JPS63117148A - Fuel injection controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To control fuel pressure or fuel injection timing properly, by providing a means for setting a feedback control quantity at specific rotation based on a difference between a target fuel pressure and a detected fuel pressure. CONSTITUTION:A variable capacity fuel pump 36 and a fuel accumulator 38 are arranged between a fuel tank 34 and a fuel injection valve 32. The fuel injection valve 32, variable capacity fuel pump 36 and a solenoid valve 48 are controlled by a controller 50. The controller 50 has a feedback control quantity setting means for setting the feedback control quantity at specific rotation based on a difference between a target fuel pressure and a detected fuel pressure and a means for setting a correction feedback control quantity. Consequently, fuel pressure can be maintained continuously at a target level with high response resulting in a proper control of fuel injection timing or injection time.

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 fuel injection device for a diesel engine has conventionally included a fuel injection pump and a fuel injection valve, and the fuel injection pump pressurizes fuel at a predetermined timing and supplies it from a specific delivery port, and the fuel injection device connected to the delivery port is connected to the fuel injection device. The valve automatically opens due to the pressure of the fuel, and fuel is injected into the engine cylinder at high pressure. As described above, in the conventional fuel injection device, the fuel injection device functions to both pressurize the fuel and control the fuel injection timing. Since the fuel injection amount and fuel injection timing were controlled by the mechanical operation of the fuel injection pump, precise control such as finely changing the fuel injection amount and fuel injection timing depending on the engine operating condition was not possible. I couldn't say it was a satisfactory device.

To improve this, a fuel injection device called a common rail system has been proposed. Such a fuel injection device is described in, for example, Japanese Patent Laid-Open No. 57-68532. In this fuel injection system, the fuel pump has the sole function of supplying fuel at high pressure, and the high-pressure fuel supplied from this fuel pump is held in a pressure accumulator, and distributed from this pressure accumulator to each fuel injection valve. This is how it was done. A rotary control valve is disposed between the pressure accumulator and each fuel injection valve, and this controls the fuel injection timing.

In addition, the fuel injection pump is a variable displacement type equipped with a control rack, and the discharge amount is adjusted so that the fuel pressure in the pressure accumulator reaches a predetermined target fuel pressure depending on the engine operating state. It has become. A pressure sensor is attached to the pressure accumulator in order to feedback control the fuel pressure in the pressure accumulator to a target fuel pressure. With such a device, fuel injection pressure, fuel injection timing, etc. can be optimally controlled, and fuel efficiency and noise can be improved.

[Problem that the invention seeks to solve]

As described in the above publication, if fuel is supplied using a variable capacity fuel pump with capacity control means, the pressure of the fuel in the pressure accumulator can be freely controlled, and when the engine is under high load, the fuel pressure can be controlled in a short time. A large amount of fuel can be injected at high pressure, and small amounts of fuel can be injected little by little over a long period of time when the load is low. Controlling the fuel injection pressure by controlling the discharge amount of the variable displacement fuel pump in this way
This is quite advantageous because not only can a desired fuel injection pattern be obtained, but also the load on the fuel pump itself can be reduced without any loss when the engine load is low. However, when feedback controlling the fuel pressure in the pressure accumulator, the feedback control amount for each cycle is generally determined by a fixed correction coefficient, but if a fixed correction coefficient is used, the actual fuel pressure When the differential pressure between the fuel pressure and the target fuel pressure is large, there is a delay in reaching the target fuel pressure, and when the differential pressure is small, overshoot is likely to occur. A small value is generally adopted as the feedback correction coefficient, and multiple cycles of control are required to reach the target value.

In addition, the fuel pressure is controlled over a fairly wide range, and may vary rapidly, for example from 200 kg/am" to 700 kg/c+e2. In such cases, the pressure difference between the target pressure and the actual pressure may be large. Therefore, the feedback cannot be followed as described above.The present invention determines the feedback control amount as a function of the differential pressure between the actual fuel pressure and the target fuel pressure, thereby making it possible to improve the responsiveness of the control. By the way, in order to control the discharge amount of a pump, the pump's capacity control means is generally adjusted, but even if the pump's capacity control means is controlled in the same way, the actual discharge may vary depending on the rotation speed. There was a problem in that the amount changed, and therefore the responsiveness changed depending on the number of rotations.

[Means for solving problems]

In order to solve the above problems, a fuel injection control device for an internal combustion engine according to the present invention includes a variable capacity fuel pump and a system for holding fuel supplied from the variable capacity fuel pump between a fuel tank and a fuel injection valve. a fuel pressure accumulator having a constant volume, further comprising means for determining a target fuel pressure in accordance with engine operating conditions, a pressure sensor for detecting the fuel pressure in the pressure accumulator, and a means for determining a target fuel pressure in accordance with the detected fuel pressure. feedback control means for driving and feedback controlling the capacity control means of the variable displacement fuel pump in response to the pressure;
The feedback control means includes a feedback control amount setting means for determining a feedback control amount for a specific rotational speed based on a differential pressure between the target fuel pressure and the detected fuel pressure, and a feedback control amount setting means for correcting the feedback control amount by the rotational speed at that time The present invention is characterized in that it includes feedback control amount correction means for determining a correction feedback control amount.

〔Example〕

FIG. 1 shows a diesel engine main body 12 equipped with a supercharger 10, and the engine main body 12 has a piston 18 in a cylinder formed by a cylinder block 14 and a cylinder head 16, as shown in FIG. It is inserted. The combustion chamber 20 is defined by a cavity formed in the top surface of the piston 18. An intake manifold 22 is connected to the supercharger 10, and each branch pipe thereof communicates with an intake boat 24 of the cylinder head 16. An intake valve 26 is arranged on the intake boat 24, while an exhaust boat 28
An exhaust valve 30 is arranged. In a diesel engine, the fuel injection valve 32 is mounted on the cylinder head 16 so as to face directly into the combustion chamber 20.

As shown in FIG. 1, between the fuel tank 34 and the fuel injection valve 32, there is a variable displacement fuel pump 36 and a fixed volume for holding the fuel supplied from the variable displacement fuel pump 36. A fuel pressure accumulator 38 is arranged. In the embodiment, a feed pump 40 is arranged in front of the variable capacity fuel pump 36. The fuel pressure accumulator 38 is common to each fuel injection valve 32 and is connected to each other by a vibrator 42. A return vibe 44 extends from each fuel injection valve 32 to the fuel tank 34. moreover,
A fuel overflow pipe 146 is provided to connect the fuel pressure accumulator 38 and the fuel tank 34, and a solenoid valve 48 whose duty can be controlled is disposed in the middle of this fuel overflow pipe 46.

The fuel injection valve 32, variable displacement fuel pump 36, and solenoid valve 48 are controlled by a control unit (ECU) 50. The control device 50 is configured as a microcomputer, and has a third
As shown in the figure, a central processing unit (CPU) 52 having calculation and control functions, a one-way only memory (ROM) 54 for storing programs, and a random access memory (RAM) 56 for storing data, etc. Prepare,
These are interconnected by a bus 58, and
Detected values from each sensor are input via the input/output interface 60, and control signals are output to the fuel injection valve 32, variable displacement fuel pump 36, and electromagnetic valve 48 to detect the operating state of the engine. The sensor includes a load sensor 62 that detects the opening degree of the accelerator pedal to detect the engine load, a rotation speed sensor 64 that detects the rotation speed of the crankshaft, and a pressure sensor that detects the pressure of the fuel in the fuel pressure accumulator 38. Sensor 66 is of particular importance. Other sensors, such as water temperature sensor 68 and boost pressure sensor 70, may also be provided.

FIG. 4 is a detailed view of the fuel injection valve 32. fuel injection valve 3
2 has a valve body 72 and a nozzle body 74, which are integrated by a nozzle holder 76.
A needle valve 78 is inserted into the hole, and the nozzle 80 at the tip can be opened and closed.

A fuel inlet 82 is formed at the upper end of the valve body 72 and communicates with a bore 84 passing through the center of the valve body 72 and a fuel passage 86 extending parallel to the bore 84 . The fuel passage 86 communicates with an annular fuel reservoir 88a of the nozzle body 74, which applies a force that acts on the tapered portion 78a of the needle valve 78 to lift the needle valve 78, and also communicates with the nozzle 80 at the tip. Additionally, a pressure bin 88 is provided at the top of the needle valve 78.
are in contact with each other, and the pressure bin 88 is urged by the spring 90 in the direction in which the needle valve 78 closes.

A control rod 92 is inserted into a bore 84 passing through the center of the valve body 72, and the control rod 92 receives the pressure of fuel supplied from above, and its lower end is in contact with a pressure bin 88. Therefore, the needle valve 78 receives a downward force due to the pressure of the fuel supplied from above and the pressure of the spring 9o, and the tapered portion 78 receives a downward force from below.
8a receives an upward force due to the pressure of the fuel,
Since the downward force is greater, the needle valve 78 is normally closed. The needle valve 78 opens when the downward fuel pressure transmitted through the control rod 92 is removed. For this purpose, the valve body 72 is provided with a passage 94 orthogonal to the bore 84, such that the pressure generated in this passage 94 acts on the tapered portion 92a of the control rod 92. Furthermore, a cylinder bore 96 is formed as an extension of this passage 94, in which a control piston 98 is arranged. An actuator case 100 is attached to the rear of the control piston 98, and a piezo actuator 102 made of a laminated body is inserted into the actuator case 100. The piezo actuator 102 is made of an electrostrictive element and exhibits strain proportional to the supplied voltage. Thus, applying voltage to piezo actuator 102 causes it to extend, thus pushing control piston 98 and compressing the volume of passageway 94, thus creating a pressure that lifts control rod 92. When the supply voltage to the piezo actuator 102 disappears, it degenerates,
It is returned to its original position by a return spring 104. Therefore, by supplying voltage to the piezo actuator 102, the needle valve 78 opens to perform fuel injection, and by stopping the voltage supply to the piezo actuator 102, the fuel injection ends. In addition, fuel injection valve 3
The fuel population 82 of No. 2 is supplied from the fuel pump 36,
High-pressure fuel held in the fuel pressure accumulator 38 is constantly supplied. In addition, the passage 94 has leakage of fuel from the bore 84 and the annular fuel reservoir 86a, so the passage 94
is always filled with fuel. In addition, the control piston 9
8, as shown in FIG. 5, is provided with a small hole 108 passing through the front and rear thereof, so that combustion can flow into the Yuator case 100 and cool the piezo actuator 102. . A check valve 108 is located at the forward end of the small bore 108 to prevent leakage during the forward pressurization stroke of the control piston 98.

FIG. 6 is a diagram showing a detailed example of the variable capacity fuel pump 36 constructed from a radial plunger pump. This variable capacity fuel pump 36 includes a pump gauging 110;
a central shaft 112 fixed to the pump casing 110;
a rotor 114 rotatable around a fixed central axis 112;
A plurality of plungers 116 radially and slidably supported by the rotor 114, a shoe 116a attached to the tip of the plunger 116, a ring 118 in which the shoe 116a is housed, and a bearing 119 that accommodates the ring 118.
The stator 120 is rotatably supported by the stator 120. The stator 120 is pivotally supported by a single pivot pin 122 and has arms 124 diametrically opposed to each other. This arm 124 is inserted into the ramp 71112B of the control lever 126, and axially driving the control lever 126 causes the stator 120 to pivot about the pivot bin 122. This is the axis of the rotor 114 and the stator 120.
This means that the degree of eccentricity with respect to the axis of the pump changes, which causes the displacement of the pump to change. That is, the pump action is performed by the plunger 116 compressing the pump operation space 130 formed at the inner end of the plunger 116, and the axis of the rotor 114 and the stator 1 described above are aligned.
The change in the degree of eccentricity with respect to the axis of 20 is the same as the pump operating space 1.
This is because the effective volume of 30 will be changed. In this way, the control lever 126 allows capacity control. Note that this working space 130 has a suction boat 1 extending in the axial direction so as to face the fixed central shaft 112 in the diametrical direction.
32 and the discharge boat 134 alternately.

FIG. 7 is a diagram showing an example of a variable capacity fuel pump 36 constructed from an axial plunger pump. This includes a piston 138 disposed circumferentially within a rotatable cylinder block 136, a fixed valve plate 140 disposed to close the end of the cylinder block 136, and an inclined relative to the axis of the cylinder block 136. The valve plate 140 has suction and discharge grooves (
(not shown) is provided. The tilt angle of the swash plate 142 can be changed by a control lever 144;
This allows capacity control. And control lever 1
26, or 144, can be electrically controlled by a suitable actuator, such as a stepper motor.

As described above, in the present invention, the fuel injection valve 32, the fuel pump 36, and the solenoid valve 48 can be electrically controlled, and the control is performed by the computer control device 50 shown in FIG.
It is executed by Figure 8 shows fuel injection valve 3
2 is a flowchart for control of step 15.
0, the fuel injection amount (T) is calculated based on the engine load and rotational speed. The fuel injection amount (T) can be stored in the RON 54 as a map as shown in FIG. Next, in step 151, a fuel injection start timing is calculated.In step 152, a fuel injection period according to the calculated fuel injection amount and the pressure in the fuel pressure accumulator 38 is calculated. This fuel injection period is also stored as a function of fuel injection amount and pressure. This fuel injection period becomes shorter as the fuel pressure increases under the same engine operating conditions. Thus, in step 153, the injection end time is calculated from the fuel injection start time and the injection period.

As described above, when the fuel injection start time calculated in step 151 comes, the piezo actuator 102 of the fuel injection valve 32 is energized, and when the injection end time calculated in step 153 comes, the energization is stopped. still,
When calculating the fuel injection timing, corrections can be made based on water temperature, etc.

FIG. 11 shows a fuel pump 36 for controlling fuel pressure.
and a flowchart of control of the solenoid valve 48. The engine rotational speed N at which the engine operating state is determined in step 160
e, engine load Q, and fuel pressure P in the fuel pressure accumulator 38
The pressure P of the fuel in the fuel pressure accumulator 38 is detected by the pressure sensor 66, and is hereinafter referred to as the actual pressure P.Next, in steps 161 and 162, the fuel pump 36 is controlled. The basic control value R1 and the target fuel pressure P of the capacity control means such as the lever 126 are calculated as the number between the engine speed Ne and the engine load Q, respectively. These can be stored in the ROM 54 as a map of the target fuel pressure P, for example, as shown in FIG. Subsequently, in step 163, the differential pressure ΔP between the target pressure P and the actual pressure PR is calculated. Furthermore, in step 164, it is determined whether the differential pressure ΔP is 0 or more. When the differential pressure ΔP is positive, the target fuel pressure P is 'actual pressure P1. Since it is larger than I, it means that the fuel pressure in the fuel pressure accumulator 38 is required to be increased, and conversely, when it is negative, it means that the fuel pressure in the fuel pressure accumulator 38 is required to be lowered. .

In this way, in the case of YES in step 164, the process proceeds from steps 165 to 167 to perform pressure boost control, and in the case of NO, the process proceeds to steps 169 to 171 to perform pressure reduction control.
m ) feedback control amount α1゜oo is set as the target pressure P
It is calculated as a function of the differential pressure ΔP between the actual pressure PR and the actual pressure PR. This feedback control amount α1°. . is experimentally determined and stored as a function as shown in FIG. 12, and the differential pressure ΔP
The maximum value is 1. Step 16
6, the feedback control amount α+oo for a specific rotation speed
. A corrected feedback control amount α1 is determined by correcting the rotation speed Ne using the rotational speed Ne at that time. In this case, α1=α1°. . X
Calculate as 1000/N e. The discharge amount of the pump is determined by the product of the rotation speed and the capacity, and as the rotation speed increases, the pump discharge amount increases even if the differential pressure ΔP remains the same.

Therefore, the feedback control variable α, calculated as a function of the differential pressure ΔP at a specific rotational speed. . . is corrected so as to obtain the optimum boost characteristic for the rotational speed at that time. As a result, the amount of fuel discharged increases as the differential pressure ΔP increases regardless of the rotation speed, and conversely decreases as the differential pressure ΔP decreases, and the differential pressure increases when the target pressure changes greatly due to changes in operating conditions. The actual pressure also increases quickly following ΔP, and when the change in operating conditions is small, the feedback control amount can be reduced to prevent overshoot and fluctuations from occurring.

In step 167, the capacity control means 126 of the pump 36
The basic control value R1 calculated in step 161 is the control amount R of
Calculated by multiplying by (1+α1). Then, in step 168, the duty control value D of the solenoid valve 48 is
Set TYPR to 0. That is, during pressure increase control, the solenoid valve 48 is closed.

Steps 169 to 171 implement step-down control, and in this case, the feedback correction amount is β (β in FIG. 12).

. . ) is used and a subtraction operation is performed in step 171, but corresponds to steps 165 to 167. Furthermore, in step 172, it is determined whether the correction feedback control amount β1 during the subtraction process is 1, that is, its maximum value. If the correction feedback control amount β1 during the subtraction process becomes 1, the pump 3
Since the capacity of valve 6 is 0 and pressure reduction control is still required, the solenoid valve 48 is opened. If no, the process proceeds to step 168 and the solenoid valve 48 is kept closed.

If the answer is yes in step 172, the solenoid valve 48 can be fully opened, but in this embodiment, step 1
Duty ratio DTY at a specific pressure (200 bar) at 73. . (see FIG. 14), and in step 174 this duty ratio DTY2° is determined. to (2
Corrected duty ratio DTY corrected by the actual fuel pressure P2 at that time by multiplying by 00/P,)
P R is determined, and the solenoid valve 48 is duty-controlled based on this value.

〔Effect of the invention〕

As explained above, according to the present invention, the feedback control amount is determined as a function of the differential pressure between the actual fuel pressure and the target fuel pressure, thereby constantly maintaining the fuel pressure at the target value with good responsiveness. This makes it possible to appropriately control fuel injection timing and injection time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a fuel injection control device for an internal combustion engine according to the present invention, FIG. 2 is a vertical sectional view of the internal combustion engine of FIG. 1, FIG. 3 is a block diagram of the control device, and FIG. 4 is a fuel injection valve 5 is an enlarged view of the control piston shown in FIG. 4, FIG. 6 is a view showing an example of a variable displacement fuel pump, FIG. 7 is a view showing another example of a variable displacement fuel pump, and FIG. Figure 8 is a flowchart for controlling the fuel injection valve, Figure 9 is a map for calculating the fuel injection amount, Figure 10 is a map for calculating the target fuel pressure, and Figure 11 is a diagram for calculating the fuel injection amount. Flowchart for pressure control, Fig. 12 is a diagram showing the feedback control amount when increasing the pressure with respect to the differential pressure, Fig. 13 is a diagram showing the feedback control amount when decreasing the pressure with respect to the differential pressure, and Fig. 14 is a diagram showing the feedback control amount when the pressure is reduced with respect to the differential pressure. It is a figure showing the duty ratio of a valve. 12... Engine body, 22... Intake manifold, 32... Fuel injection valve, 34... Fuel tank, 3
6...Fuel pump, 38...Fuel pressure accumulator, 46...
...Fuel overflow pipe, 48...Solenoid valve. 1st Figure 32...Fuel injection valve 36...Fuel pump 3813. Fuel accumulator marriage 2 ■ Figure 3 Figure 4 Q 45 Kojima 7 ■ Figure 8 Figure 10 ∆P Figure 12 Inrei Figure 13 - 614'fig Procedural amendment (method) % formula % 1. Indication of the incident Showa 1961 Patent Application No. 261973 2, Name of the invention Fuel injection control device for internal combustion engine 3, Relationship with the amended case Name of patent applicant (320) Toyota Motor Corporation 4, Address of agent: 105 Tokyo Port Shizuka Toranomon Building, 8-10, Toranomon-ku, Tel: 504-07215, Date of amendment order: January 2, 1985), J 6, "Brief explanation of drawings" column 7 of the specification subject to amendment , on page 20, line 15 of the statement of contents of the amendment, ``No. 14 is a solenoid valve...''
・" should be corrected to "Figure 14 shows the solenoid valve...j.

Claims (1)

[Claims] A variable capacity fuel pump and a fuel pressure accumulator having a constant volume for holding the fuel supplied from the variable capacity fuel pump are disposed between the fuel tank and the fuel injection valve, and further, a fuel pressure accumulator having a constant volume is arranged between the fuel tank and the fuel injection valve. means for determining fuel pressure; a pressure sensor for detecting fuel pressure in the pressure accumulator; and feedback control by driving the capacity control means of the variable capacity fuel pump so that the detected fuel pressure responds to a target fuel pressure. feedback control means for determining a feedback control amount for a specific rotational speed based on a differential pressure between the target fuel pressure and the detected fuel pressure; 1. A fuel injection control device for an internal combustion engine, comprising: feedback control amount correction means for determining a corrected feedback control amount corrected based on the rotational speed.