JP2009121458A - Fuel supply control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel supply control system materializing stabilization of fuel pressure and fuel injection quantity with a low-cost structure. <P>SOLUTION: In the fuel supply control system provided with a control unit 1 controlling fuel delivery quantity by controlling rotation speed of a fuel pump motor, a stepping motor is used as the fuel pump motor, and the control unit 1 is provided with a drive pulse rate control means 103 controlling drive pulse rate of pulses for driving the stepping motor according to required fuel injection quantity and a PWM duty ratio control means 104 dividing apply time of the drive pulse applied to the stepping motor into a plurality of periods and controlling current with changing each pulse modulation control duty ratio for the plurality of periods. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel supply control system in which fuel pumped from a fuel tank to a delivery pipe by a fuel pump is injected into an engine cylinder by a fuel injection valve (injector).

  Some conventional fuel supply control systems perform PWM control of the motor in order to control the fuel discharge amount control by controlling the rotational speed of the fuel pump motor (see, for example, Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 10-266920 JP 2000-220548 A

However, the prior art has the following problems.
As described above, conventionally, the fuel pump motor is driven by PWM control, and the motor rotation speed is controlled by setting the duty ratio. Therefore, when a large amount of fuel discharge is required, it is necessary to increase the duty ratio and increase the motor rotation speed. As a result, the power consumption increases, the amount of heat generated from the motor increases, and the fuel temperature rises.

  When the fuel temperature rises in this manner, the fuel is vaporized in the fuel pipe, and bubbles (vapor) are likely to be generated. When bubbles are generated, the fuel cannot be pressurized, the fuel pressure becomes unstable, and the injection amount from the injector also becomes unstable.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain a fuel supply control system that realizes stabilization of fuel pressure and fuel injection amount with an inexpensive configuration.

  A fuel supply control system according to the present invention uses a stepping motor as a fuel pump motor in a fuel supply control system including a control unit that controls a fuel discharge amount by controlling a rotation speed of a fuel pump motor. The control unit includes a drive pulse rate control means for controlling a drive pulse rate of a pulse for driving the stepping motor in accordance with a required fuel injection amount, and an application time of the drive pulse applied to the stepping motor in a plurality of periods. And PWM duty ratio control means for performing current control by changing the pulse modulation control duty ratio of each of a plurality of periods.

  According to the present invention, a stepping motor that enables speed control with an inexpensive configuration is applied as the fuel pump motor, and in the control, the drive pulse rate applied to the motor is controlled according to the required fuel injection amount. At the same time, the pulse application time is divided into a plurality of periods, and the current control is performed by setting a desired duty ratio for each period, thereby adjusting the amount of fuel discharged from the fuel pump. Thus, a fuel supply control system that realizes stabilization of the fuel pressure and the fuel injection amount can be obtained.

  Hereinafter, a preferred embodiment of a fuel supply control system of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a fuel injection control system in Embodiment 1 of the present invention. The fuel supply control system includes a control unit 1, a throttle valve 2, a throttle position sensor 3, an engine temperature sensor 4, a crank angle sensor 5, a fuel tank 6, a fuel supply device 7, a pressure adjustment device 8, and an injector 9. The

  The control unit 1 stores a program and a map for controlling the operation of the entire engine. The throttle position sensor 3 measures the opening degree of the throttle valve 2. The engine temperature sensor 4 measures the wall temperature of the engine. The crank angle sensor 5 is used for crank position measurement and engine rotation speed calculation.

  The control unit 1 then determines the appropriate fuel injection timing from information such as the throttle position sensor 3, the engine temperature sensor 4, the crank angle sensor 5, and other intake air temperature sensors (not shown) that measure the temperature of the intake air. The fuel injection amount is calculated, and a drive signal is output to the injector 9 which is a fuel injection device.

  Further, the control unit 1 outputs an ignition signal to an ignition coil (not shown) at an appropriate timing based on information from various sensors. As a result, a spark is generated at the spark plug, the mixture of fuel and intake air in the engine cylinder burns, and the piston of the engine is pushed out, whereby the crankshaft rotates.

  The fuel supply device 7 is driven by a drive signal from the control unit 1 and sucks and discharges fuel from the fuel tank 6 through a filter. The discharged fuel is adjusted to a predetermined pressure by the pressure adjusting device 8, passes through the high-pressure fuel pipe, and is supplied to the injector 9.

Next, the fuel pump in the fuel supply device 7 and its drive motor will be described.
FIG. 2 is a configuration diagram of the fuel pump according to the first embodiment of the present invention. As a drive motor for this fuel pump, a motor without a power supply brush is preferable in order to avoid the generation of foreign matter.

  The fuel pump of the present invention pressurizes the fuel by pushing a plurality of pistons 20 with a plate 19 provided at the tip of the rotor. Therefore, in pressurizing the fuel, it is only necessary to be able to continuously rotate in only one direction, and a stepping motor can be applied as the drive motor. In the present invention, a unipolar drive type stepping motor is applied.

  The stator of the stepping motor includes stators 12 and 13 and a coil 14 wound around a bobbin. A stator in which the coil 14 is disposed between the stators 12 and 13 is a one-phase stator. The stators 12 and 13 have pole teeth, both of which are formed in the same shape and the same number on the respective stators 12 and 13 and are arranged on the circumference at an equal pitch.

  A two-phase stator is configured by stacking the stators having the same configuration by shifting by a half of the pole tooth pitch. As the stator, the cost of the motor is reduced by using a claw pole type in which a steel plate is press-formed by press working to form a magnetic pole face facing the rotor magnet 15.

  The rotor includes a shaft 16, a rotor magnet 15, and a plate 19. The plate 19 is fixed to the tip end of the shaft 16 while being inclined by a certain angle. The rotor magnet 15 is attracted by the rotating magnetic flux generated from the stator, and the rotor rotates.

  One stator is configured by bifilar winding that simultaneously winds two copper wires. FIG. 3 is a diagram showing the relationship between the stator and terminals of the stepping motor according to Embodiment 1 of the present invention. By shifting the terminals T1 and T3 and the terminals T4 and T6 shown in FIG. 3 by 90 degrees in electrical angle and sequentially switching energization within each phase, the stepping motor has the number of magnetic pole faces of the stator and the rotor magnet. It can be rotated by a step angle determined by the number of poles of 15. Terminals T2 and T5 are connected to a battery power source.

  FIG. 4 is a diagram illustrating a drive pulse energization pattern in the stepping motor according to the first embodiment of the present invention. At any moment, two-phase full-step energization is performed in which any two phases are always energized. In the present invention, a unipolar drive system is adopted as the motor control circuit. Unipolar drive can reduce the number of power elements required for switching the energized phase compared to bipolar drive. As a result, the cost of the motor control circuit is reduced.

  In FIG. 2, the pump portion includes a plate 19, a piston 20, a suction valve 21, a discharge valve 22, a cylinder 23, a plate 24, and a spring 28. The fuel flowing into the pump from the suction port 26 is driven up and down by the plate 19 that rotates as the rotor rotates, so that the pressure increasing chamber provided on the lower side of the piston 20 through the suction valve 21. 29. Then, the fuel fed into the pressure increasing chamber 29 is pressurized and fed from the discharge port 27 through the discharge valve 22.

  In the first embodiment, as schematically shown in FIG. 4, a pulse application time corresponding to a unit time in which a PWM-controlled drive pulse is applied to the stepping motor (the pulse application time shown in FIG. 4). Is equivalent to the first half period and the second half period. The present invention is characterized in that the current value is individually controlled for each of the first half period and the second half period.

  The current value is controlled by setting the duty ratio in PWM control. The purpose of such two-stage current control is to reduce the heat generation of the motor by suppressing the current consumption as much as possible while securing the torque of the motor.

In order to achieve such an object, specifically, the following settings and controls are performed.
1) The time division is set so that the first half period is longer than the second half period.
2) As for the time of the first half period, ensure the time more than the electrical time constant of the motor coil.
3) The duty ratio in the first half period is set to a value higher than the duty ratio in the second half period.

  FIG. 5 is a schematic diagram of duty ratio setting within one pulse application time in the first embodiment of the present invention. In the first half period in which the load angle between the rotor and the stator pole teeth is large, torque is secured by setting a high duty ratio and supplying current. On the other hand, in the latter half period, the Joule heat of the motor coil is reduced by setting the duty ratio so low as not to drop the inertia of the rotor and suppressing the current.

  By performing such control, motor heat generation can be suppressed and an increase in fuel temperature can be suppressed. Moreover, since the increase in resistance value due to the temperature rise of the coil can be suppressed, high torque can be secured. In addition, due to the decrease in coil temperature, thermal deterioration of the coil can be suppressed, and the reliability of the fuel supply device can be improved.

  Next, the internal configuration and operation of the control unit 1 will be described. FIG. 6 is a control block diagram relating to the control unit 1 according to Embodiment 1 of the present invention. The control unit 1 includes an engine speed calculation means 101, a required fuel injection amount calculation means 102, a drive pulse rate control means 103, and a PWM duty ratio control means 104.

  The required fuel injection amount changes according to the state of the engine speed and engine load (throttle opening, etc.). Therefore, the required fuel injection amount calculation means 102 in the control unit 1 calculates this required fuel injection amount based on various sensor inputs. Furthermore, the required fuel injection amount calculation means 102 can calculate the required fuel discharge amount from the fuel pump from the calculated required fuel injection amount.

  Next, the drive pulse rate control means 103 converts the fuel discharge amount obtained by the required fuel injection amount calculation means 102 into a drive pulse rate of the motor. The drive pulse rate control means 103 sets the drive pulse rate to a low frequency when the required fuel injection amount is less than a predetermined value, such as during idle operation. As a result, the motor torque can be suppressed without inadvertently reducing the motor torque.

  Further, when the pulse rate is increased in the stepping motor, the impedance increases due to the influence of the coil inductance, and as a result, the current decreases and the torque decreases. Therefore, it has been found that in order to obtain a high torque at the start of fuel pump drive, that is, at the start of the vehicle, it is better to drive at a low pulse rate.

  Conversely, when the required fuel injection amount is greater than a predetermined value, such as during high engine speeds, a high-frequency drive pulse rate is set, and necessary fuel can be secured.

  In the first embodiment, the drive pulse rate control according to the required fuel injection amount is adopted. However, it is also possible to detect the engine rotation speed and the throttle opening amount from a sensor or the like and set the drive pulse rate according to them. Become. By setting in this way, it is possible to reduce the load on the control unit 1 when calculating the fuel discharge amount of the fuel pump from the required fuel injection amount.

  In the present invention, the minimum drive pulse rate is applied when starting the vehicle, and the current value at this time is set to the maximum current that can be set in each period by setting the PWM control duty ratio to 100%. A value shall be supplied. Thereby, a fuel pump can be started reliably with a high motor torque.

  After driving the stepping motor at this minimum pulse rate for a predetermined time, the pulse rate is arbitrarily set as described above according to the engine speed and load.

  Further, when the output value of the engine temperature sensor 4 such as a water temperature sensor or a machine temperature sensor shows a temperature higher than a predetermined value, it is considered that the fuel pump motor is also heated. For this reason, it can be said that it is in a state where bubbles are easily generated. Therefore, in order to suppress the heat generation of the motor, the drive pulse rate control means 103 sets the drive pulse rate high when the output value from the engine temperature sensor 4 indicates a temperature higher than a predetermined value. Or, set the duty ratio low. As a result, it is possible to reduce the current consumption of the motor and suppress the generation of bubbles.

  Further, when the output value of the engine temperature sensor 4 such as the water temperature sensor or the machine temperature sensor indicates a temperature lower than a predetermined value, it is not necessary to consider that the fuel pump motor is heated. For this reason, control as in the case where the engine temperature is high is not particularly required.

  FIG. 7 is a diagram showing an example of a PWM control duty ratio table provided in the PWM duty ratio control means 104 according to Embodiment 1 of the present invention. The PWM duty ratio control means 104 can determine an appropriate PWM control duty ratio from the values of the engine temperature and the drive pulse rate by using this table.

  As described above, according to the first embodiment, a stepping motor that allows speed control with an inexpensive configuration is applied as the fuel pump motor. Further, in the PWM control, the pulse application time is divided into two parts, a first half period and a second half period, and the fuel discharge amount is controlled by performing two-stage current control individually. Thereby, it is possible to obtain a fuel supply control system that realizes stabilization of the fuel pressure and the fuel injection amount with an inexpensive configuration.

Summarizing the more specific effects of the configuration as described above, the following points can be cited.
1) Suppression of fuel temperature rise 2) Reduction of fuel vapor generation amount 3) Reduction of motor heat generation 4) Reduction of motor cost 5) Reduction of motor control circuit cost 6) Improvement of motor torque by reduction of coil temperature, and Improvement of motor reliability 7) Power saving of motor 8) Stabilization of fuel pressure and fuel injection amount 9) Avoiding step out of stepping motor 10) Ensuring torque at motor startup

In the first embodiment described above, the case where the following three settings and controls are performed has been described.
1) The time division is set so that the first half period is longer than the second half period.
2) As for the time of the first half period, ensure the time more than the electrical time constant of the motor coil.
3) The duty ratio in the first half period is set to a value higher than the duty ratio in the second half period.
However, the present invention does not necessarily have to satisfy all three conditions. At the very least, if the third condition, “Set the duty ratio of the first half period to a value higher than the duty ratio of the second half period” is satisfied, the fuel pressure and fuel injection amount can be stabilized with an inexpensive configuration. It is possible to obtain a fuel supply control system to be realized.

Embodiment 2. FIG.
FIG. 8 is a configuration diagram of the fuel supply control system according to the second embodiment of the present invention. Compared with the configuration of FIG. 1 in the first embodiment, the configuration of FIG. 8 in the second embodiment further includes a pressure sensor 10 in the high-pressure pipe between the fuel supply device 7 and the fuel injection valve. Is different.

  The stepping motor is driven at a driving pulse rate set based on the engine speed and load. As described in the first embodiment, when the stepping motor steps out, the discharge amount of the fuel pump decreases. As a result, in the step-out state, the fuel pressure fluctuation generated by the injection timing of the injector increases more than in the normal state. Therefore, it is possible to detect the step-out of the stepping motor by monitoring the fluctuation of the fuel pressure based on the pressure value detected by the pressure sensor 10.

  FIG. 9 is a diagram showing an example of actually measuring the relationship between the duty ratio in the second half period and the fuel pump discharge amount in the second embodiment of the present invention. FIG. 10 is a diagram showing an example in which the relationship between the duty ratio in the second half period and the fuel pressure fluctuation amount is actually measured in the second embodiment of the present invention.

  In this case, when the duty ratio in the second half period is less than 60%, the fuel discharge amount starts to decrease as shown in FIG. 9, indicating that the torque of the stepping motor becomes insufficient. As a result, the fuel pressure fluctuation increases as shown in FIG. 10 corresponding to the decrease in the fuel discharge amount in FIG.

  Therefore, the control unit 1 can detect the step-out of the stepping motor by detecting the fluctuation of the fuel pressure. Furthermore, the control unit 1 can avoid the step-out by controlling the duty ratio in the latter half period so that the fluctuation of the fuel pressure becomes a predetermined threshold value or less. Specifically, the control unit 1 can eliminate the torque shortage and avoid the step-out by increasing the duty ratio in the second half period so that the fluctuation of the fuel pressure becomes a predetermined threshold value or less. .

  As described above, according to the second embodiment, the step-out state can be detected at an early stage also by monitoring the fuel pressure fluctuation using the pressure sensor, and the normal rotation state can be avoided by avoiding the step-out. The same effect as in the first embodiment can be obtained.

Embodiment 3 FIG.
In the first and second embodiments, the case where the pulse application time is divided into two sections of the first half period and the second half period has been described. In the third embodiment, a case where the pulse application time is divided into a plurality of periods of three or more sections will be described.

  FIG. 11 is a diagram showing an energization pattern of drive pulses in the stepping motor according to the third embodiment of the present invention. FIG. 12 is a schematic diagram of duty ratio setting within one pulse application time in Embodiment 3 of the present invention. 11 and 12 illustrate a case where the pulse application time is divided into N sections from the first period to the Nth period (N is an integer of 3 or more).

  The basic system configuration is the same as the configuration of FIG. 1 in the first embodiment. In the third embodiment, as shown in FIGS. 11 and 12, the control unit 1 changes the duty of the drive pulse within the pulse application time in accordance with each of the divided N sections, and performs current control. Can be implemented. It should be noted that not only the duty ratio but also the length of each period can be set individually from the first period to the Nth period divided into N sections.

  In the first and second embodiments, the pulse application time is divided into two sections, the first half period and the second half period. When the N division in the third embodiment is associated with the two divisions in the first and second embodiments, for example, the first period corresponds to the first half period, and the second period to the Nth period are the second half. It can be considered to correspond to a period. That is, it can be considered that the second half period is further divided into two or more categories.

  When divided into such sections, individual duty ratios and lengths of periods can be set for the subdivided second half period, and finer control can be performed. Further, when avoiding step-out, a predetermined duty ratio set in advance can be used to specify a period for increasing the duty ratio. When the step-out is detected as described in the first or second embodiment, the control unit 1 performs a predetermined duty ratio set in advance from the second period to the Nth period. By controlling the fuel discharge amount by increasing the duty ratio during a period in which a lower duty ratio is set, the torque shortage can be eliminated and step-out can be avoided.

  For the first to N periods divided into N, the first half period is subdivided from the first period to the Mth period (where M is an integer of 1 ≦ M <N), and the second half period is By subdividing from the (M + 1) period to the Nth period, individual duty ratios and lengths of periods can be set for each of the subdivided periods even in the first half period. It becomes possible to control.

  As described above, according to the third embodiment, the pulse application time can be divided into a plurality of periods of three or more sections, and the current control can be performed by changing the duty of the drive pulse in accordance with each of the plurality of periods. . As a result, the same effects as those of the first and second embodiments can be obtained while increasing the degree of freedom in which the variable setting is possible.

It is a block diagram of the fuel supply control system in Embodiment 1 of this invention. It is a block diagram of the fuel pump in Embodiment 1 of this invention. It is the figure which showed the relationship between the stator of the stepping motor in Embodiment 1 of this invention, and a terminal. It is the figure which showed the energization pattern of the drive pulse in the stepping motor of Embodiment 1 of this invention. It is a schematic diagram of duty ratio setting within one pulse application time in Embodiment 1 of the present invention. It is a control block diagram regarding the control unit in Embodiment 1 of this invention. It is the figure which showed an example of the PWM control duty ratio table with which the PWM duty ratio control means in Embodiment 1 of this invention is provided. It is a block diagram of the fuel supply control system in Embodiment 2 of this invention. In Embodiment 2 of this invention, it is a figure which shows an example which measured the relationship between the duty ratio and fuel pump discharge amount of a second half period. In Embodiment 2 of this invention, it is a figure which shows an example which measured the relationship between the duty ratio and fuel pressure fluctuation amount of a latter half period. It is the figure which showed the energization pattern of the drive pulse in the stepping motor of Embodiment 3 of this invention. It is a schematic diagram of the duty ratio setting within one pulse application time in Embodiment 3 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Control unit, 2 Throttle valve, 3 Throttle position sensor, 4 Engine temperature sensor, 5 Crank angle sensor, 6 Fuel tank, 7 Fuel supply apparatus, 8 Pressure adjustment apparatus, 9 Injector, 10 Pressure sensor, 12, 13 Stator, 14 Coil, 15 rotor magnet, 16 shaft, 19 plate, 20 piston, 21 suction valve, 22 discharge valve, 23 cylinder, 24 plate, 26 suction port, 27 discharge port, 28 spring, 29 pressure increasing chamber, T1-T6 terminals, 101 engine speed calculation means, 102 required fuel injection amount calculation means, 103 drive pulse rate control means, 104 duty ratio control means.

Claims (8)

In a fuel supply control system comprising a control unit for controlling the fuel discharge amount by controlling the rotational speed of the fuel pump motor,
While applying a stepping motor as the fuel pump motor,
The control unit is
Drive pulse rate control means for controlling the drive pulse rate of the pulses for driving the stepping motor according to the required fuel injection amount;
A fuel supply control comprising: PWM duty ratio control means for performing current control by dividing an application time of a drive pulse applied to the stepping motor into a plurality of periods and changing a pulse modulation control duty ratio of each of the plurality of periods system. The fuel supply control system according to claim 1,
The said PWM duty ratio control means sets the duty ratio of the 1st period which is the first period so that it may become higher than the duty ratio of another period, when performing the said current control. The fuel supply control system according to claim 1,
The drive pulse rate control means controls the drive pulse rate to a low frequency when the required fuel injection amount tends to be small. The fuel supply control system according to claim 1,
The drive pulse rate control means controls the drive pulse rate to a high frequency when the required fuel injection amount tends to be large. The fuel supply control system according to claim 1,
The PWM duty ratio control means sets the duty ratio high when starting the stepping motor. The fuel supply control system according to claim 1,
The PWM duty ratio control means sets the duty ratio in a period corresponding to the second half period to be low while the pulse application time is divided into the plurality of periods when the drive pulse rate is a low frequency. Control system. The fuel supply control system according to claim 1,
The PWM duty ratio control means sets the duty ratio low when the engine temperature tends to be high. The fuel supply control system according to claim 1,
The PWM duty ratio control means calculates a fuel pressure fluctuation amount based on a detected pressure value of fuel discharged from a fuel pump, and detects that the fuel pressure fluctuation amount exceeds a predetermined value, thereby detecting a step-out of the stepping motor. When the step-out is detected, the pulse application time is divided into the plurality of periods so that the fuel pressure fluctuation amount is within the predetermined value. A fuel supply control system that controls the current value.

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