JP3409756B2 - Electric power steering device for vehicles - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus for a vehicle equipped with an electric motor for giving an assisting force to a turning operation of a steering wheel, and more particularly to an electric motor and electric control which generate heat by electric current. The present invention relates to an electric power steering apparatus including a temperature detection unit that detects the temperature of a portion that generates heat in order to protect a circuit.

[0002]

2. Description of the Related Art An electric power steering apparatus of this type detects the temperature of an electric motor by a temperature detecting means such as a thermistor, as disclosed in Japanese Patent Laid-Open No. 7-112666, and the temperature detecting means is used. The electric current of the electric motor is limited based on the detected temperature.

[0003]

However, in the above-mentioned conventional technique, since the abnormality of the temperature detecting means is not detected, an appropriate current limitation cannot be made when the temperature detecting means becomes abnormal. There is. In this case, since the temperature detecting means is generally configured to detect the temperature within the predetermined temperature range, it is determined that the temperature is abnormal when the detected temperature is not within the predetermined temperature range. It can also be configured. However, when the temperature detecting means is in an abnormal state in which the temperature does not change while indicating the temperature within the predetermined temperature range, there is a problem that the abnormality cannot be detected by such a method.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to address the above-mentioned problems, and is characterized in that a current corresponding to a driving state of a vehicle is applied to generate an assisting force for a turning operation of a steering wheel. In an electric power steering apparatus for a vehicle equipped with an electric motor, temperature detecting means for detecting a temperature of a portion that generates heat by the electric current, and estimation of the portion that generates heat that is obtained based on a current value of a current passed through the electric motor. Temperature condition determination means for determining whether or not the value according to the temperature has changed by a predetermined value or more, and the temperature detection when it is determined that the value according to the estimated temperature of the heat generating portion has changed by the predetermined value or more. It is provided with abnormality determining means for determining that the temperature detecting means is abnormal when the temperature detected by the means has not changed by a predetermined temperature or more.

According to this, first, it is determined whether or not the value corresponding to the estimated temperature of the heat generating portion, which is obtained based on the current value of the current passed through the electric motor, has changed by a predetermined value or more. And when this temperature condition is satisfied,
When the temperature detected by the temperature detecting means has not changed by a predetermined temperature or more, it is determined that the temperature detecting means is abnormal. Therefore, it is possible to reliably detect that the temperature detected by the temperature detecting means has not changed, and in such a case, determine that the temperature detecting means is abnormal. The above-mentioned heat generating portion is substantially synonymous with the portion where the temperature changes due to the current passed through the electric motor.

In this case, the temperature condition judging means integrates the value corresponding to the current value of the electric motor as time passes, and based on the integrated value, the value corresponding to the estimated temperature of the heat generating portion is calculated. It is preferable that the configuration according to the current value of the electric motor is
In addition to the value of the same current value itself, the value obtained by squaring the same current value,
Alternatively, a value obtained by raising the same current value to the third power may be selected.

According to this, since the integrated value obtained by integrating the value corresponding to the electric current value of the electric motor with the passage of time has a strong correlation with the temperature of the heat generating portion, the temperature for judging the abnormality of the temperature detecting means. It is possible to accurately determine whether or not the condition is satisfied.

Further, in this case, the abnormality determining means detects a temperature equal to or lower than a predetermined high temperature equal to or lower than the maximum temperature which the temperature detecting means can detect, or the same. It is preferable that the temperature detection means is configured to make an abnormality determination when a temperature that is equal to or higher than a minimum low temperature that can be detected by the temperature detection means is detected.

In general, since the temperature detecting means has a non-linear output characteristic with respect to a temperature change, the temperature detecting means is designed and adjusted so that the output characteristic in the temperature region which needs to be detected with high accuracy is as linear as possible. Therefore, above a predetermined high temperature or below a predetermined low temperature, the temperature detection means can detect the temperature, but the output change with respect to the actual temperature change is small, and the abnormality detection of the temperature detection means can be performed in such an area. If it is done, there is a risk of causing a false determination. Therefore, as described above, if it is determined that the temperature detecting means is abnormal when the temperature lower than or equal to the predetermined high temperature is detected or the temperature lower than or equal to the predetermined low temperature is detected, it is erroneous. It is possible to reduce the possibility of determination.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram schematically showing an electric power steering apparatus according to the present invention. , An electric control unit including the electric control circuit 10 and a drive circuit 20 connected to the electric control circuit 10 (hereinafter referred to as “E”).
CU ". ) 25 and a DC electric motor 30 whose energization is controlled by the drive circuit 20.

The electric motor 30 applies an assist force to the steering of the front wheels by the turning operation of the steering wheel (steering wheel) 31, and is attached to the steering shaft 33 via the reduction mechanism 32 so that torque can be transmitted. The rack bar 34 is driven in the axial direction according to the rotation, and the front wheels connected to the rack bar 34 via tie rods are steered. A steering torque sensor 3 is attached to the steering shaft 33.
5, the steering torque sensor 35 detects a steering torque TM acting on the steering shaft 33 and outputs a steering torque signal representing the torque.

Next, the details of the electric circuit of the electric power steering apparatus shown in FIG. 1 will be described with reference to FIG. 2. The electric control circuit 10 includes a microcomputer (CPU) 11, an input interface 12, and an output. Interface 13 and EEPROM 14 (Electric
al Erasable PROM) and CPU 11
Includes a memory 11a that stores a program, a map, and the like described later.

The input interface 12 is connected to the CPU 11 via a bus, and has the steering torque sensor 35, the vehicle speed sensor 41 for detecting the vehicle speed V, the engine speed sensor 42 for detecting the engine speed NE, and the engine speed sensor 42.
Also, the driving circuit 20 is connected to a substrate temperature sensor 23 for detecting the temperature TMPBORD of the printed circuit board, which is disposed on the printed circuit board, and supplies a detection signal of each sensor to the CPU 11.

The substrate temperature sensor 23 is a thermistor composed of an oxide of a transition metal or the like, the electric resistance value of which changes with temperature, and its output characteristic is as shown in FIG. Is non-linear. The substrate temperature sensor 23 can detect the temperature at approximately −50 to 250 ° C., but within the temperature range of −20 to 160 ° C. that the drive circuit 20 can take in a normal state, the resistance value change per unit temperature. Is adjusted to be large. The CPU 11 detects the electric resistance value of the board temperature sensor 23 to detect the temperature TMPBORD of the printed board.
To get.

The output interface 13 is connected to the CPU 11 via the bus, and is also connected to the drive circuit 20 and the normally-open type relay 21. It sends a signal to change the state. The EEPROM 14 is a storage unit that stores and holds data even when the power is not supplied from the vehicle battery 50. The EEPROM 14 is connected to the CPU 11 via the bus and holds the data supplied from the CPU 11. At the same time, the data held therein is supplied to the CPU 11 in response to a request from the CPU 11.

The drive circuit 20 includes four switching elements Tr1 to Tr4 each having a MOSFET whose gate is connected to the output interface 13, two resistors 20a and 20b, and the substrate temperature sensor 23 described above. . One end of the resistor 20a is connected to the downstream side terminal of the relay 21 whose upstream side terminal is connected to the power supply line L of the battery 50 mounted in the vehicle, and the resistor 20a is connected to the downstream side terminal.
The other end of a 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.
The drain of No. 4 is grounded through the resistor 20b. Further, between the switching elements Tr1 and Tr3 is connected to one side of the electric motor 30, and the switching elements Tr2 and T3 are connected.
Between r4 and the other side of the electric motor 30 is connected.
It should be noted that both ends of the electric motor 30 and between the resistor 20b and the switching elements Tr3, Tr4 are connected to the input interface 12, whereby the CPU 11 causes the motor terminal voltage Vt of the electric motor 30 and the motor current value IMOT.
You can enter R and.

With the above configuration, the drive circuit 20 (that is,
The electric motor 30) is in a state in which power can be supplied from the battery 50 when the relay 21 is turned on (closed), and when the switching elements Tr1 and Tr4 are selectively turned on (on state), the electric motor 30 When a current flows in a predetermined direction in the motor 30, the motor 30 rotates clockwise, and when the switching elements Tr2, Tr3 are selectively turned on, a current flows in the electric motor 30 in a direction opposite to the predetermined direction. The motor 30 rotates counterclockwise. When the relay 21 is turned off (opened), the power supply path of the electric motor 30 is cut off, and the power supply to the motor 30 is stopped.

An ignition switch (I / G switch) is connected to the power supply line L of the battery 50 to be turned on (closed) or off (opened) by a driver.
One end of 22 is connected. The other end of the ignition switch 22 is provided with a CPU 11, an input interface 12, an output interface 13, E via a diode D1.
It is connected to the EPROM 14 and the steering torque sensor 35, and power is supplied to each of them when the ignition switch 22 is turned on. The downstream side of the diode D1 is connected to the downstream side terminal of the relay 21 via a diode D2 that allows only a current flowing from the downstream side of the relay 21 to the downstream side of the diode D1, and the relay 21 is in an ON state. Then, regardless of the state of the ignition switch 22, power is supplied to the CPU 11, the input interface 12, the output interface 13, the EEPROM 14, and the steering torque sensor 35 via the relay 21. The EEPROM 14 is configured to be able to write and read data in a state where it is supplied with power, and hold data in a state where it is not supplied with power.

Next, the operation of the electric power steering system constructed as above will be described with reference to FIGS. 3, FIG. 4, and FIG. 7 to FIG.
4 is a flow chart showing a program (routine) executed by No. 1 and when the ignition switch 22 is changed from the off state to the on state, the routine of FIG. With the passage of time,
FIG. 16 is executed when the ignition switch 22 is changed from the on state to the off state.

First, when the driver changes the ignition switch 22 from the off state to the on state to start driving the vehicle, the CPU 11 executes the ignition switch on control routine shown in FIG.
Start from step 305 and proceed to step 305
The value obtained by multiplying the motor current square integrated storage value SQIMSUMA stored and stored in the EEPROM 14 by 1/4 of the maximum value ITH0 of the motor current limit determination value is the motor current square integrated value SQI.
Set as the initial value of MSUM. The maximum value ITH0 of the motor current limit judgment value and the motor current square integrated storage value SQIMSUMA
Will be described later.

Next, in step 310, the CPU 11 causes the flag FTMB stored / held in the EEPROM 14 to be stored.
Is read from a predetermined address in the EEPROM 14 and the value is set in the flag FTMB. This flag FTMB indicates that the substrate temperature sensor 23 is in an abnormal state by its value "1", and its value "0".
Indicates that the substrate temperature sensor 23 is in a normal state, and the value is changed by a routine described later. Next, the CPU 11 proceeds to step 315 and sets the transient temperature value TTR to 0 ° C. The transient temperature value TTR is used to determine whether or not a condition for determining an abnormality of the substrate temperature sensor 23 described later is satisfied. Thereafter, the CPU 11 changes the relay 21 to the ON state in step 320, proceeds to step 395, and ends this routine.

Thereafter, the CPU 11 executes the processing of the main routine shown in FIG. 4 at a predetermined timing in step 400.
Start from step 410 and proceed to step 410, where the basic target current value TK
Performs IHON calculation. This calculation is performed by the steering torque sensor 35.
Steering torque TM from the vehicle speed V from the vehicle speed sensor 41
And the basic target current value TKIHON at that time based on the basic target current map (table) shown in FIG. 5 stored in the memory 11a. The basic target current map is divided into vehicle speeds (in this case, low vehicle speed, medium vehicle speed, and high vehicle speed), and the CPU 11 determines the actual vehicle speed V.
From the two basic target current maps (the relationship line between the vehicle speed V and the basic target current TKIHON) corresponding to the vehicle speed closest to and the next closest vehicle speed, the basic target current value TKIHON is obtained, and they are interpolated with respect to the vehicle speed V. Determine the final basic target current value TKIHON.

Next, the CPU 11 causes the step 42 in FIG.
In step 0, the inertia compensation current value TKAN for reducing the feeling of inertia of the motor and improving the steering feeling is calculated.
Specifically, the steering torque TM from the steering torque sensor 35
From the map shown in FIG. 6 (A) and the time differential value (dTM / dt) of the same steering torque TM, the inertia value increases as the time differential value dTM / dt of the same steering torque TM increases. The basic value of compensation current TKANB is calculated and is shown in Fig. 5 (B).
Gain k1 is obtained from the map shown in and the actual vehicle speed V,
The product of these (= k1 · TKANB) is the final inertia compensation current value T
KAN.

Next, the CPU 11 causes the step 43 in FIG.
In step 0, the steering wheel return control current value TMOD is calculated to improve the return performance (return performance to the neutral point) of the steering wheel 31 and to compensate the friction of the mechanical system due to steering. Specifically, as shown in the detailed flowchart of FIG. 7, the CPU 11 determines in step 710 that the electric motor 3
Terminal voltage Vt of 0, current value IMOT of the electric motor 30
The rotational angular velocity ω of the electric motor 30 is obtained from R and the voltage equation (K · ω = Vt−R · IMOTR, where K is a constant and R is the resistance value between the terminals of the electric motor 30), and the predetermined value is obtained. The steering angular velocity estimated value STRV is obtained by multiplying by the constant of.

Next, in step 720, the CPU 11 obtains the steering wheel angular velocity estimated value STRV and the steering wheel return control current basic value TMODB from the map shown in step 720, and in step 730, the steering angular velocity estimated value STRV and the steering angular velocity estimated value STRV are used.
The friction compensation current basic value TMASAB is obtained from the map shown in 0, and in the following step 740, the vehicle speed V and the same step 740 are obtained.
The gain k2 is obtained from the map shown in the inside.

Next, the CPU 11 determines in step 750 whether the value of the flag FMOD is "1". This flag
FMOD indicates that the steering wheel 31 is in the returning state at the value "1", and the steering torque TM is a positive value and the estimated steering angular velocity STRV is a negative value for a predetermined time. When the above operation continues, it is set to "1", and in this case, it is set to "0" when the steering angular velocity estimated value STRV becomes a positive value. Similarly, the flag FMOD is set to "1" when the steering torque TM is a negative value and the estimated steering angular velocity value STRV is a positive value for a predetermined time or more. In this case, the steering angular velocity is set. It is set to "0" when the estimated value STRV becomes a negative value.

Then, when the value of the flag FMOD is "1", the CPU 11 sets the value obtained by multiplying the basic value TMODB of the steering wheel return control current by the gain k2 in step 760 as the current steering wheel return control current value TMODX. , FMOD value is "0"
In case of, the friction compensation current basic value TM in step 770
The value obtained by multiplying ASAB by the gain k2 is set as the current steering wheel return control current value TMODX. Next, the CPU 11 uses the calculation formula shown in step 780 (here, knm1 is a constant of 0 to 1) to prevent a sudden change in the handle return control current value TMOD.
Is used to smooth the handle return control current value TMOD, and the final handle return control current value TMOD is calculated.

Next, the CPU 11 causes the step 44 of FIG.
In order to improve the convergence of steering at high vehicle speed and the responsiveness when the driver further steers the steering wheel 31 to a predetermined angle (cut), The damping control current value TDAMP of is calculated. Specifically, as shown in the detailed flowchart of FIG. 8, the CPU 11 determines in step 810 the steering torque.
It is determined whether or not the absolute value of TM is smaller than a predetermined threshold value THD, and if it is smaller (when it is determined to be "Yes"), the process proceeds to step 820, and the estimated steering angular velocity value STRV and the same in step 820 are displayed. The damping control current basic value TDAMPB is calculated from this map.

Next, the CPU 11 proceeds to step 830, obtains the gain k3 from the vehicle speed V and the map shown in step 830, and in step 840, sets the current damping control current value TDAMPX as the damping control current basic value TDAMPB. The product value of gain k3. On the other hand, if “No” is determined in Step 810, in Step 850,
Set the damping control current value TDAMPX of this time to "0". Then, the CPU 11 calculates the damping control current value TDAMP in step 860 in order to prevent the sudden change of the damping control current value TDAMP (here, knm2 is a constant of 0 to 1).
Is used to damp the damping control current value TDAMP, and the final damping control current value TDAMP is calculated.

In step 810, the steering torque is
When the absolute value of TM is larger than the predetermined threshold value THD, the damping control current value TDAPX is set to "0" in step 850 because the damping control value itself imparts a reaction force to the steering and the steering feel. Although it is intended to improve the ring, if it is necessary to truly steer the steering handle 31 quickly and largely, it is necessary to reduce the damping control value to give priority to the steering. is there.

Next, the CPU 11 causes the step 45 of FIG.
In step 0, the ECU side current limit value ILECU for overheat protection of the switching elements Tr1 to Tr4 in the ECU 25 (drive circuit 20) is calculated. Specifically, as shown in the detailed flowchart of FIG. 9, the CPU 11 executes step 9
At 10, a first electric motor current integration value ISUM1 obtained by pseudo integration of the current value IMOTR of the electric motor 30 is obtained. That is,
Using the current value IMOTR of the electric motor 30 and a predetermined smoothing coefficient ke1 from 0 to 1, the value obtained according to the calculation formula shown in step 910 is used as the first electric motor current integral value IS.
UM1

Similarly, in the following step 920, the second electric motor integrated current value ISUM2 obtained by pseudo-integrating the electric current value IMOTR of the electric motor 30 is used as the current value IMOTR and a value between 0 and 1 and is a smoothing coefficient. The coefficient ke2 larger than ke1 is used, and the coefficient is calculated according to the calculation formula shown in step 920. Then, in step 930, the first electric motor current integrated value IS
The sum of UM1 and the second electric motor current integrated value ISUM2 is calculated, and the sum is set as the electric motor current integrated value ISUM. Since the averaging coefficient ke1 is smaller than the averaging coefficient ke2, the first electric motor current integral value ISUM1 mainly reflects a steady fluctuation of the motor current value, while the averaging coefficient ke2 is the averaging coefficient ke1. Since it is larger, the second electric motor integrated current value ISU
M2 is a value that mainly reflects a transient change in the motor current value. Therefore, the electric motor current integral value ISUM, which is the sum of these values, is a value that closely approximates the integral value of the motor current value that actually flows in the electric motor 30.

Next, the CPU 11 proceeds to step 940 and sets a predetermined coefficient ke3 and the electric motor current integral value ISUM.
And the substrate temperature TMPBORD detected by the substrate temperature sensor 23, the calculation formula (TMPECU = ke
3. ISUM + TMPBORD) is calculated to obtain the estimated temperature TMP ECU of the switching elements Tr1 to Tr4. Here, the substrate temperature TMPBORD is the ECU 25 (drive circuit 20)
Is a value that correlates well with the ambient temperature, and the electric motor current integral value ISUM is a value that correlates well with the temperature increase due to heat generation of the switching elements Tr1 to Tr4. Therefore, the switching element estimated temperature TMPECU obtained by adding the value obtained by multiplying the substrate temperature TMPBORD by the electric motor current integral value ISUM as a constant as described above is the actual switching element Tr1 to Tr4.
It is a value that accurately represents the temperature of (MOS junction).

Thereafter, in step 950, the CPU 11 performs the same step 95 as the switching element estimated temperature TMPECU.
The ECU side current limit value ILECU is determined from the map shown in 0. As a result, the ECU side current limit value ILECU becomes smaller as the estimated switching element temperature TMP ECU becomes higher,
The current value of the electric motor 30 is limited to a smaller value.

Next, the CPU 11 executes step 4 in FIG.
In step 60, the motor side current limit value ILMOTR for overheat protection of the electric motor 30 is calculated. Specifically, as shown in the detailed flowchart of FIG. 10, the CPU 11 determines in step 1005 whether the absolute value of the estimated steering angular velocity STRV is larger than a predetermined steering angular velocity (threshold) THSTRV. This is during steering or holding (steering handle 3
This is for distinguishing whether it is a state in which 1 is kept rotated by a predetermined angle).

If the CPU 11 determines in step 1005 to be "Yes" (during steering), the CPU 11 proceeds to step 1010.
To the heat balance balance current THSQIM to the first predetermined value (4
0A) is set, and if it is determined to be “No” (during holding) in step 1005, a second predetermined value (20A) smaller than the first predetermined value is set to the heat balance balance current THSQIM in step 1015. In step 1020, the heat balance balance current THSQI is calculated from the motor current value IMOTR of the electric motor 30.
The value after subtracting M is set as the current after heat balance (also simply referred to as the current after balance) IMBARA. The magnitude of the heat balance balance current THSQIM is a temperature equilibrium state at a predetermined temperature at which the electric motor 30 is not in an overheated state when the electric motor 30 is constantly energized in each of the steering state and the steering state. It is a current value that reaches, and is experimentally obtained in advance.

Next, the CPU 11 proceeds to step 1025 to determine whether the heat balance balance current IMBARA is "0" or more. If the heat balance balance current IMBARA is "0" or more, the process proceeds to step 1030. Go to step 10
The value obtained by multiplying the value obtained by squaring the current IMBARA after heat balance at 30 with a predetermined positive coefficient kup is added to the motor current square integrated value SQIMSUM at that time (already obtained), and the result is added. A new motor current square integrated value SQIMSUM is set, and overflow guard is applied in step 1035 to proceed to step 1040. On the other hand, in step 1025, if the current IMBARA after heat balance is balanced is smaller than “0”, the process proceeds to step 1045, and the current IM after heat balance is balanced.
The value obtained by multiplying the value obtained by squaring BARA by a predetermined positive coefficient kdwn is the motor current square integrated value at that time (which has already been obtained).
Subtraction is performed from SQIMSUM, and the result is set as a new motor current square integrated value SQIMSUM. In step 1050, guard is applied so as not to become "0" or less. The motor current square integrated value SQIMSUM obtained in this way is calculated by the electric motor 30.
It represents the overheated state (temperature).

Next, in step 1040, the CPU 11 determines the motor current limit determination value ITH that decreases as the substrate temperature TMPBORD increases from the actual substrate temperature TMPBORD and the map shown in step 1040. The substrate temperature
When TMPBORD is small, the motor current limit judgment value ITH becomes the maximum value ITH0. Then, the CPU 11 executes step 1055.
Determines whether the motor current square integrated value SQIMSUM is greater than or equal to the motor current limit determination value ITH. If the determination result is “Yes”, in step 1060 the motor-side current limit value ILMOTR is set to a positive value. The value obtained by subtracting the predetermined value α of is set as a new motor-side current limit value ILMOTR, while step 105
If the determination result of 5 is “No”, step 106
In step 5, a value obtained by adding a positive predetermined value β to the motor side current limit value ILMOTR at that time is set as a new motor side current limit value ILMOTR. After that, the CPU 11 guards the motor-side current limit value ILMOTR at predetermined upper and lower limit values (upper limit value Imax, lower limit value Imin) in step 1070, and as a result, the motor-side current limit value is set.
ILMOTR is determined.

Step 1 of the routine shown in FIG.
In 005 to 1015, the value of the heat balance balance current THSQIM during steering (20A) is set to be smaller than the value of the heat balance balance current THSQIM during steering (40A). This is because the change in the rotation angle of the electric motor 30 is small and the brush portion of the motor 30 is likely to be overheated. That is, during steering, the value of the heat balance balance current THSQIM (20A) is set to be smaller than that during steering (40A), whereby the current IMBARA after heat balance balance is increased to increase the motor current 2
The multiplication integrated value SQIMSUM can be easily increased, and thus the motor-side current limit value ILMOTR can be easily decreased to effectively prevent overheating of the electric motor 30. Further, as a result, it is possible to prevent the motor-side current limit value ILMOTR from becoming unnecessarily small in a continuous steering state such as a so-called stationary steering operation state, so that the steering assist force in the state is prevented from becoming too small. be able to.

The heat balance balance current THSQIM is
Even if the electric motor 30 is continuously energized with a current of that magnitude, the electric motor 30 will not reach a temperature below the overheating temperature (for example, 150
Since it has been selected to be a temperature equilibrium state at (° C), the heat balance balance current IMBARA obtained by subtracting the heat balance balance current THSQIM from the actual motor current value IMOTR in step 1020 is , Electric motor 3
The heat dissipation characteristic of 0 is taken into consideration, and the value has a strong correlation with the temperature change from the equilibrium temperature due to energization of the electric motor 30 itself.

Further, in steps 1030 and 1045, the value obtained by multiplying the motor current square integrated value SQIMSUM at that time by the current IMBARA after heat balance balance by the coefficient kup is added, or Motor current squared integrated value
The value obtained by multiplying the squared value of the current IMBARA after heat balance by the coefficient kdwn (different from kup) is subtracted from SQIMSUM. This is due in part to the current value after balancing
The squared current value obtained by squaring IMBARA is a value that expresses the degree of temperature increase or decrease from the equilibrium temperature. Therefore, if the motor current square integrated value SQIMSUM is updated based on this value, the same value will be obtained. This is because the square integrated value SQIMSUM is a value that accurately represents the overheated state of the electric motor. Also, the coefficient
By making kup and kdwn different values, it is possible to make the motor current square integrated value SQIMSUM a value that changes while more conforming to the temperature rising characteristics and temperature falling characteristics of the device (electric motor 30). is there. Note that step 103
0, 1045 may be a step of substantially time-integrating the squared value of the current IMBARA after heat balance.

Further, in step 1040, the motor current limit judgment value ITH is set to a value that decreases as the substrate temperature TMPBORD increases. When the motor current square integrated value SQIMSUM is larger than the motor current limit judgment value ITH, the motor current is judged in step 1060. The reason why the side current limit value ILMOTR is made small is that the motor side current limit value ILMOTR needs to be lowered early because the motor overheats easily when the substrate temperature TMPBORD is high.

In step 1070, the motor side current limit value ILMOTR is guarded so as not to become smaller than the allowable value (lower limit value) Imin. The allowable value Imin is the heat balance balance current THSQIM ( 20A) is preferably the same. This is because the electric motor 31 is not overheated and the assisting force can be generated even if a little.

After calculation of the motor side current limit value ILMOTR,
The CPU 11 proceeds to step 470 of FIG. 4 and executes the current limit value ILTEMP calculation routine shown in detail in FIG.
Specifically, in step 1105, the current limit increase / decrease value ILFG that increases from a negative value to a positive value as the motor current square integrated value SQIMSUM increases is set to the motor current square integrated value SQIMSU.
It is obtained from the map shown in step 1105 of M and step 1110, and it is determined in step 1110 whether the value of the flag FTMB is “1”. As described above, the flag FTMB indicates that the substrate temperature sensor 23 is in the abnormal state by the value “1”, and the substrate temperature sensor 23 is determined by the value “0” in the normal state. This indicates that the state is present, and the value is changed by the routine described later.

When the CPU 11 determines that the value of the flag FTMB is "1", the CPU 11 proceeds to step 1115 and sets a value obtained by subtracting the current limit adjustment value ILFG from the current limit value ILTEMP as a new current limit value ILTEMP. Proceed to step 1135. The above steps 1105 to 1115 are provided to obtain the appropriate current limit value ILTEMP even when the substrate temperature sensor 23 becomes abnormal.

On the other hand, when the CPU 11 determines in step 1110 that the value of the flag FTMB is "0", the CPU 11 proceeds to step 1120 and compares the ECU side current limit value ILECU with the motor side current limit value ILMOTR, and the ECU When the side current limit value ILECU is smaller than the motor side current limit value ILMOTR Step 112
Go to 5 and set the ECU side current limit value ILECU to the current limit value ILTEMP, and the ECU side current limit value ILECU becomes the motor side current limit value IL.
When it is larger than MOTR, the routine proceeds to step 1130, where the motor side current limit value ILMOTR is set to the current limit value ILTEMP, and then the routine proceeds to step 1135. Steps 1120 to above
1130 is the current limit value ILTEMP of the ECU side and the current limit value ILMOTR of the motor side, whichever is smaller is the final current limit value ILTEMP.
This is a step for Then, the CPU 11
In step 1135, the current limit value ILTEMP is guarded with 0 to 50 A, and the final current limit value ILTEMP according to the energization state of the electric motor 30 is determined.

Next, the CPU 11 executes step 4 in FIG.
Proceeding to 80, the final assist current value detailed in FIG.
Execute the IFINAL operation routine. Specifically, the CPU
In step 1205, 11 is the sum of the inertia compensation current value TKAN and the steering wheel return control current value TMOD.
By executing steps 1210 to 1225, the absolute value of the inertia / return current value TKM is guarded so as not to exceed the guard value KG, and the process proceeds to step 1230.

Next, in step 1230, the CPU 11 obtains the sum of the basic target current value TKIHON, the inertia / return current value TKM, and the damping control current value TDAMP, and sets this sum as the assist current value ICTRL. The absolute value of the current value ICTRL is compared with the current limit value ILTEMP. Then, when the absolute value of the assist current value ICTRL is larger than the current limit value ILTEMP, it is determined in step 1240 whether the assist current value ICTRL is positive or negative, and when it is positive, the final assist current value IFINAL is current limited in step 1245. The value ILTEMP is set, and if negative, step 1250
At step 129, the final assist current value IFINAL is set to a value (−ILTEMP) with the sign of the current limit value ILTEMP reversed.
The routine proceeds to step 5 to end this routine once. On the other hand, when it is determined in step 1235 that the absolute value of the assist current value ICTRL is smaller than the current limit value ILTEMP, the CPU 11
Sets the final assist current value IFINAL to the assist current value ICTRL in step 1255, and proceeds to step 1295 to end this routine once. Due to the above, the current limit value ILTEMP
The assist current value (final assist current value) IFINAL limited by is determined.

Incidentally, the above steps 1210 to 1
The reason why the absolute value of the inertia / return current value TKM is prevented from exceeding the guard value KG by executing 225 is as follows. That is, in this electric power steering apparatus, the sub CPU (not shown) monitors the main CPU 11, but since only the steering torque TM is input to the sub CPU, the assist current value calculated by the main CPU 11 is calculated.
The judgment value for judging whether ICTRL is an abnormally large value is the steering torque TM and the basic target current value TKIHON shown in FIG.
It is assumed that a predetermined current value (for example, 5 A) is added to the value obtained from the map. Therefore, the inertia / return current value TKM, which is the sum of the inertia compensation current value TKAN and the steering wheel return control current value TMOD obtained independently of the steering torque TM, should not be guarded below a predetermined current value (5A). In this case, it may be determined that the calculated value is abnormal even though the calculated value is normal.

Next, the CPU 11 executes step 4 in FIG.
At 90, based on the final assist current value IFINAL, well-known PID control and PWM control are performed to determine the energization time of each of the switching elements Tr1 to Tr4, and a control signal is generated to the drive circuit 20 according to this. To do. as a result,
A current corresponding to the final assist current value IFINAL flows through the electric motor 30, and an assist force corresponding to the current is applied to the steering shaft 33. Then, the CPU 11 once terminates this routine at step 495, and again starts the routine from step 400 after a predetermined time.

Next, the abnormality determination of the substrate temperature sensor 23 will be described separately for the following cases. In addition, CPU
11 repeatedly executes the routines of FIGS. 13 and 14 independently of the main routine shown in FIG. 4 at predetermined time intervals. 1: When the temperature condition for performing the abnormality determination is not satisfied 2-1: When the temperature condition for performing the abnormality determination is satisfied and the substrate temperature sensor 23 is normal 2-2: Temperature for performing the abnormality determination When the conditions are met and the substrate temperature sensor 23 becomes abnormal

<1: When the temperature condition for judging abnormality is not satisfied> First, regarding the reference value writing routine of FIG. 13 for acquiring the judgment reference value TMPBORD REF for judging the abnormality of the substrate temperature sensor 23 Explaining, CPU 11
Starts execution of the routine from step 1300 at a predetermined timing, and in subsequent step 1305, it is determined whether or not the transient temperature value TTR is equal to or lower than the reference value acquisition permission temperature (here, 2 ° C.). The transient temperature value TTR is
It is the temperature of the portion near the substrate temperature sensor 23 estimated from the value of the current flowing through the electric motor 30, and the details will be described later.

If the transient temperature value TTR is 2 ° C. or less, the CPU 11 makes a “Yes” determination at step 1305 to proceed to step 1310, at which point the substrate temperature TMPBORD output from the substrate temperature sensor 23 is set. , The reference value for judgment TMPBORD REF is written, and the routine proceeds to step 1395 to end this routine once. On the other hand, when the CPU 11 determines in step 1305 that the transient temperature value TTR is not lower than 2 ° C., the CPU 11 directly proceeds to step 1395 to end the present routine tentatively. Due to the above operation, the transient temperature value TTR
Substrate temperature TMPBORD at a predetermined point when temperature is judged to be 2 ℃ or less
Is written in the judgment reference value TMPBORD REF.

If this routine is executed at a predetermined timing after the ignition switch 22 is changed from the off state to the on state, the transient temperature value TT
Since R is set to 0 ° C. in step 315 of FIG. 3 described above, the CPU 11 sets “Yes” in step 1305.
s ”, and the substrate temperature TMPBORD, which is the output of the substrate temperature sensor 23 at that time, is written in the determination reference value TMPBORD REF.

Further, the CPU 11 executes the abnormality determination routine shown in FIG. 14 at a predetermined timing in step 1400.
Start with. This routine is a routine for determining whether the substrate temperature sensor 23 has become abnormal,
It is configured to include a step of determining whether a temperature condition that allows execution of an abnormality determination of the substrate temperature sensor 23 is satisfied, and a step of determining whether an abnormality has occurred in the substrate temperature sensor 23. There is.

Specifically, the CPU 11 causes the step 14
In 05, the integrated current value IS obtained in step 930 of FIG.
In order to convert UM into temperature, the integrated current value ISUM is multiplied by a predetermined coefficient tm for temperature conversion, and the product value thereof is taken as the transient temperature value TTR. The integrated current value ISUM used in this step is
As shown in steps 910 to 930 in FIG. 9, it is obtained based on the current value IMOTR of the current passed through the electric motor 30, and therefore the transient temperature value TTR is obtained.
A value obtained by estimating the temperature of “a portion of the drive circuit 20 near the substrate temperature sensor 23”, which is a portion where heat is generated by the current passed through 0, based on the current IMOTR passed through the electric motor 30 (depending on the estimated temperature of the heating portion) Value).

Next, the CPU 11 determines in step 1410 whether or not the first temperature condition for the abnormality determination of the substrate temperature sensor 23 is satisfied, and in step 1415 the second temperature determination for the abnormality determination. It is determined whether the temperature condition is satisfied. Specifically, in step 1410, the CPU 11 determines the transient temperature value obtained in step 1405.
It is determined whether TTR is the first reference temperature (here, 10 ° C.) or higher. In this step, the transient temperature value TTR
Is determined to be equal to or higher than the first reference temperature, the electric motor 3
The temperature estimated based on the current value flowing to 0 (that is, the transient temperature value TTR) is the first predetermined temperature (in this case, 10 ° C-2 ° C = 8) from the time when the reference value for determination TMPBORD REF is written.
℃) means that it has changed.

Further, the CPU 11 determines in step 1415 whether the substrate temperature TMPBORD detected by the substrate temperature sensor 23 is equal to or lower than the second reference temperature (here, 160 ° C.). The second reference temperature is selected to be a predetermined high temperature equal to or lower than the maximum temperature that the substrate temperature sensor 23 can detect. In other words, the second reference temperature is selected as a temperature at which the value (resistance value) detected by the substrate temperature sensor 23 changes by a predetermined value or more per unit temperature in a region below that temperature. That is, in this step 1415, since the output characteristic of the substrate temperature sensor 23 is non-linear, the change in the output (resistance value) with respect to the temperature change becomes small at the second reference temperature or higher, and the substrate temperature sensor 23 becomes abnormal. In consideration of the possibility that the accuracy of the determination as to whether or not the temperature is lower than the second reference temperature, it is provided so as not to perform the abnormality determination described below at the second reference temperature or higher.

Steps 1410 and 141 described above
When all of 5 are satisfied, it means that the temperature condition for performing the abnormality determination is satisfied, and the CPU 11 proceeds to step 1425. However, since the temperature condition is not satisfied at the present time, the CPU 11 causes the step 1410 or step 141 to be performed.
5 is determined as “No” in any one of Steps 5 and 142.
The value of the abnormality determination counter C described later is set to "0".
Is set (cleared), and then the routine proceeds to step 1495 to end this routine once.

<2-1: When the temperature condition for making an abnormality determination is satisfied and the substrate temperature sensor 23 is normal> Next, the temperature condition for making an abnormality determination by the subsequent operation is satisfied, and A case where the substrate temperature sensor 23 is normal will be described. When the temperature condition for performing the abnormality determination is satisfied, the CPU 11 determines “Yes” in both steps 1410 and 1415,
Proceed to step 1425. In this step 1425, it is determined whether the value obtained by subtracting the judgment reference value TMPBORD REF from the substrate temperature TMPBORD at that time (that is, the variation width of the detected substrate temperature) is the second predetermined temperature (2.5 ° C. here) or less. To determine.

This is because whether or not the substrate temperature TMPBORD has changed by the second predetermined temperature or more since the judgment reference value TMPBORD REF was written (the temperature change width indicated by the substrate temperature TMPBORD is the second predetermined temperature or less). Whether or not)
The substrate temperature sensor 23 determines whether or not the substrate temperature sensor 23 is in an abnormal state in which the output does not change according to the temperature change. At this stage, since the substrate temperature sensor 23 is not in such an abnormal state, the CPU 11 makes a “No” determination at step 1425 to determine the above-mentioned step 142.
After proceeding to 0 and setting the abnormality determination counter C to "0", this routine is once ended in step 1495.

<2-1: When Temperature Condition for Abnormality Judgment is Established and Substrate Temperature Sensor 23 is Abnormal> As described above, the CPU 11 causes the CPU 11 to execute step 1 in FIG.
When the transient temperature TTR becomes 2 ° C or less at 305 and 1310, the substrate temperature TMPBORD at that time is used as a reference value for determination TMPBO.
It is retained as RD REF, the transient temperature TTR is determined to be 10 ° C. or higher in step 1410 of FIG. 14, and step 1
When it is determined in 415 that the substrate temperature TMPBORD at that time is 160 ° C. or lower, it is determined in step 1425 that the difference between the substrate temperature TMPBORD at the same point and the reference value for determination TMPBORD REF is 2.5 ° C. or more. To determine. Moreover, these steps are repeatedly executed at predetermined time intervals.

Therefore, if an abnormality occurs in the substrate temperature sensor 23 and the substrate temperature TMPBORD detected by the substrate temperature sensor 23 does not change even if the actual temperature rises, the CPU 1
1 is determined as “Yes” in step 1425. In this case, the CPU 11 proceeds to the next step 1430.
The abnormality determination counter C is incremented by "1" at step 1435, and it is determined at step 1435 whether the value of the counter C is greater than the reference determination value C0 (in this case, 30 seconds).

Immediately after the occurrence of such an abnormality, the value of the counter C is smaller than the reference judgment value C0, so that the CPU 11 makes a "No" determination at step 1435 to proceed directly to step 1495 to execute this routine. It ends once. Then, when such an abnormal state continues, the value of the counter C gradually increases due to the execution of step 1430, and exceeds the reference determination value C0 after the elapse of a predetermined time. As a result, the CPU 11 determines “Yes” in step 1435 and proceeds to step 1440. In step 1440, the CPU 11 writes in the EEPROM 14 the fact that the substrate temperature sensor 23 has become abnormal (abnormality in which output change does not occur).

Then, the CPU 11 proceeds to step 1445.
Go to and set the value of the flag FTMB to "1", and then set the flag FTMB.
The value of MB (that is, "1") is written to a predetermined address in the EEPROM 14, and then the routine proceeds to step 1495 to end this routine once. In this way, the abnormality of the substrate temperature sensor 23 is detected. In addition, when the value of the counter C becomes larger than the reference determination value C0, the substrate temperature sensor 23 is determined to be abnormal.
This is because when it is determined that there is a suspicion of an abnormality a plurality of times in succession, it is determined that the substrate temperature sensor 23 is abnormal, so that the determination accuracy can be further improved.

Next, with reference to FIG. 15, a normality determination routine for monitoring / determining whether or not the substrate temperature sensor 23 has returned to a normal state after it has been determined to be abnormal will be described. . Since the CPU 11 also repeatedly executes this routine every predetermined time, the CPU 11 starts the process from step 1500 at a predetermined timing, proceeds to step 1505, and determines whether or not the value of the flag FTMB is "1" ( That is, it is determined whether or not the substrate temperature sensor 23 is in an abnormal state, and the flag FT
If the value of MB is "0", this routine is immediately terminated in step 1595.

On the other hand, when the substrate temperature sensor 23 is determined to be abnormal, the value of the flag FTMB is "1", so the CPU 11 returns "Yes" in step 1505.
And proceeds to step 1510, and the same step 151
At 0, it is determined whether the transient temperature TTR is equal to or higher than the normal determination reference temperature (here, 10 ° C.). If the transient temperature TTR is not higher than the reference temperature for normality determination, the CPU
The No. 11 determines "No" in step 1510, advances to step 1595, and ends this routine once.

On the other hand, if the transient temperature TTR is equal to or higher than the reference temperature for normality determination, the CPU 11 makes a “Yes” determination at step 1510 to proceed to step 1515. The case where “Yes” is determined in step 1510 is the same as the case where “Yes” is determined in step 1410 of FIG. 14 described above, and the temperature (based on the current value flowing through the electric motor 30 ( That is, it means that the transient temperature value TTR) has changed by the first predetermined temperature (in this case, 10 ° C.−2 ° C. = 8 ° C.) from the time when the reference value TMPBORD REF for determination was written.

Step 1515 corresponds to step 1 in FIG.
425 is a step of performing the same processing, and the value obtained by subtracting the determination reference value TMPBORD REF from the substrate temperature TMPBORD at that time (detected substrate temperature change width) is different from the third predetermined temperature (second predetermined temperature). It may be set to 2.5 ° C. here) It is determined whether or not the temperature is higher than or equal to.

This is because the substrate temperature sensor 2 is determined by determining whether or not the substrate temperature TMPBORD has changed by the third predetermined temperature or more since the determination reference value TMPBORD REF was written.
3 determines whether or not the state has returned to the normal state in which the output changes according to the temperature change. Then, when it is determined “No” in the same step 1515, it can be determined that the substrate temperature sensor 23 has not returned to the normal state, and therefore the CPU 11 proceeds to step 1595 to end the present routine tentatively. On the other hand, in step 1515, “Yes
When it is determined to be “s”, it can be determined that the substrate temperature sensor 23 has returned to the normal state. In this case, the CPU 11
Advances to step 1520 and changes the value of the flag FTMB from "1" to "0".

Next, the CPU 11 proceeds to step 1525, writes the value of FTMB (that is, "0") to a predetermined address in the EEPROM 14, and then in step 1530, sets the value of the abnormality determination counter C to "0". After that, the routine proceeds to step 1595 to end this routine once. In this way, it is detected that the substrate temperature sensor 23 has returned from the abnormal state to the normal state.

Next, the case where the ignition switch 22 is changed from the on state to the off state will be described. The CPU 11 uses the change of the ignition switch 22 from the on state to the off state as a trigger to execute the routine shown in FIG. Starting at 1600, step 16
Go to 05. In step 1605, the CPU 11 determines whether the motor current square integrated value SQIMSUM is smaller than 1/4 of the maximum value ITH0 of the motor current limit determination values, and the motor current square integrated value SQIMSUM determines the motor current limitation. If it is smaller than 1/4 of the maximum value ITH0, step 161
At 0, the value "0" is set to the motor current square integrated storage value SQIMSUMA stored in the EEPROM 14, and this value is set to EE.
It is stored in the PROM 14.

When it is determined to be "No" in step 1605, the CPU 11 determines in step 1615 that the motor current square integrated value SQIMSUM is 1/4 or more to 1/2 of the maximum value ITH0 of the motor current limit determination value. If the determination result is “Yes”, the value “1” is stored in the motor current square integrated storage value SQIMSUMA in step 1620, and the process proceeds to step 1640. If it is determined as “No” in step 1615, the CP
U11 is the motor current squared integrated value SQ in step 1625.
It is determined whether IMSUM is in the range of ½ or more to 3/4 of the maximum value ITH0 of the motor current limit determination value. If the determination result is “Yes”, the motor current 2 is determined in step 1630. The value "2" is stored in the multiplication and accumulation stored value SQIMSUMA, and the process proceeds to step 1640. Then, if “No” is determined in Step 1625, the value “3” is stored in the motor current square integrated storage value SQIMSUMA in Step 1635, the process proceeds to Step 1640, and the relay 21 is performed in Step 1640. To the off state.

As described above, the ignition switch 22
The motor current 2 which is one of the data related to the current limit value ILTEMP when the ON state is changed to the OFF state.
The integrated value SQIMSUM is the maximum value of the motor current limit judgment value ITH0
Is converted into a value according to the ratio to the motor current square integrated storage value SQIMSU in the EEPROM 14.
Memorized as MA. As a result, when the driver again changes the ignition switch 22 from the off state to the on state, the stored motor current square integrated storage value SQIMSUMA is set to the maximum motor current limit determination value by the routine shown in FIG. A value obtained by multiplying 1/4 of the value ITH0 is obtained (step 305), and the value is subsequently updated according to the energization state of the electric motor 30, the motor current square integrated value SQIM.
It is set as the initial value of SUM (steps 1030, 1 in FIG. 10).
045).

Therefore, when the ignition switch 22 is changed from the ON state to the OFF state, the data regarding the current limit value (data corresponding to the motor current square integrated value SQIMSUM) can be held without imposing a burden on the battery 50. Ignition switch 2
The data (motor current square integrated value SQIMSUMA) held when 2 is turned on is read out and updated according to the energization state of the electric motor 30. The motor current square integrated value SQIMSUM Since the ignition switch 22 is initially turned off from the on state and then changed to the on state within a short time, the current limit value ILTEMP becomes an appropriate value. The final assist current value (IFINAL) can be set to the optimum value,
It is possible to reliably prevent overheating of the drive circuit 20 and the electric motor 30.

In the above, the reference value when the motor current square integrated value SQIMSUM, which is one of the current limit value data, is stored as the motor current square integrated storage value SQIMSUMA is the motor current limit determination value. Maximum value of ITH0. This is usually the motor current squared integrated value SQIMSUM
Is greater than (the maximum value of ITH0 of) the motor current limit judgment value, the motor current value IMOTR is limited. Therefore, the motor current value IMOTR becomes the maximum value ITH of the motor current limit judgment value.
It is unlikely that the value will be significantly larger than 0, and therefore the maximum value ITH0 of the motor current limit judgment value (that is, a value near the maximum value of the motor current IMOTR for which the current is limited) is used as a reference. By storing the ratio, it is possible to improve the accuracy of the stored data (use a small LSB) while using a small capacity.

The motor current square integrated value SQIMSUM obtained as described above is a value obtained by subtracting the heat balance balance current THSQIM from the actual motor current value IMOTR, which is a value to which the heat radiation characteristics of the electric motor 30 are added ( That is, the basic data is the current IMBARA after heat balance.
Also, since it is a value calculated based on a value obtained by squaring the current IMBARA after balancing the heat balance, the electric motor 3
The value well reflects the degree of temperature increase or decrease from the equilibrium temperature of 0. As a result, according to the above device, the overheated state of the electric motor 30 is accurately estimated, and the current limitation based on the estimation becomes appropriate. Moreover, since the overheated state of the electric motor 30 can be estimated without using a temperature sensor that directly detects the temperature of the electric motor 30, it is possible to reduce the manufacturing cost.

As described above, in the electric power steering apparatus according to the embodiment of the present invention, the temperature of the heat generating portion is determined based on the current value of the current passed through the electric motor 30 at a predetermined time (transient). First predetermined temperature (8 ° C) from the temperature when the temperature value TTR becomes 2 ° C or less)
It is determined whether or not the change has occurred (step 1305).
1310, 1410). Then, when this temperature condition is satisfied, the substrate temperature sensor 2 serving as the temperature detecting means is provided.
When the condition that the detected temperature TMPBORD according to 3 does not change from the detected temperature (TMPBORD REF) at the predetermined time point by the second predetermined temperature (2.5 ° C.) or more is satisfied, it is determined that the temperature detection means is abnormal. (Steps 1425 to 1450). Therefore, it is possible to reliably detect an abnormal state that does not change while indicating a temperature within the temperature range that can be detected by the substrate temperature sensor 23.

Further, in the above-described embodiment, the determination as to whether or not the temperature condition for permitting the execution of the abnormality determination of the temperature detecting means is established, the value corresponding to the current value (IMOTR) of the electric motor 30 is set as the time. Accumulate over time (steps 910-93
0), based on this integrated value (ISUM), a value corresponding to the temperature of the portion near the installation position of the printed circuit board temperature sensor 23 is obtained (step 1405), and the process is performed based on this temperature estimated value. . As a result, the electric motor 3
Since the integrated value obtained by integrating the value corresponding to the current value (IMOTR) of 0 with the passage of time has a strong correlation with the temperature (temperature change) of the heat generating portion, the accuracy of the determination as to whether or not the temperature condition is satisfied is high. improves. The value corresponding to the current value of the electric motor may be a value obtained by squaring the same current value, a value obtained by squaring the same current value, or the like.

In the above embodiment, the substrate temperature sensor 2 is used.
3 is configured to perform the abnormality determination of the substrate temperature sensor 23 when the condition indicating the abnormality is satisfied when the temperature is equal to or lower than a predetermined high temperature (160 ° C.) lower than the maximum temperature (250 ° C.) that can be detected by (Step 141
5). As a result, the change in the output (resistance value) of the substrate temperature sensor 23 with respect to the actual change in temperature is small, so that it is possible to reduce the possibility of erroneously determining that the output is normal but abnormal.

Further, in the above embodiment, when the value of the flag FTMB is changed, the value of the flag FTMB is stored in a predetermined address of the EEPROM 14 (steps 1445, 15).
25), it is memorized that the substrate temperature sensor 23 is in a state of being determined to be abnormal even when the ignition switch 22 is turned off, and when the ignition switch 22 is changed to the on state next time, EEPROM
The value of the flag FTMB stored at a predetermined address of 14 is read out and written in the flag FTMB (step 310).

Therefore, when the substrate temperature sensor 23 is abnormal, the ignition switch 22 is once turned off, and when it is turned on thereafter, it is immediately recognized that the substrate temperature sensor 23 is abnormal. It becomes possible to execute the current control (steps 1110-1135),
It is possible to properly limit the current value passed through the electric motor 30.

In the above embodiment, the substrate temperature sensor 2 is used.
When it is determined that 3 is abnormal, in addition to the value of the flag FTMB, that fact is written to a predetermined address of the EEPROM 14 (step 1440). Therefore, when checking the vehicle, the EEPROM 14
By reading the contents of
Since it is possible to determine whether or not 3 has been determined to be abnormal even once, there is also an advantage that even if the substrate temperature sensor 23 is returned to the normal state, repair / inspection becomes easy.

Although one embodiment of the present invention has been described above, various modifications can be made within the scope of the present invention. For example, in the above embodiment, the motor current 2
The squared integrated value SQIMSUM is classified into four stages, and the distinguished result is stored as the motor current squared integrated memory value SQIMSUMA. The motor current squared integrated value SQIMSUM is compared with the maximum value ITH0 of the motor current limit judgment value. It is also possible to calculate what percentage it is and store the calculation result with LSB as 1%, for example.

Further, in the above embodiment, when the ignition switch 22 is changed from the ON state to the OFF state, the motor current square integrated value SQIMSUM (ratio) is stored in the EEPROM 14. Can be stored at a predetermined timing when the power is supplied (when the relay 21 or the ignition switch 22 is in the ON state).
Even in this case, since the relay 21 is normally turned off within a short time after the ignition switch 22 is turned off, the value stored in the EEPROM 14 changes from the on state of the ignition switch 22 to the off state. The value is substantially equal to the value at time.

Further, in the above embodiment, the assist current value ICTRL is obtained from the basic target current value TKIHON, the inertia compensation current value TKAN, the handle return control current value TMOD and the damping control current value TDAMP, but it is not limited to this. However, it may be calculated from the basic target current value TKIHON and the steering wheel return control current value TMOD, for example.

In the above embodiment, the motor side current limit value I is calculated based on the motor current square integrated value SQIMSUM.
The LMOTR is calculated. The average current value of the electric motor 30 is calculated, and a coefficient that decreases as the average current increases is calculated.
By multiplying the assist current value ICTRL by the coefficient,
The configuration may be such that the final assist current value IFINAL is determined. In this case, when the ignition switch 22 changes from the ON state to the OFF state, the EE
The data stored in the PROM 14 is the average current value.

In the above embodiment, the coefficients kup and kdwn in steps 1030 and 1040 in FIG. 10 are different values, but they may be the same value, and the values α and β in steps 1060 and 1065 may be different. May have different values or the same value.

The substrate temperature indicated by the substrate temperature sensor 23
When TMPBORD is equal to or lower than the minimum value (for example, −50 ° C. or lower) or higher than or equal to the maximum value (for example, 250 ° C. or higher) of the planned temperature range, it is determined that the substrate temperature sensor 23 is abnormal such as short circuit or disconnection. However, if the abnormality display flag FTMC different from the flag FTMB is set to "1" and the substrate temperature TMPBORD is within the predetermined temperature range, the substrate temperature sensor 23
Is added to the flag FTMC and the flag FTMC is set to “0”, and a routine to be executed every predetermined time is added.
By changing to a step of determining whether or not at least one of them is "1", it is possible to properly cope with an abnormality such as a short circuit or a disconnection of the substrate temperature sensor 23.

In the above embodiment, the substrate temperature sensor 2 is used.
However, the present invention is not limited to this. For example, when the electric power steering device has a temperature sensor in the electric motor 30, the abnormality of the temperature sensor is the same. Can be detected.

In the above embodiment, the substrate temperature sensor 2 is used.
3 is configured to perform the abnormality determination of the substrate temperature sensor 23 when the condition indicating the abnormality is satisfied when the temperature is equal to or lower than a predetermined high temperature (160 ° C.) lower than the maximum temperature that can be detected. In the case where the substrate temperature sensor is composed of a positive temperature coefficient thermistor whose resistance value increases as the detected temperature rises, when the substrate temperature sensor 23 is at a predetermined low temperature or higher than the minimum temperature that can be detected,
The substrate temperature sensor 23 may be configured to make an abnormality determination.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an electric power steering device according to a first embodiment of the present invention.

FIG. 2 is an electric circuit diagram of the electric power steering apparatus shown in FIG.

FIG. 3 is a flowchart showing a program executed by the CPU shown in FIG.

FIG. 4 is a flowchart showing a program executed by the CPU shown in FIG.

FIG. 5 is a map (table) showing basic target current values.

FIG. 6A is a map showing a basic value of inertia compensation current,
(B) is a map showing the gain.

FIG. 7 is a flowchart showing a program executed by the CPU shown in FIG.

8 is a flowchart showing a program executed by the CPU shown in FIG.

9 is a flowchart showing a program executed by the CPU shown in FIG.

10 is a flowchart showing a program executed by the CPU shown in FIG.

11 is a flowchart showing a program executed by the CPU shown in FIG.

12 is a flowchart showing a program executed by the CPU shown in FIG.

13 is a flowchart showing a program executed by the CPU shown in FIG.

14 is a flowchart showing a program executed by the CPU shown in FIG.

15 is a flowchart showing a program executed by the CPU shown in FIG.

16 is a flowchart showing a program executed by the CPU shown in FIG.

17 is a diagram showing output characteristics of the substrate temperature sensor shown in FIG.

[Explanation of symbols]

10 ... Electric control circuit, 11a ... Memory, 20 ... Drive circuit, 21 ... Relay, 22 ... Ignition switch, 2
3 ... Substrate temperature sensor, 30 ... DC electric motor, 31 ... Steering handle, 32 ... Reduction mechanism, 33 ... Steering shaft, 35 ... Steering torque sensor, 50 ... Battery, Tr1-Tr4 ... Switching elements.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI B62D 127: 00 B62D 127: 00 (58) Fields investigated (Int.Cl. ⁷ , DB name) B62D 6/00 B62D 5/04

Claims (3)

(57) [Claims] 1. An electric power steering apparatus for a vehicle, comprising an electric motor for generating an assisting force for a turning operation of a steering wheel when a current according to a driving state of the vehicle is supplied to the electric power steering apparatus. And a temperature condition determining means for determining whether or not the value according to the estimated temperature of the heat generating portion obtained based on the current value of the current passed through the electric motor has changed by a predetermined value or more. When the temperature detected by the temperature detecting means has not changed by a predetermined temperature or more when it is determined that the value corresponding to the estimated temperature of the heat generating portion has changed by the predetermined value or more, the temperature detecting means is abnormal. An electric power steering apparatus for a vehicle, comprising: an abnormality determining unit that determines that there is an electric power steering apparatus. 2. The temperature condition determining means integrates values corresponding to the current value of the electric motor as time passes, and obtains a value corresponding to the estimated temperature of the heat generating portion based on the integrated value. The electric power steering device according to claim 1, which is configured as follows. 3. The abnormality determining means detects a temperature not higher than a predetermined high temperature which is not higher than a maximum temperature which the temperature detecting means can detect, or when the temperature detecting means has a high temperature. The abnormality determination of the temperature detecting means is performed when a temperature of a predetermined low temperature or more higher than a minimum temperature that can be detected is detected.
Alternatively, the electric power steering device according to claim 2.