Fuel injection pump

Abstract

 In a fuel injection pump (1), in which communication between an inflow / outflow port (16) of a rotor (3) and a fuel chamber (6) is opened / closed with an electromagnetic valve and fuel is induced to an operating chamber (10) through a passage at the rotor (3), the dead volume is reduced and noise is also reduced.
An electromagnetic valve (26) is housed inside the pump housing members (2a, 2b, 2c) and a plug (27) of the electromagnetic valve (26) is placed at a side of the rotor (3) so that it slides at a right angle to the direction of the axis of the rotor (3). The proximate portions of the plug (27) and the rotor (3) are made to communicate with each other at a connecting hole (20) that constitutes a portion of a communicating passage whereby an inflow / outflow port (16) and the fuel chamber (6) communicate with each other, with the electromagnetic valve (26) being provided with a valve seat (31), which seats the plug (27) in the vicinity of the connecting hole (20). The distance between the valve seat (31) and the operating chamber (10) can be reduced and by enclosing the electromagnetic valve (26) with the housing members (2a, 2b and 2c), less of the operating noise of the electromagnetic valve (26) is communicated to the outside.

Description

[0001] The present invention relates to a fuel injection pump that is used for fuel supply to an engine or the like, i.e., to a fuel injection pump used, for instance, as a fuel injection pump or the like employing an inner cam system which controls the injection start timing and the injection end timing of fuel by opening and closing the communication between a fuel chamber and an inflow / outflow port of a rotor with an electromagnetic valve. More specifically, the present invention relates to a fuel injection pump in which the plug of the electromagnetic valve is provided in a direction that is different from the direction in which the rotor extends.

[0002] Fuel injection pumps of this type in the known art include, for instance, the one disclosed in Japanese Unexamined Patent Publication No. S60-228733 and the one disclosed in Japanese Unexamined Patent Publication No. S58-133468.

[0003] Of these, in the former fuel injection pump, an electromagnetic valve is mounted at a housing with its plug provided extending in a direction running at a right angle to the direction of the axis of the rotor (rotary distributor), and the solenoid portion of the electromagnetic valve is structured to be exposed from the housing surface. In the electromagnetic valve, the plug which is pulled by the solenoid portion is provided in such a manner that it can come in contact with a valve seat 13, with a fuel intake 19 provided at a side surface of the valve seat 13 so that fuel that is made to flow in through this fuel intake 19 travels through a circular chamber 20 formed around the plug, a conical valve that opens and closes between the plug and the valve seat 13 and a lateral hole 17 and a longitudinal hole 18 formed in the plug to be conducted from the front end of the plug to a fuel inflow passage 28 of the rotor (rotary distributor 27), to be finally supplied to an operating chamber 29.

[0004] In contrast, the latter fuel injection pump is provided with an inner cam (circular cam 10) around a rotor (rotor 3) which operates in synchronization with an engine and plungers (12) are caused to make reciprocal movement in the direction of the radius of the rotor (rotor 3) by the cam surfaces formed on the inside of the inner cam (circular cam 10) so that the volumetric capacity of an operating chamber 19 is varied. In a pump housing, a first electromagnetic valve, which adjusts the injection start timing of fuel by opening and closing a spill passage 27 that can communicate with the operating chamber 19 and a second electromagnetic valve which adjusts the injection end timing of the fuel by opening and closing a spill passage 26 that likewise can communicate with the operating chamber 19 are provided. In each electromagnetic valve, a spool (escape valve 30 or 31) provided in a direction running at a right angle to the direction in which the rotor (rotor 3) extends is made to be displaced through power supply control of a solenoid 36 or 37. The first electromagnetic valve normally leaves the spill passage 27 which communicates with the operating chamber 19 in an open state (normal open) and when starting injection, it closes the spill passage 27 to block the spill route of the fuel supplied to the operating chamber 19, whereas the second electromagnetic valve normally leaves the spill passage 26, which communicates with the operating chamber 19, in a closed state (normal close) and when ending injection, it opens the spill passage 26 to spill the compressed fuel.

[0005] However, in the case of the former fuel injection pump, even though it has a structure in which the path leading from the fuel intake 19 to the operating chamber 29 is opened and closed by the plug provided in the direction running at a right angle to the rotor, fuel is delivered to the operating chamber of the rotor (rotary distributor 27) from the front end of the plug through the inside of the plug, lengthening the path leading from the valve seat 13 to the operating chamber. This results in a structure with an increased dead volume, which makes it difficult to raise the fuel pressure to a high level. In addition, since the solenoid portion of the electromagnetic valve projects out to the outside of the pump, the operating noise of the electromagnetic valve tends to leak to the outside, which poses a problem in that it is difficult to reduce noise.

[0006] In the case of the latter fuel injection pump, too, although the plugs of the electromagnetic valves and the rotor (rotor 3) are positioned at a right angle to each other, they are not in close enough proximity to each other to reduce the dead volume. Moreover, since the electromagnetic valves employed in this fuel injection pump adopt a system in which the spools move, a longer stroke is required in order to open and close the spill passage. This, in turn, delays the open / close operation and, at the same time, since the volumetric capacity of the spools themselves is great, noise will also be significant. In addition, in this fuel injection pump, too, since the solenoid portions of the electromagnetic valves are provided to project out from the surface of the housing, sufficient cooling cannot be achieved and this structure also limits anti-noise measures that can be taken. Furthermore, since two electromagnetic valves are required for injection control, miniaturization of the pump cannot be achieved and production cost will be high.

[0007] An object of the present invention is to provide a fuel injection pump with which the dead volume can be minimized and noise can be reduced by eliminating the problems described above. Another object of the present invention is to provide a fuel injection pump which positively promotes cooling of the electromagnetic valves and in which, when a drive unit for an electromagnetic valve is to be mounted at the pump, no sealing is required in the connected area of the electromagnetic valve and the drive unit and no wiring harness is required either.

[0008] The inventor of the present invention, taking into consideration the fact that in a fuel injection pump in which fuel is induced into the operating chamber via a passage in a rotor, it is necessary to minimize the length of the passage leading from the electromagnetic valve to the operating chamber to reduce the dead volume and the fact that it is necessary to ensure that the operating noise of the electromagnetic valve is not readily communicated to the outside to reduce the noise of the fuel injection pump, has conducted research into various alternatives in regard to the mounting position and the mounting method of the electromagnetic valve, which has resulted in the present invention.

[0009] Namely, the fuel injection pump according to the present invention is provided with a rotor provided rotatably relative to an immobile member inside a pump housing, in which a passage communicating with an operating chamber, an inflow / outflow port connecting to this passage and a distribution port are formed, a communicating passage formed at the immobile member, which causes the inflow / outflow port of the rotor and a fuel chamber to communicate with each other and an electromagnetic valve which opens and closes this communicating passage. The electromagnetic valve is housed inside the pump housing with the plug of the electromagnetic valve positioned in such a manner that it slides against the side of the rotor in a direction other than the direction of the axis of the rotor. The proximate portions of the plug and the rotor come into communication with each other at a fuel path that constitutes a portion of the communicating passage and the electromagnetic valve is structured in such a manner that its valve seat for receiving the plug is provided near this fuel path to open and close the communicating passage. This fuel injection pump may be structured so that the plug of the electromagnetic valve is positioned, for instance, in a direction running at a right angle to the direction of the axis of the rotor.

[0010] As a result, when the communicating passage is opened during the intake process of the injection pump in such a structure, fuel in the fuel chamber travels to the inflow / outflow port of the rotor via the fuel path that communicates between the proximate portions of the plug and the rotor and is then induced to the operating chamber from the inflow / outflow port via the passage in the rotor, whereas, when the communicating passage is closed during the force feed process, the path extending from the valve seat provided near the fuel path to the operating chamber becomes closed off so that fuel that has been compressed in the operating chamber is delivered through a discharge port. Then, if the closed state of the communicating passage effected by the electromagnetic valve is released during the force feed process, the compressed fuel is spilled toward the fuel chamber from the inflow / outflow port of the rotor to end fuel injection.

[0011] In this instance, the smaller the dead volume (the shorter the length of the path extending from the valve seat to the operating chamber), the easier it is to pressurize the fuel to be compressed to a high level, and if the plug of the electromagnetic valve is positioned in a direction different from the direction of the axis of the rotor at the side of the rotor, as in the present invention, it is possible to form the inflow / outflow port of the rotor at a position close to the operating chamber. In addition, by providing the proximate portions of the plug and rotor in communication with each other with the valve seat provided near this communicating portion, the distance extending from the valve seat to the inflow / outflow port of the rotor can be reduced, which results in a reduced distance overall from the valve seat to the operating chamber, achieving a reduction in the actual dead volume. Moreover, since the electromagnetic valve is housed within the pump housing, it does not become exposed out of the housing, making the operating noise of the electromagnetic valve leak to the outside less readily.

[0012] The structure described above may be optimal for a so-called VR type fuel injection pump or the like in which the operating chamber is provided at the rotor, a plurality of plunger passages extending in the direction of the radius from the operating chamber are provided at the rotor, a plunger is provided slidably in each of the plunger passages and the plungers are caused to make reciprocal movement in the direction of the radius of the rotor by an inner cam provided around the rotor, and even more preferably, the electromagnetic valve should be provided projecting out to the fuel chamber in order to forcibly cool the electromagnetic valve.

[0013] The above and other features of the invention and the concomitant advantages will be better understood and appreciated by persons skilled in the field to which the invention pertains in view of the following description given in conjunction with the accompanying drawings which illustrate preferred embodiments. In the drawings :

FIG. 1 is a schematic cross section showing an example of the fuel injection pump according to the present invention;

FIG. 2 is a cross section through a portion of the electromagnetic valve of the fuel injection pump shown in FIG. 1; and

FIG. 3 is a cross section which is an enlargement of the essential portion of FIG. 2.

[0014] In FIG. 1, which shows a distributor type fuel injection pump employing the inner cam system (opposed plunger system), a rotor 3 is provided within pump housing members 2a, 2b and 2c in a distributor type fuel injection pump 1, and the rotor 3, which is linked to a drive shaft 4, rotates upon receiving drive torque imparted by an engine (not shown) in synchronization with the engine. A feed pump 5 is secured at the drive shaft 4, and fuel in a fuel tank (not shown) is supplied via the feed pump 5 to a fuel chamber 6 in a slightly pressurized state.

[0015] The rotor 3 is inserted rotatably in a barrel 7 which is secured at the pump housing members 2a and 2b and is provided with a larger diameter portion 3a, which is formed by increasing the diameter toward the base portion with plunger passages 8 formed in the larger diameter portion, extending in the direction of the radius (radial direction). In this embodiment, for instance, four plunger passages 8 are formed over 90° intervals on the same plane and in each plunger passage 8, a plunger 9 is inserted slidably.

[0016] The front end of each plunger 9 faces opposite an operating chamber 10 provided at the center of the rotor 3, blocking the operating chamber 10, with the base end of the plunger 9 sliding in contact with the inner surface of a ring-like inner cam 13 via a shoe 11 and a roller 12. This inner cam 13 is provided concentrically to the rotor 3 around its larger diameter portion, and it is provided with cam surfaces on its inside, the number of which corresponds to the number of cylinders in the engine. When the rotor 3 rotates, each plunger 9 makes reciprocal movement in the direction of the radius of the rotor 3 (radial direction) to change the volumetric capacity of the operating chamber 10. In other words, if the inner cam 13 is formed to correspond to a four cylinder engine, it is provided with projected surfaces on its inside over 90° intervals and, consequently, four plungers 9 move simultaneously toward the operating chamber 10 to compress the operating chamber 10, and move simultaneously away from the operating chamber 10.

[0017] In the rotor 3, a longitudinal passage 15, formed in the direction of its axis and communicating with the operating chamber 10, an inflow / outflow port 16, one end of which is connected to the longitudinal passage 15 with the other end opening onto the rotor external circumferential surface covered by the barrel 7, and a distribution port 17 that is capable of communicating with the distribution passages (not shown) formed in the barrel 7 and the housing member 2b are formed.

[0018] As shown in FIGS. 2 and 3, in the barrel 7, a decentered groove 18 is formed in the portion facing opposite the inflow / outflow port 16 along the direction of the circumference of the rotor 3, and a guide hole 19 for positioning a plug 27, which is to be detailed later, in a direction running at a right angle to the direction of the axis of the rotor 3 and a connecting hole 20, which communicates between the guide hole 19 and the decentered groove 18 with the minimum distance are also formed. The guide hole 19 is connected to a receptacle hole 23 where an armature 21 is housed and a solenoid portion 22 is mounted, and in the receptacle hole 23, a storage portion 24 for housing the armature 21 is connected with a passage 25 which communicates with the fuel chamber 6. These components, namely, the passage 25, the armature storage portion 24, the guide hole 19, the connecting hole 20 and the decentered groove 18 constitute a communicating passage that makes communication possible between the inflow / outflow port 16 of the rotor 3 and the fuel chamber 6.

[0019] An electromagnetic valve 26 is provided with the plug 27 provided slidably at the guide hole 19, the armature 21 which is positioned at the receptacle hole 23 and is mounted at an end of the plug 27, the solenoid portion 22, which is fitted in the receptacle hole 23 to face opposite the armature 21 with almost half its surface including its connector exposed into the chamber, and a return spring 28 provided at the guide hole 19 to apply a constant force to the plug 27 in the direction in which the armature 21 is distanced from the solenoid portion 22. The front end of the plug 27 is made to come in contact with a stopper 29 that blocks off the guide hole 19. A large clearance is provided between the guide hole 19 and the plug 27 ranging from the connecting hole 20 through the receptacle hole 23 and, significantly, in the vicinity of the connecting hole 20, a valve seat 31, which comes in contact with a valve portion 30 formed on the circumferential surface of the plug 27, is formed. Consequently, when power is supplied to the solenoid portion 22 and the plug 27 moves against the spring force imparted by the spring 28, the valve portion 30 becomes seated on the valve seat 31 to close off the communicating passage (guide hole 19), and when power supply to the solenoid portion 22 is stopped, the plug 27 is reset by the return spring 28 and the valve portion 30 departs from the valve seat 31 to open the communicating passage (guide hole 19).

[0020] In the structure described above, when the rotor 3 rotates, the plungers 9 make reciprocal movement within plunger passages 8 of the rotor 3 in correspondence to the cam shape of the inner cam 13, and during the intake process, in which the plungers 9 move away from the operating chamber 10, no power is supplied to the solenoid portion 22 so that the guide hole 19 achieves an open state. Consequently, fuel inside the fuel chamber is in a state in which it can be supplied to the decentered groove 18 through the passage 25, the armature storage portion 24, the guide hole 19 and the connecting hole 20, and the fuel is finally taken into the operating chamber 10 after traveling through the longitudinal hole 15 via the inflow / outflow port 16 which aligns with the decentered groove 18.

[0021] After that, when the operation enters the force feed process during which the plungers 9 travel toward the operating chamber 10, power is supplied to the solenoid portion 22 and as the armature 21 is pulled the valve portion 30 of the plug 27 becomes seated on the valve seat 31 to close the guide hole 19. Thus, the fuel taken in becomes compressed by the plungers 9 and this compressed fuel is supplied to a delivery valve via one of the distribution passages from the distribution port 17, to be force fed to an injection nozzle.

[0022] Then, during the force feed process, when the power supply to the solenoid portion 22 stops, the plug 27 is reset by the spring force imparted by the return spring 28 and the valve portion 30 departs from the valve seat 31. As a result, the compressed fuel becomes spilled all at once toward the fuel chamber via the inflow / outflow port 16, the decentered groove 18, the connecting hole 20, the guide hole 19 and the like, to end the fuel injection.

[0023] Note that reference number 32 indicates a drive unit that performs ON/OFF control of the electromagnetic valve, which is mounted at the upper portion of the housing as an integrated part, and the connection with the solenoid portion is made within the pump. In addition, reference number 33 indicates a timer that causes the inner cam to rotate and to become displaced. It changes the range over which the cam is engaged and makes it possible to control the fuel feed rate in addition to control of the injection start timing and the injection end timing performed by the electromagnetic valve 26.

[0024] In the fuel injection pump 1 operated through the series of processes described above, it is desirable to achieve a high pressure in the compressed fuel and, in this embodiment, since the decentered groove 18 and the guide hole 19 are connected by the connecting hole 20 over a minimum distance and the valve seat 31, with which the valve portion 3 comes in contact, is formed at the guide hole 20 near the connecting hole, the valve seat 31 can be provided with its distance from the inflow / outflow port 16 minimized. Moreover, since the plug 27 is provided at a right angle to the rotor 3 at its side, it is possible to place the inflow / outflow port 16 close to the operating chamber 10. Thus, by reducing the length of the path extending from the valve seat 31 to the operating chamber 10, the enclosed space leading to the operating chamber 10 during the force feed process can be reduced to reduce the dead volume.

[0025] Furthermore, since the electromagnetic valve 26 is provided inside the housing, the operating noise of the electromagnetic valve 26 is not readily communicated to the outside, and since the drive unit 32 is provided at the upper portion of the electromagnetic valve to make the connection between the drive unit 32 and the solenoid portion 22 inside the pump, it is not necessary to expose the connection to the outside, eliminating the necessity for sealing the connecting portion and also eliminating the necessity for a wiring harness. Moreover, since the solenoid portion 22 of the electromagnetic valve 26 is exposed into the fuel chamber 6, fuel inside the pump is charged around the solenoid portion 22 to forcibly cool the solenoid portion 22.

[0026] As has been explained, according to the present invention, since the plug of the electromagnetic valve is provided at a side of the rotor in a direction different from the direction of the axis of the rotor, the proximate portions of the plug and the rotor are made to communicate with each other in the fuel path which constitutes a portion of the communicating passage extending from the fuel chamber to the inflow / outflow port of the rotor and the valve seat where the plug is seated is formed near the fuel path, the inflow / outflow port can be provided near the operating chamber and it is also possible to reduce the distance between the valve seat and the inflow / outflow port.

[0027] Even when the plug of the electromagnetic valve is provided in a direction different from the direction of the axis of the rotor, if the proximate portions of the plug and the rotor are not in communication with each other and a valve seat is not provided in the vicinity of the communicating portion, as in the case of the prior art, the dead volume cannot be reduced. Also, there is an added problem in the prior art in that, if the plug is constituted by a spool, the stroke cannot be shortened, making it difficult to achieve fast open / close operation of the plug. However, the present invention, which makes it possible to reduce the dead volume by reducing the distance extending from the valve seat to the operating chamber and which can also achieve the start / end control of injection with short strokes of the plug, is ideally suited for an injection pump that must satisfy the requirement for high speed operation.

[0028] Moreover, since the electromagnetic valve is provided inside the housing, less operating noise is communicated to the outside so that the noise of the injection pump itself can be reduced. In addition, if the drive unit for the electromagnetic pump is to be mounted at the top of the pump, the drive unit and the electromagnetic valve can be connected inside the pump, eliminating the necessity for sealing the connecting portion and the need for a wiring harness.

[0029] Furthermore, if the electromagnetic valve is to be provided exposed into the fuel chamber, it is possible to cool the electromagnetic valve itself with the fuel inside the pump.

Claims

1. A fuel injection pump comprising a rotor (3) provided rotatably relative to an immobile member (7) within a pump housing (2a, 2b, 2c), in which a passage (15) communicating with an operating chamber (10), an inflow / outflow port (16) connecting with said passage (15) and a distribution port (17) are formed, a communicating passage (25, 24, 19, 20, 18) formed at said immobile member (7) to communicate between said inflow / outflow port (16) of said rotor (3) and a fuel chamber (6) , and an electromagnetic valve (26) for opening and closing said communicating passage (25, 24, 19, 20, 18), with said electromagnetic valve (26) being housed within said pump housing (2a, 2b, 2c), characterized in that a plug (27) of said electromagnetic valve (26) is positioned at a side of said rotor (3) in such a manner that said plug (27) slides in a direction different from a direction of an axis of said rotor (3), proximate portions of said plug (27) and said rotor (3) are made to communicate with each other at a fuel path (20) which constitutes a portion of said communicating passage (25, 24, 19, 20, 18) and said electromagnetic valve (26) is provided with a valve seat (31) for seating said plug (27) near said fuel path (20) to open / close said communicating passage (25, 24, 19, 20, 18).

2. A fuel injection pump according to claim 1, wherein said plug (27) of said electromagnetic valve (26) is provided in a direction running at a right angle to said direction of said axis of said rotor (3).

3. A fuel injection pump according to claim 1, wherein at said immobile member (7), a decentered groove (18) that can communicate with said inflow / outflow port (16) is formed around said rotor (3), and a guide hole (19) for positioning said plug (27) is also formed, with said decentered groove (18) and said guide hole (19) being made to communicate with each other at said fuel path (20) over a nearly minimum distance.

4. A fuel injection pump according to claim 1, wherein said communicating passage (25, 24, 19, 20, 18) is constituted with a decentered groove (18) that is capable of communicating with said inflow / outflow port (16) along a circumferential direction of said rotor (3), a guide hole (19) where said plug (27) is positioned, said fuel path (20) where said decentered groove (18) and said guide hole (19) are connected with each other, an armature storage portion (24) for housing an armature (21) that is to be directly connected to said plug (27) and a passage (25) where said fuel chamber (6) and said armature storage portion (24) are connected with each other.

5. A fuel injection pump according to claim 3, wherein said valve seat (31) is provided between said fuel path (20) of said guide hole (19) and said armature storage portion (24).

6. A fuel injection pump according to claim 1 or 2, wherein said operating chamber (10) is provided at said rotor (3), a plurality of plunger passages (8) extending from said operating chamber (10) in a radial direction are provided at said rotor (3), a plunger (9) is provided slidably in each of said plunger passages(8), and said plunger (9) is made to make reciprocal movement in a direction of a radius of said rotor (3) by an inner cam (13) provided around said rotor (3).

7. A fuel injection pump according to any of claims 1, 2 and 3, wherein said electromagnetic valve (26) is provided in such a manner that a solenoid portion (22) where an electromagnetic force is generated is exposed into said fuel chamber (6).

Drawing