JP2012046049A - Steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a steering function by an electric motor to be obtained sufficiently, while maintaining an over-heat preventing function, even if estimated temperature data cannot be written in a non-volatile memory.SOLUTION: If data in an EEPROM is abnormal, a microcomputer corrects each of temporary temperature values SUM1max, SUM2max and SUM3max for computing the motor estimated temperature by using a board temperature change value ΔT(Tbmax-Tb) obtained by subtracting the board temperature Tb, which is detected by a temperature sensor, from the temporary board temperature Tbmax previously set at a high temperature (S61, S62). Consequently, initial values SUM1(n-1), SUM2(n-1) and SUM3(n-1) corresponding to the board temperature Tb can be set. In this case, when the temperature sensor is abnormal, correction by using the board temperature change value ΔT(Tbmax-Tb) is not performed (S63).

Description

  The present invention relates to a steering apparatus such as an electric power steering apparatus that generates a steering torque by an electric motor.

  Conventionally, for example, an electric power steering device is known as this type of steering device. The electric power steering apparatus includes an electric motor that generates a steering assist torque in response to a steering operation of a steering wheel, and an electronic control unit (referred to as an ECU) that controls energization of the electric motor. The ECU includes a calculation circuit whose main part is composed of a microcomputer and calculates a target energization control amount of the electric motor, and a motor drive circuit that supplies power to the electric motor in response to a command signal from the calculation circuit.

  In such an electric power steering device, the temperature of the electric motor or the motor drive circuit is monitored in order to prevent the electric motor or the motor drive circuit from being damaged due to heat generation, and the monitor temperature exceeds the set temperature for preventing overheating. Restricts the current flowing to the electric motor. In this case, it is difficult to directly measure the temperature of the electric motor with a temperature sensor. Therefore, in the electric power steering apparatus proposed in Patent Document 1, the temperature of the electric motor is estimated by calculation based on the value of the current flowing through the electric motor.

  In the electric power steering apparatus proposed in Patent Document 1, during the assist control, the estimated temperature of the electric motor is repeatedly calculated, and when the ignition switch is turned off to end the assist control, the estimated temperature at that time is handled. The estimated temperature data is stored in a nonvolatile memory. The ECU reads the estimated temperature data stored in the nonvolatile memory at the start of the next assist control, and uses it for the temperature estimation calculation as the initial value of the estimated temperature.

JP 2008-195246 A

  However, the estimated temperature data may not be properly written to the nonvolatile memory. For example, when the ignition switch is turned on and the cranking operation is performed while the estimated temperature data is being written to the nonvolatile memory after the assist control is finished, the ECU's temporary voltage drop causes the ECU to The microcomputer may be reset. In such a case, the estimated temperature data cannot be properly written to the nonvolatile memory.

  Therefore, when the estimated temperature data cannot be written in the nonvolatile memory in this way, the ECU uses the preset temporary estimated temperature initial value when starting the assist control. Start computation. However, the temporary estimated temperature initial value is set to the highest temperature in the temperature range that the electric motor can take so that the electric motor can be prevented from overheating regardless of the situation where the assist control is started. Even if the motor temperature is low, the calculated estimated temperature is high. Therefore, the overheat prevention function works more than necessary, and the current flowing to the electric motor is limited. For this reason, the steering wheel operation becomes heavy and the burden on the driver increases.

  The present invention has been made to cope with the above problem, and even when the estimated temperature data cannot be written in the nonvolatile memory, the steering function by the electric motor can be sufficiently obtained while the overheat prevention function is maintained. The purpose is to do so.

  In order to achieve the above object, the present invention is characterized by an electric motor (15) that generates a steering torque, temperature estimation means (S21 to S26) for estimating the temperature of the electric motor by sequential calculation, and a steering handle Steering detection means (S11) for detecting the steering state, and target energization control of the electric motor based on the detected steering state of the steering wheel while applying a current limit based on the estimated temperature of the estimated electric motor. Motor control means (S12 to S19) for calculating the amount and controlling the electric motor according to the calculated target energization control amount, and nonvolatile storage means for storing estimated temperature data relating to the estimated temperature of the electric motor (44) and an estimated temperature related to the estimated temperature of the electric motor estimated by the temperature estimating means at the end of the drive control of the electric motor. Estimated temperature data reading / writing means (S51, S39, S42) for writing estimated data to the nonvolatile storage means and reading estimated temperature data stored in the nonvolatile storage means at the next start of drive control of the electric motor. The temperature estimation means is a steering device that starts calculation of the estimated temperature of the electric motor using the estimated temperature data read by the estimated temperature data read / write means at the start of drive control of the electric motor; Related temperature measuring means (25) for measuring the temperature of the portion where the temperature changes with the temperature change of the electric motor as the related temperature, and whether or not the data in the nonvolatile storage means is abnormal at the start of drive control of the electric motor Data abnormality detection means (S52) for determining the initial estimated temperature initially set to a high temperature for overheating prevention (SUM1max, SUM2max, SUM3max) are stored, and when the abnormality of the data in the nonvolatile storage means is detected, the related temperature (Tb) measured by the related temperature measuring means is acquired, and the temporary Correction at the time of abnormality that calculates the estimated estimated temperature initial value (SUM1 (n-1), SUM2 (n-1), SUM3 (n-1)) corrected so that the estimated temperature initial value decreases as the related temperature decreases Estimated temperature initial value calculating means (S61, S62), and the temperature estimating means is calculated by the abnormal time corrected estimated temperature initial value calculating means when an abnormality of data in the nonvolatile storage means is detected. The calculation of the estimated temperature of the electric motor is started using the corrected estimated temperature initial value.

  In this invention, the temperature estimation means estimates the temperature of the electric motor by sequential calculation, and the motor control means applies a current limit based on this estimated temperature while applying the target current control amount of the electric motor based on the steering state of the steering wheel. And the electric motor is driven and controlled according to the target energization control amount. Thus, steering torque is generated by the drive control of the electric motor. At this time, the electric motor is prevented from being overheated by current limitation based on the estimated temperature. Note that the temperature of the electric motor is not limited to the temperature of the electric motor itself, but may be the temperature increase of the electric motor. This is because it is possible to prevent overheating of the electric motor.

  The estimated temperature data read / write means writes the estimated temperature data of the electric motor estimated at the end of the drive control of the electric motor to the nonvolatile storage means, and is stored in the nonvolatile storage means at the next drive control of the electric motor. Read temperature data. The read estimated temperature data becomes initial value data necessary to start calculation of the estimated motor temperature.

  If the microcomputer reset occurs in the middle of writing the estimated temperature data to the nonvolatile storage means, the estimated temperature data cannot be properly written to the nonvolatile storage means. In this case, appropriate initial value data required for calculating the estimated motor temperature cannot be obtained. Therefore, the present invention includes related temperature measurement means, data abnormality detection means, and abnormality correction estimated temperature initial value calculation means.

  The related temperature measuring means measures the temperature of the part where the temperature changes with the temperature change of the electric motor as the related temperature. When the temperature of the electric motor decreases (increases) over time, the related temperature measuring means may measure the temperature of the portion where the temperature decreases (increases) with this. For example, since the substrate temperature of the drive circuit that drives the electric motor is highly related to the temperature of the electric motor, the substrate temperature can be used as the related temperature.

  The data abnormality detection means determines whether or not the data in the nonvolatile storage means is abnormal when the drive control of the electric motor is started. Then, when an abnormality in the data in the nonvolatile storage means is detected, the corrected estimated temperature initial value calculating means at the time of abnormality calculates a corrected estimated temperature initial value that is an initial value necessary for starting the calculation of the motor estimated temperature. Calculate. In calculating the corrected estimated temperature initial value, the abnormal correction estimated temperature initial value calculating means stores the temporary estimated temperature initial value. The temporary estimated temperature initial value is a temperature set in advance as a high temperature for preventing overheating. That is, the temporary estimated temperature initial value is set to a temperature at which overheating can be prevented regardless of the heat generation state of the electric motor, for example, the maximum temperature in the temperature range that the electric motor can take.

  The abnormality correction estimated temperature initial value calculating means obtains the related temperature measured by the related temperature measuring means when the abnormality of the data in the nonvolatile storage means is detected, and the temporary estimated temperature initial value is A corrected estimated initial temperature value corrected so that the initial estimated initial temperature value decreases as the value decreases is calculated.

  If the data in the non-volatile storage means is abnormal, the calculated estimated temperature becomes high when the estimated temperature is calculated using the temporary estimated temperature initial value as it is. For this reason, even if the temperature of the electric motor is actually low, the current limitation is greatly activated, and the capacity of the electric motor cannot be fully exhibited. However, if the related temperature at the start of the drive control of the electric motor is low, it can be estimated that the temperature of the electric motor is low accordingly. Therefore, in the present invention, the abnormal correction estimated initial temperature value calculation means calculates the corrected estimated initial temperature value corrected so that the temporary estimated initial temperature value decreases as the related temperature decreases. . The temperature estimating means starts calculation of the estimated temperature of the electric motor using the corrected estimated temperature initial value calculated by the abnormal correction estimated temperature initial value calculating means.

  Therefore, according to the present invention, the steering function by the electric motor can be sufficiently obtained while maintaining the overheat prevention function even when the writing failure of the estimated temperature data to the nonvolatile storage means occurs, The burden on the person is reduced.

  The estimated temperature data relating to the estimated temperature in the present invention includes not only data representing the estimated temperature itself but also data from which the estimated temperature can be derived. The steering detection means detects the steering state of the steering handle, and detects, for example, at least one of a steering torque applied to the steering handle, a steering angle of the steering handle, a steering angular velocity of the steering handle, etc. If it is.

  Another feature of the present invention is that the abnormal-time correction estimated temperature initial value calculating means stores a temporary related temperature initial value (Tbmax) set in advance to a high temperature for overheating prevention, and the temporary related temperature Based on the temperature difference (ΔT) between the initial value and the related temperature (Tb) measured by the related temperature measuring means, the corrected estimated temperature is corrected so that the temporary estimated temperature initial value decreases as the temperature difference increases. It is to calculate the initial value.

  In the present invention, the abnormality correction estimated temperature initial value calculating means stores a temporary related temperature initial value that is set in advance to a high temperature for preventing overheating. This temporary related temperature initial value is a value corresponding to the temperature that the related temperature takes when the electric motor becomes a high temperature corresponding to the temporary estimated temperature initial value, and is set corresponding to the temporary estimated temperature initial value Is. Based on the temperature difference between the temporary related temperature initial value and the related temperature measured by the related temperature measuring means, the abnormal correction estimated temperature initial value calculating means calculates the temporary estimated temperature initial value as the temperature difference (temporary related temperature The corrected estimated temperature initial value corrected so that the temporary estimated temperature initial value decreases as the initial value-measurement-related temperature increases is calculated. Therefore, a more appropriate corrected estimated temperature initial value can be calculated. As a result, it is possible to prevent overheating more appropriately and to improve the steering operability accordingly.

  Another feature of the present invention is that the related temperature data related to the related temperature measured by the related temperature measuring means at the end of the drive control of the electric motor is written in the nonvolatile storage means, and the next drive of the electric motor is performed. The related temperature data read / write means (S53, S39, S42) for reading the related temperature data stored in the nonvolatile storage means at the start of control, and the abnormality of the data in the nonvolatile storage means at the start of drive control of the electric motor. If not detected, the temperature difference (ΔT) between the related temperature (TBo) represented by the related temperature data read by the related temperature data read / write means and the related temperature (TB) measured by the related temperature measurement means. ) Based on the estimated temperature data represented by the estimated temperature data read by the estimated temperature data read / write means ( UM1o, SUM2o, SUM2o) are provided with normal correction estimated temperature initial value calculating means (S57, S58) for calculating a corrected estimated temperature initial value corrected so as to decrease as the temperature difference increases. When no abnormality is detected in the data in the nonvolatile storage means, the calculation of the estimated temperature of the electric motor is started using the corrected estimated temperature initial value calculated by the normal correction estimated temperature initial value calculating means. There is.

  In the present invention, the related temperature data read / write means, the normal correction estimated temperature initial value calculation means, and the normal temperature correction estimated temperature initial value calculation means so as to calculate a more appropriate correction estimated temperature initial value even when no abnormality of data in the nonvolatile storage means is detected. It has. The related temperature data read / write means writes the related temperature data related to the related temperature measured by the related temperature measurement means at the end of the drive control of the electric motor to the nonvolatile storage means, and stores the nonvolatile temperature at the next start of the drive control of the electric motor. Read related temperature data stored in the means.

  If the related temperature at the start of the electric motor drive control is lower than the related temperature at the end of the previous drive control of the electric motor, the temperature of the electric motor also decreases as the temperature decreases. Can be assumed. Therefore, the normal correction estimated temperature initial value calculation means is represented by the estimated temperature data read by the estimated temperature data read / write means when no abnormality of the data in the nonvolatile storage means is detected at the start of drive control of the electric motor. The estimated temperature is decreased as the temperature difference between the related temperature represented by the related temperature data read by the related temperature data reading / writing unit and the related temperature measured by the related temperature measuring unit is large. The corrected corrected estimated temperature initial value is calculated. That is, the estimated temperature at the end of the previous electric motor drive control is calculated using the temperature drop of the related temperature from the end of the previous electric motor drive control to the start of the next electric motor drive control. As the temperature drop is larger, the estimated temperature is corrected so as to decrease, and the corrected value is set as the corrected estimated temperature initial value. Therefore, a more appropriate corrected estimated temperature initial value can be calculated.

  The temperature estimating means calculates the estimated temperature of the electric motor using the corrected estimated temperature initial value calculated by the normal correction estimated temperature initial value calculating means when no abnormality of the data in the nonvolatile storage means is detected. To start. As a result, the temperature estimation accuracy of the electric motor is improved, and good overheat prevention performance and steering operation performance are obtained.

  Another feature of the present invention includes temperature measurement abnormality detection means (S54) for determining whether or not the related temperature measurement means is abnormal, and the normal correction estimated temperature initial value calculation means includes the related temperature measurement. When the abnormality of the means is detected, the estimated temperature represented by the estimated temperature data read by the estimated temperature data read / write means is set as the estimated temperature initial value without correction (S59, S58). is there.

  If the related temperature cannot be measured properly, an appropriate corrected estimated temperature initial value cannot be calculated if correction is made using the temperature drop of the related temperature. Therefore, in the present invention, in such a case, the estimated temperature at the end of the previous drive control of the electric motor is set as the estimated temperature initial value without correcting the estimated temperature. In this case, the temperature estimation means starts calculation of the estimated temperature of the electric motor using the estimated temperature initial value. Thereby, even if the related temperature measuring means is abnormal, it is possible to reliably prevent overheating.

  Another feature of the present invention includes temperature measurement abnormality detection means (S54) for determining whether or not the related temperature measurement means is abnormal, and the abnormality correction estimated temperature initial value calculation means includes the related temperature measurement. If an abnormality of the means is detected, the temporary estimated temperature initial value is set as the estimated temperature initial value without correction (S63, S62).

  In the present invention, if the data in the nonvolatile storage means is abnormal and the related temperature measuring means is abnormal, the temporary estimated temperature initial value is set as the estimated temperature initial value without correction. In this case, the temperature estimation means starts calculation of the estimated temperature of the electric motor using the estimated temperature initial value. Therefore, it is possible to reliably prevent overheating.

  In the above description, in order to help the understanding of the invention, the reference numerals used in the embodiments are attached to the configuration of the invention corresponding to the embodiments in parentheses. It is not intended to be limited to the embodiment defined by.

1 is an overall configuration diagram of an electric power steering apparatus according to an embodiment of the present invention. It is a schematic circuit block diagram showing the control system and power supply system in an electric power steering device. It is a flowchart showing an assist control routine. It is a characteristic view showing an assist torque map. It is a characteristic view showing an upper limit electric current value map. It is a flowchart showing a motor temperature estimation routine. It is a flowchart showing a data read / write control routine. It is a timing chart which shows the reading / writing timing of temperature data. It is a flowchart showing an estimated temperature initial value calculation routine.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an electric power steering device for a vehicle as an embodiment of a steering device of the present invention, and FIG. 2 schematically shows a control system and a power supply system in the electric power steering device.

  The electric power steering apparatus 1 for a vehicle can be broadly divided into a steering mechanism 10 that steers steered wheels by steering a steering handle 11, an electric motor 15 that is assembled to the steering mechanism 10 and generates a steering assist torque, and a steering handle 11. The electronic control unit 30 controls the operation of the electric motor 15 in accordance with the steering state.

  The steering mechanism 10 is a mechanism for steering the left and right front wheels FW1 and FW2 by a rotating operation of the steering handle 11, and includes a steering shaft 12 connected so as to rotate integrally with the upper end of the steering handle 11. A pinion gear 13 is connected to the lower end of the steering shaft 12 so as to rotate integrally. The pinion gear 13 meshes with rack teeth formed on the rack bar 14 to constitute a rack and pinion mechanism. Left and right front wheels FW1, FW2 are steerably connected to both ends of the rack bar 14 via tie rods and knuckle arms (not shown). The left and right front wheels FW1 and FW2 are steered left and right in accordance with the axial displacement of the rack bar 14 accompanying the rotation of the steering shaft 12 around the axis. Accordingly, the steering mechanism 10 is constituted by the steering handle 11, the steering shaft 12, the rack and pinion mechanisms 13, 14, the tie rod, the knuckle arm, and the like.

  An electric motor 15 is assembled to the steering shaft 12 via a reduction gear 16. In the present embodiment, a brush motor is used as the electric motor 15. The electric motor 15 rotationally drives the steering shaft 12 around its central axis via the reduction gear 16 by rotation of the rotor, and applies assist torque to the turning operation of the steering handle 11.

  A steering torque sensor 21 is provided on the steering shaft 12. The steering torque sensor 21 outputs a signal corresponding to the steering torque that acts on the steering shaft 12 by the turning operation of the steering handle 11. Hereinafter, the value of the steering torque detected by the signal output from the steering torque sensor 21 is referred to as steering torque Th. As for the steering torque Th, the operation direction of the steering wheel 11 is identified by a positive or negative value. In the present embodiment, the steering torque Th when the steering handle 11 is steered in the right direction is indicated by a positive value, and the steering torque Th when the steering handle 11 is steered in the left direction is indicated by a negative value. Therefore, the magnitude of the steering torque Th is the magnitude of its absolute value.

  The electric motor 15 is provided with a rotation angle sensor 23. The rotation angle sensor 23 is incorporated in the electric motor 15 and outputs a detection signal corresponding to the rotation angle position of the rotor of the electric motor 15. The detection signal of the rotation angle sensor 23 is used to calculate the rotation angle and rotation angular velocity of the electric motor 15. On the other hand, since the rotation angle of the electric motor 15 is proportional to the steering angle of the steering handle 11, it is commonly used as the steering angle of the steering handle 11. Further, the rotational angular velocity obtained by differentiating the rotational angle of the electric motor 15 with respect to time is proportional to the steering angular velocity of the steering handle 11, and thus is commonly used as the steering angular velocity of the steering handle 11.

  Hereinafter, the value of the steering angle of the steering wheel 11 detected by the output signal of the rotation angle sensor 23 is referred to as a steering angle θ, and the value of the steering angular velocity obtained by time differentiation of the steering angle θ is referred to as a steering angular velocity ω. Note that the steering angle θ and the steering angular velocity ω are calculated by the microcomputer 41 of the electronic control circuit 40 described later. The steering angle θ represents the steering angle in the right direction and the left direction with respect to the neutral position of the steering handle 11 by using positive and negative values. In the present embodiment, the neutral position of the steering handle 11 is set to “0”, the steering angle in the right direction with respect to the neutral position is indicated by a positive value, and the steering angle in the left direction with respect to the neutral position is indicated by a negative value.

  Next, the electronic control unit 30 will be described with reference to FIG. The electronic control unit 30 (hereinafter referred to as ECU 30) calculates a target energization control amount of the electric motor 15, and drives the electric motor 15 with the calculated target energization control amount, and an electronic control circuit And a motor drive circuit 32 that drives the electric motor 15 in accordance with a control command from 40.

  The electronic control circuit 40 includes a microcomputer 41 (hereinafter referred to as a microcomputer 41) composed of a CPU, ROM, RAM, and the like, an input interface 42, an output interface 43, and an EEPROM (Electric Erasable PROM) 44. The ROM in the microcomputer 41 stores a control program, various data, and the like, which will be described later.

  The input interface 42 is connected to the microcomputer 41 via a bus, and is connected to the steering torque sensor 21, the vehicle speed sensor 22, the rotation angle sensor 23, the current sensor 24, and the temperature sensor 25. A detection signal is supplied. The input interface 42 includes an A / D converter (not shown) that generates a digital signal corresponding to the power supply voltage from the power supply supplied to the electronic control circuit 40 and supplies the digital signal to the microcomputer 41. The vehicle speed sensor 22 outputs a vehicle speed signal that represents the traveling speed vx of the vehicle.

  The output interface 43 is connected to the microcomputer 41 via a bus, and is connected to the motor drive circuit 32 and a normally open type power supply relay 57, and these conductions are based on a command from the microcomputer 41. A signal for changing the state is transmitted. The EEPROM 44 is a non-volatile storage unit that stores and holds data even when the power supply from the power supply device 50 is not received, and is connected to the microcomputer 41 via a bus.

  The motor drive circuit 32 includes four switching elements Tr1 to Tr4 made of MOSFETs each having a gate connected to the output interface 43, and two resistors R1 and R2. One end of the resistor R1 is connected to the power supply line 55 of the power supply device 50, and the other end of the resistor R1 is connected to the sources of the switching elements Tr1 and Tr2. The drains of the switching elements Tr1 and Tr2 are connected to the sources of the switching elements Tr3 and Tr4, respectively, and the drains of the switching elements Tr3 and Tr4 are grounded via a resistor R2. The switching elements Tr1 and Tr3 are connected to one pole of the electric motor 15, and the switching elements Tr2 and Tr4 are connected to the other pole of the electric motor 15. A current sensor 24 is provided between the resistor R <b> 2 and the switching elements Tr <b> 3 and Tr <b> 4 and outputs a detection signal representing the current value Im flowing through the electric motor 15 to the input interface 42.

  In the motor drive circuit 32, when the switching elements Tr1 and Tr4 are selectively turned on (on state) in a state where power is supplied, a current in a predetermined direction flows through the electric motor 15 and the motor 15 When the motor rotates clockwise and the switching elements Tr2 and Tr3 are selectively turned on, a current in the direction opposite to the predetermined direction flows through the electric motor 15 and the motor 15 rotates counterclockwise.

  Further, the motor drive circuit 32 is provided with a temperature sensor 25 constituted by a thermistor or the like for detecting the temperature of the circuit board on which the switching elements Tr1 to Tr4 are provided. The temperature sensor 25 detects a substrate temperature Tb that is a temperature corresponding to the heat generation state of the switching elements Tr1 to Tr4, and outputs a signal representing the substrate temperature Tb. Further, the heat generation state of the switching elements Tr <b> 1 to Tr <b> 4 is related to the heat generation state of the electric motor 15. That is, the greater the amount of heat generated by the electric motor 15, the higher the substrate temperature Tb. Accordingly, the substrate temperature Tb corresponds to the “related temperature” in the present invention, and the temperature sensor 25 corresponds to the related temperature measuring means in the present invention.

  Next, a power supply circuit configuration to the electronic control circuit 40 and the motor drive circuit 32 will be described with reference to FIG. The ECU 30 is supplied with power from a power supply device 50 including a battery 51 and an alternator 52 that generates electric power by rotating the engine. As the battery 51, a general in-vehicle battery having a rated output voltage of 12V is used.

  The power supply device 50 commonly supplies power not only to the electric power steering device 1 but also to other in-vehicle electric loads including an engine starter and the like. An ignition switch 60 is connected to the power supply source line 53 connected to the power supply terminal (+ terminal) of the battery 51. The ECU 30 includes a control power supply line 54 that supplies power to the electronic control circuit 40 from the secondary side of the ignition switch 60, and a drive power supply that supplies power mainly to the motor drive circuit 32 from the primary side (power side) of the ignition switch 60. And a supply line 55.

  The control power supply line 54 is provided with a diode 56. The diode 56 is a backflow prevention element that is provided with the cathode facing the electronic control circuit 40 and the anode facing the power supply device 50 and can be energized only in the power supply direction. The drive power supply line 55 is provided with a power relay 57 in the middle thereof. The power supply relay 57 is turned on by a control signal from the electronic control circuit 40 to form a power supply circuit to the electric motor 15.

  The drive power supply line 55 is connected to the control power supply line 54 via a connecting line 58 on the load side of the power relay 57. The connection line 58 is connected between the diode 56 and the electronic control circuit 40 in the control power supply line 54. A diode 59 is connected to the connecting line 58. The diode 59 is provided with a cathode facing the control power supply line 54 side and an anode facing the drive power supply line 55 side, and a backflow prevention element capable of energizing only from the drive power supply line 55 to the control power supply line 54. It is. In the power supply system configured as described above, when the power relay 57 is turned on, power is supplied to the electronic control circuit 40 and the motor drive circuit 32 regardless of the state of the ignition switch 60. ing.

  Next, processing performed by the ECU 30 will be described. The ECU 30 includes an assist control process that provides an appropriate assist torque to the steering wheel operation by the driver, a motor temperature estimation process that estimates and calculates a motor temperature to prevent overheating of the electric motor 15 during the assist control, Data indicating the estimated motor temperature and the substrate temperature Tb is written to the EEPROM 44 when the control is finished, and the data read / write control process for reading the data when the next assist control is started, and the estimation of the electric motor 15 from the read data. An estimated temperature initial value calculation process for calculating the temperature initial value is performed.

  First, assist control processing executed by the ECU 30 will be described. FIG. 3 shows an assist control routine performed by the microcomputer 41. The assist control routine is stored in the ROM of the microcomputer 41 as a control program and repeatedly executed in a short cycle. This control routine is started when the ignition switch 60 is turned on and a predetermined initial diagnosis is completed, and is executed in parallel with a motor temperature estimation routine described later.

  When this control routine is activated, the microcomputer 41 first reads the vehicle speed vx detected by the vehicle speed sensor 22 and the steering torque Th detected by the steering torque sensor 21 in step S11.

  Subsequently, with reference to the assist torque table shown in FIG. 4, a basic assist torque Tas set according to the input vehicle speed vx and steering torque Th is calculated (S12). The assist torque table is stored in the ROM of the microcomputer 41, and is set so that the basic assist torque Tas increases as the steering torque Th increases, and increases as the vehicle speed vx decreases.

  The characteristic graph of FIG. 4 shows only the relationship between the positive region, that is, the steering torque Th in the right direction and the basic assist torque Tas, but the negative region, that is, the left direction steering torque Th and the basic assist torque Tas, 4 is moved to a point-symmetrical position around the origin. In the present embodiment, the basic assist torque Tas is calculated using the assist torque table, but a function that defines the basic assist torque Tas that changes according to the steering torque Th and the vehicle speed vx instead of the assist torque table. May be prepared, and the basic assist torque Tas may be calculated using the function. Further, the calculation of the basic assist torque Tas is not necessarily calculated from the combination of the vehicle speed vx and the steering torque Th, and may be performed based on at least a detection signal corresponding to the steering state.

  Subsequently, in step S13, the microcomputer 41 calculates the target torque T * by adding the compensation torque to the basic assist torque Tas. This compensation torque is a torque for compensating the basic assist torque Tas, and is not necessarily required. For example, the sum of the return torque and the damping torque can be used. The return torque is set so that a good assist torque works toward the neutral position when the driver turns back while loosening the handle of the steering handle 11, and is set according to the steering angle θ. Further, the damping torque attenuates vibrations in the entire steering system and is set according to the steering angular velocity ω. In this calculation, the rotation angle θ of the electric motor 15 detected by the rotation angle sensor 23 and the angular velocity ω of the electric motor 15 (corresponding to the steering angular velocity ω obtained by differentiating the steering angle θ of the steering handle 11 with respect to time) are input. calculate.

  Subsequently, in step S14, the microcomputer 41 calculates a necessary current I * necessary for generating the target torque T *. The required current I * is obtained by dividing the target torque T * by the torque constant.

  Subsequently, in step S15, the microcomputer 41 reads the latest estimated motor temperature Tm calculated in a motor temperature estimation routine described later. Next, in step S16, an upper limit current value Imax for energizing the electric motor 15 from the estimated motor temperature Tm is set. The upper limit current value Imax is obtained with reference to the upper limit current value map shown in FIG. This upper limit current value map is stored in the ROM of the microcomputer 41, and the upper limit current value Imax is set to a smaller value as the estimated motor temperature Tm is higher. The upper limit current value Imax represents an absolute value that is not related to the magnitude, that is, the direction in which the current flows.

  Subsequently, the microcomputer 41 advances the process to step S17, and obtains a final target current I ** from the necessary current I * calculated in step S14 and the upper limit current value Imax calculated in step S16. If the magnitude (absolute value) of the required current I * is less than or equal to the upper limit current value Imax, the target current I ** is set to the same value as the required current I *, and the magnitude of the required current I * is equal to the upper limit current value Imax. If it is larger, the target current I ** is set to the same magnitude as the upper limit current value Imax.

Subsequently, the microcomputer 41 advances the process to step S18, calculates a deviation ΔI between the target current I ** and the actual current Im, and performs a target command voltage V * by PI control (proportional integral control) based on the deviation ΔI. Calculate The actual current Im used for the calculations in steps S15 and S18 is a current value flowing through the electric motor 15 detected by the current sensor 24.
The target command voltage V * is calculated by the following formula, for example.
V * = Kp · ΔI + Ki · ∫ΔI dt
Here, Kp is a control gain of a proportional term in PI control, and Ki is a control gain of an integral term in PI control.

  In step S19, the microcomputer 41 outputs a PWM control voltage signal corresponding to the target command voltage V * to the motor drive circuit 32, and temporarily ends the assist control routine. This control routine is repeatedly executed at a predetermined short cycle. Therefore, by executing this control routine, the duty ratio of the switching elements Tr1 to Tr4 of the motor drive circuit 32 is controlled by the PWM control, and a steering assist torque corresponding to the driver's steering operation is obtained. Further, in this assist control, a current limit corresponding to the estimated motor temperature Tm is added, so that overheating damage of the electric motor 15 and the motor drive circuit 32 can be prevented.

  In the assist control routine, a process of detecting the substrate temperature Tb by the temperature sensor 25 and setting the upper limit current value Ibmax based on the substrate temperature Tb may be added to the process of step S18. In this case, the microcomputer 41 uses a map similar to the upper limit current value map shown in FIG. 5 (the horizontal axis is Tb, the vertical axis is Ibmax), and the upper limit current value Ibmax is set to a smaller value as the substrate temperature Tb is higher. . Then, the smaller one of the upper limit current value Imax set from the estimated motor temperature Tm and the upper limit current value Ibmax set from the substrate temperature Tb is set as the upper limit current value Imax. Therefore, in a system in which the switching elements Tr1 to Tr4 of the motor drive circuit 32 approach the overheat prevention temperature before the electric motor 15, the motor drive circuit 32 can be prevented from overheating.

  Next, the motor temperature estimation process will be described. FIG. 6 shows a motor temperature estimation routine performed by the microcomputer 41, which is stored as a control program in the ROM of the microcomputer 41 and repeatedly executed in a short cycle. This routine is started when the ignition switch 60 is turned on and a predetermined initial diagnosis is completed, and ends when a data read / write control routine described later ends.

When the motor temperature estimation routine is started, the microcomputer 41 first reads the current value Im flowing through the electric motor 15 detected by the current sensor 24 in step S21. Subsequently, in Step S22, a heat mass temperature estimation current square integrated value SUM1 (hereinafter referred to as a heat mass temperature value SUM1) is calculated. The heat mass temperature value SUM1 represents a value corresponding to the rising temperature of the casing of the electric motor 15, and is calculated by the following equation (1).
SUM1 (n) = SUM1 (n -1) + Ka1 · (Im 2 -SUM1 (n-1)) ···· (1)

  Here, Ka1 is a preset coefficient that represents the degree to which the casing of the electric motor 15 changes in temperature according to the square value of the current value Im. Further, (n) means a value calculated by the current process in the motor temperature estimation routine repeatedly executed around a predetermined short surrounding, and (n-1) is 1 in the motor temperature estimation routine. It means the value calculated in the process before the calculation cycle. Therefore, SUM1 (n) is the heat mass temperature value SUM1 to be obtained by this calculation, and SUM1 (n-1) is the heat mass temperature value SUM1 calculated one calculation cycle before. In the following description, (n) and (n-1) are not described when it is not necessary to specify the calculation cycle.

Subsequently, in step S23, the microcomputer 41 calculates a coil temperature estimation current square integrated value SUM2 (hereinafter referred to as a coil temperature value SUM2). The coil temperature value SUM2 represents a value corresponding to the rising temperature of the coil of the electric motor 15, and is calculated by the following equation (2).
SUM2 (n) = SUM2 (n -1) + Ka2 · (Im 2 -SUM2 (n-1)) ···· (2)
Here, Ka2 is a preset coefficient representing the degree to which the temperature of the coil of the electric motor 15 changes according to the square value of the current value Im.

Subsequently, in step S24, the microcomputer 41 calculates a brush temperature estimation current square integrated value SUM3 (hereinafter referred to as a brush temperature value SUM3). The brush temperature value SUM3 represents a value corresponding to the rising temperature of the brush of the electric motor 15, and is calculated by the following equation (3).
SUM3 (n) = SUM3 (n -1) + Ka3 · (Im 2 -SUM3 (n-1)) ···· (3)
Here, Ka3 is a preset coefficient representing the degree of temperature change of the brush of the electric motor 15 according to the square value of the current value Im.

Subsequently, in step S25, the microcomputer 41 calculates the estimated motor temperature Tm. The estimated motor temperature Tm represents the temperature rise due to the heat generated by the electric motor 15, and based on the heat mass temperature value SUM1 (n), the coil temperature value SUM2 (n), and the brush temperature value SUM3 (n), the following equation (4) Is calculated by
Tm = Kb1 · SUM1 (n) + Kb2 · SUM2 (n) + Kb3 · SUM3 (n)
.... (4)
Here, Kb1, Kb2, and Kb3 are rising temperature conversion coefficients in consideration of the degree (gain) that the heat mass temperature value SUM1, the coil temperature value SUM2, and the brush temperature value SUM3 affect the estimated motor temperature.

  Thus, in the present embodiment, the heat generated by the electric motor 15 is divided into a heat generating element in the housing, a heat generating element in the coil, and a heat generating element in the brush, and a value obtained by multiplying the temperature rise for each heat generating element by the gain. Is added to calculate the estimated motor temperature Tm, so the estimation accuracy is high.

  In the present embodiment, the estimated motor temperature Tm represents the temperature rise due to the heat generated by the electric motor 15, and does not represent the temperature of the electric motor 15 itself. For example, an outside air temperature sensor is provided, The temperature of the electric motor 15 itself may be estimated such that a value obtained by adding the temperature increase of the electric motor 15 to the outside air temperature detected by the outside air temperature sensor is used as the estimated motor temperature. This is because it is possible to prevent overheating in either case.

  Subsequently, in step S26, the microcomputer 41 calculates the heat mass temperature value SUM1 (n), the coil temperature value SUM2 (n), and the brush temperature value SUM3 (n) calculated this time as the heat mass temperature value SUM1 (n -1), coil temperature value SUM2 (n-1), and brush temperature value SUM3 (n-1). This process is performed for the calculation process of steps S42, S43, and S44 after one calculation cycle.

  After performing the process of step S26, the microcomputer 41 once ends the motor temperature estimation routine. Since the motor temperature estimation routine is repeatedly executed at a predetermined short cycle, the estimated motor temperature Tm is sequentially calculated every predetermined time. The latest estimated motor temperature Tm sequentially calculated in this way is used to determine the motor upper limit current value Imax in the assist control (S16).

  In calculating the estimated motor temperature Tm, it is not possible to estimate only the amount of heat generated by the electric motor 15 from the start of the assist control, but the heat remaining in the electric motor 15 at the start of the assist control must also be taken into consideration. Therefore, initial values of the heat mass temperature value SUM1, the coil temperature value SUM2, and the brush temperature value SUM3 are required. Therefore, in the present embodiment, at the end of the assist control routine, the heat mass temperature value SUM1, the coil temperature value SUM2, the brush temperature value SUM3, and the temperature data representing the substrate temperature Tb detected by the temperature sensor 25 are obtained. The temperature data stored in the EEPROM 44 is read when writing to the EEPROM 44 and starting the next assist control routine. And the initial value of heat mass temperature value SUM1, coil temperature value SUM2, and brush temperature value SUM3 is calculated by executing an estimated temperature initial value calculation routine, which will be described later, based on the value represented by the temperature data.

  In this embodiment, in order to calculate the estimated motor temperature Tm based on the heat mass temperature value SUM1, the coil temperature value SUM2, and the brush temperature value SUM3, the heat mass temperature value SUM1, the coil temperature value SUM2, and the brush temperature value SUM3 are set as one set. The obtained data is data representing the estimated motor temperature Tm. Therefore, hereinafter, the heat mass temperature value SUM1, the coil temperature value SUM2, and the brush temperature value SUM3 stored in the EEPROM 44 are collectively referred to as motor estimated temperature data. Further, the substrate temperature Tb data stored in the EEPROM 44 is referred to as substrate temperature data Tb, and when the temperature value represented by the substrate temperature data Tb is indicated, the value is referred to as the substrate temperature Tbo.

  Next, data read / write control processing executed by the microcomputer 41 will be described. FIG. 7 shows a data read / write control routine executed by the microcomputer 41. This routine is stored as a control program in the ROM of the microcomputer 41 and is activated when the ignition switch 60 is turned on. FIG. 8 is a timing chart showing the processing in time series.

  When the ignition switch 60 is switched from the off state to the on state, power is supplied from the power supply device 50 to the ECU 30. When receiving the power supply, the microcomputer 41 starts this control routine (time t0), and first performs an initial diagnosis in step S31. That is, in-system diagnosis and initial setting in the electric power steering apparatus 1 are performed.

  Subsequently, in step S50, the microcomputer 41 performs an estimated temperature initial value calculation process (time t1). This estimated temperature initial value calculation process will be described later using an estimated temperature initial value calculation routine shown in FIG. In the estimated temperature initial value calculation routine, motor estimated temperature data (heat mass temperature value SUM1, coil temperature value SUM2, brush temperature value SUM3) and substrate temperature data Tb are read from EEPROM 44, and motor estimated temperature Tm is calculated based on these data. Calculate initial values ((heat mass temperature value SUM1 (n-1), coil temperature value SUM2 (n-1), brush temperature value SUM3 (n-1)) for calculation. Estimated temperature initial value calculation processing Is performed at the time of initial diagnosis of the electric power steering apparatus 1.

  When the initial diagnosis is completed, the microcomputer 41 starts the assist control described above in step S32 (time t2). At the start of the assist control, the power relay 57 is turned on to form a power supply circuit to the electric motor 15. At this time, motor temperature estimation processing is also started in parallel with the assist control.

  When the assist control is started, the microcomputer 41 first determines in step S33 whether or not the flag F is “1”. This flag F is set to F = 0 when this control routine is started, and is set to F = 1 when provisional temperature data is written in the EEPROM 44 by the process of step S35 described later. Immediately after the start of the assist control, since F = 0 is set, the determination in step S33 is “NO”, and the microcomputer 41 advances the process to step S34.

  In step S34, it is determined whether or not the provisional temperature data is written. This write timing is set, for example, when a set time (for example, several seconds) has elapsed since the estimated temperature initial value calculation process (S50). Therefore, it is determined here whether or not the elapsed time since the estimated temperature initial value calculation process (S50) has reached the set time. If it is not the write timing, the microcomputer 41 proceeds to step S37 to determine whether or not the ignition switch 60 is turned off. While the ignition switch 60 remains on, the process returns to step S33 and the above-described determination is repeated.

  When such determination is repeated and the writing timing of the temporary temperature data comes (S34: Yes), the microcomputer 41 reads the temporary temperature data stored in advance in the ROM and writes it in the EEPROM 44 (time t3). In the EEPROM 44, temperature data including motor estimated temperature data (heat mass temperature value SUM1, coil temperature value SUM2, brush temperature value SUM3) and substrate temperature data Tb at the end of assist control in steps S39 and S42 to be described later. Has been written. Then, using this temperature data, the estimated motor temperature Tm is calculated by the estimated temperature initial value calculation process in step S50. Therefore, in step S35, the temperature data written at the end of the previous assist control is rewritten to temporary temperature data.

  The process of step S35 is a process performed in preparation for a situation where the microcomputer 41 resets during the assist control and information indicating the estimated motor temperature Tm disappears. Only when such a situation occurs, the next assist is performed. Temporary temperature data is used as an initial value for calculating the estimated motor temperature Tm at the start of control.

  This temporary temperature data is composed of a temporary heat mass temperature value SUM1max, a temporary coil temperature value SUM2max, a temporary brush temperature value SUM3max, and a temporary substrate temperature Tbmax. The motor estimated temperature Tm is set to a high temperature from the viewpoint of preventing overheating. It is set to a value that can be calculated. That is, the temporary heat mass temperature value SUM1max, the temporary coil temperature value SUM2max, and the temporary brush temperature value SUM3max are substituted and used for SUM1 (n), SUM2 (n), and SUM3 (n) in the calculation formula (4) in step S25. The estimated motor temperature Tm obtained by substituting SUM1max, SUM2max, and SUM3max is a high temperature that prevents overheating regardless of the heat generation state of the electric motor 15 (overheating prevention). High temperature). That is, it is set to a value corresponding to the maximum temperature that the electric motor 15 can take.

  The temporary substrate temperature Tbmax is a value corresponding to the temperature taken by the substrate temperature Tb when the electric motor 15 becomes the estimated motor temperature Tm calculated by using SUM1max, SUM2max, and SUM3max. The temperature is set in advance so that Tb reaches the highest possible temperature. The process of step S35 is a safety measure because it is not known what heat generation state the electric motor 15 has when the microcomputer 41 is reset and the assist control is interrupted.

  When the microcomputer 41 completes the writing of the temporary temperature data to the EEPROM 44 in step S35, the microcomputer 41 sets the flag F to F = 1 in the subsequent step S36. Therefore, after that, the determination in step S33 is “YES”, and the determination of the OFF state of the ignition switch 60 in step S37 is continued.

  When the ignition switch 60 is operated and an off state is detected (time t4), the assist control is terminated in step S38. Therefore, thereafter, the electric motor 15 is not driven and controlled. Subsequently, in step S39, the microcomputer 41 writes the estimated motor temperature data (SUM1, SUM2, SUM3) at the end of the assist control and the substrate temperature data Tb representing the substrate temperature detected by the temperature sensor 25 in the EEPROM 44. . Therefore, the temporary temperature data written in the EEPROM 44 in the previous step S35 is rewritten with the temperature data (SUM1, SUM2, SUM3, Tb) at the end of the assist control.

  Subsequently, the microcomputer 41 starts a timer in step S40, and determines whether a predetermined time (for example, 10 minutes) has elapsed in step S41. When the assist control is finished and the passage of a predetermined time is confirmed (S41: YES), in step S42, the microcomputer 41 determines the motor estimated temperature data (SUM1, SUM2, SUM3) at that time, and the substrate temperature. Data Tb is written to the EEPROM 44 (time t5). The microcomputer 41 calculates the estimated motor temperature Tm by the motor temperature estimation routine even after the end of the assist control. In this case, since the electric motor 15 is in a state where no current flows for a predetermined time or longer, the estimated motor temperature Tm and the substrate temperature Tb represented by the estimated motor temperature data are smaller than the values in step S39. .

  Thus, the temperature data stored in the EEPROM 44 in the previous step S39 is finally rewritten with the temperature data after the predetermined time has elapsed. This temperature data (SUM1, SUM2, SUM3, Tb) is read in the estimated temperature initial value calculation process in step S50 when the next ignition switch 60 is turned on, and estimated motor temperature data (SUM1, SUM2, SUM3). Used to calculate the initial value of.

  When the writing of the temperature data to the EEPROM 44 is completed in step S42, the microcomputer 41 turns off the power supply relay 57 in step S43 and ends all the processes. When the ignition switch 60 is switched on during a predetermined time waiting (time t4 to t5), the microcomputer 41 starts the initial diagnosis (S31) without writing the final temperature data. Start processing.

  Next, the estimated temperature initial value calculation process will be described. FIG. 9 shows an estimated temperature initial value calculation routine executed by the microcomputer 41. This estimated temperature initial value calculation routine is incorporated as a subroutine of step S50 in the data read / write control routine.

  When the estimated temperature initial value calculation routine starts, the microcomputer 41 first reads the temperature data (SUM1, SUM2, SUM3, Tb) stored in the EEPROM 44 in step S51. Subsequently, in step S52, the temperature data state is checked using a check sum (Check Sum: error detection code).

  The EEPROM 44 is provided with four temperature data fields for separately storing the heat mass temperature value SUM1, the coil temperature value SUM2, the brush temperature value SUM3, and the substrate temperature Tb, and a checksum field for storing the checksum. Yes. When the microcomputer 41 writes the temperature data (SUM1, SUM2, SUM3, Tb) to the EEPROM 44, the microcomputer 41 writes the heat mass temperature value SUM1SUM1, the coil temperature value SUM2, the brush temperature value SUM3, and the substrate temperature Tb in order to each temperature data field. Also, a checksum is calculated from the temperature data (SUM1, SUM2, SUM3, Tb), and the calculated checksum is written in the checksum field.

  In step S52, the microcomputer 41 calculates the checksum of the temperature data (SUM1, SUM2, SUM3, Tb) read from the EEPROM 44, and determines whether this checksum is the same as the value stored in the checksum field. Is determined as to whether or not the state of the temperature data (SUM1, SUM2, SUM3, Tb) is normal.

  For example, when the ignition switch 60 is turned on and the cranking operation is performed while the assist control is finished and the temperature data is being written to the EEPROM 44, the microcomputer 41 causes the temporary voltage drop of the battery 51 to It may reset. In such a case, the temperature data cannot be correctly written in the EEPROM 44. Therefore, in step S52, the microcomputer 41 determines whether there is an abnormality in the temperature data (SUM1, SUM2, SUM3, Tb) using a checksum.

  Subsequently, the microcomputer 41 reads the current substrate temperature Tb detected by the temperature sensor 25 in step S53. Subsequently, in step S54, it is checked whether or not an abnormality has occurred in the temperature sensor 25. For example, the abnormality of the temperature sensor 25 is determined by detecting a state in which the substrate temperature Tb detected by the temperature sensor 25 becomes an abnormal value exceeding a range assumed in advance, an abnormality (disconnection, short circuit), or the like of the power supply line. .

  Further, although not necessarily a sensor abnormality, it is determined that a sensor abnormality is present for convenience when the estimated motor temperature should not be corrected in accordance with the substrate temperature Tb. The situations that should not be corrected include the situation where the substrate temperature Tb detected by the temperature sensor 25 is higher than the preset estimated temperature correction permission substrate temperature, and the substrate temperature Tb detected by the temperature sensor 25. The temperature is set higher than the substrate temperature Tbo represented by the substrate temperature data Tb read from the EEPROM 44.

  Subsequently, in step S55, the microcomputer 41 determines whether or not the temperature data is normal based on the check result of the temperature data. If the temperature data is normal, the temperature sensor 25 is normal in the subsequent step S56. It is determined whether or not. If both the temperature data and the temperature sensor 25 are normal, a substrate temperature change value ΔT is calculated in step S57. In this case, the substrate temperature change value ΔT is a value obtained by subtracting the substrate temperature Tb detected by the temperature sensor 25 in step S53 from the substrate temperature Tbo which is the temperature value represented by the substrate temperature data Tb stored in the EEPROM 44 (Tbo). -Tb).

Subsequently, in step S58, the microcomputer calculates an initial value SUM1 (n-1) for calculating the heat mass temperature value SUM1 by the following equation (5), and an initial value SUM2 () for calculating the coil temperature value SUM2. n-1) is calculated by the following equation (6), and an initial value SUM3 (n-1) for calculating the brush temperature value SUM3 is calculated by the following equation (7).
SUM1 (n-1) = SUM1o-α · ΔT (5)
SUM2 (n−1) = SUM2o−β · ΔT (6)
SUM3 (n−1) = SUM3o−γ · ΔT (7)

  Here, SUM1o represents the value of the heat mass temperature value SUM1 stored in the EEPROM 44, SUM2o represents the value of the coil temperature value SUM2 stored in the EEPROM 44, and SUM3o represents the brush temperature stored in the EEPROM 44. The value SUM3 is represented. Α, β, and γ are preset correction coefficients (for example, 0.5). The correction coefficients α, β, and γ are preferably set to different values in accordance with the characteristics of the heat generating elements, but may be set to the same value. Further, the correction coefficients α, β, and γ are not necessarily fixed values, and may be changed according to the substrate temperature change value ΔT.

  The initial values SUM1 (n-1), SUM2 (n-1), and SUM3 (n-1) calculated in this way are the first steps S22 and S23 when the above-described motor temperature estimation routine (FIG. 6) is started. , S24. Thereby, in step S25, the estimated motor temperature Tm is calculated.

  In step S58, the initial values SUM1 (n-1), SUM2 (n-1), and SUM3 (n-1) are increased as the substrate temperature change value ΔT increases in accordance with the substrate temperature change value ΔT. It is calculated by correcting values (SUM1o, SUM2o, SUM3o) stored in the EEPROM 44 so as not to decrease. This means that the larger the substrate temperature change value ΔT (the lower the detected substrate temperature Tb), the smaller the initial value of the estimated motor temperature Tm is corrected. The temperature of the electric motor 15 is related to the substrate temperature Tb. Therefore, if the substrate temperature Tb is lower than the substrate temperature Tbo at the end of the previous assist control at the start of the assist control, it is estimated that the substrate temperature Tb decreases in proportion to the amount of decrease. Therefore, the values (SUM1o, SUM2o, SUM3o) related to the calculation of the estimated motor temperature Tm are reduced by a temperature proportional to the substrate temperature change value ΔT. As a result, an appropriate estimated motor temperature Tm can be calculated.

On the other hand, if it is determined that the temperature sensor 25 is abnormal (S56: No), the substrate temperature change value ΔT is set to zero (ΔT = 0) in step S59, and the above equations (5) to (7) are set. ) Are used to calculate initial values SUM1 (n-1), SUM2 (n-1), and SUM3 (n-1). Therefore, in this case, the initial values SUM1 (n−1), SUM2 (n−1), and SUM3 (n−1) are not corrected by the substrate temperature change value ΔT and are stored in the EEPROM 44 as shown in the following equation. The stored heat mass temperature value SUM1o, coil temperature value SUM2o, and brush temperature value SUM3o are set to the same values.
SUM1 (n-1) = SUM1o
SUM2 (n-1) = SUM2o
SUM3 (n-1) = SUM3o

  If it is determined in step S55 that the temperature data in the EEPROM 44 is abnormal, it is determined in step S60 whether or not the temperature sensor 25 is normal. If it is determined that the temperature sensor 25 is normal (S60: Yes), that is, if the temperature data is abnormal and the temperature sensor 25 is normal, in step S61, the substrate temperature change value is determined. ΔT is calculated. In this case, the microcomputer 41 reads the temporary substrate temperature Tbmax stored in advance in the ROM, and subtracts the substrate temperature Tb detected by the temperature sensor 25 in step S53 from the temporary substrate temperature Tbmax (Tbmax−Tb). ) Is set to the substrate temperature change value ΔT. The temporary substrate temperature Tbmax is set in advance so as to be the highest temperature that the substrate temperature Tb can take, and may be the same as that used in step S35.

Subsequently, in step S62, the microcomputer calculates an initial value SUM1 (n-1) for calculating the heat mass temperature value SUM1 by the following equation (8), and an initial value SUM2 ( n-1) is calculated by the following equation (9), and an initial value SUM3 (n-1) for calculating the brush temperature value SUM3 is calculated by the following equation (10).
SUM1 (n−1) = SUM1max−α · ΔT (8)
SUM2 (n−1) = SUM2max−β · ΔT (9)
SUM3 (n-1) = SUM3max−γ · ΔT (10)

  Here, SUM1max, SUM2max, and SUM3max are the temporary heat mass temperature value SUM1max, the temporary coil temperature value SUM2max, and the temporary brush temperature value SUM3max that are stored in advance in the ROM, and the temperature at which the estimated motor temperature Tm is high in order to prevent overheating. It is set to a value that can be calculated. The temporary heat mass temperature value SUM1max, the temporary coil temperature value SUM2max, and the temporary brush temperature value SUM3max may be the same as those used in step S35.

  The initial values SUM1 (n-1), SUM2 (n-1), and SUM3 (n-1) calculated in this way are the first steps S22 and S23 when the above-described motor temperature estimation routine (FIG. 6) is started. , S24. Thereby, in step S25, the estimated motor temperature Tm is calculated.

  As described above, when the microcomputer 41 is reset while the temperature data is being written to the EEPROM 44, the correct temperature data is not written to the EEPROM 44. Therefore, in step S62, instead of the estimated motor temperature data of the EEPROM 44, the provisional heat mass temperature value SUM1max, provisional coil temperature set to a high temperature that can prevent overheating regardless of the heat generation state of the electric motor 15 The value SUM2max and the temporary brush temperature value SUM3max are used.

  In this case, when the estimated motor temperature Tm is calculated using the temporary temperature values SUM1max, SUM2max, and SUM3max as they are, the upper limit current value Imax in the assist control is actually set low even when the electric motor 15 is in a low temperature state, and the handle The operation becomes heavy and the burden on the driver increases.

  Therefore, in calculating the estimated motor temperature Tm, the microcomputer 41 uses a substrate temperature change value ΔT (Tbmax−Tb) obtained by subtracting the substrate temperature Tb detected by the temperature sensor 25 from the preset temporary substrate temperature Tbmax. Values obtained by correcting the temporary temperature values SUM1max, SUM2max, and SUM3max are set as initial values SUM1 (n-1), SUM2 (n-1), and SUM3 (n-1). Therefore, the estimated motor temperature Tm is corrected to be smaller as the substrate temperature change value ΔT is larger (as the detected substrate temperature Tb is lower).

  The substrate temperature change value ΔT (Tbmax−Tb) is larger than the substrate temperature change value ΔT (Tbo−Tb) calculated in step S57, but the temporary temperature values SUM1max, SUM2max, and SUM3max are the highest in each part. Since the temperature is set to a value corresponding to the temperature, and the temporary temperature values SUM1max, SUM2max, and SUM3max are corrected by the substrate temperature change value ΔT (Tbmax−Tb), the calculated estimated motor temperature Tm is an appropriate value. Therefore, even if the temperature data cannot be written in the EEPROM 44 and the estimated motor temperature Tm is calculated using the temporary temperature values SUM1max, SUM2max, and SUM3max, the overheat prevention function can be maintained and the steering assist by the electric motor 15 is sufficient. can get. For this reason, it is convenient for the driver.

On the other hand, if it is determined in step S60 that the temperature sensor 25 is abnormal, the substrate temperature change value ΔT is set to zero (ΔT = 0) in step S63, and the above equations (8) to (10) are set. Are used to calculate initial values SUM1 (n-1), SUM2 (n-1), and SUM3 (n-1). Therefore, in this case, the initial values SUM1 (n-1), SUM2 (n-1), and SUM3 (n-1) are not corrected by the substrate temperature change value ΔT and are read from the ROM as shown in the following equation. The read provisional heat mass temperature value SUM1max, provisional coil temperature value SUM2max, and provisional brush temperature value SUM3max are set to the same values.
SUM1 (n-1) = SUM1max
SUM2 (n-1) = SUM2max
SUM3 (n-1) = SUM3max

  When the microcomputer 41 calculates the initial values SUM1 (n-1), SUM2 (n-1), and SUM3 (n-1) in step S58 or step S62, the estimated temperature initial value calculation routine is terminated. Therefore, when the motor temperature estimation routine (FIG. 6) is started, in steps S22 to S24, the heat mass is calculated using these initial values SUM1 (n-1), SUM2 (n-1), and SUM3 (n-1). Temperature value SUM1, coil temperature value SUM2, and brush temperature value SUM3 are calculated. In step S25, estimated motor temperature Tm is calculated from these calculated values.

According to the electric power steering apparatus 1 of the present embodiment described above, the following effects are obtained.
1. Since the temperature of the electric motor 15 is estimated and the upper limit current value Imax that can be passed to the electric motor 15 is set based on the estimated temperature Tm, overheating of the electric motor 15 and the motor drive circuit 32 can be prevented. it can.

2. In estimating the temperature of the electric motor 15, the temperature data stored in the EEPROM 44 is checked. If the temperature data is abnormal, the temporary temperature data (SUM1max, SUM2max, Since the calculation of the estimated motor temperature Tm is started using SUM3max), overheating can be reliably prevented even in such a case.

3. If the temperature data is abnormal, the substrate temperature change value ΔT (Tbmax−Tb) is used to correct the initial value SUM1 (n−) so as to decrease as the substrate temperature change value ΔT (Tbmax−Tb) increases. 1), SUM2 (n-1), SUM3 (n-1) are used to start the calculation of the estimated motor temperature Tm (S61, S62). Therefore, the steering assist function by the electric motor 15 is maintained while maintaining the overheat prevention function. Is sufficiently obtained and the burden on the driver is reduced.

4). If an abnormality of the temperature sensor 25 is detected, temperature correction based on the substrate temperature change value ΔT (Tbmax−Tb) is not performed (S63), so that overheating can be reliably prevented. In this case, since the steering wheel operation becomes heavy, the driver can be made aware of the abnormality.

5. If the temperature data is normal, the substrate temperature change value ΔT (Tbo−Tb) is used to correct the initial value SUM1 (n−) so as to decrease as the substrate temperature change value ΔT (Tbo−Tb) increases. Since the calculation of the estimated motor temperature Tm is started using 1), SUM2 (n-1), and SUM3 (n-1) (S57 to S58), the estimated motor temperature Tm can be set to an optimum value. Thereby, the current limitation of the electric motor 15 is more appropriately performed, and good overheat prevention performance and steering operation performance can be obtained.

6). Even if the temperature data is normal, if an abnormality of the temperature sensor 25 is detected, temperature correction based on the substrate temperature change value ΔT (Tbo−Tb) is not performed (S59), so that overheating can be reliably prevented. it can.

7). In estimating the motor temperature, the heat generated by the electric motor 15 is divided into a heat generating element in the housing, a heat generating element in the coil, and a heat generating element in the brush, and a value obtained by multiplying the rising temperature for each heat generating element by a gain is added. Since the estimated motor temperature Tm is calculated (S22 to S25), the estimation accuracy is high. In addition, in calculating the initial values SUM1 (n-1), SUM2 (n-1), and SUM3 (n-1), the correction coefficients α, β, and γ are set for each heating element (S58, S62). ), Each can be set to an optimum value. As a result, accurate overheating can be prevented.

8). In preparation for a situation where the estimated temperature data is lost due to the reset of the microcomputer 41 during the assist control, the temporary temperature data is written in the EEPROM 44, so that overheating can be reliably prevented (S35).

  The electric power steering apparatus according to the present embodiment has been described above. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the object of the present invention.

  For example, in the present embodiment, the heat generation of the electric motor 15 is divided into three heat generation elements, and the estimated motor temperature Tm is calculated from the respective temperature rises. However, it is not always necessary to divide the heat generation elements into such heat generation elements. It may be calculated simply by the integrated value of the square of the current flowing through the electric motor 15.

  In the present embodiment, the provisional temperature values SUM1max, SUM2max, and SUM3max are corrected using the substrate temperature Tb. However, the substrate temperature Tb is not necessarily used, and the temperature changes with the temperature change of the electric motor 15. You may make it correct | amend using the temperature of the site | part which changes and detecting that temperature. For example, a temperature sensor may be provided in the vicinity of the electric motor 15 and correction may be made using the motor ambient temperature detected by the temperature sensor.

  In the present embodiment, the substrate temperature change value ΔT is used to correct the temperature values (SUM1max, SUM2max, SUM3max, or SUM1o, SUM2o, SUM3o) to obtain initial values SUM1 (n-1), SUM2 (n -1) and SUM3 (n-1) are calculated, but the substrate temperature Tb is simply based on the substrate temperature Tb (substrate temperature at the start of assist control) without using the substrate temperature change value ΔT. The temperature values (SUM1max, SUM2max, SUM3max, or SUM1o, SUM2o, SUM3o) are corrected so that the initial values SUM1 (n-1), SUM2 (n-1), and SUM3 (n-1) decrease as the value of SUM decreases. It may be a configuration.

  Further, in the present embodiment, the temperature data abnormality is detected using the checksum. However, regarding the data abnormality detection, not only the checksum but various methods are known. You can use something.

  In this embodiment, the temperature data is stored in the EEPROM 44. However, the EEPROM 44 is not necessarily used, and may be stored in another nonvolatile memory. The electric motor is not limited to a brush motor but may be a brushless motor, or may be a three-phase motor without being limited to a single-phase motor.

  The electric power steering according to the present embodiment is a column assist type that applies a rotational force to the steering shaft 12 by the electric motor 15, but is applied to a rack assist type that applies an axial force to the rack bar 14 by the electric motor 15. May be.

  In this embodiment, the electric power steering device that assists the steering operation has been described. However, the present invention can also be applied to a steering-by-wire steering device in which the steering handle and the steered wheels are mechanically separated. That is, at least one of an electric motor that generates a steering reaction torque for a steering operation of the driver and an electric motor that generates a steering torque for steering the steered wheels is provided, and the temperature of at least one of the electric motors is adjusted. It may be estimated to prevent overheating by adding a current limit based on the estimated temperature.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus, 10 ... Steering mechanism, 11 ... Steering handle, 15 ... Electric motor, 21 ... Steering torque sensor, 22 ... Vehicle speed sensor, 23 ... Rotation angle sensor, 24 ... Current sensor, 25 ... Temperature sensor, 30 DESCRIPTION OF SYMBOLS ... Electronic control unit (ECU), 32 ... Motor drive circuit, 40 ... Electronic control circuit, 41 ... Microcomputer, 42 ... Input interface, 43 ... Output interface, 44 ... EEPROM, 50 ... Power supply, 51 ... Battery, 60 ... Ignition Switch, FW1, FW2 ... front left and right wheels (steering wheels), SUM1 ... current square integrated value for heat mass temperature estimation, SUM1max ... temporary heat mass temperature value, SUM1o ... heat mass temperature value, SUM2 ... current square integrated value for coil temperature estimation, SUM2max ... Temporary coil temperature value, SUM2o ... Coil temperature value, SUM3 ... Brush Current square integrated value for degree estimation, SUM3max ... temporary brush temperature value, SUM3o ... brush temperature value, Tb ... substrate temperature, Tbmax ... temporary substrate temperature, Tbo ... substrate temperature, Th ... steering torque, Tm ... motor estimated temperature, α, β, γ: correction coefficient, ΔT: substrate temperature change value.

Claims (5)

An electric motor that generates steering torque;
Temperature estimation means for estimating the temperature of the electric motor by sequential calculation;
Steering detection means for detecting the steering state of the steering wheel;
The target energization control amount of the electric motor is calculated based on the detected steering state of the steering wheel while applying a current limit based on the estimated temperature of the estimated electric motor, and the calculated target energization control amount Motor control means for driving and controlling the electric motor according to
Nonvolatile storage means for storing estimated temperature data relating to the estimated temperature of the electric motor;
The estimated temperature data related to the estimated temperature of the electric motor estimated by the temperature estimating means at the end of the drive control of the electric motor is written to the nonvolatile storage means, and the nonvolatile data is started at the next start of the drive control of the electric motor. An estimated temperature data read / write means for reading the estimated temperature data stored in the storage means,
In the steering apparatus that starts the calculation of the estimated temperature of the electric motor using the estimated temperature data read by the estimated temperature data read / write means at the start of driving control of the electric motor,
Related temperature measuring means for measuring the temperature of the portion where the temperature changes with the temperature change of the electric motor as the related temperature;
Data abnormality detection means for determining whether or not the data in the nonvolatile storage means is abnormal at the start of drive control of the electric motor;
The temporary estimated temperature initial value set in advance to a high temperature for overheating prevention is stored, and when the abnormality of the data in the nonvolatile storage means is detected, the related temperature measured by the related temperature measuring means is An abnormal-time corrected estimated temperature initial value calculating means for calculating a corrected estimated temperature initial value obtained by correcting and correcting the temporary estimated temperature initial value so as to decrease as the related temperature decreases,
The temperature estimating means detects the estimated temperature of the electric motor using the corrected estimated temperature initial value calculated by the abnormal correction estimated temperature initial value calculating means when an abnormality of data in the nonvolatile storage means is detected. A steering apparatus characterized by starting computation.   The abnormal correction estimated temperature initial value calculating means stores a temporary related temperature initial value set in advance to a high temperature for overheating prevention, and the temporary related temperature initial value and the related temperature measured by the related temperature measuring means. 2. The steering apparatus according to claim 1, wherein a corrected estimated initial temperature value corrected so that the temporary estimated initial temperature value decreases as the temperature difference increases is calculated based on a temperature difference with temperature. The related temperature data related to the related temperature measured by the related temperature measuring means at the end of the drive control of the electric motor is written into the nonvolatile storage means, and the nonvolatile storage means is started at the next start of the drive control of the electric motor. Related temperature data read / write means for reading related temperature data stored in
If no abnormality is detected in the data in the nonvolatile memory means at the start of driving control of the electric motor, the related temperature represented by the related temperature data read by the related temperature data read / write means and the related temperature measuring means Based on the temperature difference from the related temperature measured by the corrected temperature estimated by correcting the estimated temperature represented by the estimated temperature data read by the estimated temperature data read / write means so as to decrease as the temperature difference increases And a normal correction estimated temperature initial value calculating means for calculating an initial value,
The temperature estimating means uses the corrected estimated temperature initial value calculated by the normal correction estimated temperature initial value calculating means when the abnormality of the data in the nonvolatile storage means is not detected, and the estimated temperature of the electric motor The steering apparatus according to claim 1 or 2, characterized by starting the calculation. A temperature measurement abnormality detecting means for determining whether or not the related temperature measurement means is abnormal,
The normal correction estimated temperature initial value calculating means corrects the estimated temperature represented by the estimated temperature data read by the estimated temperature data read / write means when an abnormality of the related temperature measuring means is detected. 4. The steering apparatus according to claim 3, wherein the steering temperature is set as the estimated temperature initial value. A temperature measurement abnormality detecting means for determining whether or not the related temperature measurement means is abnormal,
The abnormality correction estimated temperature initial value calculating means sets the temporary estimated temperature initial value as the estimated temperature initial value without correcting when the abnormality of the related temperature measuring means is detected. The steering apparatus according to any one of claims 1 to 4.

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