JP2001280220A - High pressure fuel pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-pressure fuel pump equipped with a good sealing performance. SOLUTION: The high-pressure fuel pump includes a fuel supply passage to put the peripheral surface of a plunger in communication with the end on the side with pressure chamber and a valve mechanism to open and close the passage. A seal member is installed between the plunger and each cylinder on the counter pressure chamber side more than a fuel inlet provided in the plunger peripheral surface. This lessens the pressure difference between the sides of the seal member, to allow establishing a good sealing performance and also prolongation of the lifetime of the seal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel pump for an internal combustion engine, and more particularly to a high-pressure fuel pump suitable for a direct injection type internal combustion engine in which fuel is directly injected into a cylinder from an injection valve.

[0002]

2. Description of the Related Art In-cylinder direct fuel injection type is under study.
In an in-cylinder direct fuel injection device, a high-pressure fuel of 3 MPa or more needs to be supplied to a fuel injection valve in order to inject fuel directly into a cylinder in an internal combustion engine.

[0003] This type of high-pressure side pump is of a reciprocating plunger type, and is provided with a plunger and a cylinder for preventing the fuel introduced into a pump chamber formed between the plunger and the cylinder bore from leaking to the drive side. A sealing member is provided between them (see U.S. Pat. No. 2519893).

[0004]

In the conventional structure, the fuel pressure in the suction passage is applied to one side of the seal between the reciprocating plunger and the cylinder, and the pressure in the pump chamber (pressurizing chamber) is applied to the other side. Fuel pressure acts. For this reason, there was a problem that the pressure difference was too large and the sealing was insufficient.

[0005] It is an object of the present invention to reduce the differential pressure of the fuel pressure acting on both ends of a seal member provided between a plunger and a cylinder to improve the sealing effect.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuel supply passage which connects a peripheral surface of a plunger with an end of the plunger on the side of a pressurizing chamber, and a valve mechanism which opens and closes the passage in accordance with reciprocation of the plunger. This is attained by providing a seal member for sealing between the plunger and the cylinder on the side of the plunger peripheral surface opposite to the fuel inlet from the fuel inlet. With this configuration, the pressure difference between the fuel pressures acting on both sides of the seal portion can be reduced, and the seal can be improved. Specifically, a plunger reciprocating in the cylinder bore inserts a reciprocating seal on the cylinder side extending in the longitudinal direction from the cylinder bore, and forms a metal ring for allowing the reciprocating seal itself to be press-fitted into the cylinder. . The side of the reciprocating seal that seals the fuel is provided in a space formed by a cylinder, a plunger, and a reciprocating seal to communicate with the suction side passage of the high-pressure pump, and the other is on the oil side of the engine. Further, the reciprocating seal is provided at a place where a gap of 3 mm between the plunger and the cylinder bore is secured from the pump chamber formed in the plunger and the cylinder bore to 7 μm and a seal distance (a fitting length between the plunger and the cylinder bore) of 10 mm or more is secured. I do. By doing so, the fuel seal by the reciprocating seal is improved, and at the same time, the fuel from the reciprocating seal does not need to be returned to the tank, and the piping to the fuel tank is not required.

[0007] More preferably, since a resistance to the pump suction pressure acting on the reciprocating seal is required, a projection for reinforcing the lip of the seal is provided on the opposite side of the reciprocating seal where the suction pressure acts, and the projection is provided outside the plunger. It is necessary to form a supporting member that suppresses deformation of the seal against the diameter. The reciprocating seal seals two liquids, fuel and oil, which are formed from two lips to seal each liquid. The protrusion is formed on the fuel side where pressure acts from the center between the lips. The metal ring for press-fitting the reciprocating seal into the cylinder is bent and extends between the two lips to prevent deformation of the seal lip. However, the rubber material, which is a sealing material in the fuel, has a large swelling due to the fuel, and when the protrusion comes to a portion corresponding to the metal ring portion, the volume change due to the swelling increases, and the surface pressure on the plunger increases. Tend. Therefore, it is necessary to provide the projection so as not to cover the metal ring. If possible, it is more advantageous to provide the protrusion on the fuel side where pressure acts, from the viewpoint of the support function by pressure.

On the other hand, a seal portion made of the same material as a lip portion for preventing fuel leakage from the press-fit portion of the metal ring of the reciprocating seal is formed, and the fuel is sealed between the cylinder and the cylinder.

By doing so, the above problem can be solved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment is shown in FIG.

The coupling 1 for transmitting the driving force transmitted from the engine camshaft has a shaft 5 connected to the coupling 1 by a pin 3 fitted to the coupling 1. The shaft 5 has a swash plate surface 5a formed as an oblique flat plate that spreads in the radial direction. A slipper 7 contacts the swash plate surface 5a,
The swash plate side of the slipper 7 is substantially flat so that it can slide smoothly on the swash plate surface rotating integrally with the shaft 5. The other side of the slipper 7 has a spherical shape, and the spherical portion 11a of the plunger 11
And ball joint configuration. The slipper 7 is provided with a central communication hole 7a for supplying lubricating oil from the swash plate surface 5a to the sliding portion on the spherical surface side. The swing plate motion transmitted from the swash plate surface is configured so that the plunger 11 that slides in the cylinder bore 9a of the cylinder block 9 only reciprocates.

In the cylinder block 9, a pump chamber 13 is formed between the plurality of cylinder bores 9a and the plunger 11. A suction space 15 communicating with each plunger is provided at the center of the cylinder block 9 so as to supply fuel to the pump chamber 13. In order to guide the fuel into the space 15, a fuel pipe outside the pump is attached to a rear body 17 made of aluminum die-casting with high productivity and considering the weight reduction. A filter 21 for preventing foreign matter from entering the apparatus is fixed. The fuel sent from the low-pressure pump 100 passes through the suction passage 19 and connects the suction chamber 23 in the center of the rear body 17 to the suction space 15 provided in the cylinder block 9. In the plunger 11, a suction valve for sucking fuel is formed by a ball 25, a spring 27, and a stopper 28 supporting the spring. The stopper 27 is also used to support the spring force of the plunger spring 30 inserted for the purpose of causing the plunger itself to follow the slipper and the swash plate. Fuel supply to the plunger suction valve configured as described above is performed from the suction space 15 of the cylinder block 9 through the A passage 31 oblique from the cylinder side.
The suction space 33 is formed in the cylinder block 9 so that the B communication passage 11b provided in the plunger 9 always communicates with the A passage 31 while reciprocating.

When the fuel supplied to the pump chamber 13 provided in the plunger 11 during the suction stroke moves to a discharge stroke (a stroke in which the space of the pump chamber 13 is reduced), the fuel is provided in the cylinder block 9. Spring stopper 3 supporting ball 35, spring 36 and spring 36
A discharge valve constituted by 7 is opened when the discharge chamber 39 formed in the rear body 17 reaches a specified pressure, and discharges fuel from the pump chamber. Here, the suction chamber 23 and the discharge chamber 39 provided in the rear body 17 are provided.
Is divided by the O-ring 41, and at the same time, the suction chamber 23 is provided on the center side of the discharge chamber 39 to make the passage configuration of the pump itself compact.

In the above description, the pressure inside the discharge chamber of the rear body 17 can be controlled to an optimum pressure by a pressure regulating valve (pressure regulator: P / Reg) 102 provided on the discharge side. The purpose of controlling the discharge pressure is to control the additional pressure applied to the injector 104 downstream on the discharge side. The high-pressure side fuel communicated from the discharge chamber 39 of the rear body 17 to the P / Reg 102 has a P / R
A passage B communicating with the suction chamber through a ball valve provided in the eg is provided in the rear body.

In this manner, the pressure in the pump chamber 13 is also changed to the fuel suction pressure (generally 0.2 MPa to 0.7 MPa).
To the pressure of the discharge chamber 39 (generally 3MPa to 20MPa).
a). In order to secure the pressure in the discharge chamber 39 and discharge a prescribed flow rate, the diameter gap between the plunger 11 and the cylinder bore 9 is set to 3 μm to 7 μm, and the seal length between the plunger 11 and the cylinder bore 9 a is ensured to be 5 mm or more. . In order to support the load generated by the pressure in the pump chamber 13 and achieve smooth rotation, a radial bearing 43 and a thrust bearing 45 are fitted to the shaft 5 so that the body 47 supports the load. .

The portions supporting these loads, that is, the slipper, the swash plate surface, and the bearing portion (referred to as a drive portion) are portions that support the relative speed and load due to rotation. A reduction in driving force due to wear loss can be prevented. Although it is necessary to supply lubricating oil to the drive unit, the lubricating oil is connected to the engine-side oil supply unit on the body 47 in order to use the lubricating oil on the engine side, and between the body 47 and the cylinder block 9. Swash plate chamber 5 to be formed
0 is provided with an oil supply path 52. The oil supply passage 52 has a throttle portion 5 for adjusting the amount of oil supplied from the engine.
2a was provided. However, the hole diameter of the constricted portion 52a is set to a hole having a diameter of 1 mm or more so as not to be closed by a foreign substance or the like from the engine side.

However, if only the oil supply path 52 is used, the oil supply from the supply hole stops when the swash plate chamber 50 is filled with the oil, and the oil is likely to deteriorate. For this reason, it is necessary to provide an oil return passage from the swash plate chamber 50 to the engine separately from the supply passage and to circulate the oil.

In the present embodiment, the gap between the balls of the radial bearing 43 and the radial bearing are of an open type on one side, and the return flow is reduced by the gap between the seal portions.

Further, in order to separate the fuel in the suction space 33 into the plunger and the oil in the swash plate chamber 50 between the plunger and the cylinder block, the respective plungers 9 and the end faces of the respective cylinder blocks 9 on the slipper side. And a reciprocating seal 55 for sealing fuel and oil during reciprocating movement.

FIG. 2 is a detailed structural view of the cylinder block and the plunger fitting portion of the reciprocating seal.

The reciprocating seal 55 forms a seal between the plunger 11 and the suction space 33 communicating from the center of the cylinder block as described above. For this,
A first lip 57 for sealing the suction pressure fuel, a second lip 58 for sealing the oil, and a metal ring 56 for pressing and fixing the reciprocating seal into the fitting hole 9b of the cylinder block.
A third lip 59 for preventing fuel from leaking from the metal ring 56 and the fitting hole 9b of the cylinder block is provided in the longitudinal direction, and the reciprocating seal is sealed at an end face of the fitting hole of the cylinder block into which the reciprocating seal is pressed. It is configured.

Since the first lip 57 seals the fuel at the suction pressure, the reciprocating seal 55 has a projection 60 between the first lip 57 and the second lip 58 for preventing deformation due to pressure. Further, the metal ring 56 of the reciprocating seal 55 extends to the inner diameter side between the first lip 57 and the second lip 58. The reciprocating seal 55 is made of a rubber material and causes an increase in volume due to swelling of fuel. If the gap 62 between the inner diameter including the inner diameter portion 56 'of the metal ring and the inner diameter including the rubber thickness on the inner diameter side and the outer diameter portion of the plunger is not provided, the surface pressure of this portion increases due to swelling. .

Therefore, the protrusion 60 is not provided immediately below the metal ring 56 'but is provided at a shifted position (L0> 0).
Further, the protrusion 60 is provided on the first lip side (L) in order to reduce the deformation of the first lip portion due to the suction side pressure.
2> L1). In particular, in this embodiment, the distance L2 from the second lip to the projection is set to be equal to or longer than the plunger stroke of the pump.

Further, since the slipper side of the second lip has a structure in which oil is stored so that the lubricating oil of the engine can circulate, the stored oil contains foreign substances such as soot. When the foreign matter enters the first lip, which is the fuel-side lip of the reciprocating seal 55, and the protrusion, the wear resistance due to the low pressure characteristic of the fuel and the surface pressure due to the fuel pressure is reduced.

For this reason, the swash plate chamber pressure P2 is set to a value lower than the fuel-side pressure P1, so that oil-side foreign matters are less likely to enter the fuel. Further, as shown in FIG. 3, a configuration including a plurality of lips 58 & 58 'is also conceivable in order to improve the performance of foreign matter prevention of the second lip for sealing oil.

As described above, by employing a structure in which oil and fuel are separated by the reciprocating part, it becomes possible to lubricate the swash plate chamber with oil. By adopting a structure in which oil is always stored in the swash plate, a rolling bearing can be used as the bearing for supporting the load. In particular, the structure is such that the thrust bearing can be made into a rolling bearing, the driving torque can be reduced, and the reliability of the sliding portion can be improved.

FIG. 4 shows a fuel system diagram when the high-pressure pump of the present invention is used. By setting the reciprocating seal portion to the suction pressure, the high pressure pump shown in FIG. 5 and the formation of the communication path 200 for maintaining the tank pressure to the fuel tank are not required, and the high pressure pump attached to the engine portion of the vehicle becomes unnecessary. A fuel system that does not require a long return pipe to the fuel tank can be configured.

[0028]

According to the present invention, the sealing of the high-pressure fuel pump is improved and the life of the sealing member can be extended, so that a highly reliable high-fuel pump can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal section of a first embodiment of the present invention.

FIG. 2 is a detailed view of a reciprocating seal portion.

FIG. 3 is an alternative view of a reciprocating seal.

FIG. 4 is a fuel system diagram using the pump of the present invention.

FIG. 5 is a conventional fuel system diagram.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Coupling, 3 ... Pin, 5 ... Shaft, 5a ... Swash plate surface, 7 ... Slipper, 7a ... Slipper center hole, 9 ... Cylinder block, 11 ... Plunger, 13 ... Pump chamber, 1
5 suction chamber, 17 rear body, 19 suction passage, 21
... Filter, 25 ... Ball for suction valve, 27,36 ...
Spring, 28, 37 stopper, 30 plunger spring, 33 suction space, 35 discharge valve ball, 39 discharge chamber, 41 O-ring, 43 radial bearing, 45 thrust bearing, 47 body 50 ... Swash plate chamber, 52 ... Oil supply path, 55 ... Reciprocating seal, 56 ...
Metal ring, 57: first lip, 58: second lip, 60 ...
Projection, 100: low pressure pump, 102: high pressure regulating valve,
104: injector, 200: fuel tank return passage.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // F02M 59/04 F04B 21/04 B (72) Inventor Minoru Hashida Minoru 2520, Oaza Takaba, Hitachinaka City, Ibaraki Prefecture Hitachi, Ltd. Automotive Equipment Group (72) Inventor Yoshinobu Ono 2520 Ojitakaba, Hitachinaka-shi, Ibaraki Prefecture Hitachi, Ltd. Automotive Equipment Group (72) Inventor Riyoshi Kotaki, Osaka, Ibaraki 2520 Hitachi, Ltd. Automotive Equipment Group (72) Inventor Takeshi Yamamura 2520 Oji Takaba, Hitachinaka City, Ibaraki Prefecture F-term, Hitachi Automotive Equipment Group F-term (reference) 3G066 AB02 AD02 AD12 BA36 CA34 CD10 CE03 3H070 AA01 BB04 BB07 CC29 DD96 3H071 AA03 BB01 CC28 DD01 DD53

Claims (9)

[Claims] 1. A high-pressure fuel pump, comprising: a reciprocating plunger; and a cylinder in which the plunger slides, wherein a pressurized chamber having a variable volume is formed in the cylinder by the reciprocating movement of the plunger. A fuel supply passage communicating between a hole opened on the outer periphery of the plunger and a hole opened on the pressure chamber side end of the plunger; and a valve mechanism for opening the fuel supply passage while the plunger is pulled out of the cylinder. A high-pressure fuel pump in which a seal member is provided between the plunger and the cylinder on the side opposite to the pressurizing chamber from the position of the hole provided on the outer periphery. 2. The reciprocating direction of the plunger, comprising: a plunger reciprocating in synchronization with the rotation of the engine; and a reciprocating high-pressure fuel pump having a cylinder between the plunger and the cylinder, the plunger sliding on the plunger. A seal member having a first lip and a second lip formed at an interval from each other, and a fuel is supplied to the pump chamber outside the first lip located on the pump chamber side formed by the plunger and the cylinder. A high-pressure fuel pump characterized in that a fuel suction side passage portion for introducing the fuel is formed. 3. The high-pressure fuel pump according to claim 1, wherein
Each lip of the seal member is fixed to a metal ring,
The high-pressure fuel pump is characterized in that the metal ring is fitted and held in the inner periphery of a hole formed in a cylinder block around the plunger. 4. A high-pressure fuel pump according to claim 2, wherein said seal member has an annular third lip which is in close contact with an inlet opening end surface of said cylinder. 5. The high-pressure fuel pump according to claim 1, wherein an end surface of said plunger on the insertion side of said plunger into said cylinder is formed as a curved surface. 6. The high pressure fuel pump according to claim 1, wherein
The high-pressure fuel pump according to claim 1, wherein the member is integrally provided with a protrusion protruding toward the outer peripheral surface of the plunger between the first lip and the second lip. 7. The high-pressure fuel pump according to claim 6, wherein said projection is provided on a first lip side from a center between said first lip and said second lip. 8. The high-pressure fuel pump according to claim 6, wherein the seal member is made of a rubber material attached to the metal ring so that the first lip and the second lip are located before and after the metal ring. The high-pressure fuel pump according to claim 1, wherein the protrusion is provided on the rubber material on a side closer to the first lip than the metal ring. 9. A high-pressure fuel pump for pressurizing fuel sent from a fuel tank and sending it to an injection valve, wherein the fuel tank and the high-pressure pump are connected only by a fuel supply passage. .