JPS623134A - Fuel injection controller for internal-combustion engine - Google Patents

Abstract

PURPOSE:To enable employment of small Piezo-electric element by communicating the pressurizing chamber of fuel supply pump with an overflow control valve to be controlled through a piezoelectric element thereby controlling overflow from the pressurizing chamber thus controlling the fuel injection timing. CONSTITUTION:The pressurizing chamber 42 of fuel supply pump 30 where a rotary/reciprocal plunger 41 is inserted into the housing 40 having a pressurized fuel flow-out port 45 to be communicated with a fuel injection valve is communicated through an overflow path 56 with an injection timing control valve 32. The control valve 32 is comprising an overflow control valve 52 having a large diameter section 53 slidable in the small diameter hole 50 and a valve body 54 for opening/closing the coupling section between the small diameter section 50 and the large diameter hole 51 while an overflow chamber 55 is formed between the large diameter section 53 and the valve body 54. The operation of the overflow control valve 52 is controlled through a control rod 64 by increasing/decreasing the hydraulic pressure in the pressurizing chamber 70 by means of a hydraulic piston 67 to be advanced/retracted through a drive unit 63 thus to control overflow of said chamber 42.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a fuel injection control device for an internal combustion engine.

BACKGROUND OF THE INVENTION Fuel injection valves using piezoelectric elements are known to perform fuel injection control with good responsiveness in internal combustion engines, especially diesel engines (Japanese Patent Laid-Open No. 60-17250 or No. 60-1369). (see publication). When a voltage is applied to a piezoelectric element, it expands in the axial and linear directions, and the time from application of voltage to expansion is 50 minutes.
Since it is an extremely short time of 100 μsec from μfl@e, fuel injection control with good responsiveness becomes possible by utilizing the expansion action of the piezoelectric element. Therefore, in the 1980s,
In the fuel injection valve described in Publication No. 17250, the fuel pressure of high-pressure fuel acting on the pressure-receiving surface of the needle is increased by the expansion action of a piezoelectric element to open the needle, thereby injecting fuel. . On the other hand, the fuel injection valve described in Japanese Patent Application Laid-Open No. 60-1369 has no
.

High-pressure fuel is placed on the needle end face opposite to the through hole.
The pressure is applied, and the pressure of the high-pressure fuel acting on the end face of the needle is reduced by the contraction of the piezoelectric element, thereby opening the needle, thereby injecting fuel.

Problems to be Solved by the Invention However, these fuel injection valves have a structure in which high fuel pressure acts directly on the piezoelectric element, so a large piezoelectric element is required to withstand the high fuel pressure. There is a problem in that power consumption increases accordingly.

Furthermore, in the fuel injection valve described in Japanese Patent Application Laid-Open No. 60-1369, high-pressure fuel is guided onto the end face of the needle through a gap around the needle, and the pressure of this high-pressure fuel is temporarily reduced. I'm trying to open the needle properly. However, when the fuel pressure becomes high, as soon as the fuel pressure acting on the needle end surface is reduced, the high pressure fuel is guided onto the needle end surface through the gap around the needle, so that the needle opens immediately after the needle is opened. There is a problem in that when the valve is closed and the fuel actually becomes under high pressure, fuel injection control cannot be performed.

In addition, in these fuel injection valves, injection is controlled by attaching a piezoelectric element to each fuel injection valve and controlling the piezoelectric element for each fuel injection valve, so variations in the characteristics of the piezoelectric element may occur. However, there is a problem in that the injection amount varies from fuel injection valve to fuel injection valve.

Means for Solving the Problems In order to solve the above problems, according to the present invention, fuel pressurized in the pressurizing chamber of the fuel supply pump is supplied to the fuel injection valve, and the pressurized fuel is supplied from the fuel injection valve. In a fuel injection control device configured to inject fuel, a pressurizing chamber is connected to an overflow control valve controlled by a piezoelectric element, and the overflow control valve controls overflow of fuel from the pressurizing chamber. The fuel injection timing is controlled.

Embodiment Referring to FIG. 2, 1 is a fuel injection valve, 2 is a fuel injection valve main body, 3 is a spacer, 4 is a nozzle, and 5 is a nozzle for fixing the spacer 3 and the nozzle 4 to the fuel injection valve main body 2. In the holder, 6 indicates a fuel inlet, and 7 indicates a nozzle hole. A needle 8, a pressure pin 9, and a control rod 10 arranged in series are slidably inserted into the nozzle 4, spacer 3, and fuel injection valve body 2. The needle 8 has a conical pressure receiving surface 11 formed in its middle portion, and a needle pressurizing chamber 12 is formed around the pressure receiving surface 11. This needle pressurizing chamber 12 is connected to a fuel inlet 6 via a fuel passage 13 on the one hand.
On the other hand, it is connected to the nozzle hole 7 via an annular fuel passage 14 formed around eight circumferences of the needle. The pressure bottle 9 that comes into contact with the upper end surface of the needle 8 has an enlarged part 15, and a compression spring 16 is disposed between the enlarged part 15 and the fuel injection valve main body 2.
is inserted. Therefore, the needle 8 is always urged in the valve closing direction by the spring force of the compression spring 16.

A large diameter hole 17 and a small diameter hole 18 are formed in the fuel injection valve body 2 and are aligned with each other, and the upper end of the control rod 10 projects into the small diameter hole 18 . A pressure receiving piston 19 is in contact with the upper end of the control rod 10 .

On the other hand, a large-diameter piston 20 and a small-diameter piston 21 that are integrally formed are slidably inserted into the large-diameter hole 17 and the small-diameter hole 18, respectively, and these large-diameter piston 20 and small-diameter piston 21 increase the hydraulic pressure. A servo piston 22 is formed for this purpose. Small diameter piston 21 and pressure receiving piston 19
A control oil pressure chamber 23 is formed therebetween, and a control oil introduction chamber 24 is formed above the large diameter piston 20.

As shown in FIG. 2, a fuel supply pump 30 and a control oil supply pump 31 are provided for supplying fuel and control oil to the fuel injection valve 1. The fuel supply pump 30 is connected to the fuel inlet 6 of the fuel injection valve 1 via an injection timing control valve 32 and a constant volume accumulator 33. On the other hand, the control oil supply pump 31 is connected to the control oil introduction chamber 24 of the fuel injection valve 1 via a pressure regulating valve 34 on the one hand, and to the control oil pressure chamber 23 via a port 25 that opens into the control oil pressure chamber 23 on the other hand. Concatenated. The control oil supply pump 31 may not be a vane pump, for example, and the pressure regulating valve 34 returns a part of the pressurized control oil discharged from the control oil supply pump 31 to the suction port of the control hydraulic pump 31, thereby increasing the control oil introduction chamber 24. and controls the pressure of control oil supplied into the control hydraulic chamber 23. Note that fuel is used here as control oil. The fuel supply pump 30, the injection timing control valve 32, the control oil supply pump 31, and the pressure regulating valve 34 are common to all the fuel injection valves 1, and therefore, they are provided individually.

As shown in FIG. 2, a compression spring 26 is inserted between the large diameter piston 20 and the fuel injection valve body 2.

When the pressure in the control oil introduction chamber 24 is low, the servo piston 22 does not move down due to the spring force of the compression spring 26, and at this time the servo piston 22 is in the position shown in FIG. Therefore, at this time, the control oil pressure in the control oil pressure chamber 23 acts on the pressure receiving piston 19.

The control hydraulic pressure acting on the pressure receiving piston 19 is controlled by the control rod 10.
and is applied to the needle 8 via the pressure pin 9. Therefore, a force in the needle closing direction due to the compression spring 16 and a force in the needle closing direction due to the control oil pressure act on the needle 8. In this way, when the control oil pressure increases, the valve opening pressure of the needle 8 changes, and the fuel injection rate changes. Control oil introduction chamber 24
When the internal pressure is low, that is, when the control oil pressure regulated by the pressure regulating valve 34 is low, the compression spring 2
The servo piston 22 does not descend due to the force of the spring 6, and therefore, at this time, the valve opening pressure of the needle 8 is an increase in the control oil pressure in the control oil pressure chamber 23, that is, the control oil pressure regulated by the pressure regulating valve 34. It increases with the increase in size. On the other hand, when the control oil pressure in the control oil introduction chamber 24 becomes high, the servo piston 22 descends against the compression spring 26 and closes the valve boat 25. The control oil pressure also becomes higher than the control oil pressure in the control oil introduction chamber 24. Next, as the control oil pressure in the control oil introduction chamber 24 increases, the control oil pressure in the control oil pressure chamber 23 increases. Therefore, the valve opening pressure P of the needle 8 is as shown in FIG.
When it exceeds , it rises rapidly.

By the way, the optimum needle opening pressure P for the engine load has the same shape as the curve shown in FIG. That is, the optimal valve opening pressure p
When the engine load is small, Fi gradually increases as the engine load increases, and when the engine load is large, it increases rapidly as the engine load increases. Therefore, when using the fuel injection valve 1 shown in FIG. 2, the optimum valve opening pressure P can be secured by controlling the control oil pressure in the control oil introduction chamber 24 in proportion to the engine load, and thus the needle opening pressure Easy control of P row 7! - You can do it. In addition, the servo piston 22
By using this, a large valve opening pressure can be applied to the needle 8 with a control oil pressure lower than K, and there is an advantage that the control oil supply pump 31 can be a small one and a low pressure one.

FIG. 1 shows a portion of the fuel supply pump 30 and the injection timing control valve 32. As shown in FIG. The fuel supply pump 30 has a housing 40 thereof.
a plunger 4 slidably and rotatably inserted therein;
1 and a pressurizing chamber 42 defined by a plunger 41. The plunger 41 is reciprocated in the axial direction while being rotated by the engine via a drive mechanism (not shown).

A pressurized fuel outflow hole 43 is formed inside the plunger 41, and a fuel inflow groove 44 is formed on the outer peripheral surface of the plunger 41. The housing 40 also includes a pressurized fuel outlet hole 43.
A pressurized fuel outflow boat 45 that can communicate with the fuel injector 1 and a fuel inflow port 46 that can communicate with the fuel inflow groove 44 are formed, and the pressurized fuel outflow boat 45 connects to the fuel inlet 6 of the fuel injection valve 1 via the achievator 33. Concatenated. Plunger 4
1 rotates and descends, the fuel inlet port 46 opens into the fuel inlet groove 44, and fuel is supplied into the pressurizing chamber 42. Next, when the plunger 41 rotates and moves up, the fuel inlet port 46 is closed by the plunger 41, and as the plunger 41 moves up, the fuel in the pressurizing chamber 42 is pressurized. Next, when the pressurized fuel outflow hole 43 communicates with the pressurized fuel outflow boat 45, the pressurized fuel in the pressurized chamber 42 flows through the pressurized fuel outflow hole 43, the pressurized fuel outflow boat 45. The fuel is supplied into the needle pressurizing chamber 12 via the achievator 33, the fuel inlet 6, and the fuel passage 13. This pressurized fuel
, the material acts on the pressure receiving surface 11 of the needle 8 and the needle
A force in the needle valve opening direction is applied to the needle □''8, and when this force in the needle valve opening direction exceeds the needle valve opening pressure, fuel is injected from the nozzle hole 7.

Note that the double valve opening pressure at this time is controlled by the pressure regulating valve 34 as described above.

On the other hand, as shown in FIG. 1, the injection timing control valve 32 has a small diameter hole 50 and a large diameter hole 51 arranged in alignment therein,
An overflow control valve 52 is slidably inserted into the small diameter hole 50 . The overflow control valve 52 has a large diameter portion 53 that is slidable within the small diameter hole 50, and a large diameter portion 53 that is slidable within the small diameter hole 50 and the large diameter hole 5.
1 and a valve body 54 that can open and close the connecting portion with 1. An overflow chamber 55 is formed between the large diameter portion 53 and the valve body 54, and this overflow chamber 55 is connected to the pressurizing chamber 42 via an overflow passage 56. On the other hand, a fuel discharge chamber 57 is formed in the large diameter hole 51, and this fuel discharge chamber 57 is connected to the fuel inflow hole 46 via a fuel return passage 58. Large diameter portion 5 of overflow control valve 52
3, a spring chamber 59 is formed in the small diameter hole 50 on the opposite side to the overflow chamber 55, and an overflow control valve 5 is formed in the spring chamber 59.
Two pressing compression springs 60 are inserted. The pressurized fuel leaking into the spring chamber 59 is discharged into the fuel discharge chamber 57 via a fuel discharge passage 61 formed in the overflow control valve 52 .

On the other hand, a spacer 62 is fitted into the injection timing control valve 32, and this spacer 62 is fixedly supported within the injection timing control valve 32 by a driving device 63 fixed to one end of the injection timing control valve 32. A control rod 64 is slidably inserted into the spacer 62, and inside the control rod 64 is a fuel discharge passage 61 formed in the overflow control valve 52 and a fuel discharge chamber 57.
A fuel discharge path 65 is formed which communicates with the two. One end of the control rod 64 abuts the overflow control valve 52, and the other end of the control rod 64 protrudes from the line spacer 62. The drive device 63 has a hydraulic piston 67 slidably arranged in its housing 66, and a piezoelectric element 6 is disposed between the hydraulic piston 67 and the housing 66.
8 is inserted. This piezoelectric element 68 has a laminated structure in which a large number of thin plate-like piezoelectric elements are laminated, and when a voltage is applied to this piezoelectric element 68, the piezoelectric element 6
8 produces longitudinal strain due to the electrostrictive effect, that is, it extends in the longitudinal direction. Although the amount of elongation is a small amount, for example, about 50 μm, the response is extremely good, and the response time from application of voltage to elongation is about 80 μsec. When the voltage application is stopped, the piezoelectric element 68 immediately contracts. As shown in FIG. 1, a disc spring 69 is inserted between the hydraulic piston 67 and the housing 66.
Hydraulic power by spring force.

The piston 67 is pressed toward the piezoelectric element 68. A pressurizing chamber 70 is formed between the hydraulic piston 67 and the spacer 62, and the control rod 64 projects into this pressurizing chamber 70. A fuel passage 71 is formed within the hydraulic piston 67.
On the one hand, this fuel passage 71 is connected to the inside of the pressurizing chamber 70 via a check valve 72 that allows flow only toward the pressurizing chamber 70,
On the other hand, it is connected into the fuel discharge chamber 57 via a fuel passage 73 formed in the housing 66 and the spacer 62 .

When the application of voltage to the piezoelectric element 68 is stopped, the piezoelectric element 68 contracts, and the hydraulic piston 67 moves to the left by the spring force of the disc spring 69. At this time, the overflow control valve 52 is operated by the spring force of the compression spring 60.
At the same time, it moves to the left, and the valve body 54 opens to communicate the overflow chamber 55 with the fuel discharge chamber 57. Therefore, even if the plunger 41 of the fuel supply pump 30 rises at this time, the pressure chamber 42
Since the fuel in the pressurizing chamber 42 is discharged into the fuel discharge chamber 57 via the overflow passage 56 and the overflow chamber 55, the fuel in the pressurizing chamber 42 is not pressurized, and the plunger 41 is free from pressure. Even if the pressurized fuel outflow hole 43 communicates with the pressurized fuel outflow port 45, the fuel injection valve: 1'', 1.
. 7ゎEnglish is long. □1 Next, when a voltage is applied to the piezoelectric element 6B, the piezoelectric element 68 expands, and as a result, the hydraulic piston 67 moves to the right, so that the fuel in the pressurizing chamber 70 is pressurized. Pressurized chamber 7
When the fuel pressure in the 0 increases, the control rod 64 moves to the right, which causes the overflow control valve 52 to move to the right against the compression spring 60, causing the valve body 54 to move as shown in FIG. The overflow chamber 55 is closed. Therefore, at this time, when the plunger 41 of the fuel supply pump 30 rises, the fuel in the pressurizing chamber 42 is pressurized, and when the fuel pressure in the needle pressurizing chamber 12 of the fuel injection valve 1 increases, fuel injection is performed. On the other hand, when the voltage application to the piezoelectric element 68 is stopped, the piezoelectric element 68
shrinks, and the aforementioned °゛°°2″“”′°”°“″”°”
.

Injection stops. At this time, the fuel in the fuel discharge chamber 57 flows through the fuel passages 73 and 72 and the check valve 72 into the pressurizing chamber 70.
will be replenished within.

As described above, the responsiveness of the busy piezoelectric element 68 is fast, and therefore the fuel injection timing and the fuel injection completion timing can be accurately controlled. Further, when the present invention is applied to, for example, a four-cylinder diesel engine, four pressurized fuel outflow boats 45 shown in FIG. 1 are formed on the housing 40 at equal angular intervals, and each pressurized fuel outflow boat 45 is It is connected to each fuel injection valve 1.

Further, in this case, the plunger 41 is reciprocated four times during one rotation. Therefore, regardless of the number of fuel injection valves 1, the fuel supply pump 30 and the injection timing control valve 32 can be provided on the negative side.

As shown in FIG. 2, the injection timing control valve 32 and the pressure regulating valve 34 are connected to an electronic control unit 80 and are controlled by the output signal of the electronic control unit 80. The electronic control unit 80 is a digital combination.
A ROM (read-on memory) 82, a RAM (random access memory) 83 and a CPU (microprocessor) 84 are interconnected by a bidirectional bus 81. An input boat 85 and an output boat 86 are provided. A rotation speed sensor 87 is connected to the human-powered boat 85, and a load sensor 88 and a water temperature sensor 89 are further connected to the input boat 85 via corresponding human-power converters 90 and 91, respectively. Meanwhile, the output boat 86 is connected to the injection timing control valve via a corresponding drive circuit 92,93.

32 piezoelectric elements 68. and the solenoid of the pressure regulating valve 34. The rotational speed sensor 87 generates a number of output pulses proportional to the engine rotational speed,
The engine speed is calculated from this output pulse. The load sensor 88 generates an output voltage proportional to the amount of depression of the accelerator pedal, and the load is calculated from this output voltage. Water temperature sensor 89 generates an output voltage proportional to the engine cooling water temperature. The electronic control unit 80 controls the injection timing control valve 32 and the pressure regulating valve 34 to achieve the optimum injection timing and optimum needle opening pressure based on the engine speed, load, and water temperature.

As described above, by using the piezoelectric element 68 to control the injection timing control valve 32, pilot injection becomes possible. The pilot injection control will be explained below.

Referring to FIG. 2, a needle lift detector 94 is disposed within the spacer 3 of the fuel injection valve 1.

This needle lift detector 94 is located at the enlarged portion 1 of the pressure pin 9.
5 and the needle lift detector 94, that is, an output voltage proportional to the lift of the needle 8 is generated. A needle lift detector 94 is connected to one input terminal of a comparator 96 via an AD converter 95. A reference voltage is applied to the other input terminal of the comparator 96, and the output terminal of the comparator 96 is connected to the human-powered boat 85.
connected to. When the output voltage of the needle lift detector 94 becomes larger than a predetermined voltage, that is, when the lift amount of the needle 8 becomes larger than the predetermined lift amount, the output voltage of the comparator 96 increases. Becomes a high level.

Next, fuel injection control when performing pilot injection will be described with reference to FIGS. 5 and 6. Referring to FIG. 5, first, in step 100, the output signal of the rotation speed sensor 87 representing the engine speed N, the output signal of the load sensor 88 representing the load, and the output signal of the water temperature sensor 89 representing the water temperature T are obtained. It's crowded. Then step 10
In step 1, it is determined whether the operating state is such that pilot injection is required, and if pilot injection is required, the process proceeds to step 102. In step 102, the optimum pilot injection interval τa is calculated from the engine speed N, load and water temperature T, and then in step 103 a pilot flag is set. Next, in step 104, the main injection start timing τC is determined based on the engine speed N, negative load, and water temperature T.
and the main injection completion time fd is calculated, and step 105
τa and τC9τd are output to the output port 86.

When the pilot injection starts τ breath, the PC display in Fig. 4(b)
A voltage E is applied to the piezoelectric element 68 so as to cause the needle 8 to move as shown in FIG. rose.

However, the output voltage V of the needle lift detector 94 increases. When the needle 8 rises, pilot injection is started. When the output voltage V of the needle lift detector 94 exceeds a predetermined voltage vO, the output voltage of the comparator 96 becomes high level, and when the output voltage of the comparator 96 becomes high level, the interrupt routine shown in FIG. 6 is executed. be done.

In FIG. 6, first, in step 110, it is determined whether the pilot flag is set.

When the pilot flag is set, the process proceeds to step 111, where the application of voltage to the piezoelectric element 68 is stopped, and the pilot injection is stopped. Next, in step 112, the pilot flag is reset. Next is the main injection start timing τ.

Then, as shown in FIG. 4(b), the piezoelectric element 68
A voltage is applied to and main injection is performed. At this time, since the pilot flag has been reset, the main injection is continued at the main injection completion time τdt even if the output voltage V of the needle lift detector 94 exceeds Vo.

Effects of the Invention A structure in which the piezoelectric element pressurizes the fuel is not adopted, and the overflow control valve is controlled by the piezoelectric element, so that high fuel pressure is not applied to the piezoelectric element. There is no. Therefore, a small piezoelectric element can be used, thus reducing power consumption.

Further, even when a plurality of fuel injection valves are provided, the fuel injection timing of each fuel injection valve can be controlled by one overflow control valve, so that the injection control device can be simplified.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of a part of the fuel supply pump and the injection timing control valve, Fig. 2 is an overall view of the fuel injection control device, and Fig. 3 is a side sectional view of a part of the fuel supply pump and the injection timing control valve.
FIG. 4 is a diagram showing the needle opening pressure, FIG. 4 is a diagram showing pilot injection control, and FIGS. 5 and 6 are flowcharts for the first time to execute pilot injection control. 30...Fuel supply pump, 32...Injection timing control valve, □41...Plunger, 42...
Pressurized chamber, 43... Pressurized fuel outflow hole, 52... Overflow control valve, 55... Overflow chamber, 56... Overflow path, 64...
- Control rod, 67... Hydraulic piston, 68... Piezo piezoelectric element, 2o... Pressurizing chamber. Figure 5 Figure 6

Claims (1)

[Claims] In a fuel injection control device that supplies pressurized fuel in a pressurizing chamber of a fuel supply pump to a fuel injection valve and injects the pressurized fuel from the fuel injection valve, the pressurizing chamber is controlled by a piezoelectric element. A fuel injection control device for an internal combustion engine, which is connected to a controlled overflow control valve, and the overflow control valve controls overflow of fuel from a pressurizing chamber to control fuel injection timing.