JPH09126029A - Method and device for controlling fuel pump of fuel injection device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel pump control method capable of obtaining the constant fuel pressure without being affected by the variance of the powersupply voltage or the performance of a pump motor. SOLUTION: The power-supply voltage of a pump motor 1 and the rotational speed of an internal combustion engine are detected, the fuel pressure is kept at the set value, and the duty ratio of the driving current to be supplied to the pump motor 1 to discharge the fuel of the required amount to obtain the required injection by the engine from a fuel pump 2 is operated to the power- supply voltage and the engine rotational speed. The driving current is PWM- controlled by connecting/disconnecting the driving current to be supplied to the pump motor 1 from a battery 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a fuel pump of a fuel injection device for supplying fuel to an internal combustion engine, and a fuel pump control device used for implementing the method.

[0002]

2. Description of the Related Art A fuel injection device for an internal combustion engine is a fuel pump driven by a pump motor supplied with a drive current from a DC power source to discharge fuel, and a fuel pump supplied with fuel to supply an injection command pulse. Injector for injecting fuel into the fuel injection space in the intake pipe or cylinder of the internal combustion engine during the injection time determined by the pulse width of the injection command pulse, and the pressure and fuel of the fuel supplied from the fuel pump to the injector. A pressure regulator that controls the pressure difference between the pressure in the injection space or the pressure between the fuel supplied from the fuel pump to the injector and the atmospheric pressure to keep it at a set value, and the fuel injection amount from the injector at each rotation speed. And a fuel injection control device for giving an injection command pulse to the injector so that the injection amount becomes equal to the required injection amount.

Generally, an injector includes a valve body having an injection port at its tip, a needle valve provided in the valve body for opening and closing the injection port, and a solenoid coil for driving the needle valve. Fuel is supplied from the fuel pump.

A drive current is applied to the solenoid coil of the injector through a drive circuit having a switching element such as a transistor which is turned on / off by an injection command pulse. When the injection command pulse is given to the drive circuit of the injector, the switching element in the drive circuit is turned on and a drive current is supplied to the solenoid coil of the injector. This opens the needle valve and injects the fuel supplied from the fuel pump. The amount of fuel injected from the injector (fuel injection amount) depends on the time during which the injection port is opened (injection time), the pressure of fuel given to the injector from the fuel pump, and the pressure in the fuel injection space or atmospheric pressure. It is determined by the differential pressure (this differential pressure will be referred to as fuel pressure in this specification).

There is a predetermined delay time between the injection of the injection command pulse to the drive circuit and the actual opening of the valve of the injector, and there is also a delay between the injection of the injection command pulse and the closing of the valve. Since the predetermined delay time exists, the pulse width of the injection command pulse and the actual injection time (effective injection time) are not equal, but the length of the effective injection time is determined by the pulse width of the injection command pulse. Therefore,
The effective injection time can be controlled by controlling the pulse width of the injection command pulse.

As described above, the fuel injection amount from the injector is determined by the fuel pressure and the effective injection time. However, if both of them are changed, the control becomes complicated. Therefore, the fuel pressure is practically kept constant by the pressure regulator. Control so that the fuel injection amount is almost uniquely determined by the pulse width of the injection command pulse, and the fuel injection amount is controlled by changing the pulse width of the injection command pulse according to various control conditions. I am trying.

The pressure regulator has, for example, a fuel chamber and a spring chamber in its housing, and a diaphragm is provided so as to partition the fuel chamber and the spring chamber, and the diaphragm is provided in the spring chamber. Is biased toward the fuel chamber by a spring. A valve that opens and closes between the inlet and the outlet of the fuel chamber is provided in the fuel chamber, the movable part of the valve is connected to the diaphragm, and the valve is normally urged by a spring in the spring chamber to close. Is held in a state. The inlet of the fuel chamber is connected to a pipe having the same pressure as the pressure on the fuel inlet side of the injector, and the outlet of the fuel chamber is connected to the fuel tank via a return pipe. The spring chamber is connected to the fuel injection space of the internal combustion engine.

When the pressure difference (fuel pressure) between the pressure inside the fuel chamber and the pressure inside the spring chamber exceeds a set value, the diaphragm is deformed toward the spring chamber side against the biasing force of the spring, and the inlet and outlet of the fuel chamber. Since the valve that has cut off the flow of fuel between the fuel tank and the fuel tank is opened, surplus fuel in the fuel supplied from the fuel pump to the injector returns to the fuel tank through the return pipe. As a result, when the fuel pressure falls below the set value, the diaphragm returns to its original shape and closes the valve. By these operations, the fuel pressure is maintained almost at the set value.

In this type of regulator, the control pressure is affected by the flow rate (return flow rate) of the surplus fuel that returns to the fuel tank side through the regulator, and if the return flow rate of the surplus fuel is too small or too large, control is performed. The fluctuation range of pressure becomes large and controllability deteriorates. Therefore, in order to keep the fuel pressure almost constant using this type of regulator, the amount of surplus fuel that returns to the fuel tank side through the regulator is within an appropriate range (a range where proper controllability of the pressure regulator is ensured). Need to keep.

As described above, in the fuel injection device,
In order to be able to control the fuel injection amount by the pulse width of the injection command pulse, it is necessary to keep the fuel pressure at the set value, and in order to do so, the fuel amount always exceeds the injection amount required by the engine. Needs to be supplied to the injector from the fuel pump. The fuel injection amount required by the engine is not constant but changes depending on various conditions such as the rotational speed, the atmospheric pressure, the engine temperature, and the operating condition of the engine. Therefore, conventionally, in anticipation of the maximum required injection amount of the engine and the drop of the power supply voltage, sufficient output is generated even when the power supply voltage is lower than the rated value so that the fuel pump can obtain the required discharge amount in any case. The fuel pump is operated by selecting the pump motor to be operated and driving the pump motor with a DC power source such as a battery.

[0011]

As described above, conventionally, even if the power supply voltage is lower than the regulation, the fuel pump has an output required to discharge an amount of fuel commensurate with the maximum expected injection amount. Select the pump motor,
Since the pump motor was driven by a direct current power source such as a battery, when the power supply voltage rises, the discharge amount from the fuel pump becomes too large, and excess fuel is fed back through the pressure regulator when the required injection amount is small. However, there is a problem in that the controllability of the pressure regulator deteriorates due to excessive pressure.

Further, in the conventional apparatus, the discharge amount from the fuel pump may not be the set value due to the variation in the performance of the pump motor, and the discharge amount from the fuel pump may become too large due to the variation in the performance of the pump motor. However, the amount of surplus fuel that returns to the fuel tank through the pressure regulator may deviate from the proper range depending on the required injection amount, and the controllability of the fuel pressure may deteriorate.

When the controllability of the fuel pressure by the pressure regulator becomes poor, the injection amount cannot be uniquely determined by the pulse width of the injection command pulse, so that the fuel injection amount cannot be controlled accurately. The desired performance cannot be obtained from the engine.

In particular, in the case of a two-cycle engine in which a part of unburned gas is discharged by blow-by, it is not possible to detect oxygen in the exhaust gas and perform feedback control for correcting the air-fuel ratio, so that fuel injection is performed. It is necessary to control the amount accurately, and for that purpose it is necessary to keep the controllability of the pressure regulator good and to keep the fuel pressure as constant as possible.

Conventionally, the pump motor is selected so that a sufficient amount of fuel is discharged from the fuel pump even when the power supply voltage is lower than the specified value. However, a pump motor that generates a large output at a low voltage is driven by a large amount. Since a current is required, power consumption increases, and there is a problem that wasteful power consumption increases during low speed operation with a small required injection amount. In particular, when the low-speed operation is continued for a long time, such as an outboard motor that performs trolling, the pump motor consumes much of the output of the magneto generator attached to the engine, so the battery charging There was a problem that could not be performed sufficiently.

An object of the present invention is to provide a fuel pump control method for a fuel injection device for an internal combustion engine, which can prevent the controllability of fuel pressure from being deteriorated due to fluctuations in power supply voltage and variations in pump motor performance. And to provide a fuel pump controller used to implement the method.

Another object of the present invention is to provide a fuel pump control method for a fuel injection device for an internal combustion engine, which is capable of preventing wasteful power consumption by a pump motor during low speed operation of the engine and the like. It is to provide a fuel pump controller used to carry out the method.

[0018]

According to the present invention, an injector mounted so as to inject fuel into a fuel injection space of an internal combustion engine and a pump motor supplied with a drive current from a DC power supply supply the injector with fuel. A fuel pump to supply, an injector drive circuit that drives the injector so that the fuel is injected from the injector for an injection time determined by the pulse width of the injection command pulse when the injection command pulse is given, and the injector from the fuel pump The pressure regulator that controls the pressure difference between the fuel pressure supplied to the engine and the pressure in the fuel injection space or the atmospheric pressure, and the fuel injection amount from the injector to be equal to the required injection amount at each rotational speed. The pulse width of the injection command pulse is calculated as In which it relates to a method for controlling a fuel pump for an internal combustion engine fuel injection system and a fuel injection control device for providing to the injector drive circuit as a command pulse.

In the present invention, the above-mentioned differential pressure (fuel pressure)
Is maintained at the set value and the drive current of the pump motor is PWM-controlled so that the fuel pump discharges the required amount of fuel to obtain the required injection amount.

As described above, the drive current of the pump motor is set to P
In the WM control, for example, the rotation speed of the internal combustion engine and the power supply voltage of the pump motor are detected, and the fuel pump supplies the fuel in an amount necessary to obtain the required injection amount while maintaining the differential pressure at a set value. The duty ratio of the drive current that needs to be supplied to the pump motor for discharging is calculated with respect to the power supply voltage and the rotation speed, and the drive current supplied from the battery to the pump motor is interrupted at the calculated duty ratio. You can do this.

Further, when the fuel injection control device calculates the pulse width of the injection command pulse so that the fuel injection amount from the injector is made equal to the required injection amount at each rotational speed, the calculated pulse width is calculated from the calculated pulse width. The discharge amount from the fuel pump required to obtain the required injection amount while maintaining the fuel pressure at the set value can be calculated as the required discharge amount. When the required discharge amount can be calculated in this way, the duty ratio of the drive current that needs to be supplied to the pump motor to obtain the required discharge amount for the detected power supply voltage is calculated, The drive current of the pump motor may be interrupted at the calculated duty ratio.

The fuel pump control system according to the present invention is driven by an injector mounted so as to inject fuel into a fuel injection space of an internal combustion engine and a pump motor to which a driving current is supplied from a DC power source, to inject fuel into the injector. A fuel pump to supply, an injector drive circuit that drives the injector so that the fuel is injected from the injector for an injection time determined by the pulse width of the injection command pulse when the injection command pulse is given, and the injector from the fuel pump The pressure regulator that controls the pressure difference between the fuel pressure supplied to the engine and the pressure in the fuel injection space or the atmospheric pressure, and the fuel injection amount from the injector to be equal to the required injection amount at each rotational speed. And calculate the pulse width of the injection command pulse as A device for controlling the fuel pump of an internal combustion engine fuel injection system having a fuel injection control device for providing to the injector drive circuit a pulse as the injection command pulse having a pulse width.

In the present invention, the rotational speed detecting means for detecting the rotational speed of the internal combustion engine, the power source voltage detecting means for detecting the power source voltage of the pump motor, and the differential pressure are maintained at a set value to obtain the required injection amount. In order to discharge the required amount of fuel from the fuel pump in order to store the duty ratio calculation map that gives the relationship between the duty ratio of the drive current that needs to be supplied to the pump motor and the power supply voltage and the rotation speed of the internal combustion engine. A map storage means, a duty ratio calculation means for calculating the duty ratio of the drive current by using the map with respect to the rotation speed detected by the rotation speed detection means and the power supply voltage detected by the power supply voltage detection means; Fuel pump control by providing a drive current control switch for connecting and disconnecting the drive current at the duty ratio calculated by the ratio calculation means To configure the location.

The fuel pump control device of the present invention also maintains the differential pressure at a set value from the pulse width calculated by the fuel injection control device and the power supply voltage detecting means for detecting the power supply voltage of the pump motor, and thereby the required injection amount. A discharge amount calculation means for calculating a discharge amount required from the fuel pump as a necessary discharge amount, and a duty ratio of a drive current and a power supply voltage required to be supplied to the pump motor to obtain the required discharge amount. And a map storage means for storing a duty ratio calculation map for giving the relationship of: and a duty ratio calculation means for calculating the duty ratio of the drive current with respect to the power supply voltage detected by the power supply voltage detection means using the duty ratio calculation map. When,
A drive current control switch for connecting and disconnecting the drive current of the pump motor at the calculated duty ratio can also be used.

In the present specification, the "duty ratio" of the drive current means the drive current when the drive current is PWM-controlled by alternately generating a period Ton for flowing the drive current and a period Toff for cutting off the drive current. Ratio of ON period Ton to ON / OFF cycle Ton + Toff [= Ton / (Ton +
Toff)] is meant.

As described above, when the drive current of the pump motor is PWM-controlled so that the fuel pump discharges the amount of fuel required to obtain the required injection amount while maintaining the fuel pressure at the set value, the power source of the fuel pump Regardless of whether the voltage is high or low, and is not affected by variations in pump motor performance, the discharge rate from the fuel pump is always kept in an appropriate range (a range in which good controllability of the pressure regulator can be secured). Thus, the fuel pressure can be kept almost constant.

Further, with the above configuration, at the time of low speed operation in which the fuel injection amount required by the engine is small, the minimum fuel required to secure a constant fuel pressure by reducing the duty ratio of the drive current of the pump motor. Since it can be discharged from the fuel pump, the power consumption of the pump motor can be reduced and the output of the magnet generator can be used for charging the battery. Therefore, even when the low speed operation is performed for a long time like an outboard motor that performs trolling, it is possible to maintain an appropriate operating state of the engine without depleting the battery.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the hardware configuration of an apparatus used to carry out the control method of the present invention. In FIG. 1, 1 is a pump motor for driving a fuel pump 2, and 3 is a pump motor. A battery constituting a DC power source for driving the motor, 4 a CPU of a microcomputer, 5 a signal generator for generating a signal for giving rotation angle information and rotation speed information of the internal combustion engine 6, and 7 a cylinder of the internal combustion engine. An ignition circuit that gives a high voltage for ignition to the attached spark plug,
Reference numeral 8 is an injector mounted so as to inject fuel into a fuel injection space such as an intake pipe of the internal combustion engine 6, and 9 is a CP.
It is an injector drive circuit that supplies a drive current to the injector 8 when U generates an injection command pulse. Also 10
Is a power supply voltage detection interface circuit that detects the output voltage of the battery 3 (pump motor power supply voltage) and inputs it to the CPU 4. 11 is a MOSF that constitutes a drive current control switch that turns on and off the drive current flowing to the pump motor 1.
ET and 12 are FET drive circuits (switch drive circuits) that give a drive signal of a pulse waveform intermittently at a predetermined duty ratio to the gate of the FET 11 according to the drive command signal Vj output from the CPU 4, and 13 is connected to both ends of the motor 1. A diode is provided, 14 is a fuel tank, and 15 is a pressure regulator.

More specifically, one end of the pump motor 1 is connected to the positive terminal of the battery 3 via the switch SW, and the other end is connected to the drain of the MOSFET 11. The negative terminal of the battery 3 and the source of the FET 11 are grounded, and a diode 13 is connected to both ends of the motor 1 with its cathode facing the positive terminal of the battery 1. The MOSFET 11 is of N-channel type and has a parasitic diode 11a between its drain and source.

The signal generator 5 is mounted on an internal combustion engine and generates a pulse signal at a fixed rotation angle position of a crankshaft, and a signal generator CP which outputs an output pulse from the signal generator.
It is composed of a waveform shaping circuit which converts the signal into a waveform that U4 can recognize and inputs it to the CPU 4.

The CPU 4 obtains the engine rotation angle information from the pulse signal output from the signal generator 5, and calculates the engine rotation speed from the generation period of the pulse signal. CP
U4 also calculates the pulse width of the injection command pulse that gives the fuel injection amount at the calculated rotation speed, using the outputs of various sensors such as a sensor that detects the opening of the throttle valve and a sensor that detects the intake air temperature. Then, the injector drive circuit 9 is provided with an injection command pulse Vj having a pulse width calculated when the fuel injection position is detected based on the rotational angle position information obtained from the pulse signal generated by the signal generator 5.

The CPU 4 also calculates the ignition position at each rotational speed of the engine, measures the ignition position calculated from a predetermined reference position, and outputs the ignition signal Vi to the ignition circuit 7 when the ignition position is measured. give.

The ignition circuit 7 is composed of a capacitor discharge type circuit and a current interruption type circuit, and when the ignition signal Vj is given from the CPU 4, the primary current of the ignition coil is suddenly changed for ignition. Outputs the high voltage Vh of. Since this high voltage is applied to the spark plug attached to the cylinder of the internal combustion engine 6, a spark is generated in the spark plug and the engine is ignited.

The injector drive circuit 9 is a circuit provided with a switch element such as a transistor which is turned on while the injection command pulse Vj is applied, and drives the solenoid coil of the injector 8 while the switch element is on. Apply current.

The drive command signal Vd output from the CPU 4 is
This is a pulse waveform signal which is intermittent with a duty ratio equal to the duty ratio of the drive current of the pump motor 1. When the duty ratio of the drive current is 100%, it is a DC signal with a constant level.

The FET drive circuit 12 is a circuit provided with a switch means which is turned on / off by a drive command signal Vd output from the CPU 4, and a drive command signal Vd is supplied from a DC power supply circuit (not shown) between the gate and source of the FET 11 through the switch means. A drive signal Vg which is intermittently applied with the same duty ratio as the above is given.

The fuel pump 2 sucks the fuel in the fuel tank 14 and feeds the fuel into the fuel inlet 8 of the injector 8.
Discharge to the conduit connected to a. The fuel pump 2 may be arranged in the fuel tank 14,
It may be arranged outside the.

The injector 8 includes an injection port opened in a fuel injection space (for example, an intake pipe) of the internal combustion engine, a needle valve for opening and closing the injection port, and a solenoid (electromagnet) for driving the needle valve. Then, fuel having a predetermined pressure is supplied to the fuel inlet port, and when a drive current is applied to the solenoid coil, the needle valve opens and the fuel is injected from the injection port.

The illustrated injector 8 is of a so-called side-feed type, which has a fuel inlet 8a and a fuel outlet 8b on the side surface of the body of the injector, and one of the fuel introduced into the body from the inlet 8a. The part is provided to the pressure regulator through the outflow port 8b.

The injector 8 is not limited to the side-feed type, but a bottom-feed type in which fuel is introduced from the lower part of the main body and a part of it is discharged from the upper part to be supplied to the pressure regulator,
Alternatively, there is a top feed type in which fuel is introduced from the upper part of the main body.

The pressure regulator 15 has a fuel chamber 15b and a spring chamber 15c in a housing 15a thereof, and a diaphragm 15d is provided so as to partition the fuel chamber and the spring chamber, and the diaphragm is a spring. It is biased toward the fuel chamber by a spring 15e provided inside the chamber. A valve 15f that opens and closes between an inlet and an outlet of the fuel chamber is provided in the fuel chamber 15b, a movable side of the valve is connected to a diaphragm 15d, and the valve is normally biased by a spring 15e. It is held closed. The inlet of the fuel chamber 15b is connected to a pipe 16 having the same pressure as the pressure on the fuel inlet side of the injector 8, and the outlet of the fuel chamber 15b is connected to the fuel tank 14 via a return pipe 17. In the illustrated example, the spring chamber 15c is connected to the fuel injection space of the internal combustion engine 6 (for example, in the intake pipe).

Although not shown in FIG. 1, a magnet generator is attached to the internal combustion engine, and the output of the magnet generator is input to a rectifier circuit having a voltage adjusting function. The battery 3 is adapted to be charged. When a power generation coil that generates an AC voltage in synchronization with the rotation of the engine is used as the power source of the ignition circuit 7, the power generation coil is provided in the magnet power generator.

In the apparatus of FIG. 1, the CPU 4 causes
A fuel injection control device that controls the injection position (injection timing) and the injection time of the fuel from the injector 8 under control conditions such as rotation speed, throttle opening, atmospheric pressure, intake air temperature, and the like. An ignition position control device that controls the ignition position (ignition timing) is configured.

The microcomputer has a ROM, a RAM, a timer, a register and the like in addition to the CPU 4, but these are not shown.

In the apparatus shown in FIG. 1, when the switch SW is turned on, a power supply voltage (not shown) is applied to the CPU 4 to start the CPU 4. CPU4 is FE
A drive command signal which is intermittent at a predetermined duty ratio is given to the T drive circuit 12 to turn on / off the FET 11. As a result, a drive current is supplied to the pump motor 1, so that the motor rotates and fuel is supplied from the fuel pump 2 to the injector 8.

In FIG. 6, the drive command signal V having a duty ratio of 100% is sent from the CPU 4 to the FET drive circuit 12 at time t1.
It shows the response of the fuel pump when d is given. As shown in the figure, the discharge amount Q from the fuel pump 2 gradually increases with a predetermined delay after the pump motor 1 is driven. The relationship between the discharge amount Q from the fuel pump 2 and the applied voltage Vp to the pump motor 1 is as shown in FIG. 7, for example, and the discharge amount Q from the fuel pump 2 changes greatly with the change in the applied voltage Vp.

When the difference (fuel pressure) between the pressure of the fuel supplied from the fuel pump 2 to the injector 8 and the pressure of the fuel injection space of the internal combustion engine exceeds a set value, the valve 15f of the pressure regulator 15 is opened to remove excess fuel. The fuel is returned to the fuel tank 14 through the return pipe 17, and the pressure of the fuel applied to the injector 8 (relative pressure to the pressure in the fuel injection space = fuel pressure) is maintained at a set value.

When the internal combustion engine is started and the crankshaft of the engine rotates, the signal generator 5 generates a pulse signal at a predetermined rotational angle position. The CPU 4 obtains the rotational angle information of the engine from this pulse signal, calculates the rotational speed from the generation period of the pulse signal, and calculates the ignition position of the engine and the pulse width of the injection command pulse at the calculated rotational speed. The CPU 4 sends the injection command pulse Vj to the injector drive circuit 9 when detecting that the rotational angle position of the crankshaft of the engine coincides with the fuel injection position.
give. The injector drive circuit 9 uses the injection command pulse V
Since a drive current is applied to the injector 8 while j is given, the valve of the injector 8 is opened and fuel is injected from the injector into the fuel injection space of the engine.

The CPU 4 also gives an ignition signal Vi to the ignition circuit 7 when it is detected that the rotational angle position of the crankshaft coincides with the calculated ignition position. This triggers the ignition circuit 7 to generate a high voltage Vh for ignition, so that the engine is ignited.

In the above apparatus, if the discharge amount from the fuel pump 2 is Q, the amount of fuel injected from the injector 8 is Qi, and the flow rate of excess fuel returned to the fuel tank 14 through the pressure regulator 15 is Qr, The formula is established.

Q = Qi + Qr (1) In the equation (1), the fuel injection amount (required injection amount) Qi required at each rotational speed of the engine depends on the atmospheric pressure, the intake air temperature, the operating condition of the engine, etc. It changes and is not constant. For example, as shown in FIG. 8, even when the engine speed N increases uniformly with the passage of time t, the accelerator pedal (or accelerator grip) is abruptly displaced toward the acceleration side during the process. If so, the required injection amount Qi is greatly increased in order to maintain the predetermined air-fuel ratio. Therefore, the relationship between the engine rotation speed N and the required injection amount Qi cannot be represented by a single curve or straight line.
It will have a considerable spread as shown by the diagonal lines.

As described above, the required injection amount Qi at each rotational speed of the internal combustion engine greatly changes with changes in various conditions. Therefore, when the discharge amount Q from the fuel pump is fixed, the pressure regulator 15 is used. Fuel tank 1
The flow rate Qr of the surplus fuel returning to the 4th side also changes significantly with the change of the control condition, but in order to maintain the controllability of the pressure regulator well, the flow rate Qr of the surplus fuel is set to an appropriate range. Need to keep.

FIG. 10 shows the flow rate Qr of the surplus fuel returned to the fuel tank 14 side through the pressure regulator 15.
3 shows an example of the relationship between the pressure and the control pressure P of the pressure regulator 15. In this example, in order to maintain the control pressure P at a substantially constant set value, it is necessary to maintain the surplus fuel flow rate Qr between the lower limit value Qr1 and the upper limit value Qr2.

When the controllability of the pressure regulator becomes poor, the fuel pressure largely deviates from the set value, so that the fuel injection amount cannot be determined by the pulse width of the injection command pulse Vj, and the fuel injection amount can be controlled properly. Can not be.

Conventionally, considering the variation in the performance of the pump motor 1 and the variation range of the required injection amount at each rotation speed (FIG. 9), even when the required injection amount Qi becomes maximum at each rotation speed, The discharge amount Q of the fuel pump is set so that a predetermined surplus fuel Qr can flow, and a pump motor 1 having an output required to obtain a predetermined protrusion amount Q even when the power supply voltage is lower than the regulation is provided. The pump motor is selected and driven by a DC power supply.

However, in such a configuration, when the power supply voltage is high, the flow rate Qr of the surplus fuel exceeds the upper limit value Qr2, the controllability of the pressure regulator deteriorates, and the fuel pressure may exceed the set value. It was

When a pump motor which produces a large output at a low voltage is used, useless power is consumed by the pump motor at low speed when the required injection amount is small, which is not preferable. In particular, in the case of an outboard motor that may be operated at low speed for a long time, if the power consumption of the pump motor increases at low speed, the battery cannot be sufficiently charged, which is not preferable.

Also, due to variations in the performance of the pump motor, the flow rate Qr of the surplus fuel returning to the fuel tank may fall below the lower limit value or exceed the upper limit value Qr2, and the controllability of the pressure regulator may deteriorate. .

In order to prevent these problems from occurring, in the present invention, the pump motor is arranged so that the fuel pump 2 discharges the amount of fuel required to obtain the required injection amount while maintaining the fuel pressure at the set value. The drive current of 1 is PWM-controlled.

In order to control the injector and the ignition position by the CPU 4, for example, the rotational speed is calculated, the ignition position is calculated, the calculated ignition position is measured, and the injection time (the pulse width of the injection command pulse is set). Computation), injection position detection, fuel pump control, etc. are prepared in advance, and a multitasking system that performs these tasks in a predetermined order is used to achieve accurate control. It can be done. FIG. 2 shows an algorithm of a task k executed by the CPU 4 to carry out the control method according to the present invention. In this task k, first, the power supply voltage is detected through the power supply voltage detecting interface circuit 10 (see FIG. 1). In the example, the voltage of the battery 3) is read. The power supply voltage detecting means is realized by the power supply voltage detecting interface circuit 10 and the process of reading the power supply voltage through the circuit.

After reading the power supply voltage, the rotational speed of the engine is calculated from the generation cycle of the output pulse of the signal generator 5 read in another task. The rotation speed detecting means is realized by this process.

Next, the amount of fuel required to maintain the fuel pressure at a substantially constant set value and obtain the required injection amount (in order to keep the flow rate Qr of the surplus fuel in the range between Qr1 and Qr2 in FIG. 9). Calculation is performed using a duty ratio calculation map that gives the relationship between the duty ratio D of the drive current that needs to be supplied to the pump motor to discharge the required amount of fuel) from the fuel pump, the power supply voltage Vp, and the rotation speed. The duty ratio D of the drive current required to maintain the fuel pressure at the set value and obtain the required injection amount is calculated by the interpolation method with respect to the determined rotation speed and the detected power supply voltage. By this process, a duty ratio calculation means for calculating the duty ratio of the drive current with respect to the rotation speed and the power supply voltage is realized.

After calculating the duty ratio D, the drive command signal Vd having a pulse waveform which is intermittent at the calculated duty ratio.
To the FET drive circuit 12. This makes FET11
The (drive current control switch) is turned on / off at the calculated duty ratio D, and the drive current of the pump motor 1 is PWM.
Control.

The duty ratio calculation map used for calculating the duty ratio of the drive current of the pump motor is shown in FIG.
3 is a three-dimensional map having the structure shown in FIG. In the figure, N0, N1, ..., Nm are values that the engine speed N can take, and Vp0, Vp1, Vp2, ... Vpn are values that the power supply voltage Vp of the pump motor 1 can take. Also D00-D
0n, D10 to D1n, ... Dmo to Dmn are duty ratios of drive currents. The data forming this map is stored in the ROM or EEPROM of the microcomputer. The duty ratio of the drive current that must be supplied to the pump motor in order to discharge the amount of fuel required to maintain the fuel pressure at the set value and obtain the required injection amount from the fuel pump, using the ROM that stores the map or the EEPROM. And a map storage means for storing a duty ratio calculation map that gives the relationship between the power supply voltage and the rotation speed.

The duty ratio values forming the map of FIG. 3 are the dispersion of the performance of the pump motor, the fluctuation range of the power supply voltage, the fluctuation range of the injection amount Qi required at each rotation speed, and the control of the pressure regulator. In consideration of the characteristics, the flow rate Qr of the surplus fuel is set so that it always falls within an appropriate range.

The pump motor 1 is selected so that the fuel pump 2 can discharge a sufficient amount of fuel even when the power supply voltage is low. Even if such a pump motor is used, the duty ratio of the drive current when the power supply voltage is the specified value is made small so that the minimum required fuel is discharged from the fuel pump at low speed when the required injection amount is small. By creating a map in, it is possible to prevent unnecessary power consumption at low speed. Also, by creating a map so that the duty ratio of the drive current is increased for a low power supply voltage, the required discharge amount can be secured even if the power supply voltage becomes lower than the specified value. .

In the above example, the rotation speed detecting means for detecting the rotation speed of the internal combustion engine 6, the power supply voltage detecting means for detecting the power supply voltage of the pump motor 1, and the required injection amount while maintaining the fuel pressure at the set value. A duty ratio calculation map that gives the relationship between the duty ratio of the drive current that needs to be supplied to the pump motor 1 in order to discharge the amount of fuel necessary to obtain it from the fuel pump 2 and the power supply voltage and the rotation speed is stored. A map storage means, a duty ratio calculation means for calculating the duty ratio of the drive current using a map for the rotation speed detected by the rotation speed detection means and the power supply voltage detected by the power supply voltage detection means; A fuel pump control device is constituted by a drive current control switch (FET 11) for connecting and disconnecting the drive current at the duty ratio calculated by the calculation means. It is.

As described above, when the drive current of the pump motor is PWM-controlled so that the fuel pump discharges the amount of fuel required to obtain the required injection amount while maintaining the fuel pressure at the set value, Since the discharge rate can always be kept within an appropriate range (a range where good controllability of the pressure regulator can be secured), it does not matter whether the power supply voltage of the fuel pump is high or low, and there is no fluctuation in the performance of the pump motor. Regardless of the above, it is possible to appropriately control the fuel injection amount while keeping the fuel pressure substantially constant.

Further, at the time of low speed operation in which the amount of fuel injection required by the engine is small, the duty ratio of the drive current of the pump motor is reduced to discharge the minimum amount of fuel necessary for ensuring a constant fuel pressure from the fuel pump. Therefore, the power consumption of the pump motor can be reduced and the output of the magnet generator can be used for charging the battery. Therefore, even when the low speed operation is performed for a long time like an outboard motor that performs trolling, it is possible to maintain an appropriate operating state of the engine without depleting the battery.

In the above example, the duty ratio of the drive current of the pump motor 1 is calculated using the three-dimensional map that gives the relationship between the power supply voltage, the engine speed, and the duty ratio of the drive current of the pump motor 1. However, the discharge amount from the fuel pump 2 required to obtain the required injection amount while maintaining the fuel pressure at the set value is determined from the pulse width of the injection command pulse calculated by the CPU 4 which constitutes the fuel injection control device. It is also possible to calculate the required discharge amount and calculate the duty ratio of the drive current that needs to be supplied to the pump motor 1 to obtain the required discharge amount for the detected power supply voltage. The algorithm of task k in this case is shown in FIG.

That is, since the CPU 4 calculates the pulse width of the injection command pulse Vj that gives the required injection amount Qi at each rotational speed, the required injection amount Qi at each rotational speed can be calculated from the pulse width. , Its injection quantity Qi
Therefore, the discharge amount from the fuel pump 2 required to maintain the fuel pressure at the set value and obtain the required injection amount (flow rate Q of surplus fuel
The ejection amount required to keep r within an appropriate range can be calculated as the required ejection amount. If the required discharge amount can be calculated, the duty ratio D of the drive current required to obtain the required discharge amount can be calculated for the detected power supply voltage, so that the fuel pressure can be maintained at the set value. Fuel pump 2 supplies the required amount of fuel to obtain the required injection amount
Drive current of the pump motor 1 to discharge from the PW
M control is possible.

In this case, the fuel pressure is kept at the set value from the power supply voltage detecting means for detecting the power supply voltage of the pump motor 1 and the pulse width of the injection command pulse calculated by the fuel injection control device realized by the CPU 4. It is necessary to supply the amount of discharge from the fuel pump required to secure the required injection amount to the pump motor in order to obtain the required amount of discharge, which is realized by the process of calculating the required amount of discharge by the CPU. A map storage unit that stores a duty ratio calculation map that gives a relationship between a duty ratio of a certain drive current and a power supply voltage, and a drive current for the power supply voltage detected by the power supply voltage detection unit using the duty ratio calculation map. Of the duty ratio of the pump and the pump ratio based on the calculated duty ratio. Driving current control switch to interrupt the driving current of the motor and (FET 11) fuel pump control device is constituted by.

According to this method, the duty ratio of the drive current of the pump motor is calculated using a two-dimensional map that gives the relationship between the power supply voltage Vp and the duty ratio Dn of the drive current as shown in FIG. Therefore, the structure of the map can be simplified, the calculation speed can be improved, and
It is possible to save the memory of the microcomputer.

In the above description, the battery 3 is used as the DC power supply for driving the pump motor, but the output of the DC power supply circuit using the power generation coil in the magnet generator installed in the internal combustion engine as the power supply without using the battery. The present invention can also be applied to the case where the pump motor 1, the CPU 4, the injector 8, the injector drive circuit 9 and the like are driven.

The present invention is particularly effective for a two-cycle engine in which it is necessary to accurately control the fuel injection amount, but it goes without saying that it can be applied to a four-cycle engine.

In the above description, the drive current control switch for turning on / off the drive current of the pump motor is constituted by the FET 11, but other switch elements such as transistors may be used as this switch.

In the example shown in FIG. 1, the spring chamber of the pressure regulator 15 is connected to the fuel injection space (for example, the intake pipe) of the internal combustion engine, and the pressure of the fuel given to the injector from the fuel pump and the pressure of the fuel injection space are connected. The pressure difference between the fuel pressure supplied to the injector and the pressure difference between the fuel supplied from the fuel pump to the injector and the atmospheric pressure is controlled by the pressure regulator. You may make it hold | maintain at a setting value.
For example, when an injector is individually attached to each cylinder of a multi-cylinder internal combustion engine and fuel is directly injected into each cylinder,
Since the fuel injection space is different for each cylinder, the pressure regulator 15 is used with its spring chamber open to the outside air. In this case, the pressure regulator controls so that the pressure difference between the pressure of the fuel supplied from the fuel pump to the injector and the atmospheric pressure is maintained at the set value.

[0078]

As described above, according to the present invention, the drive current of the pump motor is controlled so that the fuel pump discharges the required amount of fuel to maintain the fuel pressure at the set value and obtain the required injection amount. Since the PWM control is used, the pressure regulator control is performed by always maintaining the discharge amount from the fuel pump within an appropriate range, regardless of whether the power supply voltage of the fuel pump is high or low, and without being affected by variations in the performance of the pump motor. It is possible to maintain good sex. Therefore, the fuel pressure can always be kept substantially constant, and the fuel injection amount can be controlled appropriately.

Further, according to the present invention, at the time of low speed operation in which the fuel injection amount required by the engine is small, the minimum amount of fuel required to secure a constant fuel pressure by reducing the duty ratio of the drive current of the pump motor is provided. Since the fuel can be discharged from the fuel pump, the power consumption of the pump motor can be reduced and the output of the magnet generator can be used for charging the battery. Therefore, even when the low speed operation is performed for a long time like an outboard motor that performs trolling, it is possible to maintain an appropriate operating state of the engine without depleting the battery.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing an example of an algorithm of a task executed when implementing the control method of the present invention.

FIG. 3 is a map configuration diagram showing a configuration of a duty ratio calculation map used when implementing the control method of the present invention.

FIG. 4 is a flowchart showing another example of the algorithm of the task executed when the control method of the present invention is carried out.

5 is a map configuration diagram showing a configuration of a duty ratio calculation map used in the case of the method shown in FIG.

FIG. 6 is a diagram showing a response of the fuel pump when a power supply voltage is applied to the pump motor.

FIG. 7 is a diagram showing an example of the relationship between the applied voltage of the pump motor and the discharge amount from the fuel pump.

FIG. 8 is a diagram showing an example of a temporal change in the rotational speed of the internal combustion engine and a temporal change in the fuel injection amount.

FIG. 9 is a graph showing the relationship between the engine speed and the injection amount required by the engine.

FIG. 10 is a diagram showing an example of control characteristics of a pressure regulator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pump motor 2 Fuel pump 3 Battery 4 CPU 5 Signal generator 6 Internal combustion engine 8 Injector 9 Injector drive circuit 10 Power supply voltage detection interface circuit 11 MOSFET 12 FET drive circuit constituting a switch circuit 14 Fuel tank 15 Pressure regulator

Claims (5)

[Claims] 1. An injector mounted to inject fuel into a fuel injection space of an internal combustion engine, a fuel pump driven by a pump motor supplied with a drive current from a DC power source to supply fuel to the injector, and an injection. An injector drive circuit that drives the injector to inject fuel from the injector for an injection time determined by the pulse width of the injection command pulse when a command pulse is given, and fuel supplied from the fuel pump to the injector. Pressure regulator that controls the pressure difference between the fuel injection space and the pressure in the fuel injection space or the atmospheric pressure to be maintained at a set value, and an injector drive circuit that makes the fuel injection amount from the injector equal to the required injection amount at each rotational speed. Internal combustion engine provided with a fuel injection control device for giving the injection command pulse to A method of controlling the fuel pump of a fuel injection device for a vehicle, wherein the pump motor is configured to discharge an amount of fuel required to obtain the required injection amount by maintaining the differential pressure at a set value. The method for controlling a fuel pump of an internal combustion engine fuel injection device is characterized by performing PWM control of the driving current of the above. 2. An injector mounted to inject fuel into a fuel injection space of an internal combustion engine, a fuel pump driven by a pump motor supplied with a drive current from a DC power source to supply fuel to the injector, and an injection. An injector drive circuit that drives the injector to inject fuel from the injector for an injection time determined by the pulse width of the injection command pulse when a command pulse is given, and fuel supplied from the fuel pump to the injector. Pressure regulator that controls the pressure difference between the fuel injection space and the pressure in the fuel injection space or the atmospheric pressure to keep it at a set value, and an injector drive circuit that makes the fuel injection amount from the injector equal to the required injection amount at each rotational speed. Internal combustion engine provided with a fuel injection control device for giving the injection command pulse to A method for controlling the fuel pump of a fuel injection device for a vehicle, comprising detecting a rotation speed of the internal combustion engine, detecting a power supply voltage of the pump motor, and maintaining the differential pressure at a set value to obtain the required injection amount. The duty ratio of the drive current required to be supplied to the pump motor in order to discharge the required amount of fuel from the fuel pump is calculated with respect to the power supply voltage and the rotation speed, and the calculated duty ratio is calculated. 2. A fuel pump control method for a fuel injection device for an internal combustion engine, wherein the drive current supplied from the DC power supply to the pump motor is intermittently controlled by PWM control of the drive current. 3. An injector mounted to inject fuel into a fuel injection space of an internal combustion engine, a fuel pump driven by a pump motor supplied with a drive current from a DC power source to supply fuel to the injector, and an injection. An injector drive circuit that drives the injector to inject fuel from the injector for an injection time determined by the pulse width of the injection command pulse when a command pulse is given, and fuel supplied from the fuel pump to the injector. Pressure regulator that controls the pressure difference between the fuel injection space and the pressure in the fuel injection space or atmospheric pressure to maintain a set value, and an injection command pulse that makes the fuel injection amount from the injector equal to the required injection amount at each rotational speed. Pulse width of the injection command pattern A method for controlling the fuel pump of a fuel injection device for an internal combustion engine, comprising: a fuel injection control device that is supplied to an injector drive circuit as a loss, the differential pressure being set value from a pulse width calculated by the fuel injection control device. The discharge amount from the fuel pump required to obtain the required injection amount is calculated as the required discharge amount, the power supply voltage of the pump motor is detected, and the required discharge amount is calculated with respect to the detected power supply voltage. An internal combustion engine characterized by calculating a duty ratio of a drive current that needs to be supplied to a pump motor in order to obtain the PWM current, and intermittently controlling the drive current of the pump motor at the calculated duty ratio to perform PWM control of the drive current. A fuel pump control method for an engine fuel injection device. 4. An injector mounted to inject fuel into a fuel injection space of an internal combustion engine, a fuel pump driven by a pump motor supplied with a drive current from a DC power source to supply fuel to the injector, and an injection. An injector drive circuit that drives the injector to inject fuel from the injector for an injection time determined by the pulse width of the injection command pulse when a command pulse is given, and fuel supplied from the fuel pump to the injector. Pressure regulator that controls the pressure difference between the fuel injection space and the pressure in the fuel injection space or atmospheric pressure to maintain a set value, and an injection command pulse that makes the fuel injection amount from the injector equal to the required injection amount at each rotational speed. Having a pulse width equal to the pulse width calculated by calculating the pulse width of A fuel pump control device for controlling the fuel pump of the fuel injection device for an internal combustion engine, comprising: a fuel injection control device for giving the injection command pulse to the injector drive circuit, wherein a rotation speed of the internal combustion engine is detected. Rotational speed detection means, power supply voltage detection means for detecting the power supply voltage of the pump motor, and the fuel pump to discharge the amount of fuel required to obtain the required injection amount while maintaining the differential pressure at a set value. For storing the duty ratio calculation map that gives the relationship between the duty ratio of the drive current that needs to be supplied to the pump motor, the power supply voltage, and the rotation speed, and the rotation speed detection means. The rotation speed and the power supply voltage detected by the power supply voltage detection means are used to determine the duty ratio of the drive current using the map. A fuel pump control for a fuel injection device for an internal combustion engine, comprising: a duty ratio calculating means for calculating; and a drive current control switch for connecting and disconnecting the drive current at the duty ratio calculated by the duty ratio calculating means. apparatus. 5. An injector mounted so as to inject fuel into a fuel injection space of an internal combustion engine, a fuel pump driven by a pump motor supplied with a drive current from a DC power source to supply fuel to the injector, and an injection. An injector drive circuit that drives the injector to inject fuel from the injector for an injection time determined by the pulse width of the injection command pulse when a command pulse is given, and fuel supplied from the fuel pump to the injector. Pressure regulator that controls the pressure difference between the fuel injection space and the pressure in the fuel injection space or atmospheric pressure to maintain a set value, and an injection command pulse that makes the fuel injection amount from the injector equal to the required injection amount at each rotational speed. Having a pulse width equal to the pulse width calculated by calculating the pulse width of A fuel pump control device for controlling the fuel pump of a fuel injection device for an internal combustion engine, comprising: a fuel injection control device for giving the injection command pulse to the injector drive circuit, wherein a power supply voltage of the pump motor is detected. The discharge amount from the fuel pump required to secure the required injection amount by maintaining the differential pressure at a set value from the pulse width calculated by the power supply voltage detection means and the fuel injection control device is calculated as the required discharge amount. A discharge amount calculation unit; a map storage unit that stores a duty ratio calculation map that gives a relationship between the duty ratio of the drive current that needs to be supplied to the pump motor to obtain the required discharge amount and the power supply voltage; The duty ratio of the drive current is calculated with respect to the power supply voltage detected by the power supply voltage detection means using the duty ratio calculation map. A fuel pump control device for a fuel injection device for an internal combustion engine, comprising: a duty ratio calculating means for calculating; and a drive current control switch for connecting and disconnecting the drive current of the pump motor at the calculated duty ratio.