JP2000297716A - Fuel pump control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly control the fuel discharge quantity of a fuel pump against the requirement of an engine and to reduce the power loss in a control device by feeding back the applied voltage to a pump motor to a driving means via an integrating means, comparing it with a reference signal, and controlling the drive of the pump motor. SOLUTION: An integrating circuit 42 is connected to one end of a fuel pump driving DC motor 4, and the both-end voltage of the DC motor 4 is applied to the integrating circuit 42. The output signal Vi of the integrating circuit 42 is applied to an error signal generating circuit 43 made of a differential amplifier to obtain an error signal Ve corresponding to the level difference from a reference signal Vr. The error signal Ve is compared with the chopping wave signal from a chopping wave generating circuit 46 by a comparator 45 to generate a signal indicating a high level or a low level. This signal is inverted by two NOT circuits 47, 48 and applied to FETs 37, 38. When the FET 37 is turned on, the DC motor 4 is excited from the positive terminal of a battery 40 and is relatively driven.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel pump control device for pumping fuel in a fuel tank to a fuel supply device such as an injector or a carburetor in an internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine, a fuel pump is provided to pressurize and supply fuel in a fuel tank to an injector. As shown in FIG. 1, a suction port 3a and a discharge port 3b are formed in a casing 3 of the fuel pump 1, and a pump motor 4 which is a DC motor and a pump body 5 which is rotationally driven by the motor 4 are formed in the casing 3. And are provided. A fuel inlet pipe 6 extending into the fuel tank 2 is connected to the inlet 3a, and a fuel outlet pipe 7 is connected to the outlet 3b. When the pump body 5 operates, the fuel in the fuel tank 2 is supplied to the fuel suction pipe 6 and the suction port 3 by the rotational force of a turbine (not shown) of the pump body 5.
The fuel is sucked into the casing 3 through the outlet port a, and further sent out to the fuel discharge pipe 7 through the casing 3 and the discharge port 3b.

[0003] The fuel discharge pipe 7 has a filter 10
The injector 11 is connected via the. The injector 11 injects the fuel delivered through the fuel discharge pipe 7 near an intake port of an engine (not shown). Also,
A pressure regulator 12 for adjusting the fuel pressure in the fuel discharge pipe 7 to a predetermined pressure is connected to the fuel discharge pipe 7. The pressure regulator 12 adjusts the fuel pressure in the fuel discharge pipe 7 by flowing a part of the fuel in the fuel discharge pipe 7 to the fuel pipe 13. The fuel in the fuel pipe 13 is returned to the fuel tank 2.

As a conventional configuration of a control device for controlling the driving of the fuel pump 1, there is a mere on / off control using two relays 21 and 22 as shown in FIG. Each of the relays 21 and 22 is a relay switch 21a, 2
2a and relay coils 21b and 22b, and two relay switches 21a and 22
a is connected in series to one end of the motor 4, and the negative terminal of the battery 23 is grounded together with the other end of the motor 4. One end of each of the relay coils 21b and 22b is connected to a positive terminal of the battery 23, and the other end is connected to the ECU 24. A voltage drop resistor 25 is connected between both terminals of the relay switch 22a.

[0005] In this control device, the ECU 24 controls to switch the motor drive between two stages of a high consumption mode and a low consumption mode according to the engine speed and the fuel injection amount.
When driving the fuel pump 1 in the high consumption mode, EC
U24 makes the other end of each of the relay coils 21b and 22b equal to the ground potential to thereby set the relay coils 21b and 22b.
22b are excited together. This makes relay switch 2
Since both 1a and 22a are turned on, the output voltage of the battery 23 is directly applied to the motor 4, and the relay switch 21 is connected to the positive terminal of the battery 23.
A current flows to the motor 4 through the motors a and 22a. When driving the fuel pump 1 in the low consumption mode, the ECU 24 excites only the relay coil 21b by making the other end of the relay coil 21b equal to the ground potential. As a result, the relay switch 21a is turned on, so that the output voltage of the battery 23 is applied to the motor 4 via the resistor 25. Since the current flowing through the motor 4 in the low consumption mode is lower than in the high consumption mode, the amount of fuel supplied to the injector 11 by the fuel pump 1 per unit time is reduced, so that an excessive amount of fuel is not supplied. I have to.

FIG. 3 shows another conventional control device of the fuel pump. The conventional control device shown in FIG. 3 is a device for feedback-controlling the level of the current flowing through the motor 31 of the fuel pump. In this control device, one end of a motor 31 is connected to a positive terminal of a battery 32, and the other end of the motor 31 is grounded via a switch element 33 and a resistor 34 in this order. A flywheel diode 36 is connected to the motor 31 in parallel. The resistor 34 is for detecting a current flowing through the motor 31, and the voltage across the resistor 34 is supplied to the ECU 35 as an actual current value. The ECU 35 sets a target current value according to the engine speed and the fuel injection amount, compares the target current value with the actual current value, sets a duty ratio according to the comparison result, and sets a drive pulse of the duty ratio. The signal is supplied to the switch element 33. The switch element 33 repeatedly turns on and off according to the drive pulse signal, whereby the current flowing through the motor 31 is controlled to the target current value. Therefore, according to this control device, an appropriate amount of fuel is supplied to the injector according to the operating state of the engine.

[0007]

However, in the case of the control device shown in FIG. 2, the amount of fuel discharged from the fuel pump is roughly adjusted in two stages, so that the amount of fuel discharged from the fuel pump is controlled by the operating state of the engine. However, since the amount of fuel is not appropriate for the required amount depending on the amount of fuel supplied to the injector, power is wasted. Further, since the voltage applied to the pump motor 4 is reduced by using the voltage drop resistor 25 in order to adjust the fuel discharge amount of the fuel pump, the power loss of the battery due to the voltage drop resistor 25 occurs. There was a problem that there is. Furthermore, because of the open-loop control, the fluctuation of the output voltage of the battery 23 changes the fuel discharge amount of the fuel pump, and there is a problem that a desired fuel discharge amount cannot always be obtained.

In the case of the control device shown in FIG. 3, a resistor 34 for detecting a current flowing through the pump motor 31 for feedback control is provided. However, since the resistor 34 is connected in series with the motor 31, In addition, there is a problem that the power loss of the battery due to the resistor 34 occurs.
Therefore, an object of the present invention is to provide a fuel pump control device capable of appropriately controlling the fuel discharge amount of a fuel pump and reducing the power loss of a power supply.

[0009]

SUMMARY OF THE INVENTION A fuel pump control device according to the present invention is a fuel pump control device for driving and controlling a pump motor in a fuel pump for feeding fuel in a fuel tank of an internal combustion engine to a fuel supply device. Connecting a first switch element connected in series with the pump motor between the positive and negative terminals of the DC power supply, a second switch element for a flywheel connected in parallel with the pump motor, and a first switch element of the pump motor Integrating means for integrating the voltage of the terminal; reference signal generating means for generating a reference signal; and driving the first switch element on and off in accordance with the level difference between the output signal of the integration means and the reference signal. And a driving means for driving the second switch element on / off in a phase opposite to the on / off state.

According to the structure of the present invention, the voltage applied to the pump motor is fed back to the driving means via the integrating means, and the voltage is compared with a reference signal to drive the pump motor. The discharge amount can be appropriately controlled according to the required amount of the engine. Further, since the voltage applied to the pump motor is fed back to the driving means via the integrating means, the output voltage of the DC power supply can be applied to the pump motor without passing through the current detecting resistor and the voltage dropping resistor. Therefore, power loss in the control device can be reduced.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 4 shows a control device for a fuel pump according to the present invention. This control device is assumed to be applied to the fuel pump 1 of FIG. In this control device, two MOSFETs (Metal Oxi
deSemiconductor Field Effect Transistor) 37, 38
Is provided. The FET 37 corresponding to the first switch element is a P-channel FET, and is provided as a switch element for turning on and off the level of the current flowing through the DC motor 4 of the fuel pump 1 to control the duty ratio. FET3 corresponding to the above second switch element
Reference numeral 8 denotes an N-channel FET, which is provided as a flywheel switch element for flowing a current caused by electromagnetic energy accumulated in the DC motor 4 when the FET 37 is turned off.

The source of the FET 37 is connected via a relay switch 39a of a relay 39 to a battery 40 which is a DC power supply.
, And the drain is connected to one end of the motor 4 together with the source of the FET 38. The source of the FET 38 is grounded together with the other end of the motor 4. The excitation of the relay coil 39b of the relay 39 is controlled by an ECU (engine control unit). Note that the other end of the battery 40 is grounded.

An integrating circuit 42 is connected to one end of the DC motor 4 of the fuel pump 1. Since the other end of the DC motor 4 is grounded, the voltage at both ends of the DC motor 4 is supplied to the integration circuit 42. The output of the integration circuit 42 is connected to an error signal generation circuit 43 composed of a differential amplifier. The error signal generation circuit 43 generates an error signal Ve corresponding to the level difference between the output signal Vi of the integration circuit 42 and the reference signal Vr. The reference signal Vr has a level corresponding to a desired current value to flow through the motor 4 and is generated by the reference signal generation circuit 44. The reference signal generation circuit 44 is EC
An analog reference signal Vr is generated based on a digital command value indicating a desired current value from U41. ECU 41
In, an instruction value is set according to the engine speed and the fuel injection amount. The engine speed is detected by a crank angle sensor (not shown). The fuel injection amount is, for example, an engine speed, an air flow meter (not shown)
Is set based on the intake air amount detected by the control unit.

A comparator 45 is connected to the output of the error signal generation circuit 43. The comparator 45 compares the error signal supplied from the error signal generation circuit 43 with the triangular wave signal, and generates a signal indicating a high level or a low level indicating the comparison result. The triangular wave signal is a signal having a constant period, as shown in FIG.

The output of the comparator 45 has two NOT circuits 4
7, 48 are connected. The NOT circuit 47 is a comparator 4
The level of the output signal of the comparator 5 is inverted and supplied to the gate of the FET 37, and the NOT circuit 48 inverts the level of the output signal of the comparator 45 and supplied to the gate of the FET 38. The error signal generation circuit 43, the comparator 45, and the triangular wave generation circuit 4
6 and NOT circuits 47 and 48 form driving means.

In this control device, the output voltage Vb of the battery 40 is further compared with a predetermined voltage Va (for example, 12 V) by the comparator 49. The predetermined voltage Va is a stabilized voltage. The output of the comparator 49 is supplied to the ECU 41. Also, FE
A relay switch (mechanical switch) 50a of the relay 50 is connected between the source and the drain of T37. A switching element 51 such as a transistor is connected between the gate of the FET 38 and the ground. Relay 50
The control terminals of the relay coil 50b and the switch element 51 are connected to the ECU 41. The ECU 41 is a comparator 49
To excite the relay coil 50b according to the output level of
At the same time, the switch element 51 is turned on. When the relay coil 50b is excited, the relay switch 50a is turned on.

Next, the operation of the control device having such a configuration will be described with reference to the waveform diagram of FIG. First, battery 4
The output voltage Vb of 0 is equal to or higher than the predetermined voltage Va, and the relay switch 50a and the switch element 51 are turned off. When the ECU 41 excites the relay coil 39b to drive and control the fuel pump 1, the relay switch 39a is turned on, and the potential of the positive terminal of the battery 40 is applied to the source of the FET 37. Further, a reference signal Vr having a level corresponding to the instruction value from the ECU 41 is supplied to a reference signal
Generated from. When the relay switch 39a is turned on, the output voltage Vi of the integration circuit 42 is sufficiently lower than the level of the reference signal Vr, as shown in FIG.
Error signal Ve output from error signal generation circuit 43
Is the lowest as shown in FIG. 5 (b). When the error signal Ve is compared with the triangular wave signal from the triangular wave generation circuit 46 in the comparator 45, the level of the triangular wave signal is higher than the error signal Ve, and the output level of the comparator 45 is as shown in FIG. As shown in c), the output level of the comparator 45 becomes high, and the duty ratio during the high level period of the output signal of the comparator 45 becomes almost 100%. When the high level output is inverted by the NOT circuit 47 and supplied to the gate of the FET 37 as a low level, the FET 37 is turned on.
When the high level output of the comparator 45 is inverted by the NOT circuit 48 and supplied to the gate of the FET 38 as a low level, the FET 38 is turned off.

When the level of the triangular wave signal is lower than the error signal Ve, the output level of the comparator 45 becomes low,
When this low level output is inverted by the NOT circuit 47 and supplied to the gate of the FET 37 as a high level,
The ET 37 is turned off. When the low level output of the comparator 45 is inverted by the NOT circuit 48 and supplied to the gate of the FET 38 as a high level, the FET 38 is turned on.

When the FET 37 is turned on, a current flows from the positive terminal of the battery 40 to the relay switch 39a, between the source and drain of the FET 37, and to the ground via the motor 4, and a voltage is applied to the motor 4, so that the motor 4 rotates. Driven. Since the applied voltage to the motor 4 is integrated by the integrating circuit 42, the integrated applied voltage, that is, the integrated voltage Vi is supplied to the error signal generating circuit 43.

When the integrated voltage Vi rises to the positive voltage side, the level of the error signal Ve also rises as shown in FIG. The rising error signal Ve is supplied to the comparator 45.
When compared with the triangular wave signal, the periodic high-level output period of the comparator 45 becomes shorter as shown in FIG. 5C, so that the duty ratio becomes smaller. As a result, the on-period of the FET 37 per unit time is shortened, so that the average current value flowing through the motor 4 decreases, and as a result, the integrated voltage Vi decreases to the negative voltage side.

On the other hand, when the integrated voltage Vi drops to the negative voltage side, the level of the error signal Ve also drops as shown in FIG. When the error signal Ve whose level falls is compared with the triangular wave signal by the comparator 45, the periodic high-level output period of the comparator 45 becomes longer as shown in FIG. Become. As a result, the on-period of the FET 37 per unit time becomes longer, so that the average current value flowing through the motor 4 increases, and as a result, the integral voltage Vi increases to the positive voltage side. Thus, the integrated voltage Vi of the voltage applied to the motor 4 is equal to the reference signal Vr.
The duty ratio of the ON / OFF of the FET 37, that is, the driving of the motor 4 is controlled so as to be equal to the level of
The average current value of the motor 4 is substantially equal to the current value corresponding to the value specified by the ECU 41.

When FET 37 is off, FET 3
8 is turned on, and the current due to the electromagnetic energy stored in the DC motor 4, that is, the current due to the so-called back electromotive force is applied to the FET.
38 is commutated between the source and the drain. Further, in such a control device, the output voltage Vb of the battery 40 is constantly compared with the predetermined voltage Va by the comparator 49. When the output voltage Vb of the battery 40 falls below the predetermined voltage Va, the comparator 49 becomes high level. Is generated and supplied to the ECU 41. The ECU 41 responds to the switching signal by
Current is supplied to the relay coil 50b of the relay coil 5b.
0b is excited and the switch element 51 is turned on. The excitation of the relay coil 50b causes the relay switch 5
0a is turned on, and the current flows from the positive terminal of the battery 40 to the relay switch 39 regardless of the on / off state of the FET 37.
a, the relay switch 50a, and the ground through the motor 4, and the output voltage Vb of the battery 40 is applied to the motor 4.
Is applied as it is. That is, when the output voltage Vb of the battery 40 falls below the predetermined voltage Va, the power of the battery 40 is supplied to the motor 4 without being lost by the ON resistance of the FET 37. When the switch element 51 is turned on, the gate of the FET 38 is forcibly set to the ground potential, so that the FET 38 is turned off.

In the above embodiment, a P-channel MOSFET 37 is used as the first switch element, and an N-channel MOSFET is used as the second switch element.
Although the ET38 is used, the present invention is not limited to this, and another on / off switch element can be used.
However, when the MOSFET is used as in the embodiment, the on-resistance is smaller than that of a switch element such as another PNP type or NPN type transistor, so that the power loss due to the switch element can be reduced. That is, since the FET which is a low-loss element as described above is used instead of the diode as the commutation element, the loss in the commutation circuit can be reduced.

[0024]

As described above, according to the present invention, the voltage applied to the pump motor is fed back to the driving means via the integrating means and compared with the reference signal to drive the pump motor. In addition, the amount of fuel discharged from the fuel pump can be appropriately controlled in accordance with the required amount of the engine. Further, since the voltage applied to the pump motor is fed back to the driving means via the integrating means, the output voltage of the DC power supply can be applied to the pump motor without passing through the current detecting resistor and the voltage dropping resistor. Therefore, power loss in the control device can be reduced. As a result, the size of the heat sink can be reduced, and the weight of the device can be reduced. Further, since there is no need to provide the current detecting resistor used in the conventional device, the circuit configuration in the control device can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a fuel injection device for an internal combustion engine including a fuel pump.

FIG. 2 is a schematic diagram showing a conventional fuel pump control device.

FIG. 3 is a schematic diagram showing a conventional fuel pump control device.

FIG. 4 is a diagram showing an embodiment of the present invention.

FIG. 5 is a waveform chart showing an operation state of each unit of the apparatus of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel pump 2 Fuel tank 3 Casing 4 Pump motor 5 Pump body 10 Filter 11 Injector 12 Pressure regulator 24, 35, 41 ECU 37, 38 FET

Claims (3)

[Claims] 1. A fuel pump control device for driving and controlling a pump motor in a fuel pump for pumping fuel in a fuel tank of an internal combustion engine to a fuel supply device, wherein the pump motor is connected in series with the pump motor between positive and negative terminals of a DC power supply A first switch element connected to the pump motor; a second switch element for a flywheel connected in parallel with the pump motor; and an integrating means for integrating a voltage of a connection terminal of the pump motor with the first switch element. A reference signal generating means for generating a reference signal; and an on / off drive of the first switch element according to a level difference between an output signal of the integration means and a reference signal, in a phase opposite to the on / off state of the first switch element. And a drive unit for driving the second switch element on and off. 2. The fuel pump control device according to claim 1, wherein the first switch element and the second switch element include MOSFETs having different channels. 3. A mechanical switch connected in parallel to the first switch element, a comparing means for generating a switching signal when an output voltage of the DC power supply falls below a predetermined voltage, and a response to the switching signal. 2. The relay control device according to claim 1, further comprising: relay control means for turning on the mechanical switch by turning on the mechanical switch; and off-control means for forcibly turning off the second switch element in response to the switching signal. Fuel pump control unit.