JP2019182233A - Steering control device - Google Patents

Abstract

To provide a steering control device which can control overheat protection at further proper timing even if a temperature detection part fails.SOLUTION: A microcomputer 31 of a steering control device 30 has an assist control part 70 for calculating a fundamental current command value Ia*, an overheat protection control part 71 and a temperature calculation part 72. The overheat protection control part 71 calculates a current command value I* in which an absolute value of the fundamental current command value Ia* is limited to a current limit value. The overheat protection control part 71 changes the current limit value on the basis of a thermistor temperature Ts which is detected by a thermistor 60. When an ignition key is turned on in a state where the thermistor 60 fails, the overheat protection control part 71 calculates the current limit value by using a control post-start temperature Te which is calculated by a temperature calculation part 72. The temperature calculation part 72 sets a control start temperature on the basis of an intake air temperature Ti when the ignition key is turned on, and an atmospheric temperature To.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a steering control device.

  An electric power steering device (hereinafter referred to as “EPS”) that assists a driver's steering operation by applying a motor torque to a steering mechanism of a vehicle is known (Patent Document 1). The EPS includes a steering control device that controls power supply to the motor. A board on which a switching element, a thermistor, and the like are mounted is provided inside the steering control device. A switching element for controlling power supply to the motor generates heat. Further, the motor generates heat due to the influence of copper loss, iron loss, and the like during driving. In the steering control device described in Patent Literature 1, an internal temperature that is an internal temperature of the steering control device is detected through temperature detection by a thermistor. The steering control device performs overheat protection control that suppresses overheating of the steering control device or the motor (particularly the switching element) based on the internal temperature. The steering control device restricts power supply to the motor when the internal temperature exceeds a temperature threshold set from the viewpoint of overheat protection. Thereby, overheating of a motor is suppressed and overheating of a switching element is suppressed. By the way, the thermistor may break down. The steering control device cannot determine whether or not the overheat protection control is to be executed when the thermistor has failed. Therefore, in the steering control device described in Patent Document 1, when it is determined that the thermistor has failed, power supply to the motor is limited.

  For example, in the steering control device disclosed in Patent Document 2, when the ignition switch is turned on in a state where the thermistor has failed, the internal temperature at that time is set on the assumption, and the motor temperature is set with respect to the assumed temperature. The subsequent internal temperature is estimated by taking into account the temperature change caused by heat generation and heat dissipation associated with driving. However, in such a steering control device, when the ignition switch is turned on, it is impossible to grasp how the motor was driven during the period when the ignition switch was turned on last time. For this reason, the steering control device cannot grasp the temperature change caused by the heat generation and the heat radiation accompanying the driving of the motor during the period when the ignition switch was previously turned on, and cannot estimate the appropriate internal temperature. . Therefore, in the steering control device of Patent Document 2, it is disclosed that when the ignition switch is turned on, the internal temperature is set assuming a correspondingly high temperature in order to reliably prevent the motor from overheating.

JP 2008-230540 A JP 2008-195246 A

  The correspondingly high temperature is set, for example, from the viewpoint of ensuring that overheat protection can be performed. However, the internal temperature when the ignition switch is turned on varies depending on the traveling state before the ignition switch is turned off, the period from when the ignition switch is turned on to when it is turned on, and the like. Therefore, there is a corresponding difference between the assumed internal temperature of the steering control device and the actual internal temperature, which are set to execute the overheat protection control when the ignition switch is turned on when the thermistor is broken. May occur. In particular, as the time elapsed after the ignition switch is turned off, the internal temperature decreases toward the outside air temperature, so that the difference between the assumed temperature and the actual internal temperature increases. Therefore, in spite of the fact that it is not actually necessary to execute overheat protection, the power supply to the motor is limited, and the assistance of the steering operation by the driver may be interrupted early. As described above, when the ignition switch is turned on in a state where the thermistor has failed, there is room for improvement as to how the overheat protection control is executed assuming the internal temperature.

  A steering control device that solves the above-described problem is a steering control device that controls power supply to a motor that applies torque to a steering mechanism of a vehicle, and a temperature detection unit that detects an internal temperature that is an internal temperature of the steering control device; And controlling the power supply to the motor when the internal temperature detected by the temperature detector is equal to or higher than a temperature threshold that requires overheat protection to restrict the power supply to the motor. And when the ignition switch is turned on in a state where the temperature detection unit is out of order, the control unit estimates a decrease in the internal temperature immediately after the ignition switch is turned off. A control start temperature when the ignition switch is turned on based on possible vehicle information is set, and the control start temperature is set based on the control start temperature. Estimating the internal temperature to be used in the control of the thermal protection.

  According to the above configuration, when the ignition switch is turned on while the temperature detection unit is out of order, the steering control device can estimate the vehicle temperature decrease state immediately after the ignition switch is turned off. Based on this, the control start temperature is set. Considering vehicle information that can estimate the internal temperature drop state after the ignition switch is turned off, the control start temperature can be set close to the actual internal temperature when the ignition switch is turned on become. Accordingly, overheat protection control can be executed based on the internal temperature estimated using the control start temperature. Therefore, when the ignition switch is turned on while the temperature detection unit is out of order, the internal temperature can be estimated more appropriately, so that overheat protection control can be executed at a more appropriate timing. become. And since it is possible to secure a larger temperature difference until the internal temperature estimated using the control start temperature becomes equal to or higher than the temperature threshold, the steering control device does not limit the power supply to the motor. The motor can be driven.

  In the steering control device, the vehicle information is drive source temperature information that is information on a temperature of the drive source acquired from a drive source control device that controls a drive source of the vehicle, and the vehicle has an air temperature outside the vehicle. An outside air temperature sensor that detects outside air temperature information, which is information on a certain outside air temperature, is provided, and the control unit turns off the ignition switch when the ignition switch is turned on while the temperature detecting unit is out of order. The deviation between the temperature based on the drive source temperature information and the temperature based on the outside air temperature information after it has been assumed is assumed that the internal temperature when the ignition switch is turned on matches the outside air temperature. In this case, it is preferable to set a temperature based on the drive source temperature information or a temperature based on the outside air temperature information as the control start temperature.

  Similar to the internal temperature, the temperature of the drive source of the vehicle decreases toward the outside air temperature as the time elapsed after the ignition switch is turned off. That is, the drive source temperature information is vehicle information that can estimate a decrease in internal temperature after the ignition switch is turned off. For this reason, it is considered that both the internal temperature and the temperature of the drive source almost coincide with the external air temperature if the appropriate time has passed. Therefore, in the above configuration, the control start temperature can be set by using the drive source temperature information and the outside air temperature information as the vehicle information that can estimate the state of decrease in the internal temperature after the ignition switch is turned off.

  In the steering control device described above, the vehicle information is time information acquired from another control device, and the control unit, when the ignition switch is turned on in a state where the temperature detection unit is out of order, Based on the deviation between the time based on the time information when the ignition switch is turned off and the time based on the time information when the ignition switch is turned on, the ignition switch is turned on after the ignition switch is turned off. It is preferable to calculate an elapsed time until and set the control start temperature based on the elapsed time.

  The temperature of the drive source becomes higher compared to the outside air temperature as the traveling time of the vehicle is longer, and when the vehicle stops, the heat is dissipated to decrease toward the outside air temperature. According to the said structure, control start temperature can be set by using time information as vehicle information which can estimate the fall state of internal temperature after an ignition switch is turned off.

  In the steering control device described above, the vehicle is provided with an outside air temperature sensor that detects outside air temperature information that is outside air temperature information, and the control unit is in a state where the temperature detecting unit is out of order. When the ignition switch is turned on, when the elapsed time exceeds the time when the internal temperature when the ignition switch is turned on exceeds the time expected to match the outside air temperature, the temperature based on the outside air temperature information is It is preferable to set it as the control start temperature.

  As the time elapsed since the ignition switch is turned off, the internal temperature decreases toward the outside air temperature. For this reason, it is considered that the internal temperature almost coincides with the outside air temperature if the appropriate time has passed. In this case, the control unit can set the temperature based on the outside air temperature information as the control start temperature.

  According to the steering control device of the present invention, overheat protection control can be executed at a more appropriate timing even when the temperature detection unit fails.

The schematic block diagram of an electric power steering apparatus. The principal part sectional drawing of a motor. The block diagram which shows the structure of the steering control apparatus of 1st Embodiment. The graph which shows the relationship between the thermistor temperature and the temperature after a restriction | limiting start, and a current limiting value. The graph which shows the relationship between intake temperature and thermistor temperature, and time. The graph which shows the relationship of time until temperature after control start reaches a 1st temperature threshold value. The block diagram which shows the structure of the steering control apparatus of 2nd Embodiment.

<First Embodiment>
Hereinafter, a first embodiment in which the steering control device is applied to an electric power steering device (hereinafter referred to as “EPS”) will be described.

  As shown in FIG. 1, the EPS 1 gives a steering mechanism 2 that steers the steered wheels 15 and 15 based on an operation of the steering wheel 10 by a driver, and an assisting force for assisting the steering operation in the steering mechanism 2. And an steering control device 30 for controlling the actuator 3.

  The steering mechanism 2 includes a steering shaft 11 to which a steering wheel 10 is coupled, and a rack shaft 12 as a steered shaft that reciprocates in the axial direction in accordance with the rotation of the steering shaft 11. The steering shaft 11 includes a column shaft 11a connected to the steering wheel 10, an intermediate shaft 11b connected to the lower end portion of the column shaft 11a, and a pinion shaft 11c connected to the lower end portion of the intermediate shaft 11b. is doing. The rack shaft 12 and the pinion shaft 11c are arranged with a predetermined crossing angle, and the rack and pinion mechanism is formed by meshing the rack teeth formed on the rack shaft 12 and the pinion teeth formed on the pinion shaft 11c. 13 is configured. Further, tie rods 14 and 14 are connected to both ends of the rack shaft 12, and the tips of the tie rods 14 and 14 are connected to knuckle (not shown) to which the steered wheels 15 and 15 are assembled. Therefore, in EPS 1, the rotational motion of the steering shaft 11 accompanying the steering operation is converted into a reciprocating linear motion in the axial direction of the rack shaft 12 via the rack and pinion mechanism 13. This reciprocating linear motion in the axial direction is transmitted to the knuckle through the tie rods 14, 14, thereby changing the turning angle of the steered wheels 15, 15, that is, the traveling direction of the vehicle.

  The actuator 3 includes a motor 20 and a speed reduction mechanism 21. A rotation shaft 20 a of the motor 20 is connected to the column shaft 11 a via a speed reduction mechanism 21. The reduction mechanism 21 reduces the rotation of the motor 20 and transmits the reduced rotational force to the column shaft 11a. That is, the steering operation of the driver is assisted by applying the torque of the motor 20 to the steering shaft 11 as an auxiliary force (assist force).

  The steering control device 30 controls the motor 20 based on detection results of various sensors provided in the vehicle. As various sensors, for example, a torque sensor 40 and a rotation angle sensor device 41 are provided. The torque sensor 40 is provided on the column shaft 11a. The rotation angle sensor device 41 is provided in the motor 20. The torque sensor 40 detects a steering torque Th applied to the steering shaft 11 in accordance with the driver's steering operation. The rotation angle sensor device 41 detects the rotation angle θ of the rotation shaft 20 a of the motor 20. The steering control device 30 sets a target torque to be applied to the steering mechanism 2 based on the output value of each sensor, and the current supplied to the motor 20 so that the actual torque of the motor 20 becomes the target torque. To control.

  The steering control device 30 is communicably connected to other control devices such as the engine control device 51 and the display control device 53 via an in-vehicle network 50 such as a CAN (Controller Area Network).

  The engine control device 51 is connected to an intake air temperature sensor 52 provided in an intake pipe (not shown) of an engine that is a drive source. The intake air temperature sensor 52 detects the intake air temperature Ti. The engine control device 51 controls the driving state of the engine based on intake air temperature information that is information of the intake air temperature Ti (engine temperature). This intake air temperature information is used as drive source temperature information that is information about the temperature of the engine. The steering control device 30 acquires intake air temperature information, which is information on the intake air temperature Ti, from the engine control device 51 via the in-vehicle network 50 by transmitting a request signal to the engine control device 51.

  The display control device 53 controls display on a vehicle-mounted display (not shown) based on the detection result of the outside air temperature sensor 55 and the like. The in-vehicle display is provided, for example, on an instrument panel or the like, and displays information such as a car navigation system. The outside air temperature sensor 55 detects an outside air temperature To that is the outside air temperature. The steering control device 30 acquires the outside air temperature information, which is information on the outside air temperature To, from the display control device 53 via the in-vehicle network 50 by transmitting a request signal to the display control device 53.

  The engine control device 51 is connected to an ignition switch 4 for starting an engine that is a driving source of the vehicle. When the engine is started, the ignition switch 4 transitions from the off state to the on state, and outputs an ignition on signal Son to the engine control device 51. Further, the ignition switch 4 transitions from an on state to an off state when the engine is stopped, and outputs an ignition off signal Soff to the engine control device 51. The steering control device 30 acquires the ignition on signal Son or the ignition off signal Soff from the engine control device 51 via the in-vehicle network 50 by transmitting a request signal to the engine control device 51.

  As shown in FIG. 2, the actuator 3 includes a first housing 22 having two end walls and a side wall connecting the two end walls. The motor 20 is accommodated in the first housing 22. The rotation shaft 20 a of the motor 20 is disposed so as to protrude from both sides of the two end walls of the first housing 22. The actuator 3 includes a second housing 23 having an end wall 23a and a side wall 23b connected to the end wall 23a. One end of the second housing 23 is open. The side wall 23 b of the second housing 23 is connected to the end wall of the first housing 22 opposite to the speed reduction mechanism 21. A substrate 24 is fixed to the end wall 23 a of the second housing 23. Various electronic components are mounted on the substrate 24. As various electronic components, for example, a steering control device 30 and a rotation angle sensor device 41 are provided.

  The rotation angle sensor device 41 includes a bias magnet 42 and a magnetic sensor 43. The bias magnet 42 is fixed to the end of the rotating shaft 20a of the motor 20 opposite to the speed reduction mechanism 21. The magnetic sensor 43 is provided at a position facing the bias magnet 42 on the substrate 24 in the axial direction of the rotation shaft 20 a of the motor 20.

The configuration of the steering control device 30 will be described.
As shown in FIGS. 2 and 3, the steering control device 30 includes a microcomputer 31 (hereinafter referred to as “microcomputer”) as a control unit, a drive circuit 32, a current sensor 33, and a thermistor 60. The microcomputer 31 and the drive circuit 32 are provided at positions that do not face the bias magnet 42 on the substrate 24 in the axial direction of the rotation shaft 20 a of the motor 20. The microcomputer 31 generates a motor control signal Sm for controlling the driving of the motor 20 based on the steering torque Th. Further, the microcomputer 31 performs overheat protection control of the motor 20 based on the thermistor temperature Ts detected by the thermistor 60. The drive circuit 32 is a well-known configuration in which three arms corresponding to three phases (U, V, W) are connected in parallel with a switching unit such as two field effect transistors connected in series as a basic unit. PWM inverter. The drive circuit 32 converts each of the switching elements based on the motor control signal Sm generated by the microcomputer 31, thereby converting a direct current supplied from a direct current power source such as a battery into a three-phase alternating current.

  The thermistor 60 is provided at a position not facing the bias magnet 42 on the substrate 24 in the axial direction of the rotating shaft 20a of the motor 20. The thermistor 60 is a resistance element whose resistance value changes with changes in temperature. When the resistance value of the thermistor 60 changes as the temperature changes, the current flowing through the thermistor 60 changes, and a voltage corresponding to the change in this current is generated in the thermistor 60. Since there is a correlation between the voltage of the thermistor 60 and the temperature change in the vicinity of the substrate 24, the thermistor temperature Ts of the thermistor 60 can be obtained by obtaining the voltage of the thermistor 60. The switching element of the drive circuit 32 is mounted on the substrate 24, and the temperature of the switching element has a correlation with the substrate temperature that is the temperature of the substrate 24. The thermistor temperature Ts is used as the substrate temperature of the substrate 24. The thermistor temperature Ts is used to calculate a motor estimated temperature, which is an estimated temperature of the motor 20 that is estimated by taking into account the current supplied to the motor 20. The steering control device 30 grasps the temperature of the switching element (substrate temperature) of the drive circuit 32 and the temperature of the motor 20 (motor estimated temperature) through detection of the thermistor temperature Ts. The substrate temperature and the estimated motor temperature correspond to an internal temperature that is an internal temperature of the steering control device 30.

The microcomputer 31 includes an assist control unit 70, an overheat protection control unit 71, a temperature calculation unit 72, and a motor control signal generation unit 73.
Based on the steering torque Th detected by the torque sensor 40, the assist control unit 70 generates a basic current command value Ia * that is a basic component of the current command value I * that is a target of the actual current value I supplied to the motor 20. Calculate.

  The overheat protection control unit 71 acquires the basic current command value Ia * calculated by the assist control unit 70 and the thermistor temperature Ts detected by the thermistor 60. When the absolute value of the basic current command value Ia * is larger than the current limit value Ilim, the overheat protection control unit 71 limits the absolute value of the basic current command value Ia * to the current limit value Ilim, and the current command value I * Is calculated. In addition, when the absolute value of the basic current command value Ia * is equal to or less than the current limit value Ilim, the overheat protection control unit 71 does not limit the value of the basic current command value Ia * and uses the basic current command value Ia * as the current. Calculated as command value I *. The current limit value Ilim is determined as the upper limit value of the current supplied to the motor 20 in order to suppress the motor 20 from overheating. Note that the current limit value Ilim is set so that the portion to be protected can be protected in view of the temperature conditions of the substrate temperature and the estimated motor temperature at that time. For example, when the substrate temperature is rising, the current limit value Ilim is set so that the substrate temperature decreases. Further, for example, when the estimated motor temperature is increasing, the current limit value Ilim is set so that the estimated motor temperature decreases.

  The motor control signal generator 73 generates the actual current value I detected by the current sensor 33 provided in the power supply path between the drive circuit 32 and the motor 20 and the rotation angle θ detected by the rotation angle sensor device 41. Based on this, the motor control signal Sm is generated by executing the current feedback control so that the current command value I * follows the actual current value I. The motor control signal Sm defines the on-duty of each switching element of the drive circuit 32.

  The drive circuit 32 converts a direct current supplied from a direct current power source such as a battery into a three-phase alternating current by switching each switching element based on the motor control signal Sm. The converted three-phase alternating current is supplied to the motor 20 via the power supply path of each phase.

  The overheat protection control unit 71 changes the current limit value Ilim based on the substrate temperature calculated using the thermistor temperature Ts detected by the thermistor 60 and the estimated motor temperature. The overheat protection control unit 71 stores a map M indicating the relationship between the substrate temperature and the motor estimated temperature and the current limit value Ilim.

  A map M shown in FIG. 4 is obtained by experimentally determining the relation between the current limit value Ilim with respect to the substrate temperature and the estimated motor temperature and storing it in the overheat protection control unit 71. The current limit value Ilim is set to a smaller value as the substrate temperature and the estimated motor temperature are higher. In the map M, three stages of current limit values Ilim, which are a basic current limit value Ilim0, a first current limit value Ilim1, and a second current limit value Ilim2, are determined according to the substrate temperature and the estimated motor temperature in descending order of absolute values. It has been. In the map M, the second temperature threshold value Tmp2 and the first temperature threshold value Tmp1 are determined in descending order of absolute values.

  When the substrate temperature and the estimated motor temperature are less than the first temperature threshold value Tmp1, the overheat protection control unit 71 sets the basic current limit value Ilim0 having a large absolute value so as not to limit the basic current command value Ia *. When the substrate temperature and the estimated motor temperature are lower than the first temperature threshold value Tmp1, overheating of the steering control device 30 and the motor 20 is not particularly problematic. For this reason, the steering control device 30 can drive the motor 20 without limiting the basic current command value Ia *.

  When the substrate temperature and the estimated motor temperature are equal to or higher than the first temperature threshold value Tmp1 and lower than the second temperature threshold value Tmp2, the overheat protection control unit 71 has a first current limit value Ilim1 having a smaller absolute value than the basic current limit value Ilim0. Set. When the substrate temperature and the estimated motor temperature are equal to or higher than the first temperature threshold value Tmp1 and lower than the second temperature threshold value Tmp2, the steering control device 30 or the motor 20 is not in an overheated state, but is likely to reach an overheated state. Is in a state of being. The first current limit value Ilim1 is set to a value that limits the basic current command value Ia * so that an increase in the temperature of the steering control device 30 or the motor 20 can be suppressed. The overheat protection control unit 71 executes overheat protection control for limiting the driving of the motor 20 based on the first current limit value Ilim1 until the substrate temperature and the estimated motor temperature become less than the first temperature threshold value Tmp1.

  When the substrate temperature and the estimated motor temperature are equal to or higher than the second temperature threshold value Tmp2, the overheat protection control unit 71 sets the second current limit value Ilim2 having a smaller absolute value than the first current limit value Ilim1. When the substrate temperature and the estimated motor temperature are equal to or higher than the second temperature threshold value Tmp2, the steering control device 30 or the motor 20 is in an overheated state. In this case, it is necessary to promote a decrease in the substrate temperature and the estimated motor temperature. Therefore, the basic current command value Ia * is set to a value that limits the increase in the substrate temperature and the estimated motor temperature. The overheat protection control unit 71 executes overheat protection control for limiting the driving of the motor 20 based on the second current limit value Ilim2 until the substrate temperature and the estimated motor temperature become less than the second temperature threshold value Tmp2.

  As described above, the overheat protection control unit 71 uses the map M based on the substrate temperature and the estimated motor temperature to limit the current limit value Ilim (the basic current limit value Ilim0, the first current limit value Ilim1, and the second current limit value). Ilim2) is set.

  The thermistor 60 may fail. For example, the thermistor 60 has a disconnection failure or a short-circuit failure. As a result, the normal thermistor temperature Ts cannot be detected by the thermistor 60, and the steering control device 30 cannot grasp accurate values as the substrate temperature and the estimated motor temperature. Therefore, the microcomputer 31 of the steering control device 30 includes the substrate temperature and the estimated motor temperature in a state where the thermistor 60 is out of order so that the substrate temperature and the estimated motor temperature can be estimated based on information obtained from other than the thermistor 60. Is calculated from information other than the thermistor 60.

  As shown in FIG. 3, the temperature calculation unit 72 acquires a thermistor temperature Ts, an outside air temperature To, an intake air temperature Ti, an ignition on signal Son, an ignition off signal Soff, and an actual current value I. When the thermistor 60 is out of order, the temperature calculation unit 72 calculates a post-control temperature Te that is a temperature estimated based on information obtained from other than the thermistor 60. There are three modes for calculating the post-control temperature Te. For example, when the input thermistor temperature Ts is not in the normal range, or when the thermistor temperature Ts itself is not input, the temperature calculation unit 72 determines that the thermistor 60 has failed. Further, the temperature calculation unit 72 determines whether the ignition switch 4 is turned on or off based on the ignition on signal Son and the ignition off signal Soff.

  The first calculation mode of the temperature Te after the control is started is when the thermistor 60 breaks down during the period in which the assist control for applying the assisting force for assisting the steering operation to the steering mechanism 2 is executed. This is performed when the temperature Te is calculated after the start of control. The temperature calculation unit 72 uses the higher one of the estimated ambient temperature, which is an estimated value of the ambient temperature of the substrate 24, and the estimated substrate temperature, which is an estimated value of the temperature of the substrate 24, as the post-control start temperature Te. Set. The estimated ambient temperature is the temperature of the atmosphere inside the actuator 3. In calculating the estimated ambient temperature, the thermistor temperature Ts considered to be normally detected when the thermistor 60 is not broken is used. The temperature calculation unit 72 obtains the temperature change amount of the substrate temperature and the estimated motor temperature with the passage of time using a map showing the relationship between the passage of time obtained experimentally and the temperature rise of the estimated ambient temperature. The temperature calculation unit 72 calculates the estimated ambient temperature estimated by the motor 20 by adding the temperature change amount of the substrate temperature and the estimated motor temperature with the passage of time to the thermistor temperature Ts considered to be normally detected. . Further, in calculating the estimated substrate temperature of the substrate 24, the estimated atmospheric temperature is used. The temperature calculation unit 72 estimates heat generation of the switching elements of the motor 20 and the drive circuit 32 using the actual current value I in order to estimate a change in the substrate temperature. The temperature calculation unit 72 calculates the estimated substrate temperature of the substrate 24 by adding the temperature change amount due to the heat generation to the estimated atmosphere temperature.

  The second calculation mode of the temperature Te after the start of control is that the ignition switch 4 is turned on in a state where the thermistor 60 is broken when the steering control device 30 immediately after the ignition switch 4 is turned off is still operating. This is performed when calculating the temperature Te after the start of control. It should be noted that the failure timing of the thermistor 60 when performing this calculation mode is limited to the case where the thermistor 60 fails during the period when the ignition switch 4 is turned on immediately before the ignition switch 4 is turned off (during the previous trip). The In the case of the second calculation mode, the temperature calculation unit 72 can calculate the temperature Te after the start of control in the same calculation mode as the first calculation mode.

  The third calculation mode of the post-control temperature Te is performed when the post-control start temperature Te is calculated when it is determined that the thermistor 60 has failed when the ignition switch 4 is turned on. That is, when the ignition switch 4 is turned on when the thermistor 60 is out of order, the post-control temperature Te is calculated in the third calculation mode.

  In this case, since there is a period during which the ignition switch 4 is off, even if the post-control temperature Te is estimated from the normal value before the failure of the thermistor 60, the accurate post-control temperature Te cannot be obtained. Conventionally, when the thermistor 60 is in failure, for example, assuming a specific temperature (for example, 95 degrees) under the most severe thermal conditions, the length of the period from when the ignition switch 4 is turned on to when it is turned on is long. Regardless of this, this specific temperature is used as the temperature at the start of control (hereinafter referred to as “control start temperature”) and used for the calculation of the temperature Te after the start of control thereafter. This specific temperature is set from the viewpoint of reliably performing overheat protection of the steering control device 30 and the motor 20. The control start temperature T0 is an estimated value of the substrate temperature and the estimated motor temperature when the ignition switch 4 is turned on. On the other hand, when the thermistor 60 is out of order, the substrate temperature and the estimated motor temperature when the ignition switch 4 is turned on are the vehicle running state before the ignition switch 4 is turned off and the ignition switch 4 is turned off. It varies depending on the period from when it is turned on. For this reason, the specific temperature set from the viewpoint of reliably executing the overheat protection control may cause a corresponding difference from the actual substrate temperature and the estimated motor temperature.

  Therefore, in the present embodiment, the control start temperature T0 is set by paying attention to the fact that the substrate temperature and the estimated motor temperature decrease toward the outside air temperature To as the time elapsed after the ignition switch 4 is turned off. The post-control start temperature Te is calculated using the control start temperature T0.

  As shown in FIG. 5, the intake air temperature Ti, the substrate temperature, and the estimated motor temperature have a relationship that the temperature decreases toward the outside air temperature To as time elapses after the ignition switch 4 is turned off. ing. The intake air temperature Ti, the substrate temperature, and the estimated motor temperature finally converge to the outside air temperature To.

  As shown in FIG. 3, the temperature calculation unit 72 uses the intake air temperature Ti and the outside air temperature To when the ignition switch 4 is turned on, and the substrate temperature and the estimated motor temperature (internal) after the ignition switch 4 is turned off. (Temperature) drop state is estimated. The intake air temperature Ti and the outside air temperature To are vehicle information that can estimate a decrease in the substrate temperature and the estimated motor temperature (internal temperature) since the ignition switch 4 was turned off immediately before. When the deviation between the intake air temperature Ti and the outside air temperature To is equal to or less than the deviation threshold value X, the temperature calculation unit 72 can estimate that the substrate temperature and the estimated motor temperature have also decreased until they almost coincide with the outside air temperature To. When the deviation between the intake air temperature Ti and the outside air temperature To exceeds the deviation threshold value X, the temperature calculation unit 72 can estimate that the substrate temperature and the estimated motor temperature have not decreased until they almost coincide with the outside air temperature To. The deviation threshold value X is set to a value at which the intake air temperature Ti is considered to be almost coincident with the outside air temperature To. When the deviation between the intake air temperature Ti and the outside air temperature To is equal to or less than the deviation threshold X, the temperature calculation unit 72 sets the intake air temperature Ti (or the outside air temperature To) as the control start temperature T0. Further, when the deviation between the intake air temperature Ti and the outside air temperature To exceeds the deviation threshold value X, the temperature calculation unit 72 sets the specific temperature as the control start temperature T0. The temperature calculation unit 72 sets the higher one of the estimated atmospheric temperature and the estimated substrate temperature estimated using the control start temperature T0 as the post-control start temperature Te. The calculation of the estimated atmospheric temperature and the estimated substrate temperature is the same as in the first calculation mode. In calculating the estimated atmospheric temperature, the control start temperature T0 is used. The temperature calculation unit 72 calculates the estimated ambient temperature by adding the temperature change amount of the substrate temperature and the estimated motor temperature to the control start temperature T0. In addition, the temperature calculation unit 72 calculates the estimated substrate temperature of the substrate 24 by adding the amount of temperature change due to the heat generated by the motor 20 to the estimated ambient temperature.

  When the ignition switch 4 is turned on while the thermistor 60 is in failure, the overheat protection control unit 71 calculates the current limit value Ilim using the post-control temperature Te calculated by the temperature calculation unit 72. The overheat protection control unit 71 calculates a current limit value Ilim (basic current limit value Ilim0, first current limit value Ilim1, and second current limit value Ilim2) using the map M, based on the temperature Te after the start of control. . The overheat protection control unit 71 uses the calculated current limit value Ilim to limit the basic current command value Ia * and calculates the current command value I *.

The operation and effect of the first embodiment will be described.
(1) When the ignition switch 4 is turned on while the thermistor 60 is out of order, the steering control device 30 can estimate the lowered state of the substrate temperature and the estimated motor temperature since the ignition switch 4 was turned off immediately before. The control start temperature T0 is set based on the difference between the intake air temperature Ti and the outside air temperature To, which is vehicle information. When the intake air temperature Ti after the ignition switch 4 is turned off is taken into consideration, the control start temperature T0 is brought closer to the substrate temperature and the estimated motor temperature when the ignition switch 4 is turned on than when the intake air temperature Ti is set to a specific temperature. It becomes possible to set. As a result, the post-control start temperature Te of the motor 20 can be calculated based on the control start temperature T0 and the amount of temperature change due to the heat generation of the motor 20, and therefore steering based on the more appropriate post-control start temperature Te of the motor 20 The overheat protection control of the control device 30 or the motor 20 can be executed.

  For example, when the deviation between the intake air temperature Ti and the outside air temperature To when the ignition switch 4 is turned on is equal to or less than the deviation threshold value X, the substrate temperature and the estimated motor temperature are also lowered until they almost coincide with the outside air temperature To. It can be estimated. For this reason, it becomes possible to set the intake air temperature Ti (or the outside air temperature To), which is lower than the specific temperature set from the viewpoint of surely executing the overheat protection control, as the control start temperature T0. .

  The temperature difference until the temperature Te after the start of control becomes equal to or higher than the first temperature threshold value Tmp1 will be described with reference to FIG. FIG. 6 is a graph showing changes in the temperature Te after the start of control over time, and shows the time until the temperature Te after the start of control reaches the first temperature threshold value Tmp1. As shown in FIG. 6, the deviation between the first temperature threshold value Tmp1 and the intake air temperature Ti (or the outside air temperature To) is larger than the deviation between the first temperature threshold value Tmp1 and the specific temperature. For this reason, when the intake air temperature Ti is set to the control start temperature T0 than when the specific temperature is set to the control start temperature T0, the temperature Te of the motor 20 until the post-control start temperature Te becomes equal to or higher than the first temperature threshold Tmp1. A large amount of temperature change due to heat generation can be secured. Therefore, when the intake air temperature Ti is set to the control start temperature T0, the time t2 until the post-control start temperature Te becomes equal to or higher than the first temperature threshold value Tmp1, the post-control start temperature when the specific temperature is set to the control start temperature T0. It can be made longer than the time t1 until Te reaches the first temperature threshold value Tmp1 or more. Therefore, since the temperature difference until the temperature Te after the control starts becomes equal to or higher than the first temperature threshold value Tmp1 can be ensured, the steering control device 30 can increase the motor power without restricting the power supply to the motor 20 as much. 20 can be driven.

  On the other hand, when the deviation between the intake air temperature Ti and the outside air temperature To when the ignition switch 4 is turned on exceeds the deviation threshold X, the substrate temperature and the estimated motor temperature decrease until they almost coincide with the outside air temperature To. It can be estimated that it is not. For this reason, the specific temperature is set as the control start temperature T0. As a result, the overheat protection control can be reliably executed.

  Therefore, when the ignition switch 4 is turned on while the thermistor 60 is out of order, the control start temperature T0 can be estimated more appropriately, so that the overheat protection control can be executed at a more appropriate timing. It becomes like this.

  (2) The substrate temperature, the estimated motor temperature, and the intake air temperature Ti decrease toward the outside air temperature To as the time from when the ignition switch 4 is turned off elapses. That is, the intake air temperature information of the intake air temperature Ti is vehicle information that can estimate the lowered state of the substrate temperature after the ignition switch 4 is turned off. If the corresponding time has elapsed, it is considered that the substrate temperature and the estimated motor temperature almost coincide with the outside air temperature To together with the intake air temperature Ti. Therefore, in this embodiment, the control start temperature T0 can be set by using the intake air temperature Ti and the outside air temperature To.

  (3) Both the estimated ambient temperature and the estimated substrate temperature are merely estimates of the substrate temperature and the estimated motor temperature (internal temperature). For this reason, in the present embodiment, the temperature calculation unit 72 sets the higher one of the estimated ambient temperature and the estimated substrate temperature as the post-control start temperature Te. Thereby, from the viewpoint of reliably executing the overheat protection control, the overheat protection control can be more appropriately executed.

Second Embodiment
Hereinafter, a second embodiment in which the steering control device is applied to EPS will be described. Here, the difference from the first embodiment will be mainly described.

  As shown in FIG. 1, the display control device 53 acquires the current time t from information (time signal and orbit information) transmitted from a GPS (Global Positioning System) satellite. Time t is used to display the current time on the in-vehicle display. The steering control device 30 transmits a request signal to the display control device 53, so that the time information that is the information of the time t and the outside air temperature that is the information of the outside air temperature To from the display control device 53 via the in-vehicle network 50. Get information.

  As shown in FIG. 7, the temperature calculation unit 72 acquires the thermistor temperature Ts, time t, outside air temperature To, ignition-on signal Son, ignition-off signal Soff, and actual current value I. The first and second mode calculations of the temperature Te after the start of control are the same as in the first embodiment.

  In the case of the third calculation mode, the temperature calculation unit 72 calculates the deviation between the time t based on the time information when the ignition switch 4 is turned off and the time t based on the time information when the ignition switch 4 is turned on. Based on this, an elapsed time from when the ignition switch 4 is turned off to when it is turned on is calculated. Based on this elapsed time, the temperature calculation unit 72 estimates the lowered state of the substrate temperature and the estimated motor temperature after the ignition switch 4 is turned off. This elapsed time is vehicle information that can estimate the decrease in the substrate temperature and the estimated motor temperature since the ignition switch 4 was turned off immediately before. When the elapsed time is equal to or greater than the time threshold value Y, the temperature calculation unit 72 can estimate that the substrate temperature and the estimated motor temperature have decreased until they substantially coincide with the outside air temperature To, so the outside air temperature To (or the intake air temperature Ti) ) Is set as the control start temperature T0. Further, when the elapsed time is less than the time threshold Y, the temperature calculation unit 72 can estimate that the substrate temperature and the estimated motor temperature have not decreased until they substantially coincide with the outside air temperature To. Set as T0. The time threshold value Y is a value obtained by experiments or the like as the time when the substrate temperature and the estimated motor temperature are assumed to be almost the same as the outside air temperature To.

The operation and effect of the second embodiment will be described.
(4) The substrate temperature and the estimated motor temperature decrease toward the outside air temperature To as the time from when the ignition switch 4 is turned off elapses. That is, the elapsed time from when the ignition switch 4 is turned on to when it is turned on is vehicle information that can estimate the decrease in the substrate temperature and the estimated motor temperature after the ignition switch 4 is turned off. For this reason, in the present embodiment, the control start temperature T0 can be set by using the elapsed time from when the ignition switch 4 is turned off to when it is turned on.

  (5) The temperature of the drive source becomes higher than the outside air temperature as the traveling time of the vehicle becomes longer, and when the vehicle stops, the heat is dissipated to decrease toward the outside air temperature. That is, as the time elapsed after the ignition switch 4 is turned off, the substrate temperature and the estimated motor temperature decrease toward the outside air temperature To. For this reason, it is considered that the substrate temperature and the estimated motor temperature almost coincide with the outside air temperature To if the appropriate time has elapsed. In this case, the temperature calculation unit 72 can set the outside air temperature To (or the intake air temperature Ti) based on the outside air temperature information as the control start temperature T0.

Each embodiment may be changed as follows. Further, the following other embodiments can be combined with each other within a technically consistent range.
In the second embodiment, the temperature calculation unit 72 sets the outside air temperature To as the control start temperature T0 when the elapsed time is equal to or greater than the time threshold Y, but is not limited thereto. For example, the temperature calculation unit 72 obtains a map indicating the relationship between the substrate temperature that decreases with respect to the elapsed time and the estimated motor temperature by experiments and the like, and uses this map to calculate the substrate temperature and the estimated motor temperature relative to the elapsed time. Then, the substrate temperature and the estimated motor temperature are set as the control start temperature T0. In this case, the temperature calculation unit 72 sets the control start temperature T0 to a temperature closer to the outside air temperature To as the elapsed time increases.

  -In 2nd Embodiment, although the display control apparatus 53 calculated | required time t from the information transmitted, for example from a GPS satellite, it is not restricted to this. The display control device 53 may obtain the time t from information obtained from a mechanical timepiece, a quartz timepiece, or the like.

  In the first embodiment, the temperature calculation unit 72 sets the intake air temperature Ti as the control start temperature T0 when the deviation between the intake air temperature Ti and the outside air temperature To is equal to or less than the deviation threshold value X, but is not limited thereto. For example, the temperature calculation unit 72 may set the control start temperature T0 according to the deviation between the intake air temperature Ti and the outside air temperature To. Further, since the intake air temperature Ti tends to be higher than the substrate temperature and the motor estimated temperature, the time until the intake air temperature Ti reaches the outside air temperature To is the time until the substrate temperature and the motor estimated temperature reach the outside air temperature To. Longer than. If the control start temperature T0 is set in consideration of such a relationship, the overheat protection control can be executed flexibly.

  In the first embodiment, the temperature calculation unit 72 sets the control start temperature T0 using the outside air temperature To in addition to the intake air temperature Ti, but even if the control start temperature T0 is set based only on the intake air temperature Ti. Good. Since the outside air temperature To falls within a certain temperature range according to the environment in which the vehicle is used, if the intake air temperature Ti falls within this temperature range, the intake air temperature Ti can be set as the control start temperature T0.

  In each embodiment, when the elapsed time is equal to or greater than the time threshold Y, the temperature calculation unit 72 sets the outside air temperature To as the control start temperature T0, and the deviation between the intake air temperature Ti and the outside air temperature To is less than or equal to the deviation threshold X In this case, the intake air temperature Ti is set as the control start temperature T0, but is not limited thereto. For example, when the elapsed time is equal to or greater than the time threshold Y, or when the deviation between the intake air temperature Ti and the outside air temperature To is equal to or less than the deviation threshold X, the temperature calculation unit 72 is obtained based on weather information obtained from the Internet or the like. The outside air temperature at the current position may be set as the control start temperature T0. That is, when the elapsed time is equal to or greater than the time threshold Y, or when the deviation between the intake air temperature Ti and the outside air temperature To is equal to or less than the deviation threshold X, the temperature calculation unit 72 calculates a temperature closer to the outside air temperature To than the specific temperature. What is necessary is just to set as control start temperature T0.

  In each embodiment, the overheat protection control unit 71 sets the three-stage current limit value Ilim based on the thermistor temperature Ts detected by the thermistor 60, but is not limited thereto. The overheat protection control unit 71 may set a two-stage current limit value Ilim, for example, a basic current limit value Ilim0 that does not limit the drive of the motor 20 and a first current limit value Ilim1 that limits the drive of the motor 20. . The overheat protection control unit 71 may set four or more levels of current limit values Ilim.

  In each embodiment, when performing the overheat protection control based on the second current limit value Ilim2, the overheat protection control unit 71 stops the driving of the motor 20 by setting the second current limit value Ilim2 to “0”. You may make it do.

  In each embodiment, the temperature calculation unit 72 calculates either the estimated ambient temperature or the estimated substrate temperature and controls the temperature when the ignition switch 4 is turned on while the thermistor 60 is broken. The post-start temperature Te may be used.

  In the first embodiment, the intake air temperature information that is the information of the intake air temperature Ti is used as the drive source temperature information, but the present invention is not limited to this. For example, exhaust temperature information that is exhaust temperature information that is the temperature of exhaust from the engine may be used as drive source temperature information, or cooling water temperature information that is information about the temperature of cooling water that cools the engine is used. May be. That is, the drive source temperature information may be any information as long as it is information on the engine temperature related to the internal temperature of the engine.

The steering control device 30 has grasped the substrate temperature and the estimated motor temperature through the detection of the thermistor temperature Ts, but it is only necessary to grasp at least the substrate temperature.
-In each embodiment, although the steering control apparatus 30 was arrange | positioned inside the 2nd housing 23 provided adjacent to the 1st housing 22 in which the motor 20 was accommodated, it is not restricted to this. That is, the steering control device 30 may be disposed at a position separated from the motor 20. In this case, at least the substrate temperature of the substrate 24 is used as the internal temperature of the steering control device 30.

-In each embodiment, although the thermistor 60 was used as a temperature detection part, it is not restricted to this. For example, a thermocouple or a resistance temperature detector may be used as the temperature detection unit.
-In each embodiment, although the steering control apparatus 30 was applied to EPS1, you may apply to a steer-by-wire type steering apparatus, for example.

  In each embodiment, the vehicle is a vehicle that employs an engine as a drive source, but may be a so-called electric vehicle that employs a motor as a drive source. In the case of an electric vehicle, the ignition switch 4 is a switch that starts a motor as a drive source.

  DESCRIPTION OF SYMBOLS 1 ... EPS, 2 ... Steering mechanism, 3 ... Actuator, 4 ... Ignition switch, 10 ... Steering wheel, 11 ... Steering shaft, 12 ... Rack shaft, 15 ... Steering wheel, 20 ... Motor, 20a ... Rotating shaft, 21 ... Deceleration mechanism, 22 ... first housing, 23 ... second housing, 24 ... substrate, 30 ... steering control device, 31 ... microcomputer, 32 ... drive circuit, 33 ... current sensor, 40 ... torque sensor, 41 ... rotation angle sensor device 42 ... Bias magnet, 43 ... Magnetic sensor, 50 ... In-vehicle network, 51 ... Engine control device, 52 ... Intake temperature sensor, 53 ... Display control device, 55 ... Outside air temperature sensor, 60 ... Thermistor, 70 ... Assist control unit, 71 ... Overheat protection control unit, 72 ... Temperature calculation unit, 73 ... Motor control signal generation unit, θ ... Rotation angle, I ... Actual current value, I ... current command value, Ia ... basic current command value, M ... map, Sm ... motor control signal, t ... time, T0 ... control start temperature, Te ... control start temperature, Th ... steering torque, Ti ... intake air temperature, To ... outside air temperature, Ts ... thermistor temperature, Ilim ... current limit value, Ilim0 ... basic current limit value, Ilim1 ... first current limit value, Ilim2 ... second current limit value, Tmp1 ... first temperature threshold, Tmp2 ... second temperature Threshold: Son ... Ignition on signal, Soff ... Ignition off signal.

Claims (4)

In a steering control device that controls power supply to a motor that applies torque to a steering mechanism of a vehicle,
A temperature detector that detects an internal temperature that is an internal temperature of the steering control device;
A control unit that controls power supply to the motor and controls the power supply to the motor when the internal temperature detected by the temperature detection unit is equal to or higher than a temperature threshold that requires overheat protection to limit power supply to the motor. And comprising
When the ignition switch is turned on in a state where the temperature detection unit is out of order, the control unit is based on vehicle information that can estimate a decrease state of the internal temperature immediately after the ignition switch is turned off. A steering control device that sets a control start temperature when the ignition switch is turned on and estimates the internal temperature used in the control of the overheat protection based on the control start temperature. The vehicle information is drive source temperature information that is information on the temperature of the drive source acquired from a drive source control device that controls the drive source of the vehicle,
The vehicle is provided with an outside air temperature sensor that detects outside air temperature information that is outside air temperature information that is outside the vehicle,
When the ignition switch is turned on in a state where the temperature detection unit is out of order, the control unit detects a temperature based on the driving source temperature information and a temperature based on the outside air temperature information after the ignition switch is turned off. Is assumed that the internal temperature when the ignition switch is turned on matches the outside air temperature, the temperature based on the drive source temperature information or the temperature based on the outside air temperature information is The steering control device according to claim 1, wherein the steering control device is set as a control start temperature. The vehicle information is time information acquired from another control device,
When the ignition switch is turned on in a state where the temperature detection unit is out of order, the control unit is based on the time information when the ignition switch is turned off, and when the ignition switch is turned on. 2. An elapsed time from when the ignition switch is turned off to when the ignition switch is turned on is calculated based on a deviation from the time based on the time information, and the control start temperature is set based on the elapsed time. The steering control device described. The vehicle is provided with an outside air temperature sensor that detects outside air temperature information that is outside air temperature information that is outside the vehicle,
When the ignition switch is turned on in a state where the temperature detection unit is out of order, the control unit assumes that the elapsed time matches the internal temperature when the ignition switch is turned on. 4. The steering control device according to claim 3, wherein a temperature based on the outside air temperature information is set as the control start temperature when the time to be exceeded is exceeded.