CN107614854B - Fuel pump control device and control method - Google Patents

Abstract

The piston (56) is reciprocated by the drive of the DC motor (42) and pressurized fuel is delivered to the injector (16) and injected from the injector (16) in synchronization with the combustion cycle of the engine (1). The engine rotation period (Teg) and the motor rotation period (Tmt) are compared (S3), and if the two are different, the proportion of the driving current of the DC motor (42) is calculated according to the operating region of the engine (1) by a normal method. The duty ratio (S4) is performed to increase or decrease the duty ratio of the drive current flowing into the DC motor (42) by a predetermined value when the engine rotation period (Teg) and the motor rotation period (Tmt) are close to each other. Correction ( S6 ) is performed, whereby the DC motor ( 42 ) is driven and controlled according to the corrected duty ratio ( S5 ). Thereby, when the engine (1) is operating, the motor rotation period (Tmt) is always made different from the engine rotation period (Teg).

Description

Fuel pump control device and control method

technical field

The present invention relates to a control device for a fuel pump and a control method for the fuel pump, and more particularly to a control device for a piston-type fuel pump that uses an electric motor as a drive source to reciprocate a piston to pressurize fuel pressurized to a predetermined pressure to an injector of an engine and control methods.

Background technique

Conventionally, for the purpose of improving exhaust gas characteristics and improving fuel consumption, fuel injection devices that electronically control the fuel supply to the engine have become popular, not only for four-wheeled vehicles, but also for various types of two-wheeled vehicles and power generation. machine etc. Such a fuel injection device is configured to draw fuel in a fuel tank by a fuel pump, pressurize it to a predetermined pressure, supply the pressurized fuel to an injector provided in an intake pipe of an engine, and inject the fuel in synchronization with the combustion cycle of the engine. The injector is opened and closed to inject fuel into the intake pipe.

As such a fuel pump, for example, in an engine with a small displacement used in a motorcycle or a generator, it is desired not only to reduce the size of the fuel pump body but also to reduce the power consumption required for driving the pump. Piston-type fuel pumps with characteristics matching these conditions are sometimes employed.

Such a piston-type fuel pump is configured to be slidably disposed in a cylinder, to be biased in one direction by a return spring, and to drive the piston in an opposite direction by excitation of an electromagnetic coil. The piston reciprocates based on the periodic excitation of the electromagnetic coil, and accordingly, the fuel is pressurized in the cylinder to be discharged intermittently. Due to such an operation principle, the pressure of the fuel supplied to the injector periodically fluctuates based on the reciprocating motion of the piston, and even if the control is performed during the valve opening time of the same injector, the fuel injection amount is generated due to the fluctuation of the fuel pressure. Deviation, the combustion of the engine becomes unstable, and the exhaust gas characteristics and drivability are deteriorated.

Therefore, for example, in the piston-type fuel pump described in Patent Document 1, it is attempted to solve the problem by synchronizing the driving of the fuel pump with the rotation of the engine. That is, in the piston-type fuel pump described in Patent Document 1, the injector is driven within the fuel injection time Tout from the fuel injection start time t2 in synchronization with the rotation of the engine, while the fuel injection start time t2 is shorter than the fuel injection start time t2. The time earlier than the predetermined time Tf is determined as the fuel pump drive start time t1, and the fuel pump is driven (the solenoid is excited) throughout the fuel pump drive time Tpump from the fuel pump drive start time t1. As a result, by constantly executing fuel injection at the timing at which the fuel pressure is increased by the driving of the fuel pump, it is possible to suppress variations in the fuel injection amount due to fuel pressure fluctuations.

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2004-52596

SUMMARY OF THE INVENTION

The technical problem to be solved by the invention

In the piston-type fuel pump described in Patent Document 1, since the excitation timing of the electromagnetic coil serving as the driving source can be freely changed for each combustion cycle of the engine, it is possible to follow the fuel injection that changes from time to time based on the operating region of the engine. Timing, the driving timing of the fuel pump is controlled as described above. However, in a piston-type fuel pump using an electric motor as a drive source, it is necessary to change the rotational speed of the electric motor in order to change the driving timing, and it is difficult to quickly change the rotational speed of the electric motor by tracking the fuel injection timing in practice. Therefore, the technique of Patent Document 1 cannot be applied to a piston-type fuel pump using an electric motor as a drive source, and other solutions have been desired.

The present invention has been made in order to solve the above-mentioned problems, and an object thereof is to provide a fuel pump control device and control method, which are aimed at a piston-type fuel pump using an electric motor as a driving source and suppress the fuel pressure fluctuation caused by the fuel pump. The deviation of the fuel injection amount prevents the deterioration of exhaust gas characteristics and drivability in advance.

technical solutions to technical problems

In order to achieve the above-mentioned object, a fuel pump control device of the present invention is characterized by including a piston-type fuel pump that reciprocates a piston by driving a motor to reciprocate a fuel pressurized to a predetermined pressure pressure-feeding; an injector that injects fuel pressure-fed from a fuel pump in synchronism with the combustion cycle of the engine; a motor control unit that supplies a drive current to an electric motor and controls the electric motor; a determination unit that The determination unit executes a determination output for determining whether either one of the fuel injection period of the injector and the fuel pressure feeding period of the piston is equivalent to a multiple of the other; and a motor speed change instruction unit that is determined by the determination unit When either one of the fuel injection cycle of the injector and the fuel pressure feeding cycle of the piston is a multiple of the other, the motor control unit is caused to change the rotation speed of the motor.

According to the fuel pump control device of the present invention configured as described above, when either one of the fuel injection cycle of the injector and the fuel pressure feeding cycle of the piston corresponds to a multiple of the other, the rotation speed of the electric motor is changed to separate the fuel pressure feeding cycle fuel injection cycle. Therefore, during engine operation, the fuel injection period and the fuel injection period are always made different, and the relationship between the fuel injection timing and the fuel injection timing is changed for each combustion cycle. Therefore, even if the fuel injection timing and the fuel pressure feed timing accidentally overlap in a certain combustion cycle, the timing of the two will inevitably not overlap in the next combustion cycle, resulting in unstable operation of the engine due to the deviation of the fuel injection amount. The state ends at the instant of 1 combustion cycle.

As another mode, it is preferably configured to further include: an engine rotation period calculation unit, which calculates the rotation period of the engine; and a motor rotation period calculation unit, which calculates the rotation period of the motor, and determines The unit compares the rotation period of the engine calculated by the engine rotation period calculation unit with the rotation period of the electric motor calculated by the motor rotation period calculation unit, thereby performing determination processing.

In the case of the above configuration, the rotational speed of the electric motor is changed based on the determination result of comparing the rotation period of the engine and the rotation period of the electric motor.

As another mode, it is preferable to further include: a fuel injection timing determination unit that determines the fuel injection timing of the injector; and a fuel pressure feed timing determination unit that determines the fuel pressure feed timing according to the fuel injection timing determined by the motor control unit. The change in the value of the drive current supplied to the electric motor determines the fuel injection timing of the piston, and the determination means determines the fuel injection timing of the injector determined by the fuel injection timing determination means and the fuel injection timing of the piston determined by the fuel injection timing determination means. The pressure feeding timings are compared to execute the judgment process.

In the above configuration, the fuel pressure feeding timing of the piston is determined based on the change in the drive current value of the electric motor, and the rotation speed of the electric motor is changed according to the result of comparison between the fuel pressure feeding timing and the fuel injection timing of the injector.

Alternatively, the fuel pump is preferably configured such that the diaphragm is reciprocated by the drive of the electric motor, the piston is reciprocated in synchronization with the reciprocating motion of the diaphragm, and the fuel sent from the diaphragm is pressurized and fed by the piston. to the injector.

In the case of the above-described configuration, the above-described various effects can be obtained for a fuel pump that uses both a diaphragm and a piston.

In addition, the fuel pump control method of the present invention is characterized by comprising: a cycle determination step in which fuel is pressurized to a piston-type fuel pump that reciprocates a piston by driving a motor to pressurize fuel. The cycle is compared with the fuel injection cycle of the injector that injects the fuel pressurized from the fuel pump in synchronization with the combustion cycle of the engine, and it is determined whether either the fuel injection cycle or the fuel injection cycle corresponds to the other. and a rotational speed changing step of changing the rotational speed of the electric motor when it is determined by the cycle determination step that either the fuel pressure feeding cycle or the fuel injection cycle corresponds to a multiple of the other.

According to the fuel pump control method of the present invention configured as described above, the cycle determination step compares the fuel injection cycle of the piston-type fuel pump with the fuel injection cycle of the injector, and determines the fuel injection cycle and the fuel injection cycle Whether any one of them is equivalent to a multiple of the other. Then, when it is determined that either the fuel pressure feeding period or the fuel injection period corresponds to a multiple of the other, the rotational speed of the electric motor is changed in the rotational speed changing step so that the fuel pressure feeding period is separated from the fuel injection period.

Invention effect

According to the control device and control method of the fuel pump of the present invention, the piston fuel pump using the electric motor as the driving source is targeted, the variation in the fuel injection amount due to the fuel pressure fluctuation is suppressed, and the exhaust gas characteristics and drivability are prevented in advance. deterioration.

Description of drawings

FIG. 1 is a system configuration diagram showing a control device of a fuel pump according to the present invention.

FIG. 2 is a cross-sectional view showing details of the fuel pump.

3 is a flowchart showing a fuel pump control flow executed by the ECU according to the first embodiment.

4 is a flowchart showing a fuel pump control flow executed by the ECU according to the second embodiment.

Detailed ways

Next, an embodiment in which the present invention is embodied as a control device and a control method for a fuel pump mounted on an engine of a motorcycle will be described.

FIG. 1 is a system configuration diagram showing a control device of a fuel pump according to the present invention.

In FIG. 1 , the engine 1 is configured as a four-stroke single-cylinder gasoline engine with a displacement of 50 cc, and is mounted on a motorcycle as a driving power source. However, the specifications of the engine 1 are not limited to these, and can be arbitrarily changed.

A piston 4 is slidably arranged in a cylinder 3 formed in a cylinder block 2 of the engine 1 , the piston 4 is connected to a crankshaft 6 via a connecting rod 5 , and the crankshaft 6 rotates in conjunction with the reciprocating motion of the piston 4 . A flywheel 7 is attached to the rear end of the crankshaft 6 (the side of the not-shown transmission), and a magnetic resistance distribution head 7a for detecting the crank angle is formed at a predetermined position on the outer periphery of the flywheel 7 .

An intake port 9a and an exhaust port 9b are formed in the cylinder head 9 fixed to the cylinder block 2, and the spark plug 10 is arranged in a posture such that the front end faces the inside of the cylinder. In the intake passage 11 connected to the intake port 9a, an air cleaner 12, a throttle valve 13 that opens and closes based on a driver's throttle operation, and an injection for injecting fuel to the intake port 9a are provided from the upstream side. device 16. In addition, in the exhaust passage 17 connected to the exhaust port 9b, a three-way catalyst 18 for purifying exhaust gas and a muffler not shown are provided.

An intake valve 20 is arranged at the intake port 9a, and an exhaust valve 21 is arranged at the exhaust port 9b. The intake valve 20 and the exhaust valve 21 are pushed toward the valve closing side by the valve spring 22, and are opened by the intake camshaft 23 and the exhaust camshaft 24 that are rotationally driven in synchronization with the crankshaft 6 on the cylinder head 9. valve. As a result, the intake valve 20 and the exhaust valve 21 are opened and closed at predetermined timings synchronized with the reciprocating motion of the piston 4, and the combustion cycle of the engine 1 consisting of four strokes of intake, compression, expansion, and exhaust is performed every time The crank angle of 720°C was repeated.

The fuel (gasoline) stored in the fuel tank 25 is supplied to the injector 16 by the fuel pump 26 . The fuel pump 26 of the present embodiment is a type of piston-type fuel pump, and its structure and operating state will be described later, but it may be configured to use both a diaphragm and a piston to pressurize the fuel to predetermined requirements for the operation of the injector 16 . This fuel is pressurized and fed (hereinafter also referred to as a diaphragm/piston combined type). The fuel pump 26 is integrally formed with the injector 16 , and is connected to the fuel tank 25 via a supply hose 27 and a return hose 28 , respectively.

When the fuel pump 26 is operated, the fuel in the fuel tank 25 is guided into the fuel pump 26 via the supply hose 27, and is pressurized to a predetermined pressure, the pressurized fuel is supplied to the injector 16, and the remaining fuel is supplied via the fuel pump 26. The return hose 28 is recovered to the fuel tank 25 . Thereby, the fuel of a predetermined pressure is always supplied to the injector 16, and the fuel is injected into the intake port 9a at a predetermined injection timing and a predetermined injection amount in accordance with the valve opening of the injector 16.

When the engine 1 is operating, external air is drawn into the intake passage 11 via the air cleaner 12 by the negative pressure generated by the descending of the piston 4 during the intake stroke, and the intake air is drawn into the intake passage 11 based on the opening degree of the throttle valve 13 . After the flow rate of the air is adjusted, the air is mixed with the injected fuel from the injector 16 and flows into the cylinder of the engine 1 when the intake valve 20 is opened. After being compressed in the subsequent compression stroke, the air-fuel mixture is ignited by the spark plug 10 in the vicinity of the compression top dead center, burns in the expansion stroke, and imparts a rotational force to the crankshaft 6 via the piston 4 . In the subsequent exhaust stroke, the combusted exhaust gas is discharged from the cylinder when the exhaust valve 21 is opened, flows through the exhaust passage 17 , passes through the three-way catalyst 18 and the muffler, and is discharged to the outside.

The above-described combustion cycle of the engine 1 is executed under the control of the ECU 31 (engine control unit). Therefore, the input side of the ECU 31 is connected to various sensors such as an electromagnetic pickup 32 (electromagnetic pickup) which is arranged opposite to the above-mentioned flywheel 7 and outputs a signal synchronized with the magnetoresistive head 7a, The throttle sensor 33 of the opening degree of the throttle valve 13 is arranged in the exhaust passage 17 and changes the output stepwise based on the fluctuation of the exhaust air-fuel ratio centered on the stoichiometric (theoretical air-fuel ratio; theoretical air-fuel ratio) The O ₂ sensor 34, the water temperature sensor 35 that detects the cooling water temperature Tw of the engine 1, and the like. The output side of the ECU 31 is connected to various devices for driving the above-described injector 16 , the fuel pump 26 , the igniter 36 of the spark plug 10 , and the like.

The ECU 31 operates the engine 1 by executing various controls based on these sensor information: fuel injection control for driving the injector 16 , ignition timing control for driving the spark plug 10 , pump control for driving the fuel pump 26 , and the like .

For example, as the fuel injection control, the ECU 31 determines the target fuel injection amount in synchronization with the fuel cycle of the engine 1 based on the engine rotational speed Ne calculated using the signal of the electromagnetic sensor 32 and the throttle opening θth detected by the throttle sensor 33 , etc. The fuel injection is performed by driving the injector 16 at a predetermined timing of .

In addition, as ignition timing control, the ECU 31 determines the target ignition timing based on the engine rotational speed Ne, the throttle opening degree θth, etc., and, on the other hand, performs waveform shaping on the signal of the electromagnetic sensor 32 to generate a signal corresponding to the magnetoresistive distribution head 7a (in other words, the crank angle) synchronous rectangular wave-shaped crank angle signal. Then, the ECU 31 determines the timing corresponding to the target ignition timing based on the crank angle signal, and drives the igniter 36 to ignite the spark plug 10 .

In addition, the ECU 31 incorporates a drive circuit 31 a in order to drive an electric motor (a DC electric motor 42 to be described later) that is a drive source of the fuel pump 26 . Further, as pump control, the ECU 31 supplies a drive current from the drive circuit 31a to the electric motor to drive the fuel pump 26 when the engine 1 is running, and pressurizes the fuel pressurized to a predetermined pressure to the injector 16 (motor control unit).

However, as described above, the fuel pump 26 of the present embodiment is a diaphragm-piston type fuel pump, and thus measures to suppress variations in the fuel injection amount due to fuel pressure fluctuations are required. However, since an electric motor is used as the driving source, it is difficult to synchronize the driving of the fuel pump with the rotation of the engine as in the piston-type fuel pump described in Patent Document 1 using the electromagnetic coil as the driving source.

Therefore, in the present embodiment, the problem is solved by conversely making the rotation period of the electric motor different from the rotation period of the engine 1 . Hereinafter, although the details of the pump control will be described, first, the configuration of the fuel pump 26 will be described.

FIG. 2 is a cross-sectional view showing details of the fuel pump 26 .

The housing of the fuel pump 26 is constituted by a motor housing 41a, a pump housing 41b, and a regulator housing 41c, and a DC motor 42 (shown by a broken line) is housed in the motor housing 41a as a drive source. The cam 43 is fixed to the output shaft 42a of the DC motor 42, and when the cam 43 is rotated by the driving of the DC motor 42, the cam receiving member 44 reciprocates in the left-right direction (hereinafter referred to as the axis L direction) in the figure.

The center part of the diaphragm 46 is fixed to the cam receiving member 44, and the diaphragm chamber 47 is spaced apart between the motor case 41a and the pump case 41b by this diaphragm 46. As shown in FIG. Based on the reciprocating motion of the cam receiving member 44, the diaphragm 46 alternately reciprocates between the right side (hereinafter referred to as the suction side) and the left side (hereinafter referred to as the discharge side) in the figure. When the diaphragm 46 moves to the suction side, the fuel from the fuel tank 25 flows into the diaphragm chamber 47 via the supply hose 27 and the supply passage 50 . In addition, when the diaphragm 46 moves to the discharge side, the fuel in the diaphragm chamber 47 is recovered to the fuel tank 25 side via the return passage 52 and the return hose 28, and the reciprocation of the diaphragm 46 is repeated every time Such fuel delivery.

A piston 56 is slidably arranged in the direction of the axis L in the sleeve 55 fitted and fixed to the pump housing 41b. The piston 56 is connected to the cam receiving member 44, and the piston 56 is synchronized with the reciprocating motion of the diaphragm 46. It reciprocates between the suction side and the discharge side. When the piston 56 moves to the suction side, a part of the fuel in the diaphragm chamber 47 flows into the piston 56 through the suction port 56 a and further flows into the pressurizing chamber 57 through the check valve 58 . When the piston 56 moves to the discharge side after that, the fuel in the pressurizing chamber 57 is pressurized, and this fuel pressurization is repeated every time the piston 56 reciprocates.

The fuel pressurized in the pressurizing chamber 57 by the reciprocating motion of the piston 56 is supplied to the pressure adjusting mechanism 59 provided in the regulator housing 41 c via the check valve 60 , and the pressure adjusting mechanism 59 is adjusted to a set pressure. The excess fuel generated by the pressure adjustment is discharged to a relief valve 69 and recovered to the fuel tank 25 side together with the excess fuel from the diaphragm chamber 47 . Then, the fuel pressure-adjusted by the pressure adjustment mechanism 59 is pressure-fed to the above-mentioned injector 16 (shown in FIG. 1 ) from the pressure adjustment chamber 66 via the injector passage 68 , and is directed toward the engine as the valve of the injector 16 is opened. 1 is injected into the intake port 9a.

As described above, the fuel pump 26 of the present embodiment reciprocates the piston 56 to pressurize the fuel, and therefore cannot avoid fluctuations in the fuel pressure. On the other hand, since the DC motor 42 is used as the driving source, it cannot be applied The technology of Patent Document 1.

In consideration of the above-mentioned problems and the characteristics of the fuel pump 26 , the inventors of the present invention focused on the following points.

First, the fuel pressurized by the piston 56 and pressure adjusted by the pressure adjustment mechanism 59 is supplied to the injector 16 via the injector passage 68 , except for the pressure feeding timing at which the piston 56 pressurizes the fuel (hereinafter referred to as the fuel The fuel pressure in the passage from the injector passage 68 to the injector 16 is always maintained at a stable set pressure (for example, about 300 kPa). Therefore, if the fuel injection timing does not overlap with the fuel injection timing of each combustion cycle, since the fuel injection is always performed at the fuel pressure of the stable set pressure, it is possible to eliminate the influence of the fuel injection amount due to the fluctuation of the fuel pressure. influences.

On the other hand, when, for example, the DC motor 42 of the fuel pump 26 is driven at a predetermined rotational speed Nm, the fuel injection timing changes based on the operating range of the engine 1, resulting in a combustion cycle that occasionally overlaps the fuel injection timing. At this time, if the period of fuel injection (in other words, the rotation period Teg of the engine 1 to be described later, which is also related to the fuel injection timing TMinj) and the period of fuel pressure feeding (in other words, the rotation period Tmo of the DC motor 42 to be described later) , which is also related to the fuel injection timing TMpump), as long as the engine 1 stays in this operating region, a fuel cycle in which the fuel injection timing and the fuel injection timing overlap will be continuously generated. Therefore, while the above phenomenon occurs, the combustion of the engine 1 becomes unstable due to the variation in the fuel injection amount, and the operation state in which the target A/F cannot be achieved continues to be maintained, which is a major cause of deterioration of exhaust gas characteristics and drivability.

The cause of the problem that the fuel injection timing and the fuel pressure feed timing overlap is not limited to the case where the periods of the two are the same, and the same problem occurs when either period corresponds to a multiple of the other period. For example, when the cycle of the fuel injection is twice the cycle of the fuel pressure injection, as in the case of the above-mentioned coincidence, the fuel pressure injection timing and the fuel injection timing overlap continuously in each combustion cycle. Conversely, when the period of fuel pressure feeding is twice the period of fuel injection, the timing of fuel pressure feeding and the fuel injection timing overlap every other combustion cycle. Changes do not unwind, so it does become a problem.

On the other hand, even if the fuel injection timing and the fuel pressure delivery timing overlap in a certain combustion cycle, either one of the fuel injection period and the fuel pressure delivery period does not correspond to a multiple of the other (the If the periods do not match and are not in a multiple relationship of 2 or more), the timings of the two do not necessarily overlap in the next combustion cycle. That is, since the operating state in which the combustion of the engine 1 is unstable due to the variation in the fuel injection amount is limited to the instant of one combustion cycle, it is virtually impossible to cause deterioration of exhaust gas characteristics and drivability. Therefore, the overlapping of the fuel injection timing and the pressure feed timing in the above-described one combustion cycle can be considered to be within the allowable range.

Based on the above findings, the inventors of the present invention have come to the conclusion that if the rotation period of the DC motor 42 is controlled so that the rotation period of the engine 1 is always different from the rotation period of the engine 1, the difference between the fuel injection timing and the fuel pressure feeding timing in each combustion cycle The relationship changes, and although the timings of the two may occasionally overlap in one combustion cycle, it is possible to prevent the problem from overlapping in successive combustion cycles. Hereinafter, two methods will be sequentially described as the first embodiment and the second embodiment.

first embodiment

In the present embodiment, the rotation period of the engine 1 is monitored and compared with the rotation period of the DC motor 42 , and when the two periods are close, the rotation period of the DC motor 42 is controlled in a direction away from the rotation period of the engine 1 . Therefore, the ECU 31 executes the pump control flow shown in FIG. 3 at predetermined control intervals while the engine 1 is operating.

First, in step S1, a signal from the electromagnetic sensor 32 is acquired, and based on the signal, the engine rotation period Teg is calculated in step S2 (engine rotation period calculation means). The engine rotation period Teg referred to here represents the period of fuel injection. In the present embodiment, since the four-stroke single-cylinder gasoline engine 1 is used, the period of fuel injection is repeated every time the engine 1 rotates twice (720° C. A). It is treated as the engine rotation period Teg.

In the subsequent step S3, it is determined whether or not the engine rotation period Teg and the motor rotation period Tmt are different based on the following formula (1) (determination means, period determination step). The motor rotation period Tmt represents the period during which the piston 56 of the fuel pump 26 performs fuel pressure feeding, and as described above, the cycle of repeated fuel pressure feeding every time the DC motor 42 rotates once is treated as the motor rotation period Tmt. The ECU 31 supplies a drive current to the DC motor 42 via the drive circuit 31a in order to function as a motor control unit, and therefore calculates the rotation period of the DC motor 42 based on the duty ratio of the drive current and the like (motor rotation period calculation means).

|Engine rotation period Teg－motor rotation period Tmt|≦determination value ΔT...(1)

Due to various factors, such as control errors of the engine 1 and the DC motor 42, detection errors of the electromagnetic sensor 32, etc., or the increase or decrease of the engine rotation speed Ne between the control cycles of the ECU 31, even the engine rotation period Teg and the motor rotation period Tmt If they are not completely consistent, the timings of the two may overlap. Therefore, not only when the rotation periods Teg and Tmt of the two are completely identical, but also when the rotation periods Teg and Tmt are close to a certain degree (hereinafter, referred to as "the case where the two are close"), in order to make the two The control is performed in the direction in which the rotation periods Teg and Tmt of the other are away from each other, and the determination value ΔT is set in advance as a threshold value.

In addition, in the above-mentioned formula (1), only the case where the engine rotation period Teg and the motor rotation period Tmt coincide is assumed, and the case where the periods of the two are in a multiple relationship is not assumed. The reason is that in the specifications of the engine 1 and the fuel pump 26 according to the present embodiment, the cycles of the two cannot be in a multiple relationship in any operation region. It is a matter of course, but in the specification that the period of the two can be in a multiple relationship, it is only necessary to change the formula to take this content into consideration.

When the determination of step S3 is NO (NO), the process proceeds to step S4, and the duty ratio of the drive current supplied to the DC motor 42 is calculated by a normal method. For example, the duty ratio is calculated as an appropriate value for reducing the power consumption while suppressing the rotational speed Nm of the DC motor 42 and for discharging a fuel amount sufficient to satisfy the target injection amount from the injector 16 from the fuel pump 26 at this time.

Specifically, the reference value of the duty ratio is calculated based on the operating region of the engine 1, for example, the engine rotational speed Ne and the throttle opening θth (engine load), and is corrected by a correction coefficient corresponding to the cooling water temperature Tw and the battery voltage Vbtt This reference value is used to calculate the final duty cycle. However, the calculation process of the duty ratio is not limited to this. For example, a predetermined fixed value may be applied as the duty ratio regardless of the operating range of the engine 1 . The duty ratio is thus calculated, and in subsequent step S5 , after the drive current flowing into the DC motor 42 is controlled based on the duty ratio, the flow ends.

On the other hand, when the engine rotation period Teg is close to the motor rotation period Tmt and the determination is YES (YES) in step S3 described above, the process proceeds to step S6, and the duty ratio of the drive current flowing into the DC motor 42 is increased by a preset value Correction is performed so that the predetermined value may be fixed or the predetermined value set in advance may be decreased (motor speed change command means, rotation speed change process), and the process proceeds to the above-mentioned step S5. The value to be corrected is the duty ratio when the motor rotation period Tmt suitable for the calculation process of the above-mentioned formula (1) is realized. Increase or decrease accordingly, away from the engine rotation period Teg.

From the above description, it can be seen that the purpose of the processing of step S6 is to increase or decrease the motor rotation speed Nm by adjusting the power supply to the DC motor 42, thereby further increasing or decreasing the motor rotation period Tmo. Therefore, this method is not limited to correcting the duty ratio as described above, and various changes can be made. For example, the power supply to the DC motor 42 can be adjusted by simultaneously correcting the PWM period and the duty ratio of the drive current. .

In addition, the correction direction of the duty ratio in the above-mentioned step S6 can be corrected to the increasing side or the decreasing side when the fuel amount discharged from the fuel pump 26 has a margin relative to the target injection amount. Make corrections. However, in step S3, when the duty ratio is set corresponding to the minimum required combustion amount for satisfying the target injection amount, if the duty ratio is corrected to the decreasing side, the motor rotation speed Nm decreases and there is a possibility that the It becomes impossible to achieve the target injection amount. Therefore, in this case, it is only necessary to correct the duty ratio to the increasing side, whereby the correct fuel injection amount can be maintained.

By the processing of the ECU 31 described above, when the engine rotation period Teg is different from the motor rotation period Tmt, the drive current flowing into the DC motor 42 is controlled by the duty ratio corresponding to the operating range of the engine 1 as usual, and the other On the other hand, if the engine rotation period Teg is close to the motor rotation period Tmt, the motor rotation speed Nm is increased or decreased by correcting the duty ratio (or the PWM period and the duty ratio) so that the motor rotation period Tmo is farther away from the engine rotation period Teg.

As a result, according to the control device for the fuel pump 26 of the present embodiment, the motor rotation period Tmt and the engine rotation period Teg are always made different during the operation of the engine 1, so that the fuel injection timing and the fuel pressure feeding can be adjusted for each combustion cycle. Timing relationship changes. Therefore, even if the fuel injection timing and the fuel pressure feed timing occasionally overlap in a certain combustion cycle, in the next combustion cycle, the timings of the two do not necessarily overlap. Therefore, the operation state in which the combustion of the engine 1 is unstable due to the variation in the fuel injection amount ends in the instant of one combustion cycle. Therefore, a diaphragm-piston fuel pump using the DC motor 42 as a driving source is used. 26, it is possible to prevent the deterioration of exhaust gas characteristics and drivability due to variations in the fuel injection amount in advance.

Second Embodiment

Next, a second embodiment embodying the present invention will be described. The hardware configuration of the present embodiment is the same as that of the first embodiment, and the difference lies in the processing content of the ECU 31 . Specifically, in the first embodiment, the duty ratio setting process (step S4 in FIG. 3 ) is switched according to the comparison result between the engine rotation period Teg and the motor rotation period Tmt, but in this embodiment, according to the The fuel injection timing of the piston 56 is determined by the change in the drive current value to the DC motor 42 , and the duty ratio setting process is switched according to the comparison result between the fuel injection timing and the fuel injection timing of the engine 1 . Therefore, in the following description, the distinguishing point concerning the process of ECU31 is mainly described.

First, in order to detect the drive current value supplied from the drive circuit 31a to the DC motor 42, the ECU 31 of the present embodiment includes a current detection circuit 31b shown by a dotted line in FIG. The detection result of the fuel pressure feed timing of the piston 56 is determined (fuel pressure feed timing determination means).

In the pump control flow shown in FIG. 4, the ECU 31 first reads the driving current value of the DC motor 42 in step S11, and according to the change of the driving current value, in step S12, determines the current combustion cycle of the piston 56. Timing of fuel pressure delivery. Since the drive current value of the DC motor 42 has a characteristic of rapidly increasing at the timing at which the fuel is pressurized by the piston 56 , the timing at which the value of the driving current changes in the increasing direction is regarded as the fuel pressurization timing TMPump.

In the subsequent step S13, it is determined whether or not the fuel injection timing TMinj of the injector 16 is different from the fuel pressure feeding timing TMpump based on the following equation (2) (determination means, cycle determination process). In the fuel injection control, since the ECU 31 itself controls the drive of the injector 16, the drive timing is regarded as the fuel injection timing TMinj (fuel injection timing determination means).

|Fuel injection timing TMinj－Fuel pressure feeding timing TMPump|≦determination value ΔTM......(2)

The judgment value ΔTM has the same meaning as the judgment value ΔT of the formula (1), not only when the fuel injection timing TMinj and the fuel pressure feeding timing TMpump are completely identical, but also when the two are close to a certain degree (hereinafter, the expression In the case where the two are "close"), the determination value ΔTM is set in advance.

When the determination of step S13 is NO (NO), in step S14, the duty ratio of the drive current supplied to the DC motor 42 is calculated according to the operating range of the engine 1 by a normal method. In addition, when the determination of the above-mentioned step S13 is YES, in step S16, the duty ratio (or the PWM period and the duty ratio) of the drive current flowing into the DC motor 42 is corrected by increasing or decreasing ( Motor speed change command means, rotation speed change process), and then in step S15, the drive current flowing into the DC motor 42 is controlled.

By the processing of the ECU 31 described above, when the fuel injection timing TMinj is different from the fuel pressure feeding timing TMpump, the drive current flowing into the DC motor 42 is controlled by the duty ratio corresponding to the operating range of the engine 1 as usual, and the On the other hand, when the fuel injection timing TMinj is close to the fuel pressure feeding timing TMpump, the electric motor rotational speed Nm is increased or decreased by correcting the duty ratio. The increase or decrease in the motor rotation speed Nm means that the motor rotation period Tmo is moved away from the engine rotation period Teg, and the fuel injection timing TMPump is also moved away from the fuel injection timing TMinj.

As a result, the same functions and effects as those of the first embodiment can be obtained, and although the description will not be repeated, when the engine 1 is operating, the motor rotation period Tmt and the engine rotation period Teg are always made different, so that each combustion cycle can be used. The relationship between the fuel injection timing TMinj and the fuel injection timing TMPump changes. Therefore, by using the diaphragm-piston fuel pump 26 using the DC motor 42 as a drive source, it is possible to prevent deterioration of exhaust gas characteristics and drivability due to variations in the fuel injection amount in advance.

In addition, the form of this invention is not limited only to the above-mentioned embodiment. For example, in the above-described embodiments, the present invention is specifically described as a control device for the fuel pump 26 mounted on the engine 1 of a motorcycle, but the object to be mounted on the engine 1 is not limited to this. For example, the present invention can be embodied as a control device and a control method for a fuel pump mounted on an engine of a tricycle or a generator.

In addition, in the above-mentioned embodiment, the diaphragm-piston type fuel pump 26 is applied to the present invention, but the form of the fuel pump 26 is not limited to this. For example, the present invention can also be applied to a piston-type fuel pump that does not have the diaphragm 46 and uses only the piston 56 to pressurize and supply fuel.

Label description

1 engine

16 injectors

26 Fuel pump

31 ECU (determination unit, motor speed change command unit, engine rotation cycle calculation unit, motor rotation cycle calculation unit, fuel injection timing determination unit)

31a Drive circuit (motor control unit)

31b Current detection circuit (fuel pressure feeding timing determination unit)

42 DC motors

46 Diaphragm

56 Pistons

Claims (5)

1. A control device for a fuel pump, comprising: A piston-type fuel pump, which uses the drive of an electric motor to reciprocate the piston, and pressurizes the fuel pressurized to a predetermined pressure; an injector that injects fuel pressurized from the fuel pump in synchronism with the combustion cycle of the engine; a motor control unit that provides drive current to the motor and controls the motor; a determination unit that executes a determination process of determining whether either one of the fuel injection period of the injector and the fuel pressure feeding period of the piston corresponds to an integral multiple of the other; and a motor speed change command unit that, when it is determined by the determination unit that either one of the fuel injection cycle of the injector and the fuel pressure feeding cycle of the piston corresponds to an integral multiple of the other, The motor control unit is caused to change the rotational speed of the motor. 2. The control device of the fuel pump according to claim 1, characterized in that, further comprising: an engine rotation period calculation unit that calculates a rotation period of the engine; and a motor rotation period calculation unit, the motor rotation period calculation unit calculates the rotation period of the motor, The determination unit compares the rotation period of the engine calculated by the engine rotation period calculation unit with the rotation period of the electric motor calculated by the motor rotation period calculation unit, thereby executing whether the two are different. Judgment processing. 3. The control device of the fuel pump according to claim 1, characterized in that, further comprising: a fuel injection timing determination unit that determines the fuel injection timing of the injector; and a fuel pressure feed timing determination unit that determines the fuel pressure feed timing of the piston based on a change in the value of the drive current supplied to the electric motor by the motor control unit, The determination unit compares the fuel injection timing of the injector determined by the fuel injection timing determination unit with the fuel pressure injection timing of the piston determined by the fuel injection timing determination unit, thereby executing Whether the two are different is the judgment process. 4. The control device for a fuel pump according to any one of claims 1 to 3, characterized in that: The fuel pump is configured such that a diaphragm is reciprocated by the drive of the electric motor, and a piston is reciprocated in synchronization with the reciprocating motion of the diaphragm, and the fuel is fed from the diaphragm by the piston. pressure and pressure to the injector. 5. A method for controlling a fuel pump, comprising: A cycle determination step in which fuel is injected from the fuel pump in synchronization with a fuel pumping cycle of a piston-type fuel pump that reciprocates a piston by driving a motor to pressurize fuel, and a combustion cycle of an engine. Comparing the fuel injection periods of the injectors of the pressure-fed fuel to determine whether either the fuel injection period or the fuel injection period corresponds to an integer multiple of the other; and A rotational speed changing step of changing the rotational speed of the electric motor when it is determined by the cycle determination step that either the fuel pressure feeding cycle or the fuel injection cycle corresponds to an integral multiple of the other.

Images