JP5900369B2 - Solenoid valve drive - Google Patents

Description

  The present invention relates to a solenoid valve driving device.

  For example, as a fuel injection valve (injector) that injects fuel into a cylinder of an internal combustion engine mounted on a vehicle, an electromagnetic valve that is opened by energization of a coil is used. The fuel injection control device that controls the fuel injection by driving the fuel injection valve controls the fuel injection timing and the fuel injection amount by controlling the energization (the energization start timing and the energization time) to the coil. doing.

  In the fuel injection control device, the power supply voltage is boosted to charge the capacitor, and at the start of the energization period of the coil (which is also the drive period for opening the fuel injection valve), the capacitor is discharged to the coil. Thus, a peak current for quickly moving (lifting) the valve body of the fuel injection valve is caused to flow through the coil. From the end of the discharge from the capacitor to the coil until the end of the energization period, the power supply voltage is controlled by performing switching control to turn on / off the transistor provided between the upstream side of the coil and the power supply voltage. A constant current is passed through the coil. In the switching control, for example, the current flowing through the coil (hereinafter also referred to as coil current) is detected, and when the coil current is detected to be lower than the lower threshold, the transistor is switched from OFF to ON, and the coil current is increased to the upper threshold When it is detected that (> lower threshold) or more, the transistor is switched from on to off. For this reason, the average value of the coil current is controlled to a current between the upper threshold value and the lower threshold value (see, for example, Patent Document 1).

JP 2009-22139 A

  In the fuel injection control device, the control circuit that performs the switching control detects the arrival of the coil current to the upper threshold value, and changes the drive signal to the transistor from the on-side active level to the off-side inactive level. Even after switching, the coil current continues to increase until the transistor actually turns off. Similarly, even if the control circuit detects the arrival of the lower threshold value of the coil current and switches the drive signal to the transistor from the inactive level to the active level, the coil current remains until the transistor is actually turned on. Continue to decrease.

  For this reason, when a constant current flows through the coil, even if the coil current reaches the upper threshold, the amount still changes in the same direction (increase direction) and exceeds the upper threshold (hereinafter referred to as the upper threshold excess amount). Arise. Similarly, even if the coil current reaches the lower threshold value, it still changes in the same direction (decreasing direction) and an amount exceeding the lower threshold value (hereinafter referred to as the lower threshold excess amount) is also generated.

The upper threshold excess amount and the lower threshold excess amount vary.
For example, a transistor turn-off time (time required to shift from an on state to an off state) and a turn-on time (time required to shift from an off state to an on state) have positive temperature characteristics. Therefore, the higher the ambient temperature of the transistor, the longer the turn-off time and turn-on time of the transistor, and the larger the upper threshold excess amount and the lower threshold excess amount.

  For example, the upper threshold excess amount and the lower threshold excess amount also vary depending on the power supply voltage. This is because, even if the turn-off time of the transistor is constant, when the power supply voltage increases, the rate of increase of the coil current during the on-period of the transistor increases, so the upper threshold excess amount increases. Even if the turn-on time of the transistor is constant, if the power supply voltage increases, the maximum value of the pulsating coil current increases, so the rate of decrease in the coil current during the transistor off period increases, and the lower threshold excess amount Also grows.

Here, when variation occurs in at least one of the upper threshold excess amount and the lower threshold excess amount, the pulsation width (difference between the maximum value and the minimum value) of the coil current varies.
When the pulsation width of the coil current varies, the coil current at the end of the energization period varies.

  Furthermore, if the coil current varies at the end of the energization period, the valve closing delay time (the delay time until the valve body returns to the valve closing position) after the energization period ends until the fuel injection valve closes varies. As a result, the control accuracy of the fuel injection valve is reduced. In addition, if the solenoid valve to be driven is a fuel injection valve, the specific problem is that the fuel injection amount varies.

  Then, this invention aims at improving the control precision of a solenoid valve in a solenoid valve drive device.

  The solenoid valve driving device of the present invention is provided in series between the upstream side of the coil in the energization path for flowing current to the coil of the solenoid valve and a power supply line to which a power supply voltage is supplied. A constant current switching element that is turned on / off to allow a constant current to flow through the coil, an energization period setting unit that sets an energization period to the coil, and the on / off of the constant current switching element in the energization period. The constant current control means for allowing a constant current to flow through the coil and the threshold value changing means are provided.

  The constant current control means is given a threshold value for switching the switching element for constant current from the first state that is one of on and off to the second state that is the other of on and off. When the constant current control means detects that the current flowing through the coil has reached the threshold when the constant current switching element is in the first state during the switching control, the constant current control means The switching element is switched from the first state to the second state.

  Further, the threshold value changing means detects a physical quantity that changes in the same direction even when the current flowing through the coil reaches the threshold value and has a correlation with an excess threshold value that is an amount exceeding the threshold value, and according to the physical quantity The threshold value is changed.

  According to this solenoid valve drive device, when the change direction of the coil current when the constant current switching element is in the first state is the first change direction, the extreme value of the first change direction of the coil current is the physical quantity. It is possible to prevent the desired value from being exceeded due to the change in.

  From this, it is possible to prevent the pulsation width of the coil current from becoming larger than the desired standard value due to the change in the physical quantity. As a result, the variation in the coil current at the end of the energization period is desired. It can prevent becoming larger than a standard value. For this reason, it is possible to suppress variations in the valve closing delay time from the end of the energization period to the closing of the solenoid valve. Therefore, the control accuracy of the solenoid valve is improved.

  For example, when the first state is on and the second state is off, the threshold is an off switching threshold for switching the constant current switching element from on to off. In this case, the following configuration is better.

  That is, the constant current control means is also given an on switching threshold value smaller than the off switching threshold value as a threshold value for switching the constant current switching element from off to on. When it is detected that the coil current has reached the on-switching threshold while the current switching element is turned off, the constant current switching element is switched from off to on. The threshold value changing means also changes the ON switching threshold value in accordance with the physical quantity.

  According to this configuration, it is possible to prevent the pulsation width of the coil current from becoming larger than the desired standard value and the average value of the coil current from being out of the desired standard range due to the change in the physical quantity. easy. This is because the extreme values in both the increasing direction and the decreasing direction of the coil current (that is, both the maximum value and the minimum value) can be controlled to desired values even if the physical quantity changes.

It is a block diagram which shows the fuel-injection control apparatus of embodiment. It is explanatory drawing explaining operation | movement of IC for a drive. It is a 1st figure explaining the reason which changes an upper side threshold value and a lower side threshold value. It is a 2nd figure explaining the reason which changes an upper side threshold value and a lower side threshold value. It is a flowchart showing a threshold value setting process. It is explanatory drawing explaining the relationship between the battery voltage VB, the upper side threshold value IthH, and the lower side threshold value IthL. It is explanatory drawing explaining the relationship between ECU internal temperature, the upper side threshold value IthH, and the lower side threshold value IthL.

A fuel injection control device as an electromagnetic valve driving device of an embodiment will be described with reference to the drawings.
The fuel injection control device of the present embodiment includes four electromagnetic solenoid injectors that supply fuel to each cylinder # 1 to # 4 of a multi-cylinder (in this example, four cylinders) gasoline engine mounted on an automobile. (Hereinafter referred to as electromagnetic valves), and by controlling the energization start timing and energization time to the coils of each solenoid valve, the fuel injection timing and fuel injection amount to each cylinder # 1 to # 4 are controlled. Control. In the present embodiment, the transistor as the switching element is, for example, a MOSFET, but may be another type of transistor such as a bipolar transistor or IGBT (insulated gate bipolar transistor).

  As shown in FIG. 1, an electronic control unit (hereinafter referred to as ECU) 31 that is a fuel injection control unit includes a terminal CM to which one end (upstream side) of a coil 41a of an electromagnetic valve 41 that is a drive target is connected, and a coil A terminal INJ to which the other end (downstream side) of 41a is connected; a transistor T10 having one output terminal connected to the terminal INJ; and a current detection connected between the other output terminal of the transistor T10 and the ground line. Resistance R10.

  The solenoid valve 41 is a normally closed solenoid valve. In the solenoid valve 41, when the coil 41a is energized, a valve body (not-shown nozzle needle) (not shown) moves to the valve opening position (in other words, lifts), and fuel injection is performed. When the energization of the coil 41a is interrupted, the valve body returns to the original valve closing position, and fuel injection is stopped.

  FIG. 1 shows only one solenoid valve 41 corresponding to the nth cylinder #n (n is any one of 1 to 4) out of the four solenoid valves 41. The driving of the electromagnetic valve 41 will be described. Actually, the terminal CM is a common terminal for the solenoid valve 41 of each cylinder, and the coil 41a of each solenoid valve 41 is connected to the terminal CM. The terminal INJ and the transistor T10 are provided for each electromagnetic valve 41 (in other words, for each cylinder). The transistor T10 is a switching element for selecting the electromagnetic valve 41 to be driven (in other words, the cylinder to be injected), and is called a cylinder selection switch.

  Furthermore, the ECU 31 includes a transistor T11 as a constant current switching element having one output terminal connected to a power supply line Lp to which a battery voltage (vehicle battery voltage) VB as a power supply voltage is supplied, and the other of the transistors T11. A backflow preventing diode D11 having an anode connected to the output terminal and a cathode connected to the terminal CM, a current return diode D12 having an anode connected to the ground line and a cathode connected to the terminal CM, and a booster A circuit 33.

The diode D12 causes a current to flow back to the coil 41a when the transistor T11 is turned off from the on state while the transistor T10 is turned on.
The step-up circuit 33 is a step-up DC / DC converter, and drives the capacitor C0, the inductor L0, the step-up transistor T0, the backflow prevention diode D0, the current detection resistor R0, and the transistor T0. A charge control circuit 35.

  The capacitor C0 accumulates electric energy for causing the coil 41a to flow a peak current for quickly moving (lifting) the valve body of the electromagnetic valve 41 in the valve opening direction. The inductor L0 has one end connected to the power supply line Lp and the other end connected to one output terminal of the transistor T0. The resistor R0 is connected between the other output terminal of the transistor T0 and the ground line. One end (positive side) of the capacitor C0 is connected to the connection point between the inductor L0 and the transistor T0 via the diode D0, and the other end (negative side) of the capacitor C0 is connected to the connection point between the transistor T0 and the resistor R0. Has been.

  In the booster circuit 33, when the transistor T0 is turned on / off, a flyback voltage (back electromotive voltage) higher than the battery voltage VB is generated at the connection point between the inductor L0 and the transistor T0. Capacitor C0 is charged through diode D0. For this reason, the capacitor C0 is charged with a voltage higher than the battery voltage VB.

  The charge control circuit 35 operates when the charge permission signal given to the circuit 35 is at an active level (eg, high in this embodiment), and the voltage on the positive side of the capacitor C0 (hereinafter referred to as the capacitor voltage) VC. The transistor T0 is turned on / off so that becomes a preset target voltage (> VB).

  The charge control circuit 35 monitors the capacitor voltage VC and also monitors the charging current of the capacitor C0 based on the voltage generated in the resistor R0, and turns on / off the transistor T0 so that the capacitor C0 is charged in an efficient cycle. . Then, when the capacitor voltage VC reaches the target voltage, the charging control circuit 35 keeps the transistor T0 off and stops charging the capacitor C0. For this reason, the capacitor C0 is charged so that the capacitor voltage VC, which is the charging voltage thereof, becomes the target voltage.

  Further, the ECU 31 recovers energy by connecting a transistor T12 as a discharge switching element for connecting the positive electrode side of the capacitor C0 to the terminal CM, an anode connected to the terminal INJ, and a cathode connected to the positive electrode side of the capacitor C0. By controlling the diode D13 and the transistors T10, T11, and T12, a driving IC 37 that controls the current flowing through the coil 41a and a microcomputer (microcomputer) 39 are provided.

  The microcomputer 39 includes a CPU 51 that executes a program, a ROM 52 that stores programs, fixed data, and the like, a RAM 53 that stores calculation results by the CPU 51, an A / D converter (ADC) 54, and the like.

  The microcomputer 39 generates an injection command signal for each cylinder based on engine operation information detected by various sensors (not shown) such as the engine speed, the accelerator opening, and the engine water temperature. Output to.

  The injection command signal means that the coil 41a of the solenoid valve 41 is energized (in other words, opens the solenoid valve 41) only when the level of the signal is an active level (eg, high in this embodiment). ing. For this reason, the microcomputer 39 sets an energization period to the coil 41a of the solenoid valve 41 for each cylinder based on the engine operation information, and sets the injection command signal of the corresponding cylinder to high only during the energization period. It can be said.

  The driving IC 37 includes a cylinder selection control circuit 55 that controls the transistor T10, a discharge control circuit 56 that controls the transistor T12, a constant current control circuit 57 that controls the transistor T11, and a microcomputer 39 via a serial communication line 58. A serial / parallel converter 59 that converts the threshold data sent to parallel data and applies the converted data to the constant current control circuit 57.

  When the injection command signal S # n of the nth cylinder #n output from the microcomputer 39 becomes high, the cylinder selection control circuit 55 keeps the nth cylinder #n while the injection command signal S # n is high. The transistor T10 corresponding to the electromagnetic valve 41 is turned on.

  When the injection command signal S # n becomes high, the discharge control circuit 56 turns on the transistor T12 for a predetermined time tp, for example, to discharge the coil 41a of the solenoid valve 41 of the nth cylinder #n from the capacitor C0. In this case, current flows through a path of “capacitor C0 → transistor T12 → coil 41a → transistor T10 → resistor R10 → ground line”. Thus, the current flowing from the capacitor C0 to the coil 41a is the aforementioned peak current.

  As another example, the discharge control circuit 56 detects a coil current (current flowing in the coil 41a) from the voltage generated in the resistor R10, and causes the transistor T12 to be turned into a coil current after the injection command signal S # n becomes high. Until the peak current reaches the target maximum value.

The constant current control circuit 57 performs constant current control for flowing a constant current through the coil 41a of the solenoid valve 41 using the battery voltage VB as a power source while the injection command signal S # n is high.
The constant current control is control that allows a constant current to flow through the coil 41a by performing switching control that repeatedly turns on and off the transistor T11. In this embodiment, the transistor T11 is turned off when it is detected that the coil current has increased to the upper threshold value IthH, and the transistor T11 is turned on when it is detected that the coil current has decreased to the lower threshold value IthL. Is the control.

  In the constant current control, when the transistor T11 is on, a current flows from the battery voltage VB (power supply line Lp) to the coil 41a. Further, when the transistor T11 is turned off, a current flows (circulates) through the coil 41a from the ground line side through the diode D12.

  The upper threshold (hereinafter simply referred to as threshold) IthH is larger than the lower threshold (hereinafter also referred to simply as threshold) IthL. The upper threshold IthH is an off-switching threshold for switching the transistor T11 from on to off, and the lower threshold IthL is an on-switching threshold for switching the transistor T11 from off to on. In the present embodiment, the upper threshold value IthH and the lower threshold value IthL are variable.

Therefore, the constant current control circuit 57 includes an amplifier circuit 61, a D / A converter (DAC) 62, a comparator 63, an AND circuit 64, and a drive circuit 65.
The amplifier circuit 61 outputs a voltage proportional to the potential difference between both ends of the resistor R10. For this reason, the amplifier circuit 61 outputs a voltage proportional to the coil current.

  The comparator 63 compares the output voltage Vi of the amplifier circuit 61 with the output voltage Vo of the D / A converter 62. The output signal of the comparator 63 is high when “Vo> Vi” and low when “Vo <Vi”. Further, when “Vo = Vi”, the output signal of the comparator 63 is, for example, a level opposite to the level before “Vo = Vi”, but before “Vo = Vi”. You may maintain the level.

The AND circuit 64 outputs a logical product signal of the injection command signal S # n from the microcomputer 39 and the output signal of the comparator 63.
When the output signal San of the AND circuit 64 is high, the drive circuit 65 sets the drive signal Sd supplied to the gate of the transistor T11 to an active level, turns on the transistor T11, and the output signal San of the AND circuit 64 is When it is low, the drive signal Sd is set to an inactive level, and the transistor T11 is turned off. In the present embodiment, since the transistor T11 is a P-channel type MOSFET, the active level of the drive signal Sd is, for example, 0V, and the inactive level of the drive signal Sd is, for example, the battery voltage VB.

Threshold value data sent from the microcomputer 39 to the driving IC 37 via the serial communication line 58 is input to the D / A converter 62 via the serial / parallel converter 59.
The threshold data includes upper threshold data representing an upper threshold voltage VthH corresponding to the upper threshold IthH of the coil current, and lower threshold data representing a lower threshold voltage VthL corresponding to the lower threshold IthL of the coil current. There is.

  If the output voltage Vi of the amplifier circuit 61 is a voltage obtained by multiplying the value of the coil current by G (G is a positive number), the relationship between the upper threshold voltage IthH and the upper threshold voltage VthH is “VthH = IthH × G The relationship between the lower threshold value IthL and the lower threshold voltage VthL is also “VthL = IthL × G”.

  The D / A converter 62 stores the latest upper threshold data and lower threshold data from the microcomputer 39. When the output signal San of the AND circuit 64 is high, the D / A converter 62 outputs the upper threshold voltage VthH represented by the upper threshold data to the comparator 63, and the output signal San of the AND circuit 64. When is low, the lower threshold voltage VthL represented by the lower threshold data is output to the comparator 63.

  In such a constant current control circuit 57, when the injection command signal S # n becomes high, the coil current is initially smaller than both the upper threshold value IthH and the lower threshold value IthL. The output signal San of the AND circuit 64 also becomes high. Then, the drive signal Sd from the drive circuit 65 to the transistor T11 becomes active level to turn on the transistor T11, and the output voltage Vo of the D / A converter 62 becomes the upper threshold voltage VthH.

  Thereafter, if the coil current increases to the upper threshold value IthH, the output signal of the comparator 63 changes from high to low, and the output signal San of the AND circuit 64 also changes to low. Then, the drive signal Sd becomes an inactive level, and the transistor T11 is turned off, and the output voltage Vo of the D / A converter 62 becomes the lower threshold voltage VthL.

  Thereafter, if the coil current decreases to the lower threshold value IthL, the output signal of the comparator 63 goes from low to high, and the output signal San of the AND circuit 64 also goes high. Then, the drive signal Sd becomes an active level to turn on the transistor T11, and the output voltage Vo of the D / A converter 62 becomes the upper threshold voltage VthH.

  Therefore, the constant current control circuit 57 switches the transistor T11 to OFF when the comparator 63 detects that the coil current has increased and has reached the upper threshold value IthH while the transistor T11 is ON, When the comparator 63 detects that the coil current has decreased and has reached the lower threshold value IthL while the transistor T11 is turned off, the transistor T11 is switched on. The constant current control circuit 57 performs constant current control by repeating such an operation. Further, the upper threshold data and the lower threshold data transmitted from the microcomputer 39 to the driving IC 37 correspond to data for instructing the constant current control circuit 57 to specify the upper threshold IthH and the lower threshold IthL.

  When the injection command signal S # n becomes low, in the constant current control circuit 57, the output signal San of the AND circuit 64 becomes low and the drive signal Sd becomes inactive level. Thus, the transistor T11 remains off.

  On the other hand, for example, when the injection command signal for each cylinder from the microcomputer 39 is low (that is, when fuel injection is not performed), the driving IC 37 sets the charge permission signal to the charge control circuit 35 to high. Thus, the capacitor voltage VC is set to the target voltage.

  The ECU 31 also includes two resistors 71 and 72 that divide the battery voltage VB into a voltage that can be input by the microcomputer 39. A voltage generated at a connection point between the resistors 71 and 72 and divided from the battery voltage VB (hereinafter referred to as a divided voltage) is input to the microcomputer 39. The microcomputer 39 A / D-converts the divided voltage by the resistors 71 and 72 by the A / D converter 54 and detects the battery voltage VB from the A / D conversion value.

  Further, the ECU 31 has a thermistor 73 having one end connected to the ground line, and a pull-up resistor 74 having one end connected to the other end of the thermistor 73 and a constant power supply voltage (for example, 5V) applied to the other end. And.

  The thermistor 73 is a resistor whose resistance value changes according to temperature, and is mounted in the vicinity of the transistor T11 (for example, a position adjacent to the transistor T11) inside the ECU 31. Therefore, the resistance value of the thermistor 73 changes according to the internal temperature of the ECU 31 (hereinafter also referred to as the ECU internal temperature) corresponding to the ambient temperature of the transistor T11.

  A voltage generated at the connection point between the thermistor 73 and the resistor 74 (hereinafter referred to as a temperature monitor voltage) changes according to the ECU internal temperature, and the temperature monitor voltage is input to the microcomputer 39. The microcomputer 39 A / D converts the temperature monitor voltage by the A / D converter 54 and detects the ECU internal temperature from the A / D conversion value. For example, the microcomputer 39 converts the A / D conversion value of the temperature monitor voltage into the ECU internal temperature using a data map or calculation formula prepared in advance in the ROM 52.

Next, the operation of the ECU 31 will be described using the time chart of FIG.
As shown in FIG. 2, when the injection command signal S # n from the microcomputer 39 goes from low to high, in the driving IC 37, the cylinder selection control circuit 55 turns on the transistor T10, and at the same time, the discharge control circuit 56 turns on the transistor Turn on T12.

  Then, the capacitor C0 is discharged to the coil 41a, and this discharge starts energization of the coil 41a. Moreover, the valve opening response of the solenoid valve 41 is accelerated by the peak current that is the discharge current from the capacitor C0 to the coil 41a. When the capacitor C0 is discharged, the wraparound from the terminal CM side to the power supply line Lp side, which becomes a high potential, is prevented by the diode D11.

  When a certain time tp has elapsed since the injection command signal S # n becomes high, the discharge control circuit 56 turns off the transistor T12. As described above, the control may be such that the transistor T12 is turned off when the coil current reaches the target maximum value of the peak current.

  When the transistor T12 is turned off, the coil current decreases. When the coil current decreases to the lower threshold value IthL, thereafter, the constant current control of the constant current control circuit 57 described above causes the coil current average value to be a constant current between the upper threshold value IthH and the lower threshold value IthL. Thus, the transistor T11 is turned on / off. The target constant current that flows to the coil 41a by this constant current control is smaller than the maximum value of the peak current.

  As shown in FIG. 2, the transistor T11 is turned on until the coil current reaches the upper threshold value IthH after the injection command signal S # n becomes high. This is due to constant current control. However, since the capacitor voltage VC is higher than the battery voltage VB, a current flows from the capacitor C0 to the coil 41a during the period in which the transistor T12 is on, even if the transistor T11 is on. For this reason, the constant current control is actually started after the transistor T12 is turned off. Thus, for example, the constant current control circuit 57 may start an operation for constant current control when the transistor T12 is turned off after the injection command signal S # n becomes high. .

  Thereafter, when the injection command signal S # n changes from high to low, the cylinder selection control circuit 55 turns off the transistor T10, and the constant current control circuit 57 also stops constant current control and turns off the transistor T11. Then, energization of the coil 41a is stopped, the electromagnetic valve 41 is closed, and fuel injection by the electromagnetic valve 41 is finished.

  Further, when the injection command signal S # n becomes low and the transistor T10 and the transistor T11 are turned off, flyback energy is generated in the coil 41a. The flyback energy is supplied to the capacitor C0 through the diode D13. Recovered in the form.

  If the solenoid valve 41 can be reliably opened by passing a peak current from the capacitor C0 to the coil 41a, the target constant current to be passed to the coil 41a by constant current control is the opening of the solenoid valve 41. Any hold current may be used as long as it generates a minimum electromagnetic force necessary for holding the valve.

  Further, the constant current control circuit 57 may be configured to switch a target constant current to be passed through the coil 41a by constant current control between two levels of magnitude. Specifically, for example, a period from when the injection command signal S # n becomes high until a predetermined time elapses is defined as a lift period for reliably opening the solenoid valve 41. The constant current control circuit 57 causes the pickup current larger than the hold current to flow in the coil 41a in the constant current control from when the transistor T12 is turned off until the lift period ends. The pickup current is a current for ensuring that the solenoid valve 41 is opened. In addition, the constant current control circuit 57 causes the hold current to flow through the coil 41a in the constant current control from the end of the lift period until the injection command signal S # n becomes low.

  In this embodiment, in order to simplify the explanation, it is assumed that the constant current by constant current control is only the hold current. However, as described above, the constant current is switched between the pickup current and the hold current. Also good.

  Here, in the present embodiment, as shown in FIG. 2, for example, the microcomputer 39 performs serial communication via the serial communication line 58 to the driving IC 37 before making the injection command signal S # n high. The upper threshold data and the lower threshold data are transmitted.

  Then, the microcomputer 39 detects the battery voltage VB and the ECU internal temperature, and changes the upper threshold data and the lower threshold data to be transmitted to the driving IC 37 according to the detection results, whereby the constant current control circuit The upper threshold value IthH and the lower threshold value IthL commanded to 57 are changed.

  In FIG. 2, in the left half example, the upper threshold value IthH and the lower threshold value IthL commanded from the microcomputer 39 to the constant current control circuit 57 are “IH1” and “IL1”, respectively. Then, the upper threshold value IthH and the lower threshold value IthL are “IH2” and “IL2”, respectively.

  Further, in the left half and the right half in FIG. 2, the coil current is exemplified on the assumption that the battery voltage VB and the ECU internal temperature are the same, and the response delay with respect to the drive signal Sd of the transistor T11 is zero. Yes. Therefore, the constant current (specifically, the average value of the coil current) flowing through the coil 41a seems to change by changing the upper threshold value IthH and the lower threshold value IthL in the left half and the right half in FIG. Is shown in FIG.

  On the other hand, the change of the upper threshold value IthH and the lower threshold value IthL in this embodiment (that is, the change of the upper threshold value IthH and the lower threshold value IthL according to the battery voltage VB and the ECU internal temperature) is a constant current flowing through the coil 41a. It is not a change for changing, but a change for preventing the coil current from changing.

Next, the reason why the upper threshold value IthH and the lower threshold value IthL are changed will be described with reference to FIGS.
As shown in FIG. 3, the transistor T11 has a turn-off time Toff from when the drive signal Sd changes from the active level to the inactive level until it turns off, and the drive signal Sd changes from the inactive level to the active level. There is a turn-on time Ton from when to turn on.

  Therefore, even if the constant current control circuit 57 detects that the coil current reaches the upper threshold value IthH and switches the drive signal Sd from the active level to the inactive level, the coil current increases until the transistor T11 is turned off. Keep doing. Similarly, even if the constant current control circuit 57 detects that the coil current reaches the lower threshold value IthL and switches the drive signal Sd from the inactive level to the active level, the coil current is not changed until the transistor T11 is turned on. Continue to decrease.

  Therefore, when a constant current is passed through the coil 41a by the constant current control, even if the coil current reaches the upper threshold value IthH, the amount still changes in the same increasing direction and exceeds the upper threshold value IthH (hereinafter referred to as the upper threshold excess amount). ) IovH occurs. Similarly, even if the coil current reaches the lower threshold value IthL, an amount IovL that changes in the same decreasing direction and exceeds the lower threshold value IthL (hereinafter referred to as the lower threshold excess amount) IovL also occurs.

  The turn-off time Toff and the turn-on time Ton of the transistor T11 have positive temperature characteristics. Therefore, the higher the ambient temperature of the transistor T11, the longer the turn-off time Toff and the turn-on time Ton, and the upper threshold excess amount IovH and the lower threshold excess amount IovL increase.

  Even if the turn-off time Toff is constant, when the battery voltage VB increases, the increase rate of the coil current during the ON period of the transistor T11 increases, and thus the upper threshold excess amount IovH increases. Even if the turn-on time Ton is constant, if the battery voltage VB increases, the maximum value of the pulsating coil current increases, so that the rate of decrease of the coil current during the off period of the transistor T11 increases, and the lower threshold value The excess amount IovL also increases.

Thus, the upper threshold excess amount IovH and the lower threshold excess amount IovL also vary depending on the battery voltage VB.
Here, when the upper threshold value IthH and the lower threshold value IthL are fixed and at least one of the upper threshold excess amount IovH and the lower threshold excess amount IovL varies, the pulsation width (maximum value and minimum value) of the coil current occurs. Difference). Then, when the pulsation width of the coil current varies, as shown in FIG. 4, the coil current at the end of the energization period (that is, when the injection command signal S # n changes from high to low) becomes I1, I2, I3 will vary.

  If the coil current varies at the end of the energization period, the valve closing delay time from the end of the energization period until the solenoid valve 41 closes varies, and the control accuracy of the solenoid valve 41 decreases. . As a specific problem, the fuel injection amount varies.

  For example, it is assumed that the state in which the battery voltage VB is 14V and the ambient temperature of the transistor T11 (hereinafter also simply referred to as ambient temperature) is 25 ° C. is the standard state. The case where the battery voltage VB and the ambient temperature are higher than the standard state is referred to as the first state, and conversely, the case where the battery voltage VB and the ambient temperature are lower than the standard state is referred to as the second state. Then, the coil current in the standard state is as shown by a solid line in FIG. 4, the coil current in the first state is as shown by a one-dot chain line in FIG. 4, and the coil current in the second state is shown in FIG. Suppose that it looks like a dotted line. Furthermore, as shown in FIG. 4, it is assumed that the drive signal S # n changes from high to low at the timing when the coil current reaches the maximum value in each of the standard state, the first state, and the second state. .

  In the example of FIG. 4, the coil current at the end of the energization period is I3 larger than I2 in the standard state in the first state, and I1 smaller than I2 in the second state. For this reason, in the first state, the closing timing of the electromagnetic valve 41 is delayed from the standard state, and in the second state, the closing timing of the electromagnetic valve 41 is earlier than the standard state.

  In FIG. 4, for convenience, the minimum value of the coil current pulsating by the constant current control is shown to be the same in the standard state, the first state, and the second state, but the actual minimum value is , “Value in second state> value in standard state> value in first state”.

  Therefore, in the ECU 31 of the present embodiment, the microcomputer 39 performs the threshold setting process of FIG. 5 at regular intervals, for example, according to the ECU internal temperature corresponding to the ambient temperature of the transistor T11 and the battery voltage VB. The upper threshold value IthH and the lower threshold value IthL used in the constant current control are changed.

  As shown in FIG. 5, when starting the threshold setting process, the microcomputer 39 first detects the battery voltage VB from the divided voltage by the resistors 71 and 72 in S110, and in the next S120, monitors the temperature by the thermistor 73. The ECU internal temperature is detected from the voltage.

  Then, in the next S130, the microcomputer 39 determines an upper threshold value IthH and a lower threshold value IthL to be instructed to the constant current control circuit 57 according to the detected battery voltage VB and ECU internal temperature.

  Specifically, first, for example, the ROM 52 stores a threshold setting map that represents the relationship among the battery voltage VB, the ECU internal temperature, the upper threshold IthH, and the lower threshold IthL.

  In the threshold setting map, the relationship between the battery voltage VB and the thresholds IthH and IthL is, for example, as shown in FIG. 6, the higher (larger) the battery voltage VB, the smaller the upper threshold IthH and the lower threshold IthL. In addition, the relationship between the threshold values IthH and IthL (IthH−IthL) is set to be small. Further, in the threshold setting map, as for the relationship between the ECU internal temperature and the thresholds IthH and IthL, for example, as shown in FIG. 7, the upper threshold IthH and the lower threshold IthL are smaller as the ECU internal temperature is higher (larger). And the relationship between the two threshold values IthH and IthL is set to be small.

  In S130, the microcomputer 39 calculates thresholds IthH and IthL corresponding to the battery voltage VB detected in S110 and S120 and the ECU internal temperature from the threshold setting map, and sets the calculated thresholds IthH and IthL. The threshold values IthH and IthL to be commanded to the current control circuit 57 are determined. Then, the threshold value setting process ends.

  The microcomputer 39 includes upper threshold data representing the upper threshold voltage VthH corresponding to the upper threshold IthH determined in S130, and lower threshold data representing the lower threshold voltage VthL corresponding to the lower threshold IthL determined in S130. Is transmitted to the driving IC 37. In this embodiment, the threshold values IthH and IthL are changed as shown in FIGS. 6 and 7, so that the maximum value and the minimum value of the pulsating coil current are changed to the battery voltage VB and the ambient temperature of the transistor T11. Regardless, it is made constant.

  Further, as another example of S130, the microcomputer 39, for example, sets a correction coefficient corresponding to the battery voltage VB and an ECU internal temperature for each of the standard value IthHs of the upper threshold value IthH and the standard value IthLs of the lower threshold value IthL. The threshold values IthH and IthL to be instructed to the constant current control circuit 57 may be calculated by multiplying by a correction coefficient corresponding to.

  In this case, a map for determining the correction coefficient KvH to be multiplied by the standard value IthHs among the correction coefficients corresponding to the battery voltage VB may be set as shown by a one-dot chain line in FIG. 6, for example, and multiplied by the standard value IthLs. For example, the map for determining the correction coefficient KvL may be set like a two-dot chain line in FIG. Similarly, a map for determining the correction coefficient KtH to be multiplied by the standard value IthHs among the correction coefficients corresponding to the ECU internal temperature may be set as shown by a one-dot chain line in FIG. 7, for example, and multiplied by the standard value IthLs. The map for determining the correction coefficient KtL may be set as indicated by a two-dot chain line in FIG. In this example, for example, if the threshold values IthH and IthL in the standard state are the standard values IthHs and IthLs, the maps for determining the correction coefficients KvH, KvL, KtH, and KtL are in the standard state. In this case, the correction coefficients KvH, KvL, KtH, and KtL may be set to “1”.

On the other hand, the solenoid valves 41 other than the nth cylinder #n are also driven by the same configuration and processing as described above.
As described above, the ECU 31 uses the threshold value IthH, which is used in the constant current control, in accordance with the physical quantity correlated with the upper threshold excess amount IovH and the lower threshold excess amount IovL (in the above example, the battery voltage VB and the ECU internal temperature). IthL is changed.

  For this reason, in the constant current control, it is possible to prevent the maximum value and the minimum value of the pulsating coil current from exceeding a desired value due to the change in the physical quantity. From this, it is possible to prevent the pulsation width of the coil current from becoming larger than the desired standard value due to the change in the physical quantity, and further, the fluctuation of the coil current at the end of the energization period is desired. It can prevent becoming larger than a standard value. Therefore, the variation in the valve closing delay time from the end of the energization period to the closing of the solenoid valve 41 can be suppressed, and the control accuracy of the solenoid valve 41 and thus the control accuracy of fuel injection are improved.

  In addition, the configuration may be such that one of the threshold values IthH and IthL is changed according to the physical quantity. However, when both the threshold values IthH and IthL are changed, the pulsation width of the coil current becomes larger than a desired standard value. It is easy to prevent both of this and the average value of the coil current from deviating from the desired standard range. This is because both the maximum value and the minimum value of the coil current can be controlled to desired values.

  Also, the upper threshold excess amount IovH and the lower threshold excess amount IovL are more likely to change according to the physical quantity, so that only one of the threshold values IthH and IthL is determined according to the physical quantity. If variable, the upper threshold value IthH is preferably variable.

  Even when only the upper threshold value IthH is made variable among the threshold values IthH and IthL, the upper threshold value IthH may be changed with the change characteristics as shown in FIGS. By doing so, the maximum value of the coil current can be made constant. Further, since the maximum value of the coil current can be prevented from increasing as the battery voltage VB and the ambient temperature of the transistor T11 increase, the average value of the coil current is prevented from becoming larger than a desired upper limit value. can do.

  On the other hand, only the lower threshold value IthL may be made variable among the threshold values IthH and IthL. In this case, for example, the lower threshold value IthL may be set to increase as the battery voltage VB increases and the ECU internal temperature increases, contrary to the change characteristics shown in FIGS. By doing so, the minimum value of the coil current can be made constant. As described above, the higher the battery voltage VB and the higher the internal temperature of the ECU, the larger the lower threshold excess amount IovL (that is, the amount by which the minimum value of the coil current is lower than the lower threshold IthL).

  When both the threshold values IthH and IthL are made variable, there is a premise that “IthH> IthL”. Therefore, as shown in FIGS. 6 and 7, the lower threshold value IthL is also set in the battery voltage VB and the ECU. The temperature is changed with the same decreasing tendency as the upper threshold value IthH. However, the decreasing slope of the lower threshold value IthL is made gentler than the decreasing slope of the upper threshold value IthH, thereby preventing the minimum value of the coil current from becoming too small. That is, the higher the battery voltage VB and the ECU internal temperature, the smaller the thresholds IthH and IthL, and the smaller the difference between the thresholds IthH and IthL, the coil current pulsation width becomes larger than the standard value. And that the average value of the coil current is outside the standard range can be prevented.

[Modification 1]
In the above embodiment, the threshold values IthH and IthL are linearly changed according to the physical quantity as shown in FIGS.

  For this reason, if the battery voltage VB is taken as an example of the physical quantity, the difference between each of the threshold values IthH and IthL and the threshold values IthH and IthL is greater than that when the battery voltage VB is the first value (for example, 14V). However, the case where the battery voltage VB is a second value (for example, 32 V) higher than the first value is smaller.

As a method for realizing this, for example, the following methods <1> and <2> may be considered.
<1> In a region where the battery voltage VB is lower than a specific value between the first value and the second value, each of the threshold values IthH and IthL is constant, and in a region where the battery voltage VB is equal to or higher than the specific value. The difference between each of the threshold values IthH and IthL and the threshold values IthH and IthL is reduced as the battery voltage VB increases as shown in FIG.

  <2> The difference between each of the threshold values IthH and IthL and the threshold values IthH and IthL is different between a region where the battery voltage VB is lower than the specific value and a region where the battery voltage VB is equal to or higher than the specific value. Switch. That is, it switches to two steps.

The methods <1> and <2> are the same for the ECU internal temperature.
[Modification 2]
In the constant current control performed by the constant current control circuit 57, among the conditions for switching on / off the transistor T11, for example, the condition for switching the transistor T11 from off to on is that a predetermined time has elapsed since the transistor T11 was turned off. It may be the condition that. In this case, there is no lower threshold value IthL, and the upper threshold value IthH is made variable. Conversely, the condition for switching the transistor T11 from on to off may be a condition that a predetermined time has elapsed since the transistor T11 was turned on. In this case, there is no upper threshold value IthH, and the lower threshold value IthL is made variable.

[Modification 3]
The physical quantity as a parameter for changing the threshold values IthH and IthL may be either one of the battery voltage VB and the ambient temperature (ECU internal temperature) of the transistor T11, or may be other than these.

[Modification 4]
In an automobile, when the ECU 31 is provided in an engine room 75 (see FIG. 1) in which the engine of the automobile is housed, the microcomputer 39 sets the temperature of the engine room 75 as the ECU internal temperature (by extension, the transistor It may be detected as the ambient temperature of T11). This is because there is a correlation between the temperature of the engine room 75 and the ECU internal temperature.

For example, if there is a temperature sensor that detects the temperature of the engine room 75, the microcomputer 39 can detect the temperature of the engine room 75 from the output of the temperature sensor.
Further, the microcomputer 39 detects the temperature of a specific object whose temperature correlates with the temperature of the engine room 75 as the temperature of the engine room 75 (and thus as the ambient temperature of the transistor T11). You may do it.

  As the specific thing, the fuel supplied to an engine, the engine oil of an engine, the cooling water of an engine, etc. can be considered, for example. These temperatures are usually detected by the sensors 76, 77, and 78 (see FIG. 1) for other purposes in the automobile, so that signals from the sensors 76 to 78 are input to the microcomputer 39. Thus, detection can be performed without adding a separate sensor.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to such Embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement in a various aspect. .

  For example, the microcomputer 39 may perform part or all of what the driving IC 37 performs. The engine provided with the electromagnetic valve 41 to be driven may be a diesel engine. The electromagnetic valve 41 to be driven is not limited to an injector (fuel injection valve), and may be, for example, an electromagnetic valve of a fuel pump.

  In addition, within the scope of the contents described in the claims, a modification that changes any combination or a modification that deletes a part of the configuration and processing of the embodiment and the modification described above may be performed. Of course it is possible. For example, a configuration that does not discharge the capacitor C0 to the coil 41a may be used.

  31 ... ECU, 39 ... microcomputer, 41 ... solenoid valve, 41a ... coil, CM ... terminal, Lp ... power supply line, T11 ... transistor, 57 ... constant current control circuit

Claims (7)

Provided in series between the upstream side (CM) of the coil in the energization path for flowing current to the coil (41a) of the solenoid valve (41) and the power supply line (Lp) to which the power supply voltage is supplied. , A constant current switching element (T11) that is turned on / off to allow a constant current to flow through the coil;
Energization period setting means (39) for setting an energization period to the coil;
Constant current control means (57) for allowing a constant current to flow through the coil by performing switching control for repeatedly turning on and off the constant current switching element during the energization period;
In the electromagnetic valve drive device (31) comprising:
The constant current control means is provided with a threshold value for switching the constant current switching element from a first state that is one of on and off to a second state that is the other of on and off, During the switching control, when the constant current switching element is in the first state, if it is detected that the current flowing through the coil has reached the threshold value, the constant current switching element is Switching from the state to the second state,
The electromagnetic valve driving device is
Even if the current flowing through the coil reaches the threshold value, the threshold value is changed in the same direction and detected as a physical quantity correlated with the threshold excess quantity that exceeds the threshold value, and the threshold value is changed according to the physical quantity. Means (39, S110 to S130) ,
The first state is on and the second state is off;
The threshold is an off switching threshold for switching the constant current switching element from on to off,
The constant current control means is also given an on switching threshold smaller than the off switching threshold as a threshold for switching the constant current switching element from off to on, and during the execution of the switching control, When the constant current switching element is turned off, when it is detected that the current flowing through the coil has reached the on switching threshold, the constant current switching element is switched from off to on. And
The threshold value changing means also changes the on-switching threshold value according to the physical quantity,
The physical quantity is one or both of the power supply voltage and the ambient temperature of the constant current switching element,
The threshold value changing means sets each of the off-switching threshold value and the on-switching threshold value to a second value whose physical quantity is larger than the first value than when the physical quantity is a first value. In some cases, change to be smaller,
A solenoid valve driving device characterized by the above. In the electromagnetic valve drive device according to claim 1 ,
The threshold value changing means is configured such that the difference between the off-switching threshold value and the on-switching threshold value is greater when the physical quantity is the second value than when the physical quantity is the first value. To make it smaller,
A solenoid valve driving device characterized by the above. In the solenoid valve driving device according to claim 1 or 2 ,
The physical quantity is at least an ambient temperature of the constant current switching element,
The threshold value changing means detects the internal temperature of the electromagnetic valve driving device as the ambient temperature;
A solenoid valve driving device characterized by the above. Provided in series between the upstream side (CM) of the coil in the energization path for flowing current to the coil (41a) of the solenoid valve (41) and the power supply line (Lp) to which the power supply voltage is supplied. , A constant current switching element (T11) that is turned on / off to allow a constant current to flow through the coil;
Energization period setting means (39) for setting an energization period to the coil;
Constant current control means (57) for allowing a constant current to flow through the coil by performing switching control for repeatedly turning on and off the constant current switching element during the energization period;
In the electromagnetic valve drive device (31) comprising:
The constant current control means is provided with a threshold value for switching the constant current switching element from a first state that is one of on and off to a second state that is the other of on and off, During the switching control, when the constant current switching element is in the first state, if it is detected that the current flowing through the coil has reached the threshold value, the constant current switching element is Switching from the state to the second state,
The electromagnetic valve driving device is
Even if the current flowing through the coil reaches the threshold value, the threshold value is changed in the same direction and detected as a physical quantity correlated with the threshold excess quantity that exceeds the threshold value, and the threshold value is changed according to the physical quantity. Means (39, S110 to S130),
The first state is on and the second state is off;
The threshold is an off switching threshold for switching the constant current switching element from on to off,
The constant current control means is also given an on switching threshold smaller than the off switching threshold as a threshold for switching the constant current switching element from off to on, and during the execution of the switching control, When the constant current switching element is turned off, when it is detected that the current flowing through the coil has reached the on switching threshold, the constant current switching element is switched from off to on. And
The threshold value changing means also changes the on-switching threshold value according to the physical quantity,
The physical quantity is the ambient temperature of the constant current switching element, or both the ambient temperature and the power supply voltage,
The threshold value changing means detects the internal temperature of the electromagnetic valve driving device as the ambient temperature;
A solenoid valve driving device characterized by the above. In the electromagnetic valve driving device according to claim 3 or 4 ,
The electromagnetic valve driving device is provided in an engine room in which an automobile engine is stored in an automobile,
The threshold value changing means detects the temperature of the engine room as an internal temperature of the electromagnetic valve driving device;
A solenoid valve driving device characterized by the above. In the electromagnetic valve drive device according to claim 5 ,
The threshold value changing means detects a temperature of a specific object, the temperature of which is correlated with the temperature of the engine room, as the temperature of the engine room;
A solenoid valve driving device characterized by the above. In the electromagnetic valve drive device according to claim 6 ,
The object is at least one of fuel supplied to the engine, engine oil of the engine, and cooling water of the engine;
A solenoid valve driving device characterized by the above.

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