MOTOR CONTROL UNIT AND ELECTRIC POWER STEERING APPARATUS EQUIPPED WITH THE SAME

Abstract

A motor control unit that driving-controls a motor by an inverter based on a current command value, including: a voltage detecting section to detect a power supply voltage of a power supply connected to the inverter, a temperature detection device disposed on a wiring pattern of a circuit substrate between the inverter and the power supply, a voltage-dividing circuit to divide with the power supply voltage using the temperature detection device and resistors, a temperature detecting section to detect a temperature of the wiring pattern based on a dividing voltage from the voltage-dividing circuit and a voltage detected value detected in the voltage detecting section, and an overheat protection control section to limit the current command value based on a temperature detected value of the temperature detecting section, wherein the temperature detecting section detects the temperature of the wiring pattern using a predetermined equation or a data table in which data are preliminarily set without affecting the power supply voltage.

Claims

1.-8. (canceled)

9. A motor control unit that driving-controls a motor by an inverter based on a current command value, comprising: a voltage detecting section to detect a power supply voltage of a power supply connected to said inverter; a temperature detection device disposed on a wiring pattern of a circuit substrate between said inverter and said power supply; a voltage-dividing circuit to divide with said power supply voltage using said temperature detection device and resistors; a temperature detecting section to detect a temperature of said wiring pattern based on a dividing voltage from said voltage-dividing circuit and a voltage detected-value detected in said voltage detecting section; and an overheat protection control section to limit said current command value based on a temperature detected-value of said temperature detecting section, wherein said temperature detecting section detects said temperature of said wiring pattern using a predetermined equation or a data table in which data are preliminarily set without affecting said power supply voltage.

10. The motor control unit according to claim 9, wherein, in said circuit substrate, a thickness of said wiring pattern between said inverter and said power supply in which said temperature detection device is disposed, is uniform, and a width of said wiring pattern between said inverter and said power supply is narrower than widths of said wiring patterns of other portions.

11. The motor control unit according to claim 9, wherein, in said circuit substrate, a width of said wiring pattern between said inverter and said power supply in which said temperature detection device is disposed, is uniform, and a thickness of said wiring pattern between said inverter and said power supply is thinner than thicknesses of said wiring patterns of other portions.

12. The motor control unit according to claim 9, wherein said wiring pattern between said inverter and said power supply in which said temperature detection device is disposed, has a structure that heat is hardly dissipated at a back surface of said circuit substrate, at an interior of said circuit of said circuit substrate, or around said wiring pattern.

13. The motor control unit according to claim 9, wherein at least one of a thermal VIA, a grease and a heat sink is used in a back surface of said circuit substrate.

14. The motor control unit according to claim 9, wherein said circuit substrate is a multilayer substrate, and said temperature detection device is disposed on an outermost layer of said multilayer substrate.

15. The motor control unit according to claim 14, wherein said temperature detection device is a thermistor.

16. An electric power steering apparatus, comprising said motor control unit according to claim 9.

17. An electric power steering apparatus, comprising said motor control unit according to claim 15.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In the accompanying drawings:

[0030] FIG. 1 is a configuration diagram showing a general outline of an electric power steering apparatus;

[0031] FIG. 2 is a block diagram showing a general configuration example of a control unit (ECU) of the electric power steering apparatus;

[0032] FIG. 3 is a circuit diagram showing a configuration example of a motor control section of the electric power steering apparatus;

[0033] FIG. 4 is a cross-sectional view of a substrate showing a conventional arrangement example of a thermistor;

[0034] FIG. 5 is a block diagram showing a configuration example of the present invention;

[0035] FIG. 6 is a cross-sectional view of a substrate showing an arrangement example of the thermistor according to the present invention;

[0036] FIG. 7 is a connection diagram showing a configuration example of a voltage-dividing circuit;

[0037] FIG. 8 is a characteristic diagram showing an example of a data table of a temperature conversion;

[0038] FIGS. 9A and 9B are plan views showing an adjustment example of a heat generation amount of a wiring pattern in a circuit substrate;

[0039] FIGS. 10A, 10B, and 10C are cross-sectional views of the other adjustment example of the heat generation amount of the wiring pattern in the circuit substrate and FIG. 10D is a partial plan view; and

[0040] FIG. 11 is a plan view showing an example of arranging a temperature detection device of the present invention to the circuit substrate, in comparison with the conventional example.

MODE FOR CARRYING OUT THE INVENTION

[0041] In an inverter of a motor control unit equipped with an EPS and the like, the present invention provides a motor driving unit having an excellent transient response of a temperature detection of a heat generation portion by directly connecting the electrical conductive wiring pattern (having an excellent heat conductivity) of a power supply line (a VR line) of an inverter in which heat is easily generated, to one contact point of a temperature detection device such as, for example, a thermistor, and connecting a power supply (VR) to the other contact point. Concretely, the first dividing voltage of a power supply voltage connected between the temperature detection device (the power supply side) and a resistor (a GND (ground) side) is detected, and the second dividing voltage of the power supply voltage connected between the power supply and a resistor which is connected to a ground is detected. An influence of voltage variation of the power supply is removed by dividing the first dividing voltage by the second dividing voltage, and then the temperature (the temperature of the wiring pattern which is connected to the one contact point of the temperature detection device) can be detected by the calculation or referring a data table of a temperature conversion. Normally, since the power supply voltage is substantially the same as a battery voltage of a vehicle, the voltage variation is large. Since the voltage variation due to the motor driving is remarkable, it is necessary to remove the variation of the power supply voltage, in order to perform the accurate temperature detection.

[0042] In the present invention, a shape of the wiring pattern is modified so that the heat generation amount of the electrical conductive wiring pattern of the power supply line, which is the temperature detection portion, becomes large. Concretely, the width of the wiring pattern of the circuit substrate in which the temperature is detected is partially narrow, the number of thermal VIAs of the wiring pattern in which the temperature is detected is adjusted, or the heat around the wiring pattern in which the temperature is detected is hardly dissipated to a heat sink. Thereby, overheat protection having the high degree of freedom can be performed by increasing the heat generation of the wiring pattern of the power supply line, and the temperature of the components by which the inverter is constituted can surely be prevented from becoming higher than the heat resistant temperature of the components.

[0043] In the inverter which drives the motor, by directly disposing the temperature detection device on the wiring pattern of the power supply line in which the heat is easily generated, and detecting the temperature, the present invention provides the motor control unit which has a high thermal binding between the heat generation portion and the temperature detection device, and an excellent temperature detection performance. Since the surplus heat conductive material and the special substrate process are not required for the circuit substrate in order to enhance the thermal binding between the heat generation portion and the temperature detection device, a cost can be reduced. Conventionally, in order to enhance the heat transfer of the temperature detection device from the heat generation portion, the thermal VIA and the heat conductive member are additionally provided. Contrarily, in the present invention, an inclusion such as thermal grease is not existed from the heat generation section to the temperature detection device, and the new thermal via (the new thermal VIA) and the like are not provided to increase the heat transfer efficiency between the heat generation portion and the temperature detection device, neither.

[0044] Furthermore, in the present invention, the design is performed as follows. The width of the wiring pattern of the temperature detecting section is narrow and the heat around the detection portion is hardly dissipated to the heat sink and the like. Thereby, the heat is intentionally and largely generated at the temperature detecting section, and the heat generation amount can be adjusted. Based on the detected temperature, a degree of freedom for designing a threshold of the overheat protection can be improved, and the temperature of the components by which the inverter is constituted can be prevented from becoming higher than the heat resistant temperature of the components.

[0045] Embodiments according to the present invention will be described with reference to the drawings in detail.

[0046] FIG. 5 shows a configuration example of the present invention, corresponding to FIG. 3. The thermistor 130 as the temperature detection device is connected to the power supply line of the inverter 106, and large-capacitance capacitors C1 to C3 which are connected to the power supply line are disposed at respective arms. In the present invention, a power supply voltage for the thermistor 130 is not disposed, and the power supply voltage VR which is used in the inverter 106 is applied to the thermistor 130. The large-capacitance capacitors C1 to C3 are constituted by electrolytic capacitors, conductive polymer hybrid electrolytic capacitors, or the like. Arrows in the inverter 106 denote a direction of a current. Solid lines denote the direction of the current when the upper-arm FETs are turned-ON, and dashed lines denote the direction of the current passed through parasitic diodes when the upper-arm FETs are turned-OFF. As described above, since the currents are passed through the FETs by rotations of the motor 20 regardless of turning-ON or turning-OFF the FETs, the temperature of the wiring pattern of the power supply voltage VR increases. Therefore, it is important to accurately detect the temperature at the above portion. It is considered that the variation of the power supply voltage VR is large.

[0047] A voltage detecting section 143 to detect the power supply voltage and a voltage-dividing circuit 144 to divide with the power supply voltage using the thermistor 130 and resistors are connected to the inverter 106. The power supply voltage VRd detected at the voltage detecting section 143 and dividing voltages V1 and V2 of the voltage-dividing circuit 144 are inputted into a temperature detecting section 142, and the temperature detecting section 142 detects the temperature using a temperature conversion data table or the like. A temperature detection value Tm detected at the temperature detecting section 142 is inputted into an overheat protection control section 141, and the overheat protection control section 141 inputs a current limit value Ir to a motor driving control section 140. The motor driving control section 140 limits a current command value (an assist command) based on the current limit value Ir.

[0048] FIG. 6 shows an arrangement example of the thermistor 130, corresponding to FIG. 4. The thermistor 130 is disposed on the wiring pattern by using a solder 130A. In this example, the thermal VIA is existed, but the thermal VIA may not be disposed.

[0049] FIG. 7 shows a configuration example of the voltage-dividing circuit 144 and a connection example of the thermistor 130. One end of the thermistor 130 is connected to the power supply voltage VR, and the other end of the thermistor 130 is connected to the ground (GND) through the resistor R1. A voltage-dividing circuit of the resistors R3 and R4 is disposed between the power supply and the ground. Here, assuming that the power supply voltage and the resistor of the thermistor 130 are set to VR and RZ, respectively, an output voltage V1 of the voltage-dividing circuit comprising the thermistor 130 and the resistor R1 is represented by a following Expression 1. The output voltage V1 is affected by the variation of the power supply voltage VR.

[00001]$\begin{array}{cc}V.Math..Math.1=\frac{R.Math..Math.1}{R.Math.1+R.Math.Z}V.Math.R& \left[\mathrm{Expression}.Math..Math.1\right]\end{array}$

[0050] The output voltage V2 of the voltage-dividing circuit comprising the resistors R3 and R4 is represented by the following Expression 2. As well, the output voltage V2 is affected by the variation of the power supply voltage VR.

[00002]$\begin{array}{cc}V.Math.2=\frac{R.Math.3}{R.Math.3+R.Math.4}V.Math.R& \left[\mathrm{Expression}.Math..Math.2\right]\end{array}$

[0051] The voltages V1 and V2 from the voltage-dividing circuit 144 are inputted into the temperature detecting 142, are performed an analog to digital conversion (an A/D conversion). The digital values of the voltages V1 and V2 are set to VAL1 and VAL2, respectively. A value VAL3 is obtained by dividing the digital value VAL1 by the digital value VAL2. That is, the value VAL3 is represented by the following Expression 3.

[00003]$\begin{array}{cc}\mathrm{VAL}.Math..Math.3=\frac{\mathrm{VAL}.Math..Math.1}{\mathrm{VAL}.Math..Math.2}=\frac{\frac{R.Math..Math.1}{R.Math.1+R.Math.Z}V.Math.R}{\frac{R.Math.3}{R.Math.3+R.Math.4}V.Math.R}=\frac{R.Math.1}{R.Math.3}\frac{R.Math.3+R.Math.4}{R.Math.1+R.Math.Z}& \left[\mathrm{Expression}.Math..Math.3\right]\end{array}$

[0052] In the above Expression 3, since the resistors R1, R3 and R4 are a fixed value and the term of the power supply voltage VR is removed, the value VAL3 is dependent on only the resistor RZ of the thermistor 130. Thus, by preliminarily preparing the data table with reference to a relationship between the resistor of the thermistor 130 and the temperature, or by performing the calculation, the temperature Tm can be detected. That is, as shown in FIG. 8, by performing the temperature detection using the relationship between the value VAL3 and the temperature detection value Tm, even when the configuration including the power supply voltage whose voltage variation is large is used, the temperature can accurately be detected without being affected by the voltage variation. Generally, assuming that the thermistor resistance is set to R.sub.0 when the temperature is T.sub.0 [K], the thermistor resistance RZ when the temperature is T [K] is represented by the following Expression 4.

[00004]$\begin{array}{cc}\mathrm{RZ}=R_0.Math.\exp .Math.\left\{B\left(\frac{1}{T}-\frac{1}{T_0}\right)\right\}& \left[\mathrm{Expression}.Math..Math.4\right]\end{array}$ [0053] Here, B is called as a B-constant of the thermistor, and the values of B are different in the respective thermistors. Further, a Steinhart-Hart Expression (Expression 5) whose approximate accuracy is higher than the Expression 4 is used as an approximate expression of the temperature resistance characteristic of the thermistor.

[00005]$\begin{array}{cc}\frac{1}{T}=a+b.Math.1_n.Math.\left(R.Math.Z\right)+c.Math..Math.1_n^3.Math.\left(R.Math.Z\right)& \left[\mathrm{Expression}.Math..Math.5\right]\end{array}$ [0054] Here, a, b and c are called as Steinhart-Hart parameters, and those values are specified in the respective thermistors.

[0055] It is understood that the thermistor resistance RZ is dependent on the temperature from the Expression 4, and the thermistor temperature T, that is, the temperature of the wiring pattern on which the thermistor 130 is disposed is obtained by measuring the thermistor resistance RZ from the Expression 5. A periodic detection is not used in the present invention. A detection of a channel CH1 that the power supply voltage VR (VRd) is measured and the A/D conversion is performed to the measured voltage VR (VRd), a detection of a channel CH2 that the divider voltage value V1 of the thermistor 130 is measured and the A/D conversion is performed to the measured voltage V1, and a detection of a channel CH3 that the dividing voltage value V2 of the voltage dividing circuit 144 is measured and the A/D conversion is performed to the measured voltage V2 are simultaneously sampled. The temperature calculating section 142 detects the temperature of the thermistor 130 by using the above expression or by using the preliminarily calculated temperature measurement data table.

[0056] The overheat protection control section 141 suppresses the temperature increase of the components of the inverter 106 by slightly limiting the current command value or stopping the motor driving depending on the temperature detected value Tm. That is, in accordance with the temperature detected value Tm, the current command value (the assist command) is reduced and is limited, or the motor driving is stopped. Besides, the stop of the motor driving may be performed when the temperature detection value Tm is higher than a predetermined value Tm2.

[0057] Further, a correlation value between the temperature increase of the components of the inverter 106 and the temperature detected value Tm is preliminarily analyzed by an experiment or the like. A temperature that is higher than the temperature detection value Tm1 when the temperature of any of the components is the same as the heat resistant temperature, is set to an overheat protection start temperature (a threshold temperature). Thereby, the temperatures of the components can be prevented from exceeding the heat resistant temperature.

[0058] When the motor current control is performed, the large current is often passed through the power supply line of the inverter. The heat is easily generated in the power supply line of the inverter by the heat transfer from the pattern resistance of the circuit substrate and the FETs by equivalent series resistances (ESR) of the electrolytic capacitors (the resistances due to losses of dielectrics, electrodes and the like). Therefore, the countermeasures that the pattern width of the power supply line is widened, the thermal VIA is further disposed, or the heat is dissipated from the circuit substrate to the case (the heat sink) through the heat conductive material, can be adopted. However, in a case that the heat dissipation in the wiring pattern of the power supply line is exceeded, only the low temperature can be detected in spite of generating the heat from other components of the inverter and then the appropriate overheat protection cannot be performed. Consequently, in order that the moderate heat in the wiring pattern of the power supply line which is the temperature detecting section is generated (the temperature range is not surely higher than the heat resistant temperature of the circuit substrate), in the present invention, an adjustment is performed by using the following methods (1) to (4). [0059] (1) As shown in FIGS. 9A and 9B, the width of the wiring pattern of the power supply line at the portion where the temperature detection device is disposed is narrower than the widths at other portions. In a case that the thickness of the wiring pattern is uniform, when the width of the wiring pattern is narrower, the electrical resistance is larger and the heat generation in the wiring pattern due to the current increases. Since the width of the wiring pattern at the portion where the temperature detection device is disposed is the same as the widths at other portions, the heat generation amount of the temperature detection section is small. Contrarily, as shown in FIG. 9B, the wiring pattern at the portion where the temperature detection device is shaved away in a V-shape from one side surface, the width of the wiring pattern becomes narrower, and the heat generation amount of the temperature detecting section can be larger. The width of the wiring pattern may be uniform and the thickness of the wiring pattern may be thinner, based on the same theory. [0060] (2) The number of the thermal VIAs of the wiring pattern of the power supply line shown in FIG. 6 is reduced, and the heat generation amount of the temperature detecting section can be larger. Contrarily, the number of the thermal VIAs increases, and the heat generation amount of the temperature detecting section can be smaller. [0061] (3) As shown in FIGS. 10A, 10B, 10C and 10D, the heat dissipation amount from the circuit substrate of the wiring pattern to the case is adjusted, and the heat generation amount of the temperature detecting section can be adjusted. That is, in FIG. 10A, since the heat is dissipated to the back surface of the portion where the temperature detection device is disposed through the grease and the heat sink, the heat generation amount can slightly be adjusted. In FIG. 10B, since the heat dissipation material is not disposed on the back surface of the portion where the temperature detection device is disposed, the heat generation amount can largely be adjusted. [0062] (4) In the embodiment of FIG. 10B, as shown in FIGS. 10C and 10D, the width of the wiring pattern may be widened (the first case), or the width of the wiring pattern may be narrowed (the second case). Further, the narrow width in which the above wiring pattern is shaved away may be combined.

[0063] By using the above methods (1) to (4), the heat generation amount of the wiring pattern of the power supply line can adjusted. Thereby, the threshold temperature of the overheat protection can be easily designed, a degree of freedom for designing the threshold of the overheat protection can be improved, and the temperature of the components by which the inverter is constituted can be prevented from becoming higher than the heat resistant temperature of the components.

[0064] FIG. 11 shows an example of arranging the temperature detection device to the circuit board according to the present invention. In the present invention, the temperature detection device is disposed at an edge portion of the circuit board. Conventionally, the temperature detection device is disposed at a center portion of the circuit substrate. The reason is described as follows.

[0065] The heat generation devices are disposed on the circuit substrate of a power section, and the center of the circuit substrate can be a portion where the temperature is highest. By disposing the temperature detection device at the center of the power section, distances from the respective devices to the temperature detection device are averaged, and the temperatures of the respective heat generation devices can be moderately acquired. In other words, the state that the distance from the component device to the temperature detection device is too far and the temperature of the component device cannot be detected is hardly occurred. In the present invention, the portion which is a weakest to the heat in the circuit is intentionally set to the VR pattern (the wiring pattern of the power supply line). If the temperature at the thermal weakest portion is detected, since the temperatures of other devices are equal to or lower than the temperature at the portion which is the weakest to the heat in the circuit, normally, it is enough that the temperature detection is performed on the VR pattern which is not wired at the center of the power section, and it is not required that the temperature detection device is disposed at the center of the substrate of the power circuit section.

[0066] As well, in the above embodiment, the thermistor is exemplified as the temperature sensor. A temperature measuring resistor, a thermocouple, an integrated circuit (IC) temperature sensor in which the temperature characteristic of the transistor is utilized, a quartz thermometer in which a Y-cut crystal is utilized, and the like can be used as the temperature sensor.

[0067] In the embodiment of the present invention, the thermal VIA and the grease are shown for simply dissipating the heat of the system. These are not served for dissipating the heat from the heat generation portion to the temperature detection device.

EXPLANATION OF REFERENCE NUMERALS

[0068] 1 handle (steering wheel) [0069] 2 column shaft (steering shaft, handle shaft) [0070] 10 torque sensor [0071] 12 vehicle speed sensor [0072] 20 motor [0073] 100 control unit (ECU) [0074] 101 current command values calculating section [0075] 104 PI-control section [0076] 105 PWM-control section [0077] 106, 106A inverter [0078] 110 compensation signal generating section [0079] 120, 130 thermistor [0080] 121 heat generation component [0081] 122-1, 122-2, 122-3, 122-4 conductor layer [0082] 123-1, 123-2, 123-3 insulating layer [0083] 140 motor driving control section [0084] 141 overheat protection control section [0085] 142 temperature detecting section [0086] 143 voltage detecting section [0087] 144 voltage-dividing circuit