EP2169213A2

EP2169213A2 - Starting system for fuel injection engine

Info

Publication number: EP2169213A2
Application number: EP09170112A
Authority: EP
Inventors: Takeo Takahashi
Original assignee: Keihin Corp
Current assignee: Keihin Corp
Priority date: 2008-09-24
Filing date: 2009-09-11
Publication date: 2010-03-31
Anticipated expiration: 2029-09-11
Also published as: EP2169213A3; JP2010077822A; EP2169213B1; JP5113696B2

Abstract

In a control system for a fuel injection engine in which at least operations of a fuel injection valve and a fuel pump are controlled by an electrical control unit to become incapable of control processing in a state in which a voltage of a battery reaches a predetermined reset voltage or lower, prohibition signal output means (41) outputs a prohibition signal for prohibiting operation of the fuel pump (34) by detecting starting of operation of a starter motor; permission signal output means (42) outputs a permission signal for permitting operation of the fuel pump (34) by determining that a pump operation permission state capable of avoiding a voltage of the battery reaching a predetermined reset voltage or lower even by operation of the fuel pump (34) has reached prior to fuel injection by the fuel injection valve after operation of the fuel pump (34) is stopped in response to starting of operation of the starter motor; and pump drive means (43) drives the fuel pump (34) according to a prohibition signal output from the prohibition signal output means (41) and a permission signal output from the permission signal output means (42). Accordingly, it is possible to enhance engine startability when a battery has deteriorated.

Description

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The present invention relates to a control system for a fuel injection engine comprising: a fuel injection valve for injecting fuel; a fuel pump for supplying fuel to the fuel injection valve; a starter motor capable of transmitting starting power to a crankshaft; a generator connected to the crankshaft; a battery for supplying operating power to the fuel pump, the fuel injection valve, and the starter motor; and an electronic control unit for controlling operations of at least the fuel injection valve and the fuel pump so that control processing is disabled when a voltage of the battery is equal to or less than a predetermined reset voltage.

DESCRIPTION OF THE RELATED ART

An engine control system for enabling operation of a fuel pump even in a state in which battery voltage is low when an engine is being started by cranking with a starter motor is known from Japanese Patent Application Laid-open No. 07-317620 .
Now, an electronic control unit for controlling the operation of a fuel pump, etc. generally becomes incapable of control processing in a state in which the voltage of a battery reaches a predetermined reset voltage or lower. In the arrangement disclosed in Japanese Patent Application Laid-open No. 07-317620 in which the operation of a fuel pump is made possible even in a state in which the battery voltage is low when the engine is being started, since the electronic control unit becomes incapable of control processing in a state in which the battery has deteriorated after a long term use, etc., even if the extent of the deterioration is small, it becomes difficult to start the engine.

SUMMARY OF THE INVENTION

The present invention has been accomplished in the light of such circumstances, and it is an object thereof to provide a control system for a fuel injection engine in which engine startability when a battery has deteriorated is enhanced.
In order to achieve the object, according to a first feature of the present invention, there is provided a control system for a fuel injection engine comprising: a fuel injection valve for injecting fuel; a fuel pump for supplying fuel to the fuel injection valve; a starter motor capable of transmitting starting power to a crankshaft; a generator connected to the crankshaft; a battery for supplying operating power to the fuel pump, the fuel injection valve, and the starter motor; and an electronic control unit for controlling operations of at least the fuel injection valve and the fuel pump so that control processing is disabled when a voltage of the battery is equal to or less than a predetermined reset voltage, characterized in that the electronic control unit includes: prohibition signal output means for outputting a prohibition signal for prohibiting operation of the fuel pump by detecting starting of operation of the starter motor; permission signal output means for outputting a permission signal for permitting operation of the fuel pump by determining that a pump operation permission state has reached prior to fuel injection by the fuel injection valve after operation of the fuel pump is stopped in response to starting of operation of the starter motor, the pump operation permission state being capable of avoiding the voltage of the battery to reach a predetermined reset voltage or lower even by operation of the fuel pump; and pump drive means for driving the fuel pump by stopping operation of the fuel pump according to a prohibition signal output from the prohibition signal output means and by starting operation of the fuel pump according to a permission signal output from the permission signal output means after the prohibition signal is outputted.
In accordance with the first feature of the present invention, when the operation of the starter motor is started, prior to fuel injection after operation of the fuel pump is temporarily stopped, it is determined by the permission signal output means whether or not a pump operation permission state has reached in which it is possible to avoid the battery voltage reaching a reset voltage or lower even if the fuel pump is operated. When the permission signal output means determines that there is such a state, drive of the fuel pump is started. Accordingly, it is possible to enhance the startability even when the battery has deteriorated at the time of starting the engine with the starter motor being operated, by avoiding control processing by the electronic control unit becoming disabled even by operation of the fuel pump.
According to a second feature of the present invention, in addition to the first feature, there is provided the control system for a fuel injection engine, further comprising a starter switch for controlling operation of the starter motor, wherein the prohibition signal output means detects starting of operation of the starter motor based on a change in the switching mode of the starter switch.
Furthermore, in accordance with the second feature of the present invention, since starting of operation of the starter motor is detected based on a change in the switching mode of the starter switch, starting of operation of the starter motor can be detected reliably.
According to a third feature of the present invention, in addition to the first feature, there is provided the control system for a fuel injection engine, further comprising voltage detection means for detecting a voltage of the battery, wherein the prohibition signal output means determines that operation of the starter motor has started according to a decrease in battery voltage detected by the voltage detection means to a predetermined prohibition threshold value or lower.
In accordance with the third feature of the present invention, since it is determined that operation of the starter motor has started according to a decrease in the battery voltage to a predetermined prohibition threshold value or lower, the invention can easily be applied to one in which operation of the starter motor is not controlled by an electronic control unit.
According to a fourth feature of the present invention, in addition to any one of the first to third features, there is provided the control system for a fuel injection engine, further comprising a crank sensor for outputting a crank pulse that is dependent on rotation of the crankshaft, wherein based on the crank pulse the permission signal output means determines that the pump operation permission state has reached when a crank angle of the crankshaft reaches a predetermined value.
In accordance with the fourth feature of the present invention, it is determined based on the crank pulse that a pump operation permission state has reached when the crank angle of the crankshaft reaches a predetermined value, and based on the ignition and fuel injection timings being determined according to the crank angle at the time of cranking by the starter motor it is possible to reliably determine a pump operation permission state prior to fuel injection and start operation of the fuel pump.
According to a fifth feature of the present invention, in addition to any one of the first to third features, there is provided the control system for a fuel injection engine, further comprising voltage detection means for detecting a voltage of the battery, wherein the permission signal output means determines that the pump operation permission state has reached according to the battery voltage detected by the voltage detection means exceeding a predetermined permission threshold value.
In accordance with the fifth feature of the present invention, since it is determined that a pump operation permission state has reached according to the battery voltage exceeding a predetermined permission threshold value, it is possible to reliably determine a pump operation permission state that can avoid the battery voltage decreasing to a reset voltage or lower even by operation of the fuel pump.
According to a sixth feature of the present invention, in addition to any one of the first to third features, the permission signal output means determines that the pump operation permission state has reached according to a predetermined time having elapsed after a prohibition signal has been outputted from the prohibition signal output means.
Furthermore, in accordance with the sixth feature of the present invention, since it is determined that a pump operation permission state has reached according to a predetermined time having elapsed after operation of the fuel pump is prohibited by means of a prohibition signal output from the prohibition signal output means, simple control without involving crank angle or battery voltage is possible, and the invention can easily be applied to an engine of a conventional specification.
The above description, other objects, characteristics and advantages of the present invention will be clear from detailed descriptions which will be provided for the preferred embodiment referring to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 4 show a first embodiment of the present invention:

FIG. 1 is a view showing an arrangement of a control system of a fuel injection engine;
FIG. 2 is a view showing an arrangement of a portion, which is related to a fuel pump control at the time of starting the engine, of an electronic control unit;
FIG. 3 is a flow chart showing fuel pump control procedure at the time of starting the engine;
FIG. 4 is a timing chart showing a change with the passage of time of a starter motor, a battery voltage, a fuel pump and an engine rotational speed at the time of starting the engine.
FIG. 5 is a flow chart showing a fuel pump control procedure at the time of starting an engine of a second embodiment of the present invention.
FIG. 6 is a flow chart showing a fuel pump control procedure at the time of starting an engine of a third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the present invention will be described below base on the attached drawings.
First in FIG. 1, a crankshaft 15 is rotatably supported on a crankcase 12 of an engine main body 11 of a fuel injection engine, and a piston 16 slidably fitted into a cylinder block 13 joined to the crankcase 12 is connected to the crankshaft 15 via a connecting rod 17. Moreover, a starter motor 18 for transmitting power for starting to the crankshaft 15 at the time of starting is connected to the crankshaft 15 via a reduction mechanism 19, and a generator 20 that generates power in response to rotation of the crankshaft 15 is coaxially connected thereto.
A cylinder head 14, which forms part of the engine main body 11, is joined to the cylinder block 13 so as to form between itself and the cylinder block 13 a combustion chamber 21 that a top part of the piston 16 faces. An intake port 22 and an exhaust port 23 communicating with the combustion chamber 21 are provided in the cylinder head 14. An intake valve 24 for switching between provision and blockage of communication of the intake port 22 with the combustion chamber 21 and an exhaust valve 25 for switching between provision and blockage of communication of the exhaust port 23 with the combustion chamber 21 are disposed in the cylinder head 14 so as to be capable of opening and closing, a spark plug 26 having a tip end part which faces the combustion chamber 21 is mounted on the cylinder head 14, and a spark coil 27 is connected to the spark plug 26.
An intake system 28 connected to the intake port 22 includes a throttle body 30 having an intake path 29 communicating with the intake port 22, a throttle valve 31 for opening and closing the intake path 29 is disposed in the throttle body 30 so as to be capable of opening and closing, and a fuel injection valve 32 for injecting fuel is attached to the throttle body 30. Fuel within a fuel tank 33 is supplied to the fuel injection valve 32 from a fuel pump 34 disposed in a bottom part of the fuel tank 33.
Power for operation is supplied from a battery 35 to the fuel pump 34, the fuel injection valve 32, and the starter motor 18. An electronic control unit 36 controls operations of at least the fuel injection valve 32 and the fuel pump 34, in this embodiment operation of the fuel injection valve 32, the fuel pump 34, and the starter motor 18 and timing of ignition of the spark plug 26 by the spark coil 27. Inputted into the electronic control unit 36 are crank pulses from a crank sensor 38 fixedly disposed so as to face the outer periphery of a pulser 37 fixed to the crankshaft 15, a signal from a starter switch 39 for determining the timing of starting operation of the starter motor 18, and battery voltage from voltage detection means 40 for detecting the voltage of the battery 35.
As shown in FIG. 2, a section of the electronic control unit 36 involved in control of the fuel pump 34 at the time of starting the engine includes: prohibition signal output means 41 for outputting a prohibition signal for prohibiting operation of the fuel pump 34 by detecting starting of operation of the starter motor 18; permission signal output means 42 for outputting a permission signal for permitting operation of the fuel pump 34 by determining that a pump operation permission state has reached in which it is possible to avoid the voltage of the battery 35 reaching a predetermined reset voltage or lower even by operation of the fuel pump 34 prior to fuel injection by the fuel injection valve 32 after operation of the fuel pump 34 has been stopped in response to starting of operation of the starter motor 18; and pump drive means 43 for driving the fuel pump 34 by stopping operation of the fuel pump 34 in response to a prohibition signal output from the prohibition signal means 42 and by starting operation of the fuel pump 34 in response to a permission signal output from the permission signal output means after a prohibition signal has been outputted.
The prohibition signal output means 41 detects starting of operation of the starter motor 18 based on a change in the switching mode of the starter switch 39 for controlling the operation of the starter motor 18, and the permission signal output means 42 determines, based on crank pulses outputted from the crank sensor 38 in response to rotation of the crankshaft 15, that a pump operation permission state has reached when the crank angle of the crankshaft 15 attains a predetermined value prior to starting of fuel injection from the fuel injection valve 32; for example, it determines that a pump operation permission state has reached when the piston 16 attains top dead center.
Such an electronic control unit 38 carries out control of operation of the fuel pump 34 at the time of starting the engine in accordance with the procedure shown in FIG. 3; in step S1 computation of a crank angle of the crankshaft 15 is carried out based on crank pulses output from the crank sensor 38, and in step S2 it is determined whether or not the crank angle has attained a predetermined value. That is, step S1 and step S2 are processing steps that are carried out by the permission signal output means 42, and when it is determined that the crank angle has not attained the predetermined value, the procedure moves on from step S2 to step S3.
In step S3, in order to start operation of the starter motor 18, it is determined whether or not the starter switch 39 is in an ON state, and when it is determined that the starter switch 39 is in an OFF state, the procedure moves on to step S4. In this step S4, it is determined whether or not a battery voltage VB detected by the voltage detection means 40 exceeds a predetermined value V1, for example 7V, and if it exceeds the predetermined value V1 the procedure moves from step S4 to step S5 and the count value of a counter is increased by only "1"; if in the following step S6 it is determined that the count value is equal to or less than "20" the procedure moves from step S6 to step S7 and the fuel pump 34 is operated, and if the count value exceeds "20" the procedure moves from step S6 to step S8 and operation of the fuel pump 34 is stopped.
That is, at the time of starting the engine, the fuel pump 34 is operated as preliminary drive before operation of the starter motor 18 is started, and since computation processing by the electronic control unit 36 is carried out, for example, every 100 msec, the fuel pump 34 is preliminarily driven for a maximum of, for example, 2 sec.
Here, the determination processing in step S3 is carried out by the prohibition signal output means 41, and when it is determined that the starter switch 39 for controlling operation of the starter motor 18 is in an ON state, the procedure moves from step S3 to step S8, and a prohibition signal for prohibiting operation of the fuel pump 34 is outputted.
Furthermore, if in step S2 it is determined that the crank angle has attained a predetermined value, a pump operation permission state has reached, and after it is confirmed in step S9 that the engine has not stalled, the procedure moves to step S7 and an operation permission signal is outputted.
In accordance with such control at the time of starting the engine by means of the electronic control unit 36, at the time of starting the engine, the starter motor 18, the battery voltage VB, the fuel pump 34, and an engine rotational speed NE change as shown in FIG. 4, and when it is confirmed that operation of the starter motor 18 has been started by the starter switch 39 at a time t1 after the fuel pump 34 has been preliminarily driven only for a period of less than 2 sec in a state in which the battery voltage VB exceeds the predetermined value V1, operation of the fuel pump 34 is stopped.
If operation of the fuel pump 34 were continued, the battery voltage VB would rapidly decrease, as shown by the broken line, in response to starting of operation of the starter motor 18, but as described above by temporarily stopping operation of the fuel pump 34 it is possible to suppress the decrease in the battery voltage VB due to starting of operation of the starter motor 18.
When starting power is inputted into the crankshaft 15 by operation of the starter motor 18 from the time t1, the generator 20 connected to the crankshaft 15 operates, and the battery voltage VB gradually increases due to charging by power generation thereof. At a time t2 after operation of the fuel pump 34 has been stopped at time t1, and when it is detected that the piston 16 before fuel injection from the fuel injection valve 32 is started has attained a crank angle that corresponds to top dead center, operation of the fuel pump 34 is started.
Next, the operation of the first embodiment is explained. At the time of starting operation of the starter motor 18, prior to fuel injection after operation of the fuel pump 34 has been temporarily stopped, it is determined by the permission signal output means 42 whether or not a pump operation permission state has reached in which it is possible to avoid the voltage of the battery 35 reaching a reset voltage VR or lower (see FIG. 4) even by operation of the fuel pump 34, and if the permission signal output means 42 determines that there is such a state drive of the fuel pump 34 is started, and it is therefore possible to enhance the startability by avoiding the electronic control unit 36 becoming incapable of control processing even by operation of the fuel pump 34 even when the battery 35 has deteriorated at the time of starting the engine, on which the starter motor 18 is being operated.
Furthermore, since starting of operation of the starter motor 18 is detected based on a change in the switching mode of the starter switch 39, it is possible to reliably detect starting of operation of the starter motor 18.
Moreover, it is determined based on the crank pulses that a pump operation permission state has reached when the crank angle of the crankshaft 15 has attained a predetermined value, and based on the ignition and fuel injection timings being determined by the crank angle at the time of cranking by the starter motor 18 it is possible to reliably determine a pump operation permission state prior to fuel injection and start operation of the fuel pump 34.
FIG. 5 shows a control procedure at the time of starting an engine of a second embodiment of the present invention. In step S11, it is determined whether or not a battery voltage VB exceeds a predetermined prohibition threshold value V2 (see FIG. 4 of the first embodiment), and if it is determined that the battery voltage VB has decreased to the predetermined prohibition threshold value V2 or lower, prohibition signal output means 41 determines that operation of a starter motor 18 has started, and in step S12 a prohibition signal for prohibiting operation of a fuel pump 34 is outputted.
Furthermore, if it is determined in step S11 that the battery voltage VB has exceeded the predetermined prohibition threshold value V2, the procedure moves from step S11 to step S13, and it is determined whether or not the battery voltage VB has exceeded a predetermined permission threshold value V3. This permission threshold value V3 is set as a value that can avoid the battery voltage VB reaching a reset voltage VR or lower even by operation of the fuel pump 34 prior to fuel injection by a fuel injection valve 32 after operation of the fuel pump 34 is stopped, and is set so as to be larger than the prohibition threshold value V2.
If in step S13 it is determined that the battery voltage VB is equal to or lower than the predetermined permission threshold value V3, the procedure moves on to step S12, and if the battery voltage VB exceeds the predetermined permission threshold value V3, it is determined that a pump operation permission state has reached and the procedure moves on to step S14.
In step S14, it is determined whether or not the engine has stalled, and when it is determined that it has not, in step S15 an operation permission signal is outputted.
Furthermore, if it is determined in step S14 that the engine has stalled, in step S16 the start count value of a start counter is increased only by "1", and if in the following step S17 it is determined that the start count value exceeds "20" the procedure moves on to step S12, and if the start count value is not greater than "20" the procedure moves on to step S15.
In accordance with the second embodiment, since operation of the fuel pump 34 is stopped by determining that operation of the starter motor 18 has started according to a decrease in the battery voltage VB to the predetermined prohibition threshold value V2 or lower, this can easily be applied to one in which operation of the starter motor 18 is not controlled by an electronic control unit 36.
Furthermore, since it is determined that a pump operation permission state has reached according to the battery voltage VB exceeding the predetermined permission threshold value V3, it is possible to reliably determine the pump operation permission state, in which it is possible to avoid the voltage of the battery 35 reaching the reset voltage VR or lower even by operation of the fuel pump 34.
FIG. 6 shows a control procedure at the time of starting an engine of a third embodiment of the present invention. In step S21, in order to start operation of a starter motor 18, it is determined whether or not a starter switch 39 is in an ON state, and if it is determined that the starter switch 39 is in an OFF state, in step S22 it is determined whether or not the engine has stalled, and if it is determined that it has not an operation permission signal is outputted in step S23.
Furthermore, if it is determined in step S21 that the starter switch 39 is in an ON state, in step S24 the stop count value of a stop counter is increased by only "1", in the following step S25 it is determined whether or not the stop count value exceeds "10", that is, whether or not it exceeds 1 sec, and if it is determined that it is no greater than 1 sec, the procedure moves on to step S26, and a prohibition signal for prohibiting operation of the fuel pump 34 is outputted.
Moreover, if in step S25 it is determined that the stop count value exceeds "10" the procedure moves from step S25 to step S22.
Furthermore, if in step S22 it is determined that the engine has stalled, in step S27 the start count value of a start counter is increased by only "1", if in step S28 it is determined that the start count value exceeds "20" the procedure moves on to step S26, and if it is determined that the start count value is equal to or less than "20" the procedure moves on to step S23.
In accordance with this third embodiment, since it is determined that there is a pump operation permission state according to a predetermined time, for example 1 sec, having elapsed after a prohibition signal for prohibiting operation of the fuel pump 34 is outputted by the starter switch 39 attaining an ON state, it is possible to carry out simple control without involving crank angle or battery voltage VB, and it can easily be applied to an engine of a conventional specification.
Embodiments of the present invention are explained above, but the present invention is not limited to the above-mentioned embodiments and may be modified in a variety of ways as long as the modifications do not depart from the gist of the present invention.
In a control system for a fuel injection engine in which at least operations of a fuel injection valve and a fuel pump are controlled by an electrical control unit to become incapable of control processing in a state in which a voltage of a battery reaches a predetermined reset voltage or lower, prohibition signal output means (41) outputs a prohibition signal for prohibiting operation of the fuel pump (34) by detecting starting of operation of a starter motor; permission signal output means (42) outputs a permission signal for permitting operation of the fuel pump (34) by determining that a pump operation permission state capable of avoiding a voltage of the battery reaching a predetermined reset voltage or lower even by operation of the fuel pump (34) has reached prior to fuel injection by the fuel injection valve after operation of the fuel pump (34) is stopped in response to starting of operation of the starter motor; and pump drive means (43) drives the fuel pump (34) according to a prohibition signal output from the prohibition signal output means (41) and a permission signal output from the permission signal output means (42). Accordingly, it is possible to enhance engine startability when a battery has deteriorated.

Claims

A control system for a fuel injection engine comprising:
a fuel injection valve (32) for injecting fuel;

a fuel pump (34) for supplying fuel to the fuel injection valve (32);

a starter motor (18) capable of transmitting starting power to a crankshaft (15);

a generator (20) connected to the crankshaft (15);

a battery (35) for supplying operating power to the fuel pump (34), the fuel injection valve (32), and the starter motor (18); and

an electronic control unit (36) for controlling operations of at least the fuel injection valve (32) and the fuel pump (34) so that control processing is disabled when a voltage of the battery (35) is equal to or less than a predetermined reset voltage,

characterized in that

the electronic control unit (36) includes:

prohibition signal output means (41) for outputting a prohibition signal for prohibiting operation of the fuel pump (34) by detecting starting of operation of the starter motor (18);

permission signal output means (42) for outputting a permission signal for permitting operation of the fuel pump (34) by determining that a pump operation permission state has reached prior to fuel injection by the fuel injection valve (32) after operation of the fuel pump (34) is stopped in response to starting of operation of the starter motor (18), the pump operation permission state being capable of avoiding the voltage of the battery (35) to reach a predetermined reset voltage or lower even by operation of the fuel pump (34); and

pump drive means (43) for driving the fuel pump (34) by stopping operation of the fuel pump (34) according to a prohibition signal output from the prohibition signal output means (41) and by starting operation of the fuel pump (34) according to a permission signal output from the permission signal output means (42) after the prohibition signal is outputted.
The control system for a fuel injection engine according to Claim 1, further comprising a starter switch (39) for controlling operation of the starter motor (18), wherein the prohibition signal output means (41) detects starting of operation of the starter motor (18) based on a change in the switching mode of the starter switch (39).
The control system for a fuel injection engine according to Claim 1, further comprising voltage detection means (40) for detecting a voltage of the battery (35), wherein the prohibition signal output means (41) determines that operation of the starter motor (18) has started according to a decrease in battery voltage detected by the voltage detection means (40) to a predetermined prohibition threshold value or lower.
The control system for a fuel injection engine according to any one of Claims 1 to 3, further comprising a crank sensor (38) for outputting a crank pulse that is dependent on rotation of the crankshaft (15), wherein based on the crank pulse the permission signal output means (42) determines that the pump operation permission state has reached when a crank angle of the crankshaft (15) reaches a predetermined value.
The control system for a fuel injection engine according to any one of Claims 1 to 3, further comprising voltage detection means (40) for detecting a voltage of the battery (35), wherein the permission signal output means (42) determines that the pump operation permission state has reached according to the battery voltage detected by the voltage detection means (40) exceeding a predetermined permission threshold value.
The control system for a fuel injection engine according to any one of Claims 1 to 3, wherein the permission signal output means (42) determines that the pump operation permission state has reached according to a predetermined time having elapsed after a prohibition signal has been outputted from the prohibition signal output means (41).