JPH0463933A - Fuel injection control device - Google Patents

Abstract

PURPOSE:To prevent the reduction of a fuel injection quantity with the lowering of fuel pressure and improve acceleration performance at the time of acceleration by making a quantity-increasing correction for the fuel injection quantity at the time of the acceleration condition of an internal combustion engine according to the lowering quantity of fuel pressure. CONSTITUTION:The acceleration condition of an internal combustion engine 1 causes quantity-increasing control for a fuel supply quantity and a fuel injection quantity according to the acceleration quantity in the condition. In this case, a value, referring to the lowering quantity of fuel pressure due to the difference between responsive speeds of the increases of the fuel supply quantity and the fuel injection quantity, is detected with a detection means 26. Then the fuel injection quantity with a fuel injection valve 4 is made a quantity-increasing correction with a correction means 16 according to the value referring to the lowering quantity of the fuel pressure. As a result, even if the fuel pressure is temporarily lowered attendant upon acceleration, the fuel injection quantity in the lowering condition of fuel pressure is made the quantity-increasing correction according to the lowering quantity of the fuel pressure, consequently an air-fuel ratio does not become lean at the time of acceleration to improve acceleration performance.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a fuel injection control device that controls the amount of fuel supplied to a fuel injection valve by an electric fuel pump and also controls the fuel injection timing and injection period of the fuel injection valve. In particular, it aims to improve the acceleration performance of an internal combustion engine.

[Prior art]

Conventionally, various sensors have been used to detect the operating state of an internal combustion engine, the amount of fuel required by the internal combustion engine is determined from the operating state, and the amount of fuel injected by the fuel injection valve is determined according to the required amount of fuel. It is being said. In particular, during acceleration, the air-fuel ratio temporarily becomes lean due to timing delays in injection timing control, response delays in the output value of the air flow meter, and the like. In order to prevent this, fuel is injected asynchronously in an amount corresponding to the amount of change in throttle opening over time (asynchronous injection). In addition, the voltage applied to the fuel pump is adjusted according to the load and rotational speed of the internal combustion engine to control the amount of fuel supplied from the fuel tank to the fuel injection valve, and the amount of fuel supplied by the fuel pump is increased during acceleration. The device is known (Japanese Unexamined Patent Publication No. 5
9-150972). In addition, the fuel injection time is controlled according to the operating state of the internal combustion engine, and the voltage dependence of the amount of fuel supplied by the fuel pump is controlled.
A device is known that takes into account the dependence of fuel pressure on the fuel supply amount and corrects the injection time according to the drive voltage of the fuel pump (Japanese Patent Application Laid-Open No. 142346/1983).

[Problem to be solved by the invention]

However, in controlling the amount of fuel supplied by the fuel pump, there is a problem in that the responsiveness to changes in the amount of fuel supplied is poor. In other words, there is a time delay from when the voltage applied to the motor that drives the fuel pump is changed until the fuel pump starts up to a predetermined rotation speed, and there is a delay in the rise of the fuel flow rate due to the viscosity of the fuel, so the fuel supply by the fuel pump is difficult. There is a time delay in the increase in volume. Therefore, even if the fuel supply amount is increased during acceleration, the actual fuel supply amount cannot be increased immediately, and the fuel supply amount becomes smaller than the fuel requirement of the internal combustion engine during acceleration. As a result, the fuel pressure decreases, resulting in a lean air-fuel ratio during acceleration, resulting in poor acceleration performance. Further, in the device disclosed in Japanese Patent Application Laid-open No. 61-142346, fuel pressure is predicted by the voltage applied to the motor that drives the fuel pump, and the fuel injection amount is corrected in accordance with the fuel pressure. However, due to an increase in the voltage applied to the fuel pump motor during acceleration, it is immediately determined that the fuel pressure has increased, and a correction is made to shorten the injection time by the increase in fuel pressure.
After all, the air-fuel ratio becomes lean during acceleration. Next, we will specifically discuss how the air-fuel ratio becomes lean during acceleration. As shown in FIG. 8(C), when the accelerator pedal is depressed to open the throttle valve, the opening speed VTA changes as shown in FIG. 8(5). As the measured amount of intake air per rotation of the enshiff increases, the basic injection time increases as shown in FIG. 8(a). At this time, the rise of the basic injection time is delayed due to the response delay of the detected value of the air flow meter, so as shown in Figure 8 (a), the injection time increases sharply from the rise of the throttle valve opening speed VTA. A correction is made, and part of the correction becomes the increase due to asynchronous injection. In this way, the required fuel amount during acceleration increases sharply, and by increasing the injection time, the actual fuel injection amount can rapidly increase during acceleration. On the other hand, the voltage applied to the fuel pump motor is basically increased as the amount of intake air per revolution of the engine increases, and is increased in steps as shown in Figure 8 (0). As shown in Figure 8, the amount of fuel supplied rises slowly after the timing when the applied voltage is increased due to motor responsiveness, fuel viscosity, etc. Therefore, at the beginning of acceleration, the amount of fuel supplied increases gradually. During the period when the amount of fuel cannot respond quickly to the fuel demand, the fuel surplus amount is
It becomes zero as shown in the figure. As a result, during that period, the fuel pressure decreases as shown in Figure 8(e), and even if the fuel injection time is corrected to increase, the actual fuel injection amount will be smaller than the theoretical value determined by the fuel injection time. . Therefore, at the beginning of acceleration, the air-fuel ratio A/F becomes lean, as shown in FIG. 8, and there is a delay in increasing the engine speed NB, as shown in FIG. 8 (1). The present invention has been made to solve the above problems, and its purpose is to prevent the air-fuel ratio from becoming lean during acceleration of an internal combustion engine and improve acceleration performance.

[Means to solve the problem]

The structure of the invention for solving the above problem is to control the amount of fuel supplied by a fuel pump and the amount of fuel injected by a fuel injection valve according to the amount of fuel required by the internal combustion engine, and when the internal combustion engine is in an acceleration state. In some cases, a fuel injection control device that corrects the fuel injection amount according to the acceleration amount increases the fuel supply amount by the fuel pump and the fuel injection amount by the fuel injection valve when the internal combustion engine is in an accelerating state. a detection means for detecting a value related to a decrease in the pressure of the fuel supplied to the fuel injection valve by the fuel pump caused by a difference in response speed between the increase and the response speed; Therefore, a correction means for increasing the fuel injection amount when the internal combustion engine is in an accelerating state is provided.

[Effect]

When the internal combustion engine is accelerated, the amount of fuel supplied and the amount of fuel injection are controlled to increase in accordance with the amount of acceleration. At this time, the detection means detects a value related to the amount of decrease in fuel pressure caused by the difference in response speed between the increase in the fuel supply amount and the increase in the fuel injection amount. Then, the correction means increases the amount of fuel injected by the fuel injection valve in accordance with the value related to the amount of decrease in fuel pressure. As a result, even if there is a temporary drop in fuel pressure due to acceleration, the fuel injection amount when the fuel pressure is low is corrected to increase according to the amount of the drop, so the air-fuel ratio during acceleration becomes lean. This improves acceleration performance.

【Example】

The present invention will be described below based on a specific example. In FIG. 1, an intake passage 2 and an exhaust passage 3 are connected to an engine 1, and a fuel injection valve 4 is disposed in the intake passage 2. A fuel supply passage 5 is connected to the fuel injection valve 4, and a fuel pump 7 that supplies fuel from a fuel tank 6 to the fuel injection valve 4 is provided in the fuel supply passage 5. The fuel pump 7 is composed of an electric motor, and its rotation speed is controlled by adjusting the applied voltage, and the amount of fuel supplied can be controlled according to the rotation speed. Filters 8.9 are provided before and after the fuel pump 7 in the fuel supply passage 5, and these filters 8.9 prevent the fuel pump 7 and the fuel injection valve 4 from malfunctioning due to foreign matter. Further, a return passage 10 is branched from the fuel supply passage 5 on the upstream side of the fuel injection valve 4;
is connected to the fuel tank 6 via a pressure regulator 11. The intake negative pressure in the intake passage 2 near the fuel injection valve 4 is introduced into the pressure regulator 11, and the pressure regulator 11 is designed to maintain a constant difference between this intake negative pressure and the fuel pressure in the fuel supply passage 5. The amount of fuel returned through the return passage 10 is adjusted. The fuel injection valve 4 is provided with a temperature sensor 12 that detects the fuel temperature based on the temperature of the fuel injection valve 4. On the other hand, an air cleaner 13 is installed in the intake passage 2 of the engine 1.
An air flow meter 14 for detecting the amount of intake air indicating the load amount of the engine 1 is disposed downstream of the air flow meter 14 , and a throttle valve is installed in the intake passage 2 downstream of the air flow meter 14 and upstream of the fuel injection valve 4 . 15 are interposed. A throttle sensor 25 having an acceleration sensor 26 is operatively coupled to the throttle valve 15 . The acceleration sensor 26 is a sensor that detects the opening speed of the throttle valve 15. Further, a bypass passage 27 is provided outside the intake passage 2 to bypass the throttle valve 15 and allow intake air to flow. is mediated. The ISC valve 24 is a solenoid valve, and by duty-controlling the solenoid valve, the amount of bypass intake air when the throttle valve 15 is fully closed can be electrically controlled. Additionally, the fuel pump 7 controls the fuel supply amount, the fuel injection valve 4 controls the fuel injection amount and injection timing, and the SC valve 24 controls the fuel injection amount and injection timing.
A control device 16 is provided to perform control. The fuel pump 7 changes the rotation speed according to the average voltage output from the DC-DC converter 21, and the DCDC converter 21 changes the rotation speed according to the control signal commanded by the control device 16.
Controls the 8-power average voltage. A current detector 22 is provided to detect the current supplied from the DC-DC converter 21 to the fuel pump 7, and a detection signal from the current detector 22 is input to the control device 16. . In addition, an intake air amount signal indicating the load amount of the engine 1 from the air flow meter 14, a fuel temperature signal from the temperature sensor 12, and an engine rotation speed signal from the rotation sensor 17 are input to the control device 1G. A warning light 23 is connected to indicate a failure state. As shown in FIG. 4, the control device I6 basically controls the amount of fuel supplied by controlling the voltage applied to the fuel pump 7 according to the amount of fuel injection. The amount of fuel supplied is controlled to be a predetermined amount greater than the amount of fuel required by the engine at that time. That is, it is designed so that the amount of fuel supplied is always somewhat larger than the actual amount of fuel injected, and a constant amount of fuel is returned. Further, when the fuel temperature detected by the temperature sensor 12 reaches a high temperature higher than the set value, the control device 16 causes the fuel pump to rotate 70 times via the DC-DC converter 21 so as to increase the amount of fuel returned flowing through the return passage 10. improve numbers. Further, the control device 16 controls the injection timing and injection amount of the fuel injection valve 4 according to the injection timing and injection amount calculated from the engine rotation speed detected by the rotation sensor 17 and the intake air amount detected by the air flow meter 14. The injection period is controlled. The control device 16 that performs the above basic operations includes a CPU 160,
ROM 161 that stores the control program and the relationship between the applied voltage and the fuel injection amount that determines the fuel supply amount in a map format.
, a RAM 16 for storing input data and -time storage data.
2, input/output interfaces 163 and 164. Note that 18 is an intake valve, 19 is an exhaust valve, and 20 is a spark plug. Next, the operation of the present device will be explained with reference to a flow chart of the processing procedure of the CPU 160 of the control device 16. (1) Voltage control of fuel pump Voltage control of the fuel pump is performed according to the program shown in FIG. This program is repeatedly executed in synchronization with the 180 degree crank angle signal output from the rotation sensor 17. In step 100, the intake air amount Q output from the air flow meter 14 is read. In the next step 102, the start interval of this program, that is, the cycle of the 180 degree crank angle signal output by the rotation sensor 17 is measured, and the current engine rotation speed NB is calculated from the interval, and this value is stored in the RAM 162. be remembered. Next, in step 104, the intake air amount QN per rotation is calculated from the intake air amount port and the engine rotational speed NB. This intake air amount per revolution N corresponds to the pressure in the intake passage 2. Next, the process proceeds to step 106, where a fuel injection amount (fuel consumption) q per unit time is calculated from the fuel injection time T and engine rotational speed NB determined by a program to be described later. At this time, the fuel injection amount due to asynchronous injection is also taken into consideration for the fuel injection amount q. Next, the process proceeds to step 108, where the output value of the acceleration sensor 26 (opening speed of the throttle valve 15) VTA is input. Next, step 1101. : Set the throttle valve 15
It is determined whether the opening speed VTA of is equal to or greater than a predetermined value α. If the opening speed VT^ of the throttle valve 15 is not equal to or higher than the predetermined value α, in step 112, according to the characteristics shown in FIG. The voltage V, applied to the motor is determined. Note that when the pressure in the intake passage 2 is high, even if the relative pressure of the fuel pressure with respect to the pressure in the intake passage 2 is constant, the absolute value of the fuel pressure becomes high, so the load on the fuel pump 7 increases. Therefore, the applied voltage V with respect to the pressure in the intake passage 2 is also corrected. If it is determined in step 110 that the opening speed VTA of the throttle valve 15 is equal to or greater than the predetermined value α, then in step 114 the throttle valve 15 is adjusted according to the characteristics shown in FIG. Opening speed VTA
Then, the applied voltage Vp corrected by the intake air amount ON per one rotation of the enshiff is calculated. Next, in step 116, a duty ratio 0 for controlling the DC-DC converter 21 corresponding to the applied voltage VP is calculated. Next, in step 11g, a control signal corresponding to the duty ratio is output to the DC-DC converter 21. As a result, the average voltage applied to the fuel pump 7 is controlled, so that the optimal amount of fuel supplied by the fuel pump 7 for the current load state of the engine 1 is realized. (2) Asynchronous injection control Asynchronous injection control is executed according to the program shown in FIG. This program is repeatedly executed at a cycle that is sufficiently shorter than the synchronous fuel injection cycle. In step 200, it is determined whether the opening speed VTA of the throttle valve 15 is greater than or equal to a predetermined value α. If the opening speed VTA of the throttle valve 15 is not equal to or greater than the predetermined value α, the asynchronous injection according to this program is not executed. On the other hand, if the opening speed VTA of the throttle valve 15 is equal to or higher than the predetermined value α, in step 202, the applied voltage VPO before the opening speed VTA of the throttle valve 15 exceeds the predetermined value α, that is, before acceleration The fuel supply amount port is determined by taking into account the difference in intake air amount per revolution corresponding to the pressure in the intake passage 2. The reason why the applied voltage v2° before acceleration is used is that at the beginning of acceleration,
This is because the rise of the fuel supply amount Qp is delayed, so the applied voltage VPO before acceleration better represents the current fuel supply amount. Next, in step 204, the current fuel supply amount Q,
The surplus fuel amount is calculated as the difference between the current fuel injection amount q and the current fuel injection amount q. Next, in step 206, the asynchronous injection pulse width τ is calculated from the fuel surplus amount 03 and the opening speed VTA of the throttle valve 15 according to the characteristics shown in FIG. Then, in step 208, the injection valve 4 receives the asynchronous injection pulse width τ determined in step 206. The valve will be open for a period of , and then the program will end. Note that the calculation in step 202 is based on the throttle valve 15.
When the opening speed VTA exceeds the predetermined value α, the asynchronous injection is repeatedly executed at a predetermined minute timing. At this time, since the fuel supply amount Qp rises with an exponential delay with a predetermined time constant with respect to a change in the applied voltage, the function G may be a function including a time variable that approximates its characteristics. (3) Synchronous injection control Synchronous injection is performed once per engine revolution. The synchronous injection pulse width τ is determined as follows. The current engine speed NE is read from the RAM 162, the intake air amount V is read from the air flow meter 14, and each output signal from the throttle sensor 25 is read. Additionally, the cooling water temperature, intake air temperature, battery voltage, starter switch status, etc. are read from various sensors (not shown). Based on these input values, the injection pulse width τ for controlling the injection time T of the fuel injection valve 4 is calculated, as is well known. Of the injection pulse width τ, the basic pulse width is determined from the intake air amount V and the engine rotation speed ME, and the correction term or correction coefficient for the injection pulse width is stored in the ROM 161 in advance from other output values. Determined by referring to the data map. Further, a correction may be made by adding the pulse width τ obtained in step 206 to this synchronous injection pulse width τ3. (4) Operation explanation using characteristic diagrams As mentioned above, at the beginning of acceleration, the actual fuel supply amount cannot respond quickly to the fuel demand amount, so the difference between the intake negative pressure and the fuel pressure is as shown in Figure 7(e). As shown in FIG. 7(a), the injection time is further corrected to increase according to the amount of decrease in fuel pressure. As a result, the actual fuel injection amount becomes equal to the fuel requirement of the engine 1, and the air-fuel ratio A/F does not become lean, as shown in FIG. 7G. Therefore, the responsiveness of the engine speed increase by 10 during acceleration is improved as shown in FIG. 7(1). In the above embodiment, the detection means predicts the actual fuel supply amount from the applied voltage, taking into account the response delay of the fuel supply amount, and calculates the difference between the fuel injection amount and the fuel injection amount known from the injection time. The surplus fuel amount is predicted, and the fuel pressure is predicted based on the surplus fuel amount. However, a means for directly measuring the pressure of the fuel supplied from the fuel pump 7 to the fuel injection valve 4 may be used. Furthermore, although the opening speed VTA of the throttle valve 15 is used for acceleration detection, the state of the idle switch, the amount of change per unit time in the negative pressure of the intake road 2, and the amount of intake air per unit time per rotation of the engine shifter 10 are also used. The amount of change per unit time of the synchronous injection time may be used. Further, the above-described amount of change may be used to correct the increase in the injection time during acceleration.

【Effect of the invention】

The present invention provides a method for supplying fuel to an injector by a fuel pump, which is caused by a difference in response speed between an increase in the amount of fuel supplied by the fuel pump and an increase in the amount of fuel injected by the fuel injector when the internal combustion engine is in an accelerating state. detects the value related to the amount of pressure drop of the fuel that is
The fuel injection amount when the internal combustion engine is in an accelerating state is corrected to increase. Therefore, during acceleration, a decrease in the fuel injection amount due to a decrease in fuel pressure is prevented, and acceleration performance is improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the entire fuel supply system including a fuel pump control device according to a specific embodiment of the present invention, and FIG.
3 are flowcharts showing the processing procedure of CPt1 of the control device of the same embodiment, FIGS. 4 and 5 are characteristic diagrams showing the relationship between fuel injection amount and applied voltage, and FIG. is a characteristic diagram showing the relationship between the opening speed of the throttle valve and the asynchronous injection pulse width; FIGS. 7(a) to (i) are timing charts showing the operating characteristics of the device of this embodiment; a)
~(i) is a timing chart showing the operating characteristics of the conventional device. 1...-Engine 2...-Intake passage 4...°Fuel injection valve 5...Fuel supply passage 6"...Fuel tank 7
・-Fuel pump 10 ・-″Return passage 11--°・
Pressure regulator 12°゛°temperature sensor 14"゛air flow meter 16...°control device 24-・ISC
valve

Claims (1)

[Scope of Claims] According to the amount of fuel required by the internal combustion engine, the amount of fuel supplied to the fuel injection valve by the fuel pump is controlled, and the amount of fuel injected by the fuel injection valve is controlled, and the internal combustion engine is in an acceleration state. In this case, in the fuel injection control device that corrects the fuel injection amount according to the acceleration amount, when the internal combustion engine is in the acceleration state, the fuel injection amount is increased by the fuel pump and the fuel injection amount is increased by the fuel injection valve. a detection means for detecting a value related to a decrease in the pressure of fuel supplied to the fuel injection valve by the fuel pump caused by a difference in response speed with an increase in injection amount; A fuel injection control device comprising: a correction means for increasing the fuel injection amount when the internal combustion engine is in an acceleration state in accordance with a decrease in pressure of the internal combustion engine.