FUEL INJECTOR

Description

TECHNICAL FIELD

[0001] Aspects of the present invention relate to a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine.

BACKGROUND

[0002] A prior art fuel injector 1 will be described with reference to Figure 1. The fuel injector 1 comprises an injector body 2 (sometimes referred to as a nozzle holder body), an injector nozzle 3 and an injector needle 4. The injector needle 4 is movably mounted within an injection chamber 5 formed in the injector nozzle 3. A nozzle seat 6 is formed in the injector nozzle 3 for cooperating with a needle valve 7 disposed at a distal end of the injector needle 4. The injector nozzle 3 comprises a plurality of injection apertures 8 through which fuel is injected into the combustion chamber. The injector needle 4 is displaced relative to the nozzle seat 6 to control the injection of fuel into a combustion chamber (not shown) of an internal combustion engine (not shown). The injection apertures 8 are closed when the needle valve 7 is seated in the nozzle seat 6 and open when the needle valve 7 is unseated from the nozzle seat 6. A first spring 9 is provided in a spring chamber 10 for biasing the needle valve 7 towards the nozzle seat 6 to close the injection apertures.

[0003] The fuel injector 1 further comprises a control valve 11 for controlling the injector needle 4. The control valve 11 comprises a control valve member 12 mounted in a control chamber 13. The control valve member 12 comprises a barrel 14 and a stem 15 having a reduced diameter. A conical valve 16 is formed above the stem 15 for locating in a control valve seat 17 to close the control valve 11. A sidewall 18 of the control chamber 13 forms a guide for the barrel 14. An electro-mechanical solenoid 19 is provided to actuate the control valve 11 selectively to control opening and closing of a low pressure fuel return line 20. When the solenoid 19 is energized, the conical valve 16 lifts from the control valve seat 17 and the low pressure fuel return line 20 is opened. The solenoid 19 comprises a second spring 21 operative to bias the conical valve 16 towards the control valve seat 17 to close the low pressure fuel return line 20 when the solenoid 19 is de-energized. WO02090753 and WO2013/086427 disclose relevant prior art.

[0004] A high pressure fuel supply line 22 supplies fuel from a high pressure fuel rail (not shown) to the injector nozzle 3. The control chamber 13 is in fluid communication with the fuel supply line 22 via a high pressure fuel passage 23. The injector is electrically activated to inject a certain amount of fuel into a combustion chamber. The solenoid 19 is electrically energized to open the injection apertures 8 and subsequently de-energized to close the injection apertures 8; this is referred to herein as an injection event. The quantity of fuel injected during the injection event is dependent on the rail pressure and the period of time that the injection apertures 8 are open. The operation of the fuel injector 1 will now be described in more detail.

[0005] When the solenoid 19 is energized, the conical valve 16 lifts from the control valve seat 17 and the low pressure fuel return line 20 is opened. The spring chamber 10 is placed in fluid communication with the low pressure fuel return line 20 resulting in a reduction in the fuel pressure in the spring chamber 10. The fuel pressure in the injector nozzle 3 is higher than the fuel pressure in the spring chamber 10 and a pressure force is applied to the injector needle 4 which overcomes the bias of the first spring 9. The injector needle 4 lifts from the nozzle seat 6 and opens the injection apertures 8 allowing high pressure fuel to be injected into the combustion chamber. When the solenoid 19 is de-energized, the control valve 11 is closed and fluid communication between the spring chamber 10 and the low pressure fuel return line 20 is inhibited. The fuel pressure in the injector nozzle 3 and the spring chamber 10 equalises and the first spring 9 biases the injector needle 4 to a seated position in which the injection apertures 8 are closed.

[0006] A potential shortcoming of the fuel injector 1 occurs during a multiple injection scheme comprising a plurality of injection events performed in a short period of time. Each injection event comprises the opening and closing of the injection apertures 8 which forms a pressure wave in the high pressure fuel within the fuel injector 1. The magnitude of the pressure wave varies through the fuel injector 1 and is typically higher on injector side (for example in the injector nozzle 3 proximal to the nozzle seat 6), than close to the high pressure fuel rail. These pressure waves can make accurate control of the fuel injections difficult and affect the delivery stability of the fuel injector 1, particularly in a multiple injection scheme. The resulting variations in fuel injections can adversely affect the operating efficiency of the internal combustion engine.

[0007] These problems are compounded by the need to improve system performances, with improved delivery stability under higher constraints, such as the number of injections per cycle, higher rail pressure, etc. The increase of combustion quality and efficiency is achieved by using multiple injection schemes. A multiple injection scheme comprising five (5) injection events will now be described by way of example. Without any perturbation, each injector event is expected to provide a metered delivery of fuel to the combustion chamber. The expected quantity of fuel injected during each injection event (Q1-Q5) in the multiple injection scheme is illustrated in Figure 2A (the Y-axis represents the quantity of fuel injected and the X-axis represents the energizing time). In practice, however, the pressure wave(s) generated by each injection event influence the subsequent injection event(s). The resulting interactions cause variations in the quantity of fuel injected during the subsequent injection event(s). The variations in the quantity of fuel injected during each injection event (Q1'-Q5') in the multiple injection scheme is illustrated in Figure 2B (the Y-axis represents the quantity of fuel injected and the X-axis represents the energizing time). Moreover, the extent of the variation is dependent on the dwell between the injection events.

[0008] Various hardware solutions have been proposed to reduce these pressure variations and their impact on the deliveries during multiple injection schemes. It has been proposed to provide orifices to attenuate the pressure waves, for example in the high pressure supply line. However, the provision of attenuating orifices can present different problems. In particular, the orifices in the high pressure line can decreases the global performance of the system due to higher pressure drop (which can impacts on the injection rate).

[0009] An alternative approach is to provide an enlarged volume within the injector body 2. The volume is open at both ends to provide a series connection with a high pressure supply line. The volume can reduce the amplitude of waves through volume amortization, but is not effective in promoting the decay of high frequency waves .

[0010] An alternative approach is to implement a correction strategy in the control of the solenoid 19. The correction strategy can be implemented in software, for example in an injector control unit, and can correct for some variations in the delivery. However, this requires extensive calibration which may be specific for particular applications. As a result, the implementation of the correction strategy could result in increased system costs.

[0011] It is against this backdrop that the present invention has been conceived. At least in certain embodiments, the present invention sets out to overcome or ameliorate at least some of the problems associated with known fuel injectors.

SUMMARY OF THE INVENTION

[0012] The invention relates to a diesel fuel injector according to claim 1.

[0013] According to a further aspect of the present invention there is provided a fuel injector comprising:

an injector body;

an injector nozzle having a nozzle seat and at least one injection aperture;

an injector needle having a needle valve for cooperating with the nozzle seat, the injector needle being movable within the injector nozzle to control the injection of fuel through said at least one injection aperture; and

a high pressure supply line for supplying high pressure fuel to the injector nozzle.

[0014] The fuel injector comprises a high pressure accumulator in fluid communication with the high pressure supply line. The high pressure accumulator is operative to reduce variations in the fuel pressure, for example at the nozzle seat. The high pressure accumulator can attenuate pressure waves generated during an injection event. The high pressure accumulator comprises a chamber which is in fluid communication with the high pressure supply line. In use, high pressure fuel collects in the chamber and provides a hydraulic damper which reduces the amplitude of pressure waves. In use, the high pressure supply line is connected to a high pressure supply rail arranged to receive fuel from a high pressure fuel pump. The high pressure accumulator forms part of the fuel injector and is separate from the high pressure supply rail. The high pressure supply line can be arranged to establish fluid communication between the high pressure supply rail and the high pressure accumulator. At least in certain embodiments, the high pressure accumulator can reduce the pressure drop from the high pressure supply rail to the nozzle seat and this can help to reduce energy consumption. The fuel injector can function to provide improved delivery stability which can facilitate control of the delivery of each injection in a multiple injection scheme.

[0015] The fuel injector can be controlled by an electronic controller. The electronic controller can implement a correction strategy to allow for any remaining variations in the quantity of fuel delivered during each injection event. The inclusion of the high pressure accumulator can reduce the pressure waves and may thereby facilitate implementation of the correction strategy.

[0016] The injector needle can be disposed in an injection chamber. In use, the injector needle can reciprocate within the injection chamber to control the injection of fuel. The injection chamber can be formed within the injector body. A control valve for controlling actuation of the injector needle can also be formed in the injector body.

[0017] The high pressure accumulator can be formed in the injector body. The high pressure accumulator can be in the form of a chamber formed within the injector body.

[0018] The fuel injector can comprise an accumulator line for establishing fluid communication between the high pressure accumulator and the high pressure supply line. At least a portion of the accumulator line can be formed in the injector body. The accumulator line can be a conduit formed within said injector body. The accumulator line can have an accumulator inlet in communication with the high pressure supply line. In certain embodiments, the accumulator inlet can open directly into the high pressure supply line. The high pressure supply line can comprise a supply inlet for operative connection to the high pressure fuel rail. The accumulator inlet can be disposed between the supply inlet and the nozzle seat. The accumulator inlet can be disposed proximal to the supply inlet. For example, the accumulator inlet can be disposed adjacent to the supply inlet. Alternatively, the accumulator inlet can be disposed remote from the supply inlet. The accumulator inlet can be disposed proximal to the nozzle seat. For example, the accumulator inlet can be disposed adjacent to the nozzle seat. It is believed that the effectiveness of the high pressure accumulator can be improved by locating the accumulator inlet closer to the nozzle seat.

[0019] The fuel injector can comprise means for restricting the flow of fuel through the accumulator line. The flow restricting means could be in the form of a section of the accumulator line having a reduced diameter. Indeed, the accumulator line could be sized to restrict the flow of fuel to/from the high pressure accumulator. Alternatively, the flow restricting means can be in the form of a flow restrictor (also referred to as a jet). The flow restrictor can be disposed in the accumulator line. The flow restrictor can be disposed proximal to the accumulator inlet, for example adjacent to the accumulator inlet. The flow restrictor can be disposed at the accumulator inlet. The flow restrictor can damp pressure waves in the fuel supply line. The flow restrictor can separate the high pressure accumulator from the fuel supply line. The pressure drop in the fuel supply line can, at least in certain embodiments, be reduced or avoided. Depending on the available volume inside the injector body, a ratio between this volume and the associated orifice diameter is specified to define the best hydraulic damping effectiveness.

[0020] The flow restricting means can comprise a flow restrictor in the form of an aperture, for example a circular aperture. The aperture can have a diameter in the range 0.05mm to 1mm (inclusive). More particularly, the aperture can have a diameter in the range 0.1mm to 0.7 (inclusive); or in the range 0.2mm to 0.5mm (inclusive). The aperture can, for example, have a diameter of 0.15mm, 0.25mm, 0.35mm, or 0.45mm. The flow restrictor can have a length in the range 0.1mm to 3mm; or in the range 0.1mm to 2mm.

[0021] The high pressure accumulator and the high pressure supply line can be arranged in a parallel fluid connection (rather than a series fluid connection). Thus, at least in certain embodiments, operation of the high pressure supply line is substantially unaffected by the high pressure accumulator. The accumulator line can provide the only fuel supply connection to the high pressure accumulator.

[0022] At least a portion of the accumulator line can be formed in the injector needle. At least a portion of the accumulator line can be formed within (i.e. inside) the injector needle. The accumulator line can comprise a conduit formed within the injector needle. The accumulator line can comprise a longitudinal bore formed in the injector needle. The accumulator line can comprise an accumulator inlet. The accumulator line can be open at a first end to form said accumulator inlet. The accumulator inlet can be arranged, in use, to communicate with an injection chamber in which the injector needle reciprocates. The accumulator line can comprise a transverse bore formed in the injector needle to form the accumulator inlet for communicating with the injection chamber. The transverse bore can extend substantially perpendicular to a longitudinal axis of the injector needle. The transverse bore can, for example, extend in a radial direction. The accumulator inlet can be disposed proximal to the needle valve. For example, the accumulator inlet can be disposed adjacent to the needle valve. The accumulator line can comprise a fluid connector for establishing fluid communication between the accumulator inlet and the high pressure accumulator. The fluid connector can accommodate relative movement between the needle valve and the injector body. The fluid connector can be arranged to maintain fluid communication between the accumulator inlet and the high pressure accumulator irrespective of the position of the injector needle.

[0023] The flow restricting means can be provided in the accumulator line. The flow restricting means can be disposed at or proximal to the accumulator inlet. The flow restricting means could, for example, be disposed adjacent to the accumulator inlet. The flow restricting means can be disposed in the transverse bore. Alternatively, the flow restricting means can be disposed remote from the accumulator inlet. For example, the flow restricting means can be disposed in the longitudinal bore formed in the injector needle.

[0024] The flow restricting means can be in the form of a flow restrictor. Alternatively, the flow restricting means can be defined by a section of the accumulator line, for example the transverse bore or the radial bore, having a diameter sized to restrict flow.

[0025] The high pressure accumulator can have an internal volume in the range 0.2 cubic centimetres (cc) to 5 cubic centimetres (cc) inclusive; or in the range 0.4 cubic centimetres (cc) to 4 cubic centimetres (cc) inclusive; or in the range 1 cubic centimetre (cc) to 2 cubic centimetres (cc) inclusive.

[0026] The high pressure accumulator can be connected to a vent passage for venting gas (such as air) from the high pressure accumulator. The vent passage can be formed in the injector body. The vent passage can be connected to the high pressure supply line. The vent passage can be connected to an upper portion of the high pressure accumulator. The vent passage can be configured to permit gas to vent from the high pressure accumulator whilst restricting or preventing the flow of fuel. A vent flow restrictor can be provided in the vent passage for restricting the flow of fuel through the vent passage. Alternatively, the vent passage can be sized to restrict or prevent the flow of fuel. The vent passage can have a diameter which is smaller than that of the inlet restrictor.

[0027] The fuel injector can comprise a control valve having a valve member movable between a closed position for inhibiting fluid communication between a control chamber and a fuel return line; and an open position for enabling fluid communication between the control chamber and the fuel return line.

[0028] In use, fuel can be supplied to the high pressure supply line at an operating pressure of greater than or equal to: 1000bar, 1500bar, 2000bar or 2500bar. The operating pressure of the fuel can, for example, be 1200bar.

[0029] Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which:

Figure 1 shows a prior art fuel injector;

Figures 2An and 2B illustrate a multiple injection scheme implemented on the fuel injector shown in Figure 1;

Figure 3 shows a fuel injector in accordance with a first example which is not part of the present invention;

Figure 4 illustrates the injection flow rates for a multiple injection scheme;

Figure 5 illustrates the variance between injection events for a prior art fuel injector and the fuel injector according to the first example which is not part of the present invention;

Figure 6 illustrates the variance between injection events for a prior art fuel injector and a variant of the fuel injector according to the first example which is not part of the present invention;

Figure 7 shows a fuel injector in accordance with a second example which is not part of the present invention;

Figure 8 illustrates the variance between injection events for a prior art fuel injector and the fuel injector according to the second embodiment of figure 7;

Figure 9 shows a fuel injector in accordance with an embodiment of the present invention;

Figures 10A and 10B shows a schematic representation of the connection between the upper end of the injector needle and the injector body in the embodiment shown in Figure 9; and

Figure 11 illustrates the variance between injection events for a prior art fuel injector and the fuel injector according to the embodiment of the present invention.

DETAILED DESCRIPTION

[0031] A fuel injector 101 in accordance with a first example which is not part to the present invention will now be described with reference to Figure 3. The fuel injector 101 is configured to inject diesel fuel into a combustion chamber of a compression-ignition combustion engine (not shown).

[0032] The fuel injector 101 comprises an injector body 102 (sometimes referred to as a nozzle holder body), an injector nozzle 103 and an injector needle 104. The injector needle 104 is movably mounted within an injection chamber 105 formed in the injector nozzle 103. A nozzle seat 106 is formed in the injector nozzle 103 for cooperating with a needle valve 107 disposed at a distal end of the injector needle 104. The injector nozzle 103 comprises a plurality of injection apertures 108 through which fuel is injected into a combustion chamber of an internal combustion engine (not shown). The movement of the injector needle 104 relative to the nozzle seat 106 controls the injection of fuel. In particular, the injection apertures 108 are closed when the needle valve 107 is seated in the nozzle seat 106 and open when the needle valve 107 is unseated from the nozzle seat 106. A first spring 109 is provided in a spring chamber 110 for biasing the needle valve 107 towards the nozzle seat 106 to close the injection apertures.

[0033] The fuel injector 101 further comprises a control valve 111 for controlling the injector needle 104. The control valve 111 comprises a control valve member 112 movably mounted in a control chamber 113. The control valve member 112 comprises a barrel 114 and a stem 115 having a reduced diameter. A conical valve 116 is formed above the stem 115 for locating in a control valve seat 117 to close the control valve 111. A sidewall 118 of the control chamber 113 forms a guide for the barrel 114. An electro-mechanical solenoid 119 is provided to actuate the control valve 111 selectively to control opening and closing of a low pressure fuel return line 120. When the solenoid 119 is energized, the conical valve 116 lifts from the control valve seat 117 and the low pressure fuel return line 120 is opened. The solenoid 119 comprises a second spring (not shown) operative to bias the conical valve 116 towards the control valve seat 117 to close the low pressure fuel return line 120 when the solenoid 119 is de-energized.

[0034] A high pressure supply line 122 supplies fuel from a high pressure fuel rail (not shown) to the injector nozzle 103. In use, fuel is supplied to the fuel supply line 122 at an operating pressure of 1200bar. The control chamber 113 is in fluid communication with the fuel supply line 122 via a high pressure fuel passage 123. The fuel supply line 122 is also in fluid communication with the injection chamber 105 in which the injector needle 104 reciprocates. In particular, the fuel supply line 122 opens into an annular region 124 of the injection chamber 105 which extends around the injector needle 104. The high pressure supply line 122 is connected to an outlet rail orifice (for delivering a flow rate of 3.29L/min at a pressure under 50bar) by a conduit having an internal diameter of 3mm and a length of 167mm.

[0035] A high pressure accumulator 125 is formed in the injector body 102. The high pressure accumulator 125 comprises an accumulator chamber 126. The accumulator chamber 126 is a cylindrical having a diameter of 2mm and a length of 125mm. The internal volume of the accumulator chamber 126 in the present embodiment is approximately 393mm³ (approximately 0.4 cubic centimetres (cc)). The accumulator chamber 126 is formed by a drilling a bore in the injector body 102 substantially parallel to the fuel supply line 122. The accumulator chamber 126 is in fluid communication with the fuel supply line 122 via an accumulator line 127. The accumulator line 127 has an accumulator inlet 128 which opens into the fuel supply line 122 through which high pressure fuel is introduced into the accumulator chamber 126. The accumulator line 127 provides the only inlet to the accumulator chamber 126. The high pressure accumulator 125 can be considered as being disposed in parallel to the fuel supply line 122. The fuel injector 101 comprises flow restricting means for restricting the flow of fuel into and out of the accumulator chamber 126. In the present embodiment, the flow restricting means is in the form of a flow restrictor 129 (also referred to as a jet) disposed at the accumulator inlet 128. The flow restrictor 129 in the present embodiment has a diameter of approximately 0.25mm. The fuel injector 101 provides an example of a small volume accumulator chamber 126 in combination with a flow restrictor 129 having a small diameter. A vent passage (not shown) can optionally be provided between an upper portion of the high pressure accumulator 125 and the fuel supply line 122 to allow air trapped in the high pressure accumulator 125 to vent.

[0036] The operation of the fuel injector 101 to perform an injection event will now be described. The high pressure fuel is supplied to the injection chamber 105 from the fuel supply line 122. The accumulator chamber 126 of the high pressure accumulator 125 is also supplied with high pressure fuel from the fuel supply line 122 via the accumulator line 127.

[0037] To initiate an injection event, the solenoid 119 is energized to open the control valve 111. The conical valve 116 lifts from the control valve seat 117, thereby opening the low pressure fuel return line 120. The spring chamber 110 is placed in fluid communication with the low pressure fuel return line 120 resulting in a reduction in the fuel pressure in the spring chamber 110. The fuel pressure in the injector nozzle 103 is higher than the fuel pressure in the spring chamber 110 and a pressure force is applied to the injector needle 104 which overcomes the bias of the first spring 109. The injector needle 104 lifts from the nozzle seat 106 and opens the injection apertures 108 allowing high pressure fuel to be injected into the combustion chamber. To terminate the injection event, the solenoid 119 is de-energized to close the control valve 111. The conical valve 116 is seated in the control valve seat 117 and fluid communication between the spring chamber 110 and the low pressure fuel return line 120 is inhibited. The fuel pressure in the injector nozzle 103 and the spring chamber 110 equalises and the first spring 109 biases the injector needle 104 to a seated position in which the injection apertures 108 are closed. It will be appreciated that fuel injector 101 can be controlled to perform a multiple injection scheme comprising a plurality of injection events.

[0038] The opening and closing of the injection apertures 108 serves as an excitation source which forms pressure waves (oscillations) in the fuel within the fuel injector 1. The pressure waves propagate through the fuel injector 101, for example along the fuel supply line 122, and can potentially affect the volume of fuel injected during one or more subsequent injection events. The high pressure accumulator 125 functions as a hydraulic damper for damping oscillations, thereby filtering pressure waves. The accumulator chamber 126 can be considered as forming a cavity resonator for at least partially attenuating the pressure waves. The accumulator chamber 126 is similar to a Helmholtz resonator, although the orifice length and damping frequency may differ. The flow restrictor 129 isolates the accumulator chamber 126 from the fuel supply line 122 and should be calibrated for particular applications.

[0039] By positioning the accumulator inlet 128 in the fuel supply line 122, the transmittal of the pressure waves can be inhibited. When the prior art fuel injector 1 performs a multiple injection scheme, the pressure waves influence the injection stability. The high pressure accumulator 125 has particular application to reduce pressures waves in a multiple injection scheme and to improve injection stability and accuracy. Figure 4 shows the injection flow rates (L/min) for the multiple injection scheme illustrated in Figure 2A comprising five (5) injection events (Q1-Q5) with corresponding energising times (ET1-ET5) of the solenoid 119. A first graph 130 illustrates the injection flow rates for the prior art fuel injector 1; a second graph 131 illustrates the injection flow rates for the fuel injector 101 in accordance with the present embodiment; and a third graph 132 illustrates the injection flow rates for the fuel injector 101 in conjunction with an electronic controller implementing a correction strategy. As shown in the first graph 130, the pressure waves generated during an injection event in the prior art fuel injector 1 can affect the quantity of fuel injected during one or more subsequent injection events. The high pressure accumulator 125 functions to reduce these variations, as illustrated by the second graph 131. Furthermore, by implementing a correction strategy to control operation of the fuel injector 101, the variations can be further reduced, as illustrated by the third graph 132. Any low frequency variations (which typically occur at a period of approximately 500µs) are reduced by the high pressure accumulator 125.

[0040] A fourth graph 133 is shown in Figure 5 comparing the operation of the fuel injector 101 according to the first example not part to the present invention to the operation of the prior art fuel injector 1. The fuel is supplied at an operating pressure of 1200bar. A first plot 134 represents the variance between first and second injection events in a multiple injection scheme performed by the prior art fuel injector 1. A second plot 135 represents the variance between first and second injection events in a multiple injection scheme performed by the fuel injector 101 according to the first example not part to the present invention. The high pressure accumulator 125 reduces the pressure waves and, as shown in Figure 5, the variance between the first and second injection events is reduced.

[0041] A modified version of the fuel injector 101 according to the first example which is not part of the present invention will now be described. Like reference numerals are used for like components. The dimensions of the accumulator chamber 126 are altered in the modified version of the fuel injector 101. The volume of the accumulator chamber 126 and the diameter of the flow restrictor 129 are larger than those of the fuel injector 101 according to the first example not part to the present invention. In particular, the accumulator chamber 126 is a cylindrical bore having a diameter of 4mm and a length of 165mm; the internal volume of the accumulator chamber 126 is approximately two (2) cubic centimetres (cc). The diameter of the flow restrictor 129 is approximately 0.45mm. The location of the high pressure accumulator 125 and of the accumulator inlet 128 is unchanged from the first example of the fuel injector 1. A fifth graph 136 is shown in Figure 6 to provide a comparison between the modified version of the fuel injector 101 according to the first example not part to the present invention and the prior art fuel injector 1. The fuel is supplied at an operating pressure of 1200bar. A first plot 137 represents the variance between first and second injection events in a multiple injection scheme performed by the prior art fuel injector 1. A second plot 138 represents the variance between first and second injection events in a multiple injection scheme performed by the fuel injector 101 according to the first example not part to the present invention.

[0042] A fuel injector 101 according to a second example not part to the present invention is illustrated in Figure 7. Like reference numerals are used for like components. The fuel injector 101 according to the second example is similar to the fuel injector 101 according to the first example. However, the configuration of the high pressure accumulator 125 and the location of the accumulator inlet 128 are different in this embodiment. Specifically, the accumulator inlet 128 is disposed in the injector body 102 proximal to the supply inlet for the fuel supply line 122 (i.e. proximal to the connection to the common rail). The flow restrictor 129 is disposed in the accumulator line 127 proximal to the accumulator inlet 128. The accumulator chamber 126 in the second embodiment has an internal volume of approximately two (2) cubic centimetres (cc). The diameter of the flow restrictor 129 is approximately 0.45mm. The operation of the fuel injector 101 according to the second example is unchanged from the fuel injector 101 according to the first example.

[0043] A sixth graph 139 is shown in Figure 8 comparing the operation of the fuel injector 101 according to the second example not part to the present invention to the operation of the prior art fuel injector 1. The fuel is supplied at an operating pressure of 1200bar. A first plot 140 represents the variance between first and second injection events in a multiple injection scheme performed by the prior art fuel injector 1. A second plot 141 represents the variance between first and second injection events in a multiple injection scheme performed by the fuel injector 101 according to the first example not part to the present invention. The high pressure accumulator 125 reduces the pressure waves and, as shown in Figure 8, the variance between the first and second injection events is reduced.

[0044] A fuel injector 101 according to an embodiment of the present invention is illustrated in Figure 9. The fuel injector 101 according to the embodiment is similar to the fuel injector 101 according to the first example. Like reference numerals are used for like components.

[0045] The configuration of the high pressure accumulator 125 is different in the embodiment. In particular, the accumulator line 127 is disposed in the injector needle 104. The accumulator line 127 comprises a longitudinal bore 142, a transverse bore 143, and a radial bore 144. The transverse bore 143 is formed at a distal end of the injector needle 104 to form a pair of accumulator inlets 128 proximal to the needle valve 107. The radial bore 144 is disposed at the opposite end of the injector needle 104 to the transverse bore 143 and is configured to communicate with the accumulator chamber 126. The longitudinal bore 142 extends along a central longitudinal axis of the injector needle 104 and is sealed by an insert, such as a ball plug, at an end disposed opposite to the needle valve 107 (the upper end of the injector needle 104 in the orientation shown in Figure 9).

[0046] The accumulator chamber 126 in the embodiment is disposed in the injector body 102 and has an internal volume of approximately one (1) cubic centimetre (cc). The diameter of the flow restrictor 129 is approximately 0.35mm. The flow restrictor 129 is formed in the injector needle 104 at the inlet to the accumulator line 127. In particular, the flow restrictor 129 is formed by the transverse bore 143 which is sized to restrict the flow of fuel. The radial bore 144 is positioned axially on the injector needle 104 so as to align with an inlet 145 to the accumulator chamber 126. As illustrated in Figures 10A and 10B, the inlet 145 is sized such that the radial bore 144 remains in fluid communication with the accumulator line 127 irrespective of the position of the injector needle 104. The inlet 145 can, for example, be formed by a slot machined in the injector body 102 (extending in a vertical direction in the orientation illustrated in Figure 9). The inlet 145 thereby maintains fluid communication when the injector needle 104 is in a lowered position such that the needle valve 107 is seated in the nozzle seat 106 (as illustrated in Figure 10A) and also when the injector needle 104 is in a raised position such that the needle valve 107 is unseated from the nozzle seat 106 (as illustrated in Figure 10B). Thus, the radial bore 144 and the inlet 145 form a fluid connector for maintaining fluid communication between the accumulator inlets 128 and the accumulator chamber 126. A seal is formed between the injector needle 104 and the injector body 102 to seal the accumulator chamber 126. The operation of the fuel injector 101 according to the embodiment is unchanged from the fuel injector 101 according to the first example.

[0047] A seventh graph 145 is shown in Figure 11 comparing the operation of the fuel injector 101 according to the embodiment of the present invention to the operation of the prior art fuel injector 1. The fuel is supplied at an operating pressure of 1200bar. A first plot 146 represents the variance between first and second injection events in a multiple injection scheme performed by the prior art fuel injector 1. A second plot 147 represents the variance between first and second injection events in a multiple injection scheme performed by the fuel injector 101 according to the first example not part to the present invention. The high pressure accumulator 125 reduces the pressure waves and, as shown in Figure 10, the variance between the first and second injection events is reduced.

[0048] The fuel injector 101 has been described with reference to an operating pressure of 1200bar by way of example. It will be appreciated that the fuel injector 101 is not limited in this respect. The operating pressure of the fuel injector 101 can be higher or lower than 1200bar.

[0049] It will be appreciated that various changes and modifications can be made to the fuel injector 101 described herein without departing from the scope of the present invention as defined by the claims. For example, the high pressure accumulator 125 has been described as comprising an accumulator chamber 126 formed by a cylindrical bore in the injector body 102. However, the accumulator chamber 126 does not have to have a cylindrical section. Furthermore, the accumulator inlet 128 could be disposed in the injector nozzle 103.

[0050] Furthermore, more than one accumulator line 127 could be provided to establish communication between the high pressure accumulator 125 and the fuel supply line 122. Each accumulator line 127 could have a separate flow restrictor 129, for example disposed at or proximal to the associated accumulator inlet 128.

Claims

1. A diesel fuel injector (101) comprising:

an injector body (102);

an injector nozzle (103) having a nozzle seat (106) and at least one injection aperture (108);

an injector needle (104) having a needle valve (107) for cooperating with the nozzle seat (106), the injector needle (104) being movable within the injector nozzle (103) to control the injection of fuel through said at least one injection aperture (108); and

a high pressure supply line (122) for supplying high pressure fuel to the injector nozzle (103);

characterised in that the fuel injector (101) further comprises a high pressure accumulator (125) in fluid communication with the high pressure supply line (122),

the fuel injector (101) further comprising an accumulator line (127) for establishing fluid communication between the high pressure accumulator (125) and the high pressure supply line (122); and means for restricting flow through the accumulator line (127) and, wherein at least a portion of the accumulator line (127) is formed in the injector needle (104), said accumulator line (127) comprising a longitudinal bore (142), a transverse bore (143), and a radial bore (144), the transverse bore (143) being formed at a distal end of the injector needle (104) proximal to the needle valve (107), the radial bore (144) being disposed at the opposite end of the injector needle (104) to the transverse bore (143) and being configured to communicate with an accumulator chamber (126) disposed in the injector body (102).

2. A fuel injector (101) as claimed in claim 1, wherein the flow restricting means is in the form of a flow restrictor (129).

3. A fuel injector (101) as claimed in claim 2, wherein the accumulator line (127) comprises an accumulator inlet (128); the flow restrictor (129) being disposed at or proximal to said accumulator inlet (128).

4. A fuel injector (101) as claimed in claim 3, wherein the accumulator inlet (128) opens into the high pressure supply line (122).

5. A fuel injector (101) as claimed in claim 3 or claim 4, wherein the accumulator inlet (128) is disposed proximal to a supply inlet of the high pressure supply line (122).

6. A fuel injector (101) as claimed in claim 1, wherein the accumulator line (127) comprises an accumulator inlet (128) formed in the injector needle (104), the accumulator inlet (128) being disposed proximal to the needle valve (107).

7. A fuel injector (101) as claimed in claim 6, wherein the flow restricting means is disposed at or proximal to the accumulator inlet (128).

8. A fuel injector (101) as claimed in claim 6 or claim 7, wherein the accumulator inlet (128) is formed by a transverse bore (143) formed in the injector needle (104).

9. A fuel injector (101) as claimed in any one of the preceding claims, wherein the accumulator line (127) comprises a radial bore (144) formed in the injector needle (104) for communicating with the high pressure accumulator (125).

Ansprüche

1. Dieselkraftstoffinjektor (101), der aufweist:

einen Injektorkörper (102);

eine Injektordüse (103) mit einem Düsensitz (106) und zumindest einer Einspritzöffnung (108);

eine Injektornadel (104) mit einem Nadelventil (107) zum Zusammenwirken mit dem Düsensitz (106), wobei die Injektornadel (104) innerhalb der Injektordüse (103) bewegbar ist, um die Einspritzung von Kraftstoff durch die zumindest eine Einspritzöffnung (108) zu steuern; und

eine Hochdruckzufuhrleitung (122) zum Liefern von Hochdruckkraftstoff an die Injektordüse (103);

dadurch gekennzeichnet, dass der Kraftstoffinjektor (101) weiter einen Hochdruckspeicher (125) in Fluidverbindung mit der Hochdruckzufuhrleitung (122) aufweist,

der Kraftstoffinjektor (101) weiter eine Speicherleitung (127) aufweist zum Herstellen einer Fluidverbindung zwischen dem Hochdruckspeicher (125) und der Hochdruckzufuhrleitung (122); und Mittel zum Begrenzen eines Stromes durch die Speicherleitung (127), und wobei zumindest ein Teil der Speicherleitung (127) in der Injektornadel (104) ausgebildet ist, wobei die Speicherleitung (127) eine Längsbohrung (142), eine Querbohrung (143) und eine radiale Bohrung (144) aufweist, wobei die Querbohrung (143) an einem distalen Ende der Injektornadel (104) nah an dem Nadelventil (107) gebildet ist, wobei die radiale Bohrung (144) an dem entgegengesetzten Ende der Injektornadel (104) zu der Querbohrung (143) angeordnet ist und konfiguriert ist zum Kommunizieren mit einer Speicherkammer (126), die in dem Injektorkörper (102) angeordnet ist.

2. Kraftstoffinjektor (101) gemäß Anspruch 1, wobei das Strömungsbegrenzungsmittel in der Form eines Strömungsbegrenzers (129) ist.

3. Kraftstoffinjektor (101) gemäß Anspruch 2, wobei die Speicherleitung (127) einen Speichereinlass (128) aufweist; wobei der Strömungsbegrenzer (129) an oder nahe dem Speichereinlass (128) angeordnet ist.

4. Kraftstoffinjektor (101) gemäß Anspruch 3, wobei der Speichereinlass (128) in die Hochdruckzufuhrleitung (122) mündet.

5. Kraftstoffinjektor (101) gemäß Anspruch 3 oder Anspruch 4, wobei der Speichereinlass (128) nahe eines Zufuhreinlasses der Hochdruckzufuhrleitung (122) angeordnet ist.

6. Kraftstoffinjektor (101) gemäß Anspruch 1, wobei die Speicherleitung (127) einen Speichereinlass (128) aufweist, der in der Injektornadel (104) gebildet ist, wobei der Speichereinlass (128) nahe dem Nadelventil (107) angeordnet ist.

7. Kraftstoffinjektor (101) gemäß Anspruch 6, wobei das Strömungsbegrenzungsmittel an oder nahe dem Speichereinlass (128) angeordnet ist.

8. Kraftstoffinjektor (101) gemäß Anspruch 6 oder Anspruch 7, wobei der Speichereinlass (128) durch eine Querbohrung (143) gebildet ist, die in der Injektornadel (104) gebildet ist.

9. Kraftstoffinjektor (101) gemäß einem der vorhergehenden Ansprüche, wobei die Speicherleitung (127) eine radiale Bohrung (144), die in der Injektornadel (104) gebildet ist, zum Kommunizieren mit dem Hochdruckspeicher (125) aufweist.

Revendications

1. Injecteur de carburant diesel (101) comprenant :

un corps d'injecteur (102) ;

une buse d'injecteur (103) ayant un siège de buse (106) et au moins une ouverture d'injection (108) ;

un pointeau d'injecteur (104) ayant une valve à pointeau (107) pour coopérer avec le siège de buse (106), le pointeau d'injecteur (104) étant déplaçable à l'intérieur de la buse d'injecteur (103) pour commander l'injection de carburant à travers ladite au moins une ouverture d'injection (108) ; et

une conduite d'alimentation à haute pression (122) pour alimenter du carburant sous haute pression à la buse d'injecteur (103) ;

caractérisé en ce que l'injecteur de carburant (101) comprend en outre un accumulateur à haute pression (125) en communication fluidique avec la conduite d'alimentation à haute pression (122),

l'injecteur de carburant (101) comprenant en outre une conduite d'accumulateur (127) pour établir une communication fluidique entre l'accumulateur à haute pression (125) et la conduite d'alimentation à haute pression (122) ; et un moyen pour restreindre l'écoulement à travers la conduite d'accumulateur (127) et dans lequel au moins une portion de la conduite d'accumulateur (127) est formée dans le pointeau d'injecteur (104), ladite conduite d'accumulateur (127) comprenant un perçage longitudinal (142), un perçage transversal (143), et un perçage radial (144), le perçage transversal (143) étant formé à une extrémité distale du pointeau d'injecteur (104) à proximité de la valve à pointeau (107), le perçage radial (144) étant disposé à l'extrémité opposée du pointeau d'injecteur (104) par rapport au perçage transversal (143) et étant configuré pour communiquer avec une chambre d'accumulateur (126) disposée dans le corps d'injecteur (102).

2. Injecteur de carburant (101) selon la revendication 1, dans lequel le moyen de restriction d'écoulement à la forme d'une restriction d'écoulement (129).

3. Injecteur de carburant (101) selon la revendication 2, dans lequel la conduite d'accumulateur (127) comprend une entrée d'accumulateur (128) ; la restriction d'écoulement (129) étant disposée au niveau de ou à proximité de ladite entrée d'accumulateur (128).

4. Injecteur de carburant (101) selon la revendication 3, dans lequel l'entrée d'accumulateur (128) s'ouvre dans la conduite d'alimentation à haute pression (122).

5. Injecteur de carburant (101) selon la revendication 3 ou 4, dans lequel l'entrée d'accumulateur (128) est disposée à proximité d'une entrée d'alimentation de la conduite d'alimentation à haute pression (122).

6. Injecteur de carburant (101) selon la revendication 1, dans lequel la conduite d'accumulateur (127) comprend une entrée d'accumulateur (128) formée dans le pointeau d'injecteur (104), l'entrée d'accumulateur (128) étant disposée à proximité de la valve à pointeau (107).

7. Injecteur de carburant (101) selon la revendication 6, dans lequel le moyen de restriction d'écoulement est disposé au niveau de ou à proximité de l'entrée d'accumulateur (128).

8. Injecteur de carburant (101) selon la revendication 6 ou 7, dans lequel l'entrée d'accumulateur (128) est formée par un perçage transversal (143) formé dans le pointeau d'injecteur (104).

9. Injecteur de carburant (101) selon l'une quelconque des revendications précédentes, dans lequel la conduite d'accumulateur (127) comprend un perçage radial (144) formé dans le pointeau d'injecteur (104) pour communiquer avec l'accumulateur à haute pression (125).

Drawing