JP2007096754A - Load driving circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load driving circuit for detecting circuit grounding regardless of the existence of any resistance. <P>SOLUTION: This load driving circuit is provided with: a load to be driven by a power to be supplied from a power source; a control signal output circuit for outputting a pulse signal for controlling the driving of the load; an intelligent power device for outputting a voltage supplied from the power source to the load as a pulse voltage based on the pulse signal from the control signal output circuit, and for interrupting the pulse voltage in the case of overcurrents; a voltage detecting means for detecting a voltage between the load and the intelligent power device as a monitor voltage; a pulse signal correcting circuit for correcting the pulse signal, based on a current value running through the load; and an abnormality detecting circuit for detecting the grounding of the intelligent power device, based on the whether the monitor voltage is synchronized with the pulse signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a load drive circuit that assists steering force, and more particularly to a load drive circuit that drives a solenoid valve.

Conventionally, a failure diagnosis device for a solenoid valve detects a circuit abnormality by comparing a duty signal for driving the solenoid valve with a monitor voltage on the collector side of the drive transistor. In particular, when a ground fault of a circuit is detected, the monitor voltage becomes zero due to the ground, and therefore a circuit ground fault is determined when the difference between the duty signal and the monitor voltage becomes a predetermined value abnormality.
JP-A-1-244143

  However, the conventional technology has a problem that when a resistance is present at a ground fault location or other locations, the monitor voltage does not become zero and the circuit ground fault cannot be detected.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a load driving circuit capable of detecting a circuit ground fault regardless of the presence of a resistor.

  In order to achieve the above object, in the present invention, a load driven by electric power supplied from a power supply, a control signal output circuit for outputting a pulse signal for driving and controlling the load, and a voltage supplied from the power supply are provided. An intelligent power device that outputs a pulse voltage based on a pulse signal from the control signal output circuit to the load and interrupts the pulse voltage in the event of an overcurrent, and between the load and the intelligent power device. Voltage detection means for detecting a voltage as a monitor voltage, a pulse signal correction circuit for correcting the pulse signal based on a current value flowing through the load, and whether the monitor voltage and the pulse signal are synchronized, And an abnormality detection circuit for detecting a ground fault of the intelligent power device.

  Therefore, it is possible to provide a load drive circuit that prevents erroneous detection of relay abnormality.

  Hereinafter, the best mode for realizing a load driving circuit of the present invention will be described based on an embodiment shown in the drawings.

[System configuration of load drive circuit]
Example 1 will be described with reference to FIGS. FIG. 1 is a system configuration diagram of a vehicle equipped with a load driving circuit of the present application.

  When the driver steers the steering wheel SW, the pinion 3 is driven through the shaft 2, and the rack shaft 4 is moved in the axial direction by a so-called rack and pinion mechanism to steer the front wheels. The rack shaft 4 is provided with a power steering mechanism that assists the movement of the rack shaft 4 according to the steering torque of the driver. The power steering mechanism includes a cylinder 6, a control unit 10 (load drive circuit), a pump P, a hydraulic control valve 1, and a solenoid SOL (load).

  The cylinder 6 is defined in a first cylinder chamber 61 and a second cylinder chamber 62 by a piston 63 provided so as to be movable in the axial direction. The first and second cylinder chambers 61 and 62 are connected to the pump P via the first and second passages 31 and 32 and the hydraulic control valve 1, and the hydraulic oil is introduced from the pump P to move the piston 63 in the axial direction. Move to obtain steering assist force.

  The hydraulic control valve 1 is connected to the torsion bar 5 and adjusts the flow rate to the first and second cylinder chambers 61 and 62 by changing the opening according to the twist direction and the twist amount of the torsion bar 5. Excess hydraulic fluid is returned to the reservoir tank 7. Further, the hydraulic control valve 1 is provided with a solenoid SOL, and controls the opening amount of the hydraulic control valve 1 in accordance with a command from the control unit 10.

  The control unit 10 receives power from the battery E, and receives a switch signal from the ignition IGN, a vehicle speed signal from the vehicle speed sensor 8, and an engine speed signal from the engine speed sensor 9. A steering assist force is determined based on these various signals, and a command signal is output to the solenoid SOL.

[Details of Control Unit]
FIG. 2 is a control block diagram of the control unit 10. The control unit 10 includes a vehicle speed calculation unit 11, an engine speed calculation unit 12, a target current calculation unit 13, a PWM_DUTY determination unit 14 (control signal output circuit and pulse signal correction circuit), an abnormality detection unit 15, a solenoid current detection unit 16, and a terminal. The voltage detection part 17 and the solenoid drive part 100 (intelligent power device) are provided.

  The vehicle speed calculator 11 calculates the vehicle speed VSP, and the engine speed calculator 12 calculates the engine speed Ne and outputs it to the target current calculator 13. The target current calculation unit 13 determines whether the engine has been started (Ne> 0). If the engine has been started, the target current I * is calculated based on the vehicle speed-target current map (see FIG. 4), and PWM_DUTY is determined. To the unit 14.

  The PWM_DUTY determination unit 14 determines PWM_DUTY for the solenoid SOL based on the target current I * and the solenoid actual current I detected by the solenoid current detection unit 16. Based on this, the solenoid drive unit 100 drives the solenoid SOL.

  The terminal voltage detection unit 17 detects the inter-terminal voltage Vr of the solenoid SOL and outputs it to the abnormality detection unit 15. The abnormality detection unit 15 detects an abnormality of the solenoid SOL based on the voltage Vr between the terminals, and outputs a drive prohibition signal to the PWM_DUTY determination unit 14 when an abnormality is detected. The abnormality detection uses a target current-terminal voltage threshold map (see FIG. 5), and when the target current I * is small, the terminal voltage threshold Va is set large.

  In addition, without providing the current detection unit 16, the vehicle speed VSP may be introduced into the abnormality detection unit 15, and the current of the solenoid SOL may be estimated from the value of VSP. In this case, the current detection unit 16 that directly detects the current is not necessary.

[Solenoid drive (details of load drive circuit)]
FIG. 3 is a control block diagram of the solenoid driving unit 100. The solenoid driving unit 100 includes a regulator 110, an overheat protection unit 120, a charge pump 130, a driver 140, and a MOS_FET 150.

  The voltage V from the battery E is boosted by the charge pump 130 after being stabilized by the regulator 110 and introduced into the driver 140. The driver 140 drives the MOS_FET 150 based on PWM_DUTY. Further, the driver 140 limits the current value output to the MOS_FET 150 when the overheat protection unit 120 determines that the overheat state occurs or when an overcurrent flows.

[Solenoid ground fault detection control]
When detecting a ground fault of a circuit, a potential difference between terminals at a detection point is detected, and when this potential difference becomes zero, it is determined that there is a ground fault. If the low potential side at the detection location is grounded and the high potential side voltage is detected, the circuit ground fault can be detected only by measuring the voltage.

  However, when a resistance exists between two detection points, even if a ground fault occurs, the potential difference does not become zero, and a ground fault cannot be detected. In particular, in a circuit that grounds the low potential side of the detection location, even when a resistor exists downstream from the high potential side, detection is similarly impossible.

  Here, when there is a resistance at the detection location, the resistance is short-circuited due to a ground fault, so that the potential difference between terminals decreases. Therefore, in this embodiment, if the voltage Vr between terminals of the solenoid SOL, which is a ground fault detection target, is equal to or higher than the threshold value Va, it is determined that there is no ground fault and is normal. When the state of Vr ≦ Va continues for a certain time ta, it is determined as a ground fault and PWM output is stopped. Although the PWM output is stopped in the present application, a flat signal may be output instead of a pulse signal.

  When a ground fault is detected, the amount of liquid supplied to the cylinder 6 is minimized when the output of the pulse signal is stopped. Therefore, although the steering load during low-speed traveling increases, it is possible to avoid applying an excessive steering assist force during high-speed traveling. In addition, the steering load increases during low-speed traveling, and the driver is notified of the abnormality.

  In addition, since a large current flows during a ground fault and the device generates heat, in the present embodiment, the temperature of the solenoid drive unit 100 is detected by the overheat protection unit 120, and when the detected temperature exceeds a predetermined value, the PWM output To stop. In this case, an overcurrent may be determined by measuring a current value instead of a temperature.

  Further, the solenoid SOL of the present application performs assist force control of the power steering device. Since the assist force becomes small during high speed traveling, the target current I * for the solenoid SOL is also set small. In this case, since the current I * is small, the heat generation at the time of the ground fault is also small, and it is difficult to stop the PWM output by the overheat protection unit 120. Therefore, when the target current I * is small, the threshold value Va of the inter-terminal potential difference V is set high, and the normal margin of the inter-terminal voltage Vr is reduced.

[Solenoid ground fault detection control processing]
FIG. 6 is a flowchart showing the flow of the ground fault detection control process of the solenoid SOL. Hereinafter, each step will be described.

  In step S101, it is determined whether or not the ignition IGN is ON. If YES, the process proceeds to step S102, and if NO, step S101 is repeated.

  In step S102, the engine speed Ne is read, and the process proceeds to step S103.

  In step S103, it is determined whether or not the engine is started (Ne> 0). If YES, the process proceeds to step S104. If NO, step S103 is repeated.

  In step S104, the inter-terminal voltage Vr of the solenoid SOL is read, and the process proceeds to step S105.

  In step S105, the vehicle speed VSP is read, and the process proceeds to step S106.

  In step S106, the target current I * for the solenoid SOL is calculated, and the process proceeds to step S107.

  In step S107, a voltage threshold Va between the terminals of the solenoid SOL is set, and the process proceeds to step S108.

  In step S108, it is determined whether or not the voltage between solenoid terminals Vr ≦ the threshold value Va. If YES, the process proceeds to step S109, and if NO, the process proceeds to step S111.

  In step S109, it is determined whether or not a predetermined time t has elapsed since Vr ≦ Va. If YES, the process proceeds to step S110, and if NO, the process proceeds to step S111.

  In step S110, the PWM output is turned OFF, and the process proceeds to step S113.

  In step S111, PWM_DUTY is calculated, and the process proceeds to step S112.

  In step S112, PWM output is executed, and the process proceeds to step S200.

  In step S200, an overheat protection control process (see FIG. 7) is executed, and the process proceeds to step S113.

  In step S113, it is determined whether or not the ignition IGN is OFF. If YES, the control is terminated, and if NO, the process returns to step S104.

[Overheat protection control processing]
FIG. 7 is a flowchart showing the flow of the overheat protection control process. This corresponds to step S200 in FIG.

  In step S201, it is determined whether or not the temperature T of the solenoid driving unit 100 detected by the overheat protection unit 120 is equal to or higher than the upper limit threshold Th. If YES, the process proceeds to step S202, and if NO, the process proceeds to step S203. .

  In step S202, the PWM output is stopped and the control is terminated.

  In step S203, it is determined whether or not the temperature of the solenoid drive unit 100 is equal to or lower than the lower limit threshold Tl. If YES, the process proceeds to step S205, and if NO, the process proceeds to step S204.

  In step S204, the current PWM output state is continued and the control is terminated.

  In step S205, the PWM output is resumed and the control is terminated.

[Change in solenoid ground fault detection control over time]
FIG. 8 shows the change over time of the solenoid ground fault detection control.
(Time t1)
At time t1, the PWM voltage is turned on.

(Time t2)
At time t2, a ground fault occurs in the solenoid SOL, and the inter-terminal voltage Vr drops below the threshold value Va. The actual current I increases with the ground fault, and the temperature of the solenoid driving unit 100 starts to rise. In addition, time measurement from this point is started by the counter.

(Time t3)
At time t3, the PWM voltage is turned off, the actual current I becomes 0, and the temperature of the solenoid drive unit 100 also decreases.

(Time t4)
At time t4, the PWM signal is turned ON, and the solenoid terminal voltage Vr rises. Moreover, the temperature T also rises by restarting energization.

(Time t5)
At time t5, the temperature of the solenoid driving unit 100 reaches Th, and energization is stopped regardless of the PWM signal.

(Time t6 to t7)
The times t4 to t5 are repeated.

(Time t7)
At time t7, the time from time t2 (at the time of ground fault) becomes ta, it is determined that there is a ground fault, and the output of the PWM signal is stopped.

[Effect of the embodiment of the present application]
In the present embodiment, the PWM_DUTY determination unit 14 that outputs a pulse signal for driving and controlling the solenoid SOL based on the target current I * and the actual current I of the solenoid SOL, and the voltage from the battery E as the pulse signal from the PWM_DUTY determination unit 14 A solenoid driving unit 100 that outputs a pulse voltage based on the voltage to the load and interrupts the pulse voltage in the case of an overcurrent; a terminal voltage detection unit 17 that detects a terminal voltage Vr of the solenoid SOL; and a terminal voltage An abnormality detection unit 15 that detects abnormality of the solenoid SOL based on Vr is provided.

In the embodiment of the present invention, the temperature of the solenoid drive unit 100 is detected by the overheat protection unit 120, and the PWM output is stopped when the detected temperature exceeds a predetermined value because a large current flows at the time of ground fault and the device generates heat. To do. As a result, a ground fault is reliably detected even when a resistance exists at the ground fault location by determining that a ground fault has occurred when the voltage Vr ≦ the threshold value Va of the solenoid SOL continues for a certain period of time ta. can do.
(Other examples)

  The best mode for carrying out the present invention has been described based on the embodiments. However, the specific configuration of the present invention is not limited to each embodiment, and the scope of the invention is not deviated. Design changes and the like are included in the present invention.

  Further, technical ideas other than the claims that can be grasped from the above embodiments will be described below together with the effects thereof.

(A) In the load driving circuit according to claim 1,
The intelligent power device includes temperature detection means,
The load driving circuit, wherein when the temperature detected by the temperature detecting means is equal to or higher than a predetermined value, the output of the pulse signal is stopped.

  Even if the temperature is slightly increased despite being normal, erroneous detection of an abnormality can be avoided.

(B) In the load driving circuit according to claim 1,
The intelligent power device includes temperature detection means,
The load driving circuit, wherein when the temperature detected by the temperature detecting means is equal to or lower than a predetermined value, the output of the pulse signal is stopped.

  Even if the temperature is slightly lowered despite being normal, erroneous detection of abnormality can be avoided.

(C) In the load driving circuit described in (b) above,
The load driving circuit, wherein the detection circuit decreases the predetermined value as a current value flowing through the load is lower.

  When the value of the current flowing through the load is low, the pulse voltage cutoff function of the intelligent power device becomes difficult to operate, and the pulse voltage may not be cut off even at a predetermined time before the end of the ON period of the pulse signal. Even in this case, since the pulse voltage value itself tends to decrease, it is possible to detect a circuit abnormality by detecting a decrease in the pulse voltage value by increasing the predetermined threshold.

(D) The load drive circuit described in (c) above is
A circuit mounted on a vehicle,
The current flowing through the load changes based on the vehicle speed,
The load detection circuit, wherein the abnormality detection circuit estimates the current based on the vehicle speed.

  There is no need to provide a current value detection circuit that directly detects the current value.

(E) In the load driving circuit described in (d) above,
The load driving circuit, wherein the load is an actuator of a power steering device that applies a steering assist force to the steered wheels.

  Since the actuator of the power steering device decreases the current value as the vehicle speed increases, it is possible to appropriately detect a circuit abnormality during high-speed driving.

  (F) In the load drive circuit described in (d) above,

The load is a solenoid for a control valve that controls the amount of liquid supplied to a hydraulic power cylinder that applies a steering assist force to the steered wheels,
As the vehicle speed increases, the current value flowing through the solenoid is decreased,
A load driving circuit, wherein the control valve is controlled so as to reduce the liquid amount as the current value decreases.

  Since the current flowing through the control valve decreases as the vehicle speed increases, it is possible to appropriately detect a circuit abnormality during high-speed traveling.

(G) In the load driving circuit described in (f) above,
The control signal output circuit stops outputting the pulse signal when the abnormality detection circuit detects a circuit abnormality.

  When a circuit abnormality is detected, when the output of the pulse signal is stopped, the control valve minimizes the amount of liquid supplied to the hydraulic power cylinder. Therefore, although the steering load during low-speed traveling increases, it is possible to avoid applying an excessive steering assist force during high-speed traveling. In addition, since the steering load increases during low-speed traveling, it is possible to notify the driver of a circuit abnormality.

1 is a system configuration diagram of a vehicle equipped with a load drive circuit of the present application. It is a control block diagram of a control unit. It is a control block diagram of a solenoid drive unit. It is a vehicle speed-target current map. It is a target current-terminal voltage threshold value map. It is a flowchart which shows the flow of a ground fault detection control process of a solenoid. It is a flowchart which shows the flow of an overheat protection control process. It is a time-dependent change of solenoid ground fault detection control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydraulic control valve 2 Shaft 3 Pinion 4 Rack shaft 5 Torsion bar 6 Cylinder 7 Reservoir tank 8 Vehicle speed sensor 9 Engine speed sensor 10 Control unit 11 Vehicle speed calculation part 12 Engine speed calculation part 13 Target current calculation part 14 PWM_DUTY determination part 15 Abnormality detection unit 16 Solenoid current detection unit 17 Terminal voltage detection units 31 and 32 First and second passages 61 and 62 First and second cylinder chambers 63 Piston 100 Solenoid drive unit 110 Regulator 120 Overheat protection unit 130 Charge pump 140 Driver E Battery IGN Ignition P Pump SOL Solenoid SW Steering wheel

Claims (1)

A load driven by power supplied from a power source;
A control signal output circuit for outputting a pulse signal for driving and controlling the load;
An intelligent power device that outputs the voltage supplied from the power source to the load as a pulse voltage based on a pulse signal from the control signal output circuit, and interrupts the pulse voltage in the event of an overcurrent;
Voltage detection means for detecting a voltage between the load and the intelligent power device as a monitor voltage;
A pulse signal correction circuit for correcting the pulse signal based on a value of a current flowing through the load;
A load drive circuit comprising: an abnormality detection circuit that detects an abnormality of the intelligent power device when the monitor voltage becomes a predetermined threshold value or less.

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