JPS62645A - Fuel injection control device for internal-combustion engine - Google Patents

Abstract

PURPOSE:To adjust an injection rate of fuel to an optimum value responding to the operating condition of an engine, by controlling a fuel pressure in a pressure accumulating chamber. CONSTITUTION:A fuel injection valve 8 is coupled to a fuel pressure accumulating pipe 11 common to cylinders through a fuel feed pipe 10. The fuel pressure accumulating pipe 11 is provided at its interior with a pressure accumulating chamber 12 with a specified volume, and fuel in the pressure accumulating chamber 12 is fed to a fuel injection valve 8 through a fuel feed pipe 10. A fuel pressure sensor is located in a fuel feed passage to control a fuel pressure in the pressure accumulating chamber depending upon an operating condition. This enables adjustment of an injection rate to an optimum value.

Description

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

[Conventional technology]

A diesel engine in which a fuel injection valve is connected to a fuel supply pump via a fuel supply passage, a pressure accumulation chamber is provided in the fuel supply passage, and the fuel accumulated in the pressure accumulation chamber is injected from the fuel injection valve by the fuel supply pump. is publicly known (
For example, see US Pat. No. 3,587,547). In this diesel engine, the fuel injection timing and fuel injection amount are controlled according to the operating state of the engine.

[Problem that the invention seeks to solve]

However, it is difficult to ensure good engine operation by controlling only the fuel injection timing and fuel injection amount in this way. In other words, when operating a diesel engine at high load, it is necessary to inject a large amount of fuel in a short period of time, and when operating at low load, it is necessary to inject a small amount of fuel little by little over a long period of time. If only the fuel injection timing and fuel injection amount are controlled, a large amount of fuel will be injected in a short period of time even during low load operation, which will result in noise during low load operation, a decrease in output, and a reduction in fuel consumption. There is a problem of increased consumption.

[Means for solving problems]

In order to solve the above problems, according to the present invention, a fuel injection valve is connected to a fuel supply pump whose discharge pressure can be controlled through a fuel supply passage, and a pressure accumulation chamber of a constant volume is provided in the fuel supply passage. A fuel pressure sensor is placed in the passage, and the discharge pressure of the fuel supply pump is controlled based on the output signal of the fuel pressure sensor so that the pressure in the fuel supply passage becomes a predetermined pressure depending on the engine operating status. I try to do that.

〔Example〕

Referring to FIGS. 1 and 2, l is the diesel engine body, 2 is the cylinder block, 3 is the cylinder head, and 4 is the cylinder block.
is a piston, 5 is a combustion chamber, 6 is an intake valve, 7 is an exhaust valve, 8
9 represents a fuel injection valve disposed within the combustion chamber 5, and 9 represents an intake manifold, the inlet portion of the intake manifold 9 being connected below the supercharger.

The fuel injection valve 8 is connected via a fuel supply pipe 10 to a fuel pressure accumulation pipe 11 common to each cylinder. The fuel accumulator pipe 11 has a pressure accumulator chamber 12 with a constant volume inside thereof, and the fuel in this pressure accumulator chamber 12 is supplied to the fuel injection valve 8 via the fuel supply pipe 10. On the other hand, the pressure accumulation chamber 12 is connected via a fuel supply pipe 13 to a discharge port of a fuel supply pump 14 whose discharge pressure can be controlled.

A suction port of the fuel supply pump 14 is connected to a discharge port of a fuel pump 15, and a suction port of the fuel pump 15 is connected to a fuel reservoir tank 16. Each fuel injection valve 8 is also connected to a fuel reservoir tank 16 via a fuel return conduit 17 . The fuel pump 15 is provided to feed the fuel in the fuel reservoir tank 16 into the fuel supply pump 14, and the fuel supply pump 14 can be used even without the fuel pump 15.
If it is possible to suck fuel into the fuel pump 15
There is no need to specifically provide this. On the other hand, the fuel supply pump 14 is provided to discharge high-pressure fuel, and the high-pressure fuel discharged from the fuel supply pump 14 is delivered to the pressure accumulation chamber 1.
Accumulated and accumulated within 2.

FIG. 3 shows a side sectional view of the fuel injection valve 8. Referring to FIG. 3, 20 is the fuel injection valve body, 2 is the nozzle, 22
23 is a spacer, 23 is a nozzle holder for fixing the nozzle 21 and spacer 22 to the fuel injection valve body 20, and 24 is a nozzle holder.
25 indicates a fuel inlet, and 25 indicates a nozzle hole formed at the tip of the nozzle 2t.The fuel injection valve body 20 includes a spacer 22, a control loft 26 arranged in series with each other in the nozzle 23, and a pressurizing bottle. 27 and needle 28 are slidably inserted. A fuel chamber 29 is formed above the control iron 26, and this fuel chamber 29 is connected to the pressure accumulation chamber 12 (FIG. 2) via the fuel inlet 24 and the fuel supply pipe 10. Therefore, the fuel pressure in the pressure accumulation chamber 29 is applied to the fuel chamber 29, and the fuel pressure in the fuel chamber 29 acts on the upper surface of the control iron 26. The needle 28 has a conical pressure receiving surface 3
0, and a needle pressurizing chamber 30 is formed around this pressure receiving surface 30.
is formed. The needle pressurizing chamber 31 is connected to the fuel chamber 29 via a fuel passage 32 on the one hand, and to the nozzle hole 25 via an annular fuel passage 33 formed around the needle 28 on the other hand. A compression spring 34 that urges the pressure bottle 27 downward is inserted into the fuel injection valve body 20, and the needle 28 is pressed downward by the compression spring 34. The control iron 26 has a conical pressure receiving surface 35 in its intermediate portion, and a control iron pressurizing chamber 36 is formed around this pressure receiving surface 35. The pressurizing chamber 36 is communicated with a cylinder 37 formed within the fuel injection valve body 20, and a hydraulic piston 38 is slidably inserted into the cylinder 37.

An O-ring 39 is attached to this hydraulic piston 38.

On the other hand, a drive device 40 for driving the hydraulic piston 38 is attached to the fuel injection valve body 20. This drive device 40 includes a casing 41 fixed to the fuel injection valve main body 20.
and a piezoelectric element 42 inserted between the piston 38 and the casing 40. This piezoelectric element 42
The piezoelectric element 42 has a laminated structure in which a large number of thin plate-like piezoelectric elements are laminated, and when a voltage is applied to the piezoelectric element 42, the piezoelectric element 42 generates strain in the longitudinal direction due to an electrostrictive effect. That is, it extends in the longitudinal direction. This amount of elongation is, for example, 50μ
Although it is a small amount of about m, the response is extremely good, and the response time from application of voltage to expansion is about 80 μsec. When the voltage application is stopped, the piezoelectric element 42
shrinks immediately. As shown in FIG. 3, a disc spring 43 is inserted between the hydraulic piston 38 and the fuel injection valve body 20, and the spring force of the disc spring 43 presses the hydraulic piston 38 toward the piezoelectric element 42.

As shown in FIG. 4, there is a fuel passage 4 inside the hydraulic piston 38.
4 is formed, and a check valve 45 is inserted into this fuel passage 44. Fuel is circulated between the casing 41 and the piezoelectric element 42 by a device (not shown) in order to cool the piezoelectric element 42, and when the fuel in the control loft pressurizing chamber 36 leaks, the fuel in the casing 41 flows into the fuel passage 44. and is supplied into the control rond pressurizing chamber 36 via the check valve 45.

When the fuel in the control iron pressurizing chamber 36 is not pressurized, the needle 28 receives a downward force acting on the upper surface of the control iron 26, a downward force from the compression spring 34, and a pressure receiving surface 30 of the needle 28. An upward force acting on is added.

At this time, the diameter of the control rod 26, the spring force of the compression spring 34, and the area of the pressure receiving surface 30 of the needle 28 are set so that the sum of the downward forces is slightly larger than the upward forces. Therefore, a downward force normally acts on the needle 28, and thus the needle 28 normally closes the nozzle hole 25.Next, when a voltage is applied to the piezoelectric element 42, the piezoelectric element 42 expands. Hydraulic piston 3
8 moves to the left, and as a result, the pressure within the control rond pressurizing chamber 36 increases. At this time, the pressure receiving surface 35 of the control loft 26
Since an upward force acts on the control rod 26, the needle 28 rises, so that fuel is injected from the nozzle hole 25. As mentioned above, the response at this time is about 80 μsec, which is extremely fast. On the other hand, when the voltage application to the piezoelectric element 42 is stopped, the piezoelectric element 42 contracts, and as a result, the control rond pressurizing chamber 36
The control rod 26 and needle 28 are lowered to stop fuel injection. The response at this time is also extremely fast, about 80 μsec.

Note that, as described above, the diameter of the control iron 26 is adjusted so that the sum of the downward forces acting on the needle 28 is slightly larger than the upward force when the fuel in the control iron pressure chamber 3G is not pressurized. The spring force of the compression spring 34 and the pressure receiving surface 28 of the needle 28 can be increased.

That is, the fuel pressure in the control rond pressurizing chamber 36 that needs to be increased in order to raise the needle 28 only needs to be small, and thus the amount of electric power that needs to be applied to the piezoelectric element 42 is also small.

FIGS. 5 and 6 show an example of a fuel supply pump 14 whose discharge pressure can be controlled. Referring to FIG. 5, the fuel supply pump 14 is swingably attached to the pump casing 50 via a fixed shaft 51 fixedly supported by the pump casing 50, a rotor 52 rotating around the fixed shaft 51, and a pivot pin 53. a stator 54 and a ring 56 rotatably supported within the stator 54 via a bearing 55.
and has. The rotor 52 includes a large number of radial pistons 57 arranged radially, and each radial piston 5
A shoe 58 that rotates together with the radial piston 57 is inserted between the ring 56 and the radial piston 57 . When the rotor 52 rotates, the radial piston 57 also rotates, and at this time, the shoe 58 slides on the inner peripheral surface of the ring 56, and the ring 56 also rotates due to the frictional force with the shoe 58.

A suction port 59 and a discharge port 60 are formed on the fixed shaft 51.
Suction port 59 is connected to fuel pump 15 (FIG. 1), and discharge port 60 is connected to fuel pump 15 (FIG. 1).
are connected to the pressure accumulator chamber 12 (FIG. 1), respectively. The cylinder chamber 61 of each radial piston 57 communicates with the suction port 59 and the discharge port 60 alternately.

When the cylinder chamber 61 communicates with the suction port 59, the radial piston 57 moves radially outward, so fuel is sucked into the cylinder chamber 61, and the cylinder chamber 61 communicates with the discharge port 59.
0, compressed fuel is discharged from the cylinder chamber 61 to the discharge port 60. The pressure of the fuel discharged to the discharge port 60 depends on the stroke of the radial piston 57, and the stroke of the radial piston 57 is determined by the position of the stator 54. Therefore, by swinging the stator 54 around the pivot pin 53, the discharge pressure of the fuel supply pump 14 can be controlled.

Referring to FIGS. 5 and 6, the pump casing 50
A control lever 62 that is slidable in the axial direction of the fixed shaft 51 is arranged at the bottom of the fixed shaft 51 . The control lever 62 has a long groove 63 inclined with respect to the axis of the control lever 62, and an arm 64 formed at the lower part of the stator 54 is slidably inserted into the long groove 63. Therefore, when the control lever 62 is moved in its axial direction, the stator 54 swings, thereby controlling the discharge pressure of the fuel supply pump 14.

The control lever 62 is connected to a drive device 66 via a speed reduction mechanism 65. In this embodiment, the drive device 66 is formed of a step motor, but it is not necessary to use a step motor; for example, a linear solenoid or other means can be used as the drive device 66. Drive device 66
As a result, the control lever 62 is moved in its axial direction, so that the discharge pressure of the fuel supply pump 14 is controlled by the drive device 66.

Referring again to FIG. 1, an electronic control unit 70 is provided for controlling the fuel injection valve 8 and the drive device 66. This electronic control unit) 70 consists of a digital computer, and is connected to a ROM (read-on memory) by a bidirectional bus 71. 2, a RAM (random access memory) 73, a CPU (microprocessor) 74, an input port door 5, and an output port door 6.

As shown in FIG. 1, a fuel pressure sensor 80 for detecting the fuel pressure in the pressure accumulation chamber 12 is attached to the end of the fuel pressure accumulation pipe 11. The fuel pressure sensor 80 generates an output voltage proportional to the fuel pressure in the accumulator chamber 12, and this fuel pressure sensor 80
It is connected to the input port door 5 via a converter 81 . On the other hand, a boost pressure sensor 82 is installed inside the intake manifold 9 to detect the boost pressure inside the intake manifold 9. The boost pressure sensor 82 generates an output voltage proportional to the pressure within the intake manifold 9, and is connected to the input port door 5 via an AD converter 83.

Further, a water temperature sensor 84 is attached to the engine body 1 to detect the engine cooling water temperature. The water temperature sensor 84 generates an output voltage proportional to the engine cooling water temperature.
It is connected to the input port door 5 via a D converter 85. Further, a load sensor 87 that generates an output voltage proportional to the amount of depression of the accelerator pedal 86 is attached to the accelerator pedal 86 . This load sensor 87 is connected to the input port door 5 via an AD converter 88. Further, a pair of disks 89 and 90 are attached to the engine crankshaft, and a pair of crank angle sensors 91 and 92 are arranged opposite the toothed outer peripheral surfaces of these disks 89 and 90. On the other hand, the crank angle sensor 91 generates an output pulse indicating, for example, that the No. 1 cylinder is at the intake top dead center, and therefore it is determined from the output pulse of the crank angle sensor 91 which cylinder's fuel injection valve 8 is to be operated. can do. The other crank angle sensor 92 generates an output pulse every time the crankshaft rotates by a certain angle, so the engine speed can be calculated from the output pulse of the crank angle sensor 92. These crank angle sensors 91 and 92 are connected to the input port door 5. On the other hand, the output port door 6 is connected via a drive circuit 93 to a drive device 6 consisting of a step motor.
6 and is connected to the piezoelectric element 42 of the corresponding fuel injection valve 8 via the drive circuit 94.

Next, the operation of the fuel injection control device according to the present invention will be explained with reference to FIGS. 7 to 11.

FIG. 7 shows the main routine, which is executed by interrupts at every fixed crank angle. Referring to FIG. 7, first, in step 100, the output signal of the crank angle sensor 92 represents the engine speed N, the output signal of the load sensor 87 represents the amount of depression of the accelerator pedal, and the boost pressure sensor represents the boost pressure B. 82, the output signal of the water temperature sensor 84 representing the engine cooling water temperature T, and the output signal of the fuel pressure sensor 80 representing the fuel pressure P in the pressure accumulator 12 are sequentially input into the CPU 74, and the crank angle sensor 92 Engine speed N from the output signal of
is calculated. These engine speed N, accelerator pedal depression amount, supercharging pressure B, water temperature T and fuel pressure P are RA
M73. Next, in step 200, the injection amount τ is calculated, in step 300, the injection timing is calculated, and in step 400, the fuel pressure P is controlled. The calculation of the injection amount τ in step 200 is shown in FIG. 8, the calculation of the injection timing in step 300 is shown in FIG. 9, and the control of the fuel pressure P in step 400 is shown in FIG.

FIG. 8 shows a flowchart for calculating the fuel injection amount τ. Referring to Figure 8, first step 20
], the basic fuel injection amount τ is determined from the amount of depression of the accelerator pedal, that is, the load. is calculated. FIG. 11(a) shows the basic fuel injection amount τ. This relationship is stored in the ROM 72 in advance. Next, in step 202, a supercharging correction coefficient is calculated from the supercharging pressure P. Figure 11 (as shown in bl, the supercharging correction coefficient is 1
becomes thicker as the boost pressure P increases (Fig. 11).
Is the relationship shown in b) ROM in advance? It is stored in 2. Next, in step 203, the injection amount is set to τ=.

is calculated. Then, in step 204, the maximum injection amount MAX is calculated from the water temperature T. As shown in FIG. 11(C) (in order to prevent the generation of white smoke, the maximum injection amount MAX decreases as the water temperature T increases. Next, step 20
In step 5, it is determined whether or not the injection amount τ is larger than the maximum injection amount MAX. If τ>MAX, the process proceeds to step 206 and is set to τ-MAX. Therefore, the maximum injection amount MAX is limited by the water temperature T.

FIG. 9 shows a flowchart for calculating the fuel injection period. Referring to FIG.
1, the injection start timing τ is determined from the engine speed N and the load.
is calculated. As shown in FIG. 11(d), the relationship between 11, ..., τ, 7 at the injection start time, the engine speed N, and the load is stored in advance in the ROM 72 in the form of a map. The injection start timing τ1 is calculated from 0. Then, in step 302, the water temperature correction coefficient Kt is calculated from the water temperature T. As shown in FIG. 11(f), the water temperature correction coefficient becomes smaller as the water temperature T increases, and the relationship shown in FIG. A supercharging correction coefficient of 3 is calculated from the pressure P. The boost pressure correction coefficient increases as the boost pressure P increases, as shown in FIG. 11(e), and becomes larger as shown in FIG.
Is the relationship shown in el written in ROM in advance? It is stored in 2.

Next, in step 304, the correction coefficients Kt and Ks are added to the injection start time τ obtained in step 301 to obtain the actual injection start time τ1. The actual injection start timing τ increases as Kt and Ks increase. In other words, it is accelerated. Next, in step 305, the injection completion time τ1 is calculated from the injection amount τ calculated in the routine shown in FIG. 8 and the actual injection start time τ. The injection start time τ1 and injection completion time τ thus obtained are outputted to the output port door 6 in step 306, and injection control of each fuel injection valve 8 is performed according to these τ, , τ1.

FIG. 10 shows a flowchart for controlling the fuel pressure P. Referring to FIG. 10, first, in step 401, a reference fuel pressure P is calculated from the engine speed N and the load. FIG. 11 (As shown in the figure, the relationship between the reference fuel pressure pH'...Po, the engine speed N, and the load is stored in advance in the ROM 72 in the form of a map, and from this map the reference fuel pressure is calculated as 0. Next, in step 402, a water temperature correction coefficient of 4 is calculated from the water temperature T.The water temperature correction coefficient of 4 increases as the water temperature T increases, as shown in FIG. Figure (1)
Is the relationship shown in ROM in advance? It is stored in 2. Next, in step 403, the supercharging pressure correction coefficient K is calculated from the supercharging pressure P.
.

is calculated. The boost pressure correction coefficient increases as the boost pressure P increases as shown in FIG. 11 (hl), and the relationship shown in FIG. In step 404, the target reference fuel pressure PO1, that is, the target fuel pressure P0, is obtained by multiplying the reference fuel pressure P0 obtained in step 401 by a correction coefficient of 41Ks.The target fuel pressure P0 increases as the water temperature T increases. (The higher the boost pressure P is, the larger it becomes 0.) Next, in step 405, it is determined whether the absolute value of the difference between the target fuel pressure P0 and the current fuel pressure P is smaller than ΔP. ip, - If pl≧ΔP, step 4
Proceeding to step 06, it is determined whether p>p.

When P>PO, the process advances to step 407 and the drive device 66
That is, a fixed number of steps A is subtracted from the step position ST of the step motor 66. As a result fuel supply pump 1
Since the control lever 62 (FIGS. 5 and 6) of No. 4 is moved in the direction of decreasing the discharge pressure of the fuel supply pump 14, the fuel pressure within the pressure accumulator chamber 12 immediately decreases. On the other hand, P
When ≦P, the process proceeds to step 408, where a predetermined number of steps A is added to the step position ST of the step motor 66. As a result, the control lever 62 of the fuel supply pump 14 is moved in the direction of increasing the discharge pressure of the fuel supply pump 14, so that the fuel pressure within the pressure accumulation chamber 12 immediately increases. On the other hand, in step 405, IP・−pl<ΔP
When it is determined that this is the case, the processing routine is completed, and at this time, the step motor 66 is held in a stationary state. In this way, the fuel pressure P in the pressure accumulation chamber 12 is maintained at the target fuel pressure P0.

〔Effect of the invention〕

By controlling the fuel pressure in the pressure accumulation chamber, the injection rate of fuel injected from the fuel injection valve can be controlled to the optimum injection rate depending on the operating state of the engine.

As a result, optimum combustion can be ensured at all times regardless of the engine operating state, thereby suppressing noise generation and improving output and fuel consumption. Furthermore, since a small drive device can be used without requiring a large force to control the discharge pressure of the fuel supply pump, there is an advantage that only a small amount of electric power is required for controlling the discharge pressure.

[Brief explanation of drawings]

Figure 1 is a plan view schematically showing a diesel engine;
3 is a side sectional view of the diesel engine, FIG. 3 is a side sectional view of the fuel injection valve, FIG. 4 is an enlarged plan sectional view of the hydraulic piston in FIG. 3, and FIG. 5 is a side sectional view of the fuel supply pump. 6
The figure is a plan view of the control lever and its drive device in FIG.
Fig. 7 is a flowchart showing the main routine, Fig. 8 is a flowchart for calculating the injection amount, and Fig. 9 is a flowchart showing the main routine.
The figure is a flowchart for performing the calculation of the injection period,
FIG. 1θ is a flowchart for executing fuel pressure control, and FIG. 11 is a diagram showing correction coefficients, etc. 8... Fuel injection valve, io, 13... Fuel supply pipe, 12... Pressure accumulation chamber, 14... Fuel supply pump, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8 Figure 9 Figure 10 (a) (b) (d)
(e) (g)
(h) Figure 11 (C) ■ (f) ■ (j) Procedural amendment (voluntary) August 72, 1985 Director General of the Patent Office Michibe Uga 1, Indication of case Patent application No. 138990 of 8760 No. 2, Name of the invention Fuel injection control device for an internal combustion engine 3, Relationship with the person making the amendment Name of patent applicant (320) ) Yota Jidosha Co., Ltd. 4 Address of agent: 8 Toranomon-chome, Minato-ku, Tokyo 105 No. 10 No. 5,
Column 6 of “Detailed Description of the Invention” of the specification to be amended, contents of m (a) “Pressure” on page 10, line 20 of the specification is amended to “quantity j.” (o) Specification "Discharge pressure" on page 11, line 5 of the specification is corrected to "discharge amount j." Controlled. Corrected to J.

Claims (1)

[Claims] A fuel injection valve is connected to a fuel supply pump whose discharge pressure can be controlled via a fuel supply passage, and a pressure accumulation chamber of a constant volume is provided in the fuel supply passage, a fuel pressure sensor is arranged in the fuel supply passage, and the fuel pressure sensor is disposed in the fuel supply passage. Fuel injection control for an internal combustion engine in which the discharge pressure of a fuel supply pump is controlled based on the output signal of a fuel pressure sensor so that the pressure in the fuel supply passage becomes a predetermined pressure depending on the operating state of the engine. Device.