JPH10184494A - Fuel booster pump for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability of a seal member to seal a plunger and to increase a lubricant pressure at an engine low speed area so as to operate a variable valve gear normally. SOLUTION: A pump part 1A for fuel consists of a plunger 6 reciprocating in a cylinder 3 and feeds high pressure fuel to a fuel injection valve 15. To prevent a leakage of fuel, the plunger 6 is sealed with a seal member 18. By reciprocating a piston part 22 formed integrally with the plunger 6 in a back pressure chamber 23, an auxiliary pump part 1B for lubricant is constituted. Lubricant discharged from an oil pump 29 is further pressurized and fed to a hydraulic actuator 32 for a variable valve gear. Since the back pressure chamber 23 is filled with lubricant having a pressure higher than the atmospheric pressure, a pressure difference exerted on the seal member 18 is reduced and even when the fuel leaks, the feel is prevented from residing in the back pressure chamber 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in a fuel pressurizing pump for pressurizing a fuel such as gasoline supplied to an internal combustion engine to a relatively high pressure.

[0002]

2. Description of the Related Art For example, in recent years, in order to realize lean combustion in a gasoline engine, various direct injection type spark ignition type internal combustion engines in which fuel is directly injected into a cylinder in a compression stroke or the like have been proposed. In such a direct injection type internal combustion engine, it is necessary to pressurize the fuel supplied to the fuel injection valve to a sufficiently high pressure, for example, about 10 MPa.

In order to obtain such a high pressure,
Generally, a reciprocating fuel pressurizing pump in which a pump working chamber is defined at a cylinder end by a cylindrical plunger is used, for example, a pump provided coaxially with a cam shaft for an intake / exhaust valve of an engine. The driving cam reciprocates the plunger (see, for example, JP-A-8-14140, JP-A-8-68370).

[0004]

In such a plunger-type fuel pressurizing pump, the fuel pressure in the pump working chamber becomes extremely high as described above, so that the inside of the slidably fitted cylinder is required. Leakage of fuel through a small clearance between the peripheral surface and the outer peripheral surface of the plunger is a very serious problem. In order to prevent the fuel from leaking, in the apparatus disclosed in Japanese Patent Application Laid-Open No. 8-68370, a rubber cap-shaped sealing member is provided to seal the reciprocating plunger.

[0005] However, even if some kind of seal member is provided in order to prevent the leakage of fuel from the pump working chamber, the area on the low pressure side, that is, the area opposite to the pump working chamber, which is partitioned by this seal member, is always atmospheric. Therefore, there is a problem that the pressure difference from the fuel pressure in the pump working chamber is large and the seal member is quickly deteriorated. Further, if the fuel leaks due to deterioration of the sealing member, if the fuel stays in the back pressure chamber containing the return spring, for example, corrosion occurs in various parts of the back pressure chamber, and the lubrication performance is reduced. It is not preferable because it deteriorates.

On the other hand, an internal combustion engine is provided with a mechanically driven oil pump such as a gear pump in order to pump lubricating oil to various parts of the engine as is well known. Since the engine is driven in conjunction with the engine crankshaft, it is difficult to secure a sufficient oil pressure in a region where the engine speed is low. Therefore, for example, when a variable valve mechanism that variably controls the valve lift characteristic with some hydraulic mechanism is provided, the hydraulic pressure tends to be insufficient at the time of low-speed rotation immediately after starting or at the time of idling, and the normal There is also a problem that a proper operation cannot be secured.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a cylinder, a plunger which is slidably fitted to the cylinder, and defines a pump working chamber at one end of the cylinder. A fuel pressurizing pump for an internal combustion engine comprising: a suction-side check valve and a discharge-side check valve provided in a connected fuel suction passage and a fuel discharge passage, respectively; and a cam for driving the plunger. A seal structure for sealing between the plunger and the inner periphery of the cylinder is provided, and a back pressure chamber is defined on the opposite side of the seal structure from the pump working chamber. The pump is configured to introduce a fluid having a pressure lower than the discharge pressure in the pump working chamber and higher than the atmospheric pressure.

[0008] In a further specific aspect of the invention, an oil pump of an internal combustion engine is used as the external fluid pump, and lubricating oil pressurized by the oil pump is introduced into the back pressure chamber. You.

That is, the plunger that slides back and forth with respect to the cylinder is sealed by the seal structure, thereby preventing fuel leakage. By holding the fluid such as lubricating oil appropriately pressurized in the back pressure chamber, the pressure difference borne by the seal structure is reduced, and the sealing performance is ensured. Since the pressure difference between the front and rear of the seal structure is small, the amount of leakage can be sufficiently suppressed even with a mechanical seal or the like.

According to the invention of claim 3, an oil outlet passage is connected to the back pressure chamber, so that the lubricating oil introduced by the oil pump is constantly circulated.

Accordingly, even if the fuel leaks from the pump working chamber through the seal member, the fuel does not stay in the back pressure chamber.

Further, according to the present invention, a large-diameter piston portion provided at one end of the plunger is slidably fitted to an auxiliary cylinder provided coaxially with the cylinder, and the back pressure chamber is formed. A check valve is provided in each of the oil suction passage and the oil discharge passage connected to the back pressure chamber, and with the reciprocation of the plunger,
It constitutes an auxiliary pump for pressurizing the introduced lubricating oil.

That is, in the structure of the fourth aspect, the auxiliary pump for pressurizing the lubricating oil is formed integrally with the pump mechanism for pressurizing the fuel. The fuel is pressurized, and the lubricating oil is pressurized on the other back pressure chamber side. Therefore, the hydraulic pressure increased by the oil pump is further increased by the auxiliary pump.

A fifth aspect of the present invention further embodies the fourth aspect.
In the invention, a bypass passage is provided between the oil suction passage and the oil discharge passage, and a bypass valve that opens when the pressure on the upstream side of the oil suction passage becomes equal to or higher than a set pressure is provided in the bypass passage. Is equipped.

Therefore, when the engine speed is low and the pressure of the lubricating oil pumped from the oil pump to the oil suction passage is lower than the set pressure, the bypass valve is closed, and the lubricating oil is supplied to the auxiliary pump. And is pressurized by the reciprocating motion of the plunger. This ensures a sufficiently high oil pressure. When the engine speed increases and the pressure of the lubricating oil pumped from the oil pump toward the oil suction passage reaches a set pressure, the bypass valve opens. As a result, the lubricating oil is supplied to the downstream side without passing through the back pressure chamber serving as the auxiliary pump. That is, the pumping action of the auxiliary pump is substantially stopped, and an increase in power loss is avoided.

Further, in the invention according to claim 6, a return spring for urging the plunger toward the cam is housed in the back pressure chamber. That is, the back pressure chamber into which a fluid such as lubricating oil is introduced also serves as a storage space for the return spring.

[0017]

As described above, according to the fuel pressurizing pump according to the first aspect, the pressure difference acting on the seal structure can be reduced, so that the sealing action is further ensured, and the pressure from the pump working chamber is reduced. Fuel leakage can be reliably prevented, and the durability of the seal structure is improved.

In particular, if the lubricating oil is introduced by using an oil pump as in the second aspect, the structure can be simplified without an extra increase in the number of parts.

According to the third aspect of the present invention, even if the fuel leaks into the back pressure chamber through the seal structure, the fuel is discharged to the outside by the circulating lubricating oil, so that the fuel may stay in the back pressure chamber. Therefore, it is possible to prevent corrosion of each part due to fuel.

According to the fourth aspect of the present invention, the back pressure chamber is used as an auxiliary pump for pressurizing the lubricating oil.
Therefore, a sufficiently high oil pressure can be ensured even in a region where the engine speed is low, and for example, it is possible to correctly control the variable valve mechanism by the oil pressure.

If the bypass passage and the bypass valve are provided as in claim 5, the pumping action of the auxiliary pump is substantially stopped in the high-speed region of the engine, and an increase in power loss in the high-speed region can be prevented. .

Further, according to the present invention, it is possible to avoid an increase in the size of the entire pump.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a fuel pressurizing pump 1 according to the present invention.
1 shows an embodiment. In this fuel pressurizing pump, a fuel pump section 1A and an auxiliary pump section 1B for lubricating oil are integrally formed.
A cylindrical cylinder 3 constituting the fuel pump section 1A is formed in a shape in which one end is sealed, and the lubricating oil auxiliary pump section 1B is connected to the open other end of the cylinder 3. An auxiliary cylinder 4 to be constituted is formed.
The auxiliary cylinder 4 has a cylindrical shape larger in diameter than the cylinder 3 and is provided coaxially with the cylinder 3.
The end of the auxiliary cylinder 4 is open, and a cam 5 for driving the pump is arranged at a position facing the end.

The pump housing 2 is attached to, for example, a cylinder head of an internal combustion engine, and the cam 5 is formed integrally with a cam shaft for driving intake and exhaust valves. It is to be noted that the pump housing 2 is disposed at another portion, and a separate cam connected to the camshaft via a coupling or a separate cam linked to the engine crankshaft via a chain or the like is used as the cam 5. Of course, it is also possible. In this embodiment, the cam 5 has four cam ridges. In this case, the cam 5 and a structure for rotatably supporting the cam 5 are formed integrally with the fuel pressurizing pump 1.

A cylinder-shaped plunger 6 is slidably fitted in the cylinder 3, and a pump working chamber 7 is defined at the sealed end of the cylinder 3 by the plunger 6. ing. A fuel suction passage 8 and a fuel discharge passage 9 are connected to the pump operation chamber 7, and a suction-side check valve 10 and a discharge-side check valve 11 are interposed in the respective passages 8 and 9. Have been. The fuel suction passage 8 is connected to a discharge side of a fuel feed pump 13 driven by an electric motor 12, and is connected to the fuel tank 1.
Fuel such as gasoline is fed from 4 through a fuel filter (not shown). The fuel discharge passage 9 is connected to the electromagnetic fuel injection valve 15 of each cylinder via a high-pressure fuel pipe. The fuel injection valve 15 is configured to directly inject fuel into the cylinder.

A relief passage 16 is provided between the fuel discharge passage 9 downstream of the discharge check valve 11 and the fuel suction passage 8 upstream of the suction check valve 10. A pressure regulator 17 for appropriately adjusting the fuel discharge pressure (P1) is interposed in the passage 16. In this embodiment, a type in which the discharge pressure can be variably controlled by controlling the energization of the solenoid 17a is used as the pressure regulator 17, but is not limited to this.

The clearance between the outer peripheral surface of the plunger 6 and the inner peripheral surface of the cylinder 3 is set as small as possible to prevent fuel leakage. Further, at the open end side of the cylinder 3, that is, at the boundary between the auxiliary cylinder 4 and the cylinder 3, a seal member 18 that seals between the cylinder 3 and the outer peripheral surface of the plunger 6 is disposed as a seal structure. The seal member 18 is, for example, a packing-like member formed by combining a rubber seal lip and a metal retainer, and presses against and seals the outer peripheral surface of the plunger 6 that moves linearly. Note that a mechanical seal may be used as the seal structure. In this case, a labyrinth may be formed on the inner periphery of the cylinder 3 or the outer periphery of the plunger 6. In this embodiment, a low-pressure port 19 in the form of a groove is formed on the inner peripheral surface of the cylinder 3 over the entire circumference so as to separate the pump working chamber 7 and the seal member 18 from each other. The low-pressure port 19 and the upstream side of the suction-side check valve 10 of the fuel suction passage 8 are always in communication by a low-pressure passage 20. Thereby, the low-pressure port 19 is always maintained at a low pressure, preventing high pressure from acting on the seal member 18 and
Fuel that is about to leak through the fitting gap between the cylinder 3 and the plunger 6 is collected in the fuel suction passage 8 side.

At the end of the plunger 6 on the auxiliary cylinder 4 side, a bottomed cylindrical piston portion 22 having a larger diameter than the plunger 6 is integrally formed via a rod portion 21. The piston portion 22 has a diameter corresponding to the auxiliary cylinder 4 and is slidably fitted on the inner peripheral surface of the auxiliary cylinder 4. The back pressure chamber 23 is defined in the auxiliary cylinder 4 in a substantially sealed state by fitting the piston portion 22 to the auxiliary cylinder 4 in this manner. The end wall of the piston portion 22 also serves as a cam follower, and is in contact with the cam 5. Further, a return spring 24 composed of a coil spring that constantly urges the end wall of the piston portion 22 toward the cam 5 is housed in the back pressure chamber 23. Therefore, when the cam 5 rotates with the rotation of the engine, the plunger 6 reciprocates together with the piston portion 22 to pressurize the fuel sucked into the pump operating chamber 7 and supply it to the fuel injection valve 15.
The discharge pressure of this fuel is, for example, about 7 to 10 MPa.

The lubricating oil auxiliary pump portion 1B is mainly composed of the back pressure chamber 23, and an oil supply passage 25 and an oil discharge passage 26 are connected to the back pressure chamber 23. In addition, an oil suction side check valve 27 and an oil discharge side check valve 28 are interposed in the respective passages 25 and 26 in order to realize a pump function. The oil supply passage 25 is connected to a discharge side of a lubrication oil pump 29 of the internal combustion engine via a main oil gallery 30. This oil pump 29
Is composed of, for example, a gear pump driven by an engine crankshaft, sucks up lubricating oil stored in an oil pan 31 of the engine, and sends it to the main oil gallery 30 by pressure. The lubricating oil pressurized by the oil pump 29 is supplied from the main oil gallery 30 to each part such as the main bearing part, and a part of the lubricating oil is introduced into the back pressure chamber 23 through the oil supply passage 25. It has become. A downstream side of the oil discharge passage 26 serving as an oil outlet passage is connected to a hydraulic actuator 32 of a variable valve mechanism, and supplies a hydraulic pressure serving as a drive source. Although not shown in detail, the hydraulic actuator 32 includes, for example, an actuator unit such as a hydraulic cylinder or a hydraulic motor, and a control valve unit that switches a hydraulic supply path.

Between the upstream side of the check valve 27 of the oil supply passage 25 and the downstream side of the check valve 28 of the oil discharge passage 26, there is provided a bypass passage 33 for directly connecting the two. In the passage 33, the bypass passage 33
A bypass valve 34 that opens and closes is provided. The bypass valve 34 is a relief valve (a check valve) with a kind of pilot mechanism that opens when the hydraulic pressure (P4) on the upstream side, that is, on the discharge side of the oil pump 29 becomes higher than a set pressure.
As shown in FIG. 2, the main valve body 3 opens and closes the bypass passage 33 urged by the set spring 35 in the valve closing direction.
6 and a pilot piston which moves by the balance between the urging force of the pilot spring 37 and the discharge pressure (P4) of the oil pump 29, and pushes the main valve body 36 open when the discharge pressure (P4) of the oil pump 29 exceeds a set pressure. 38,
It is composed of 39 is a drain passage.

The lubricating oil auxiliary pump portion 1B configured as described above performs a pumping action by the reciprocating movement of the piston portion 22 integral with the plunger 6 with the rotation of the cam 5, and the oil pump 29 The discharged lubricating oil is further pressurized to provide a hydraulic actuator 3 for a variable valve mechanism.
Feed to 2. Since the lubricating oil auxiliary pump section 1B is a piston pump, a high pressure can be easily obtained. That is, the straight line a in FIG. 3 is the hydraulic characteristic of the oil pump 29 itself, and the straight line b is the hydraulic characteristic when the pressure is further increased by the auxiliary pump unit 1B for lubricating oil. Since the oil pressure rises along the straight line b, the hydraulic actuator 32 for the variable valve mechanism can be reliably operated, and the valve lift characteristics can be correctly controlled in accordance with the desired control characteristics. Then, the engine speed reaches a predetermined speed, and the discharge pressure (P
4) is equal to or higher than the set pressure, the bypass valve 34 (the main valve element 3)
6) is pushed open, and the lubricating oil discharged from the oil pump 29 does not pass through the back pressure chamber 23 and the hydraulic actuator 32
Will be supplied to That is, the hydraulic pressure P3 supplied to the hydraulic actuator 32 changes as shown by the solid line in FIG. As described above, at the stage where the bypass valve 34 is opened and the lubricating oil does not pass through the back pressure chamber 23, the lubricating oil auxiliary pump unit 1B does not substantially perform the pumping operation. Will be very small. Therefore, it is possible to avoid an increase in power loss in a high-speed range due to the addition of the auxiliary pump.

In the above configuration, the back pressure chamber 23 is always filled with lubricating oil having a pressure (P2) higher than the atmospheric pressure. Therefore, the pressure difference acting on the seal member 18 for sealing the pump working chamber 7 of the fuel pump section 1A becomes relatively small, so that the sealing performance is further ensured and the durability is improved. The bypass valve 34
When the valve is opened, the pumping action of the back pressure chamber 23 substantially stops, but even in this state, the pressure P2 in the back pressure chamber 23
Does not become lower than the discharge pressure (P4) of the oil pump 29, so that a sufficiently high pressure is applied to the seal member 18 as is apparent from FIG.

The lubricating oil present in the back pressure chamber 23 is of course at the stage when the bypass valve 34 is closed,
Even when the bypass valve 34 is opened, it circulates with the oil pan 31 as the piston portion 22 reciprocates.
Therefore, in the unlikely event that the fuel flows through the back pressure chamber 2 through the seal member 18,
Even if the fuel leaks to the third side, the fuel does not stay in the back pressure chamber 23. Therefore, the return spring 24 made of fuel is used.
Corrosion of each part is prevented.

In the above embodiment, the bypass valve 3
4 is configured to open and close mechanically by pressure, but may be configured to open and close the bypass passage 33 by a control signal from the outside. Further, in the above embodiment, the back pressure chamber 23 is configured as an auxiliary pump for lubricating oil. However, the oil suction side check valve 27 and the oil discharge side check valve 28 are removed, and the back pressure chamber 23 is simply provided. Even if the lubricating oil pressurized by the oil pump 29 is circulated, the durability of the seal member 18 can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view showing one embodiment of a fuel pressurizing pump according to the present invention.

FIG. 2 is a configuration explanatory view showing one embodiment of the bypass valve.

FIG. 3 is a characteristic diagram showing characteristics of hydraulic pressure supplied to a hydraulic actuator for a variable valve mechanism.

[Explanation of symbols]

 1A: fuel pump section 1B: lubricating oil auxiliary pump section 3 ... cylinder 4 ... auxiliary cylinder 6 ... plunger 7 ... pump operating chamber 18 ... seal member 23 ... back pressure chamber 29 ... oil pump 34 ... bypass valve

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI F04B 53/14 F04B 21/04 Z (72) Inventor Naoki Yamamoto 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd.

Claims (6)

[Claims] 1. A cylinder, a plunger fitted slidably in the cylinder and defining a pump working chamber at one end of the cylinder, a fuel intake passage and a fuel discharge passage connected to the pump working chamber. A fuel pressurizing pump for an internal combustion engine, comprising: a suction-side check valve and a discharge-side check valve respectively provided on the cylinder; and a cam for driving the plunger. And a back pressure chamber is defined on the side opposite to the pump working chamber with the sealing structure interposed therebetween, and the back pressure chamber is provided with a discharge pressure in the pump working chamber by an external fluid pump. A fuel pressurizing pump for an internal combustion engine, which is configured to introduce a fluid having a pressure lower than the atmospheric pressure and higher than the atmospheric pressure. 2. An internal combustion engine according to claim 1, wherein an oil pump of an internal combustion engine is used as said external fluid pump, and lubricating oil pressurized by said oil pump is introduced into said back pressure chamber. Engine fuel pressurization pump. 3. The fuel pressurizing pump for an internal combustion engine according to claim 2, wherein an oil outlet passage is connected to the back pressure chamber, and lubricating oil introduced by the oil pump circulates constantly. 4. A back pressure chamber is defined by a large-diameter piston portion provided at one end of the plunger slidably fitted to an auxiliary cylinder provided coaxially with the cylinder. A check valve is provided in each of the oil suction passage and the oil discharge passage connected to the back pressure chamber, and constitutes an auxiliary pump for pressurizing the introduced lubricating oil with the reciprocation of the plunger. Claim 2
A fuel pressurizing pump for an internal combustion engine according to claim 1. 5. A bypass passage is provided between the oil suction passage and the oil discharge passage.
5. The fuel pressurizing pump for an internal combustion engine according to claim 4, wherein a bypass valve that opens when the pressure on the upstream side of the oil suction passage becomes equal to or higher than a set pressure is interposed in the bypass passage. 6. The fuel for an internal combustion engine according to claim 1, wherein a return spring for urging the plunger toward the cam is housed in the back pressure chamber. Pressurizing pump.