JPH04353262A - Fuel injection device - Google Patents

Abstract

PURPOSE:To provide a fuel injection device that reduces fuel leak through an opening between a plunger and a cylinder inner peripheral wall and restrains the dilution of internal combustion engine lubrication oil with fuel and prevents the lowering of internal combustion engine reliability. CONSTITUTION:A plunger 4 that slides in reciprocation at a cylinder 3 inner peripheral wall surface in responsive motion to a cam shaft 9, is provided, and a pump chamber 12 is formed of a plunger end surface 4a and the cylinder 3 inner peripheral wall surface. The pump chamber 12 is connected to a low pressure fuel passage 39 through the seat portion 28 of an injection time control solenoid valve 20 and at the same time communicates with a high pressure injection pipe 18 through a discharge valve 16. An annular leak fuel recovery groove 42 is formed at the inner peripheral wall of the cylinder 3 into which the plunger 4 is inserted, and the groove 42 and the passage 39 are connected to each other by means of a leak passage 44. An annular seal member 40 is provided at a cylinder 3 inner peripheral wall passage surface on the cam chamber 11 side of the leak fuel recovery groove 42, and the member 40 is brought into contact with the outer peripheral surface of the plunger 4 liquid-tightly.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device that pumps a measured amount of fuel by reciprocating a plunger without rotating it to an internal combustion engine such as a gasoline engine or a diesel engine.

0002

[Prior Art] Conventionally, as a fuel injection device in which fuel is metered by opening and closing a solenoid valve, the Japanese Unexamined Patent Publication No.
There is one disclosed in Japanese Patent No.-161136. According to this fuel injection device, when the injection timing control solenoid valve is energized, the valve member seats on the valve seat and the fuel return passage is cut off, thereby pressurizing the fuel in the pump chamber as the plunger rises. When the pressure of the pressurized fuel reaches a predetermined value or higher, the discharge valve is opened and fuel is injected from the high-pressure injection pipe.

0003

However, according to such a conventional fuel injection device, when the pump chamber is pressurized during fuel injection, fuel flows into the cam from the gap between the outer peripheral surface of the plunger and the inner peripheral wall of the cylinder. This leaked fuel mixes with the lubricating oil for the internal combustion engine. Therefore, since the lubricating oil for the internal combustion engine is diluted by the fuel having a lower viscosity than the lubricating oil, there is a problem that lubrication, cooling, etc. of various parts of the internal combustion engine by the lubricating oil are insufficient and the reliability of the engine is reduced. The present invention was made to solve these problems, and it reduces the leakage of fuel from the gap between the plunger of the fuel injection device and the inner peripheral wall of the cylinder, and reduces the dilution of lubricating oil for internal combustion engines by fuel. It is an object of the present invention to provide a fuel injection device which suppresses deterioration in reliability of an internal combustion engine.

0004

[Means for Solving the Problems] A fuel injection device according to the present invention for solving the above-mentioned problems includes a camshaft rotated by the driving force of an internal combustion engine, and a cylinder inner peripheral wall surface that is rotated in response to the rotation of the camshaft. a plunger that slides back and forth; a pump chamber formed by the end face of the plunger and an inner peripheral wall surface of the cylinder; an injection timing control valve that opens and closes a passage connecting the pump chamber and a low-pressure side fuel passage; A discharge valve that discharges pressurized fuel to a high-pressure side fuel passage when the pressure of the fuel exceeds a predetermined value, an annular leak fuel recovery groove formed in the inner circumferential wall of the cylinder, and the leak fuel recovery groove. and the low-pressure side fuel passage, and an annular seal member fixed to the cylinder and in liquid-tight contact with the outer peripheral surface of the plunger.

[0005]

[Operation] According to the fuel injection device of the present invention, fuel that attempts to leak from between the plunger and the cylinder inner circumferential wall is collected in the leak fuel recovery groove, and is also transferred to the low pressure side through the leak passage using the pressure difference. It is actively collected in the fuel passage. At the same time, the annular seal member prevents fuel from leaking toward the camshaft. Therefore, since dilution of the lubricating oil for the internal combustion engine by leaked fuel is reduced, the lubrication of the internal combustion engine is not impaired, a decrease in the reliability of the internal combustion engine is prevented, and the life of the lubricating oil is extended.

[0006]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. A first embodiment of the present invention applied to a fuel injection device for a diesel engine is shown in FIG. The injection pump 1 is of a row type, and a pump housing 2 is provided with cylinders 3 in a number corresponding to the number of cylinders of a diesel engine.
A plunger 4 is slidably inserted therein. The lower end of the plunger 4 is engaged with a tappet 7 that is urged downward by a spring 6 against the lower end 3a of the cylinder, and the tappet 7 contacts a cam 10 of a camshaft 9 via a roller 8. The camshaft 9 provided in the cam chamber 11 is
It is connected to the crankshaft of a diesel engine (not shown) and is rotationally driven. A pump chamber 12 is defined above the plunger 4 by the plunger end surface 4a and the inner circumferential wall of the cylinder 3. The pump chamber 12 communicates with a discharge port 14 formed in the cylinder 3, and a ball 16 serving as a discharge valve is interposed in the discharge port 14 and urged by a spring 15 in the direction of closing the discharge port. Discharge port 1
4 communicates with the high pressure injection pipe 18 through the ball 16.

[0007] An injection timing control solenoid valve 20 is assembled in the upper part of the pump housing 2. A valve member 26 is slidably inserted into a valve body 24 fixed to a solenoid valve housing 22 of an injection timing control solenoid valve 20, and a seat portion 28 is formed at the tip of this valve member 26. Valve member 26
The armature 30 fixed to is biased downward by a spring 31, and when the coil 32 is energized, it is attracted to the iron core 33 by electromagnetic attraction force. The valve port 24a connecting the pump chamber 12 and the low-pressure fuel passage 39 is opened and closed by moving the seat portion 28 into and out of the valve port 24a. A fuel pump 38 that pumps fuel into the pump chamber 12 is interposed in the low-pressure fuel passage 39 .

An annular groove 3b is formed in the cylinder 3 that slidably accommodates the plunger 4, and an annular seal member 40 is provided in the annular groove 3b so as to be in constant contact with the outer periphery of the plunger 4. An annular leak fuel recovery groove 42 is formed in the inner peripheral wall of the cylinder of the annular seal member 40 on the injection timing control solenoid valve 20 side.
is connected to. A clearance of several μm is formed between the cylinder 3 and the plunger 4 for good sliding and prevention of seizure. The injection timing control solenoid valve 20 controls the injection timing by energizing and stopping the coil 32 in response to a command from a control unit (ECU), not shown. That is, a control unit (ECU, not shown) calculates the pressure of a common rail, not shown, as the injection timing,
The coil 32 is energized at the timing to realize this injection timing.

Next, the operation will be explained. fuel tank 3
The fuel pumped from 6 by the fuel pump 38 is
When the seat portion 28 is open, the pump chamber 12 is filled with fuel from the low-pressure fuel passage 39 passing around the seat portion 28 . As the camshaft 9 rotates, the plunger 4 rises via the tappet 7 and the roller 8 that contacts the cam 10, and the fuel in the pump chamber 12 is returned to the low pressure fuel passage 39 from the valve port 24a. Next, when the armature 30 and the valve member 26 are attracted to the iron core 33 against the spring 31 by energizing the coil 32, the seat portion 28 is seated in the valve port 24a, so that the fuel in the pump chamber 12 is discharged. will be stopped. The fuel in the pump chamber 12 is pressurized to high pressure as the plunger 4 rises, and when the pressure of this fuel exceeds the set pressure of the spring 15, the fuel pushes open the ball 16 and is injected from the high pressure injection pipe 18.

A part of the fuel pressurized in the pump chamber 12 is
Although the fuel tends to leak from the clearance between the cylinder 3 and the plunger 4, this leaked fuel is returned to the low pressure fuel passage 39 from the leak fuel recovery groove 42 through the leak passage 44. The remaining leaked fuel descends to the annular seal member 40 along the inner circumferential wall of the cylinder. However, when the annular seal member 40 is applied to the plunger 4 with an appropriate contact pressure,
, the leakage fuel is prevented from passing to the cam chamber 11 side. Further, as the plunger 4 reciprocates, the contact portion of the annular seal member 40 scrapes up leaked fuel, so the amount of adhesion leakage caused by fuel adhering to the plunger 4 is also reduced.

Therefore, when the camshaft 9 is driven by the crankshaft of a diesel engine (not shown), the lubricating oil in the cam chamber 11 is hardly diluted by the fuel in the pump chamber 12, and the lubricating oil maintains good lubricity and Cooling performance is ensured. Furthermore, although the lubricating oil in the cam chamber 11 may be scraped up and come into contact with the lower part of the plunger 4, it is sealed at the contact portion of the seal member 40, so that it will not mix with the fuel in the pump chamber 12. do not have. Therefore, there is no adverse effect such as generation of white smoke in the exhaust gas due to lubricating oil mixed into the fuel of the diesel engine.

A second embodiment of the invention is shown in FIG. The second embodiment is similar to the first leak fuel recovery groove 42 of the first embodiment.
A second leak fuel recovery groove 5 is provided between the
This is an example in which 0 is formed. The second leak fuel recovery groove 50 communicates with the fuel tank 36 through a second leak passage 51 . In this embodiment, the leak fuel whose pressure has been reduced to the intake fuel pressure in the first leak fuel recovery groove 42 is further reduced to atmospheric pressure in the second leak groove 50 which is open to atmospheric pressure. As a result, the leakage fuel and the seal member 40
Since there is no pressure difference with the atmospheric pressure part below, fuel leak to the cam chamber 11 side due to the pressure difference is effectively prevented. Furthermore, since the required pressure for sealing by the seal member 40 is reduced, the sealing effect is improved, and the contact pressure with the plunger 4 can be reduced, so that the amount of wear of the seal member 40 can be reduced. can. Note that other constituent parts of this second embodiment are the same as those of the first embodiment, so substantially the same constituent parts are given the same reference numerals and explanations will be omitted. The same applies to the following examples.

A third embodiment of the present invention is shown in FIG. In the third embodiment, a leak fuel recovery groove 50 is communicated with a fuel tank 36 through a leak passage 51. In this embodiment as well, when the plunger 4 rises, the fuel in the pump chamber 12 is pressurized, and this pressurized fuel tries to leak from the clearance between the plunger 4 and the cylinder 3. The leak fuel is collected in the leak fuel collection groove 50 and returned to the fuel tank 36 through the leak passage 51 which is released to atmospheric pressure. Further, since the sealing member 40 improves the sealing performance with the outer circumferential surface of the plunger 4, leakage of leakage fuel into the cam chamber 11 is suppressed.

A fourth embodiment of the present invention is shown in FIG. The fourth embodiment uses a spill control solenoid valve, and is an example in which fuel pumped up from a fuel tank 36 by a fuel pump 38 is directly forced into the pump chamber 12. The leak fuel recovery groove 42 formed in the inner circumferential wall of the cylinder communicates with the low pressure fuel passage 54 through a leak passage 55 . The pump chamber 12 also communicates with the fuel tank 36 through a fuel return passage 60 through the periphery of the seat portion 58 of the injection timing control solenoid valve 20 . This injection timing control solenoid valve 20 is a spill control valve, and when the coil 32 is energized, the armature 30 and the valve member 2
6 is attracted by the iron core 33 to open the seat portion 58. That is, unlike the first embodiment, when energized,
The valve is configured to open. In this fourth embodiment, the clearance between the plunger 4 and the inner circumferential wall of the cylinder 3 is such that the fuel is transported from the leak fuel recovery groove 42 to the leak passage 55.
The fuel is then collected into the low-pressure fuel passage 54 on the low-pressure side. Further, since the outer periphery of the plunger 4 is sealed by the seal member 40, leakage of leak fuel into the cam chamber 11 is suppressed.

Next, FIG. 5 shows the specific structure of the sealing member that seals the clearance between the cylinder and the plunger.
and shown in FIG. The sealing member according to the fifth embodiment shown in FIG. This is an example in which a first mechanical seal 64 and a second mechanical seal 65 are inserted. The two annular mechanical seals further improve sealing performance. The seal member according to the sixth embodiment shown in FIG. 6 is an example in which an annular groove 66 located on the outer periphery of the plunger 4 is formed in the lower end 3c of the cylinder 3, and an annular mechanical seal 68 is inserted into the annular groove 66. The mechanical seal 68 is fixed to the annular groove 66 by a fixing plate 70 fixed to the lower surface 3b of the cylinder 3.

Next, a fixing means for fixing the seal member to the cylinder 3 is shown in FIGS. 7 and 8. The seal fixing means according to the seventh embodiment shown in FIG. 7 is an example in which a press-fitting member 72 is used. The assembly procedure is to insert the seal member 40 into the annular press-fit member 72.
The press-fitting member 72 and sealing member 40 are fitted into the annular groove 66 and fixed with a push plate 73. Further, the seal fixing means according to the eighth embodiment shown in FIG. 8 is an example in which the seal member 40 is inserted into the annular groove 66, the C ring 74 is fitted into the annular groove 76, and the seal member 40 is fixed to the annular groove 66. .

[0017]

As explained above, according to the fuel injection device of the present invention, there is a leak recovery groove that releases fuel leakage from the clearance between the outer circumference of the plunger and the inner circumferential wall of the cylinder to the low pressure side by utilizing the pressure difference. In addition, an annular seal member that is always in contact with the outer periphery of the plunger is provided, which prevents leaked fuel from being mixed with the lubricating oil of the internal combustion engine, so that the lubricating and cooling properties of the lubricating oil of the internal combustion engine are not impaired and the internal combustion engine is maintained. This has the effect of increasing reliability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a fuel injection device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a fuel injection device according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a fuel injection device according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing a fuel injection device according to a fourth embodiment of the present invention.

FIG. 5 is a partial sectional view showing a seal member according to a fifth embodiment of the present invention.

FIG. 6 is a partial sectional view showing a sealing member according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view showing seal member fixing means according to a seventh embodiment of the present invention.

FIG. 8 is a sectional view showing a seal member fixing means according to an eighth embodiment of the present invention.

[Explanation of symbols]

3 Cylinder 4 Plunger 4a Plunger end face 9 Camshaft 12 Pump chamber 16 Ball (discharge valve) 18 High pressure injection pipe (high pressure side fuel passage) 20
Solenoid valve for injection timing control (injection timing control valve) 24a
Valve port (passage) 39 Low pressure fuel passage (low pressure side fuel passage) 40
Annular seal member 42 Leak fuel recovery groove 44 Leak passage

Claims (1)

[Claims] Claim 1: A camshaft rotated by the driving force of an internal combustion engine, a plunger that slides back and forth on the inner circumferential wall surface of a cylinder in response to the rotation of the camshaft, and an end surface of the plunger and the inner circumferential wall surface of the cylinder. an injection timing control valve that opens and closes a passage connecting this pump chamber and a low-pressure side fuel passage; a discharge valve that discharges to the side fuel passage; an annular leak fuel recovery groove formed in the inner circumferential wall of the cylinder; a leak passage that connects the leak fuel recovery groove and the low pressure side fuel passage; fixed to the cylinder; A fuel injection device comprising: an annular seal member that is in liquid-tight contact with the outer peripheral surface of the plunger.