JP2008052564A - Load driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect the temperature of a load driving circuit at low cost making the most of existing constitution without separately providing exclusive parts for temperature detection and furthermore to secure the maximum driving time of the load driving circuit. <P>SOLUTION: A microprocessor 71 comprises a voltage detecting section 71d, a temperature deriving section 71e, a driving time determining section 71f and a solenoid driving control section 71g. The temperature deriving section 71e applies a constant current in the forward direction of a second parasitic diode 82b by a constant current circuit 76 when first and second switching elements 81, 82 are in the OFF state, and derives the temperature of a solenoid driving circuit 73 based on the forward voltage detected by the voltage detecting section 71d. The driving time determining section 71f determines the drivable time of the first switching element 81 based on the temperature at the driving start of the solenoid driving circuit 73 derived by the temperature deriving section 71e, and on the ensured temperature of the first switching element 81. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a load driving device.

  This type of load drive device is connected in series between a load DC power supply and a load to which drive current is supplied from the load DC power supply, and allows only current flowing from the output end side to the input end side. A device having a load driving circuit including a first switching element including a first parasitic diode is known.

  In order to prevent a current from flowing through the load and the first switching element when the load DC power supply is reversely connected, the load is connected in series between the load DC power supply and the first switching element and the first switching element. A device that further includes a second switching element (see Patent Document 1) that is connected in the opposite direction and includes a second parasitic diode that allows only a current flowing from the output end side to the input end side is known.

In such a load driving device, when the load DC power supply is reversely connected to the load, the current application to the load can be cut off, and when the load is normally connected, a voltage is requested from the load without passing through a diode. Therefore, it is possible to prevent a decrease in supply voltage to the load.
German Patent Application Publication No. 3924499A1

  By the way, in the load drive device described above, there is a demand for a longer drive time of the load. In this case, when the energization time to the load is lengthened, the temperature of the first switching element that controls on / off of energization to the load rises due to self-heating due to energization. The guaranteed temperature of the first switching element is defined in advance, and energization of the first switching element must be stopped before the temperature of the first switching element rises and exceeds the upper limit temperature of the guaranteed temperature. The driveable time depends on the upper limit temperature of the guaranteed temperature, the temperature at the start of driving the load (drive start temperature), and the load drive conditions (control pattern; for example, duty ratio in the case of PWM control) It is determined. Since the upper limit temperature of the guaranteed temperature and the drive condition (control pattern) can be grasped in advance, if the drive start temperature can be grasped accurately and accurately, an accurate driveable time can be determined. For example, if the driving start temperature cannot be grasped and the setting is made at the maximum environmental temperature, when the actual temperature is lower than the above-described set value, the control time becomes shorter than necessary. In addition, it is desirable to detect the drive start temperature using an existing configuration as much as possible without separately providing a temperature detection dedicated component (temperature detection means).

  The present invention has been made in order to solve the above-described problems. The load driving is performed at a low cost by utilizing an existing configuration as much as possible without separately providing a temperature detection dedicated component (temperature detection means). It is an object of the present invention to provide a load driving device that can detect the temperature of a circuit with high accuracy and, in turn, can ensure the maximum driving time of the load driving circuit.

  In order to solve the above-mentioned problem, the structural feature of the invention according to claim 1 is that the DC power supply for load and the load to which drive current is supplied from the DC power supply for load are connected in series and output. When a first switching element having a first parasitic diode that allows only a current flowing from an end side (for example, the source of a MOSFET) to an input end side (for example, the drain of a MOSFET) and the load DC power source are reversely connected, In order to prevent a current from flowing through the first switching element, it is connected in series between the load DC power supply and the first switching element and in the opposite direction to the first switching element, and at the output end side (for example, the MOSFET) A second switching element including a second parasitic diode that allows only a current flowing from the source) to the input end side (for example, the drain of the MOSFET); A load driving circuit, a constant current circuit for applying a constant current in the forward direction of the second parasitic diode, a voltage detecting means for detecting a forward voltage of the second parasitic diode, and first and second switching elements. Temperature deriving means for deriving the temperature of the load drive circuit based on the forward voltage detected by the voltage detecting means by applying a constant current in the forward direction of the second parasitic diode when the constant current circuit is in the off state; Driving time determination for determining the drivable time of the first and second switching elements based on the temperature at the start of driving of the load driving circuit derived by the temperature deriving means and the guaranteed temperatures of the first and second switching elements. And the on-off control of the first and second switching elements to control the driving of the load, and the control time of the first and second switching elements A control load drive control means so as not to exceed the determined drive possible time by moving time determining means is that with the.

  The structural feature of the invention according to claim 2 is that for an IC according to claim 1, wherein an existing IC having an A / D function is used as the voltage detection means, and a power supply voltage is supplied to the IC as a power source for the constant current circuit. Is to use a power supply.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the drive time determining means includes the temperature at the start of driving of the load drive circuit derived by the temperature deriving means, the first switching element The driveable time of the first switching element is determined based on the guaranteed temperature and the drive condition of the load.

  In the invention according to claim 1 configured as described above, the temperature deriving means generates a constant current in the forward direction of the second parasitic diode by the constant current circuit when the first and second switching elements are off. Since the temperature of the load drive circuit is derived based on the forward voltage detected by the applied voltage detection means, the existing configuration is used as much as possible without providing a separate temperature detection component (temperature detection sensor). Therefore, the driving start temperature can be accurately grasped at a low cost. The drive time determining means can drive the first and second switching elements based on the temperature at the start of driving the load drive circuit derived by the temperature deriving means and the guaranteed temperatures of the first and second switching elements. And the load drive control means controls so that the control time of the first and second switching elements does not exceed the driveable time determined by the drive time determination means, so that the upper limit of the guaranteed temperature of the load drive circuit The drive time can be accurately determined according to the temperature and the drive start temperature, and the drive time of the load drive circuit can be ensured to the maximum.

  In the invention according to claim 2 configured as described above, in claim 1, an existing IC having an A / D function is used as the voltage detecting means, and a power supply voltage is supplied to the IC as a power source of the constant current circuit. Since the IC power supply is used, the temperature is stable and the temperature can be detected more accurately by using the existing power supply.

  In the invention according to claim 3 configured as described above, in claim 1 or claim 2, the drive time determining means includes the temperature at the start of driving of the load drive circuit derived by the temperature deriving means, and the first switching. Since the driveable time of the first switching element is determined based on the guaranteed temperature of the element and the drive condition of the load, the drive time can be determined more accurately.

  Hereinafter, an embodiment of a vehicle braking device to which a load driving device according to the present invention is applied will be described with reference to the drawings. As shown in FIG. 1, the vehicle braking device A includes a master cylinder 10 that generates a hydraulic pressure corresponding to the depression state of the brake pedal 11, and a left and right front and rear wheels FL of the vehicle that are provided separately from the master cylinder 10. , FR, RL, and RR, and a hydraulic pressure supply source 20 that supplies hydraulic pressure to the wheel cylinders WCfl, WCfr, WCrl, and WCrr, which respectively regulate the rotation of the wheel cylinders.

  When the hydraulic pressure supply source 20 is normal, the hydraulic pressure corresponding to the brake pedal depression force is supplied from the hydraulic pressure supply source 20 to the left and right front and rear wheels FL, FR, RL, RR of the vehicle. When the hydraulic pressure supply source 20 is abnormal, the hydraulic pressure from the hydraulic pressure supply source 20 is not supplied, and the hydraulic pressure corresponding to the brake pedal depression force is supplied from the master cylinder 10 to the left and right front wheels FL, FR of the wheel cylinders WCfl, It is configured to be supplied to WCfr.

  In the vehicular braking apparatus A configured as described above, the stroke simulator 30 for causing the brake pedal 11 to generate a stroke having a magnitude corresponding to the operation state of the brake pedal 11 when the hydraulic pressure supply source 20 is normal. Is installed.

  The vehicle braking device A includes a master cylinder 10 that pumps almost the same hydraulic pressure (hydraulic pressure) of brake oil (liquid) from the first and second output ports 10a and 10b in response to the depression of the brake pedal 11. Yes. The first output port 10a of the master cylinder 10 communicates with the wheel cylinder WCfl for the left front wheel FL via the solenoid valve 41 when the solenoid valve 41 is in a non-energized state (shown state). The second output port 10b of the master cylinder 10 communicates with the wheel cylinder WCfr for the right front wheel FR via the solenoid valve 42 when the solenoid valve 42 is in a non-energized state (shown state).

  The solenoid valves 41 and 42 are controlled to be opened and closed by energization, and communicate and block the master cylinder 10 with respect to the wheel cylinders WCfl and WCfr, respectively. That is, these solenoid valves 41 and 42 are energized and closed when the hydraulic pressure supply source 20 is normal, shuts off between the master cylinder 10 and both wheel cylinders WCfl and WCfr, and deenergized and opened when the fluid pressure supply source 20 is abnormal. It functions as a master cylinder cut valve that communicates the cylinder 10 with both wheel cylinders WCfl, WCfr. The vehicle braking device A includes a pedal stroke sensor 11a that is connected to the brake pedal 11 and detects a movement amount (stroke amount, that is, pedal stroke) of the brake pedal 11.

  A stroke simulator 30 is connected to the first output port 10a of the master cylinder 10 so as to communicate therewith. Between the master cylinder 10 and the stroke simulator 30, an electromagnetic valve 43 and a check valve 44 are provided in parallel. Yes. The stroke simulator 30 is a well-known mechanical stroke simulator as disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-293229, and absorbs hydraulic pressure (hydraulic pressure) supplied from the first output port 10a of the master cylinder 10. To do.

  The solenoid valve 43 shuts off the first output port 10a of the master cylinder 10 and the input port 30a of the stroke simulator 30 when in a non-energized state (shown state), and communicates both ports 10a and 30a when in an energized state. To do. The solenoid valve 43 is energized and opened when the hydraulic pressure supply source 20 is normal, and communicates with the master cylinder 10 and the stroke simulator 30, and is de-energized and closed when abnormal, and the master cylinder 10 and the stroke simulator 30. It functions as a stroke simulator cut valve that shuts off the gap. The check valve 44 is provided in parallel with the solenoid valve 43 between the first output port 10a of the master cylinder 10 and the input port 30a of the stroke simulator 30, and allows only the flow from the stroke simulator 30 to the master cylinder 10. Is.

  The hydraulic pressure supply source 20 includes an electric motor 21, a pump 22, and an accumulator 23. The pump 22 is driven by the electric motor 21 and pumps the brake oil of the reservoir tank 12 sucked from the suction port 22a communicating with the input port 12a of the reservoir tank 12 from the discharge port 22b. The accumulator 23 communicates with the discharge port 22b of the pump 22 so that the high-pressure brake oil supplied from the pump 22 is always kept at a constant hydraulic pressure and stored, and supplied to the wheel cylinders WCfl to WCrr as necessary. It has become. A relief valve 24 is interposed between the intake and discharge ports 22a and 22b of the pump 22, and the relief valve 24 is closed when the pressure of the brake oil discharged from the pump 22 is less than a predetermined value. When the value exceeds a predetermined value, it is opened. Thereby, the hydraulic pressure supply source 20 supplies predetermined high-pressure brake fluid to the wheel cylinders WCfl to WCrr.

  The hydraulic pressure supply source 20 communicates with the wheel cylinder WCfl for the left front wheel FL via the electromagnetic valve 45 when the electromagnetic valve 45 is energized. The electromagnetic valve 45 is a linear solenoid valve that can control the differential pressure between the input and output ports, that is, an electromagnetic valve that generates a differential pressure proportional to the electromagnetic force. The solenoid valve 45 communicates the hydraulic pressure supply source 20 to the wheel cylinder WCfl so that a differential pressure corresponding to the energization amount is in the energized state, and the wheel in the non-energized state (shown state). The hydraulic pressure supply source 20 is shut off with respect to the cylinder WCfl.

  Further, the wheel cylinder WCfl communicates with the reservoir tank 12 via the electromagnetic valve 46 when the electromagnetic valve 46 is in an energized state. The solenoid valve 46 is a linear solenoid valve, similar to the solenoid valve 45 described above. The solenoid valve 46 communicates the wheel cylinder WCfl with the reservoir tank 12 so as to have a differential pressure corresponding to the energization amount when in the energized state, and the reservoir tank 12 when in the non-energized state (shown state). In contrast, the wheel cylinder WCfl is shut off.

  Further, the hydraulic pressure supply source 20 communicates with the wheel cylinder WCfr for the right front wheel FR via the electromagnetic valve 47 when the electromagnetic valve 47 is in an energized state. The solenoid valve 47 is also a linear solenoid valve like the solenoid valve 45. The solenoid valve 47 communicates the hydraulic pressure supply source 20 with the wheel cylinder WCfr so as to have a differential pressure corresponding to the energization amount when energized, and the wheel when not energized (shown). The hydraulic pressure supply source 20 is shut off with respect to the cylinder WCfr.

  Further, the wheel cylinder WCfr communicates with the reservoir tank 12 via the electromagnetic valve 48 when the electromagnetic valve 48 is energized. The solenoid valve 48 is also a linear solenoid valve like the solenoid valve 46. The solenoid valve 48 communicates the wheel cylinder WCfr with the reservoir tank 12 so as to have a differential pressure corresponding to the energization amount when in the energized state, and when not in the energized state (shown state), the reservoir tank 12. In contrast, the wheel cylinder WCfr is shut off.

  Further, the hydraulic pressure supply source 20 communicates with the wheel cylinder WCrl for the left rear wheel RL via the electromagnetic valve 51 when the electromagnetic valve 51 is in an energized state. The solenoid valve 51 is also a linear solenoid valve like the solenoid valve 45. The solenoid valve 51 communicates the hydraulic pressure supply source 20 with the wheel cylinder WCrl so as to have a differential pressure corresponding to the energization amount when energized, and the wheel when not energized (shown). The hydraulic pressure supply source 20 is shut off with respect to the cylinder WCrl.

  Further, the wheel cylinder WCrl communicates with the reservoir tank 12 via the electromagnetic valve 52 when the electromagnetic valve 52 is in a non-energized state (shown state). The solenoid valve 52 is also a linear solenoid valve like the solenoid valve 46. The solenoid valve 52 is controlled to be opened and closed by energization, and shuts off the wheel cylinder WCrl from the reservoir tank 12 when energized.

  Further, the hydraulic pressure supply source 20 communicates with the wheel cylinder WCrr for the right rear wheel RR via the electromagnetic valve 53 when the electromagnetic valve 53 is in an energized state. The solenoid valve 53 is also a linear solenoid valve like the solenoid valve 45. The solenoid valve 53 communicates the hydraulic pressure supply source 20 with respect to the wheel cylinder WCrr so that a differential pressure corresponding to the energization amount when in the energized state, and the wheel when in the non-energized state (shown state). The hydraulic pressure supply source 20 is shut off with respect to the cylinder WCrr.

  Further, the wheel cylinder WCrr communicates with the reservoir tank 12 via the electromagnetic valve 54 when the electromagnetic valve 54 is in a non-energized state (shown state). The solenoid valve 54 is also a linear solenoid valve like the solenoid valve 46. The solenoid valve 54 is controlled to be opened and closed by energization, and shuts off the wheel cylinder WCrr from the reservoir tank 12 when energized.

  In addition, the vehicle braking device A includes oil pressure gauges 61 to 67. The oil pressure gauges 61 and 62 detect the oil pressure of the brake oil supplied from the first and second output ports 10a and 10b of the master cylinder 10, respectively. The oil pressure gauge 63 detects the oil pressure of the brake oil supplied from the hydraulic pressure supply source 20. The hydraulic gauges 64 to 67 detect the hydraulic pressure of the brake oil supplied to and discharged from the wheel cylinders WCfl to WCrr, respectively.

  Further, the vehicle braking device A includes wheel speed sensors Sfl, Sfr, Srl, Srr. Wheel speed sensors Sfl, Sfr, Srl, Srr are attached to the wheels FL, FR, RL, RR, and detect the wheel speeds of the wheels FL, FR, RL, RR and transmit them to the control device 70.

  Further, the vehicle braking device A includes a downhill assist control SW80 that is a switch for turning on / off the downhill assist control of the vehicle. The on / off signal of the downhill assist control SW 80 is transmitted to the control device 70. The downhill assist control is a control for controlling the vehicle speed during the downhill to a constant speed (for example, 5 km / h) by executing the brake control when the downhill assist control SW80 is in the on state.

  The vehicle braking device A includes the pedal stroke sensor 11a, the electric motor 21, the electromagnetic valves 41, 42, 43, 45 to 48, 51 to 54, the hydraulic gauges 61 to 67, and the wheel speed sensors Sfl and Sfr. , Srl, Srr, a control device (for example, a brake control device) 70 is provided. The control device 70 is also connected to a steering sensor that detects the steering angle of the vehicle, an accelerator sensor that is assembled to an accelerator pedal to detect the accelerator opening of the vehicle, and a yaw rate sensor that detects the actual yaw rate Y of the vehicle. (All are not shown). Based on the detection signals from these sensors, the control device 70 controls the electric motor 21 and the electromagnetic valves 41, 42, 43, 45 to 48, 51 to 54 of the vehicle braking device A to control the wheel cylinders WCfl to WCrr. The applied hydraulic pressure, that is, the braking force applied to each wheel FL, FR, RL, RR is controlled.

  As shown in FIG. 2, the control device 70 which is a load driving device includes a microprocessor 71, a solenoid driving unit 72, a solenoid driving circuit (load driving circuit) 73, first and second voltage detection circuits 74 and 75, a constant current. A circuit 76 is provided. In FIG. 2, the solenoid LD indicates only one of the solenoid valves 41 to 43, 45 to 48, and 51 to 54 described above, and only the solenoid drive circuit 73 that drives the solenoid LD. The other solenoids and their solenoid drive circuits are omitted.

  The microprocessor 71 includes a voltage detection unit 71d, a temperature derivation unit 71e, a drive time determination unit 71f, and a solenoid drive control unit (load drive control unit) 71g. The voltage detector 71d detects the forward voltage of the second parasitic diode.

  The temperature deriving unit 71e applies a constant current in the forward direction of the second parasitic diode by the constant current circuit 76 when the second switching element 82 is in the OFF state, and sets the forward voltage detected by the voltage detecting unit 71d. Based on this, the temperature of the solenoid drive circuit 73 is derived.

  The drive time determination unit 71f determines the driveable time of the first switching element 81 based on the temperature at the start of driving of the solenoid drive circuit 73 derived by the temperature deriving unit 71e and the guaranteed temperature of the first switching element 81. decide.

  The solenoid drive control unit 71g controls on / off control of the first and second switching elements 81 and 82 to control the drive of the solenoid LD, and the control time of the first switching element 81 is determined by the drive time determination unit 71f. Control so that the driveable time is not exceeded.

  The solenoid drive unit 72 inputs a control command signal (drive request) from the microprocessor 71 and controls on / off of a drive current (drive voltage) supplied to the solenoid LD to be controlled in accordance with the control command signal. is there. The solenoid driving unit 72 transmits an on / off signal (which may be a PWM signal having a predetermined duty ratio) according to a driving request from the microprocessor 71 to the first to third switching elements 81 to 83 to transmit the on / off signal of the solenoid LD. Control energization / non-energization.

  The solenoid drive circuit 73 includes the first to third switching elements 81 to 83, the solenoid LD, and the battery BAT that is a load DC power source.

  The first switching element 81 is connected in series between a battery (BAT) which is a DC power supply for load and a solenoid LD to which a drive current is supplied from the battery (BAT). The first switching element 81 includes a first parasitic diode 81b that allows only a current flowing from the output end side to the input end side, and is configured by, for example, a MOSFET (MOS field effect transistor). The first switching element 81 includes a first switching unit 81a and a first parasitic diode 81b. The drain (input end) of the first switching unit 81a is connected to one terminal of the solenoid LD. The source (output terminal) of the first switching unit 81 a is connected to the source of the second switching element 82. The gate (signal input terminal) of the first switching unit 81 a is connected to the output port 72 a of the solenoid driving unit 72. The cathode and anode of the first parasitic diode 81b are connected to the drain and source of the first switching unit 81a, respectively.

  The second switching element 82 is connected in series between the battery BAT and the first switching element 81 in order to protect the solenoid LD and the first switching element 81 from the voltage application of the battery BAT when the battery BAT is reversely connected. The first switching element 81 is connected in the opposite direction. The second switching element 82 is configured similarly to the first switching element 81, and includes a second switching unit 82a and a second parasitic diode 82b. The drain (input terminal) of the second switching unit 82a is connected to the negative electrode of the battery BAT, the source (output terminal) of the second switching unit 82a is connected to the source of the first switching unit 81a, and the gate of the second switching unit 82a. The (signal input end) is connected to the output port 72b of the solenoid driving unit 72. The cathode and anode of the second parasitic diode 82b are connected to the drain and source of the second switching unit 82a, respectively.

  The third switching element 83 is a fail-safe switching element and is connected in series between the battery BAT and the solenoid LD. The third switching element 83 is configured similarly to the first switching element 81, and includes a third switching unit 83a and a third parasitic diode 83b. The drain (input end) of the third switching unit 83a is connected to the positive electrode of the battery BAT. The source (output terminal) of the third switching unit 83a is connected to the other terminal of the solenoid LD. The gate (signal input terminal) of the third switching unit 83 a is connected to the output port 72 c of the solenoid driving unit 72. The cathode and anode of the third parasitic diode 83b are connected to the drain and source of the third switching unit 83a, respectively.

  A constant current circuit 76 that applies a constant current in the forward direction of the second parasitic diode 82b is connected between the first and second switching elements 81 and 82 described above. The constant current circuit 76 includes a power source 76a and a resistor 76b. The power source 76a is a power source common to the power source 71a that supplies a power source voltage (for example, 5 V) of the microprocessor 71. Since the power supply 71a supplies a power supply voltage to the microprocessor 71, it is generally a stable power supply voltage with little fluctuation. The resistor 76b has a function of supplying a minute current to the second parasitic diode 82b. The resistor 76b is preferably set to several kΩ so that the second parasitic diode 82b hardly generates heat due to energization, whereby a constant minute current of several mA can be applied to the second parasitic diode 82b.

  The microprocessor 71 has an input port 71b having an A / D conversion function. The input port 71b is connected between the first and second switching elements 81 and 82 via the first voltage detection circuit 74. It is connected. Thereby, the microprocessor 71 detects the voltage between the first and second switching elements 81 and 82 via the first voltage detection circuit 74. Therefore, it is possible to detect whether the second switching element is normal or abnormal, and it is possible to detect the forward voltage of the second parasitic diode 82b. That is, the microprocessor 71 functions as voltage detection means for detecting the forward voltage of the second parasitic diode 82b.

  The first voltage detection circuit 74 is a circuit for detecting the voltage between the first and second switching elements 81 and 82. The first voltage detection circuit 74 includes a resistor 74 a connected in series between the source of the first switching unit 81 a and the input port 71 b of the microprocessor 71.

  The microprocessor 71 has an input port 71c having an A / D conversion function, and the input port 71c is connected between the third switching element 83 and the solenoid LD via the second voltage detection circuit 75. Has been. Thereby, the microprocessor 71 detects the voltage between the third switching element 83 and the solenoid LD via the second voltage detection circuit 75. Therefore, it can be detected whether the third switching element is normal or abnormal.

  The second voltage detection circuit 75 is a circuit for detecting a voltage between the third switching element 83 and the solenoid LD. The second voltage detection circuit 75 includes a resistor 75a connected in series between the source of the third switching unit 83a and the input port 71c of the microprocessor 71, and between the input port 71c (resistor 75a) and the ground GND. And a resistor 75b connected in series.

  Next, an example of the operation of the vehicle braking device A configured as described above will be described. First, brake fluid pressure control will be described. The control device 70 calculates a wheel speed Vw based on detection signals from the wheel speed sensors Sfl to Sfr every predetermined time, calculates a wheel acceleration DVw from the wheel speed Vw, and based on the wheel speed Vw of the four wheels. When the vehicle body speed Vs is calculated and it is detected that the stop switch 14 is turned on and brake braking is being performed, an optimal control is applied to each wheel so that the difference between the wheel speed Vw and the vehicle body speed Vs does not exceed a predetermined value. Implement ABS control to give power.

  Specifically, the control device 70 controls the pressure-increasing linear valve 45 and the pressure-reducing linear valve so as to control the fluid pressure to an optimum hydraulic pressure by the pair of pressure-increasing linear valves 45 and pressure-reducing linear valves 46 assigned to the wheels FL. 46 is excited / de-energized according to the fluid pressure. Other wheels are similarly controlled. Further, during the ABS control, the solenoid LD is energized and the pumps 23 and 33 are controlled to operate.

  Moreover, the control apparatus 70 can implement downhill assist control. Downhill assist control is a comfortable convenience that allows the driver to concentrate on steering the steering wheel while maintaining a predetermined speed by operating on scenes that are difficult to go down by driver operation in off-road areas or downhill on snowy roads It is a function.

  The downhill assist control SW 80 is turned on, operates without operation of the brake pedal 11 and the accelerator pedal (not shown), and the driver determines that acceleration / deceleration is desired and operates the brake pedal 11 and the accelerator pedal (not shown). Then, even if the downhill assist control SW 80 is not turned off, it is interrupted. In addition, the wheel cylinders of the respective wheels are increased or decreased based on the difference between the wheel speed and the vehicle body speed so as to maintain a predetermined speed.

  That is, in the downhill assist control, when the control device 70 detects that the downhill assist control SW 80 is turned on, the wheel speed sensors Sfl to Sfr at predetermined time intervals when the driver does not operate the brake pedal 11. The vehicle speed Vs is estimated based on the wheel speed Vw of the four wheels, and an optimum braking force is applied to each drive wheel so that the vehicle speed Vs does not exceed a predetermined speed. Yes. That is, similarly to the ABS control described above, the control device 70 controls the optimal hydraulic pressure with each pair of wheels by controlling the optimal hydraulic pressure with a pair of pressure increasing linear valves and pressure reducing linear valves assigned to the wheels. Has been granted.

  In any control, during the control, the electromagnetic valves 41 and 42 are excited to function as a cut valve. Further, the electromagnetic valve 43 is excited to function as a valve for communicating the master cylinder 10 and the stroke simulator 30. That is, among all the solenoid valves, the solenoid valves 41, 42 and 43 are solenoid valves having the longest energization time during the control.

  The operation of the solenoid valves 41 and 42 and the solenoid drive circuit for these solenoid valves 41 and 42 will be described in detail. The electromagnetic valve 41 will be described as an example. When the control device 70 turns on all of the first to third switching elements 81 to 83, the voltage of the battery BAT is applied to the solenoid LD, and the electromagnetic valve 41 is excited to be closed. Further, when the control device 70 turns off all of the first to third switching elements 81 to 83, the voltage of the battery BAT is not applied to the solenoid LD, and the electromagnetic valve 41 is de-energized to be in an open state.

  When the battery BAT is reversely connected, the second switching element 82 is turned off. At this time, the second parasitic diode 82b cuts off the current.

  Next, the case where the temperature of the solenoid drive circuit 73 is derived and the solenoid valve 41 is controlled based on the derived result will be described. First, the temperature deriving unit 71e of the control device 70 applies a constant current in the forward direction of the second parasitic diode 82b by the constant current circuit 76 when the first and second switching elements 82 are in the OFF state. At this time, the voltage detector 71d detects the forward voltage of the second parasitic diode 82b. The temperature deriving unit 71e of the control device 70 is based on the forward voltage detected by the voltage detecting unit 71d and the temperature characteristic map of the forward voltage stored in the microprocessor 71 in advance (see FIG. 3). Deriving the temperature. For example, if the forward voltage is Vf1, the temperature of the solenoid drive circuit 73 is Th1. This temperature derivation is preferably performed before the start of control of the solenoid LD. If the control of the solenoid LD is not yet started, the temperature of the solenoid drive circuit 73 is substantially the same as the environmental temperature of the solenoid drive circuit 73, so deriving the temperature of the solenoid drive circuit 73 derives the environmental temperature. That is.

  The first to third parasitic diodes 81b to 83b generally exhibit characteristics as shown in FIG. The forward voltage increases as the ambient temperature decreases. When the ambient temperature is 100 ° C., 25 ° C., and −40 ° C., the forward voltages are Va, Vb, and Vc, respectively. Therefore, the forward voltage temperature characteristic map shown in FIG. 3 is such that when the constant current Ir flows, the forward voltage increases as the ambient temperature decreases. That is, for example, it has a slope of about −2 mV / ° C. The horizontal axis and the vertical axis are temperature and voltage, respectively.

  The drive time determination unit 71f is a temperature at the start of driving of the solenoid drive circuit 73 derived by the temperature deriving unit 71e (drive start temperature), a guaranteed temperature of the first switching element 81, that is, a drive end temperature, and a drive condition of the solenoid LD. Based on the above, the driveable time of the first switching element 81 (second switching element 82) is determined.

  For example, when the drive start temperature is 50 ° C., the guaranteed temperature of the first switching element 81 is 150 ° C., and the drive condition is always energized, the map shows the relationship between the drive condition stored in advance and the temperature increase rate. The temperature rise rate is derived from the drive conditions based on the above, and the drivable time is determined from the derived result, the drive start temperature, and the drive end temperature. The driveable time in this case is shown in FIG. 5 as T1. The drivable time is the time from the start of driving to the end of driving, and is the time taken for the temperature of the solenoid drive circuit 73 to reach the driving end temperature from the driving start temperature. The driving conditions are a control pattern and a duty ratio.

  In the case where the guaranteed temperatures and the heat generation temperatures of the first and second switching elements 81 and 82 are different, the drivable time which is shorter in time until the guaranteed temperature is reached earlier may be employed.

  The solenoid drive control unit 71g controls on / off of the first and second switching elements 81 and 82 to control the drive of the solenoid LD, and the control time of the first switching element 81 is controlled by the drive time determining unit 71f. Control is performed so that the determined driveable time is not exceeded. The third switching element 83 is turned off at the time of failure.

  As is apparent from the above description, according to the present embodiment, the temperature deriving means (temperature deriving portion 71e) is operated by the constant current circuit 76 when the first and second switching elements 81 and 82 are in the off state. Since a constant current is applied in the forward direction of the two parasitic diodes 82b and the temperature of the load drive circuit 73 is derived based on the forward voltage detected by the voltage detection means (voltage detection unit 71d), the temperature detection dedicated component ( Without providing a separate temperature detection sensor, the drive start temperature can be accurately grasped at low cost by using an existing configuration as much as possible. The driving time determining means (driving time determining section 71f) determines the temperature at the start of driving of the load driving circuit 73 derived by the temperature deriving means (temperature deriving section 71e) and the guaranteed temperature of the first and second switching elements 81 and 82. Based on the above, the driveable time of the first and second switching elements 81 and 82 is determined, and the load drive control means (solenoid drive control unit 71g) controls the control time of the first and second switching elements 81 and 82. Is controlled so as not to exceed the drivable time determined by the drive time determining means (driving time determining unit 71f). Therefore, the drivable time according to the upper limit temperature and the drive start temperature of the guaranteed temperature of the load drive circuit 73 is controlled. Can be accurately determined, and the drive time of the load drive circuit 73 can be ensured to the maximum.

  If temperature detection is not performed, the drive start temperature may be set to 100 ° C. in advance in anticipation of a thermal safety margin (see FIG. 5). In this case, the driving time is T2. In this case, when the actual temperature is lower than the driving start temperature, there is a situation in which driving is stopped although there is a margin in temperature. For example, when the drive start temperature is 50 ° C., the drive time is T1 longer than T2. According to the present embodiment, the solenoid drive circuit 73 can be controlled in an appropriate drive time by accurately measuring the drive start temperature.

  Further, an existing IC (microprocessor 71) having an A / D function is used as the voltage detection means (voltage detection unit 71d), and an IC power supply 71a that supplies a power supply voltage to the IC is used as the power supply 76a of the constant current circuit 76. Since it is used, the driving start temperature can be detected more accurately by using a stable voltage and using an existing power source.

  Further, the drive time determining means (drive time determining section 71f) includes the temperature at the start of driving of the load drive circuit 73 derived by the temperature deriving means (temperature deriving section 71e), the guaranteed temperature of the first switching element 81, and the load Since the driveable time of the first switching element 81 is determined on the basis of the drive conditions, the drive time can be ensured to the maximum.

  In the above-described embodiment, the second switching element 82 is connected in series between the negative electrode of the load DC power supply (battery BAT) and the first switching element 81. However, the load DC power supply (battery BAT) and the first switching element 81 may be connected in series. According to this, the second switching element 82 is connected in series between the positive electrode of the load DC power supply (battery BAT) and the first switching element 81, and the load DC power supply (battery BAT) is used as a power supply for the constant current circuit. ) Or the second voltage detection circuit 75 can be used to determine the current. Therefore, the temperature deriving unit (temperature deriving unit 71e) applies the voltage of the load DC power supply (battery BAT) in the forward direction of the second parasitic diode 82b when the second switching element 82 is in the OFF state, and the voltage detecting unit. The temperature of the load drive circuit 73 can be derived based on the forward voltage detected by the (voltage detection unit 71d).

  In the embodiment described above, the present invention is applied to the solenoid drive circuit, but may be applied to a motor drive circuit.

It is a figure which shows the outline | summary of one Embodiment of the braking device for vehicles to which the load drive device by this invention is applied. It is a general | schematic block diagram which shows the control apparatus shown in FIG. It is a temperature characteristic map of the forward voltage of a parasitic diode. It is a voltage-current characteristic map for every temperature of a parasitic diode. It is a figure which shows the temperature change during the drive of a solenoid drive circuit.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Master cylinder, 10a ... 1st output port, 10b ... 2nd output port, 11 ... Brake pedal, 11a ... Pedal stroke sensor, 12 ... Reservoir tank, 12a ... Input port, 20 ... Fluid pressure supply source, 21 ... Electricity Motor, 22 ... Pump, 22a ... Suction port, 22b ... Discharge port, 23 ... Accumulator, 24 ... Relief valve, 30 ... Stroke simulator, 30a ... Input port, 41-43 ... Solenoid solenoid valve, 45-48, 51-54 ... Solenoid valve (linear solenoid solenoid valve), 44 ... Check valve, 61-67 ... Hydraulic gauge, 70 ... Control device (load drive device), 71 ... Microprocessor, 71a ... Power supply for IC, 71d ... Voltage detector ( Voltage detecting means), 71e... Temperature deriving section (temperature deriving means), 71f... Driving time determining section (driving time determining means), 71 ... Solenoid drive control unit (load drive control means), 72 ... Solenoid drive unit, 73 ... Solenoid drive circuit (load drive circuit), 74 ... First voltage detection circuit, 75 ... Second voltage detection circuit, 76 ... Constant current circuit 76a ... Power supply, 80 ... Downhill assist control SW, 81-83 ... First to third switching elements, 81a-83a ... First to third switching units, 81b-83b ... First to third parasitic diodes, A ... Vehicle braking device, WCfl to WCrr ... wheel cylinder, BAT ... battery (DC power supply for load), LD ... solenoid (load).

Claims (3)

Connected in series between the load DC power supply (BAT) and the load (LD) to which drive current is supplied from the load DC power supply (BAT), and allows only current flowing from the output end side to the input end side In order to prevent a current from flowing to the load and the first switching element when the first switching element (81) including the first parasitic diode (81b) and the load DC power supply are reversely connected to each other, A second parasitic diode (82b) that is connected in series between the DC power supply for load and the first switching element in a direction opposite to the first switching element and allows only current flowing from the output end side to the input end side. A second switching element (82) comprising a load drive circuit (73) comprising:
A constant current circuit (76) for applying a constant current in the forward direction of the second parasitic diode;
Voltage detecting means (71d) for detecting a forward voltage of the second parasitic diode;
Based on the forward voltage detected by the voltage detection means by applying a constant current in the forward direction of the second parasitic diode by the constant current circuit when the first and second switching elements are off. Temperature deriving means (71e) for deriving the temperature of the load driving circuit;
The drivable time of the first and second switching elements is determined based on the temperature at the start of driving of the load driving circuit derived by the temperature deriving means and the guaranteed temperature of the first and second switching elements. Drive time determining means (71f);
The first and second switching elements are turned on / off to control the driving of the load, and the drivable time determined by the driving time determining means is determined by the control time of the first and second switching elements. And a load drive control means (71g) for controlling so as not to exceed the load drive device. In claim 1, using an existing IC (71) having an A / D function as the voltage detection means,
An IC power source (71a) for supplying a power source voltage to the IC is used as a power source (76a) for the constant current circuit.   3. The drive time determining means according to claim 1, wherein the drive time determining means is a temperature at the start of driving the load drive circuit derived by the temperature deriving means, a guaranteed temperature of the first switching element, and a drive condition for the load. A load driving device that determines a driveable time of the first switching element based on

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