JPH09151826A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection device to improve sliding ability of the valve element of a solenoid valve to regulate a fuel pressure in a control pressure chamber. SOLUTION: An inner valve 34 is slidably guided by the inner wall 33b of a cylindrical pressure control valve 32 and a pressure balance chamber 35 is partitioned by the inner valve 34 and the inner wall of the pressure control valve 32. The pressure balance chamber 35 communicates with a control pressure chamber 42 in which high pressure fuel is introduced from a pressure accumulating chamber 8. An annular low pressure chamber 36 is arranged between the outer peripheral wall 32a of the pressure control valve 32 for a part of which the pressure balaruce chamber 35 consists and a valve body 31. During seating of the valve seat 31c of the pressure control valve 32, a pressure in the pressure balance chamber 35 is increased to a value higher than that in the low pressure chamber 36 by means of high pressure fuel of the control pressure chamber 42, the pressure control valve 32 is radially expanded. However, since a sufficient gas is ensured between the outer peripheral wall 32a and the valve body 31 by the low pressure chamber 36, defective sliding due to breakage of an oil film at this part and lodging of a foreign matter is prevented from occurring.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fuel injection device for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in an injector of a fuel injection device for an internal combustion engine, a control pressure chamber capable of introducing high pressure fuel is provided on the side opposite to the injection hole of a valve body, and the pressure of this control pressure chamber is increased together with the biasing force of a compression coil spring. It is known that the fuel injection timing is controlled by urging the valve body in the valve closing direction by means of the above, and by connecting and disconnecting the control pressure chamber and the low pressure side using an electromagnetic valve.

In the above fuel injection device, the pressure in the control pressure chamber is adjusted by providing, for example, a two-way valve that connects and disconnects the control pressure chamber and the low pressure fuel passage as the solenoid valve. The valve element of the two-way valve is driven in the valve opening direction by energizing the electromagnetic coil, and is biased in the valve closing direction by the compression coil spring.

[0004]

FIG. 4 shows an example of such a two-way valve used in the above fuel injection device having a control pressure chamber. The two-way valve 200 includes a valve body 220 and a pressure control valve 230. The valve body 220 has a sliding hole 221 formed by the large-diameter inner wall 220a and communicating with the low-pressure fuel passage 240, and a communication passage 222 formed by the small-diameter inner wall 220b. The communication passage 222 communicates with a control pressure chamber (not shown) located in the lower part of FIG. 4, and high pressure fuel is supplied to the control pressure chamber from a common rail (not shown). Small diameter inner wall 220b, large diameter inner wall 220a
Are provided in this order from the control pressure chamber side, and the pressure control valve 230 is guided by the large-diameter inner wall 220a so as to be capable of reciprocating.

An annular valve seat 223 is provided between the large diameter inner wall 220a and the small diameter inner wall 220b. When the pressure control valve 230 separates from the valve seat 223, the low pressure fuel passage 240
And the control pressure chamber communicate with each other, and the pressure control valve 230 is connected to the valve seat 22.
When seated at 3, the communication between the low pressure fuel passage 240 and the control pressure chamber is cut off. The pressure control valve 230 is formed in a cylindrical shape, and by the end surface of the sealing member 210 on the control pressure chamber side that slides with the inner wall of the pressure control valve 230 and the inner wall of the pressure control valve 230, the pressure control valve 230 is provided inside the pressure balance chamber 212. Are sectioned. The pressure balance chamber 212 communicates with the control pressure chamber via a communication passage 222.

A compression coil spring (not shown) for urging the pressure control valve 230 in the seating direction and an electromagnetic coil (not shown) for driving the pressure control valve 230 in the seating direction are provided above the pressure control valve 230 in FIG. Has been. When the electromagnetic coil is not energized, the pressure control valve 230 is seated on the valve seat 223 by the urging force of the compression coil spring, and the communication between the control pressure chamber and the low pressure fuel passage 240 is cut off. At this time, the fuel pressure in the control pressure chamber and the pressure balance chamber 212 is high due to the high-pressure fuel supplied from the common rail. When the electromagnetic coil is energized from this state, the pressure control valve 230 separates from the valve seat 223, and the control pressure chamber and the low pressure fuel passage 240 communicate with each other. As a result, the high-pressure fuel in the control pressure chamber is transferred to the low-pressure fuel passage 24.
Since it flows to 0, the pressure in the control pressure chamber drops. In this way, the pressure control valve 230 is driven by turning on and off the power supply to the electromagnetic coil, and the pressure in the control pressure chamber is adjusted by connecting and disconnecting the control pressure chamber and the low pressure fuel passage 240.

By the way, in the above solenoid valve 200,
The clearance 224 between the outer peripheral wall of the pressure control valve 230 and the inner wall 220a of the valve body 220 is defined by the pressure control valve 230.
And the inner wall 220a are slidable, and the width is set to such an extent that an oil film is formed by the fuel between the outer peripheral wall of the pressure control valve 230 and the inner wall 220a of the valve body 220. This is the valve body 22 utilizing this oil film.
This is because the pressure control valve 230 slides smoothly with respect to zero.

However, when the pressure control valve 230 is seated, the pressure balance chamber 212 has a high pressure and the clearance 224 has a low pressure as described above. Therefore, as shown by the dotted line in FIG. The portion of the pressure control valve 230 forming the elastically deforms elastically so as to expand radially outward. As a result, the clearance 224 becomes smaller than that when the pressure control valve 230 is separated, so that the oil film is broken and a sliding failure of the pressure control valve 230 occurs. Further, when the clearance 224 becomes smaller, fine foreign matter that has passed through a fuel filter (not shown) that filters the fuel supplied to the control pressure chambers will have an outer peripheral wall and an inner wall 220 of the pressure control valve 230.
It is caught between the pressure control valve 2 and
30 sliding failure occurs. In this way, the pressure control valve 2
When the sliding failure of 30 occurs, the pressure in the control pressure chamber cannot be adjusted properly, so that the accuracy of the fuel injection amount and the fuel injection timing deteriorates.

An object of the present invention is to provide a fuel injection device in which the valve body of the solenoid valve for adjusting the fuel pressure in the control pressure chamber has a good slidability.

[0010]

In order to solve the above problems, the fuel injection device of the present invention employs the means described in claim 1. That is, between the second valve member and the inner peripheral wall of the valve body, the valve seat side of the sliding portion between the sealing member and the second valve member from the seated position of the second valve member and the valve seat. An annular low pressure chamber is formed that extends from the end portion to the lift side of the second valve member. This ensures a sufficient gap between the outer peripheral wall of the pressure control valve and the valve body forming the low pressure chamber even if the pressure control valve expands and deforms radially due to the pressure difference between the pressure balance chamber and the low pressure chamber. To be done. In addition, a sliding portion between the valve body and the second valve member is formed on the lift side of the second valve member with respect to the low pressure chamber, and expansion deformation of the pressure control valve due to a pressure difference between the pressure balance chamber and the low pressure chamber occurs. Since it is possible to prevent the sliding part from reaching the sliding part, it is possible to prevent the oil film from being cut off or foreign matter from being caught in the sliding part. As a result, the reciprocating movement of the pressure control valve is smoothly performed when the electromagnetic valve is opened and closed, so that the fuel injection amount and the fuel injection timing can be accurately controlled.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) A first embodiment in which the fuel injection device of the present invention is applied to a pressure-accumulation type diesel internal combustion engine is shown in FIGS. 1 and 2.

A fuel reservoir 13 and an injection hole 16 are formed in the nozzle body 11 of the injector 10 so as to communicate with each other through a valve body sliding hole 14, and the nozzle body 11 forming the valve body sliding hole 14 is formed. The needle valve 21 is housed in the inner wall so as to be capable of reciprocating. The pressure pin 24 and the pressure pin 2 are provided on the side opposite to the injection hole of the needle valve 21.
Control piston 25 that contacts or connects with No. 4 on the side opposite to the injection hole
Are arranged. Pressure pin 24 is spring 2
3, the spring 23 urges the pressure pin 24 downward in FIG. 1, that is, in the injection hole closing direction. Here, the needle valve 21, the pressure pin 24, and the control piston 25 correspond to the "first valve member" described in the claims, and the spring 23 is the "first biasing means" described in the claims. Equivalent to.

The high-pressure fuel pumped up by the supply pump 7 and accumulated in the accumulator chamber 8 of the common rail is supplied to the fuel reservoir 13 through the high-pressure fuel passage 51, and the pressure of the high-pressure fuel in the fuel reservoir 13 is adjusted by the needle valve 20. Works to lift. The high pressure fuel in the pressure accumulating chamber 8 is also supplied to the control pressure chamber 42 through the high pressure fuel passage 53 provided with the first throttle hole 52.

Above the nozzle body 11, a solenoid valve 30 including a valve body 31 and a pressure control valve 32 is provided. The solenoid valve 30 is a two-way valve that connects and disconnects the control pressure chamber 42 and a low-pressure fuel passage 56 described later. The pressure control valve 32 as the second valve member is formed in a cylindrical shape, and a sliding hole 33 is formed inside the pressure control valve 32 by the tapered surface 33a and the inner wall 33b so as to penetrate the pressure control valve 32 in the axial direction. . The tapered surface 33a and the inner wall 33b are provided in this order from the control pressure chamber side. The inner valve 34 as a sealing member is slidably guided by the inner wall 33b, and the inner valve 34, the tapered surface 33a and the inner wall 33b define a pressure balance chamber 35 inside the pressure control valve 32. This pressure balance chamber 3
5 is open to the control pressure chamber 42 side. Pressure control valve 3
The movement of 2 and the inner valve 34 in the upward direction in FIG. 1 is restricted by a stopper 39.

In the valve body 31, an annular groove 31a having a diameter larger than the outer circumference of the pressure control valve 32 is provided coaxially with the pressure control valve 32. An annular low pressure chamber 36 is formed between the annular groove 31a and the outer peripheral wall 32a of the pressure control valve 32. As shown in FIG. 2, at the upper end position where the inner valve 34 is in contact with the stopper 39, the low pressure chamber 36 has a control pressure of the sliding portion between the pressure control valve 32 and the inner valve 34 from the valve seat 31c. It is formed to a lift side of the pressure control valve 32 by a distance H from the chamber side end portion. The low pressure fuel passage 56 provided in the valve body 31 communicates with the low pressure chamber 36.

Following the control pressure chamber side of the annular groove 31a,
The small-diameter inner wall 31b forming the communication passage 41 has the valve body 3
1 extends in the axial direction. As shown in FIG. 1, the communication passage 4
1 and the control pressure chamber 42 communicate with each other via a high pressure fuel passage 55 provided with a second throttle hole 54. Here, the flow passage area of the second throttle hole 54 is smaller than the flow passage area of the first throttle hole 52. An annular valve seat 31c on which a pressure control valve 32 can be seated between the annular groove 31a and the small-diameter inner wall 31b.
Are formed. The pressure control valve 32 is guided so as to be axially reciprocally movable by a sliding inner wall 31d that continues from the anti-control pressure chamber 42 side of the annular groove 31a. In the sliding portion 43 composed of the inner sliding wall 31d and the outer peripheral wall 32a of the pressure control valve 32, the clearance between the inner sliding wall 31d and the outer peripheral wall 32a slides between the pressure control valve 32 and the inner sliding wall 31d. The width is set so that it is possible and an oil film is formed by the fuel between the sliding inner wall 31d and the outer peripheral wall 32a.

Above the pressure control valve 32 in FIG.
A compression coil spring 37 as a second urging means for urging the pressure control valve 32 toward the valve seat 31c, and an electromagnetic coil 38 for driving the pressure control valve 32 in a direction away from the valve seat 31c by energization are provided. It is provided. Next, the operation of this fuel injection device will be described. (1) When the energization of the electromagnetic coil 38 is off, the pressure control valve 32
Is the valve seat 31c due to the urging force of the compression coil spring 37.
Since the communication between the control pressure chamber 42 and the low pressure fuel passage 56 is cut off, the fuel pressure in the control pressure chamber 42 is high. By the sum of the force received from the fuel pressure in the control pressure chamber and the urging force of the spring 23, the needle valve 21 closes the injection hole 16 against the force in the lift direction of the needle valve 21 due to the fuel pressure of the fuel reservoir 13. doing. Further, the fuel pressure in the pressure balance chamber 35 communicating with the control pressure chamber 42 is also high, and is smaller than the area where the pressure acts downward on the pressure control valve 32 in FIG. Since it is larger, the fuel pressure in the pressure balance chamber 35 also acts in the seating direction of the pressure control valve 32 in addition to the urging force of the compression coil spring 37. On the other hand, the low pressure fuel passage 5
The low pressure chamber 36 communicating with 6 has a lower pressure than the pressure balance chamber 35.

At this time, the pressure balance chamber 35 and the low pressure chamber 3
Due to the pressure difference with the pressure control valve 6, the pressure control valve 32 in the portion forming the pressure balance chamber 35 slightly expands radially outward, as shown by the dotted line in FIG. However, since the low pressure chamber 36 is provided between the outer peripheral wall 32a of the pressure control valve 32 and the valve body 31 in the expanding portion, the outer peripheral wall of the pressure control valve 32 is expanded even if the pressure control valve 32 expands. A sufficient gap is secured between 32a and the annular groove 31a forming the low pressure chamber 36. The sliding portion 43 between the sliding inner wall 31d of the valve body 31 and the outer peripheral wall 32a of the pressure control valve 32 has a distance H from the end of the sliding portion between the pressure control valve 32 and the inner valve 34 on the control pressure chamber side. Since it is provided only on the lift side of the pressure control valve 32, the deformation due to the expansion of the pressure control valve 32 does not extend to the sliding portion 43. Therefore, even when the fuel pressure in the pressure balance chamber 35 is high, the sliding inner wall 3
Since the clearance between 1d and the outer peripheral wall 32a is maintained at a predetermined width, it is possible to prevent the sliding failure of the pressure control valve 32 due to the oil film running out in the sliding portion 43 or the foreign matter being caught. (2) When energizing the electromagnetic coil 38, the spring 37
Also, the pressure control valve 42 separates from the valve seat 31c against the biasing force due to the fuel pressure in the pressure balance chamber 35, and the control pressure chamber 42 and the low pressure chamber 36 communicate with each other. As a result, the high-pressure fuel in the control pressure chamber 42 flows into the low-pressure chamber 36 through the second throttle hole 54, and the low-pressure fuel passage 5 is further discharged from the low-pressure chamber 36.
Runs out to 6. Here, from the pressure accumulation chamber 8 to the control pressure chamber 42
Of the flow passage area of the first throttle hole 52 which defines the flow rate of the fuel introduced into the low pressure chamber 36 compared with the flow passage area of the first throttle hole 52 which defines the flow rate of the fuel introduced into the low pressure chamber 36. The fuel pressure in the control pressure chamber 42 is relatively lower than the fuel pressure in the high-pressure fuel passage 51 because the fuel pressure in the control pressure chamber 42 is set higher. Needle valve 21 due to fuel pressure in fuel reservoir 13
When the balance between the force acting in the lift direction of the needle valve 21 and the force acting in the valve closing direction of the needle valve 21 due to the fuel pressure of the control pressure chamber 42 and the urging force of the spring 23 is reversed, the needle valve 21 lifts and comes out from the injection hole 16. Fuel is injected.

Thus, the pressure control valve 42 of the solenoid valve 30 is
Moves back and forth in the axial direction of the valve body 31 to move the valve seat 31c.
By sitting on or away from the control pressure chamber 42 and the low-pressure fuel passage 56, the pressure of the control pressure chamber 42 is adjusted, and the pressure of the control pressure chamber 42 controls the fuel injection timing and the fuel injection amount. Have control. First of the present invention
According to the fuel injection device of the embodiment, by providing the annular recessed groove 31a in the valve body 31, between the outer peripheral wall 32a of the pressure control valve 32 and the valve body 31, from the valve seat 31c to the pressure control valve 32 and the inner valve 34. A low pressure chamber 36 is formed that extends to the lift side of the pressure control valve 32 by a distance H from the end of the sliding portion of the control pressure chamber side. The sliding portion 43 between the valve body 31 and the pressure control valve 32 is formed on the lift side of the pressure control valve 32 with respect to the low pressure chamber 36. As a result, the pressure balance chamber 35 and the low pressure chamber 36
Even if the pressure control valve 32 expands in the radial direction due to the pressure difference between the pressure and the pressure, this expansion does not reach the sliding portion 43. Therefore, since the clearance between the sliding inner wall 31d and the outer peripheral wall 32a is maintained at a predetermined width, the pressure control valve 32 smoothly reciprocates, and the fuel injection amount and the fuel injection timing can be accurately controlled. The effect is that you can do it.

As a method of setting the distance H, as shown in FIG. 2, a deformation analysis by FEM (finite element method) is performed with the axial length A of the annular groove 31a and the axial length B of the inner valve as variables. By doing so, the optimum value of the distance H can be obtained. (Second Embodiment) A second embodiment of the present invention is shown in FIG. First
The same components as those in the embodiment are designated by the same reference numerals.

The solenoid valve 130 is a two-way valve, and has a large diameter inner wall 1
A valve body 131 having a sliding hole 131 formed by 31a and a communication passage 41 formed by a small diameter inner wall 131b communicating with the sliding hole 131, and a large diameter inner wall 1
The pressure control valve 132 is reciprocally guided by 31a and can be seated on a valve seat 31c provided on the valve body 131.

The pressure control valve 132 is formed in a cylindrical shape, and an inner wall 33b of the pressure control valve 132 slidably guides the inner valve 34. Inner valve 34, tapered surface 33
A pressure balance chamber 35 is defined inside the pressure control valve 132 by a and the inner wall 33b. Outer peripheral wall 1 of the pressure control valve 132 in the portion forming the pressure balance chamber 35
32a is provided with an annular thinning portion 132b. The thinning portion 132b and the large-diameter inner wall 13 of the valve body 131 are provided.
An annular low pressure chamber 136 communicating with a low pressure fuel passage (not shown) is formed between the low pressure chamber 1a and 1a. Meat removal part 132b
Is formed up to the lift side of the pressure control valve 132 by a distance H from the control pressure chamber side end of the sliding portion between the pressure control valve 132 and the inner valve 34. Above the low-pressure chamber 136 in FIG. 3, a sliding portion 143 is formed by the large-diameter inner wall 131a and the non-thinned outer peripheral wall 132a of the pressure control valve 132.

When the pressure control valve 132 is seated on the valve seat 33c, the pressure balance chamber 35 becomes higher in pressure than the low pressure chamber 136 due to the high pressure fuel supplied to the control pressure chamber (not shown), and as shown by the dotted line in FIG. The pressure control valve 132 in the portion forming the pressure balance chamber 35 expands in the radial direction. However, since the low pressure chamber 136 is provided between the valve body 131 and the outer peripheral wall 132a of the pressure control valve 132 in the portion of the pressure balance chamber 35 where the high pressure acts, the outer peripheral wall 3
A gap is secured between 2a and the large diameter inner wall 131a. Further, since the sliding portion 143 is formed on the lift side of the pressure control valve 132 with respect to the low pressure chamber 136, even if the pressure control valve 132 expands in the radial direction due to the high pressure of the pressure balance chamber 35, the deformation due to this expansion. Does not extend to the sliding portion 143. Therefore, the large-diameter inner wall 131a and the outer peripheral wall 1
Since the clearance between the pressure control valve 132 and 32a is kept within a predetermined range, the pressure control valve 132 smoothly reciprocates, and the fuel injection amount and the fuel injection timing can be controlled accurately.

[Brief description of the drawings]

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

FIG. 2 is a schematic cross-sectional view showing an electromagnetic valve of the fuel injection device according to the first embodiment of the present invention.

FIG. 3 is a schematic sectional view showing an electromagnetic valve of a fuel injection device according to a second embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view showing a solenoid valve of a conventional fuel injection device.

[Explanation of symbols]

 8 Accumulation chamber 10 Injector 11 Nozzle body 13 Fuel reservoir 16 Injection hole 21 Needle valve (first valve member) 23 Spring (first urging means) 24 Pressure pin (first valve member) 25 Control piston (first) 30 solenoid valve 31 valve body 31a annular groove 31b small diameter inner wall 31c valve seat 31d sliding inner wall 32 pressure control valve (second valve member) 34 inner valve (sealing member) 35 pressure balance chamber 36 low pressure chamber 37 Compression coil spring (second urging means) 38 Electromagnetic coil 39 Stopper 41 Communication passage 42 Control pressure chamber 43 Sliding parts 51, 53, 55 High pressure fuel passage 56 Low pressure fuel passage

Claims (2)

[Claims] 1. A fuel injection device for supplying high pressure fuel accumulated in a pressure accumulator to an injector provided for each cylinder of an internal combustion engine, and injecting fuel from an injection nozzle of the injector into a combustion chamber of each cylinder. A first valve member for connecting and disconnecting the high pressure fuel passage capable of supplying high pressure fuel to the injection hole of the injection nozzle and the injection hole; and a first valve member for urging the first valve member in the injection hole blocking direction. An urging means, and a control pressure chamber provided on the side opposite to the injection hole of the first valve member for urging the first valve member in the injection hole blocking direction by the fuel pressure supplied from the high-pressure fuel passage. A second valve member, which is an electromagnetic valve that connects and disconnects with the low-pressure fuel passage, has a pressure balance chamber that is open at both ends in the axial direction and that communicates with the control pressure chamber, and a second valve member that forms the pressure balance chamber. Anti-control pressure of the pressure balance chamber that slides on the inner wall of the A sealing member for sealing the opening on the chamber side, and a seat for the second valve member to form a valve seat for blocking communication between the control pressure chamber and the low-pressure fuel passage and the second valve member. A reciprocatingly supported valve body, second urging means for urging the second valve member in the seating direction to the valve seat, and energizing the second valve member from the valve seat. An electromagnetic valve comprising an electromagnetic coil that drives in the direction of separation of the valve body, and the second valve member communicates with the low-pressure fuel passage between the second valve member and the inner peripheral wall of the valve body. An annular low-pressure chamber is formed that is connected to and disconnected from the control pressure chamber, and the low-pressure chamber slides from the seating position between the second valve member and the valve seat between the sealing member and the second valve member. Extends to the lift side of the second valve member from the valve seat side end of the portion. Fuel injection device according to claim and. 2. The low-pressure chamber has a lift side of the second valve member with respect to a valve seat side end of a sliding portion of the sealing member and the second valve member following the valve seat. The fuel injection device according to claim 1, wherein the fuel injection device is formed by providing an annular groove extending to the valve body.