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(11) | EP 1 227 242 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Fuel-feed pump |
| (57) In order to provide a fluid pump where the discharge amount is stable even when there
are pressure fluctuations on the side of an intake line 70, there is provided a forco-feeding
pump 90 for taking in fuel from the intake line 70 and discharging fuel towards a
discharge line 80, and an opening and closing valve 100 located in such a manner as
to provide urging in a direction closing a path of the intake line 70, and opening
the path of the discharge line 80 when the pressure of fuel discharged towards the
discharge line 80 exceeds a prescribed pressure. At a piston 110 of the opening and
closing valve 100, the pressure of fuel within the intake line 70 acts in opposition
to the pressure of the discharged fuel. |
[0001] The present invention relates to a fluid pump for force feeding fluid, and particularly relates to a fluid pump suited to fluid supply systems where pressure fluctuations occur on a fluid intake line side.
[0002] Mechanical pumps where a diaphragm is made to move in a reciprocal manner, or roller vane pumps, circumferential flow-type pumps, or solenoid pumps etc. where electromagnetic force causes a plunger to perform a pumping action are wellknown as related fluid (force-feeding) pumps for force-feeding heater fuel, engine fuel or other fluids.
[0003] With vehicles mounted with diesel engines, that shown in FIG. 7 is well known as a fuel supply system for supplying fuel to an engine, and as a fuel supply system for supplying fuel to booster heaters for application in heaters such as hot air and hot water heaters. This fuel supply system comprises a fuel supply path for enabling fuel to pass from a fuel tank 1 filled with light oil to a fuel combustion chamber of an engine 4 via a fuel pump 2 for force-feeding fuel for engine use and an injection pump 3, and a fuel supply path for enabling fuel to pass to a booster heater 6 via a fuel pump 5 constituting a fluid pump for pressure-feeding fuel for the heater from the fuel tank 1.
[0004] Namely, the discharge side of the fuel pump 5 is directly connected to an intake line 7 passing from the fuel tank 1 and the discharge side of the fuel pump 5 is connected to a discharge line 8 communicating with the booster heater 6.
[0005] The fuel pump 5 can therefore discharge a desired amount of fuel without being subjected to the influence of the fuel pump 2 or the injection pump 3.
[0006] In the above fuel supply system, as shown by the two-dotted and dashed line in FIG. 7, in order to attain simplification of the piping system and commonaly, etc., a fuel supply system is considered where an intake line 7' is connected to the downstream side of the fuel pump 2, with this intake line 7' being connected to the intake side of the fuel pump 5 so as to supply fuel to the booster heater 6.
[0007] However, pressure fluctuations occur within the intake line 7' with this kind of fuel supply system due to the operating characteristics of the fuel pump 2 or the injection pump 3. This causes the amount of fuel discharged from the fuel pump 5 to vary due to the influence of these pressure fluctuations. A fixed amount of fuel is therefore not supplied to the booster heater 6 as required and the heater characteristics are therefore unstable.
[0008] In order to resolve the aforementioned problems, it is the object of the present invention to provide a fluid pump which is both small and simple and which is capable of force-feeding a prescribed amount of fluid such as fuel etc. without being influenced by pressure fluctuations within an intake line occurring on an upstream side.
[0009] A fluid pump of the present invention comprises a forcefeeding pump for taking in fluid from an intake line and discharging fluid at a desired pressure towards a discharge line; and an opening and closing valve arranged in such a manner as to urge in a direction closing a path of the discharge line, and open a path of the discharge line when pressure of fluid discharged in the direction of the discharge line exceeds a prescribed pressure. Pressure of fluid within the intake line acts in a direction opposing the pressure of the discharge fluid at the opening and closing valve.
[0010] According to this configuration, fluid taken in from the intake line is raised in pressure to a desired pressure by the force-feeding pump and discharged towards the discharge line. The opening and closing valve then opens the path when the pressure of the discharged fluid exceeds a prescribed pressure and the fluid is supplied to the downstream side.
[0011] During this time, the pressure of the fluid within the intake line acts in a direction that closes the path. Therefore, even if the pressure within the intake line fluctuates, such pressure fluctuations act in both the opening and closing direction of the opening and closing valve and therefore cancel each other out. The opening and closing valve therefore opens due to a prescribed discharge pressure without being influenced by pressure fluctuations in the intake line and the amount of fluid discharged is therefore stable.
[0012] In the above, a configuration is adopted where the intake line communicates with a downstream side of the fuel pump for force-feeding engine fuel.
[0013] According to this configuration, the fluid pump can therefore supply a stable amount of discharged fuel to the desired subject (for example, a booster heater) without being subjected to the influence of pressure fluctuations occurring on the downstream side of the fuel pump for force-feeding engine fuel.
[0014] In the above configuration, a structure is adopted where the opening and closing valve has a freely reciprocating piston formed in such a manner that pressure of the discharge fluid acts at one end thereof, and spring urging force and pressure of the fluid within the intake line acts on the other end thereof.
[0015] According to this configuration, pressure of the discharged quid acts on one end of the piston, while pressure of the fluid within the intake line and an urging force of a spring act on the other end. During this time, pressure fluctuations within the intake line act on both sides of the piston and therefore cancel each other out. The piston can therefore open and close the path using just the relationship between the urging force of the spring set in advance and the discharge force of the fluid.
[0016] In the above, a configuration is adopted where the opening and closirg valve has a diaphragm for opening and closing the path of the discharge line, formed in such a manner that pressure of the discharge fluid acts at a surface on one side, and urging force of the spring and pressure of fluid within the intake line act on asurface on the other side.
[0017] According to this configuration, pressure of the discharged fluid acts on a surface at one side of the diaphragm, while pressure of the fluid within the intake line and an urging force of a spring act on the surface on the other side. During this time, pressure fluctuations within the intake line act on surfaces on both sides of the diaphragm and therefore cancel each other out. The diaphragm can therefore open and close the path using just the relationship between the urging force of the spring set in advance and the discharge force of the fluid. In particular, the discharge line side and the intake line side are completely separated by the diaphragm. This means that leaks (seepage) between the sides can be completely preventedand a more stable discharge amount can be ensured.
[0018] In the configuration adopted above, the opening and closing valve has bellows formed in such a manner as to freely expand and contract, and a seal for opening and closing the path of the discharge line, formed at an end of the bellows in such a manner that pressure of the discharge fluid acts at a surface on one side, and urging force of the spring and pressure of fluid within the intake line act on a surface on the other side.
[0019] According to this configuration, pressure of the discharged fluid acts on a surface at one side of the diaphragm, while pressure of the fluid within the intake line and an urging force of a spring act on the surface on the other side. During this time, pressure fluctuations within the intake line act on surfaces on both sides of the seal having the same bearing area and therefore cancel each other out. The bellows therefore compress and expand using just the relationship between the urging force of the spring set in advance and the discharge force of the fluid so as to open and close the path. In particular, the intake line side and the discharge line side are completely separated by the bellows and the seal. Leaking (seepage) between the two sides is therefore completely prevented, it is straightforward to make the pressure bearing area for the discharge side and the intake side at the seal the same, and a more stable discharge amount can therefore be ensured.
[0021] FIG. 2 is a view illustrating the theory of operation of an opening and closing valve constituting part of the fluid pump, where FIG. 2(a) shows the state of the opening and closing valve when the force-feeding pump is not operating, and where FIG. 2(b) shows the state of the opening and closing valve when the force-feeding pump is operating.
[0022] FIG. 3 is a cross-sectional view showing a force-feeding pump constituting part of a fluid pump.
[0024] FIG. 5 is an outline system view showing a further embodiment of a fluid pump of the present invention.
[0025] FIG. 6 is an outline system view showing a still further embodiment of a fluid pump of the present invention.
[0027] The following is a description with reference to the appended drawings of embodiments of the present invention.
[0028] FIG. 1 to FIG. 3 show a first embodiment of the fluid pump of the present invention, with FIG. 1 being a system view, FIG. 2 being a view illustrating operation, and FIG. 3 being a cross-sectional view of a force-feeding pump.
[0029] The fluid pump used in this embodiment is that used in supplying fuel to a booster heater of a vehicle mounted with a diesel engine. As shown in FIG. 1, the fuel supply system of the present invention comprises an engine side supply path for supplying fuel from a fuel tank 10 filled with light fuel to a combustion chamber of an engine 40 via a fuel pump 20 and an injection pump 30, and a heater side supply path on the downstream side of the fuel pump 20 and branching from the upstream side of the injection pump 30, for supplying fuel to a booster heater 60 via a fluid pump 50.
[0030] The fluid pump 50 is comprised of a solenoid pump 90 constituting a pressure-feed pump and an opening and closing valve 100 for opening and closing a path of the discharge line 80. The upstream side (intake side) of the solenoid pump 90 is connected to an intake line 70 branching from the downstream side of the fuel pump 20 and the downstream side (discharge side) of the solenoid pump 90 is connected to a discharge line 80 communicating with the booster heater 60. One end of the opening and closing valve 100 is connected midway along the discharge line 80 (between an upstream discharge line 81 and a downstream discharge line 82), and the other end is connected to the intake line 70.
[0031] Namely, as shown in FIG. 1 and FIG. 2, the opening and closing valve 100 is formed from a piston 100 constituting a valve body located so as to move in a freely reciprocating manner within a cylinder bore 101, a spring 120 for urging the piston 110 in a direction closing (blocking between the upstream discharge line 81 and the downstream discharge line 82) the path of the discharge line 80, and a communicating path 130 formed at a side surface of the cylinder bore 101 and communicating with the downstream discharge line 82.
[0032] One end of the cylinder bore 101 communicates with the upstream discharge line 81 and the other end of the cylinder bore 101 communicates with the intake line 70.
[0033] The pressure of fuel (discharged fluid) discharged from the solenoid pump (force-feeding pump) 90 through the upstream discharge line 81 acts on an end surface 111 at one end of the piston 110 and pressure of the fuel (fluid) within the intake line 70 and the urging force of the spring 120 act on another end surface 112 of the piston 110 (pressure of the fuel within the intake line 70 acts in a direction opposed to the pressure of the discharge fuel). The piston 110 therefore stays at a position where the forces acting from both sides are balanced.
[0034] Describing the operation of the opening and closing valve 100, as shown in FIG. 2(a), when the solenoid pump (force-feeding pump) 90 is not operating or when the pressure of fuel discharged from the solenoid pump (force-feeding pump) 90 is less than a prescribed level, the piston 110 is moved in a closing direction by urging force of the spring 120 and the discharge line 80 is closed.
[0035] On the other hand, taking head pressure of the solenoid pump (force-feeding pump) 90 to be P and the pressure of fuel within the intake line 70 to be Ps, when the solenoid pump (force-feeding pump 90) is operating and the pressure of discharged fuel is a prescribed pressure (P + Ps) or more, the piston 110 moves so as to resist the urging force of the spring 120 and the communicating path 130 of the discharge line 80 is opened. At this time, as shown in FIG. 2(b), a pressure P + Ps of the discharged fuel acts on one end surface 111 of the piston 110 and the pressure Ps of the fuel within the intake line 70 and the urging force of the spring 120 act on the surface 112 at the other end of the piston 110.
[0036] The pressure Ps of the fuel within the intake lire 70 acts from both sides of the piston 110 and is therefore canceled out. This means that only the pressure P and the urging force of the spring 120 act on the piston 110. The piston 110 therefore moves to a position set in advance due to the balance of the pressure P and the urging force, and a prescribed amount of fuel is discharged towards the downstream discharge line 82.
[0037] When a pressure fluctuation ΔP occurs in fuel within the intake line 70, a pressure P + (Ps + ΔP) of fuel discharged to within the upstream discharge line 81 acts on one end surface 111 of the piston 110 and a pressure (Ps + ΔP ) of fuel within the intake line 70 acts on the other end surface 112 of the piston 110. Therefore, as with the above, pressure ( + ΔP) of fuel within the intake line 70 therefore cancels itself out.
[0038] The solenoid pump (force-feeding pump) 90 therefore provides a stably discharged amount of fuel without being influenced by pressure fluctuations of fuel within the intake line 70. The fluid pump 50 can thereforebe made small and have a simple structure as a result of constructing the opening and closing valve 100 from a piston 110 sliding within the cylinder bore 101 and a spring 120.
[0039] The solenoid pump 90 constituting the force-feeding pump is a pump of a know configuration. As shown in FIG. 3, the solenoid pump 90 comprises an intake side pipe 90a, an outer yoke 90b, and end yoke 90c, an electromagnetic coil 90d, a discharge-side pipe 90e, a sleeve 90f, a plunger 91 inserted in a freely slidable manner within the sleeve 90f, a coil spring 92 urging the plunger 91 towards the upstream side, an intake valve 93 for opening an closing a path 91a within the plunger 91, a coil spring 94 for urging the intake valve 93 in a closing direction, a discharge valve 95, and a coil spring 96 for urging the discharge valve 95 in a closing direction, etc.
[0040] When the electromagnetic coil 90d is energized, the plunger 91 moves to the downstream side, and fuel compressed by this movement acts against the urging force of the coil spring 96 so as to open the discharge valve 95, so that the fuel is supplied to the discharge line 80 via the discharge side pipe 90e. On the other hand, when excitation of the electromagnetic coil 90d erases, the discharge valve 95 closes the path due to the urging force of the coil spring 96 and the plunger 91 moves towards the upstream side due to the urging force of the coil spring 92. At this time, at the border of the intake valve 93, the downstream side pressure is lower than the upstream pressure. The intake valve 93 therefore opens in opposition to the urging force of the coil spring 94 and fuel is taken in in a downstream direction. This sequence of operations therefore enables a prescribed amount of fuel to be discharged.
[0041] FIG. 4 is a graph showing discharge characteristics when the pressure of fuel within the intake line 70 changes. FIG. 4 shows a related characteristic for the discharge characteristics when only the related solenoid pump (forcefeeding pump) 90 is connected by the intake line 7' shownby the two-dotted and dashed line in FIG. 7 and characteristics for the present invention for discharge characteristics for the fluid pump 50 of the present invention with the opening and closing valve 100 added to the solenoid pump 90. In the characteristics of the present invention, there are shown discharge characteristics for when the clearance (spacing) between the piston 110 of the opening and closing valve 100 and the cylinder bore 101 differs, i.e. graphs are shown for a large clearance (for example, approximately 15µm) and for a small clearance (for example, approximately 5µm).
[0042] As is clear from the results, according to the fluid pump 50 of the present invention, the amount of discharge is substantially fixed even if pressure within the intake line 70 fluctuates.
[0043] FIG. 5 is a view showing a further embodiment of a fluid pump of the present invention. A fluid pump 50' of this embodiment comprises the solenoid pump 90 constituting the force-feeding pump and a diaphragm-type opening and closing valve 200.
[0044] As shown in FIG. 5, the opening and closing valve 200 comprises a diaphragm 210 dividing up a discharge side space and an intake side space, and a spring 220 urging the diaphragm 210 towards the discharge side space. An upstream discharge line 81 and a downstream discharge line 82 are connected to the discharge side space and a seal 211 formed above the diaphragm 210 opens and closes an opening 81a of . the upstream discharge line 81. On the other hand, the spring 220 is located at the intake side space and the intake line 70 is also connected to the intake side space.
[0045] The pressure of fuel (discharged fluid) discharged from the solenoid pump 90 acts upon one side surface of the diaphragm 210, and the urging force of the spring 220 and the pressure of fuel within the intake line 70 act on the other side surface of the diaphragm 210 (the pressure of fuel within the intake line 70 acts in a direction resisting the pressure of the discharged fuel). The seal 211 then opens and closes the path of the discharge line 80 according to the relationship of the force acting from both sides.
[0046] With the fluid pump 50' having the opening and closing valve 200 of the above configuration, as with the fluid pump 50, when a pressure fluctuation ΔP occurs in the fuel within the intake line 70, pressure P + (Ps + ΔP) of the fuel discharged within the upstream discharge line 81 acts on one side surface of the diaphragm 210 and pressure (Ps + ΔP) of the fuel within the intake line 70 acts on the other side surface of the diaphragm 210. The pressure (P + ΔP) of the fuel within the intake line 70 can therefore be canceled out by regulating in response to differences in the bearing surface area.
[0047] The solenoid pump (force-feeding pump) 90 therefore provides a stably discharged amount of fuel without being influenced by pressure fluctuations of fuel within the intake line 70. In particular, the discharge side spaceand the intake side space are completely separated by the diaphragm 210. There is therefore no leakage (seeping) between the sides and a more stable discharge characteristic can be obtained.
[0048] FIG. 6 is a view showing a still further embodiment of a fluidpump of the present invention. A fluid pump 50" of this embodiment comprises the solenoid pump 90 constituting the force-feeding pump and a bellows-type opening and closing valve 300.
[0049] As shown in FIG. 6, the opening and closing valve 300 comprises bellow 310 dividing up a discharge side space and an intake side space and freely expanding and contracting in one direction, and a spring 320 urging the bellows 310 towards the discharge side space. An upstream discharge line 81 and a downstream discharge line 82 are connected to the discharge side space and a seal 311 formed at an upper end of the bellows 310 opens and closes an opening region of the upstream discharge line 81. On the other hand, the spring 320 is located at the intake side space and the intake line 70 is connected to the intake side space.
[0050] The pressure of fuel (discharged fluid) discharged from the solenoid pump 90 acts upon the upper surface of the seal 311 positioned at the upper end of the bellows 310 and the urging force of the spring 320 and the pressure of fuel within the intake line 70 acts on the lower side surface of the bellows 310 (the pressure of fuel within the intake line 70 acts in a direction resisting the pressure of the discharged fuel). The seal 311 then opens and closes the path of the discharge line 80 according to the relationship of the force acting from both sides.
[0051] With the fluid pump 50" having the opening and closing valve 300 of the above configuration, as with the aforementioned fluid pumps 50 and 50', when a pressure fluctuation ΔP occurs in the fuel within the intake line 70, pressure P + (Ps + ΔP) of the fuel discharged within the upstream discharge line 81 acts on one side surface (the upper surface) of the seal 311 and pressure (Ps + ΔP) of the fuel within the intake line 70 acts on the other side surface (the lower surface) of the seal 311. With this configuration, the bearing surface area of the intake side and the discharge side of the seal 311 is the same. The pressure (P + ΔP) of the fuel within the intake line 70 is therefore negated at the boundary of the seal 311.
[0052] The solenoid pump (force-feeding pump) 90 therefore provides a stably discharged amount of fuel without being influenced by pressure fluctuations of fuel within the intake line 70. In particular, the discharge side space and the intake side space are completely separated by the bellows 310 and the seal 311. There is therefore no leakage (seeping) between the sides and a more stable discharge characteristic can be obtained.
[0053] In the above embodiments, a plunger-type solenoid pump 90 taken as a force-feeding pump making up part of the fluid pumps 50, 50' and 50" is shown but the present invention is by no means limited in this respect and other related mechanical or electrical fluid pumps (force-feeding pumps) are also applicable.
[0054] In the above embodiments, a fuel supply system for supplying fuel to a booster heater 60 is shown as a fluid supplying system to which the fluid pumps 50, 50' and 50" are applied but the present invention is by no meanslimited in this respect, and providing the fuel system does not incur the influence of pressure fluctuations etc. in the intake line etc., the fluid is not limited to light oil and application to supply systems for supplying fluid constituted by gasoline taken as a fuel, oil taken as a working medium, or water, steam or gas (vapor) etc. is also possible.
[0055] Further, items formed separately from the solenoid pump (force-feeding pump) 90 are formed as the intake line 70 and the discharge line 80 connecting tothe fluid pumps 50, 50' and 50", but the present invention is by no means limited in this respect. For example, paths corresponding to the intake line and the discharge line may be formed integrally with the solenoid pump (force-feeding pump) 90 so that the present invention may also include fluid pumps where the opening and closing valves 100, 200 and 300 are provided integrally with the solenoid pump (force-feeding pump) 90.
[0056] According to the fluid pump of the present invention, there is provided a force-feeding pump for taking in fluid from an intake line and discharging fluid at a desired pressure towards a discharge line, and an opening and closing valve arranged in such a manner as to urge in a direction closing a path of the discharge line, and open a path of the discharge line when pressure of fluid discharged in the direction of the discharge line exceeds a prescribed pressure. By ensuring that the pressure of fluid within the intake line acts in opposition to pressure of the discharged fluid with respect to an opening and closing valve, fluid can be supplied at the desired stable amount with the influence of fluctuations in pressure not being incurred or being suppressed even for fluid supply systems where pressure fluctuations occur on the intakeline side. In particular, in the case of application to a system for supplying fuel to a heater where a path diverging from midway along a system for supplying fuel to an engine mounted on a vehicle is taken as an intake line, fuel can be supplied to a heater in a stable manner without the influence of pressure fluctuations due to vibrations etc. in the fuel supply system being incurred.
[0057] Further, by forming an opening and closing valve constituting the fluid pump from a piston and spring, etc., a device can be made smaller and can be simplified, and by forming the opening and closing valve from a diaphragm or bellows etc., leakage between the discharge side and the intake side is prevented, and a more stable discharge characteristic can be obtained.
1. A fluid pump comprising: a forcefeeding pump for taking in fluid from an intake line
and discharging fluid at a desired pressure towards a discharge line; and an opening
and closing valve arranged in such a manner as to urge in a direction closing a path
of the discharge line, and open a path of the discharge line when pressure of fluid
discharged in the direction of the discharge line exceeds a prescribed pressure; wherein
pressure of fluid within the intake line acts in a direction opposing the pressure
of the discharge fluid at the opening and closing valve.
2. The fluid pump of claim 1, wherein the intake line communicates with a downstream
side of a fuel pump for force-feeding fuel to the engine.
3. The fluid pump of claim 1 or claim 2, whereinthe opening and closing valve has a freely
reciprocating piston formed in such a manner that pressure of the discharge fluid
acts at one end thereof, and spring urging force and pressure of the fluid within
the intake line act on the other end thereof.
4. The fluid pump of claim 1 or claim 2, wherein the opening and closing valve has a
diaphragm for opening and closing the path of the discharge line, formed in such a
manner that pressure of the discharge fluid acts at a surface on one side, and urging
force of the spring and pressure of fluid within the intake line act on a surface
on the other side.
5. The fluid pump of claim 1 or claim 2, wherein the opening and closing valve has bellows
formed in such a manner as to freely expand and contract, and a seal for opening and
closing the path of the discharge line, formed at an end of the bellows in such a
manner that pressure of the discharge fluid acts at a surface on one side, and urging
force of the spring and pressure of fluid within the intake line acton a surface on
the other side.