JPH09126027A - Fuel pressure control device for fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel pressure control device capable of obtaining the constant fuel pressure without being affected by the variance of the power supply voltage or the performance of a pump motor. SOLUTION: A fuel pressure control device is provided with a fuel flow sensor 16 to detect the flow rate of the fuel to be returned to a fuel tank 14 through a pressure regulator 15 to adjust the pressure of the fuel to be fed from a fuel pump 2 to an injector 9. The driving current of a pump motor 1 is PWM controlled so that the output signal of the fuel flow sensor 16 is kept at the target value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel pressure control device for a fuel injection device, which controls the pressure of fuel supplied from a fuel pump of a fuel injection device which supplies fuel to an internal combustion engine.

[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 unit for giving an injection command pulse to the drive circuit of the injector so as to equalize the required injection amount in .

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. Another object of the present invention is to provide a fuel pressure control device for a fuel injection device used for carrying out 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 an object of the invention to provide a fuel pressure control device for a fuel injector used for carrying out the method.

[0018]

SUMMARY OF THE INVENTION The present invention includes an injector for injecting fuel into a fuel injection space of an internal combustion engine, and a fuel pump driven by a pump motor supplied with a driving current from a DC power source to supply the fuel to the injector. , Equipped with a pressure adjusting valve that opens when the pressure difference between the fuel pressure supplied to the injector from the fuel pump and the fuel injection space pressure or atmospheric pressure exceeds a set value, and the fuel pump supplies the injector The fuel is supplied from the fuel pump of the fuel injection device for an internal combustion engine to the injector, which includes a pressure regulator for controlling a part of the fuel to return to the fuel tank side through the pressure adjusting valve so as to maintain the differential pressure at a set value. The present invention relates to a fuel pressure control device for a fuel injection device, which controls the pressure of fuel to be injected.

In the present invention, a fuel flow sensor for outputting an electric signal containing information on the flow rate of fuel returning to the fuel tank through the pressure regulator, and an output of the fuel flow sensor as an input, the output of the sensor as a target value. A PWM control unit for performing PWM control (pulse width modulation control) of the drive current of the pump motor is provided so as to keep the above.

The above fuel flow sensor is, for example,
A resistance heating element inserted into the flow path of the fuel returning to the fuel tank through the pressure regulator, and a detection unit for detecting a change in the resistance value of the resistance heating element.

The fuel flow sensor is provided in a flow passage of fuel returning to the fuel tank through a pressure regulator in a state of being biased in a direction against the flow of the fuel, and corresponds to the flow rate of the fuel in the flow passage. It is also possible to configure the movable body that causes the above displacement and the displacement amount sensor that generates an electric signal corresponding to the displacement amount of the movable body.

According to the present invention, a valve opening sensor for detecting a displacement of a movable portion of a pressure adjusting valve of a pressure regulator and generating an electric signal including information on the opening of the valve, and the valve opening sensor. PWM that controls the drive current of the pump motor to keep the output of the pump at the target value
You may make it provide a control part.

As described above, the fuel flow sensor for outputting the electric signal containing the information of the flow rate of the fuel returned to the fuel tank through the pressure regulator is provided, and the pump motor is maintained so that the output of the fuel flow sensor is maintained at the target value. The PWM control of the drive current of (1) can keep the flow rate of the surplus fuel returned to the fuel tank through the pressure regulator substantially constant, so that the control pressure of the pressure regulator can be kept substantially constant.
Therefore, the fuel pressure can always be kept substantially constant irrespective of whether the power supply voltage of the fuel pump is high or low, and is not affected by the variation in the performance of the pump motor.

Further, with the above construction, the duty ratio of the drive current of the pump motor becomes small at the time of low speed operation when the fuel injection amount required by the engine is small, so the power consumption in the pump motor is reduced and the magnet power generation is performed. The output of the machine can be used to charge 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.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a hardware configuration of a control device according to the present invention. In FIG. 1, 1 is a pump motor for driving a fuel pump 2 and 3 is a direct current for driving the motor. A battery constituting a power source, 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,
Reference numeral 7 is an ignition circuit for applying a high voltage for ignition to a spark plug attached to a cylinder of an internal combustion engine, 8 is an injector attached to inject fuel into a fuel injection space such as an intake pipe of the internal combustion engine 6, and 9 is It is an injector drive circuit that supplies a drive current to the injector 8 when the CPU generates an injection command pulse. Reference numeral 10 denotes a power supply voltage detection interface circuit for detecting the output voltage of the battery 3 (pump motor power supply voltage) and inputting it to the CPU 4, and 11 denotes a drive current control switch for turning on / off the drive current flowing in the pump motor 1. MOSFET 12 is an FET drive circuit (switch drive circuit) that gives 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, 13 is connected to both ends of the motor 1. A diode, 14 is a fuel tank, 15 is a pressure regulator, and 16 is a fuel flow sensor.

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 attached to an internal combustion engine and generates a pulse signal at a constant rotation angle position of a crankshaft, and a signal generator CP for outputting output pulses of the signal generator.
The U4 is composed of a waveform shaping circuit for converting it into a signal of a waveform that can be recognized, and the output of this signal generator is input to a predetermined input port of the CPU 4. CPU4 also
Outputs of various sensors such as a sensor that detects the opening degree of the throttle valve of the internal combustion engine 6 and a sensor that detects the intake air temperature are input through a signal line 17.

The CPU 4 obtains rotation angle information of the engine from the pulse signal output from the signal generator 5, and calculates the rotation speed of the engine 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 cutoff type circuit. When the ignition signal Vi is given from the CPU 4, the ignition circuit 7 causes a rapid change in the primary current of the ignition coil to ignite it. 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 given, and drives the solenoid coil of the injector 8 while the switch element is on. Apply current.

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 is provided with an injection port opened in a fuel injection space (for example, in an intake pipe) of an 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, and 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 from the inlet 8a into the main body. The portion is provided to the pressure regulator 15 through the outlet 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 its housing 15a, and a diaphragm 15d is provided so as to partition the fuel chamber and the spring chamber, and the diaphragm is a spring. Spring 15e provided in chamber 15c
Is urged toward the fuel chamber. In the fuel chamber, a pressure adjusting valve 1 for opening and closing between an inlet and an outlet of the fuel chamber
5f is provided, the valve is connected to the diaphragm 15d, and the valve is normally biased by the spring 15e and is kept in the closed state. The inlet of the fuel chamber 15b is connected to a pipe 18 having the same pressure as the pressure on the fuel inlet side of the injector 8, and the outlet of the fuel chamber is connected to the fuel tank 14 via a return pipe 19. 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).

The illustrated fuel flow sensor 16 is inserted in the middle of the return pipe 19 or between the return pipe 19 and the outlet of the pressure regulator 15, and the flow rate of the surplus fuel returned to the fuel tank 14 through the pressure regulator 15. The electric signal including the information of is output.

An example of the structure of the fuel flow sensor 16 is shown in FIGS. 2 (A), (B) and FIGS. 3 (A), (B). Fuel flow sensor 16 shown in FIGS. 2 (A) and 2 (B).
Is a connecting pipe which is arranged upstream of the return flow path of the excess fuel flowing from the pressure regulator 15 to the fuel tank 14 and is connected to the outlet of the pressure regulator directly or via a pipe forming a part of the return pipe 19. 16
a hollow sensor body 16a having a1 at one end and a connecting pipe 16a2 at the other end, which is connected to the end on the pressure regulator side of the pipe constituting the return pipe 19 arranged on the downstream side of the return flow path; , A shaft 16b rotatably supported by the main body 16a in a state of being positioned in a bulging portion provided in a part of the sensor main body 16a, and one end fixed to the shaft 16b arranged in the main body 16a. Movable flap 16c
And the movable flap 16c on the connecting pipe 16a1 side (main body 16
It is composed of a spring (not shown) that urges the fuel flowing in a) to the upstream side) and a displacement sensor 16d that is connected to the shaft 16b and detects the rotational displacement of the movable flap 16c. The output line 16e is derived. In the illustrated example, the shaft 16b is led out to the outside in a state where the shaft 16b penetrates the body 16a in a liquid-tight and rotatably manner.
Is connected to the input shaft of a displacement sensor 16d mounted on the side surface of the. The displacement sensor 16d is composed of, for example, a potentiometer, and outputs an electric signal corresponding to the rotational displacement of the movable flap 16c. Displacement amount sensor 1
The output of 6d is input to the CPU 4 through the signal output line 16e.

In the fuel flow sensor 16, the movable flap 16c is pushed by the surplus fuel flowing in the main body 16a and a rotational displacement corresponding to the flow rate is generated. Since the rotational displacement amount of the movable flap 16c is detected by the displacement amount sensor 16d, it is possible to obtain an electric signal including information on the flow rate of the surplus fuel returned to the fuel tank 14 through the sensor 16d.

In the example shown in FIG. 2, a rotatable movable flap is disposed in the fuel flow path that returns to the fuel tank through the pressure regulator, and the rotational displacement of the movable flap is detected. However, this fuel flow sensor is installed in a flow path of fuel returning to the fuel tank through a pressure regulator in a state of being biased in a direction against the flow of fuel, and is displaced in accordance with the flow rate of fuel in the flow path. It suffices that the movable body is provided with a displacement amount sensor that generates an electric signal corresponding to the displacement amount of the movable body, and the movable body does not necessarily have a rotational displacement like the movable flap shown in the example of FIG. It does not have to be one that does. For example, a movable body that can be linearly displaced in the flow direction of the excess fuel may be arranged in the return flow path of the surplus fuel, and the movable body may be biased to the upstream side of the return flow path by a spring.

The fuel flow sensor 16 shown in FIGS. 3A and 3B has a sensor body 16A having connection pipes 16A1 and 16A2 at one end and the other end, respectively, and a resistance heating element inserted in the sensor body. 16B and. Both ends of the resistance heating element 16B are connected to and supported by the central conductors of the insulating bushings 16C and 16D mounted in a liquid-tight manner through the main body 16A, and the central conductors of both bushings generate heat via lead wires 16E and 16F. It is connected to a detection unit (not shown) that detects a change in the resistance value of the body 16B. As the resistance heating element 16B, it is possible to use a resistance heating element that changes its resistance value by generating heat when energized, for example, a temperature sensitive resistor having a positive or negative temperature coefficient. The detection unit that detects a change in the resistance value of the heating element can be configured by, for example, a resistance bridge circuit having the heating element on one side.

The fuel flow sensor shown in FIG. 3 has one of its connecting pipes 16A1 and 16A2 positioned upstream of the flow of excess fuel flowing to the fuel tank through the pressure regulator and the other positioned downstream thereof. Insert it in the middle of the return path for excess fuel. Then, by causing a constant current to flow through the heating element 16B, the heating element 16B is caused to generate heat, and a change in the resistance value of the heating element is detected. Heating element 16B
Is cooled by contacting with the fuel flowing in the main body 16A, the temperature of the heating element decreases as the flow rate of the surplus fuel flowing in the main body 16A increases. Therefore, the heating element 16
By detecting the change in the resistance value of B, it is possible to obtain a signal including information on the flow rate of the surplus fuel returned to the fuel tank 14 through the pressure regulator 15.

Since there is usually no oxygen in the flow path of the excess fuel, there is no danger of igniting the fuel due to the heat of the heating element 16B, but it is dangerous if air bubbles are mixed in the excess fuel. The current flowing through the heating element 16B is
It is preferable to set the temperature of B to a value small enough to limit it to a value lower than the ignition temperature of the fuel.

The CPU 4 receives the output signal of the fuel flow sensor 16 (a signal containing information on the flow rate of the surplus fuel returned to the fuel tank through the pressure regulator) as an input and maintains the signal at a target value (the surplus fuel flow rate The duty ratio of the drive current required to flow to the pump motor 1 in order to maintain the set value) is calculated, and the drive command signal Vd which is intermittent at the duty ratio is given to the FET drive circuit 12.

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 between a gate source of the FET 11 through a DC power supply circuit (not shown) through the switch means. A drive signal Vg which is intermittently applied with the same duty ratio as the above is given.

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 unit that controls the injection position (injection timing) and injection time of 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 unit 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 of FIG. 1, when the switch SW is turned on, a power supply voltage (not shown) is applied to the CPU 4 to start up 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.

FIG. 5 shows the response of the fuel pump when the drive command signal Vd having a duty ratio of 100% is applied from the CPU 4 to the injector drive circuit 9 at time t1. 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 of the pump motor 1 is as shown in FIG. 6, for example, and the discharge amount Q from the fuel pump 2 changes greatly with the change of the applied voltage Vp.

When the pressure difference (fuel pressure) between the fuel pressure applied from the fuel pump 2 to the injector 8 and the pressure in the fuel injection space of the internal combustion engine exceeds a set value, the pressure regulating valve 15f of the pressure regulator 15 opens. Excess fuel is returned to the fuel tank 14 through the return pipe 19,
The fuel pressure applied to the injector 8 is maintained at the set value.

When an operation for starting the internal combustion engine is performed and the crankshaft of the engine is rotated, the signal generator 5 generates a pulse signal at a predetermined rotation 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-mentioned apparatus, 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 the excess fuel returned to the fuel tank 14 through the pressure regulator 15 (return flow rate) is Qr. Then, the following 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. 7, even when the engine rotation speed N increases uniformly with the passage of time t, the accelerator pedal (or accelerator grip) is abruptly displaced toward the acceleration side during that time. 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 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 that returns to No. 4 also changes significantly with the change in the control conditions, but in order to maintain good controllability of the pressure regulator, the flow rate Qr of the surplus fuel
It is necessary to keep r within the proper range.

FIG. 9 shows an example of the relationship between the flow rate Qr of the surplus fuel returned to the fuel tank 14 through the pressure regulator 15 and the control pressure (fuel pressure set value) P of the pressure regulator 15. In this example, in order to keep the control pressure P substantially constant, it is necessary to keep the flow rate Qr of the surplus fuel 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 properly controlled. Can not be.

Conventionally, considering the variation of the performance of the pump motor 1 and the variation range of the fuel injection amount at each rotation speed (FIG. 8), even when the required injection amount Qi becomes maximum at each rotation speed, A pump motor that sets the discharge amount Q of the fuel pump so that the return flow rate Qr can flow in a predetermined range and has an output required to obtain the predetermined discharge amount Q even when the power supply voltage is lower than the regulation Select 1,
The pump motor was driven by a DC power supply.

However, in the case of such a configuration, the feedback flow rate Qr of the surplus fuel is the upper limit value Q when the power supply voltage is high.
The controllability of the pressure regulator deteriorated when r2 was exceeded, and the fuel pressure sometimes exceeded the set value.

Further, when a pump motor which generates 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 feedback 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. is there.

In order to prevent these problems from occurring, in the present invention, a detection signal containing information on the flow rate of the surplus fuel returned to the fuel tank through the pressure regulator is obtained and the detection signal is kept at the target value. Pump motor 1
The PWM control of the drive current of the fuel pump controls the discharge amount from the fuel pump so that the feedback flow rate Qr flowing through the pressure regulator 15 is maintained at a set value set in a range where good controllability of the regulator is ensured. .

When the above control is performed, for example, as shown in FIG.
In the above, the control pressure can be maintained at a constant value Ps by controlling the drive current of the pump motor 1 so that the feedback flow rate Qr is maintained at the set value Qrs. The fuel pressure can always be kept constant regardless of the variation in performance of the fuel injection, and the fuel injection amount can be accurately controlled.

The pump motor 1 is selected so that a sufficient amount of fuel can be discharged from the fuel pump 2 even when the power supply voltage is low. When the above control is performed, the duty ratio of the drive current of the pump motor automatically decreases at low speed of the engine with a small required injection amount, so use a pump motor that has a sufficient output at a low power supply voltage. Also, the power consumption of the pump motor can be reduced, and the output of the magnet generator can be distributed to the charging of the battery. Therefore, even when the low speed operation is continued for a long time like an outboard motor that performs trolling, it is possible to operate the engine without trouble.

In the above example, the process of calculating the duty ratio of the drive current of the pump motor required to keep the output of the fuel flow sensor at the target value by the CPU 4, and F
ET drive circuit 12 (switch drive means) and FET 11
The (drive current control switch) constitutes a PWM control unit for performing PWM control of the drive current of the pump motor so that the magnitude of the output of the fuel flow sensor is maintained at the target value.

In the above example, the fuel flow sensor 1
An electric signal for detecting the feedback flow rate flowing in the pressure regulator 15 is obtained by 6 and the drive current of the pump motor is PWM-controlled so as to keep the magnitude of the electric signal at a target value. A valve opening sensor that detects a displacement of the movable portion of the pressure adjusting valve 15f and generates an electric signal including information about the opening of the valve is provided to maintain the output of the valve opening sensor at a target value. Even if the drive current of the pump motor 1 is PWM-controlled, the same effect as described above can be obtained.

FIG. 4 shows an example of the pressure regulator 15 provided with a valve opening sensor. This regulator 15 has a fuel chamber 15 inside a housing 15a thereof.
b and a spring chamber 15c, a diaphragm 15d is provided so as to partition the fuel chamber and the spring chamber. The diaphragm 15d is urged toward the fuel chamber 15b by a spring 15e provided in the spring chamber 15c. The housing 15a has a fuel chamber 15b.
A fuel introduction pipe 15g forming an inlet of the fuel chamber, a fuel discharge pipe 15h forming an outlet of the fuel chamber, and a joint pipe 15k connecting a pipe for connecting the spring chamber 15c to the fuel injection space of the internal combustion engine. Has been done. Fuel outlet pipe 15
A valve seat 15h1 is provided at one end located in the fuel chamber of h, and the valve seat 15h1 is connected to a movable block 15d1 provided at the center of the diaphragm 15d.
It is opposed to 5i. In this example, the movable valve body 15
i and the valve seat 15h1 at the end of the fuel outlet pipe 15h constitute a pressure adjusting valve 15f, and when the pressure difference between the pressure in the fuel chamber 15b and the pressure in the spring chamber 15c is less than the set value, the spring The movable valve body 1 by the urging force of 15e
5i is in contact with the valve seat 15h1 and the valve 15f is held in the closed state. The spring chamber 15c is hermetically pierced through the opening provided in the end wall of the housing 15a.
A valve opening sensor 15j is inserted therein, and an input portion 15j1 of the valve opening sensor 15j is connected to a central portion of the diaphragm 15d (a position corresponding to the movable portion of the pressure adjusting valve 15f).

The valve opening sensor 15j is composed of a displacement sensor such as a potentiometer and has a diaphragm 1
An electric signal having a magnitude corresponding to the displacement amount of 5d is output.
Since the displacement amount of the central portion of the diaphragm 15d corresponds to the displacement amount of the movable portion (movable valve body 15i) of the pressure adjusting valve 15f, the output signal obtained from the valve opening sensor 15j is the opening signal of the pressure adjusting valve. It becomes a signal containing the degree information. This signal is also a signal containing information on the flow rate of fuel returning to the fuel tank through the pressure regulator.

When the valve opening sensor as described above is provided, the output signal of the valve opening sensor is sent to the CPU 4
Is input to The CPU 4 uses the pump motor 1 to keep the magnitude of the output signal of the valve opening sensor 15j at the target value.
Calculate the duty ratio of the drive current that needs to flow to
The drive command signal Vd which is intermittent at the calculated duty ratio is F
It is given to the ET control circuit 12. The FET control circuit 12 gives a drive signal Vg which is intermittent at the same duty ratio as the drive command signal Vd to the FET 11 to turn on / off the FET.
As a result, the discharge amount from the fuel pump is controlled so that the feedback flow rate Qr flowing through the pressure regulator 15 is maintained at a set value set in a range where good controllability of the regulator is ensured.

In this case, the process of calculating the duty ratio of the drive current of the pump motor required to keep the output of the valve opening sensor at the target value by the CPU 4, the FET drive circuit 12 (switch drive means), The FET 11 (driving current control switch) constitutes a PWM control unit that PWM-controls the driving current of the pump motor so as to keep the output of the valve opening sensor at a target value.

The drive current control switch is not limited to the FET 11 as long as it can turn on / off the drive current supplied from the DC power supply to the pump motor. Other switch elements such as transistors may be used as the drive current control switch.

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 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. 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.

In the above description, the microcomputer is used to calculate the duty ratio of the drive current of the pump motor, and a drive signal intermittently applied at the calculated duty ratio is applied to the drive current control switch to drive the pump motor. Although the current is PWM controlled, the deviation between the output signal of the fuel flow sensor and its target value or the deviation between the output signal of the valve opening sensor and its target value is detected and these deviations are made zero. The PWM control unit may be configured to perform feedback control so that

In the example shown in FIG. 1, the fuel flow sensor 16 is provided between the pressure regulator 15 and the fuel tank 14. This fuel flow sensor provides information on the flow rate of the fuel returned to the fuel tank through the pressure regulator. The fuel flow sensor 16 may be provided in the fuel flow path between the injector 8 and the pressure regulator 15 as long as the signal including the signal is generated.

[0078]

As described above, according to the present invention, a detection signal containing information on the flow rate of the fuel returned to the fuel tank through the pressure regulator is obtained, and the pump motor of the pump motor is maintained so as to maintain the detection signal at the target value. The drive current is PWM controlled, or a detection signal including information on the opening of a pressure adjusting valve provided in the pressure regulator is obtained, and the drive current of the pump motor is set to P so as to maintain the detection signal at a target value.
Since the WM control is performed, regardless of the level of the power supply voltage of the pump motor and the variation in the performance of the pump motor,
There is an advantage that the control pressure of the pressure regulator can be kept constant, the fuel pressure can be kept constant at all times, and the fuel injection amount can be accurately controlled.

Further, according to the present invention, the duty ratio of the drive current of the pump motor can be reduced at the time of low speed operation when the fuel injection amount required by the engine is small, so that the power consumption of the pump motor can be reduced. The output of the magneto generator can be distributed to the charging of 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. 2A is a front view showing a configuration example of a fuel flow sensor used when implementing the present invention. (B)
FIG. 3A is a cross-sectional view of a part of (A).

FIG. 3 (A) is a front view showing a partial cross-section of another configuration example of the fuel flow sensor used when implementing the present invention. (B) is a cross-sectional view of (A).

FIG. 4 is a cross-sectional view showing a configuration example of a pressure regulator including a valve opening sensor used when implementing the present invention.

FIG. 5 is a diagram showing a response of a fuel pump when a power supply voltage is applied to a pump motor.

FIG. 6 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. 7 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. 8 is a graph showing the relationship between the engine speed and the injection amount required by the engine.

FIG. 9 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 drive current control switch 14 Fuel tank 15 Pressure regulator 15j Valve opening sensor 16 Fuel flow sensor

Claims (4)

[Claims] 1. An injector for injecting fuel into a fuel injection space of an internal combustion engine, a fuel pump for supplying fuel to the injector by being driven by a pump motor supplied with a drive current from a DC power source, and the fuel pump to the injector. A pressure adjusting valve that opens when the pressure difference between the supplied fuel pressure and the pressure in the fuel injection space or the atmospheric pressure exceeds a set value is provided, and a portion of the fuel supplied from the fuel pump to the injector is The pressure of the fuel supplied from the fuel pump of the fuel injection device for an internal combustion engine to the injector, which is provided with a pressure regulator for controlling the differential pressure to return to a set value by returning to the fuel tank side through a pressure adjusting valve. A fuel pressure control device for a fuel injection device, the fuel pressure control device comprising: A fuel flow sensor that outputs an electrical signal containing information on the flow rate of fuel to be returned, and an output of the fuel flow sensor as an input, and PWM control of the drive current of the pump motor to maintain the output of the sensor at a target value. A fuel pressure control device for a fuel injection device, comprising: a PWM control unit. 2. The fuel flow sensor includes a resistance heating element inserted into a flow path of fuel that returns to the fuel tank through the pressure regulator, and a detection unit that detects a change in resistance value of the resistance heating element. The fuel pressure control device for a fuel injection device according to claim 1, wherein the fuel pressure control device is provided. 3. The fuel flow sensor is provided in a flow path of fuel returning to a fuel tank through the pressure regulator in a state of being biased in a direction against the flow of the fuel, and the fuel in the flow path is provided. 2. The fuel for a fuel injection device according to claim 1, further comprising a movable body that produces a displacement corresponding to the flow rate of the fuel and a displacement amount sensor that produces an electric signal corresponding to the displacement of the movable body. Pressure control device. 4. An injector for injecting 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 the fuel pump for injection into the injector. A pressure adjusting valve that opens when the pressure difference between the supplied fuel pressure and the pressure in the fuel injection space or the atmospheric pressure exceeds a set value is provided, and a portion of the fuel supplied from the fuel pump to the injector is The pressure of the fuel supplied from the fuel pump of the fuel injection device for an internal combustion engine to the injector, which is provided with a pressure regulator for controlling the differential pressure to return to a set value by returning to the fuel tank side through a pressure adjusting valve. A fuel pressure control device for a fuel injection device, the pressure regulating valve of the pressure regulator A valve opening sensor that detects a displacement of a movable part and generates an electric signal including information about the opening of the valve, and a PWM drive current for the pump motor so as to maintain an output of the valve opening sensor at a target value. A fuel pressure control device for a fuel injection device, comprising: a PWM control unit for controlling.