JP2017002770A - Control device and control method of fuel pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device and control method of a fuel pump, capable of suppressing variation in fuel injection amount resulting from combustion pressure fluctuation and preventing deterioration of exhaust gas characteristic and drivability, for a plunger type fuel pump having a motor as a driving source.SOLUTION: Pressurized fuel is fed to an injector by reciprocatively moving a plunger with driving of a DC motor, synchronized with a combustion cycle of an engine, and then injected from the injector. An engine rotation period and a motor rotation period are compared, when the periods are different from each other, a duty ratio of drive current of the DC motor is calculated from the operation region of the engine by a usual method, and when the periods are close to each other, the duty ratio of drive current to the DC motor is increasingly corrected or decreasingly corrected by only a predetermined value, to thereby drive and control the DC motor on the basis of the corrected duty ratio. Consequently, during operation of the engine, the motor rotation period is always different from the engine rotation period.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fuel pump control device and a fuel pump control method, and more particularly, to a plunger type fuel pump that feeds fuel pressurized to a predetermined pressure by reciprocating a plunger using a motor as a drive source to an injector of an engine. The present invention relates to a control device and a control method.

  Conventionally, fuel injection devices with electronic control of fuel supply to engines have been widely used for the purpose of improving exhaust gas characteristics and improving fuel efficiency. The target is not only for four-wheeled vehicles but also for various motorcycles and generators. It also extends. In this type of fuel injection device, the fuel in the fuel tank is pumped up by a fuel pump, pressurized to a predetermined pressure, and the pressurized fuel is supplied to an injector provided in the intake pipe of the engine, and is synchronized with the combustion cycle of the engine. Thus, the injector is controlled to open and close to inject fuel into the intake pipe.

  As such a fuel pump, for example, in a relatively small displacement engine used for a two-wheeled vehicle, a generator, etc., the fuel pump itself is required to be miniaturized, and power consumption required for driving the pump is also desired. Therefore, a plunger type fuel pump having characteristics suitable for those conditions may be employed.

  In this type of plunger type fuel pump, a plunger is slidably disposed in a cylinder and urged by a return spring in one direction, and then driven in the opposite direction by excitation of an electromagnetic coil. It is configured. The plunger reciprocates in accordance with the periodic excitation of the electromagnetic coil, and the fuel is pressurized and discharged intermittently in the cylinder. Due to such an operating principle, the pressure of the fuel supplied to the injector fluctuates periodically according to the reciprocating movement of the plunger, and even if controlled during the same valve opening time of the injector, the fuel injection amount varies due to fluctuations in the fuel pressure. As a result, engine combustion becomes unstable and exhaust gas characteristics and drivability deteriorate.

  Therefore, for example, in the plunger type fuel pump described in Patent Document 1, the problem is solved by synchronizing the drive of the fuel pump with the rotation of the engine. That is, while 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, a time earlier than the fuel injection start time t2 by a predetermined time Tf is determined as the fuel pump drive start time t1, The fuel pump is driven (the electromagnetic coil is excited) for the fuel pump drive time Tpump from the pump drive start time t1. As a result, fuel injection is always performed at the timing when the fuel pressure rises by driving the fuel pump, and variations in the fuel injection amount due to fuel pressure fluctuations can be suppressed.

Japanese Patent Laid-Open No. 2004-52596

  Since the plunger type fuel pump described in Patent Document 1 can freely change the excitation timing of the electromagnetic coil as a drive source for each combustion cycle of the engine, the fuel injection timing that changes momentarily according to the engine operating region. Following this, the drive timing of the fuel pump can be controlled as described above. However, in a plunger type fuel pump using a motor as a drive source, it is necessary to change the rotation speed of the motor in order to change the drive timing, and it is realistic to suddenly change the rotation speed of the motor following the fuel injection timing. It is difficult to. Therefore, the technique of Patent Document 1 cannot be applied to a plunger-type fuel pump using a motor as a drive source, and another solution has been demanded.

  The present invention has been made to solve such problems, and the object of the present invention is directed to a plunger type fuel pump using a motor as a drive source, and variations in fuel injection amount due to fluctuations in fuel pressure. It is an object of the present invention to provide a fuel pump control device and a control method capable of preventing the deterioration of exhaust gas characteristics and drivability by suppressing the above.

  In order to achieve the above object, a fuel pump control device according to the present invention includes a plunger-type fuel pump that pumps fuel pressurized to a predetermined pressure by reciprocating a plunger by driving a motor, and is pumped from the fuel pump. Any one of an injector for injecting the injected fuel in synchronization with the combustion cycle of the engine, a motor control means for controlling the motor by supplying a drive current to the motor, and a cycle of fuel injection by the injector and a cycle of fuel pressure by the plunger Determining means for executing a process for determining whether one of them corresponds to a multiple of the other, and when the determining means determines that one of them corresponds to a multiple of the other, the motor control means indicates the rotation speed of the motor. The motor speed change command means for changing is provided.

  According to the fuel pump control device of the present invention configured as described above, when either one of the fuel injection period by the injector and the fuel pressure feeding period by the plunger corresponds to a multiple of the other, the rotation speed of the motor is changed. Thus, the cycle of fuel pumping is kept away from the cycle of fuel injection. For this reason, during the operation of the engine, the fuel pumping cycle is always different from the fuel injection cycle, and the relationship between the fuel injection timing and the fuel pumping timing changes for each combustion cycle. Therefore, even if the fuel injection timing and the fuel pumping timing accidentally overlap in a certain combustion cycle, both timings do not always overlap in the next combustion cycle, and the engine combustion is unstable due to variations in the fuel injection amount. The operating state ends in an instant for one combustion cycle.

As another aspect, the engine further includes an engine rotation cycle calculation unit that calculates the rotation cycle of the engine and a motor rotation cycle calculation unit that calculates the rotation cycle of the motor, and the determination unit calculates the engine calculated by the engine rotation cycle calculation unit. It is desirable that the determination process is executed by comparing the rotation period of the motor and the rotation period of the motor calculated by the motor rotation period calculation means.
When configured in this manner, the rotational speed of the motor is changed according to the determination result obtained by comparing the rotational period of the engine and the rotational period of the motor.

As other aspects, fuel injection timing specifying means for specifying the fuel injection timing of the injector, and fuel pumping timing specifying means for specifying the fuel pumping timing of the plunger based on a change in the drive current value supplied to the motor by the motor control means And the determination means compares the fuel injection timing of the injector identified by the fuel injection timing identification means with the fuel pressure delivery timing of the plunger identified by the fuel pressure timing identification means to execute the determination process. It is desirable to configure.
In such a configuration, the fuel pumping timing of the plunger is specified from the change in the driving current value of the motor, and the rotation speed of the motor is determined according to the determination result comparing the fuel pumping timing and the fuel injection timing of the injector. Be changed.

As another aspect, the fuel pump reciprocates the diaphragm by driving the motor, reciprocates the plunger in synchronism with the reciprocating movement of the diaphragm, pressurizes the fuel delivered from the diaphragm with the plunger, and pumps it to the injector. It is desirable to configure as follows.
When configured in this way, the above-described various functions and effects can be obtained for a fuel pump that uses a diaphragm and a plunger together.

  Further, the fuel pump control method of the present invention includes a fuel pumping cycle by a plunger-type fuel pump that reciprocates a plunger by driving a motor to pump fuel, and a fuel pumped fuel from the fuel pump. The period of the fuel injection by the injector that injects in synchronization with each other, a period determining step for determining whether one of them corresponds to a multiple of the other, and the period determining step for either one to be a multiple of the other And a rotation speed changing step of changing the rotation speed of the motor when it is determined that it corresponds.

  According to the fuel pump control method of the present invention configured as described above, the cycle determination step compares the cycle of fuel pumping by the plunger type fuel pump with the cycle of fuel injection by the injector, and either one is the other. It is determined whether it corresponds to a multiple of. If it is determined that one of them corresponds to the multiple of the other, the rotational speed of the motor is changed by the rotational speed changing step, and the fuel pumping cycle is moved away from the fuel injection cycle.

  According to the control apparatus and control method for a fuel pump of the present invention, a plunger type fuel pump using a motor as a drive source is targeted, and variations in fuel injection amount due to fluctuations in the fuel pressure are suppressed to improve exhaust gas characteristics and drivability. Deterioration can be prevented in advance.

It is a system block diagram which shows the control apparatus of the fuel pump of this invention. It is sectional drawing which shows the detail of a fuel pump. It is a flowchart which shows the fuel pump control routine which ECU of 1st Embodiment performs. It is a flowchart which shows the fuel pump control routine which ECU of 2nd Embodiment performs.

Hereinafter, embodiments in which the present invention is embodied in a control device and a control method for a fuel pump for an engine mounted on a motorcycle will be described.
FIG. 1 is a system configuration diagram showing a control device for a fuel pump according to the present invention.
In FIG. 1, an engine 1 is configured as a 4-cycle single-cylinder gasoline engine with a displacement of 50 cc, and is mounted on a two-wheeled vehicle as a driving power source. 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 interlocked with the reciprocating motion of the piston 4. The crankshaft 6 rotates. A flywheel 7 is attached to the rear end of the crankshaft 6 (on the side of the transmission not shown), and a retractor 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 on the cylinder block 2, and a spark plug 10 is disposed in a posture in which the tip faces the inside of the cylinder. The intake passage 11 connected to the intake port 9a is provided with an air cleaner 12 from the upstream side, a throttle valve 13 that is opened and closed according to the driver's throttle operation, and an injector 16 that injects fuel toward the intake port 9a. ing. The exhaust passage 17 connected to the exhaust port 9b is provided with a three-way catalyst 18 for purifying exhaust gas and a silencer (not shown).

  An intake valve 20 is disposed in the intake port 9a, and an exhaust valve 21 is disposed in the exhaust port 9b. These intake and exhaust valves 20 and 21 are urged toward the valve closing side by a valve spring 22 and are opened by an intake camshaft 23 and an exhaust camshaft 24 that are driven to rotate in synchronization with the crankshaft 6 on the cylinder head 9. To be spoken. As a result, the intake valve 20 and the exhaust valve 21 are opened and closed at a predetermined timing synchronized with the reciprocation of the piston 4, and the combustion cycle of the engine 1 consisting of four strokes of intake, compression, expansion and exhaust is 720 ° CA in crank angle. Repeated every time.

  The fuel (gasoline) stored in the fuel tank 25 is supplied to the injector 16 by a fuel pump 26. The fuel pump 26 of the present embodiment is a kind of plunger type fuel pump, and its configuration and operating state will be described later. A diaphragm and a plunger are used together to pressurize a predetermined pressure of fuel necessary for the operation of the injector 16. It can be pumped (hereinafter also referred to as a diaphragm / plunger combined type). The fuel pump 26 is integrated with the injector 16 and 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, and the pressurized fuel is supplied to the injector 16 and surplus fuel is supplied. Is recovered in the fuel tank 25 via the return hose 28. As a result, fuel of a predetermined pressure is always supplied to the injector 16, and the fuel is injected toward the intake port 9a at a predetermined injection timing and injection amount according to the opening of the injector 16.

  During operation of the engine 1, outside air is sucked into the intake passage 11 through the air cleaner 12 due to the negative pressure generated as the piston 4 descends during the intake stroke, and the intake air is in accordance with the opening of the throttle valve 13. After the flow rate is adjusted, the fuel flows into the cylinder of the engine 1 while the intake valve 20 is opened while being mixed with the fuel injected from the injector 16. After the compression 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 during the expansion stroke, and applies a rotational force to the crankshaft 6 via the piston 4. In the subsequent exhaust stroke, the exhaust gas after combustion is discharged from the cylinder while the exhaust valve 21 is opened, and is discharged outside through the three-way catalyst 18 and the silencer while flowing through the exhaust passage 17.

The combustion cycle of the engine 1 described above is executed based on the control of the ECU 31 (engine control unit). Therefore, on the input side of the ECU 31, an electromagnetic pickup 32 that is disposed opposite to the flywheel 7 and outputs a signal synchronized with the reluctator 7 a, a throttle sensor 33 that detects the opening of the throttle valve 13, and an exhaust passage 17 are disposed. Various sensors such as an O ₂ sensor 34 for changing the output in a step-like manner according to a change in exhaust air-fuel ratio centered on stoichiometric (theoretical air-fuel ratio), and a water temperature sensor 35 for detecting the cooling water temperature Tw of the engine 1 are provided. It is connected. Various devices such as the injector 16, the fuel pump 26, and an igniter 36 that drives the spark plug 10 are connected to the output side of the ECU 31.

Based on these sensor information, the ECU 31 executes various controls such as fuel injection control for driving the injector 16, ignition timing control for driving the spark plug 10, and pump control for driving the fuel pump 26. The engine 1 is operated.
For example, as fuel injection control, the ECU 31 determines a target fuel injection amount based on the engine rotational speed Ne calculated from the signal of the electromagnetic pickup 32 and the throttle opening degree θth detected by the throttle sensor 33 and synchronizes with the combustion cycle of the engine 1. The injector 16 is driven at the predetermined timing to execute fuel injection.

  Further, the ECU 31 determines the target ignition timing based on the engine rotational speed Ne, the throttle opening θth, and the like as ignition timing control, while shaping the signal of the electromagnetic pickup 32 and synchronizing it with the reluctator 7a (in other words, the crank angle). A wavy crank angle signal is generated. Then, the timing corresponding to the target ignition timing is specified based on the crank angle signal, and the igniter 36 is driven to ignite the spark plug 10.

  The ECU 31 has a built-in driver circuit 31a for driving a motor (a DC motor 42 described later) that is a drive source of the fuel pump 26. Then, as pump control, a drive current is supplied from the driver circuit 31a to the motor during operation of the engine 1 to drive the fuel pump 26, and the fuel pressurized to a predetermined pressure is pumped to the injector 16 (motor control means).

By the way, as described above, since the fuel pump 26 of this embodiment is a diaphragm / plunger combined fuel pump, it is necessary to take measures to suppress variations in the fuel injection amount due to fuel pressure fluctuations. However, since the motor is used as the drive source, the drive of the fuel pump is synchronized with the rotation of the engine like the plunger type fuel pump using the electromagnetic coil described in Patent Document 1 as the drive source. Is difficult.
Therefore, in the present embodiment, the problem is solved by making the rotation period of the motor different from the rotation period of the engine 1. Details of the pump control will be described below, but the configuration of the fuel pump 26 will be described prior to that.

FIG. 2 is a cross-sectional view showing details of the fuel pump 26.
The casing of the fuel pump 26 includes a motor casing 41a, a pump casing 41b, and a regulator casing 41c. A DC motor 42 (shown by a broken line) is accommodated in the motor casing 41a as a drive source. A cam 43 is fixed to the output shaft 42a of the DC motor 42. When the cam 43 is rotated by driving the DC motor 42, the cam receiving member 44 is moved in the left-right direction in the figure (hereinafter, this direction is referred to as an axis L direction). It is designed to reciprocate.

  A central portion of a diaphragm 46 is fixed to the cam receiving member 44, and a diaphragm chamber 47 is defined by the diaphragm 46 between the motor casing 41 a and the pump casing 41 b. In response to the reciprocation of the cam receiving member 44, the diaphragm 46 reciprocates alternately between the right side (hereinafter referred to as the suction side) and the left side (hereinafter referred to as the discharge side) in the drawing. When the diaphragm 46 moves to the suction side, the fuel from the fuel tank 25 flows into the diaphragm chamber 47 through the supply hose 27 and the supply passage 50. When moving 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 such fuel transfer is repeated every time the diaphragm 46 reciprocates.

  In the sleeve 55 fitted and fixed to the pump casing 41b, a plunger 56 is slidably disposed along the direction of the axis L. The plunger 56 is connected to the cam receiving member 44 and is synchronized with the reciprocation of the diaphragm 46. Then, the plunger 56 reciprocates between the suction side and the discharge side. When the plunger 56 moves to the suction side, part of the fuel in the diaphragm chamber 47 flows into the plunger 56 through the suction port 56a, and further flows into the pressurizing chamber 57 through the check valve 58. The fuel in the pressurizing chamber 57 is pressurized during the subsequent movement of the plunger 56 to the discharge side, and such pressurization of the fuel is repeated every time the plunger 56 reciprocates.

  The fuel pressurized in the pressurizing chamber 57 by the reciprocating motion of the plunger 56 is supplied to the pressure adjusting mechanism 59 provided in the regulator casing 41c via the check valve 60, and the pressure adjusting mechanism 59 sets the pressure to the set pressure. Adjusted. The surplus fuel generated by the pressure adjustment is discharged to the relief passage 69 and is recovered to the fuel tank 25 side together with the surplus fuel from the diaphragm chamber 47. The fuel whose pressure has been adjusted by the pressure adjusting mechanism 59 is pumped from the pressure adjusting chamber 66 to the injector 16 (shown in FIG. 1) through the injector passage 68, and the intake port of the engine 1 is opened when the injector 16 is opened. It is injected toward 9a.

  As is clear from the above description, since the fuel pump 26 of the present embodiment reciprocates the plunger 56 to pressurize the fuel, fluctuations in fuel pressure are unavoidable. The first technique cannot be applied.

In view of such problems and the characteristics of the fuel pump 26, the present inventor has focused on the following points.
First, the fuel pressurized by the plunger 56 and pressure-adjusted by the pressure adjustment mechanism 59 is supplied to the injector 16 through the injector passage 68. The fuel pressure in the passage from the injector passage 68 to the injector 16 Except for the fuel pumping timing 56 (hereinafter referred to as fuel pumping timing) 56, the pressure is always kept at a stable set pressure (for example, about 300 kPa). Therefore, if the fuel pumping timing is not overlapped with the fuel injection timing of each combustion cycle, fuel injection is always performed under the fuel pressure at a stable set pressure. The influence can be eliminated.

  On the other hand, for example, when the DC motor 42 of the fuel pump 26 is driven at a predetermined rotational speed Nm, the fuel injection timing changes according to the operating region of the engine 1 and a combustion cycle that happens to overlap with the fuel pumping timing occurs. To do. At this time, the cycle of fuel injection (in other words, the rotation cycle Teg of the engine 1 described later and correlates with the fuel injection timing TMinj) and the cycle of fuel pumping (in other words, the rotation cycle Tmo of the DC motor 42 described later). And the fuel pumping timing TMpump), the combustion cycle in which the fuel pumping timing overlaps with the fuel injection timing continuously occurs as long as the engine 1 remains in the operation region. Therefore, while such a phenomenon occurs, the operating state in which the target A / F cannot be achieved because the combustion of the engine 1 is not stabilized due to variations in the fuel injection amount continues, and the exhaust gas characteristics and drivability deteriorate. It becomes a factor.

  The overlap between the fuel injection timing and the fuel pumping timing becomes a problem not only when both periods coincide with each other, but if one of the periods corresponds to a multiple of the other period, the same problem occurs. . For example, when the cycle of fuel injection is twice the cycle of fuel pumping, the fuel pumping timing overlaps the fuel injection timing continuously in each combustion cycle as in the case of the coincidence. On the contrary, when the fuel pumping cycle is twice the fuel injection cycle, the overlap of the fuel pumping timing with the fuel injection timing becomes every other combustion cycle, but the operating range of the engine 1 changes. As long as it is not solved, it still becomes a problem.

  On the other hand, even if the fuel injection timing and the fuel pumping timing overlap in a certain combustion cycle, if either one of the fuel injection cycle or the fuel pumping cycle does not correspond to the other multiple (the two cycles do not match) In the case where the relationship is not a multiple relationship of 2 or more), the timings of both sides do not always overlap in the next combustion cycle. That is, since the operating state in which the combustion of the engine 1 is unstable due to variations in the fuel injection amount is limited to the moment of one combustion cycle, it cannot be a factor that substantially deteriorates exhaust gas characteristics and drivability. Therefore, the occurrence of the overlap between the fuel injection timing and the pumping timing for one combustion cycle can be regarded as within an allowable range.

  Based on the above knowledge, the present inventor controls so that the rotation cycle of the DC motor 42 is always different from the rotation cycle of the engine 1, so that the relationship between the fuel injection timing and the fuel pumping timing changes for each combustion cycle. However, although both timings may accidentally overlap in one combustion cycle, it has been concluded that overlapping in a continuous combustion cycle can be prevented. Hereinafter, two types of techniques for this purpose will be sequentially described as a first embodiment and a 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. When both cycles are close, the rotation cycle of the DC motor 42 is away from the rotation cycle of the engine 1. To control. Therefore, the ECU 31 executes the pump control routine shown in FIG. 3 at a predetermined control interval while the engine 1 is operating.

  First, in step S1, a signal from the electromagnetic pickup 32 is fetched, and based on the signal, an engine rotation period Teg is calculated in step S2 (engine rotation period calculation means). Here, the engine rotation period Teg means the period of fuel injection. In this embodiment, the engine rotation period Teg is a four-cycle single-cylinder gasoline engine 1, and therefore, fuel injection repeated every two rotations (720 ° CA) of the engine 1. The cycle is handled as the engine rotation cycle Teg.

In subsequent step S3, it is determined whether or not the engine rotation period Teg and the motor rotation period Tmt are different according to the following equation (1) (determination means, period determination step). The motor rotation cycle Tmt means the cycle of fuel pumping by the plunger 56 of the fuel pump 26. As described above, the cycle of fuel pumping repeated every rotation of the DC motor 42 is handled as the motor rotation cycle Tmt. Since the ECU 31 supplies drive current to the DC motor 42 via the driver circuit 31a in order to function as motor control means, the rotation period of the DC motor 42 is calculated based on the duty ratio of the drive current (motor). Rotation period calculation means).
| Engine rotation cycle Teg−motor rotation cycle Tmt | ≦ determination value ΔT (1)

  The engine rotation cycle Teg and the motor rotation cycle Tmt are caused by various factors such as a control error of the engine 1 and the DC motor 42, a detection error of the electromagnetic pickup 32, etc., or an increase or decrease of the engine rotation speed Ne generated during the control cycle of the ECU 31. Even if they do not completely match, the timings of both may overlap. Therefore, both rotations including not only perfect coincidence of both rotation periods Teg and Tmt but also rotation periods Teg and Tmt are close to each other (hereinafter referred to as “approaching”). A determination value ΔT is set in advance as a threshold value with the intention of controlling the periods Teg and Tmt in a direction away from each other.

  In the above equation (1), only the case where the engine rotation period Teg and the motor rotation period Tmt coincide with each other is assumed, and the case where both the above-described periods have a multiple relationship is not assumed. The reason is that in the specifications of the engine 1 and the fuel pump 26 of the present embodiment, both cycles do not have a multiple relationship in any operating region. Of course, in the specification in which both cycles can be in a multiple relationship, the expression may be changed to a content that assumes that point.

  When the determination in step S3 is No (negative), 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 suitable for discharging from the fuel pump 26 a fuel amount sufficient to cover the target injection amount from the injector 16 at that time while suppressing the rotational speed Nm of the DC motor 42 to reduce power consumption. It is calculated as a correct value.

  Specifically, the base value of the duty ratio is calculated from the operating region of the engine 1, for example, the engine speed Ne and the throttle opening θth (engine load), and the base value is corrected according to the cooling water temperature Tw and the battery voltage Vbtt. The final duty ratio is calculated by correcting with the coefficient. However, the duty ratio calculation process is not limited to this. For example, a preset fixed value may be applied as the duty ratio regardless of the operation region of the engine 1. The duty ratio is calculated as described above, and in the subsequent step S5, the drive current to the DC motor 42 is controlled based on the duty ratio, and then the routine is terminated.

  On the other hand, when it is determined that the engine rotation period Teg and the motor rotation period Tmt are close to each other, a Yes determination is made in step S3, the process proceeds to step S6, and the duty ratio of the drive current to the DC motor 42 is set in advance. Increase correction or decrease correction by the set predetermined value (motor speed change command means, rotation speed change process), and then the process proceeds to step S5. The value to be corrected is the duty ratio when the motor rotation period Tmt applied in the calculation process of the above equation (1) is achieved, and the motor rotation speed Nm increases or decreases corresponding to the correction direction, and accordingly As a result, the motor rotation cycle Tmo increases or decreases, and is moved away from the engine rotation cycle Teg.

  As is apparent from this description, the purpose of the process of step S6 is to achieve increase / decrease in the motor rotation speed Nm and consequently increase / decrease in the motor rotation cycle Tmo by adjusting the power supplied to the DC motor 42. Therefore, the method is not limited to the above-described correction of the duty ratio, and can be variously modified. For example, even if the power supplied to the DC motor 42 is adjusted by correcting both the PWM period and the duty ratio of the drive current. Good.

  Note that the correction direction of the duty ratio in step S6 can be corrected both on the increase side and on the decrease side when there is a margin in the amount of fuel discharged from the fuel pump 26 with respect to the target injection amount. However, if the duty ratio is set in step S3 corresponding to the minimum fuel amount necessary to cover the target injection amount, the motor rotational speed Nm decreases if the duty ratio is corrected to the decreasing side. As a result, the target injection amount may not be achieved. Therefore, in this case, the duty ratio may be corrected to the increase side, whereby an accurate 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 above ECU 31 processing, the drive current to the DC motor 42 is controlled by the duty ratio according to the operation region of the engine 1 as usual. On the other hand, when the engine rotation period Teg and the motor rotation period Tmt approach each other, the motor rotation speed Nm is increased or decreased by correcting the duty ratio (or PWM period and 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 for the fuel pump 26 of the present embodiment, the motor rotation cycle Tmt is always made different from the engine rotation cycle Teg during the operation of the engine 1, and the relationship between the fuel injection timing and the fuel pumping timing is determined. It can be changed for each combustion cycle. For this reason, even if the fuel injection timing and the fuel pumping timing accidentally overlap in a certain combustion cycle, both timings do not necessarily overlap in the next combustion cycle. Therefore, since the operation state in which the combustion of the engine 1 is unstable due to variations in the fuel injection amount ends instantaneously for one combustion cycle, the diaphragm / plunger combined fuel pump 26 using the DC motor 42 as a drive source is used. Thus, it is possible to prevent deterioration of exhaust gas characteristics and drivability due to variations in the fuel injection amount.

[Second Embodiment]
Next, a second embodiment embodying the present invention will be described. The hardware configuration of this embodiment is the same as that of the first embodiment, and the difference is in the processing contents of the ECU 31. Specifically, in the first embodiment, the duty ratio setting process is switched based on the comparison result between the engine rotation period Teg and the motor rotation period Tmt (step S4 in FIG. 3), but in this embodiment, the DC motor 42 is switched. The fuel pumping timing of the plunger 56 is specified from the change in the drive current value supplied to the engine, and the duty ratio setting process is switched based on the comparison result between the fuel pumping timing and the fuel injection timing of the engine 1. Therefore, in the following description, differences regarding the processing of the ECU 31 will be mainly described.

  First, in order to detect the drive current value supplied from the driver circuit 31a to the DC motor 42, the ECU 31 of this embodiment is provided with a current detection circuit 31b indicated by a broken line in FIG. Based on the detection result of 31b, the ECU 31 can specify the fuel pumping timing of the plunger 56 (fuel pumping timing specifying means).

  In the pump control routine shown in FIG. 4, the ECU 31 first captures the drive current value of the DC motor 42 in step S11, and based on the change in the drive current value, determines the fuel pumping timing of the plunger 56 in the current combustion cycle in step S12. Identify. Since the driving current value of the DC motor 42 has a characteristic of rapidly increasing at the timing when the fuel is pumped by the plunger 56, the time point when the driving current value changes in the increasing direction is regarded as the fuel pumping timing TMpump.

In the subsequent step S13, it is determined whether or not the fuel injection timing TMinj by the injector 16 is different from the fuel pumping timing TMpump according to the following equation (2) (determination means, cycle determination step). In the fuel injection control, since the ECU 31 controls the injector 16 itself, the driving timing is regarded as the fuel injection timing TMinj (fuel injection timing specifying means).
｜ Fuel injection timing TMinj−Fuel pumping timing TMpump | ≦ determination value ΔTM (2)

  The determination value ΔTM has the same purpose as the determination value ΔT in the equation (1). In addition to the complete coincidence of the fuel injection timing TMinj and the fuel pumping timing TMpump, both are close to some extent (hereinafter referred to as “ It is set in advance so as to include “when approaching”.

  When the determination in step S13 is No, in step S14, the duty ratio of the drive current supplied to the DC motor 42 from the operation region of the engine 1 is calculated by a normal method. When the determination in step S13 is Yes, the duty ratio (or PWM cycle and duty ratio) of the drive current to the DC motor 42 is increased or decreased in step S16 (motor speed change command means, rotation speed change). Step) After that, the drive current to the DC motor 42 is controlled in step S15.

  When the fuel injection timing TMinj and the fuel pumping timing TMpump are different from each other by the processing of the ECU 31, the drive current to the DC motor 42 is controlled by the duty ratio according to the operation region of the engine 1 as usual. On the other hand, when the fuel injection timing TMinj approaches the fuel pumping timing TMpump, the motor rotation speed Nm is increased or decreased by correcting the duty ratio. The increase / decrease in the motor rotation speed Nm is that the motor rotation cycle Tmo is moved away from the engine rotation cycle Teg, and at the same time, the fuel pumping timing TMpump is moved away from the fuel injection timing TMinj.

  As a result, the same operational effects as those of the first embodiment are obtained, and there is no redundant description. However, during the operation of the engine 1, the motor rotation cycle Tmt is always different from the engine rotation cycle Teg, and the fuel injection timing TMinj The relationship with the fuel pumping timing TMpump can be changed for each combustion cycle. Therefore, after using the diaphragm / plunger combined fuel pump 26 using the DC motor 42 as a drive source, it is possible to prevent deterioration in exhaust gas characteristics and drivability due to variations in the fuel injection amount.

  In addition, the aspect of this invention is not limited to embodiment. For example, in the above embodiment, the control device for the fuel pump 26 for the engine 1 mounted on the motorcycle is embodied, but the mounting target of the engine 1 is not limited to this. For example, the present invention may be embodied in a control device and control method for a fuel pump for an engine mounted on a tricycle or a generator.

  Moreover, in the said embodiment, although applied to the diaphragm and plunger combined type fuel pump 26, the form of the fuel pump 26 is not restricted to this. For example, the present invention may be applied to a plunger type fuel pump that pressurizes and supplies fuel only by the plunger 56 without having the diaphragm 46.

1 Engine 16 Injector 26 Fuel Pump 31 ECU
(Motor control means, determination means, motor speed change command means,
Engine rotation period calculation means, motor rotation period calculation means,
Fuel injection timing specifying means, fuel pumping timing specifying means)
31a Driver circuit (motor control means)
31b Current detection circuit (fuel pumping timing specifying means)
42 DC motor 46 Diaphragm 56 Plunger

Claims (5)

A plunger-type fuel pump that reciprocates the plunger by driving the motor to pump fuel pressurized to a predetermined pressure;
An injector that injects fuel pumped from the fuel pump in synchronization with an engine combustion cycle;
Motor control means for controlling the motor by supplying a driving current to the motor;
A determination means for performing a determination process as to whether or not one of a cycle of fuel injection by the injector and a cycle of fuel pumping by the plunger is a multiple of the other;
A fuel pump comprising: motor speed change command means for causing the motor control means to change the rotation speed of the motor when it is determined by the determination means that any one of them corresponds to a multiple of the other. Control device. Engine rotation period calculating means for calculating the engine rotation period;
Motor rotation period calculating means for calculating the rotation period of the motor,
The determination unit performs a determination process by comparing the engine rotation cycle calculated by the engine rotation cycle calculation unit with the motor rotation cycle calculated by the motor rotation cycle calculation unit. The fuel pump control device according to claim 1. Fuel injection timing specifying means for specifying the fuel injection timing of the injector;
Fuel pressure feed timing specifying means for specifying the fuel pressure feed timing of the plunger based on a change in the drive current value supplied to the motor by the motor control means,
The determination means performs a determination process by comparing the fuel injection timing of the injector specified by the fuel injection timing specification means with the fuel pressure supply timing of the plunger specified by the fuel pressure timing specification means. The fuel pump control device according to claim 1, wherein: The fuel pump reciprocates the diaphragm by driving the motor, reciprocates the plunger in synchronization with the reciprocation of the diaphragm, pressurizes the fuel delivered from the diaphragm with the plunger, and pressurizes the fuel to the injector. 4. The fuel pump control device according to claim 1, wherein the control device is configured to do so. A fuel pumping cycle by a plunger type fuel pump that pumps fuel by reciprocating a plunger by driving a motor, and a fuel injection by an injector that injects fuel pumped from the fuel pump in synchronization with a combustion cycle of an engine. A period determination step of comparing the period and determining whether one of them corresponds to a multiple of the other;
A fuel pump control method comprising: a rotation speed changing step of changing a rotation speed of the motor when it is determined by the cycle determination step that any one of them corresponds to a multiple of the other.

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