JP2007009750A - Seal structure for fuel pump and fuel pump provided with same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a seal structure capable of surely isolating a fuel region and an oil region in a fuel pump even if reciprocation movement of a plunger gets to high frequency, and to provide the fuel pump provided with the same. <P>SOLUTION: The seal structure for inhibiting leak of fuel and oil from a periphery of the plunger of the fuel pump is provided with seal material 51 slidingly abutting on an outer circumference surface of the plunger 23, and coil springs 53, 54 energizing the seal material toward the outer circumference surface of the plunger. Pressing force (tension force) to the outer circumference surface of the plunger by elastic force of the seal material 51 is eliminated and sealing function is exerted by only pressing force of the seal material 51 to the outer circumference surface of the plunger by energizing force of the coil springs 53, 54. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a seal structure in a fuel pump that is applied to an internal combustion engine such as a direct injection type cylinder engine and supplies high-pressure fuel toward a fuel injection valve (injector), and a fuel pump including the seal structure. . In particular, the present invention relates to an improvement in the structure for suppressing leakage of fuel and lubricating oil (hereinafter sometimes simply referred to as oil) from around the plunger.

  2. Description of the Related Art Conventionally, in an engine where high pressure is required for fuel supplied to an injector, such as an in-cylinder direct injection engine, the fuel sent from the fuel tank is pressurized with a high-pressure fuel pump and directed to the injector. To supply.

  Specifically, as disclosed in Patent Document 1 below, the configuration of the fuel supply system in this type of engine includes a feed pump that feeds fuel from a fuel tank, and fuel that is fed by this feed pump. A high-pressure fuel pump is provided. The fuel pressurized by the high-pressure fuel pump is stored in a delivery pipe to which a plurality of injectors are connected. As a result, the high-pressure fuel stored in the delivery pipe is injected from the opened injector toward the combustion chamber as the injector opens.

  In the high-pressure fuel pump, a plunger is inserted in the cylinder. The plunger receives a pressing force from the drive cam via the lifter and reciprocates in the cylinder, and adds the fuel sucked into the pressurizing chamber. It comes to press. Specifically, a retainer is attached to the lower end portion of the plunger, and this retainer is fitted into a bottomed cylindrical lifter. The drive cam is brought into contact with the lower surface of the lifter. On the other hand, the retainer is given a biasing force in a direction in which the plunger is pushed down by a coil spring (a direction in which the volume of the pressurizing chamber is enlarged). That is, when the cam nose is retracted from the lifter as the drive cam rotates, the biasing force of the coil spring acts on the plunger via the retainer, and the plunger moves downward to increase the volume of the pressurizing chamber (intake stroke) On the other hand, in a situation where the cam nose contacts the lifter, the lifter is pushed up, and the plunger moves up accordingly, and the volume of the pressurizing chamber is reduced (pressurization stroke). The above lifter has an oil introduction hole, and the oil splashed by the rotation of the camshaft is introduced into the lifter from the oil introduction hole to lubricate contact points such as the retainer, the lifter, and the coil spring. Has been done.

  By the way, this type of high-pressure fuel pump employs a seal structure in which a substantially cylindrical rubber sealing material is slidably pressed against the outer peripheral surface of the plunger. As a result, the fuel region on the upper side (pressure chamber side) from the sealing material and the oil region on the lower side (lifter side) from the sealing material are isolated. In other words, the fuel leaking from the gap between the plunger and cylinder in the fuel region flows into the oil region and the oil is diluted to deteriorate the lubrication performance, or the oil in the oil region flows into the fuel region and the fuel supply system (particularly This prevents deposits from being generated inside the injector.

  The conventional seal structure will be specifically described. The inner diameter dimension of the sealing material is designed in advance to be smaller than the outer diameter dimension of the plunger. And by inserting a plunger inside the sealing material, the inner peripheral portion of the sealing material is elastically deformed toward the outer peripheral side. That is, a pressing force toward the outer peripheral surface of the plunger (hereinafter, this elastic pressing force is referred to as “tightening force”) is generated in the sealing material, thereby exerting a sealing function.

Further, as disclosed in Patent Document 2 below, a coil spring is wound around the outer peripheral portion of the sealing material, and the pressing force toward the inner peripheral side by the coil spring is used as an assisting force (for example, a pressing force) against the pressing force. It is also practiced to prevent leakage of fuel and oil by acting as an assist force of about half of the above.
JP 2001-295730 A Japanese Utility Model Publication No. 5-40659

  By the way, in this type of high-pressure fuel pump, since the plunger reciprocates in the cylinder as described above, the holding length of the plunger by the cylinder particularly in the intake stroke (step in which the plunger moves out of the cylinder). In addition, since there is a slight clearance between the cylinder and the plunger, there is a phenomenon (plunger oscillation) in which the plunger shaft swings with respect to the cylinder shaft. Sometimes. In other words, the lower end of the plunger and its periphery may shake in a direction (lateral direction) orthogonal to the cylinder axis. In particular, in order to suppress local wear due to friction between the outer peripheral surface of the drive cam and the lower surface of the lifter, with a mechanism that rotates the lifter around its axis, the lower end of the plunger and its periphery are in the lateral direction. In addition to the reciprocation (linear reciprocation), the lower end of the plunger may be swung in the rotational direction around the axis of the cylinder due to the influence of the rotational force.

  In the conventional seal structure, the adhesion to the outer peripheral surface of the plunger depends on the elasticity of the seal material. Therefore, when each of the above vibrations occurs, the elastic deformation of the seal material (the amount of deformation per unit time) The amount of vibration per unit time: the amount of movement in the direction away from the inner surface of the sealing material) cannot be followed, and the sealing function of the sealing material may be hindered. In particular, when the engine rotates at high speed, the reciprocating movement of the plunger also becomes high frequency, and accordingly, the above-mentioned vibration period is shortened and the plunger vibration speed increases, so that the elastic deformation of the sealing material cannot follow the plunger vibration. Increases nature. As a result, a situation in which the lubrication performance is deteriorated due to the fuel leakage and the occurrence of deposits due to the oil leakage is caused. As described above, a coil spring is also attached to the outer peripheral portion of the sealing material. However, the pressing force directed toward the inner peripheral side by the coil spring acts only as an assisting force against the above-mentioned tightening force. It is not possible to avoid problems.

  The present invention has been made in view of such a point, and an object of the present invention is to reliably isolate the fuel region and the oil region in the fuel pump even when the reciprocating movement of the plunger becomes a high frequency. It is an object of the present invention to provide a fuel pump seal structure and a fuel pump including the seal structure.

  The solution of the present invention taken to achieve the above-described object is that the pressure chamber is slidably contacted with the outer peripheral surface of the plunger that pressurizes the fuel sucked into the pressure chamber by reciprocating in the cylinder. A fuel pump seal structure that separates a certain fuel region from a lubricating oil region on the side of the non-pressurizing chamber is assumed. The seal structure is provided with a seal material that is in sliding contact with the outer peripheral surface of the plunger, and an urging member that applies an urging force toward the outer peripheral surface of the plunger with respect to the seal material. And the pressing force with respect to the plunger outer peripheral surface of the sealing material by the urging force of the urging member is set larger than the pressing force to the plunger outer peripheral surface due to the elasticity of the sealing material itself (the urging force).

Due to this particular matter, when the fuel pump is driven, the plunger reciprocates in the cylinder with its outer peripheral surface slidingly in contact with the inner surface of the sealing material, thereby sucking fuel into the pressurized chamber (
The suction stroke) and the pressurization of the fuel in the pressurization chamber (pressurization stroke) are repeated, and the high-pressure fuel is discharged. In such a driving operation, since the sealing material receives a large pressing force against the outer peripheral surface of the plunger from the urging member, the deformation of the sealing material is caused by the urging force from the urging member rather than the elasticity of the sealing material itself. The direction of action is dominant. For this reason, even if the phenomenon that the axis of the plunger sways with respect to the axis of the cylinder (plunger swing) occurs, the sealing material can be deformed per unit time. It is possible to follow the deflection of the plunger by receiving the urging force from the urging member without depending on the amount of deformation), and the deformation of the seal material (the amount of deformation per unit time) The seal function is maintained well by following the amount of vibration). This phenomenon is the same even when the reciprocating movement of the plunger becomes a high frequency and the period of the shake is shortened. As a result, a stable sealing function can always be maintained regardless of the driving state of the fuel pump, and the fuel leaking from the gap between the plunger and the cylinder in the fuel region flows into the lubricating oil region and the lubricating oil is diluted. Thus, it is possible to avoid a situation in which the lubrication performance is deteriorated or the lubricating oil in the lubricating oil region flows into the fuel region and deposits are generated inside the fuel supply system.

  Moreover, the following is mentioned as a structure which the said effect appears notably. In other words, the inner diameter dimension of the sealing material is set substantially equal to the outer diameter dimension of the plunger or larger than the outer diameter dimension of the plunger, and the sealing material is deformed toward the inner peripheral side only by the biasing force of the biasing member. The plunger is pressed against the outer peripheral surface of the plunger. That is, the pressing force on the outer peripheral surface of the plunger due to the elasticity of the sealing material itself (the above urging force) is set to “0”, and the sealing function is exhibited only by the pressing force on the outer peripheral surface of the plunger of the sealing material by the urging force of the urging member. It is. According to this, the deformation of the sealing material is governed only by the action of the urging force from the urging member, and does not depend on the elastic deformation of the sealing material itself. For this reason, even if the phenomenon that the shaft center of the plunger sways with respect to the shaft center of the cylinder occurs, the sealing material can quickly follow the swing of the plunger, and a high sealing function can be ensured.

  More specific seal structures include the following. That is, the seal material is provided with a fuel seal portion that is in sliding contact with the plunger outer peripheral surface on the fuel region side, and an oil seal portion that is in sliding contact with the plunger outer peripheral surface on the lubricating oil region side. Then, an urging member is attached to each outer peripheral portion of each seal portion, and the pressing force on the plunger outer peripheral surface of the sealing material by the urging force of the urging member is greater than the pressing force on the plunger outer peripheral surface due to the elasticity of the sealing material itself. Is set larger.

  In this way, the fuel region side seal portion (fuel seal portion) and the lubricating oil region side seal portion (oil seal portion) are separately provided, and by attaching individual urging members to each, the fuel region side It is possible to individually apply seal structures suitable for preventing fuel leakage from the lubricating oil and preventing lubricating oil leakage from the lubricating oil region side. For example, when the urging member is composed of a coil spring, the spring diameter of the coil spring attached to the fuel seal portion and the spring constant thereof are different from the spring diameter of the coil spring attached to the oil seal portion and the spring constant thereof. It is possible to apply a technique such as

  A fuel pump in which the fuel region and the lubricating oil region are isolated by the fuel pump seal structure described in any one of the above-described solutions is also within the scope of the technical idea of the present invention.

In the present invention, as a seal structure for suppressing the leakage of fuel and lubricating oil from around the plunger of the fuel pump, the deformation of the seal material is less than the elasticity of the seal material itself from the biasing member as an external force. The action of the urging force is made dominant. As a result, even when the swinging phenomenon occurs in the plunger, it becomes possible to cause the sealing material to quickly follow the swing of the plunger. For this reason, even when the reciprocating movement of the plunger becomes a high frequency and the period of the deflection is shortened, a stable sealing function can always be maintained, and the fuel area leaks from the gap between the plunger and the cylinder. Avoid situations where the fuel flows into the lubricating oil region and the lubricating oil is diluted to degrade the lubricating performance, or the lubricating oil in the lubricating oil region flows into the fuel region and deposits are generated inside the fuel supply system. And high reliability can be obtained for the fuel pump.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case where the present invention is applied to a high-pressure fuel pump used in an in-cylinder direct injection multi-cylinder (for example, four-cylinder) gasoline engine mounted on an automobile will be described.

-Fuel supply device 100-
Before describing the specific configuration of the high-pressure fuel pump, the schematic configuration of the fuel supply apparatus 100 to which the high-pressure fuel pump is applied will be described. FIG. 1 is a diagram schematically showing the structure of a fuel supply device 100 in the present embodiment. As shown in FIG. 1, a fuel supply apparatus 100 includes a feed pump 102 that sends out fuel from a fuel tank 101, and a fuel injection valve 4 for each cylinder (four cylinders) by pressurizing the fuel sent out by the feed pump 102. , 4,... Are provided.

  As a schematic configuration of the high-pressure fuel pump 1 (the specific configuration will be described later with reference to FIG. 3), a cylinder 21, a plunger 23, a pressurizing chamber 22, and an electromagnetic spill valve 30 are provided. The plunger 23 is driven by the rotation of a drive cam 111 attached to the exhaust camshaft 110 of the engine, and reciprocates in the cylinder 21. By the reciprocating movement of the plunger 23, the volume of the pressurizing chamber 22 is enlarged or reduced. In the present embodiment, two cam peaks (cam noses) 112 and 112 are formed on the drive cam 111 with an angular interval of 180 ° around the rotation axis of the exhaust camshaft 110. The plungers 23 are pushed up by the cam noses 112, 112, and the plungers 23 are moved in the cylinder 21. Since the engine according to this embodiment is a four-cylinder type, a total of 4 fuel injection valves 4 are provided once for each cylinder during one cycle of the engine, that is, while the crankshaft rotates twice. Fuel injection is performed once. In this engine, the exhaust camshaft 110 rotates once every time the crankshaft rotates twice. Therefore, the fuel injection from the fuel injection valve 4 is performed four times, and the discharge operation from the high-pressure fuel pump 1 is performed twice, every cycle of the engine.

  The pressurizing chamber 22 is partitioned by a plunger 23 and a cylinder 21. The pressurizing chamber 22 communicates with the feed pump 102 via a low-pressure fuel pipe 104, and communicates with a delivery pipe (pressure accumulating vessel) 106 via a high-pressure fuel pipe 105.

  The fuel injection valves 4, 4,... Are connected to the delivery pipe 106, and a fuel pressure sensor 161 for detecting the fuel pressure (actual fuel pressure) in the delivery pipe 106 is disposed. In addition, a return pipe 172 is connected to the delivery pipe 106 via a relief valve 171. The relief valve 171 opens when the fuel pressure in the delivery pipe 106 exceeds a predetermined pressure (for example, 13 MPa). By opening the valve, a part of the fuel stored in the delivery pipe 106 is returned to the fuel tank 101 via the return pipe 172. Thereby, an excessive increase in the fuel pressure in the delivery pipe 106 is prevented. The return pipe 172 and the high-pressure fuel pump 1 are connected by a fuel discharge pipe 108 (shown by a broken line in FIG. 1), and the fuel leaked from the gap between the plunger 23 and the cylinder 21 is sealed unit 5. The fuel is stored in the upper fuel storage chamber 6 and then returned to the fuel discharge pipe 108 connected to the fuel storage chamber 6.

  Note that the low-pressure fuel pipe 104 is provided with a filter 141 and a pressure regulator 142. The pressure regulator 142 returns the fuel in the low-pressure fuel pipe 104 to the fuel tank 101 when the fuel pressure in the low-pressure fuel pipe 104 exceeds a predetermined pressure (for example, 0.4 MPa). The fuel pressure is maintained below a predetermined pressure. Further, the low pressure fuel pipe 104 is provided with a pulsation damper 107, and the pulsation damper 107 suppresses fuel pressure pulsation in the low pressure fuel pipe 104 when the high pressure fuel pump 1 is operated. . The high pressure fuel pipe 105 is provided with a check valve 151 for preventing the fuel discharged from the high pressure fuel pump 1 from flowing backward.

  The high-pressure fuel pump 1 is provided with the electromagnetic spill valve 30 for communicating or blocking between the low-pressure fuel pipe 104 and the pressurizing chamber 22. The electromagnetic spill valve 30 includes an electromagnetic solenoid 31 and opens and closes by controlling energization of the electromagnetic solenoid 31. The electromagnetic spill valve 30 is opened by the biasing force of the coil spring 37 when the energization of the electromagnetic solenoid 31 is stopped. Hereinafter, the opening / closing operation of the electromagnetic spill valve 30 will be described with reference to FIG.

  First, when the energization of the electromagnetic solenoid 31 is stopped, the electromagnetic spill valve 30 is opened by the biasing force of the coil spring 37, and the low pressure fuel pipe 104 and the pressurizing chamber 22 are in communication with each other. In this state, when the plunger 23 moves in the direction in which the volume of the pressurizing chamber 22 increases (intake stroke), the fuel sent from the feed pump 102 is sucked into the pressurizing chamber 22 through the low-pressure fuel pipe 104. Is done.

  On the other hand, when the plunger 23 moves in the direction in which the volume of the pressurizing chamber 22 contracts (pressurization stroke), the electromagnetic spill valve 30 is closed against the urging force of the coil spring 37 by energizing the electromagnetic solenoid 31. Then, the low-pressure fuel pipe 104 and the pressurizing chamber 22 are disconnected, and when the fuel pressure in the pressurizing chamber 22 reaches a predetermined value, the check valve 40 is opened, and the high-pressure fuel is supplied to the high-pressure fuel pipe 105. And is discharged toward the delivery pipe 106.

  The fuel discharge amount in the high-pressure fuel pump 1 is adjusted by controlling the closing period of the electromagnetic spill valve 30 in the pressurization stroke. That is, if the closing time of the electromagnetic spill valve 30 is advanced and the closing period is lengthened, the fuel discharge amount increases. If the closing start time of the electromagnetic spill valve 30 is delayed and the closing period is shortened, the fuel discharge amount decreases. To come. In this manner, the fuel pressure in the delivery pipe 106 is controlled by adjusting the fuel discharge amount of the high-pressure fuel pump 1.

  Here, the pump duty DT which is a control amount for controlling the fuel discharge amount of the high-pressure fuel pump 1 (the valve closing start timing of the electromagnetic spill valve 30) will be described.

  The pump duty DT varies between 0 and 100%, and is a value related to the cam angle of the drive cam 111 of the exhaust camshaft 110 corresponding to the valve closing period of the electromagnetic spill valve 30. .

Specifically, as shown in FIG. 2, regarding the cam angle of the drive cam 111, the cam angle (maximum cam angle) corresponding to the maximum valve closing period of the electromagnetic spill valve 30 is θ0, and the target of the maximum valve closing period is set. Assuming that the cam angle (target cam angle) corresponding to the fuel pressure is θ, the pump duty DT is expressed by the ratio of the target cam angle θ to the maximum cam angle θ0 (DT = θ / θ0). Therefore, the pump duty DT becomes a value closer to 100% as the closing period (closing timing) of the target electromagnetic spill valve 30 approaches the maximum closing period, and the target closing period becomes “0”. The closer it is, the closer to 0%.

  And as the pump duty DT approaches 100%, the valve closing start timing of the electromagnetic spill valve 30 adjusted based on the pump duty DT is advanced, and the valve closing period of the electromagnetic spill valve 30 becomes longer. As a result, the fuel discharge amount of the high-pressure fuel pump 1 increases and the actual fuel pressure increases. Further, as the pump duty DT approaches 0%, the valve closing start timing of the electromagnetic spill valve 30 adjusted based on the pump duty DT is delayed, and the valve closing period of the electromagnetic spill valve 30 is shortened. As a result, the fuel discharge amount of the high-pressure fuel pump 1 is reduced and the actual fuel pressure is lowered. The details of the procedure for calculating the pump duty DT are omitted here.

-Specific configuration of high-pressure fuel pump 1-
Next, a specific configuration of the high-pressure fuel pump 1 will be described with reference to FIG. FIG. 3 is a longitudinal sectional view of the high-pressure fuel pump 1. As shown in FIG. 3, the high-pressure fuel pump 1 of the present embodiment has a configuration in which a pump unit 20, the electromagnetic spill valve 30 and a check valve 40 are provided in a housing 10.

  The pump unit 20 includes a cylinder 21, a pressurizing chamber 22, a plunger 23, a lifter 24, and a lifter guide 25. The cylinder 21 is formed at the center of the housing 10, and a pressurizing chamber 22 is formed at the tip side (the upper end side in FIG. 3). The plunger 23 has a cylindrical shape and is inserted into the cylinder 21 so as to be slidable in the axial direction. The lifter 24 is formed in a bottomed cylindrical shape, and a base end portion of the plunger 23, a retainer 26, a coil spring 27, and the like described later are accommodated therein. The lifter guide 25 is a cylindrical member attached to the lower side of the housing 10, and the lifter 24 is accommodated therein so as to be slidable in the axial direction.

  A retainer 26 is engaged with the proximal end portion of the plunger 23. Specifically, a small-diameter portion 23a is provided at the base end portion of the plunger 23, and a groove 26a having a width that substantially matches the outer diameter of the small-diameter portion 23a is formed in the retainer 26. By inserting the small-diameter portion 23a into 26a, the base end portion of the plunger 23 is reciprocally engaged with the retainer 26 integrally. A spring seat member 25a is fitted into the upper portion of the lifter guide 25, and a coil spring 27 is disposed in a compressed state between the lower surface of the spring seat member 25a and the retainer 26. That is, the coil spring 27 applies a downward biasing force to the plunger 23, and the lifter 24 is biased toward the drive cam 111. The center position of the outer peripheral surface of the drive cam 111 (the center position of the drive cam 111 in the rotation axis direction) and the center point of the lower surface of the lifter 24 are shifted (eccentric) along the rotation axis direction of the drive cam 111. Both of these are so-called offset arrangement. Further, as the direction of the offset, the lifter 24 is rotated in the clockwise direction in a plan view using a frictional force between the outer peripheral surface of the drive cam 111 and the lower surface of the lifter 24.

  The electromagnetic spill valve 30 is disposed opposite to the pressurizing chamber 22 and includes the electromagnetic solenoid 31, bobbin 32, core 33, armature 34, poppet valve 35, and sheet body 36. The electromagnetic solenoid 31 is a coil wound around the bobbin 32 in a ring shape, and the core 33 is fitted and fixed in the central through hole of the bobbin 32. The armature 34 is fixed to one end of the poppet valve 35, and a part of the armature 34 is arranged coaxially with the core 33 so as to be able to enter the central through hole of the bobbin 32. Concave portions are respectively formed on the opposing surfaces of the core 33 and the armature 34, and a coil spring 37 is accommodated in a compressed state between the concave portions. The coil spring 37 urges the armature 34 toward the pressurizing chamber 22 side.

  The poppet valve 35 is slidably inserted into a through-hole in the sheet body 36, and a disc-shaped valve body 35a is formed at the lower end thereof. When the electromagnetic solenoid 31 is not energized, the valve body 35a is separated from the seat portion 36a of the seat body 36 by the biasing force of the coil spring 37, and the electromagnetic spill valve 30 is opened. On the other hand, when the electromagnetic solenoid 31 is energized through a terminal 38 from an electronic control device (not shown), a magnetic circuit is formed by the support member 39 that supports the core 33, the armature 34, and the electromagnetic spill valve 30 as a whole. The armature 34 moves to the core 33 side against the urging force. As a result, the poppet valve 35 moves to the side opposite to the pressurizing chamber 22, the valve body 35a comes into contact with the seat portion 36a of the seat body 36, and the electromagnetic spill valve 30 is closed (shown in FIG. 3). Status).

  On the other hand, when the electromagnetic spill valve 30 is in the open state, fuel can flow between the plurality of supply passages 36 b formed in the seat body 36 and the pressurizing chamber 22.

  A low pressure fuel passage 11 is formed in the housing 10 so as to communicate with the supply passage 36b. When the plunger 23 descends with the electromagnetic spill valve 30 open, the low pressure fuel pumped up from the fuel tank 101 by the operation of the feed pump 102 is filtered 141, the pressure regulator 142, the low pressure fuel passage 11 and the supply passage. The air is sucked into the pressurizing chamber 22 through 36b.

  The pressurizing chamber 22 formed on the tip side of the cylinder 21 is formed with a larger diameter than the inner peripheral surface of the cylinder 21. The plunger 23 enters the pressurizing chamber 22 before the closing timing of the electromagnetic spill valve 30, and the plunger 23 reaches the top dead center after the electromagnetic spill valve 30 is closed. In addition, a gap is formed between the inner peripheral surface of the pressurizing chamber 22 and the outer peripheral surface of the plunger 23 in a state where the distal end portion of the plunger 23 has entered the pressurizing chamber 22. A high pressure fuel passage 12 is formed in the housing 10, and the pressurizing chamber 22 communicates with the check valve 40 through the high pressure fuel passage 12.

  The check valve 40 includes a casing 41 connected to the high-pressure fuel passage 12, a seat body 42 and a spring base body 45 disposed in the casing 41, and a valve body (valve that faces the seat body 42 detachably). Body) 43 and a coil spring 44 that urges the valve body 43 toward a contact position with respect to the seat body 42. The check valve 40 is connected to the high pressure fuel pipe 105. When the pressure of the fuel pumped from the pressurizing chamber 22 through the high pressure fuel passage 12 exceeds a predetermined value, the valve body 43 is separated from the seat body 42 against the urging force of the coil spring 44. Moved to. As a result, the check valve 40 is opened, and the high-pressure fuel pumped from the high-pressure fuel passage 12 is supplied to the delivery pipe 106 via the high-pressure fuel pipe 105.

-Configuration of seal unit 5-
Next, the seal unit 5 that is a feature of the present embodiment will be described. The seal unit 5 includes a rubber seal material 51, a support member 52 that supports the seal material 51, and two coil springs 53 and 54 as biasing members attached to the outer periphery of the seal material 51. Yes. Each will be described below.

The sealing material 51 is made of PTFE (polytetrafluoroethylene) -based rubber, and is formed into a substantially cylindrical shape (barrel shape) in which a central portion in the vertical direction slightly protrudes to the outer peripheral side. Specifically, as shown in FIG. 4 (cross-sectional view of the seal unit 5 and its peripheral portion) and FIG. 5 (side view of the seal unit 5 and its peripheral portion), a groove 51a is formed on the outer peripheral portion at a substantially central position in the vertical direction. The lower end of the support member 52 is fitted into the groove 51a. The support member 52 is a metal-made cylindrical member, and a lower end portion is formed as a flange portion 52 a extending toward the inner peripheral side, and the flange portion 52 a is fitted into the groove 51 a of the sealing material 51. ing. On the other hand, the upper end portion of the support member 52 is press-fitted into the inner peripheral surface of the spring seat member 25a. As a result, the sealing material 51 is supported by the spring seat member 25 a via the support member 52.

  The sealing material 51 is configured as a fuel seal portion 55 above the position where the groove 51a is formed, and as an oil seal portion 56 below the position where the groove 51a is formed. In the fuel seal portion 55, the fuel leaked from the gap between the plunger 23 and the cylinder 21 in the fuel region above the seal material 51 (on the pressurizing chamber 22 side) is below (lifter side) below the seal material. It is a seal portion for preventing leakage toward a certain oil region. On the other hand, the oil seal portion 56 is a seal portion for preventing the oil in the oil region from leaking toward the fuel region.

  Hereinafter, the seal portions 55 and 56 will be described. On the inner peripheral surfaces of the fuel seal portion 55 and the oil seal portion 56, lip portions 55a and 56a having a substantially semicircular cross-sectional shape are continuously formed over the entire circumferential direction. The tips of the lip portions 55 a and 56 a are in contact with the outer peripheral surface of the plunger 23. That is, the fuel region and the oil region are separated from each other by the tips of the lip portions 55a and 56a contacting (circular line contact) in the circumferential direction of the outer peripheral surface of the plunger 23.

  As one of the features of the sealing material 51, the inner diameter dimension (dimension T in FIG. 4) of each of the lip portions 55a and 56a is the outer diameter of the plunger 23 in the state where no external force is applied to the sealing material 51. Approximate to the dimensions. That is, when the plunger 23 is inserted into the center hole of the sealing material 51 in a state where no external force is applied to the sealing material 51 (the state where the coil springs 53 and 54 are not attached), the sealing material 51 Has a configuration in which elastic deformation does not occur, that is, a configuration in which the above-described “tightening force” does not occur. Note that only the lip portions 55a and 56a are in contact with the plunger 23 in the sealing material 51, and the region between the lip portions 55a and 56a recedes from the outer peripheral surface of the plunger 23, and is in contact with the outer peripheral surface. A space S is formed between them. If fuel or oil leaks, the space S is temporarily stored.

  On the other hand, spring mounting grooves 55b and 56b having substantially semicircular cross sections for mounting the coil springs 53 and 54, respectively, are formed on the outer peripheral surfaces of the fuel seal portion 55 and the oil seal portion 56 in the circumferential direction. Yes. Further, a stopper portion 55c for preventing the mounted coil spring 53 from coming off is formed on the outer side of the upper spring mounting groove 55b. Similarly, a stopper portion 56c for preventing the mounted coil spring 54 from coming off is formed on the outer side of the lower spring mounting groove 56b.

Each of the coil springs 53 and 54 is formed in an endless annular shape, and its inner diameter is set smaller than the outer diameter of the spring mounting grooves 55b and 56b when no external force is applied. For this reason, when the coil springs 53 and 54 are mounted (fitted) into the spring mounting grooves 55b and 56b, the coil springs 53 and 54 are extended, and the extension causes the pressing force (the sealing material 51 to be moved toward the inner peripheral side). A pressing force for narrowing inward) can be generated at the lip portions 55a and 56a of the sealing material 51. In other words, the lip portions 55 a and 56 a are uniformly pressed over the entire circumference of the outer peripheral surface of the plunger 23 by this pressing force. In other words, the contact force obtained by pressing the lip portions 55a and 56a around the entire outer peripheral surface of the plunger 23 can be obtained from the coil springs 53 and 54 without using the “tightening force” of the seal material 51. The structure is obtained only by the urging force. More specifically, for example, the tension force is set to “0N” and the coil springs 53 and 54 are set.
The urging force is set to “10N”.

  Further, when comparing the coil springs 53 and 54, the spring diameter of the coil spring 54 attached to the oil seal portion 56 is larger than the spring diameter of the coil spring 53 attached to the fuel seal portion 55. The diameter is set.

-Explanation of sealing operation-
Next, the sealing operation of the seal unit 5 when the high-pressure fuel pump 1 is driven will be described. When the high-pressure fuel pump 1 is driven, the plunger 23 reciprocates in the cylinder 21 while the outer peripheral surface thereof is in sliding contact with the lip portions 55 a and 56 a of the sealing material 51, thereby sucking fuel into the pressurizing chamber 22. (Intake stroke) and pressurization of fuel in the pressurizing chamber 22 (pressurization stroke) are repeated, and high-pressure fuel is supplied to the delivery pipe 106.

  In such a driving operation, the seal portions 55 and 56 of the seal material 51 receive a large pressing force from the coil springs 53 and 54 toward the outer peripheral surface of the plunger 23. The action of the urging force from the coil springs 53 and 54 is more dominant than the elasticity of the material itself. For this reason, even if the phenomenon that the shaft center of the plunger 23 sways with respect to the shaft center of the cylinder 21 (the above-described swinging of the plunger 23) occurs, the sealing material 51 has an elastic deformation amount ( It is possible to quickly follow the swing of the plunger 23 by receiving the urging force from the coil springs 53 and 54 without depending on the amount deformable per unit time), and the deformation of the sealing material 51 (per unit time). The amount of deformation) easily follows the vibration of the plunger 23 (the amount of vibration per unit time), and the sealing function is maintained well. This phenomenon can be obtained even when the reciprocating movement of the plunger 23 becomes a high frequency and the period of the deflection is shortened. As a result, a stable sealing function can always be maintained regardless of the driving state of the high-pressure fuel pump 1, and the fuel leaked from the gap between the plunger 23 and the cylinder 21 in the fuel region flows into the oil region and the oil flows. It is possible to avoid a situation where the dilution causes deterioration of the lubrication performance or the situation where the oil in the oil region flows into the fuel region and deposits are generated inside the fuel supply system, and the high-pressure fuel pump 1 has high reliability. Can be obtained.

(Modification)
In the embodiment described above, the inner diameter dimensions of the lip portions 55a and 56a of the sealing material 51 are substantially matched to the outer diameter dimensions of the plunger 23 in a state where no external force is applied to the sealing material 51. That is, the sealing material 51 is configured not to generate the tightening force.

  In this modification, instead, a slight tension force is generated on the sealing material 51. Specifically, the inner diameter dimension of each of the lip portions 55a and 56a of the sealing material 51 is set slightly smaller than the outer diameter dimension of the plunger 23 in a state where no external force is applied to the sealing material 51 so that the tension force is increased. The configuration is such that the urging force applied to the sealing material 51 by the coil springs 53 and 54 is larger than the magnitude of the tightening force. More specifically, the tension force is “3N”, and the biasing force of the coil springs 53 and 54 is “7N”.

  Even in the configuration of the present modification, as in the case of the above-described embodiment, even when the plunger 23 swings, the sealing member 51 receives the urging force from the coil springs 53 and 54 to quickly move the plunger 23. It is possible to follow, and the sealing function can be maintained well.

(Experimental example)
Next, the results of experiments conducted to confirm the effects of the present invention will be described. In this experiment, the amount of fuel leakage and the amount of oil leakage from the periphery of the sealing material 51 were measured while changing the tension force and the urging force of the coil springs 53 and 54, and gradually increasing the rotational speed of the camshaft. Specifically, as shown in Table 1 below, as the conventional example I, the tension force was set to “10N”, and the biasing force of the coil spring was set to “0N (no coil spring mounted)”, as the conventional example II The tension force was set to “7N” and the biasing force of the coil spring was set to “3N”, and as the conventional example III, the tension force was set to “5N” and the biasing force of the coil spring was set to “5N”. That is, in each case, the tension force is set to be greater than or equal to the biasing force of the coil spring, and the sum of the tension force and the biasing force of the coil spring is “10N”. On the other hand, the present invention I is the above-described modified example, that is, the tightening force is “3N”, and the biasing force of the coil spring is “7N”, and the present invention II is the above embodiment, that is, the tightening force is “0N” was used, and the biasing force of the coil spring was “10N”. In other words, both are set such that the biasing force of the coil spring exceeds the tension, and the sum of the tension and the biasing force of the coil spring is “10N”.

  The experimental results are shown in FIG. FIG. 6A shows the measurement result of the amount of fuel leakage when the rotational speed of the cam shaft is gradually increased, and FIG. 6B shows the amount of oil leakage when the rotational speed of the cam shaft is gradually increased. The measurement results are shown.

  As is clear from these experimental results, in the conventional example, that is, in the case where the tension force is set to be greater than the urging force of the coil spring, the region of a relatively low rotational speed (about 1000 rpm in the conventional example I). However, there is a phenomenon in which the amount of leakage of fuel and oil increases as the rotational speed of the camshaft increases. On the other hand, in the present invention, the fuel and oil leaks do not occur unless the rotational speed of the camshaft becomes considerably high (even if the present invention I does not significantly exceed 3000 rpm), and the amount of fuel and oil leaks. Even if a gradually increasing phenomenon starts to occur, the rate of increase in the amount of leakage of fuel and oil with respect to the rate of increase in the rotational speed of the camshaft is kept low (see the small slope of the graph). This experimental result confirms the effect of the present invention.

(Other embodiments)
In the embodiment and the modification described above, the case where the present invention is applied to an in-cylinder direct injection type four-cylinder gasoline engine mounted on an automobile has been described. The present invention is not limited to this, and can be applied to other arbitrary number of cylinders such as a direct injection type 6 cylinder gasoline engine. Further, the present invention is not limited to a gasoline engine, but can be applied to other internal combustion engines such as a diesel engine. Furthermore, the engine to which the present invention is applicable is not limited to an automobile engine.

  Moreover, in the said embodiment and modification, although the coil springs 53 and 54 were applied as a biasing member which gives the biasing force which goes to a plunger outer peripheral surface with respect to the sealing material 51, this invention is not limited to this, The sealing material 51 Any member that can uniformly press the lip portions 55a and 56a against the outer peripheral surface of the plunger 23 may be used. For example, a snap ring or the like may be used.

  Further, the material of the sealing material 51 is not limited to that of the above-described embodiment and the modified example, and a synthetic resin or the like is used as long as the material is deformed toward the outer peripheral surface of the plunger by receiving the urging force of the coil springs 53 and 54. May be.

  In the high-pressure fuel pump 1 in the above embodiment and the modification, the plunger 23 is driven by the rotation of the drive cam 111 attached to the exhaust camshaft 110. However, the drive cam attached to the intake camshaft The plunger 23 may be driven by rotation.

  Furthermore, the present invention is not limited to the one provided with the drive cam 111 having the two cam noses 112 and 112 but can be applied to the one provided with the drive cam having other numbers of cam noses.

It is a figure which shows typically the structure of the fuel supply apparatus which concerns on embodiment. It is a figure for demonstrating the opening / closing operation | movement of an electromagnetic spill valve. It is a longitudinal cross-sectional view which shows a high pressure fuel pump. It is sectional drawing which shows a seal unit and its peripheral part. It is a side view which shows a seal unit and its peripheral part. It is a figure which shows the result of the experiment conducted in order to confirm the effect of this invention, (a) shows the measurement result of fuel leak amount, (b) is a figure which shows the measurement result of oil leak amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High pressure fuel pump 21 Cylinder 22 Pressurization chamber 23 Plunger 51 Sealing material 53, 54 Coil spring (biasing member)
55 Fuel seal 56 Oil seal

Claims (4)

The fuel region on the pressurizing chamber side and the lubricating oil region on the non-pressurizing chamber side are isolated by slidingly contacting the outer peripheral surface of the plunger that pressurizes the fuel sucked into the pressurizing chamber by reciprocating in the cylinder. In the fuel pump seal structure,
A sealing material that is in sliding contact with the plunger outer peripheral surface, and a biasing member that applies a biasing force toward the plunger outer peripheral surface with respect to the sealing material,
The fuel pump seal is characterized in that the pressing force of the sealing member against the plunger outer peripheral surface by the biasing force of the biasing member is set larger than the pressing force to the plunger outer peripheral surface due to the elasticity of the sealing material itself. Construction. In the fuel pump seal structure according to claim 1,
The inner diameter dimension of the sealing material is set to be substantially equal to the outer diameter dimension of the plunger or larger than the outer diameter dimension of the plunger, and the plunger is deformed toward the inner peripheral side only by the urging force of the urging member. A fuel pump seal structure, wherein the fuel pump is pressed against an outer peripheral surface. In the fuel pump seal structure according to claim 1 or 2,
The sealing material includes a fuel seal portion that is in sliding contact with the outer peripheral surface of the plunger on the fuel region side, and an oil seal portion that is in sliding contact with the outer peripheral surface of the plunger on the lubricating oil region side. Each of these is mounted, and the pressing force on the plunger outer peripheral surface of the sealing material by the urging force of the urging member is set to be larger than the pressing force on the plunger outer peripheral surface due to the elasticity of the sealing material itself. Characteristic fuel pump seal structure.   A fuel pump characterized in that the fuel region and the lubricating oil region are isolated by the seal structure of the fuel pump according to any one of claims 1 to 3.

Images