JP2009190663A - Electric power-steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable electric power-steering device by efficiently conducting overheat protection depending on an estimated temperature of a motor and a total integrated time or a total count. <P>SOLUTION: In the electric power-steering device provided with a motor drive circuit for drive-controlling based on a current instruction value, a temperature estimation part for estimating an estimated temperature of the motor based on the temperature of the motor drive circuit and a motor current value and an overheat protection part for limiting the current instruction value by a current instruction limiting value calculated based on the estimated temperature, after the overheat protection part is operated, a function for limiting the current instruction value based on the total integrated time which is integration of time when the estimated temperature is equal to or higher than a temperature threshold value is arranged. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus that applies a steering assist force by a motor to a steering system of a vehicle, and more particularly to an electric power steering apparatus that efficiently protects a motor from excessive heat generation.

  An electric power steering device for energizing a vehicle steering device with an auxiliary load by the rotational force of a motor energizes an auxiliary load to a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a reduction gear. It is supposed to be. Such a conventional electric power steering apparatus performs feedback control of motor current in order to accurately generate assist torque (steering assist force). In the feedback control, the motor applied voltage is adjusted so that the difference between the current command value and the motor current detection value becomes small. Generally, the adjustment of the motor applied voltage is a duty of PWM (pulse width modulation) control. This is done by adjusting the tee ratio.

  Here, the general configuration of the electric power steering apparatus will be described with reference to FIG. 9. The column shaft 2 of the handle 1 is connected to the tie rod 6 of the steering wheel via the reduction gear 3, the universal joints 4 a and 4 b, and the pinion rack mechanism 5. It is connected to. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque of the handle 1, and a motor 20 that assists the steering force of the handle 1 is connected to the column shaft 2 via the reduction gear 3. A power is supplied from the battery 14 to the control unit 30 that controls the power steering device, and an ignition signal is input through the ignition key 11. The control unit 30 detects the steering torque Th and the vehicle speed detected by the torque sensor 10. The current command value I of the assist command is calculated based on the vehicle speed V detected by the sensor 12, and the current supplied to the motor 20 is controlled based on the calculated current command value I.

  The control unit 30 is mainly composed of a CPU (including MPU and MCU), and FIG. 10 shows general functions executed by a program inside the CPU.

  The function and operation of the control unit 30 will be described with reference to FIG. 10. The steering torque Th detected by the torque sensor 10 is input to the current command value calculation unit 32, and the vehicle speed V detected by the vehicle speed sensor 12 is also the current command. The value is input to the value calculation unit 32. The current command value calculation unit 32 refers to the assist map stored in the memory 33 based on the input steering torque Th and the vehicle speed V, and a current command value I that is a control target value of the current supplied to the motor 20. To decide. The current command value I is input to the subtraction unit 30a and also input to the feedforward differential compensation unit 34 for increasing the response speed, and the deviation (Ii) of the subtraction unit 30a is input to the proportional calculation unit 35. At the same time, it is input to the integral calculation unit 36 for improving the characteristics of the feedback system, and its proportional output is input to the addition unit 30b. The outputs of the differential compensator 34 and the integral compensator 36 are also added and input to the adder 30b, and the current control value E, which is the addition result of the adder 30b, is input to the motor drive circuit 37 as a motor drive signal. Electric power is supplied from the battery 14 to the motor drive circuit 37, the motor current value i of the motor 20 is detected by the motor current detection circuit 38, and the motor current value i is input to the subtraction unit 30a and fed back.

  In such an electric power steering apparatus, since the motor temperature rises due to the driving of the motor and the motor may be damaged or damaged when the motor is overheated, various types of overheat protection of the motor have been proposed.

  For example, the average value of the detected motor current value is obtained, and a large current is limited based on the average current, or when the average current is a predetermined value or more, the current is limited every predetermined time, The motor was overheat protected. However, since the outside air temperature was not taken into account, there was a problem that the estimated temperature and the actual temperature were different from each other, and the overheat protection was not sufficiently performed. In addition, the motor temperature was estimated based on the temperature of the radiator of the control unit and the motor current was limited based on the estimated temperature to protect the motor from overheating. Since the constants are different, there is a problem that accurate overheat protection cannot be performed.

As an apparatus for solving such a problem, for example, there is an electric power steering apparatus disclosed in Japanese Patent No. 3601967 (Patent Document 1), and the electric power steering apparatus disclosed in Patent Document 1 detects temperatures of a motor and a control unit. The motor and control unit are protected from overheating according to the detected temperature. That is, the temperature detection means provided in the motor drive circuit of the control unit and the control unit overheat protection that estimates the motor drive element temperature based on the temperature obtained by the temperature detection means and limits the current control value by the estimated temperature And the temperature from the temperature detection means at the time of start-up is used as a reference value for the motor brush temperature, the reference value and the estimated temperature value from the motor brush temperature estimation means are added and corrected, and the current is obtained by the corrected estimated motor brush temperature value. Motor overheat protection means for limiting the control value, and the temperature from the temperature detection means at the time of start-up as the reference value of the motor magnetic body temperature, correct by adding the reference value and the temperature estimation value from the motor magnetic body temperature estimation means, Motor low-temperature demagnetization protection means that limits the current control value based on the corrected motor magnetic body temperature estimated value, and the control unit overheats Current control value output from the protection means, current limit value output from the motor overheat protection means, or current limit value output from the motor low-temperature demagnetization protection means, so that the current control value is limited by the greater limit I have to.
Japanese Patent No. 3601967

  However, in the apparatus of Patent Document 1, the current command value is limited when the detected temperature exceeds the threshold value, but the limit is canceled when the temperature returns to within the threshold value range, so that the time elapses. At the same time, there is a problem that the amount of heat stored in the motor increases. In other words, if the amount of heat stored in the motor increases, the limitation and release (recovery) due to overheat protection will be repeated, the error in the estimated motor temperature will increase, and the temperature inside the motor may exceed the limit level depending on the situation There is sex. Moreover, when the threshold value is set low in consideration of the heat storage amount of the motor, the overheat protection is performed excessively, so that the efficiency is deteriorated and the original performance of the motor cannot be exhibited.

  FIG. 11 is a characteristic example for explaining the conventional overheat protection control. When the estimated temperature of the motor reaches 160 ° C. or more at the point P10, the overheat protection control function is activated and the current command value (steering assist command value) is It has come to be restricted. The current command value is limited by the overheat protection control function, the estimated temperature drops to 140 ° C. at point P11, the overheat protection control function is canceled, and the normal control is restored. When the estimated temperature again exceeds 160 ° C. at point P10, the overheat protection control function is activated and the current command value is limited.

  In this way, by repeating the current limitation and recovery by overheat protection many times, the amount of heat stored in the motor increases with time, so the temperature inside the motor reaches the limit level (160 ° C. in the example of FIG. 11). There is a problem that will be exceeded.

  The present invention has been made under the circumstances as described above, and an object of the present invention is to demonstrate the original performance of the motor by efficiently performing overheat protection according to the estimated temperature of the motor and the total accumulated time or the total number of counts. It is possible to provide a more reliable electric power steering device.

  The present invention includes a motor drive circuit that controls the motor based on a current command value, a temperature estimation unit that estimates an estimated temperature of the motor based on the temperature and motor current value of the motor drive circuit, and the estimated temperature. An electric power steering apparatus including an overheat protection unit that limits the current command value by a current command limit value that is calculated based on the above, and the object of the present invention is that the estimated temperature is a temperature after the overheat protection unit is activated. This is achieved by providing a function for limiting the current command value based on the total accumulated time obtained by integrating the time exceeding the threshold.

  The present invention includes a motor drive circuit that controls the motor based on a current command value, a temperature estimation unit that estimates an estimated temperature of the motor based on the temperature and motor current value of the motor drive circuit, and the estimated temperature. With respect to the electric power steering apparatus including the overheat protection unit that limits the current command value by the current command limit value calculated based on the above, the object of the present invention is to provide the estimated temperature after the overheat protection unit is activated. Is achieved by providing a function of limiting the current command value based on the total number of counts obtained by counting the number of times that the temperature becomes equal to or higher than the temperature threshold.

  The present invention includes a motor drive circuit that controls the motor based on a current command value, a temperature estimation unit that estimates an estimated temperature of the motor based on the temperature and motor current value of the motor drive circuit, and the estimated temperature. With respect to the electric power steering apparatus provided with an overheat protection unit that limits the current command value by a current command limit value calculated based on the above, the above object of the present invention is based on the estimated temperature from the overheat protection unit. This is achieved by switching between a current command limit value and a preset fixed value and providing a protection determination unit that limits the current command value.

  Further, the object of the present invention is to switch the protection determination unit by comparing the estimated temperature with the temperature threshold and comparing a total accumulated time of the estimated temperature exceeding the temperature threshold with a set time. A determination unit that outputs a signal, and a switching unit that switches between the current command limit value and the fixed value according to the switching signal, or the protection determination unit converts the estimated temperature to the temperature A determination unit that compares a threshold value, compares the number of times the estimated temperature is equal to or higher than the temperature threshold value with a set number of times, and outputs a switching signal; and the current command limit value and the fixed value according to the switching signal. The switching unit that performs switching, or the determination unit effectively compares the temperature threshold value with the estimated temperature based on the presence or absence of an overheat protection flag of the temperature estimation unit. It is made.

  The present invention includes a motor drive circuit that controls the motor based on a current command value, a temperature estimation unit that estimates an estimated temperature of the motor based on the temperature and motor current value of the motor drive circuit, and the estimated temperature. With respect to the electric power steering apparatus including the overheat protection unit that limits the current command value by the current command limit value calculated based on the above, the above object of the present invention is input to the overheat protection unit according to the estimated temperature This is achieved by providing a protection determination unit that changes the estimated temperature gain to be input to the overheat protection unit and limits the current command value.

  Further, the object of the present invention is to provide the protection determination unit that compares the estimated temperature with the temperature threshold value and changes the total accumulated time of the estimated temperature exceeding the temperature threshold value with a set time. The determination unit that outputs a signal and the gain unit that changes the estimated temperature gain according to the change signal, or the protection determination unit compares the estimated temperature with the temperature threshold value. A determination unit that outputs a change signal by comparing the number of times that the estimated temperature is equal to or higher than the temperature threshold with a set number of times, and a gain unit that changes the estimated temperature gain according to the change signal. Alternatively, the determination unit is effectively achieved by comparing the temperature threshold and the estimated temperature based on the presence or absence of an overheat protection flag of the temperature estimation unit.

  According to the electric power steering device of the present invention, even when the conventional heating protection control function is implemented, the current command limit value is switched by switching the current command limit value according to the estimated motor temperature and the total accumulated time. By limiting the maximum current, the current command value can be limited more finely. Further, by changing the estimated temperature gain of the estimated motor temperature based on the estimated motor temperature and the total count, the current command value can be more finely limited using the conventional heating protection control function.

  As described above, by efficiently performing overheat protection by limiting the current appropriately according to the temperature condition of the motor, it is possible to prevent a heavy burden on the motor and to realize a more reliable electric power steering device. be able to.

  The electric power steering apparatus according to the present invention includes a protection determination unit that limits the current command value according to the estimated temperature of the motor and the total accumulated time or the total count even when the conventional overheat protection control is performed. Can be realized. Change the current command limit value according to the estimated motor temperature and total accumulated time to limit the maximum current of the current command value, or change the estimated temperature gain according to the estimated motor temperature and the total count, and change the estimated temperature gain The current command value is limited by the current command limit value based on.

  First, an example of a configuration having a motor overheat protection function which is a premise of the present invention will be described with reference to FIG. FIG. 1 is shown corresponding to FIG. 10 described above, and the same members are denoted by the same reference numerals and description thereof is omitted.

The temperature detection means 41 of the motor drive circuit 37 is composed of a temperature detection element such as a thermistor, for example, and is attached to a printed circuit board on which a radiator and FET of the motor drive circuit 37 are mounted so that the actual temperature T can be detected. . The temperature T detected by the temperature detection means 41 is input to the temperature estimation unit 43. The temperature estimation unit 43 estimates the heat generation amount of the motor 20 as the estimated temperature Tp based on the detected temperature T and the motor current value i detected by the motor current detection circuit 38. A set temperature T ₀ (for example, 160 ° C.) is input to the temperature estimation unit 43 as a threshold value. When the estimated temperature Tp becomes equal to or higher than the set temperature T ₀ , the temperature estimation unit 43 performs overheating that can be read by the overheat protection unit 42. While setting the protection flag, the estimated temperature Tp is input to the overheat protection unit 42. When the overheat protection unit 42 reads the overheat protection flag set in the temperature estimation unit 43, the overheat protection unit 42 calculates the current command limit value Ia based on the input estimated temperature Tp and inputs it to the current command value calculation unit 32. The current command value calculation unit 32 obtains a limited current command value I based on the input current command limit value Ia.

On the other hand, when the estimated temperature Tp is lower than the set temperature T ₀ , the temperature estimating unit 43 does not set the overheat protection flag, and resets (clears) when the overheat protection flag is set. Accordingly, since the overheat protection unit 42 cannot recognize the overheat protection flag, the current command limit value Ia of “0” is input to the current command value calculation unit 32 so as to perform normal control. The current command value calculation unit 32 obtains the current command value I based on the steering torque Th and the vehicle speed V as described above, and performs normal assist control.

  Next, the configuration of the present invention having the overheat protection control function as described above will be described below with reference to FIG. FIG. 2 shows a configuration example of the present invention corresponding to FIG. 1, and the same members are denoted by the same reference numerals and the description thereof is omitted.

The present invention is provided with a protection determination unit 50 between the overheat protection portion 42 and the current command value calculating section 32, the protection determination unit 50, together with the estimated temperature Tp is compared with the temperature threshold value T _1, the total accumulated time TA Is compared with the set time ts and outputs a determination signal CS, a constant unit 52 holding an arbitrary fixed value d, and contacts C1 and C2, and the contacts C1 and C2 are determined by the determination signal CS. And a switching unit 53 that can be switched.

The temperature estimation unit 43 sets an overheat protection flag for starting the overheat protection control when the estimated temperature Tp becomes equal to or higher than the set temperature T ₀ so that the overheat protection unit 42 and the determination unit 51 can read the estimated temperature Tp. Tp is input to the overheat protection unit 42 and the determination unit 51. The overheat protection unit 42 that has read the overheat protection flag inputs the current command limit value Ia calculated based on the input estimated temperature Tp to the contact C <b> 1 of the switching unit 53. The determination unit 51 is preset with a temperature threshold T ₁ (T ₁ <T ₀ ) and a set time ts. When the overheat protection flag from the temperature estimation unit 43 is read, the input estimated temperature Tp with comparing the temperature thresholds T _1, the time that is the temperature thresholds T ₁ or integrated with integrating counter, to calculate the total accumulated time TA. The determination unit 51 only when the thermal protection unit 42 is operating, accumulates the time the estimated temperature Tp is a temperature threshold value above T _1. Then, the total accumulated time TA is compared with the set time ts, and when the total accumulated time TA becomes equal to or greater than the set time ts, a determination signal CS for switching the contact C1 and the contact C2 of the switching unit 53 is output. The fixed value d preset in the constant unit 52 is a limit value that limits the maximum current of the current command value I, and is input to the contact C2 of the switching unit 53. Based on the determination signal CS from the determination unit 51, the switching unit 53 switches the current command limit value Ia input to the contact C1 and the fixed value d input to the contact C2 to calculate a current command value. Input to the unit 32. Also, so as to reset is set temperature threshold value _{T 2 (T 2 <T 1} ) is a an overheat protection flag estimated temperature Tp is lower than the temperature threshold value T ₂ are the temperature estimating unit 43. When the overheat protection flag is cleared, the integration counter is also cleared.

In the above description, the overheat protection flag for starting overheat protection control is set in the temperature estimation unit 43 so that the overheat protection unit 42 and the determination unit 51 can read the overheat protection flag. You may make it set to the part 51. FIG. When setting the overheat protection flag overheat protection portion 42 and the determination unit 51 resets the overheat protection flag by outputting a reset signal when the estimated temperature Tp is equal to or less than the temperature threshold value T _2.

FIG. 3 shows a state in which the overheat protection unit 42 and the protection diagnosis unit 50 that have read the overheat protection flag limit the current command value I based on the estimated temperature Tp, and the estimated temperature Tp is equal to or higher than the set temperature T _0. The overheat protection control is activated at time t1, and the current command value I is limited by the overheat protection unit 42 and the protection diagnosis unit 50, and the estimated temperature Tp is lowered.

Here, in the present invention, the temperature threshold T ₁ is set lower than the set temperature T ₀ , and the determination unit 51 integrates the time when the estimated temperature Tp is equal to or higher than the temperature threshold T _1, and overheat protection is performed according to the total integrated time TA. Take control. Estimated temperature Tp becomes the set temperature _{T 0} or at time t1 in the example of FIG. 3, subsequent overheat protection control is activated, at time t2 becomes the temperature thresholds _{T 1} or less, then the time t3-t4 = TS1, the time t5- the temperature thresholds _{T 1} or more t6 = TS2. Such estimated temperature Tp is integrating the time TS1 and TS2 as the temperature thresholds _{T 1} or more, when the total accumulated time TA (= TS1 + TS2) is equal to or larger than the set time ts, to further limit the current command value I To provide better overheat protection. This is the principle of the present invention.

On the other hand, FIG. 4 is a characteristic diagram for explaining the operation example of FIG. 2, and a temperature threshold T ₂ is preset in the temperature estimation unit 43. Estimated temperature Tp is set to overheat protection flag time t10 as the set temperature T ₀ or more, the overheat protection control functions by I read the overheat protection flag overheat protection portion 42 and the protection determination unit 50 is operated. In this case, the switching unit 53 is connected to the contact C1, and the current command limit value Ia calculated by the overheat protection unit 42 is output via the contact C1 of the switching unit 53, and the current command value calculation is performed as the current command limit value Ib. Input to the unit 32. Thereafter, integrated similarly estimated temperature Tp in the case of FIG. 3 is time t11-t12 = TS10 as a temperature threshold value above _{T 1,} time t13-t14 = TS11, time t15-t16 = TS12, the time point t17-t18 = TS13 The total accumulated time TA (= TS10 + TS11 + TS12 + TS13) is compared with the set time ts. When the total accumulated time TA becomes equal to or greater than the set time ts, the contact of the switching unit 53 is changed from “C1” to “C2” by the determination signal CS. The fixed value d from the switching and constant part 52 is output to limit the current command value I. Further, the estimated temperature Tp is decreased, the time t19 to equal to or less than a temperature threshold value T _2, and resets the overheat protection flag.

  In such a configuration, an example of the operation will be described with reference to the flowchart of FIG.

  The driver turns on the ignition signal from the ignition key (step S10), inputs the steering torque Th from the torque sensor 10 (step S11), and inputs the vehicle speed V from the vehicle speed sensor 12 (step S12). Note that the input order of the steering torque Th and the vehicle speed V is arbitrary. The current command value calculation unit 32 calculates a current command value I based on the steering torque Th and the vehicle speed V (step S13), and the motor 20 is driven and controlled by the current command value I.

Comparing the temperature estimation unit 43, based on the motor current value i from the temperature T and the motor current detecting circuit 38 from the temperature detecting means 41 estimates the estimated temperature Tp (step S14), and the estimated temperature Tp and the set temperature T ₀ Thus, it is determined whether or not overheat protection control is necessary (step S15). When the estimated temperature Tp is lower than the set temperature T ₀ and overheat protection is not necessary, the current command limit value Ia is set to “0”, and the current command limit value Ib of “0” is set via the contact C1 of the switching unit 53. Is input to the current command value calculation unit 32 to perform normal control (step S16). If the ignition signal is not OFF, the process returns to step S11 and the above operation is repeated.

  On the other hand, when it is determined in step S15 that the overheat protection control is necessary, an overheat protection flag is set, and the estimated temperature Tp is input to the overheat protection unit 42 and the determination unit 51, and the overheat protection unit 42 is input. Based on the estimated temperature Tp, the current command limit value Ia is calculated, and the current command limit value Ib is input to the current command value calculation unit 32 via the contact C1 of the switching unit 53 to perform overheat protection control (step S20). .

Determining unit 51, the estimated temperature Tp is equal to or the temperature thresholds _{T 1} or more (step S21), and if the estimated temperature Tp is the temperature thresholds _{T 1} or more, the estimated temperature Tp is the temperature thresholds _{T 1} or more and is the total accumulated time TA of time until below the temperature thresholds T ₁ calculated as described in FIG. 3 or FIG. 4 (step S22), and whether or not the total accumulated time TA is set time ts or Is determined (step S23). If the total accumulated time TA is smaller than the set time ts, the process returns to step S20. If the total accumulated time TA is equal to or longer than the set time ts, the switching signal CS for switching the contact of the switching unit 53 from “C1” to “C2”. And the current command value I is limited by the current command limit value Ib based on the fixed value d preset in the constant unit 52 (step S24). Then, by comparing the estimated temperature Tp and the temperature threshold value _{T 2} (step S25), and if the estimated temperature Tp is greater than the temperature threshold value _{T 2} is returned to the above step S24, overheating if the estimated temperature Tp is the temperature threshold _{T 2} or less The protection flag is reset (step S26), and normal control is performed.

On the other hand, if the estimated temperature Tp is the temperature thresholds _{T 1} is smaller than in the step S21, the estimated temperature Tp is equal to or the temperature threshold value _{T 2} or less (step S27), the estimated temperature Tp is the temperature threshold value _{T 2} or less reset the overheat protection flag if (step S26), the estimated temperature Tp is greater than the temperature threshold value _{T 2} are returns to the step S20.

  FIG. 6 shows another configuration example of the present invention corresponding to FIG. 2, and the same members are denoted by the same reference numerals and the description thereof is omitted.

And a protective determination unit 60 between the thermal protection unit 42 and the temperature estimating unit 43 in this embodiment, the protection determination unit 60, the estimated temperature Tp while compared with the temperature thresholds T _1, the temperature thresholds T ₁ exceeds The determination unit 61 that compares the total count number cta with the set number ct and outputs the change signal GS, changes the gain of the estimated temperature Tp based on the input change signal GS, and sets the gain-changed estimated temperature Tpg. And a gain unit 62 for outputting.

Temperature estimation unit 43, the overheat protection flag for estimated temperature Tp starts overheat protection control is the set temperature T ₀ or more, with overheat protection unit 42 and the judging unit 61 is set readable, respectively, the estimated temperature Tp is input to the gain unit 62 and the determination unit 61. The overheat protection unit 42 that has read the overheat protection flag inputs the current command limit value Ic calculated based on the estimated temperature Tpg from the gain unit 62 to the current command value calculation unit 32. The determination unit 61 is preset with a temperature threshold T ₁ (T ₁ <T ₀ ) and a set count number ct. When the overheat protection flag from the temperature estimation unit 43 is read, the input estimated temperature Tp and with comparing the temperature thresholds T _1, the number of times that a temperature threshold value above T ₁ is counted up by using the integrating counter, to calculate the total number of counts cta. The determination unit 61 only when the thermal protection unit 42 is operating, the estimated temperature Tp counts up the number of times a temperature threshold value above T _1. Then, the total count number cta is compared with the set number ct, and when the total count number cta becomes equal to or greater than the set number ct, a change signal GS for changing the characteristics of the gain unit 62 is output. The gain unit 62 changes the gain of the estimated temperature Tp based on the input change signal GS, and inputs the estimated temperature Tpg whose gain has been changed to the overheat protection unit 42. The overheat protection unit 42 calculates a current command limit value Ic based on the estimated temperature Tpg, and limits the current command value I by the current command limit value Ic. Since the estimated temperature gain is not changed during normal assist control or conventional overheat protection control in which the change signal GS is not input, the estimated temperature Tp is output as it is as the estimated temperature Tpg.

  FIG. 7 shows how the overheat protection unit 42 and the protection determination unit 60 that have read the overheat protection flag limit the current command value I based on the estimated temperature Tp.

In this example, the temperature estimation unit 43 and the temperature threshold value T ₀ and T ₂ is set in advance, and sets the overheat protection flag at t20 the estimated temperature Tp reaches the set temperature T ₀ or more, reading the overheat protection flag The overheat protection control function is activated by the protection determination unit 60 and the overheat protection unit 42. Thereafter, the determination unit 61 indicates how the time t21 the temperature thresholds _{T 1} or more, the time t22, counts up the time t23 in integrating counter, the total number of counts cta is turned three times. The determination unit 61 is preset with a set number of times ct (for example, 3 times). The total count number of times cta is compared with the set number of times ct. When the total count number of times cta becomes equal to or greater than the set number of times ct, the change signal GS is output and the gain of the gain unit 62 is increased. Then, the estimated temperature Tp is to increase the gain up time t25 serving as a temperature threshold value T ₂ or less, and resets the overheat protection flag at time t25. That is, when the total number of counts cta becomes the set number of times ct, the determination unit 61 inputs an estimated temperature Tpg higher than normal to the overheat protection unit 42 and significantly limits the current command value I to provide appropriate overheat protection. Do.

In this example as well, the overheat protection flag for starting overheat protection control is set in the temperature estimation unit 43 so that the overheat protection unit 42 and the determination unit 61 can read each other. And you may make it set to the determination part 61. FIG. When setting the overheat protection flag overheat protection portion 42 and the determination unit 61 resets the overheat protection flag by outputting a reset signal when the estimated temperature Tp is equal to or less than the temperature threshold value T _2.

  In such a configuration, an example of the operation will be described with reference to the flowchart of FIG.

  The driver turns on the ignition signal from the ignition key (step S30), inputs the steering torque Th from the torque sensor 10 (step S31), and inputs the vehicle speed V from the vehicle speed sensor 12 (step S32). Note that the input order of the steering torque Th and the vehicle speed V is arbitrary. The current command value calculation unit 32 calculates a current command value I based on the steering torque Th and the vehicle speed V (step S33), and the motor 20 is driven and controlled by the current command value I.

The temperature estimation unit 43 estimates the estimated temperature Tp based on the temperature T from the temperature detection unit 41 and the motor current value i from the motor current detection circuit 38 (step S34), and the estimated temperature Tp is input to the gain unit 62. input. Then, it is determined whether or not it is necessary to overheat protection control by comparing the estimated temperature Tp and the set temperature T ₀ (step S35). Then, the estimated temperature Tp is lower than the set temperature T _0, when there is no need for thermal protection, the gain unit 62 is input to the current command value calculating section 32 estimates the temperature Tp of the temperature estimation unit 43 as it is as the estimated temperature Tpg Then, normal control is performed (step S36). If the ignition signal is not OFF, the process returns to step S31 and the above operation is repeated.

  On the other hand, when it is determined in step S35 that the overheat protection control is necessary, an overheat protection flag is set, and the estimated temperature Tp is input to the determination unit 61. The overheat protection unit 42 is input from the gain unit 62. A current command limit value Ic is calculated based on the estimated temperature Tp, and the current command limit value Ic is input to the current command value calculation unit 32 to perform overheat protection control (step S40).

Determining unit 61, the estimated temperature Tp is equal to or the temperature thresholds _{T 1} or more (step S41), if the estimated temperature Tp is the temperature thresholds _{T 1} or more, the estimated temperature Tp is the temperature thresholds _{T 1} or more and The counted number is counted up as described with reference to FIG. 7 (step S42), and it is determined whether the counted up total count number cta is equal to or greater than the set number ct (step S43). If the total count number cta is smaller than the set number ct, the process returns to step S40. If the total count number cta is equal to or greater than the set number ct, an estimated temperature Tpg higher than normal is input to the overheat protection unit 42 and a current command is issued. In order to greatly limit the value I, the change signal GS is output to increase the gain of the gain unit 62 (step S44). Then, by comparing the estimated temperature Tp and the temperature threshold value _{T 2} (step S45), if the estimated temperature Tp is greater than the temperature threshold value _{T 2} is returned to the above step S44, overheating if the estimated temperature Tp is the temperature threshold _{T 2} or less The protection flag is reset (step S46), and normal control is performed.

On the other hand, if the estimated temperature Tp is the temperature thresholds _{T 1} is smaller than in the step S41, the estimated temperature Tp is equal to or the temperature threshold value _{T 2} or less (step S47), the estimated temperature Tp is the temperature threshold value _{T 2} or less reset the overheat protection flag if (step S46), the estimated temperature Tp is greater than the temperature threshold value _{T 2} are returns to the step S40.

  In the above description, the total accumulated time TA and the set time ts are compared to limit the maximum current of the current command value I using the fixed value d, and the total count number cta and the set number ct are compared. Although the example in which the estimated temperature gain of the estimated temperature Tp is changed and the current command value I is limited by the overheat protection unit 42 has been described, the estimated temperature gain of the estimated temperature Tp is compared by comparing the total accumulated time TA and the set time ts. The current command value I may be limited by the overheat protection unit 42, or the maximum current of the current command value I may be limited using the fixed value d by comparing the total count number cta with the set number ct. Anyway. The change of the estimated temperature gain may be an analog change.

  In addition, the present invention specifies a part that needs to be overheat protected and adds to the overheat protection function as shown in Japanese Patent No. 3601967 (Patent Document 1) that performs overheat protection depending on the situation. It may be applied. That is, the protection determination unit described in the present invention is provided, the temperature estimation unit estimates the junction temperature of the FET, the motor brush temperature, and the motor magnetic body temperature, and the overheat protection unit includes the junction temperature of the FET, the motor. The control unit overheat protection, motor overheat protection, and motor low temperature demagnetization protection may be switched based on the estimated values of the brush temperature and the motor magnetic body temperature.

It is a block diagram which shows an example of the electric power steering apparatus which comprised the overheat protection part used as the premise of this invention. It is a block diagram which shows the structural example of the electric power steering apparatus which concerns on this invention. It is a characteristic view for demonstrating the operation example of this invention. It is a characteristic view for explaining the example of operation of the present invention in detail. It is a flowchart which shows the operation example of this invention. It is a block diagram which shows the structural example of another electric power steering apparatus which concerns on this invention. It is a characteristic view for demonstrating the operation example of this invention. It is a flowchart which shows an operation example in this invention. It is a figure which shows the structural example of the conventional electric power steering apparatus. It is a block diagram which shows the structural example of the conventional control unit. It is a figure for demonstrating control of overheat protection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Torque sensor 11 Ignition key 12 Vehicle speed sensor 20 Motor 32 Current command value calculating part 37 Motor drive part 41 Temperature detection means 42 Overheating protection part 43 Temperature estimation part 50, 60 Protection determination part 51, 61 Determination part 52 Constant part 53 Switching part 62 Gain section

Claims (10)

A motor drive circuit that controls the motor based on a current command value, a temperature estimation unit that estimates an estimated temperature of the motor based on the temperature of the motor drive circuit and a motor current value, and a calculation based on the estimated temperature In an electric power steering apparatus including an overheat protection unit that limits the current command value by a current command limit value, a total integration in which a time during which the estimated temperature is equal to or higher than a temperature threshold after the overheat protection unit is activated An electric power steering apparatus comprising a function of limiting the current command value based on time. A motor drive circuit that controls the motor based on a current command value, a temperature estimation unit that estimates an estimated temperature of the motor based on the temperature of the motor drive circuit and a motor current value, and a calculation based on the estimated temperature In an electric power steering apparatus comprising an overheat protection unit that limits the current command value by a current command limit value, a total count obtained by counting the number of times that the estimated temperature is equal to or higher than a temperature threshold after the overheat protection unit is activated An electric power steering apparatus having a function of limiting the current command value based on the number of times. A motor drive circuit that controls the motor based on a current command value, a temperature estimation unit that estimates an estimated temperature of the motor based on the temperature of the motor drive circuit and a motor current value, and a calculation based on the estimated temperature An electric power steering apparatus including an overheat protection unit that limits the current command value by a current command limit value, and a current command limit value from the overheat protection unit according to the estimated temperature and a preset fixed value, An electric power steering device characterized in that a protection determination unit is provided for switching the current command value to limit the current command value. The protection determination unit compares the estimated temperature with the temperature threshold value, compares a total integrated time of times when the estimated temperature is equal to or higher than the temperature threshold value with a set time, and outputs a switching signal; The electric power steering apparatus according to claim 3, comprising a switching unit that switches between the current command limit value and the fixed value in accordance with a switching signal. The protection determination unit compares the estimated temperature with the temperature threshold, compares the number of times that the estimated temperature is equal to or higher than the temperature threshold with a set number of times, and outputs a switching signal according to the switching signal. The electric power steering apparatus according to claim 3, further comprising a switching unit that switches between the current command limit value and the fixed value. The electric power steering apparatus according to claim 4 or 5, wherein the determination unit compares the temperature threshold with the estimated temperature based on the presence or absence of an overheat protection flag of the temperature estimation unit. A motor drive circuit that controls the motor based on a current command value, a temperature estimation unit that estimates an estimated temperature of the motor based on the temperature of the motor drive circuit and a motor current value, and a calculation based on the estimated temperature And an overheat protection unit that limits the current command value by a current command limit value that changes the estimated temperature gain that is input to the overheat protection unit according to the estimated temperature. An electric power steering apparatus comprising a protection determination unit that inputs to a protection unit and limits the current command value. The protection determination unit compares the estimated temperature with the temperature threshold value, compares a total integrated time of times when the estimated temperature is equal to or higher than the temperature threshold value with a set time, and outputs a change signal; The electric power steering apparatus according to claim 7, further comprising a gain unit that changes the estimated temperature gain in accordance with a change signal. The protection determination unit compares the estimated temperature with the temperature threshold value, compares the number of times the estimated temperature is equal to or higher than the temperature threshold value with a set number of times, and outputs a change signal according to the change signal. The electric power steering apparatus according to claim 7, further comprising: a gain unit that changes the estimated temperature gain. The electric power steering apparatus according to claim 8 or 9, wherein the determination unit compares the temperature threshold with the estimated temperature based on the presence or absence of an overheat protection flag of the temperature estimation unit.

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