JP2000227062A - High pressure fuel pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the pressure in an injection pipe at a fixed set pressure without executing return control in a high pressure fuel pump by enabling the stroke of the pressurizing part of a plunger to be adjusted. SOLUTION: One end of a cylinder 17 is sealed up with a cylinder cover 23, and a plunger chamber 57 is formed out of the bore of the cylinder 17, the cylinder cover 23, and one end face of a plunger. The plunger is constituted of a first plunger 25 and a second plunger 30, the first plunger 25 and the second plunger 30 are slidably engaged with each other, and a gas of fixed pressure is tightly enclosed in a sealed up space 28 between the first plunger 25 and the second plunger 30. The total length of the first plunger 25 and the second plunger 30 is limited not more than a fixed value, and by compression of the gas in the sealed up space 28, the total length of the first plunger 25 and the second plunger 30 can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-pressure fuel pump with a variable stroke of a plunger for supplying fuel to an injector of an engine.

[0002]

2. Description of the Related Art Conventional high-pressure fuel pumps (for example,
No. 146256), the fuel in the fuel tank is flowed into a plunger chamber (pump chamber) by a low-pressure pump, the fuel in the plunger chamber is pressurized by a reciprocating plunger, and injected through an injection pipe (delivery pipe). Is supplying high-pressure fuel. A plurality of injectors are connected to one high-pressure fuel pump via an injection pipe, and high-pressure fuel accumulated in the injection pipe is injected into the combustion chamber while the injector is open. The injection pipe is supplied with fuel from a high-pressure fuel pump to replenish consumed fuel, and is always maintained at a high fuel pressure.

In a high-pressure fuel pump, a solenoid valve is disposed in an inlet-side communication passage that connects a fuel introduction pipe and a plunger chamber, and the solenoid valve controls the pressurizing time of the plunger chamber. When the plunger is retracted, the solenoid valve is opened and fuel flows into the plunger chamber.In the initial stage of forward movement of the plunger, the solenoid valve remains open, and part of the fuel in the plunger chamber is returned through the solenoid valve. You. Next, when the solenoid valve is closed, the fuel pressure in the plunger chamber increases, and high-pressure fuel is supplied to the injector. Since the plunger stroke is constant at both low and high loads, the ECU
To control the valve closing timing (return amount) of the solenoid valve to set the fuel pressure of the injection pipe to a set pressure (for example, 1).
2MPa).

[0004]

In the conventional high-pressure fuel pump, the return control is performed with a constant stroke of the plunger. Therefore, the efficiency of the pump is low, and the pump device is complicated due to the presence of the solenoid valve and the return passage. Larger and more expensive. The present invention provides a high pressure fuel pump in which a stroke of a pressurizing portion of a plunger can be adjusted,
It is an object of the present invention to maintain the inside of an injection pipe at a predetermined set pressure without performing return control.

[0005]

According to the present invention, a cylinder is fixed to a central portion of a housing, a plunger is reciprocally fitted in an inner hole of the cylinder, and a plunger chamber in the inner hole of the cylinder is connected to an inlet side. In a high-pressure fuel pump in which one end of a cylinder is connected to a low-pressure fuel inlet through a passage and to a high-pressure fuel outlet through an outlet-side communication passage, and a plunger is engaged with a cam of a camshaft through a valve lifter. The plunger is sealed by a cover, and a plunger chamber is formed by the inner hole of the cylinder, the cylinder cover, and one end surface of the plunger, and the plunger is constituted by a first plunger and a second plunger.
A plunger is slidably fitted, a gas at a predetermined pressure is sealed in a sealed space between the first plunger and the second plunger, and the total length of the first plunger and the second plunger is limited to a predetermined value or less. The first configuration is that the total length of the first plunger and the second plunger can be reduced by compressing the gas in the sealed space. According to the present invention, in the first configuration, a blind hole having a circular cross section is formed in the axial direction of the first plunger or the second plunger.
A cylindrical fitting portion was formed at the end of the plunger, a sealing space was formed by inserting the fitting portion into the blind hole, and the gap between the inner surface of the blind hole and the outer surface of the fitting portion was sealed by an O-ring. The second
Configuration. According to a second aspect of the present invention, in the second configuration, a low pressure side check valve is disposed between the inlet side communication path and the low pressure fuel inlet, and a high pressure side check valve is disposed between the outlet side communication path and the high pressure fuel outlet. A supplementary space communicating with the sealed space is formed in the first plunger and / or the second plunger, an annular groove having a predetermined width is formed in the outer peripheral surface of the fitting portion, and a retaining pin fixed to the blind hole wall. Is inserted into the annular groove, and the gas chamber formed by the blind hole and the distal end face of the fitting portion is filled with nitrogen gas.

[0006]

1 to 3 show an embodiment of a high-pressure fuel pump according to the present invention. As shown in FIGS. 1 and 2,
At the center of the housing 11 of the high-pressure fuel pump, there is formed a stepped hole penetrating in the vertical direction, and the stepped holes are medium-diameter holes in order from the top.
12, a small-diameter hole 13 and a large-diameter hole 14. Medium bore
A cylindrical cylinder 17 with a step is inserted into the 12 and the small-diameter hole 13 from above, and the large-diameter portion 18 and the small-diameter portion 19 on the outer periphery of the cylinder 17 are fitted into the medium-diameter hole 12 and the small-diameter hole 13 of the stepped hole, respectively. The lower end of the cylinder 17 projects downward from the small-diameter hole 13. A disk-shaped cylinder cover 23 is fixed to the upper part of the cylinder 17 at the upper end (one end) of the medium diameter hole 12, and the upper end of the medium diameter hole 12 is sealed by the cylinder cover 23.
The upper end is sealed.

A plunger according to an embodiment of the present invention comprises a first plunger 25 and a second plunger 30, and a blind hole 26 having a circular cross section is formed in the axial direction of the first plunger 25.
The lower end of the blind hole 26 is open. A cylindrical fitting portion 31 is formed above the second plunger 30, and the fitting portion 31 of the second plunger 30 is slidably fitted in the blind hole 26 of the first plunger 25. The outer surface of the first plunger 25 has a truncated conical portion at the upper end, the other portion has the same diameter over the entire length, and the outer surface of the second plunger 30 has a large-diameter portion below the fitting portion 31.
The outer diameter of the large diameter portion 32 is the same as the outer diameter of the first plunger 25. The inner hole 20 of the cylinder 17 has a precisely machined sliding portion 21, from which a plunger composed of a first plunger 25 and a second plunger 30 is slidably inserted from below. The surface can contact the inner hole 20, and the large diameter portion 32 of the second plunger 30 is
It is set not to be inserted in 20.

A first annular groove 33 is formed at the upper end of the fitting portion 31 of the second plunger 30, and an O-ring 86 is mounted on the first annular groove 33, and the inner peripheral surface of the blind hole 26 is formed by the O-ring 86. And the outer peripheral surface of the fitting portion 31 is sealed. 2nd plunger
A second annular groove having a predetermined width is formed at the center of the fitting portion 31 of the vertical direction.
34, the thin portion (blind hole) at the lower end of the first plunger 25 is formed.
The inner portions of the plurality of retaining pins 37 fixed to the wall 26) are inserted into the second annular groove 34. In addition, retaining pin
37 is on a plane perpendicular to the center line of the first plunger 25,
The inside is directed to the center line.

The sealed space 28 between the blind hole 26 of the first plunger 25 and the upper end surface of the second plunger 30 is filled with nitrogen gas at a predetermined pressure (for example, 12 MPa at the upper end surface of the injection pipe or the first plunger 25). (The pressure at which compression starts when the set pressure is applied). Before the first plunger 25 and the second plunger 30 are assembled, the upper end of the second plunger 30 is positioned below the filling hole 38 of the first plunger 25, and the filling nozzle is filled with the nitrogen gas. Press it against. When the desired pressure is reached, the O-ring 86 of the first annular groove 33 is moved above the filling hole 38, and the retaining pin 37 is mounted at the position shown. In addition, sealed space
As shown by the dotted line in FIG. 2, a first plunger 25
A supplementary space 35 is formed or / and a second supplementary space 36 is formed in the second plunger 30 to provide a first supplementary space 35 and a second supplementary space.
Preferably, 36 communicates with sealed space 28.

By filling with nitrogen gas, a function similar to that of an air spring is exhibited, and the first plunger 25 and the second plunger 30 are separated from each other (the total length of the first plunger 25 and the second plunger 30 is increased). Direction), the retaining pin 37 engages with the second annular groove 34, thereby causing the first
The distance between the plunger 25 and the second plunger 30 (the total length of the first plunger 25 and the second plunger 30) is limited to a predetermined value or less. The first plunger 25 and the second plunger 30 are reversed in the fitting state, for example, the lower second plunger
It is a matter of course that a blind hole may be provided in 30 and a fitting portion may be formed in the first plunger 30.

An annular groove 48 is formed at the lower end of the second plunger 30, a central hole of a connection fitting 49 is engaged with the annular groove 48 by an appropriate method, and a flange of the connection fitting 49 is connected to the valve lifter.
It touches the bottom of 39. A cylindrical portion of a valve lifter 39 is reciprocally inserted from below into the large-diameter hole 14 of the housing 11, and a spring 43 is provided between the upper surface of the flange portion of the connection fitting 49 and the annular step portion 41 at the upper end of the large-diameter hole 14. Is installed. The valve lifter 39 is urged downward by the spring force of the spring 43, and the distal end surface (lower side surface) of the valve lifter 39 is engaged with the cam surface of the cam 46 of the camshaft 45. The camshaft 45 is rotated by the crankshaft of the engine.
It is set to make two rotations. The camshaft
When 45 rotates once, the valve lifter 39 makes two reciprocations.

An annular engagement groove 52 is formed at the lower end of the small-diameter hole 13 of the housing 11, and the upper end of a cylindrical support member 55 is engaged with and fixed to the engagement groove 52. A seal member 54 is integrally fixed to the support metal 55, and the seal member 54 is a support metal.
The lower flange 55 extends from the inner flange to the inner surface of the support fitting 55. The seal member 54 is formed of lubricating plastic, and has a ring-shaped and skate-shaped cross section, and a seal portion having contact portions at upper and lower ends of an inner peripheral surface thereof is in contact with the outer peripheral surface of the second plunger 30. The outer peripheral surface of the second plunger 30 is slidably supported by the seal member 54,
Protects dust from entering between the plunger 30 and the inner hole 20 of the cylinder 17.

The upper end portion 22 of the inner hole 20 of the cylinder 17 is slightly larger in diameter than the sliding portion 21 of the inner hole 20, and the upper end portion 22, the lower surface of the cylinder cover 23, and the upper end surface of the first plunger 25 (one end surface). Thus, a plunger chamber 57 is formed. At the upper part of the housing 11, there are an inlet-side protrusion 59 and an outlet-side protrusion 60, and the inlet-side protrusion 59 has an inlet-side insertion hole 62 formed therein.
The outlet-side protrusion 60 has an outlet-side insertion hole 63 formed therein.
The inner end of the inlet-side insertion hole 62 communicates with the medium-diameter hole 12 of the cylinder 17 via the inlet-side first communication passage 65, and the inlet-side first communication passage 65 is formed on the upper wall of the cylinder 17. The two-way passage 66 communicates with the plunger chamber 57. Similarly, the inner end of the outlet side insertion hole 63 communicates with the medium diameter hole 12 of the cylinder 17 via the outlet side first communication passage 67, and the outlet side first communication passage 67 is formed in the upper wall of the cylinder 17. The second communication passage 68 communicates with the plunger chamber 57.

An O-ring 70, a low-pressure side check valve body 71, and a low-pressure side valve seat 72 are sequentially inserted into the inlet-side insertion hole 62, and a female screw at the opening of the inlet-side insertion hole 62 has an inlet-side connector. 73 is screwed, and the entrance-side connecting member 73 is prevented from loosening.
A low pressure side check valve body 71 is provided with a cylindrical support valve seat 74, and a ball-shaped low pressure side valve 75 is disposed between the low pressure side valve seat 72 and the support 74. A side check valve 76 is formed. The low-pressure fuel is
From the low-pressure fuel inlet 77 through the low-pressure side check valve 76, the inlet-side first communication passage 65, and the inlet-side second communication passage 66 to the plunger chamber 57.

An O-ring 79 and a high-pressure valve seat body 80 are inserted into the outlet-side insertion hole 63, and a high-pressure-side check valve main body 81 also serving as an outlet-side fitting is provided in a female thread at the opening of the outlet-side insertion hole 63. Is screwed. A high-pressure side check valve body 81 is provided with a cylindrical support (spring) 82, and a ball-shaped high-pressure side valve 83 is disposed between the high-pressure side valve seat 80 and the support 82. A side check valve 84 is formed. The high-pressure fuel can flow out of the plunger chamber 57 through the outlet-side second communication passage 68, the outlet-side first communication passage 67, the high-pressure side check valve 84, and the high-pressure fuel outlet 85 of the high-pressure side check valve body 81. I have.

Next, the operation of the embodiment of the high-pressure fuel pump will be described. When the engine is operated, the camshaft 45 rotates, and when the cam 46 rotates, the valve lifter 39 descends, and the urging force of the spring 43 causes the second plunger 30 to retreat (down), and the first plunger 25 also moves to the second plunger 30.
Retreat at the same time. Since the sealed space 28 is maintained at a predetermined high pressure, the retaining pin 37 engages with the upper end of the second annular groove 34, and when the pressure of the plunger chamber 57 is lower than the set pressure, the first plunger 25 and the This is because they move simultaneously with the two plungers 30. When the first plunger 25 is retracted, the pressure in the plunger chamber 57 decreases, and the low-pressure fuel passes through the low-pressure fuel inlet 77, the low-pressure side check valve 76, the inlet-side first communication passage 65 and the inlet-side second communication passage 66, It flows into the chamber 57.

The rotation of the cam 46 causes the valve lifter 39 and the second
First plunger 25 when plunger 30 moves forward (rises)
At the same time, and the plunger chamber 57 is pressurized. The high-pressure fuel is discharged from the plunger chamber 57 to the injection pipe through the outlet-side second communication passage 68, the outlet-side first communication passage 67, the high-pressure side check valve 84, and the high-pressure fuel outlet 85 of the high-pressure side check valve body 81. When the pressure of the injection pipe and the plunger chamber 57 is equal to or lower than the set pressure, the first plunger 25 advances integrally with the second plunger 30, and from the moment when the pressure of the injection pipe and the plunger chamber 57 reaches the set pressure, Even if the nitrogen gas in the sealed space 28 is compressed and the second plunger 30 moves forward, the first plunger 25 does not move any further and does not discharge high-pressure fuel. Thus, the pressure in the injection pipe and the plunger chamber 57 is maintained at the set pressure.

The pressure of the nitrogen gas in the sealed space 28 rises by an amount corresponding to the compression, and strictly speaking, the control pressure in the injection pipe and the plunger chamber 57 fluctuates and exceeds the set pressure. Therefore, not only the size of the sealed space 28 is made larger than the cam stroke, but as shown in FIG. 2, the first refill space 35 and the second refill space 36 are communicated with the sealed space 28 to substantially reduce the sealed space. The pressure increase due to the compression of nitrogen gas is reduced so that practical problems do not occur. Therefore, when the engine is under a low load, the nitrogen gas in the sealed space 28 is compressed, the stroke of the first plunger 25 is reduced, the pressure is maintained at the set pressure, and the fuel is oversupplied and rises. Absent. FIG. 3A shows a state in which the nitrogen gas in the sealed space 28 is compressed at a low load, and the stroke of the first plunger 25 is reduced.
(b) shows a normal stroke at high load. Note that FIG.
As shown in the figure, the maximum stroke S ₀ of the first plunger 25
Is smaller than the stroke S of the sealed space 28.

[0019]

According to the high pressure fuel pump of the present invention, the first plunger and the second plunger are slidably fitted to each other, and
A gas (nitrogen gas) of a predetermined pressure is sealed in a sealed space between the plunger and the second plunger, and the first plunger and the second plunger are sealed.
The total length of the plungers is limited to a predetermined value or less, and the total length of the first plunger and the second plunger can be reduced by compressing the gas in the sealed space. Therefore, when the pressure of the plunger chamber or the injection pipe exceeds the set pressure, the stroke of the first plunger (the pressurizing portion of the plunger) becomes smaller than the stroke of the second plunger, and the injection is performed without performing the return control. The inside of the pipe can be maintained at a predetermined set pressure. Therefore, the conventional return passage and solenoid valve are not required, and the size and cost of the pump are reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of a high-pressure fuel pump according to the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 (a) is a diagram showing a relationship between a plunger stroke and a camshaft rotation angle under a low load, and FIG. 3 (b) is a relationship between a plunger stroke and a camshaft rotation angle under a high load. FIG.

[Explanation of symbols]

 11: Housing 17: Cylinder 20: Inner hole 23: Cylinder cover 25: First plunger 26: Blind hole 28: Sealed space (gas chamber) 30: Second plunger 31: Fitting part 35: First refill space 36: First 2 Refill space 37: Retaining pin 39: Valve lifter 45: Cam shaft 46: Cam 57: Plunger chamber 65: Inlet first communication path 66: Inlet second communication path 67: Outlet first communication path 68: Outlet side Second communication passage 76: Low pressure side check valve 77: Low pressure fuel inlet 84: High pressure side check valve 85: High pressure fuel outlet

Claims (3)

[Claims] 1. A cylinder is fixed to a center portion of a housing, a plunger is fitted to an inner hole of the cylinder so as to be reciprocally movable, and a plunger chamber in the inner hole of the cylinder is connected to a low-pressure fuel inlet through an inlet communication passage. In the high-pressure fuel pump, which is connected to the high-pressure fuel outlet through the outlet-side communication passage and the plunger is engaged with the cam of the camshaft via the valve lifter, one end of the cylinder is sealed by a cylinder cover, and the inside of the cylinder is closed. A plunger chamber is formed by the hole, the cylinder cover, and one end surface of the plunger. The plunger is constituted by a first plunger and a second plunger. The first plunger and the second plunger are slidably fitted to each other, and the first plunger is provided. A gas at a predetermined pressure is sealed in a sealed space between the first plunger and the second plunger. A high-pressure fuel pump, wherein the length is limited to a predetermined value or less, and the total length of the first plunger and the second plunger can be reduced by compressing gas in the sealed space. 2. A blind hole having a circular cross section is formed in the axial direction of the first plunger or the second plunger, and a cylindrical fitting portion is formed at an end of the second plunger or the first plunger.
2. The high-pressure fuel pump according to claim 1, wherein a sealed space is formed by inserting the fitting portion into the blind hole, and the space between the inner surface of the blind hole and the outer surface of the fitting portion is sealed by an O-ring. 3. A sealed space in which a low pressure side check valve is disposed between the inlet side communication passage and the low pressure fuel inlet, and a high pressure side check valve is provided between the outlet side communication passage and the high pressure fuel outlet. Is formed in the first plunger or the second plunger, an annular groove having a predetermined width is formed on the outer peripheral surface of the fitting portion, and a retaining pin fixed to the blind hole wall is inserted into the annular groove. 3. The high-pressure fuel pump according to claim 2, wherein the gas chamber formed by the blind hole and the front end face of the fitting portion is filled with nitrogen gas.