JPH0459465B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device for an internal combustion engine, particularly a diesel engine.

As a conventional fuel injection device, for example, the U.S. patent
There is one described in the specification of No. 3516395. As shown in FIG. 1, this device includes a fuel tank 1, a fuel pump 2, an injection unit 3, and a
and a piston stroke control means 4. The injection unit 3 includes a servo piston 6 slidably supported within a large-diameter cylinder 5, a pump piston 8 slidably supported within a small-diameter cylinder 7, and a pump piston 8 such that both pistons 6, 8 are in contact with each other. It has a spring 9 that urges the
A three-way switching valve 11 is connected to the servo pressure chamber 10 of the large diameter cylinder 5, and a solenoid valve 13 and a check valve 14 are connected to the pump working chamber 12 of the small diameter cylinder 7.
Fuel under a predetermined pressure is supplied from the fuel pump 2 through the respective fuel pumps. Further, the pump working chamber 12 communicates with an injection nozzle (not shown). Further, reference numeral 15 indicates a leak chamber of the large diameter cylinder 5, and fuel leaked into this leak chamber 15 is returned to the fuel tank 1. The solenoid valve 13 is controlled to open and close by a control circuit 16, and the three-way switching valve 11 selectively communicates the servo pressure chamber 10 with the fuel tank 1 or the fuel pump 2. In addition,
17 is a pressure regulating valve. The solenoid valve 13, control circuit 16, fuel pump 2, and check valve 14 described above collectively constitute a piston stroke control means 4 for controlling the strokes of the pistons 6, 8 of the injection unit 3.

Therefore, in such a fuel injection device, fuel pressurized by the fuel pump 2 is supplied to the servo pressure chamber 10 via the three-way switching valve 11 on the one hand.
on the other hand, the pump working chamber 1 via the solenoid valve 13.
The fuel in the pump working chamber 12 is increased in pressure in proportion to the pressure receiving area of the servo piston 6 and the pump piston 8, and then injected from the injection nozzle.

However, in such a conventional fuel injection device, the supply of fuel to the servo pressure chamber 10 is controlled by the three-way switching valve 11, so in a small direct injection diesel engine, especially during high-speed operation, , when repeating fuel injection at high frequency,
The following problems occurred. That is, at the time of fuel injection, it is not possible to make a large difference between the pressure inside the servo pressure chamber 10 and the supplied fuel pressure (if these pressure differences are made large, if the supplied fuel pressure is constant, the servo pressure chamber 10 (as a result, the pressure in the pump working chamber 12 does not increase), the switching valve 11 becomes large, or the sleeve valve controlled by the switching valve 11 has a large stroke. It is necessary to control the supply of fuel into the servo pressure chamber 10 through the
There were problems in that a complicated mechanism was required or high-speed operation had to be restricted.

This invention was made in view of these conventional problems, and the supply and discharge of fuel from a fuel pump to a servo pressure chamber is switched and controlled by a high-pressure valve that responds to the opening and closing operations of a hydraulically driven control valve. By this,
The purpose is to improve operational response and enable injection control during high-speed engine operation.

The structure of the present invention includes a pump piston that is reciprocatably housed in a small-diameter cylinder and defines a pump working chamber within the cylinder, and a pump piston that is reciprocatably housed in a large-diameter cylinder so as to interlock with the pump piston. A servo piston that defines a servo pressure chamber in a large diameter cylinder, a fuel pump that supplies fuel at a predetermined pressure to these servo pressure chambers and the pump work chamber, and a valve that opens in response to the fuel pressure in the pump work chamber to supply fuel. A fuel injection device equipped with an injection nozzle that injects fuel, which has a large diameter part on one side that receives fuel pressure from the fuel pump, and which opens and closes to intermittently supply fuel from the fuel pump to the servo pressure chamber. A high-pressure valve has a seat portion for valving, a seat portion that contacts the other side of the high-pressure valve on one side and interrupts communication between the servo pressure chamber and the fuel tank, and a seat portion on the other side that is larger than the large-diameter portion of the high-pressure valve. It has a large diameter part, and when the valve is opened, the seat part communicates the servo pressure chamber and the fuel tank to close the seat part of the high pressure valve, and when the valve is closed,
a control valve whose seat part cuts off communication between the servo pressure chamber and the fuel tank and opens the seat part of the high pressure valve;
A control pressure chamber defined by a large diameter portion of the control valve and a cylinder that slidably accommodates the control valve and communicates with the fuel pump and the fuel tank; and a control pressure chamber communicating with the fuel pump. The seat section of the control valve can be opened and closed by switching between the first switching position and the second switching position where the control pressure chamber and the fuel tank are communicated, and switching the flow of hydraulic pressure in the control pressure chamber. a switching valve, and a control means for controlling the timing of switching the switching valve to the first and second switching positions and the time for which the switching valve is located at the first and second switching positions, respectively, the switching means is located at the second switching position. At this time, by opening the seat part of the control valve to communicate the servo pressure chamber with the fuel tank and controlling the time it remains in that position,
The amount of fuel supplied from the fuel pump to the pump working chamber is adjusted, the switching valve is switched from the second switching position to the first switching position at a predetermined timing, the seat part of the control valve is closed, and the servo is switched from the fuel pump to the first switching position. The pump working chamber is pressurized by supplying fuel to the pressure chamber, and the fuel in the working chamber is injected from the injection nozzle.

Embodiments of the present invention will be described below based on the drawings.

FIGS. 2 and 3 show an embodiment of a fuel injection device according to the present invention. First, to explain the configuration, in FIG. 2, reference numeral 21 indicates a pump nozzle which is an injection unit.
includes a large diameter cylinder 23 formed in the upper housing 22, a small diameter cylinder 25 formed in the lower housing 24, and an injection nozzle 27 integrally assembled to these housings 22 and 24 by a holder 26. have.

A servo piston 31 is slidably housed in the large diameter cylinder 23, and the servo piston 31 creates a low pressure chamber 32 at one end (lower end in the figure) of the cylinder 23, and also at the other end. A servo pressure chamber 33 is defined on each side (on the upper end side). A small diameter cylinder 25 fixed to one end side of this large diameter cylinder 23 and having a smaller diameter than the large diameter cylinder 23
A pump piston 34 disposed coaxially with the servo piston 31 is slidably housed inside. One end of the pump piston 34 defines a pump working chamber 35 within the small diameter cylinder 25, and
The other end protrudes into the large diameter cylinder 23 and comes into contact with the lower end surface of the servo piston 31. Also,
A working spring 36 is compressed in the servo pressure chamber 33, and the spring 36 causes the servo piston 31 and the pump piston 34 to reciprocate together in the vertical direction in the figure.

The injection nozzle 27 has a nozzle body 4 fixed to the lower end of the lower housing 24 by a holder 26.
1, a needle valve 42 held in a nozzle body 41 so as to be able to move up and down, and a valve spring 45 that urges the needle valve 42 via a retainer 44 in a direction to close a fuel injection hole 43 formed at the tip of the nozzle body 41. It has . The valve spring 45 is compressed into a spring chamber 47 defined by a spacer 46 on the rear end side of the needle valve 42, and a spring chamber 47 is provided between the spacer 46 and the nozzle body 41 to regulate the amount of lift of the valve 42. A stopper 48 is interposed therebetween. 4
9 is a fuel reservoir formed in the nozzle body 41, and a pressure stage of the needle valve 42 is located in this fuel reservoir 49. Further, 50 indicates a high pressure passage that communicates the fuel reservoir 49 and the pump working chamber 35.

Reference numeral 51 denotes a fuel pump that sucks up fuel from the fuel tank 52 and pressurizes it to a predetermined pressure (for example, 200 kg/cm ² ). The servo pressure chamber 33 and the pump working chamber 35 are each supplied with the air. That is, the pressurized fuel is transferred to the accumulator 54 and the pressure regulator 55.
One branch path 53 of the three-pronged fuel supply path 53 that is maintained at a predetermined pressure by
It is supplied to the high pressure passage 50 via a and to the servo pressure chamber 33 via another branch passage 53b. Further, the other branch path 53c is connected to a first port 58 of a three-way solenoid valve 57 as a switching valve. 5
Reference numeral 9 denotes a check valve disposed in the branch passage 53a, and this check valve 59 prevents the fuel from flowing back from the high pressure passage 50 to the fuel supply passage 53. A high-pressure valve 61 is interposed in the branch passage 53b, and the high-pressure valve 61 has a conical seat portion 62 that can sit on the inner wall surface of the branch passage 53b, and a conical seat portion 62 that is formed on the other side and has a free flow inside the branch passage 53b. The inserted small diameter portion 63 is formed on one side, receives fuel pressure from the fuel pump 51, and has a plurality of axial grooves 64 formed on the outer circumferential surface and is slidably supported in the branch passage 53b (in the left-right direction in the figure). and a large diameter portion 65. That is, the high pressure valve 61 opens and closes the branch passage 53b to open and close the fuel pump 51.
The supply of pressurized fuel from the servo pressure chamber 33 to the servo pressure chamber 33 is interrupted. Reference numeral 71 denotes a control valve that controls the opening and closing operation of the high-pressure valve 61, and this control valve 71 is housed in a cylinder 72 formed in the upper housing 22 so as to be slidable (moveable left and right in the figure). The cylinder 72 has a branch passage 5 formed at its right end.
3b, a first port 73 connected halfway between the high pressure valve 61 and the servo pressure chamber 33, a second port 75 formed on the right end side and connected to the fuel tank 52 via a return passage 74, and a second port 75 on the left end thereof. The second one of the three-way solenoid valve 57 is connected to the
and a third port 78 connected to port 77 . Further, a large-diameter left end portion A (its diameter is larger than the diameter of the large-diameter portion 65 of the high-pressure valve 61) as a large-diameter portion formed on the other side of the control valve 71 is located on the left end side of the cylinder 72. A control pressure chamber 79 is defined by the port 78, and a small diameter right end portion B, which serves as a seat portion, formed on one side of the control valve 71 is capable of opening and closing the first port 73. Further, the high pressure valve 61 is provided on the right end surface of the control valve 71.
The end face of the small diameter portion 63 is in contact with the end face of the small diameter portion 63 . That is,
The high-pressure valve 61 and the control valve 71 are disposed substantially on the same axis and are configured to reciprocate together as a unit by hydraulic pressure. Specifically, the seat portion (small diameter right end portion) B of the control valve 71 is in the first position when the valve is opened.
The port 73 is opened to communicate the branch passage 53b and the second port 75, and the seat portion 62 of the high pressure valve 61 is closed to cut off the communication between the branch passage 53b and the fuel supply passage 53, and the valve is closed. time, 1st port 73
The seat portion 62 of the high pressure valve 61 is blocked to block communication between the branch passage 53b and the second port 75.
The branch passage 53b and the fuel supply passage 53 are communicated with each other by opening the valve. The three-way solenoid valve 57 is
a spring 81; an armature 82 that is biased downward in the figure by the spring 81 and blocks communication between the first port 58 and the second port 77;
The armature 82 has a solenoid 83 that attracts and moves upward in the figure when energized, and the energization of the solenoid 83 is controlled by an accelerator sensor 84
The energization timing and time are computationally controlled by a control circuit 87 serving as a control means that determines the operating state of the engine based on detection signals from the crank angle sensor 85, water temperature sensor 86, and the like. Further, 88 is a third port connected to the return passage 74, and this third port 88 is connected to the second port when the solenoid 83 is energized.
It is closed by armature 82 as shown. Therefore, when the three-way solenoid valve 57 is energized, the armature 82 is switched to the first switching position and closes the third port 88, and when it is not energized, the armature 82 is switched to the second switching position and the first port 88 is closed. 58 is closed, the second port 77 and the third port 88 are connected and communicated, and as a result, the working oil pressure of the control valve 71, that is, the supply and discharge of high-pressure fuel to the control pressure chamber 79 is switched. By switching between supplying and discharging high-pressure fuel, the seat portion (small diameter right end portion) B of the control valve 71 can be moved in the left-right direction in the figure to open and close the first port 73 as described above. In addition, the return passage 74 is connected to the second port 75 of the control valve 71, and is also connected to the low pressure chamber 32, the spring chamber 47, and a relief port 91 that opens in the axially intermediate portion of the small diameter cylinder 25. It is connected. The relief port 91 is formed in the pump piston 34 so that one end can communicate with the pump working chamber 35 and the other end can communicate with a relief passage 93 that opens as an annular groove 92 in the axially intermediate portion of the piston 34. There is. That is, when the pump piston 34 is in the upper position as shown in the figure, the communication between the relief port 91 and the annular groove 92 is cut off, but when the pump piston 34 is lowered by a predetermined stroke, the communication between the relief port 91 and the annular groove 92 is interrupted. will be in communication.

Next, the effect will be explained.

3A to 3E respectively show the current value i of the solenoid 83 with respect to time t, the lift amount S of the control valve 71, the pressure P of the servo pressure chamber 32, the downward stroke amount Hp of the pump piston 34, and the needle valve 4
2 shows the relationship between the lift amount H _o .

Now, the solenoid 83 is energized until time _t1 , and as a result, as shown in FIG. 77 is connected, and the control valve 71 is opened to the first port 7 by the hydraulic pressure of the control pressure chamber 79.
3 is closed, the high pressure valve 61 opens the branch passage 53b, and the servo pressure chamber 33 is supplied with fuel at a predetermined pressure (200 kg/cm ² ). At the same time, this pressure (200 Kg/cm ² ) is also acting on the pump working chamber 35 and the fuel reservoir 49, but the needle valve 42 is not lifted by the valve spring 45, and fuel injection is not performed. .

First, at time t ₁ , when the current i to the solenoid 83 is cut off (Fig. 3a), the armature 8
2 is switched to the second switching position and the armature 82
Due to the downward movement of , the second and third ports 77 and 88 communicate with each other, and the control pressure chamber 79 communicates with the return passage 72.
After a predetermined delay time τ ₁ due to the working pressure on the large diameter portion 65 of the high pressure valve 61, the control valve 71 moves to the left at time t ₂ (FIG. 3b) (the high pressure valve 61 also moves to the left and the branch path 53b ), open the first port 73 and return passage 7
After a predetermined delay time τ ₂ has elapsed, the pressure in the servo pressure chamber 33 communicating with the servo pressure chamber 33 further decreases from the time t ₃ (FIG. 3c). Therefore, the pressure of the fuel flowing from the fuel pump 51 through the check valve 59 into the pump working chamber 35 causes the pump piston 34 to rise in FIG. 2 (FIG. 3d). That is, during the time (pulse width τp) when the armature 82 is located at the second switching position, fuel is stored in the pump working chamber 35, and this fuel becomes the injection amount. Thereafter, when the control circuit 87 energizes the solenoid 83 again at a predetermined timing _t4 after the pulse _width τp time has elapsed from the aforementioned time t1, the armature 82 is switched to the first switching position and the first and second switching positions are switched. 2 ports 58 and 77 are connected, and the control pressure chamber 79 is opened at time _t5 after a predetermined delay time _τ4 has elapsed.
communicates with the fuel pump 51 via the branch passage 53c and the fuel supply passage 53 and high pressure (200Kg/cm ² ) acts on it, so the control valve 71 moves to the right and closes the first port 73, and the high pressure valve 61 Move the seat part 62 to the right.
opens branch road 53b. As a result, the pressure in the servo pressure chamber 33 rises rapidly from time t ₆ after a predetermined delay time τ ₅ has elapsed (Fig. 3c), and the pump is pumped by a force proportional to the difference in pressure receiving area between the servo piston 31 and the pump piston 34. The piston 34 is pushed down (third
Figure d). That is, the fuel pressure in the pump working chamber 35 is increased and acts on the fuel reservoir 49, and as a result, at time _t7 after a predetermined delay time _τ6 has elapsed, the needle valve 42 is lifted and fuel injection is performed at a high pressure. Figure 3 e).
After this, when the pump piston 34 further descends, the relief passage 93 communicates with the relief port 91, and the fuel pressure in the port working chamber 35 drops rapidly. As a result, the needle valve 42 descends and the fuel injection hole 4
3 is closed and the injection ends (Fig. 3e). This injection period is indicated by τ ₈ in FIG. 3e. Note that the pump piston 34 continues to descend for a predetermined time τ ₇ , reaches the zero position (lowest position) at time t ₈ , and stops. Thereafter, the above cycle will be repeated.

The injection amount can be reduced by reducing the pulse width τp and shortening the lift time _τ8 of the needle valve 42, as shown by the broken line in FIG. Further, the injection timing may be changed by changing the energization timing _t4 to the solenoid 83. These changes are made in the control circuit 8
7, it goes without saying that the setting can be made as appropriate depending on the operating state of the engine.

As explained above, according to this invention,
A high pressure valve has a large diameter part on one side that receives fuel pressure from the fuel pump and has a seat part that interrupts communication between the fuel pump and the servo pressure chamber; A control valve is provided that has a seat part that interrupts communication between the chamber and the fuel tank, and has a large diameter part on the other side that is larger than the large diameter part of the high pressure valve, and controls the flow of fuel into and out of the servo pressure chamber. Since this is performed by opening and closing the seat portion of the control valve and the high pressure valve, the fuel supply can be controlled with a small stroke amount of the control valve. Therefore, it is possible to shorten the operation delay time of the control valve with respect to the operation of the switching valve, and it is also possible to increase the area of the control valve's seat part, as well as that of the high-pressure valve's seat part, so that the control valve's operation It has also become possible to reduce the delay time for switching valve operation, and the time for the pressure in the servo pressure chamber to rise and fall in response to the operation of the switching valve can be significantly reduced.As a result, injection control during high-speed operation has become possible due to improved operational response. . Further, since only one switching valve is provided and the control valve is operated by the switching valve, the injection device can be made smaller and lighter, and the cost of the device can be reduced. Furthermore, as a result of being able to downsize the armature, the three-way solenoid valve as a switching valve such as a solenoid can be made compact and highly responsive as a whole.

Furthermore, in the above embodiment, since the control valve and the high-pressure valve are formed from separate members, the centering accuracy between the two valves is not required to be precise, and the fuel injection device itself can be made at a very low cost due to the simplification of the assembly process. can be produced.

[Brief explanation of the drawing]

Fig. 1 is a schematic circuit diagram showing a conventional fuel injection device, Fig. 2 is a schematic overall view showing an embodiment of the fuel injection device according to the present invention, and Fig. 3 is an explanatory diagram of the operation of the same device. . 23... Large diameter cylinder, 25... Small diameter cylinder, 27... Injection nozzle, 31... Servo piston, 33... Servo pressure chamber, 34... Pump piston, 35... Pump working chamber, 51... Fuel pump , 52... Fuel tank, 57... Three-way solenoid valve,
61... High pressure valve, 62... Seat part, 63... Small diameter part, 65... Large diameter part, 71... Control valve, 79...
...Control pressure chamber, 87...Control circuit (control means), A
...Large diameter left end (large diameter part), B...Small diameter right end (seat part).

Claims (1)

[Claims] 1. A pump piston that is reciprocatably housed in a small diameter cylinder and defines a pump working chamber within the cylinder, and a pump piston that is reciprocatably housed in a large diameter cylinder and that operates in conjunction with the pump piston. A servo piston that defines a servo pressure chamber, a fuel pump that supplies fuel at a predetermined pressure to these servo pressure chambers and a pump work chamber, and an injection nozzle that opens and injects fuel in response to the fuel pressure in the pump work chamber. A fuel injection device having a large diameter portion receiving fuel pressure from a fuel pump on one side,
A high pressure valve has a seat that opens and closes to interrupt the supply of fuel from the fuel pump to the servo pressure chamber, and one side of the high pressure valve contacts the other side of the high pressure valve to interrupt communication between the servo pressure chamber and the fuel tank. The seat part has a large diameter part on the other side that is larger than the large diameter part of the high pressure valve, and when the valve is opened, the seat part communicates the servo pressure chamber and the fuel tank, and the seat part of the high pressure valve At the same time, when the valve is closed, the seat part cuts off communication between the servo pressure chamber and the fuel tank and opens the seat part of the high pressure valve, and the large diameter part of the control valve and the control valve are slid together. a control pressure chamber defined by a movably housed cylinder and communicating with the fuel pump and the fuel tank; a first switching position communicating the control pressure chamber and the fuel pump; and a control pressure chamber and the fuel tank. The seat of the control valve can be opened and closed by switching the flow of hydraulic pressure in the control pressure chamber.
a switching valve, and a control means for controlling the timing of switching the switching valve to the first and second switching positions and the time for which the switching valve is located at the first and second switching positions, respectively, the switching means is located at the second switching position. At this time, the seat part of the control valve is opened to communicate the servo pressure chamber with the fuel tank, and the amount of fuel supplied from the fuel pump to the pump working chamber is adjusted by controlling the time at which the servo pressure chamber remains in this position. , the switching valve is switched from the second switching position to the first switching position at a predetermined timing, the seat portion of the control valve is closed, and fuel is supplied from the fuel pump to the servo pressure chamber, thereby increasing the pump working chamber. A fuel injection device characterized in that the fuel in the working chamber is injected from an injection nozzle by applying pressure.