CN107614854B

CN107614854B - Fuel pump control device and control method

Info

Publication number: CN107614854B
Application number: CN201680033355.8A
Authority: CN
Inventors: 马场悠一; 三浦磨
Original assignee: Mikuni Corp
Current assignee: Mikuni Corp
Priority date: 2015-06-08
Filing date: 2016-05-23
Publication date: 2020-11-17
Anticipated expiration: 2036-05-23
Also published as: WO2016199570A1; JP2017002770A; JP6545006B2; EP3306061A1; CN107614854A; EP3306061A4

Abstract

The piston (56) is reciprocated by the drive of the DC motor (42), and the pressurized fuel is pressure-fed to the injector (16) and ejected 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 when the engine rotation period (Teg) and the motor rotation period (Tmt) are different, the duty ratio of the drive current of the DC motor (42) is calculated according to the operation region of the engine (1) by a normal method (S4), and when the engine rotation period (Teg) and the motor rotation period (Tmt) are close to each other, the duty ratio of the drive current flowing into the DC motor (42) is corrected to be increased by a predetermined value or decreased by a predetermined value (S6), and the DC motor (42) is controlled to be driven according to the corrected duty ratio (S5). Thus, when the engine (1) is operated, the motor rotation period (Tmt) and the engine rotation period (Teg) are always different.

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 a fuel pump, and more particularly to a control device for a piston type fuel pump and a control method for a piston type fuel pump that reciprocates a piston using an electric motor as a drive source and pressure-feeds fuel pressurized to a predetermined pressure to an injector of an engine.

Background

Conventionally, fuel injection devices that electronically control fuel supply to an engine have been widely used for the purpose of improving exhaust gas characteristics, fuel efficiency, and the like, and the related objects include not only four-wheel vehicles but also various two-wheel vehicles, power generators, and the like. Such a fuel injection device is configured to pump up fuel in a fuel tank by a fuel pump, pressurize the fuel to a predetermined pressure, supply the pressurized fuel to an injector provided in an intake pipe of an engine, and inject the fuel into the intake pipe by opening and closing the injector in synchronization with a combustion cycle of the engine.

As such a fuel pump, for example, in an engine having a small displacement used in a two-wheeled vehicle, a generator, or the like, it is required not only to miniaturize the fuel pump body but also to reduce power consumption required for driving the pump.

The piston fuel pump is slidably disposed in the cylinder, biased in one direction by a return spring, and driven in the opposite direction by excitation of the electromagnetic coil. The piston reciprocates based on the periodic excitation of the electromagnetic coil, and accordingly, fuel is pressurized in the cylinder to be intermittently discharged. 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 varies due to the fluctuation of the fuel pressure, and the combustion of the engine becomes unstable, which causes a problem of deterioration in the exhaust gas characteristics and drivability.

Therefore, for example, in the piston type fuel pump described in patent document 1, a problem is solved 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 for the fuel injection time Tout from the fuel injection start time t2 in synchronization with the rotation of the engine, while the timing earlier than the fuel injection start time t2 by the predetermined time Tf is determined as the fuel pump drive start time t1, and the fuel pump is driven (the electromagnetic coil is excited) from the fuel pump drive start time t1 throughout the fuel pump drive time Tpump. As a result, by constantly performing fuel injection at the timing at which the fuel pressure rises due to the driving of the fuel pump, it is possible to suppress the variation in the fuel injection amount due to the variation in the fuel pressure.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2004-52596

Disclosure of Invention

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 as the drive source can be freely changed for each combustion cycle of the engine, the drive timing of the fuel pump can be controlled as described above while following the fuel injection timing that changes in time depending on the operating region of the engine. However, in the piston-type fuel pump using the electric motor as the drive source, the rotation speed of the electric motor needs to be changed in order to change the drive timing, and it is practically difficult to quickly change the rotation speed of the electric motor in accordance with the fuel injection timing. 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 measures for solving the problem have been desired.

The present invention has been made to solve the above-described problems, and an object thereof is to provide a control device and a control method for a fuel pump, which control a piston type fuel pump using an electric motor as a drive source, and suppress variation in fuel injection amount due to fuel pressure variation, thereby preventing deterioration of exhaust gas characteristics and drivability in advance.

Technical scheme for solving technical problem

In order to achieve the above object, a control device for a fuel pump according to the present invention includes: a piston-type fuel pump that reciprocates a piston by driving of a motor and pressure-feeds fuel pressurized to a predetermined pressure; an injector that injects fuel pressure-fed from a fuel pump in synchronization with a combustion cycle of the engine; a motor control unit that supplies a drive current to the motor and controls the motor; a determination unit that executes a determination output for determining whether one of a fuel injection period of the injector and a fuel pressure-feed period of the piston corresponds to a multiple of the other; and a motor speed change command unit that causes the motor control unit to change the rotation speed of the motor when the determination unit determines that either one of the fuel injection period of the injector and the fuel pressure-feed period of the piston corresponds to a multiple of the other.

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

In another aspect, the present invention preferably further comprises: an engine rotation period calculation unit that calculates a rotation period of the engine; and a motor rotation period calculation unit that calculates a rotation period of the motor, and the determination unit performs the determination process by comparing the rotation period of the engine calculated by the engine rotation period calculation unit with the rotation period of the motor calculated by the motor rotation period calculation unit.

In the case of the above configuration, the rotation speed of the electric motor is changed according to the result of determination by comparing the rotation cycle of the engine with the rotation cycle of the electric motor.

In another aspect, the present invention preferably further comprises: a fuel injection timing determining unit that determines a fuel injection timing of the injector; and a fuel pressure feed timing determination unit that determines a fuel pressure feed timing of the piston based on a change in a drive current value supplied to the motor by the motor control unit, wherein the determination unit performs the determination process by comparing the fuel injection timing of the injector determined by the fuel injection timing determination unit with the fuel pressure feed timing of the piston determined by the fuel pressure feed timing determination unit.

In the case of the above configuration, the fuel pressure feed timing of the piston is determined based on a change in the drive current value of the motor, and the rotation speed of the motor is changed based on a determination result obtained by comparing the fuel pressure feed timing with the fuel injection timing of the injector.

In another aspect, the fuel pump is preferably configured to reciprocate the diaphragm by driving of the motor, reciprocate the piston in synchronization with the reciprocation of the diaphragm, and pressurize the fuel sent from the diaphragm by the piston and pressure-feed the fuel to the injector.

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

Further, a method for controlling a fuel pump according to the present invention includes: a cycle determination step of comparing a fuel pressure-feed cycle of a piston-type fuel pump that reciprocates a piston by driving of an electric motor and pressure-feeds fuel with a fuel injection cycle of an injector that injects fuel pressure-fed from the fuel pump in synchronization with a combustion cycle of an engine, and determining whether one of the fuel pressure-feed cycle and the fuel injection cycle corresponds to a multiple of the other; and a rotation speed changing step of changing the rotation speed of the electric motor when it is determined by the period determining step that either one of the fuel pressure-feeding period and the fuel injection period corresponds to a multiple of the other.

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

Effects of the invention

According to the control device and control method for the fuel pump of the present invention, the piston type fuel pump using the electric motor as the drive source is used, and the variation of the fuel injection amount due to the fuel pressure variation is suppressed, thereby preventing the deterioration of the exhaust gas characteristics and the drivability in advance.

Drawings

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

Fig. 2 is a sectional view showing details of the fuel pump.

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

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

Detailed Description

Next, an embodiment of the present invention will be described, specifically, as a control device and a control method for a fuel pump mounted on an engine of a two-wheeled vehicle.

In fig. 1, an engine 1 is a four-stroke single-cylinder gasoline engine having an exhaust gas volume of 50cc and is mounted on a two-wheeled vehicle as a power source for running. However, the specification of the engine 1 is not limited to this, and can be arbitrarily changed.

A piston 4 is slidably disposed 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 reciprocation of the piston 4. A flywheel 7 is attached to a rear end (a transmission side not shown) of the crankshaft 6, and a magnetic resistance distribution head 7a for detecting a crank angle is formed at a predetermined position on an outer periphery of the flywheel 7.

A cylinder head 9 fixed to the cylinder block 2 is formed with an intake port 9a and an exhaust port 9b, and an ignition plug 10 is disposed in a posture in which a tip end faces the inside of the cylinder. An intake passage 11 connected to the intake port 9a is provided with, from the upstream side, an air cleaner 12, a throttle valve 13 that opens and closes based on a throttle operation by a driver, and an injector 16 that injects fuel into the intake port 9 a. Further, a three-way catalyst 18 for purifying exhaust gas and a muffler, not shown, are provided in the exhaust passage 17 connected to the exhaust port 9 b.

An intake valve 20 is disposed at the intake port 9a, and an exhaust valve 21 is disposed at the exhaust port 9 b. The intake valve 20 and the exhaust valve 21 are urged toward the closed side by a valve spring 22, and are opened by an intake camshaft 23 and an exhaust camshaft 24 that are rotationally driven in synchronization with the crankshaft 6 in the cylinder head 9. Accordingly, the intake valve 20 and the exhaust valve 21 are opened and closed at predetermined timings synchronized with the reciprocation of the piston 4, and the combustion cycle of the engine 1, which is composed of four strokes of intake, compression, expansion, and exhaust, is repeated at crank angles of 720 ° a.

The fuel (gasoline) stored in a fuel tank 25 is supplied to the injector 16 by a fuel pump 26. The fuel pump 26 of the present embodiment is one of piston-type fuel pumps, and its structure and operation state will be described later, but may be configured to pressurize fuel to a predetermined pressure necessary for the operation of the injector 16 by using both a diaphragm and a piston (hereinafter, also referred to as a diaphragm/piston dual-purpose type). The fuel pump 26 is formed integrally 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 introduced into the fuel pump 26 through the supply hose 27 and pressurized to a predetermined pressure, the pressurized fuel is supplied to the injector 16, and the remaining fuel is recovered to the fuel tank 25 through the return hose 28. As a result, the injector 16 is always supplied with fuel at a predetermined pressure, and the fuel is injected into the intake port 9a at a predetermined injection timing and a predetermined injection amount in response to the valve opening of the injector 16.

When the engine 1 is operated, the outside air is taken into the intake passage 11 through the air cleaner 12 by the negative pressure generated as the piston 4 descends during the intake stroke, the flow rate of the taken-in air is adjusted based on the opening degree of the throttle valve 13, and then the taken-in air is mixed with the fuel injected from the injector 16 and flows into the cylinder of the engine 1 when the intake valve 20 is opened. After compression in the subsequent compression stroke, the mixture gas is ignited by the ignition plug 10 in the vicinity of the compression top dead center, is burned in the expansion stroke, and gives a rotational force to the crankshaft 6 via the piston 4. In the subsequent exhaust stroke, the burned 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 combustion cycle of the engine 1 described above is executed according to control by the ECU31 (engine control unit). Therefore, various sensors are connected to the input side of the ECU31 as follows: that is, an electromagnetic sensor 32(electromagnetic pick-up) which is disposed to face the flywheel 7 and outputs a signal in synchronization with the magnetoresistive head 7a, a throttle sensor 33 which detects the opening degree of the throttle valve 13, and an O-sensor which is disposed in the exhaust passage 17 and whose output is varied stepwise based on the variation of the exhaust air-fuel ratio centered around the stoichiometric air-fuel ratio₂A sensor 34, a water temperature sensor 35 that detects the cooling water temperature Tw of the engine 1, and the like. Various devices for driving the injector 16, the fuel pump 26, the igniter 36 of the ignition plug 10, and the like are connected to the output side of the ECU 31.

The ECU31 executes various controls to operate the engine 1 based on these sensor information as follows: namely, fuel injection control for driving the injector 16, ignition timing control for driving the ignition plug 10, and pump control for driving the fuel pump 26, and the like.

For example, as the fuel injection control, the ECU31 determines a target fuel injection amount based on the engine rotation speed Ne calculated from the signal of the electromagnetic sensor 32, the throttle opening θ th detected by the throttle sensor 33, and the like, and drives the injector 16 at a predetermined timing in synchronization with the fuel cycle of the engine 1 to perform fuel injection.

As the ignition timing control, the ECU31 determines a target ignition timing based on the engine speed Ne, the throttle opening θ th, and the like, and generates a rectangular wave crank angle signal synchronized with the magnetoresistive head 7a (in other words, the crank angle) by waveform-shaping the signal of the electromagnetic sensor 32. Then, the ECU31 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.

The ECU31 incorporates a drive circuit 31a for driving a motor (a DC motor 42 described later) as a drive source of the fuel pump 26. As the pump control, the ECU31 supplies a drive current from the drive circuit 31a to the motor to drive the fuel pump 26 when the engine 1 is operating, and pressure-feeds the fuel pressurized to a predetermined pressure to the injector 16 (motor control means).

However, since the fuel pump 26 of the present embodiment is a diaphragm/piston dual-purpose fuel pump as described above, a measure for suppressing variation in the fuel injection amount due to variation in the fuel pressure is required. However, since the electric motor is used as the drive 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 which uses the electromagnetic coil as the drive source.

Therefore, in the present embodiment, the problem is solved by making the rotation cycle of the motor different from the rotation cycle of the engine 1. Next, the pump control will be described in detail, but the structure of the fuel pump 26 will be described first.

Fig. 2 is a sectional view showing details of the fuel pump 26.

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

A center portion of a diaphragm 46 is fixed to the cam receiving member 44, and a diaphragm chamber 47 is partitioned between the motor housing 41a and the pump housing 41b by the diaphragm 46. The diaphragm 46 alternately reciprocates between the right side (hereinafter referred to as suction side) and the left side (hereinafter referred to as discharge side) in the drawing based on the reciprocation of the cam receiving member 44. When the diaphragm 46 moves to the suction side, fuel from the fuel tank 25 flows into the diaphragm chamber 47 through the supply hose 27 and the supply passage 50. When the diaphragm 46 moves to the discharge side, the fuel in the diaphragm chamber 47 is collected to the fuel tank 25 side via the return passage 52 and the return hose 28, and such fuel transfer is repeated for each reciprocation of the diaphragm 46.

A piston 56 is slidably disposed in the sleeve 55 fitted and fixed to the pump housing 41b in the direction of the axis L, the piston 56 is connected to the cam receiving member 44, and the piston 56 reciprocates between the suction side and the discharge side in synchronization with the reciprocation of the diaphragm 46. When the piston 56 moves to the intake side, a part of the fuel in the diaphragm chamber 47 flows into the piston 56 through the intake port 56a and further flows into the pressurizing chamber 57 through the check valve 58. When the piston 56 moves to the discharge side later, the fuel in the pressurizing chamber 57 is pressurized, and such fuel pressurization is repeated every time the piston 56 reciprocates.

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

As described above, the fuel pump 26 of the present embodiment pressurizes the fuel by reciprocating the piston 56, and therefore, fluctuation of the fuel pressure cannot be avoided, but the technique of patent document 1 cannot be applied because the DC motor 42 is used as the drive source.

In consideration of the above-described problems and the characteristics of the fuel pump 26, the inventors of the present invention have 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 through the injector passage 68, but the fuel pressure in the passage from the injector passage 68 to the injector 16 is always kept at a stable set pressure (for example, about 300 kPa) except for the pressure feed timing (hereinafter, referred to as fuel pressure feed timing) at which the fuel is pressure-fed by the piston 56. Therefore, if the fuel pressure feed timing is not overlapped with the fuel injection timing of each combustion cycle, the fuel injection is always performed at a fuel pressure of a stable set pressure, and therefore, the influence of the fuel pressure variation on the fuel injection amount can be eliminated.

On the other hand, for example, when the DC motor 42 of the fuel pump 26 is driven at a predetermined rotation speed Nm, the fuel injection timing changes depending on the operation region of the engine 1, and a combustion cycle occasionally overlapping the fuel pressure feed timing is generated. At this time, if the period of fuel injection (in other words, the rotation period Teg of the engine 1 described later and also the fuel injection timing TMinj) matches the period of fuel pressure-feeding (in other words, the rotation period Tmo of the DC motor 42 described later and also the fuel pressure-feeding timing TMpump), a fuel cycle in which the fuel pressure-feeding timing and the fuel injection timing overlap each other is continuously generated as long as the engine 1 stays in the operating region. 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 is continuously maintained, which becomes a factor causing deterioration in the exhaust gas characteristics and drivability.

The reason why the fuel injection timing and the fuel pressure-feeding timing overlap is not limited to the case where the periods of both are identical, but the same problem occurs if one of the periods corresponds to a multiple of the other period. For example, when the period of fuel injection is 2 times the period of fuel pressure-feed, the fuel pressure-feed timing and the fuel injection timing are continuously overlapped with each other in each combustion cycle, as in the case of the above-described matching. On the other hand, when the period of the pressure-feeding of the fuel is 2 times the period of the fuel injection, the overlap of the fuel pressure-feeding timing and the fuel injection timing occurs every other combustion cycle, but this does not occur unless the operation region of the engine 1 is changed, and therefore, this is a problem.

On the other hand, even if the fuel injection timing and the fuel pressure-feeding timing overlap each other in a certain combustion cycle, in the case where either one of the period of fuel injection and the period of fuel pressure-feeding is not equal to a multiple of the other (the periods of both do not match each other, and are not in a multiple relationship of 2 or more), it is not necessary that the timings of both overlap each other in the next combustion cycle. That is, 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 moment of 1 combustion cycle, and therefore, it is substantially impossible to become a factor that deteriorates the exhaust gas characteristics and drivability. Therefore, the case where the overlap of the fuel injection timing and the pressure-feed timing occurs within 1 combustion cycle described above can be regarded as being within an allowable range.

Based on the above findings, the inventors of the present invention reached the following conclusions: if the rotation period of the DC motor 42 is controlled so as to be always different from the rotation period of the engine 1, the relationship between the fuel injection timing and the fuel pressure feed timing changes in each combustion cycle, and the timings of both may occasionally overlap each other in 1 combustion cycle, but it is possible to prevent the occurrence of overlapping in consecutive combustion cycles, which may be a problem. Next, two methods will be described in order as the first embodiment and the second embodiment.

First embodiment

In the present embodiment, the rotation cycle of the engine 1 is monitored and compared with the rotation cycle of the DC motor 42, and when the two cycles are close to each other, the rotation cycle of the DC motor 42 is controlled in a direction away from the rotation cycle of the engine 1. Therefore, the ECU31 executes the pump control flow shown in fig. 3 at predetermined control intervals during the operation of the engine 1.

First, in step S1, a signal from the electromagnetic sensor 32 is acquired, and based on the signal, an engine rotation period Teg (engine rotation period calculation means) is calculated in step S2. The engine rotation period Teg mentioned here represents the period of fuel injection, and in the present embodiment, since the engine is a four-stroke single-cylinder gasoline engine 1, the period of fuel injection that repeats every time the engine 1 rotates 2 times (720 ° ca) is treated as the engine rotation period Teg.

In 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 expression (1) (determination means, period determination step). The motor rotation period Tmt indicates a period in which the fuel is pressure-fed by the piston 56 of the fuel pump 26, and as described above, a period in which the fuel is pressure-fed repeatedly every time the DC motor 42 rotates 1 time is treated as the motor rotation period Tmt. The ECU31 supplies a drive current to the DC motor 42 via the drive circuit 31a in order to function as a motor control means, and 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 Δ T … … (1)

Even if the engine rotation period Teg and the motor rotation period Tmt do not completely coincide with each other, the timings of the engine rotation period Teg and the motor rotation period Tmt may overlap each other due to various factors such as a control error between the engine 1 and the DC motor 42, a detection error of the electromagnetic sensor 32, or an increase or decrease in the engine rotation speed Ne occurring between control periods of the ECU 31. Therefore, the determination value Δ T is set in advance as a threshold value in order to control the rotation periods Teg and Tmt in a direction away from each other not only when the rotation periods Teg and Tmt of both completely match each other but also when the rotation periods Teg and Tmt approach each other to a certain extent (hereinafter, the rotation periods Teg and Tmt are expressed as "approaching each other").

In the above equation (1), only the case where the engine rotation period Teg and the motor rotation period Tmt match each other is assumed, and the relationship between the periods is not assumed to be multiplied. The reason is that the engine 1 and the fuel pump 26 of the present embodiment cannot have their periods multiplied in any operation region. As a matter of course, in the specification in which the periods of both can be multiplied, the expression in consideration of the contents thereof may be changed.

If the determination at step S3 is no (negative), the routine proceeds to step S4, where 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 a value suitable for suppressing the rotation speed Nm of the DC motor 42 for reducing power consumption and for discharging an amount of fuel sufficient for the target injection amount from the injector 16 at that time from the fuel pump 26.

Specifically, a reference value of the duty ratio is calculated based on the operating region of the engine 1, for example, the engine rotation speed Ne and the throttle opening θ th (engine load), and the reference value is corrected by a correction coefficient corresponding to the cooling water temperature Tw and the battery voltage Vbtt, thereby calculating the final duty ratio. However, the duty ratio calculation process is not limited to this, and a fixed value set in advance may be applied as the duty ratio regardless of the operating region of the engine 1, for example. The duty ratio is thus calculated, and in subsequent step S5, the drive current flowing in the DC motor 42 is controlled based on the duty ratio, and then the flow ends.

On the other hand, when the engine rotation period Teg and the motor rotation period Tmt are close to each other and it is determined as yes (affirmative) in step S3, the routine proceeds to step S6, where the duty ratio of the drive current flowing into the DC motor 42 is corrected to increase the predetermined value set in advance or corrected to decrease the predetermined value set in advance (motor speed change command means, rotation speed change step), and then the routine proceeds to step S5. The value to be corrected is a duty ratio at the time of realizing the motor rotation period Tmt applied to the calculation processing of the above equation (1), and the motor rotation speed Nm is increased or decreased in accordance with the correction direction, and the motor rotation period Tmo is increased or decreased in accordance with the increase or decrease, and is separated from the engine rotation period Teg.

Based on the above description: the processing in step S6 is intended 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 cycle Tmo. Therefore, this method is not limited to the correction of the duty ratio as described above, and various modifications are possible, and for example, the power supply to the DC motor 42 may be adjusted by correcting the PWM period and the duty ratio of the drive current at the same time.

In the correction direction of the duty ratio in step S6, when the amount of fuel discharged from the fuel pump 26 has a margin with respect to the target injection amount, the correction can be performed to the increasing side or the decreasing side. However, in step S3, if the duty ratio is corrected to the reduction side in the case where the duty ratio is set corresponding to the minimum required combustion amount for satisfying the target injection amount, the motor rotation speed Nm decreases and the target injection amount may not be achieved. Therefore, in this case, the duty ratio may be corrected to the increase side, and thus the correct fuel injection amount can be maintained.

When the engine rotation period Teg and the motor rotation period Tmt are different from each other by the processing of the ECU31 described above, the drive current flowing into the DC motor 42 is controlled by the duty ratio corresponding to the operating region of the engine 1 as in the normal case, and when the engine rotation period Teg and the motor rotation period Tmt are close to each other, the motor rotation speed Nm is increased or decreased by the correction duty ratio (or the PWM period and the duty ratio), and the motor rotation period Tmo is moved away from the engine rotation period Teg.

As a result, according to the control device of the fuel pump 26 of the present embodiment, the relationship between the fuel injection timing and the fuel pressure-feeding timing can be changed for each combustion cycle by constantly making the motor rotation period Tmt different from the engine rotation period Teg when the engine 1 is operated. Therefore, even if the fuel injection timing and the fuel pressure-feeding timing are accidentally overlapped in a certain combustion cycle, the timings of both will not be overlapped inevitably in the next combustion cycle. Therefore, the operating state in which the combustion of the engine 1 is unstable due to the variation in the fuel injection amount ends at the instant of 1 combustion cycle, and therefore, it is possible to prevent the deterioration of the exhaust gas characteristics and the drivability due to the variation in the fuel injection amount in advance, using the diaphragm/piston combination fuel pump 26 using the DC motor 42 as the drive source.

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 is different in the processing content of the ECU 31. Specifically, although the setting process of the duty ratio is switched according to the result of comparison between the engine rotation period Teg and the motor rotation period Tmt in the first embodiment (step S4 in fig. 3), in the present embodiment, the fuel pressure feed timing of the piston 56 is determined according to the change in the drive current supplied to the DC motor 42, and the setting process of the duty ratio is switched according to the result of comparison between the fuel pressure feed timing and the fuel injection timing of the engine 1. Therefore, in the following description, the points of difference relating to the processing of the ECU31 will be described with emphasis.

First, in order to detect the value of the drive current supplied from the drive circuit 31a to the DC motor 42, the ECU31 of the present embodiment includes a current detection circuit 31b shown by a broken line in fig. 1, and the ECU31 is configured to be able to determine the fuel pressure feed timing of the piston 56 (fuel pressure feed timing determination means) based on the detection result of the current detection circuit 31 b.

In the pump control flow shown in fig. 4, the ECU31 first reads the drive current value of the DC motor 42 in step S11, and determines the fuel pressure feed timing of the piston 56 in the current combustion cycle in step S12 based on the change in the drive current value. Since the drive current value of the DC motor 42 has a characteristic of rapidly increasing at the timing at which the fuel is pressure-fed by the piston 56, the time point when the drive current value changes in the increasing direction is regarded as the fuel pressure-feeding timing TMpump.

In subsequent step S13, it is determined whether or not the fuel injection timing TMinj and the fuel pressure feed timing TMpump of the injector 16 are different from each other based on the following expression (2) (determination means, cycle determination step). In the fuel injection control, the ECU31 controls the driving of the injector 16 by itself, and therefore the driving timing is regarded as the fuel injection timing TMinj (fuel injection timing determining means).

| fuel injection timing TMinj-fuel pressure feeding timing TMpump | ≦ determination value Δ TM … … (2)

The determination value Δ TM has the same meaning as the determination value Δ T of expression (1), and is set in advance not only when the fuel injection timing TMinj and the fuel pressure feeding timing TMpump completely match but also when both approach to each other to a certain extent (hereinafter, the two approach is referred to as "the case of approaching" to each other).

If the determination at step S13 is no (negative), the duty ratio of the drive current supplied to the DC motor 42 is calculated in step S14 according to the operation region of the engine 1 by a usual method. If the determination at step S13 is yes, the duty ratio (or PWM period and duty ratio) of the drive current flowing into the DC motor 42 is corrected in an increasing manner or in a decreasing manner at step S16 (motor speed change command means, rotational speed change step), and then the drive current flowing into the DC motor 42 is controlled at step S15.

When the fuel injection timing TMinj and the fuel pressure feed timing TMpump are different from each other by the processing of the ECU31 described above, the drive current flowing to the DC motor 42 is controlled by the duty ratio corresponding to the operation region of the engine 1 as in the normal case, and when the fuel injection timing TMinj and the fuel pressure feed timing TMpump are close to each other, the motor rotation speed Nm is increased or decreased by the correction duty ratio. The increase or decrease in the motor rotation speed Nm means that the motor rotation period Tmo is shifted away from the engine rotation period Teg, and the fuel pressure feed timing TMpump is also shifted away from the fuel injection timing TMinj.

As a result, the same operational effects as those of the first embodiment can be obtained, and although not described repeatedly, the relationship between the fuel injection timing TMinj and the fuel pressure-feeding timing TMpump can be changed for each combustion cycle by constantly making the motor rotation period Tmt different from the engine rotation period Teg when the engine 1 is operated. Therefore, in addition to using the diaphragm/piston combination fuel pump 26 using the DC motor 42 as a drive source, it is possible to prevent deterioration of the exhaust gas characteristics and the drivability due to variation in the fuel injection amount.

The embodiment of the present invention is not limited to the above embodiment. For example, in the above-described embodiment, the present invention is embodied as a control device for the fuel pump 26 mounted on the engine 1 of a two-wheeled vehicle, but the mounting object of 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 the above embodiment, the diaphragm/piston dual-purpose 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 is also applicable to a piston-type fuel pump that does not have the diaphragm 46 and uses only the piston 56 to pressurize and supply fuel.

Description of the reference symbols

1 Engine

16 ejector

26 Fuel pump

31 ECU (determination means, Motor speed Change Command means, Engine rotation period calculation means, Motor rotation period calculation means, Fuel injection timing determination means)

31a drive circuit (Motor control Unit)

31b Current detection Circuit (Fuel pressure feed timing determining means)

42 DC motor

46 diaphragm

56 piston

Claims

1. A control device of a fuel pump, characterized by comprising:

a piston-type fuel pump that reciprocates a piston by driving of a motor and pressure-feeds fuel pressurized to a predetermined pressure;

an injector that injects the fuel pressure-fed from the fuel pump in synchronization with a combustion cycle of an engine;

a motor control unit that supplies a drive current to the motor and controls the motor;

a determination unit that executes a determination process of determining whether one of a fuel injection period of the injector and a fuel pressure-feed period of the piston corresponds to an integer multiple of the other; and

and a motor speed change command unit that causes the motor control unit to change the rotation speed of the motor when the determination unit determines that one of a fuel injection period of the injector and a fuel pressure-feed period of the piston corresponds to an integer multiple of the other.

2. The control device for a fuel pump according to claim 1, further comprising:

an engine rotation period calculation unit that calculates a rotation period of the engine; and

a motor rotation period calculation unit that calculates a 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 electric motor rotation period calculation unit, and executes determination processing of whether or not both are different.

3. The control device for a fuel pump according to claim 1, further comprising:

a fuel injection timing determining unit that determines a fuel injection timing of the injector; and

a fuel pressure feed timing determination unit that determines a fuel pressure feed timing of the piston according to a change in a drive current value supplied to the motor by the motor control unit,

the determination means compares the fuel injection timing of the injector determined by the fuel injection timing determination means with the fuel pressure-feed timing of the piston determined by the fuel pressure-feed timing determination means, and executes determination processing of whether or not both are different.

4. The control device of a fuel pump according to any one of claims 1 to 3,

the fuel pump is configured to reciprocate a diaphragm by driving of the motor, reciprocate a piston in synchronization with the reciprocation of the diaphragm, and pressurize the fuel sent from the diaphragm by the piston and pressure-feed the fuel to the injector.

5. A control method of a fuel pump, characterized by comprising:

a cycle determination step of comparing a fuel pressure-feed cycle of a piston-type fuel pump that reciprocates a piston by driving of an electric motor and pressure-feeds fuel with a fuel injection cycle of an injector that injects fuel pressure-fed from the fuel pump in synchronization with a combustion cycle of an engine, and determining whether one of the fuel pressure-feed cycle and the fuel injection cycle corresponds to an integer multiple of the other; and

and a rotation speed changing step of changing the rotation speed of the electric motor when it is determined by the cycle determining step that either one of the fuel pressure-feed cycle and the fuel injection cycle corresponds to an integer multiple of the other.