JP2001115925A - Unit injector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that injection quantities between cylinders become irregular by slight regulating difference because there is a characteristic for rapidly changing a fuel injection quantity against rotating speed, in a region of little injection under low rotating speed, in a conventional unit injector, and thereby a defect such as hunting or engine stall is generated. SOLUTION: A check valve 20 for opening/closing an oil passage for communicating a pressure chamber 3 and a nozzle 7 positioned on a downstream side of the pressure chamber 3, is composed of a first valve 21 slidably disposed in the oil passage 9, and a second valve 22 slidably fitted into the first valve 21 from the nozzle side 7. An orifice 32 is formed on the second valve 22, a spring 23 is interposed between the first valve 21 and the second valve 22, the firs valve 21 is energized to the pressure chamber 3 side, and the second valve 22 is energized to the nozzle 7 side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a unit injector which is a fuel injection device for a diesel engine.

[0002]

2. Description of the Related Art As shown in FIG. 10, for example, a conventional unit injector has a pressing portion 1 formed in a substantially cylindrical shape.
A plunger 2 is reciprocally inserted therein, and a pressurizing chamber 3 is formed. A nozzle 7 is provided downstream of the pressurizing chamber 3, and the pressurizing chamber 3 and the nozzle 7 are connected by an oil passage 9. A nozzle 72 is provided at the tip of the nozzle 7.
And is closed by a needle valve 70 slidably fitted in the nozzle 7 and urged toward the injection port 72 by a spring 8. A check valve 10 is interposed between the pressurizing chamber 3 and the oil passage 9, and the check valve 10
This opens and closes the oil passage 9 to prevent the flow from returning from the nozzle 7 side to the pressurizing chamber 3 side.

[0003] In FIG. 10, at the position where the plunger 2 is raised, an oil supply hole 4 formed in the pressurizing section 1 is inserted into the pressurizing chamber 3.
The fuel flows into the pressurizing chamber 3 through the oil supply hole 4. When the plunger 2 descends, the fuel supply hole 4 is closed by the plunger 2 and the fuel in the pressurizing chamber 3 is pushed by the plunger 2 to open the check valve 10 and flow toward the nozzle 7. When the plunger 2 further descends,
The fuel flowing into the fuel reservoir 71 of the nozzle 7 is pressurized, and pushes up the needle valve 70 against the urging force of the spring 8.
And the nozzle 72 communicate with each other, and fuel is injected from the nozzle 72. When the plunger 2 is lowered to some extent, the cutout groove 6 of the plunger 2 communicating with the pressurizing chamber 3 communicates with the fuel supply hole 4, so that the fuel in the pressurizing chamber 3 flows out of the fuel supply hole 4 and the fuel reservoir 7
The pressure of 1 decreases, the needle valve 70 closes the injection port 72, and the injection ends. Thereafter, when the plunger 2 rises, the pressure in the pressurizing chamber 3 becomes smaller than the pressure on the nozzle 7 side.
Check valve 10 closes.

[0004] The unit injector constructed as described above has no injection pipe, and is not affected by the reflected wave at the time of fuel injection. Therefore, the unit injector has no irregular injection and can easily perform high-pressure injection. It is used as a fuel injection device.
Further, the unit injector is characterized in that the injection pressure sharply increases from the start of the injection and the injection rate in the initial stage of the injection is high.

[0005]

[0008] However, unit injector described above, as shown in FIG. 11, in a small amount injection region of the idle rotational speed N ₀ of about or lower rotational speed, the fuel injection amount with respect to the rotational speed Has a characteristic that changes abruptly, so that the injection amount between the cylinders becomes uneven due to a slight adjustment difference, which causes problems such as hunting and engine stall. Note that FIG. 11 shows the fuel injection amount with respect to the number of revolutions of each of the rotational positions R ₋₁ , R, R ₊₁ , R ₊₂ , and R ₊₃ of the plunger 2, and the rotational position R ₋₁ , the rotational position R, rotation position R ₊₁ , rotation position R ₊₂ , rotation position R ₊₃
The rotation positions are such that the fuel injection amount increases in the order of.
Therefore, in order to make the injection amount in the low rotation speed range uniform, it is necessary to increase the precision of each component and to take a lot of labor and man-hours to assemble and adjust the governor link system, etc. Had become. In order to improve the characteristic of the fuel injection amount with respect to the rotation speed, a so-called suction-back function is provided between the pressurizing chamber 3 and the nozzle 7 to reduce the residual pressure on the nozzle 7 side when the plunger 2 rises. Although it is conceivable to provide a valve with a valve, the existing valve with a suction-back function is high, so if used as it is, the height of the unit injector itself will increase and the cylinder head position will be at a high position. The mountability at the time of mounting on a ship will be degraded. In addition, when the height of the unit injector is increased, the deformation due to the thrust force at the time of driving the unit injector is increased, and problems such as plunger sticking occur. Furthermore, if the injection rate in the early stage of injection is high, the combustion temperature will rise rapidly, so that NOx in the exhaust gas
Is difficult to reduce.

[0006]

The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described. That is, in the first aspect, a check valve that opens and closes an oil passage that communicates between the pressurizing chamber and a nozzle located downstream of the pressurizing chamber is provided with a first valve that is slidably provided in the oil passage. And a second valve slidably inserted from the nozzle side into the first valve, a communication passage is provided in the first valve, an orifice is formed in the second valve, and the first valve and An urging member was interposed between the second valve and the second valve to urge the first valve toward the pressurizing chamber and urge the second valve toward the nozzle.

According to a second aspect of the present invention, a check valve for opening and closing an oil passage communicating the pressurizing chamber and a nozzle located downstream of the pressurizing chamber is provided so as to be slidable in the oil passage. A first valve having a substantially ring shape, and a second valve slidably fitted in the first valve, wherein the first valve is closed on a boundary wall between the pressurizing chamber and the oil passage. In addition to providing a communication path that communicates the pressurizing chamber and the oil passage at the time, an orifice that communicates the pressurizing chamber and the nozzle-side oil passage is formed in the second valve,
The second valve was urged toward the nozzle by an urging member.

According to a third aspect of the present invention, an additional chamber is formed downstream of the pressurizing chamber, a piston is slidably provided in the additional chamber, and the piston is urged toward the pressurizing chamber by an urging member. did.

[0009]

Next, an embodiment of the present invention will be described. FIG. 1 is a side sectional view showing a unit injector of the present invention, FIG. 2 is a side sectional view showing a check valve portion of the unit injector, FIG.
5 is a diagram showing a change in fuel injection amount with respect to the engine speed in a unit injector using the check valve of FIGS. 2 and 3; FIG. 5 is a side sectional view showing another embodiment of the unit injector; FIG. 7 is a plan view showing the check valve used in the injector, FIG. 8 is a plan view of the same, FIG. 8 is a view showing a third embodiment of the unit injector, and FIG. 9 is a graph showing the relationship between the cam angle and the injection rate in the unit injector of FIG. FIG. 10 is a diagram showing the relationship, FIG. 10 is a diagram showing a conventional unit injector, and FIG. 11 is a diagram showing a change in the fuel injection amount with respect to the engine speed in the conventional unit injector.

First, the overall configuration of the unit injector of the present invention will be described. In the unit injector shown in FIG. 1, a plunger 2 is reciprocally inserted into a pressurizing portion 1 formed in a substantially cylindrical shape. A chamber 3 is formed. On the side wall surface of the pressurizing section 1, an oil supply hole 4 is formed for communicating the oil supply chamber outside the unit injector with the pressurizing chamber 3. A cutout groove 6 is formed on the outer peripheral surface of the plunger 2 so as to be inclined, and the cutout groove 6 and the pressurizing chamber 3 communicate with each other. A tappet 11 urged upward by a spring 5 is attached to the upper end of the plunger 2.
1 is moved downward by a cam or the like (not shown) integrally with the plunger 2, and is moved upward by the urging force of the spring 5.

A nozzle 7 is provided below the pressurizing chamber 3, that is, downstream of the pressurizing chamber 3, and the pressurizing chamber 3 and the nozzle 7 are connected by an oil passage 9. A nozzle 72 is bored at the tip of the nozzle 7 and is closed by a needle valve 70 slidably fitted in the nozzle 7 and urged toward the nozzle 72 by a spring 8. A fuel reservoir 71 is formed at the nozzle-side end of the oil passage 9. Further, a check valve 20 is interposed between the pressurizing chamber 3 and the oil passage 9, and the oil passage 9 is opened and closed by a first valve 21 constituting the check valve 20, and a pressure is applied from the nozzle 7 side. The flow is prevented from returning to the pressure chamber 3 side.

Next, the operation of the thus configured unit injector will be described. First, plunger 2
In the position where the pressure rises, the fuel supply hole 4 formed in the pressurizing section 1 communicates with the pressurizing chamber 3, and the fuel is supplied through the fueling hole 4 to the pressurizing chamber 3.
To fill the pressure chamber 3. When the plunger 2 descends, the fuel supply hole 4 is closed by the plunger 2 and the fuel in the pressurizing chamber 3 is pushed by the plunger 2,
Open the first valve 21 of the check valve 20 and set the nozzle 7
To the fuel reservoir 71 on the side. When the plunger 2 further descends, the fuel flowing into the fuel reservoir 71 is pressurized, and this pressure acts on the conical surface 70 a of the needle valve 70, and a force acts in a direction to push the needle valve 70 upward. When this force overcomes the urging force of the spring 8, the needle valve 70 is pushed upward, and the fuel reservoir 71
And the nozzle 72 communicate with each other, and fuel is injected from the nozzle 72.

When the plunger 2 is lowered to some extent, the cutout groove 6 of the plunger 2 communicates with the fuel supply hole 4, the fuel in the pressurizing chamber 3 flows out to the fuel supply chamber through the fuel supply hole 4, and the pressure in the fuel reservoir 71 decreases. Then, the needle valve 70 closes the injection port 72 by the urging force of the spring 8, whereby the injection ends. Further, in this case, since the first valve 21 is urged upward by the spring 23, when the urging force of the spring 23 overcomes the pressure in the pressurizing chamber 3, the first valve 21 is closed. Thereafter, when the plunger 2 rises, the pressure in the pressurizing chamber 3 decreases in the process of ascending and becomes lower than the pressure on the nozzle 7 side. Exerts a force in the direction of being sucked into the pressurizing chamber 3 side.

Next, the configuration of the check valve 20 will be described. As shown in FIGS. 2 and 3, a valve seat 25 having a communication hole 25 a is formed at the lower end of the pressure unit 1.
Is attached. Below the valve seat 25, a valve chamber 9a connected to the upper end of the oil passage 9 is formed, and a check valve 20 including a first valve 21 and a second valve 22 is formed in the valve chamber 9a. Is decorated.

The first valve 21 is formed in a substantially convex shape when viewed from the side.
The lower part 21b inserted into the valve chamber 9a with a certain gap provided therein has an outer diameter larger than the inner diameter of the communication hole 25a. Lower part 21 of first valve 21
A gap Lv is provided in the up-down direction between b and the valve chamber 9a, and the first valve 21 can move up and down within the range of the gap Lv. The upper surface of the lower portion 21b is formed on a sealing surface 21c. The sealing surface 21c contacts the valve seat 25 when the lower portion 21b moves upward to close the communication hole 25a. Close and divide. A communication passage 31 is formed in the upper portion 21 a of the first valve 21 to communicate the pressurizing chamber 3 of the first valve 21 with the oil passage 9 via the orifice 32 of the second valve 22. I have.

The valve seat 25 need not always be provided. The upper portion 21a of the first valve 21 is inserted into the pressurizing chamber 3, and the sealing surface 21c of the lower portion 21b is brought into contact with the lower end surface of the pressurizing section 1. Alternatively, the pressure chamber 3 and the oil passage 9 may be closed.

On the other hand, the second valve 22, which is formed in a substantially cylindrical shape with its lower end closed, is slidably inserted into a storage hole 21d formed in the first valve 21 from the lower surface side. A spring 23 is interposed between the second valve 22 and the first valve 21. The spring 23 urges the first valve 21 upward and urges the second valve 22 downward. ing. A gap Sr is provided in the up-down direction between the first valve 21 and the second valve 22, and the second valve 22 is vertically movable within the range of the gap Sr. Also,
An orifice 32 is formed in the second valve 22 to communicate the pressurizing chamber 3 side and the oil passage 9 side of the second valve 22. The gap Sr is equal to or larger than the gap Lv.

The check valve 20 constructed as described above
In the state, when the plunger 2 is raised and the inside of the pressurizing chamber 3 is not pressurized, the first valve 21 is urged upward by the spring 23, and the sealing surface 21c of the first valve 21 and the valve seat 25 are Abuts on the oil passage 9, and the second valve 22 is urged downward by a spring 23,
It is in contact with the lower surface of the valve chamber 9a.

The plunger 2 descends to close the oil supply hole 4,
When the pressure further decreases, the pressure in the pressurizing chamber 3 increases, and when this pressure exceeds the urging force of the spring 23, the first valve 2
1 moves downward to seal surface 21 c and valve seat 25.
Are separated from each other, the pressurizing chamber 3 and the oil passage 9 communicate with each other, and the fuel in the pressurizing chamber 3 flows into the oil passage 9. When the pressurized state is released after the pressurizing chamber 3 is communicated with the oil supply hole 4 and the pressure in the pressurizing chamber 3 decreases after the fuel injection, the urging force of the spring 23 and the pressure on the side of the oil passage 9 cause the first pressure. The valve 21 moves upward,
The oil passage 9 is closed while sitting on the valve seat 25.

Further, the pressure on the oil passage 9 side is greater than the urging force of the spring 23, and the pressure causes the two valves 22 to move toward the pressurizing chamber by the gap Sr. The second valve 22 is the pressurizing chamber 3
Side, the volume of the oil passage 9 closer to the nozzle 7 than the check valve 20 increases by the volume of the second valve 22 that has moved, and the nozzle 7 and the oil passage 9 correspond to the increased volume.
The residual pressure of the fuel remaining inside will decrease.

In this case, when the engine speed is high, the rising speed of the plunger 2 is high and the pressure in the oil passage 9 is high, so that the first valve 21 is suddenly seated on the valve seat 25 and the second valve 22 is also It works suddenly upward. When the second valve 22 suddenly operates, the resistance of the orifice 32 formed in the head increases, so that almost no fuel flows from the oil passage 9 into the oil chamber 27, and the second valve 22 has the gap Sr. Only, that is, the entire movable range moves to the pressurizing chamber 3 side.

Conversely, when the engine speed is low, the plunger 2 rises slowly and the pressure in the oil passage 9 is low, so that the resistance of the orifice 32 formed in the second valve 22 is small, and From the fuel chamber 27 into the oil chamber 27. Therefore, the suction efficiency of the second valve 22 decreases.

As described above, when the engine speed is high, the efficiency with which the second valve 22 sucks back into the pressurizing chamber 3 is high, and the degree of decrease in the residual pressure of the fuel remaining on the nozzle 7 increases. As a result, the residual pressure decreases. That is, the so-called suck-back effect by the second valve 22 is largely exerted. Further, when the engine speed is low, the efficiency of the second valve 22 sucking back to the pressurizing chamber 3 side is low, and the degree of decrease in the residual pressure of the fuel remaining on the nozzle 7 side is reduced. The pressure does not decrease so much and becomes higher than when the engine speed is high. That is, the so-called suction effect by the second valve 22 does not act so much.

The residual pressure of the fuel nozzle 7 side when the engine speed is low is made higher than the residual pressure when the engine speed is high, as shown in FIG. 4, idle speed N ₀
It is possible to moderate the change in the fuel injection amount with respect to the engine speed in the small-injection region at a low speed of about or less. Note that FIG. 4 shows the fuel injection amount with respect to the number of rotations of each of the rotational positions R _-2 , R _-1 , R, R ₊₁ , and R ₊₂ of the plunger 2, and the rotational position R _-2 , the rotational position R _-1 ,
The rotation position is such that the fuel injection amount increases in the order of the rotation position R, the rotation position R _{+ 1} , and the rotation position R _{+ 2} . This allows
It is easy to make uniform the injection amount between cylinders without making fine adjustments, etc., and it is possible to prevent problems such as hunting and engine stall, and to reduce assembly and adjustment man-hours. Can be planned.

Further, in this embodiment, the urging member of the first valve 21 and the urging member of the second valve 22 are shared by the spring 23. It is possible to improve the check valve function. Further, the second valve 22 having a so-called suction effect is replaced with a flat first valve 2 having a low height.
Since the check valve 20 is configured by being inserted into 1,
The height of the check valve 20 itself can be suppressed,
The height of the unit injector can be reduced, so that the mountability of the engine is improved, and problems such as plunger sticking can be prevented.

Next, another embodiment of the check valve for opening and closing the oil passage 9 communicating the pressurizing chamber 3 and the nozzle 7 will be described. In the unit injector shown in FIGS. 5 to 7, a check valve 50 is interposed between the pressurizing chamber 3 and the oil passage 9, and the first valve 51 constituting the check valve 50 connects the oil passage 9. Opening and closing prevents the flow from returning from the nozzle 7 side to the pressurizing chamber 3 side.

At the lower end of the pressurizing section 1, a valve seat 25 ', which is a boundary wall between the pressurizing chamber 3 and the oil passage 9, is attached. A communication hole 25a 'that connects the chamber 3 side and the oil passage 9 side is formed. A first valve 51 and a second valve 5 are provided in a valve chamber 9a at the upper end of the oil passage 9 located below the valve seat 25 '.
2 is installed therein.

The first valve 51 is formed in a substantially ring shape in which a storage hole 51a is formed in a central portion.
A second valve 52 having a substantially cylindrical shape with a lower end closed is slidably inserted into 1a. First valve 51
A gap Lv is provided in the vertical direction between the first valve 51 and the valve chamber 9a, and the first valve 51 can be moved up and down within the range of the gap Lv. The upper surface of the first valve 51 is formed on a sealing surface 51c, and when the first valve 51 moves upward, the sealing surface 51c comes into contact with the valve seat 25 'to close the communication hole 25a', and The space between the oil passage 9 and the oil passage 9 is closed and divided. An oil passage 61 that connects the pressurizing chamber 3 side and the oil passage 9 side is formed at a substantially central portion of the valve seat 25 '.

A spring 23 is interposed between the second valve 52 inserted into the storage hole 51d of the first valve 51 and the valve seat 25 ', and the second valve 52 is attached downward by the spring 23. It is being rushed. A gap Sr is provided in the up-down direction between the valve seat 25 'and the second valve 52, and the second valve 52 is vertically movable within the range of the gap Sr. The second valve 52 has an oil passage 62 communicating the pressurizing chamber 3 side and the oil passage 9 side of the second valve 52.
Are formed. The gap Sr is equal to or larger than the gap Lv.

The check valve 50 constructed as described above
In, from the state where the inside of the pressurizing chamber 3 is not pressurized,
When the pressure in the pressurizing chamber 3 rises, the pressure causes the first valve 51 to move downward (toward the oil passage 9), separating the sealing surface 51c and the valve seat 25 ', and
And the oil passage 9 communicate with each other, and the fuel in the pressurizing chamber 3 flows into the oil passage 9. Further, when the pressurized state is released by the pressurizing chamber 3 communicating with the oil supply hole 4 after the end of the fuel injection, the first valve 21 moves upward due to the residual pressure from the nozzle 7 side, and the first valve 21 moves to the sealing surface 51c. The valve seat 25 ′ comes into contact with the oil passage 9.
Is closed.

Further, the pressure on the oil passage 9 side is larger than the urging force of the spring 23, and the pressure causes the second valve 22 to move toward the pressurizing chamber by the gap Sr. When the second valve 22 moves toward the pressurizing chamber 3, the volume of the oil passage 9 closer to the nozzle 7 than the check valve 20 increases by the volume of the moved second valve 22, and the nozzle increases by the increased volume. 7 and oil passage 9
The residual pressure of the fuel remaining inside will decrease.

In the unit injector having such a configuration, as in the case of the unit injector shown in FIGS. 1 to 3, the residual pressure of the fuel on the nozzle 7 side when the engine speed is low is reduced by the engine speed. As shown in FIG. 4, the change in the fuel injection amount with respect to the engine speed in the small-injection range at low engine speeds equal to or lower than the idle engine speed N ₀ can be gradually increased. Therefore, the same effect as in the case of the unit injector described above can be obtained.

Furthermore, the second valve 52 is inserted and fitted.
Since it is formed in a simple shape, the cost of parts and the number of assembling steps can be reduced and the cost can be reduced. Further, the height of the check valve 50 itself can be further reduced, and the height of the unit injector can be further reduced.

In the unit injector, since the propagation of the pressure wave due to the oil supply of the plunger 2 is directly transmitted to the nozzle 7 because it has no injection pipe, the injection pressure sharply increases from the start of injection. The characteristic is that the injection rate at the initial stage of the injection is high. In recent years, it has been required to reduce NOx in exhaust gas. However, when the injection rate in the early stage of injection is high, such as in a unit injector, the combustion temperature rises sharply. It will be difficult. Therefore, in the present invention, the unit injector is configured as follows to suppress the injection rate at the initial stage of injection, lower the combustion temperature at the start of combustion, and reduce NOx.

That is, in the unit injector shown in FIG. 8, a pressure suppressing section 80 for suppressing the injection rate at the initial stage of injection is interposed between the pressurizing chamber 3 and the oil passage 9 of the unit injector shown in FIG. It was done. In the pressure control unit 80, a communication passage 80a and an additional chamber 80b are formed.
The pressurizing chamber 3 and the oil passage 9 are communicated by the communication passage 80a,
A check valve 10 for preventing a flow from returning from the nozzle 7 to the pressurizing chamber 3 between the communication passage 80a and the oil passage 9
Is interposed.

An additional chamber 80 provided downstream of the pressurizing chamber 3
The end of the pressure chamber 3 on the side of the pressure chamber 3 communicates with the pressure chamber 3, and the end of the additional chamber 80 b on the side of the nozzle 7 is connected to the low-pressure circuit 85. Further, a piston 81 is provided in the additional chamber 80b so as to be slidable up and down, and the piston 81 is urged toward the pressurizing chamber 3 by a spring 82.

The pressurizing chamber 3 and the low-pressure circuit 85 communicated with each other by the additional chamber 80b are separated by a piston 81.
A gap Sp is provided between the piston 81 urged toward the pressurizing chamber 3 by the spring 82 and the lower end of the additional chamber 80b (the end on the low-pressure circuit 85 side). And the additional room 80
When pressure is applied to the pressure chamber 3b from the pressure chamber 3 side, the pressure allows the piston 81 to move toward the low pressure circuit 85 against the urging force of the spring 82 within the range of the gap Sp. I have.

In the unit injector provided with the pressure control unit 80 configured as described above, when the plunger 2 descends and the inside of the pressurizing chamber 3 is pressurized, the fuel in the pressurizing chamber 3 passes through the communication passage 80a. Through the oil passage 9 through
Due to the pressure in the pressurizing chamber 3, the piston 81 in the additional chamber 80b
Moves to the low voltage circuit 85 side. Then, the volume of the space on the pressurizing chamber 3 side in the additional chamber 80b is larger than that of the piston 81 in the additional chamber 80b by an amount corresponding to the movement of the piston 81 to the low-pressure circuit 85, and the fuel in the pressurizing chamber 3 is increased by the increased volume. Additional room 80
b.

That is, when the fuel in the pressurizing chamber 3 is pressurized and the oil supply to the nozzle 7 is started, the fuel in the pressurizing chamber 3 leaks into the additional chamber 80b, Since it is necessary to pressurize the fuel flowing into the additional chamber 80b in addition to the fuel sent to the nozzle 7, the increase in the injection pressure at the start of the injection is suppressed, and the injection rate at the beginning of the injection is reduced. be able to.

[0040] For example, as shown in FIG. 9, in the injection rate curve P ₀ when not provided unit pressure controller 80 as the injector of Figure 10, substantially linearly injection rate from the start of injection abruptly It is rising and growing. On the other hand, in the injection rate curve P ₁ when the pressure control unit 80 is provided as in the unit injector of FIG. 8, the injection rate increases near the cam angle θ ₁ due to the movement of the piston 81 of the additional chamber 80 b. It can be seen that is suppressed. As described above, by suppressing the increase in the injection rate at the beginning of the injection to suppress the injection rate, the combustion temperature at the start of the combustion can be reduced, and the NOx can be reduced.
The degree of suppression of the injection rate can be arbitrarily changed by changing the size of the gap Sp, which is the sliding stroke of the piston 81, and the setting of the spring 82.

[0041]

As described above, the present invention has the following advantages. That is, a check valve for opening and closing an oil passage communicating the pressurizing chamber and a nozzle located on the downstream side of the pressurizing chamber is slidably provided in the oil passage. A valve, and a second valve slidably inserted from the nozzle side into the first valve, a communication path is provided in the first valve, and an orifice is formed in the second valve. A biasing member is interposed between the second valve and the second valve to bias the first valve toward the pressurizing chamber and bias the second valve toward the nozzle. In the region of small injection at low rotation speed,
The change in the fuel injection amount with respect to the rotation speed can be made gentle. This makes it possible to make uniform the injection amount between the cylinders easily without making fine adjustments and the like, thereby preventing problems such as hunting and engine stall. Can be reduced. Further, since the urging member of the first valve and the urging member of the second valve are shared, it is possible to improve the check valve function while suppressing the number of parts. Furthermore, the second valve having a so-called suction effect
By forming the check valve by inserting it into the flat first valve having a low height, the height of the check valve itself can be suppressed, and the height of the unit injector can be reduced. As a result, the mountability of the engine is improved, and problems such as plunger sticking can be prevented.

Further, a check valve for opening and closing an oil passage communicating the pressurizing chamber and a nozzle located downstream of the pressurizing chamber is slidably provided in the oil passage. A first valve having a substantially ring shape, and a second valve slidably inserted into the first valve. The first valve is provided on a boundary wall between the pressurizing chamber and the oil passage. A communication path for communicating the pressurizing chamber and the oil passage when the valve is closed, an orifice is formed in the second valve, and the second valve is urged toward the nozzle by an urging member. In addition to the effect of
The following effects are obtained. That is, since the first valve into which the second valve is inserted and the first valve is formed in a simple and simple shape such as a substantially ring shape having a small plate pressure, the cost of parts and the number of assembling steps can be reduced to reduce costs. Can be. In addition, the height of the check valve itself can be further reduced, and the height of the unit injector can be further reduced.

Further, an additional chamber is formed downstream of the pressurizing chamber, and a piston is slidably provided in the additional chamber, and the piston is attached to the pressurizing chamber by an urging member. As a result, the increase in injection pressure at the start of injection can be suppressed, the injection rate at the beginning of injection can be suppressed low, the combustion temperature at the start of combustion can be reduced, and NOx can be reduced.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a unit injector of the present invention.

FIG. 2 is a side sectional view showing a check valve unit of the unit injector.

FIG. 3 is a plan view of the same.

FIG. 4 is a diagram showing a change in a fuel injection amount with respect to an engine speed in a unit injector using the check valve of FIGS. 2 and 3;

FIG. 5 is a side sectional view showing another embodiment of the unit injector.

FIG. 6 is a side sectional view showing a check valve used in the unit injector of FIG.

FIG. 7 is a plan view of the same.

FIG. 8 is a view showing a third embodiment of the unit injector.

9 is a diagram showing a relationship between a cam angle and an injection rate in the unit injector of FIG.

FIG. 10 is a view showing a conventional unit injector.

FIG. 11 is a diagram showing a change in a fuel injection amount with respect to an engine speed in a conventional unit injector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressurizing part 2 Plunger 3 Pressurizing chamber 7 Nozzle 9 Oil passage 20 Check valve 21 First valve 22 Second valve 23 Spring 32 Orifice

Claims (3)

[Claims] A first valve that opens and closes an oil passage communicating the pressurizing chamber and a nozzle positioned downstream of the pressurizing chamber, the first valve being slidably provided in the oil passage; A second valve slidably inserted from the nozzle side into the first valve, a communication path is provided in the first valve, an orifice is formed in the second valve, and the first valve and the second valve are formed. And a biasing member interposed between the first injector and the second injector to bias the first valve toward the pressurizing chamber and the second valve toward the nozzle. 2. A substantially ring-shaped first valve slidably provided in the oil passage for opening and closing an oil passage communicating the pressurizing chamber and a nozzle located downstream of the pressurizing chamber. A valve, and a second valve slidably inserted into the first valve. The pressure chamber is provided on the boundary wall between the pressure chamber and the oil passage when the first valve is closed. A unit injector, comprising: a communication passage communicating the oil passage and an oil passage; an orifice formed in the second valve; and the second valve being urged toward the nozzle by an urging member. 3. An additional chamber is formed downstream of the pressurizing chamber, a piston is slidably provided in the additional chamber, and the piston is urged toward the pressurizing chamber by an urging member. Unit injector.