Drive unit for driving fuel pump for small-sized vehicle

Abstract: A drive unit for driving a fuel pump (4) for a small-sized vehicle is provided, which is capable of reducing a current consumption of the fuel pump (4). A drive unit for driving a fuel pump (4) for a small-sized vehicle, includes an ECU (9) for controlling a fuel injection amount of a fuel injector (6). The ECU (9) drives the fuel pump (4) on the basis of control data for controlling the fuel injection amount of the fuel injector (6) and of a power supply voltage of the fuel pump (4). For example, the fuel pump (4) is driven under pulse-width modulation (PWM) in such a manner that a pulse-width of a PWM signal is made larger with an increase in fuel injection amount of the fuel injector (6) and is made smaller with a decrease in fuel injection amount of the fuel injector 6.

Description: The present invention relates to a drive unit for driving a fuel pump for a small-sized vehicle using an electronic control unit (ECU). A conceptual view of a drive unit for driving a fuel pump for a motorcycle is shown in Fig. 6. Referring to Fig. 6, gasoline is fed from a fuel tank 2 into a fuel pump 4 through a filter 3, being pressurized in the fuel pump 4, and is fed into a fuel injector 6 through a filter 5. A fuel presssure in an intake manifold 7 is kept constant by a pressure regulator 8, and gasoline is fed into the fuel tank 2 through the pressure regulator 8, thus gasoline circulates. A piston 21 is reciprocated along with combustion of gasoline, to rotate a crank (not shown). A power supply voltage is supplied from an on-vehicle battery 10 to the fuel pump 4. A fuel injection amount of the fuel injector 6 is controlled by an ECU (Electronic Control Unit) 9. DE4443879A1 discloses a drive unit according to the preamble of claim 1. There, the control signal for the fuel pump is divided by the power supply voltage. EP0055417A1 and US4554634 disclose to correct the fuel injection amount by the battery power supply voltage without giving specific algorithms for this process. In the case where a total current consumption of an electric system is large as in a four-wheeled vehicle, a ratio of a current consumption of a fuel pump to the total current consumption of the electric system becomes small. Meanwhile, in the case where a total current consumption of an electric system is small as in a motorcycle, a ratio of a current consumption of a fuel pump to the total current consumption of the electric system becomes large. Therefore, it is an object of the invention to provide a drive unit for driving a fuel pump for a motorcycle, which is capable of reducing a current consumption of a fuel pump. It is a further object of the invention to provide a drive unit for driving a fuel pump for a motorcycle, which prevents an injection amount of a fuel injector from being excessively varied depending on a change in a power supply voltage of the fuel pump. To achieve at least the first object, according to an invention described in claim 1, there is provided a drive unit for driving a fuel pump for a small-sized vehicle, comprising: an electronic control unit for controlling a fuel injection amount of a fuel injector; wherein said electronic control unit drives said fuel pump on the basis of control data for controlling a fuel injection amount of said fuel injector and of a power supply voltage applied to said fuel pump and wherein said power supply voltage is taken into consideration in form of a correction term Pv depending on said power supply voltage, when a control signal for said fuel pump is calculated by said electronic control unit characterized in that a duty factor D of said control signal is calculated in accordance with the following equation: D = A + Ti x Ne x K + Pv, wherein A is a minimum duty factor, Ti is a fuel injection amount, Ne is an engine speed, K is a correction coefficient, and Pv is an additive correction term. Since the drive of the fuel pump is controlled on the basis of control data of an injection amount of the fuel injector and of a power supply voltage of the fuel pump, the drive of the fuel pump can be controlled such that a drive power of the fuel pump is reduced in the case where the fuel injection amount is small. The drive of the fuel pump can be also controlled such that the fuel injection amount (or injection pressure) is prevented from becoming deficient depending on a substantial change in power supply voltage of the fuel pump. Preferably, the electronic control unit drives said fuel pump under pulse-width modulation (PWM) using a PWM signal on the basis of control data for controlling a fuel injection amount of said fuel injector and of a power supply voltage applied to said fuel pump in such a manner that a pulse-width of the PWM signal is made larger with an increase in fuel injection amount of said fuel injector and is made smaller with a decrease in fuel injection amount of said fuel injector. Since the drive of the fuel pump is controlled on the basis of control data of an injection amount of the fuel injector and of a power supply voltage of the fuel pump, the drive of the fuel pump can be controlled such that a drive power of the fuel pump is reduced in the case where the fuel injection amount is small. The drive of the fuel pump can be also controlled such that the fuel injection amount (or injection pressure) is prevented from becoming deficient depending on a change in power supply voltage of the fuel pump. For example, the drive unit is configured that a pulse-width of a PWM signal is made larger with an increase in fuel injection amount of the fuel injector so that the fuel pump can be driven at the maximum flow rate when the pulse-width is maximized; and further, the pulse-width of the PWM signal is made smaller with a decrease in fuel injection amount of the fuel injector so that a power consumption of the fuel pump can be reduced when the fuel injection amount is small. Preferably, said electronic control unit drives said fuel pump under pulse-width modulation (PWM) using a PWM signal on the basis of control data for controlling a fuel injection amount of said fuel injector and of a power supply voltage applied to said fuel pump in such a manner that when the power supply voltage of said fuel pump is larger than a rating voltage, a pulse-width of the PWM signal is made smaller than that in the case where the power supply voltage is equal to the rating voltage; and when the power supply voltage of said fuel pump is smaller than the rating voltage, the pulse-width of the PWM signal is made larger than that in the case where the power supply voltage is equal to the rating voltage. Since the drive of the fuel pump is controlled on the basis of control data of an injection amount of the fuel injector and of a power supply voltage of the fuel pump, the drive of the fuel pump can be controlled such that a drive power of the fuel pump is reduced in the case where the fuel injection amount is small. The drive of the fuel pump can be also controlled such that the fuel injection amount (or injection pressure) is prevented from becoming deficient depending on a change in power supply voltage of the fuel pump. For example, when a power supply voltage of the fuel pump is larger than a rating voltage, the drive power of the fuel pump can be lowered and thereby the power consumption thereof can be reduced by making smaller a pulse width of a PWM signal than that in the case where the power supply voltage of the fuel pump is equal to the rating voltage. Similarly, when the power supply voltage of the fuel pump is smaller than the rating voltage, the fuel injection amount (or injection pressure) can be prevented from becoming deficient depending on a change in power supply voltage of the fuel pump by making larger the pulse-width of the PWM signal than that in the case where the power supply voltage of the fuel pump is equal to the rating voltage. Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1: A conceptual diagram showing a drive unit for driving a fuel pump of a small-sized vehicle of the present invention. Fig. 2: A schematic diagram illustrating one method of driving the fuel pump shown in Fig. 1. Fig. 3: A characteristic diagram showing a correction amount of a duty factor depending on a power supply voltage of the fuel pump. Fig. 4: A schematic diagram illustrating one method of driving the fuel pump shown in Fig. 1. Fig. 5: A characteristic diagram showing a power switching signal with respect to a required fuel amount. Fig. 6: A conceptual diagram of a related art drive unit for driving a fuel pump of a motorcycle. Fig. 1 is a conceptual view of a drive unit for driving a fuel pump 4 for a small-sized vehicle according to the present invention. The drive unit for driving a fuel pump 4 for a small-sized vehicle includes a fuel tank 2, filters 3 and 5, a fuel pump 4, a fuel injector 6, a pressure regulator 8, an on-vehicle battery 10, an ECU 9, and a switching means 11. Gasoline is fed from the fuel tank 2 into the fuel pump 4 through the filter 3, being pressurized in the fuel pump 4, and is fed into the fuel injector 6 through the filter 5. A fuel pressure in an intake manifold 7 is kept constant by the pressure regulator 8, and gasoline is fed into the fuel tank 2 through the pressure regulator 8, thus gasoline circulates. A piston 21 is reciprocated along with combustion of gasoline, to rotate a crank (not shown). A power supply voltage is supplied from the on-vehicle battery 10 to the fuel pump 4. A fuel injection amount of the fuel injector 6 is controlled by the ECU-9 integrated with a memory in which various control programs are previously stored. The ECU 9 supplies a PWM (Pulse-Width Modulation) signal into the switching means 11, to drive (a motor in) the fuel pump 4 under pulse-width modulation through the switching means 11. The ECU 9 detects a voltage of the on-vehicle battery 10, thus detecting a power supply voltage of the fuel pump 4. Fig. 2 is a schematic diagram illustrating a method of driving the fuel pump 4 in the fuel injection system shown in Fig. 1. One terminal of the fuel pump 4 is connected to a high potential side of the on-vehicle battery 10. The other terminal of the fuel pump 4 is connected to an input terminal of the switching means 11. A capacitor C is connected in parallel to the fuel pump 4. An output terminal of the switching means 11 is connected to a low potential side of the on-vehicle battery 10. A control terminal T of the switching means 11 is connected to the ECU 9. The switching means 11 is repeatedly turned on/off on the basis of the PWM signal supplied from the ECU 9, to drive the fuel pump 4 under pulse-width'modulation. As the switching means 11, there may be used a field effect transistor or a bipolar transistor. The field effect transistor is preferably represented by an n-channel enhancement type field effect transistor. The bipolar transistor is preferably represented by an npn type transistor. A pulse-width of the PWM signal supplied from the ECU 9 is determined on the basis of a duty factor D. The duty factor D is calculated in accordance with the following equation: D = A + Ti×Ne×K + Pv Here, character A is a minimum duty factor, and Ne is an engine speed (rotational speed, crank rotation speed). Character Ti is a fuel injection amount. The fuel injector 6 is controlled to inject fuel in the fuel injection amount Ti. Character K is a correction coefficient. Character Pv is a correction amount of the duty factor depending on the power supply voltage of the fuel pump 4 (see Fig. 3). The ECU 9 calculates the fuel injection amount Ti in accordance with the following equation: Ti = TiM×Ktw×Kta×Kpa×Kacc Here, character TiM is a basic fuel injection amount. A table (data table) for determining the basic fuel injection amount TiM on the basis of a throttle opening degree and a crank rotational speed is previously stored in the memory integrated with the ECU 9. Character Ktw is a correction coefficient on the basis of a temperature of cooling water for cooling a water-cooled engine of a small-sized vehicle. The small-sized vehicle includes a water temperature sensor, an atmospheric temperature sensor, an atmospheric pressure sensor, a throttle opening degree detecting sensor, and a crank rotational speed sensor. Character Kta is a correction coefficient on the basis of an atmospheric temperature near a throttle inlet port (or throttle valve). Character Kpa is a correction coefficient on the basis of an atmospheric pressure near the throttle inlet port (or throttle valve). Character Kacc is a correction coefficient on the basis of a variation of the throttle opening degree. In this way, the pulse-width (duty factor D) of the PWM signal is made larger with an increase in fuel injection amount Ti×Ne, so that the fuel pump 4 can be driven at the maximum flow rate in the case where the pulse-width is maximized. The pulse-width is made smaller with a decrease in fuel injection amount Ti, so that a current consumption of the fuel pump 4 can be reduced in the case where the fuel injection amount Ti is small. To be more specific, the drive of the fuel pump 4 can be controlled such that a drive power of the fuel pump 4 is reduced when the fuel injection amount Ti is small, by controlling the drive of the fuel pump 4 on the basis of the control data of the fuel injection amount Ti of the fuel injector 6, that is, TiM, Ktw, Kta, Kpa, Kacc, and Ne and of the power supply voltage of the fuel pump 4. Fig. 3 is a characteristic diagram showing characteristics of the correction amount Pv of the duty factor D depending on the power supply voltage of the fuel pump 4. A table (data table) corresponding to the characteristic diagram shown in Fig. 3 is previously stored in the memory integrated with the ECU 9. In this way, when the power supply voltage of the fuel pump 4 is more than a rating voltage Vo, a pulse-width of the PWM signal is made smaller than that in the case where the power supply voltage of the fuel pump 4 is equal to the rating voltage Vo, so that the drive power of the fuel pump 4 can be lowered and thereby the power consumption thereof can be reduced. Similarly, when the power supply voltage of the fuel pump 4 is smaller than the rating voltage Vo, the pulse-width of the PWM signal is made larger than that in the case where the power supply voltage of the fuel pump 4 is equal to the rating voltage Vo, so that the fuel injection amount (or injection pressure) can be prevented from becoming deficient depending on a change in power supply voltage of the fuel pump 4. In other words, the drive of the fuel pump 4 can be controlled such that the fuel injection amount is prevented from being varied depending on a change in power supply voltage of the fuel pump 4. As shown in Fig. 4, the switching means 11 shown in Fig. 1 may be formed of a relay RY and a resistance R. Referring to Fig. 4, one contact of the relay RY is connected to an input terminal while the other contact of the relay RY is connected to an output terminal, and the resistance R is connected between the input and output terminals. One end of a coil of the relay RY is connected to the control terminal T and the other end of the coil is connected to the output terminal. During flow of a current in the coil, both the contacts are connected to each other by a movable contact piece of the relay RY to be thus short-circuited. Referring to Fig. 4, a power switching signal on the basis of a required fuel amount is supplied from the ECU 9 to the control terminal T. For example, a table (data table) indicating characteristics between the required fuel amount (fuel injection amount determined by calculation) and the power switching signal as shown in Fig. 5 is previously stored in the memory integrated with the ECU 9. The ON/OFF states (H/L levels) of the power switching signal correspond to the ON/OFF states of the relay RY. The filter 3 shown in Fig. 1 may be disposed in the fuel tank 2 as a strainer, and the fuel injector 6 may include a solenoid valve. An oxygen detecting sensor may be provided in an exhaust pipe or exhaust manifold for detecting a fuel injection amount from an exhaust gas and inputting the detection data in the control data. The above-described embodiment of the present invention is for illustrative purposes only, and it is to be understood that the present invention is not limited thereto. According to the drive unit for driving a fuel pump for a small-sized vehicle, since the drive of the fuel pump is controlled on the basis of control data of an injection amount of the fuel injector and of a power supply voltage of the fuel pump, the drive of the fuel pump can be controlled such that a drive power of the fuel pump is reduced in the case where the fuel injection amount is small. The drive of the fuel pump can be also controlled such that the fuel injection amount (or injection pressure) is prevented from becoming deficient depending on a change in power supply voltage of the fuel pump. For example, the drive unit is configured that a pulse-width of a PWM signal is made larger with an increase in fuel injection amount of the fuel injector so that the fuel pump can be driven at the maximum flow rate when the pulse-width is maximized; and further, the pulse-width of the PWM signal is made smaller with a decrease in fuel injection amount of the fuel injector so that a power consumption of the fuel pump can be reduced when the fuel injection amount is small. For example, when a power supply voltage of the fuel pump is larger than a rating voltage, the drive power of the fuel pump can be lowered and thereby the power consumption thereof can be reduced by making smaller a pulse width of a PWM signal than that in the case where the power supply voltage of the fuel pump is equal to the rating voltage. When the power supply voltage of the fuel pump is smaller than the rating voltage, the fuel injection amount (or injection pressure) can be prevented from becoming deficient depending on a change in power supply voltage of the fuel pump by making larger the pulse-width of the PWM signal than that in the case where the power supply voltage of the fuel pump is equal to the rating voltage. In summary it is an object of the invention to provide a drive unit for driving a fuel pump 4 for a small-sized vehicle, which is capable of reducing a current consumption of the fuel pump 4. A drive unit for driving a fuel pump 4 for a small-sized vehicle includes an ECU 9 for controlling a fuel injection amount of a fuel injector 6. The ECU 9 drives the fuel pump 4 on the basis of control data for controlling the fuel injection amount of the fuel injector 6 and of a power supply voltage of the fuel pump 4. For example, the fuel pump 4 is driven under pulse-width modulation (PWM) in such a manner that a pulse-width of a PWM signal is made larger with an increase in fuel injection amount of the fuel injector 6 and is made smaller with a decrease in fuel injection amount of the fuel injector 6. Explanation of Characters: 2: fuel tank, 3, 5: filter, 4: fuel pump (PUMP), 6: fuel injector, 7: intake manifold, 8: pressure regulator, 9: electronic control unit (ECU), 10: on-vehicle battery (BAT), 11: switching means (SW), 15: air cleaner (A/C), 16: throttle valve, 17: intake valve, 18: ignition plug, 19: exhaust valve, 20: exhaust manifold, 21: piston, 22: piston pin, 23: combustion chamber, C: capacitor, D: duty factor, Pv: correction amount of duty factor D, R: resistance, RY: relay, T: control terminal of switching means 11.

Claims: A drive unit for driving a fuel pump (4) for a small-sized vehicle, comprising: an electronic control unit (9) for controlling a fuel injection amount of a fuel injector (6); wherein said electronic control unit (9) drives said fuel pump (4) on the basis of control data for controlling a fuel injection amount of said fuel injector (6) and of a power supply voltage applied to said fuel pump (4) and wherein said power supply voltage is taken into consideration in form of a correction term Pv depending on said power supply voltage, when a control signal for said fuel pump (4) is calculated by said electronic control unit (9) characterized in that a duty factor D of said control signal is calculated in accordance with the following equation: D = A + Ti x Ne x K + Pv, wherein A is a minimum duty factor, Ti is a fuel injection amount, Ne is an engine speed, K is a correction coefficient, and Pv is an additive correction term. A drive unit for driving a fuel pump (4) for a small-sized vehicle according to claim 1, wherein said electronic control unit (9) drives said fuel pump (4) under pulse-width modulation (PWM) using a PWM signal with said duty factor D in such a manner, that a pulse-width of the PWM signal is made larger with an increase in fuel injection amount of said fuel injector (6) and is made smaller with a decrease in fuel injection amount of said fuel injector (6). A drive unit for driving a fuel pump (4) for a small-sized vehicle according to claim 1 or 2, wherein said electronic control unit (9) drives said fuel pump (4) under pulse-width modulation (PWM) using a PWM signal with said duty factor D in such a manner, that when the power supply voltage of said fuel pump (4) is larger than a rating voltage, a pulse-width of the PWM signal is made smaller than that in the case where the power supply voltage is equal to the rating voltage; and when the power supply voltage of said fuel pump (4) is smaller than the rating voltage, the pulse-width of the PWM signal is made larger than that in the case where the power supply voltage is equal to the rating voltage.

Inventors: KONNO TAKESHI, TANAKA HIROSHI, KONNO, TAKESHI, TANAKA, HIROSHI
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1998
Main classification: F02D41
IPC codes: F02D41, F02M37