JP2001136771A - Drive device for motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent demagnetization at low temperature of a magnet in a permanent magnet-type brushless motor. SOLUTION: A thermistor TM is installed at an inverter IV. The temperature of switching elements S1 to S6, which are nearly proportional to the temperature of a permanent magnet-type three-phase DC brushless motor M, are detected. The detected temperatures are input to a control part CO. Whether the switching elements S1 to S6 are at a prescribed temperature or lever, generating the demagnetization at a low temperature of a magnet is determined by the control part CO. A resistance R4, whose resistance value is higher than that of a resistance R1 and that of a resistance R2, is installed. Both its ends are connected to the connecting point of the two voltage-dividing resistances R1, R2 and to the changeover signal output terminal PO of the control part CO. When a temperature which is a detected by the thermistor TM is at the prescribed temperature or lower, a changeover signal at a level L is output from the changeover-signal output terminal PO of the control part CO, and a reference value to the inversion input terminal of a computer CP is changed over to be low, as compared to the case in which the detected temperature is higher than the prescribed temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor for controlling the switching of a plurality of switching elements constituting a drive unit in accordance with a control signal of a control unit, and controlling the opening and closing of a current path to a winding of a permanent magnet type brushless motor. And a control signal from the control unit to the switching element to limit the current value detected by the current detection unit to a predetermined cut-off current value or less by the current limit unit by detecting the current flowing through the drive unit by the current detection unit. The present invention relates to a motor driving device for shutting off a motor.

[0002]

2. Description of the Related Art Conventionally, a control circuit of a power steering apparatus for a vehicle using a permanent magnet type three-phase DC brushless motor is configured as shown in FIG. 3, for example.

That is, as shown in FIG. 3, a steering wheel (not shown) is provided with a detector 1 comprising a rotary encoder or the like for detecting a steering angle, and an output signal of the detector 1 is supplied to a control unit comprising a microcomputer. When input to 2,
The control unit 2 detects the steering operation speed based on the output signal of the detector 1, and the control unit 2 determines the assist amount of the steering operation torque according to whether the speed is high or low. Depending on the control signal
A plurality of switching elements constituting a three-phase bridge inverter 3 as a driving unit are switched, and a DC power supply 4
A plurality of switching elements control opening and closing of a current path to each winding of the permanent magnet type three-phase DC brushless motor M, thereby driving the motor M and generating a necessary assist torque.

The three-phase bridge inverter 3 is generally constructed as shown in FIG. 4, in which a first arm A1 is formed by a series circuit of two switching elements S1 and S2 composed of a field effect transistor and the like. Similarly, a second arm A2 is formed by a series circuit of two switching elements S3 and S4, and a third arm A3 is formed by a series circuit of two switching elements S5 and S6. Each of the switching elements S1 to S6 has The flywheel diodes D1 to D6 are respectively connected to opposite polarities.

The respective arms A1 to A of the inverter 3
3 respectively, a connection point P1 of both switching elements,
The star-connected three-phase windings M1, M2, M3 of the stator of the motor M are connected to P2, P3, and each of the upper switching elements HT above the connection points P1, P2, P3 of the inverter IV. One end of each of the switching elements S1, S3, S5 is connected to the positive terminal of the DC power supply 4, and each of the switching elements S2, S4, S6 of the lower switching element group LT below the connection points P1, P2, P3 of the inverter 3. Is connected to the negative terminal of the DC power supply 4.

In such a configuration, as shown in FIG. 5, each of the switching elements S1, S3, S5 of the upper switching element group HT is shifted by 120 ° by a control signal having a phase shift of 120 ° from the control unit 2. Similarly, the switching elements S2, S4, S6 of the lower switching element group LT are turned on by 120 ° by a control signal having a phase shifted by 120 ° from the control unit 2 similarly.

At this time, in the control unit 2, the switching elements of the lower switching element group LT different from the ON switching arm of the switching elements S1, S3, S5 of the upper switching element group HT are used. A control signal is output so as to be turned on, and a combination of a switching element of the upper switching element group HT and a switching element of the lower switching element group LT to be turned on is determined by a rotation detector (not shown) composed of a Hall element. The switching is performed in relation to the detected position of the rotor of the motor M. Thus, each winding M1 to M3
The direction of current flow to the stator is switched, and the magnetic poles of the stator rotate in one direction, thereby obtaining the rotational force of the rotor.

As shown in FIG. 3, in order to prevent and protect the switching elements S1 to S6 of the inverter 3 from overcurrent, each of the switching elements S1 to S6 is protected.
A current limiter 6 is provided to limit the current flowing through the current limiter 6 to a predetermined cutoff current value or less.

As shown in FIG. 3, the current limiting section 6
It comprises an amplifier 61 for amplifying the voltage between both ends of the shunt resistor 7 as a current detecting section, a comparator 62, and a cutoff section 63 including a gate and the like.

As shown in FIG. 3, a shunt resistor 7 is provided in a negative current path from the DC power supply 4 to the inverter 3, and a current flowing through the inverter 3 is detected by the shunt resistor 7. The voltage at both ends is amplified by the amplifier 61, the output of the amplifier 61 is input to the non-inverting input terminal of the comparator 62, and two voltage dividing resistors provided in series between a positive power supply (not shown) and the ground. 64, 65
Is input to the inverting input terminal of the comparator 62 as a reference value, and the comparator 62 compares the potentials of both input terminals.

As shown in FIG. 3, each switching element S1 is provided between the control unit 2 and the inverter 3.
To the interrupting section 63 for passing and interrupting the control signal to S6
The output signal of the comparator 62 is input, the current flowing through the shunt resistor 7 exceeds a predetermined cutoff current value, and the output potential of the amplifier 61 on the non-inverting input terminal side of the comparator 62 exceeds the reference value on the inverting input terminal side. For example, the output of the comparator 62 changes from a low level (hereinafter, referred to as L) to a high level (hereinafter, referred to as H).
As a result, the closing condition of the gate of the cut-off section 63 is satisfied, and the control signal to each of the switching elements S2, S4, S6 of the lower switching element group LT of the inverter 3, for example, is cut off. I have.

Thus, the lower switching element group LT
The control signal to each of the switching elements S2, S4, and S6 is cut off, so that the current flowing through the inverter 3 is limited to a predetermined cutoff current value or less, and the switching elements S1 to S6 are protected from damage due to overcurrent. At the same time, the demagnetization of the motor M due to the overcurrent is prevented.

By the way, the operating environment of a vehicle varies from -40.degree. C. to + 120.degree. C. only in terms of temperature. Although it is necessary to be able to cope with the possible environmental temperature, in the permanent magnet type brushless motor M, the magnet tends to be demagnetized at a predetermined temperature or less, and there is a possibility that a disadvantage that torque cannot be generated may occur. .

[0014]

However, in the above-described conventional configuration, the reference value on the inverting input terminal side as a comparison reference in the comparator 62 is independent of the temperature of the motor M, strictly speaking, regardless of the temperature of the magnet. Since it is constant, when the temperature in the use environment is lower than a predetermined temperature, such as in a cold region,
If a high current such that the current limiter 6 operates to obtain a high torque is passed, the low-temperature demagnetization described above occurs in the motor M, and the necessary torque cannot be obtained.
There is a problem that it becomes impossible to generate a sufficient assist torque.

Further, in consideration of the variation in the resistance value of the shunt resistor 7 and the temperature dependency, and the variation in the offset of the operational amplifiers constituting the amplifier 61 and the comparator 62, the comparison is usually made so as not to cause a torque shortage. Since the reference value of the motor 62 is set higher than the ideal value, the above-described low temperature demagnetization of the motor M is likely to occur.

An object of the present invention is to prevent a magnet from being demagnetized at a low temperature in a permanent magnet type brushless motor.

[0017]

In order to solve the above-mentioned problems, the present invention provides a temperature detecting unit for detecting a temperature of the switching element or the motor, and a detecting unit which detects a temperature of the switching element or the motor when the temperature is lower than a predetermined temperature. In some cases, a switching unit that switches the cutoff current value when the control signal is cut off by the current limiting unit to be lower than when the detected temperature is higher than the predetermined temperature is provided.

According to such a configuration, if the temperature detected by the temperature detecting unit is equal to or lower than the predetermined temperature, the switching unit switches the cutoff current value when the control signal is cut off to be lower than when the control signal is higher than the predetermined temperature. Therefore, the low temperature demagnetization of the conventional motor can be prevented.

Further, since the low-temperature demagnetization can be prevented in this way, even when the temperature in the use environment is lower than a predetermined temperature, such as in a cold region, a decrease in generated torque can be prevented.

At this time, it is desirable to use a thermistor for the temperature detector for detecting the temperature of the switching element, and the temperature of the switching element which is substantially proportional to the temperature of the motor winding by the thermistor, preferably the temperature of the motor winding,
Most preferably, the temperature of the magnet is detected.

Further, in the present invention, when the temperature detected by the temperature detecting means is equal to or lower than a predetermined temperature, the switching unit sets the cut-off current value when the control signal is cut off by the current limiting unit. It is characterized in that it is switched in several stages according to the detected temperature at that time.

According to such a configuration, the cutoff current value is switched in several steps in accordance with the relationship between the temperature at which low-temperature demagnetization occurs and the motor current, so that a more accurate motor current limit control can be performed. it can.

Also, in the present invention, a setting section for setting the cutoff current value is provided, and the current limiting section compares the detected current value by the current detection section with a value set by the setting section. The switching unit switches the value set by the setting unit.

According to such a configuration, the value itself set by the setting unit is switched so as to be a comparison reference in the comparator, so that the cutoff current value when the control signal is cut off by the current limiting unit can be easily and reliably set. Switching can be performed, and low-temperature demagnetization can be prevented.

Further, in the present invention, an amplifier for amplifying the output of the current detection unit is provided, and the switching unit switches the gain of the amplifier to change the current value detected by the current detection unit, thereby cutting off the interruption. It is characterized by switching the current value.

According to such a configuration, since the cutoff current value is switched by changing the current value detected by the current detection section by switching the gain of the amplifier, the cutoff when the control signal is cut off by the current limit section is changed. The current value can be easily and reliably switched, and low-temperature demagnetization can be prevented.

[0027] In the present invention, the motor may include a plurality of the windings, and the driving unit may include an arm formed by connecting the two switching elements in series, the number of which is equal to the number of the windings. A first switching element group on one side of the connection point of the inverter and a second switching element on the other side, each of the windings being connected to a connection point between the two switching elements in each arm; Control the group, and by turning on one of the switching elements of the one-side switching element group and turning on the switching elements of the other-side switching element group on an arm different from the arm of the switching element, The switching element of the one-side switching element group to be turned on while the current flows and the other-side switch Switching the combination of the switching element group and the switching element in relation to the position of the rotor of the motor detected by the detection means, thereby switching the direction of current flow to each winding to rotate the rotor. The current limiting unit cuts off a control signal from the control unit to any one of the one-side switching element group and the other-side switching element group. .

According to such a configuration, the current flowing through each switching element of the drive unit can be suppressed to a predetermined cut-off current value or less, so that protection of each switching element and prevention of demagnetization due to overcurrent can be achieved. Will be possible.

Further, in the present invention, the temperature detector detects a temperature of a permanent magnet of the motor. According to such a configuration, low-temperature demagnetization of the motor can be more reliably and accurately prevented.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a motor driving device according to the present invention is applied to a vehicle power steering will be described with reference to FIGS. However,
FIG. 1 is a connection diagram of a motor driving device according to an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the operation.

A motor driving device applied to a power steering for a vehicle such as an automobile is configured as shown in FIG. 1, for example. A detector SD including a rotary encoder or the like is provided on a steering wheel (not shown). From this detector SD, a two-phase pulse signal having a 90 ° phase shift is output as a detection signal to a subsequent signal conversion unit WS. The waveform of the detection signal is shaped by the conversion unit WS.

When the waveform-shaped detection signal is input to a control unit CO comprising a microcomputer (hereinafter simply referred to as a microcomputer), the control unit CO controls the steering angular velocity, that is, the steering operation speed based on the detection signal. Is detected, and the control unit CO determines the assist amount of the steering operation torque according to the high / low of the steering angular velocity.

Further, in order to generate the determined assist torque, a plurality of switching elements constituting a three-phase bridge inverter IV as a drive unit are switched by a control signal output from the control unit CO. The energization path to each winding of the permanent magnet type three-phase DC brushless motor M is controlled to be opened and closed by a plurality of switching elements to drive the motor M and generate a necessary assist torque.

The three-phase bridge inverter IV for driving the permanent magnet type three-phase DC brushless motor M
Has, for example, a configuration similar to that of the inverter 3 shown in FIG. 4, and each of the switching elements S1, S3, S5 of the upper switching element group HT (FIG. Are turned on by 120 ° each (see FIG. 5), and similarly, the control signals from the control unit CO are shifted in phase by 120 °, so that each of the switching elements S2, S4,
S6 (see FIG. 4) is turned on with a shift of 120 ° (see FIG. 5).
reference).

Here, the control unit CO controls the switching element S of each of the arms A1 to A3 of the upper switching element group HT.
1, the lower switching element group LT of an arm different from the ON of the switching element arm among S3 and S5
A control signal is output so that the switching element of the upper switching element group HT and the switching element of the lower switching element group LT to be turned on are combined with the switching element of the lower switching element group LT. (Not shown) is switched in relation to the position of the rotor of the motor M detected. Note that a PWM control signal is output from the control unit CO to the lower switching element group LT of the inverter IV, and the duty cycle in the PWM is controlled to control the current of the motor M.

Further, as shown in FIG.
In order to prevent and protect an overcurrent from flowing through each of the switching elements S1 to S6,
There is provided a current limiting unit CR for limiting the current flowing in S6 to a predetermined cutoff current value or less.

As shown in FIG. 1, the current limiting section CR includes an amplifier A for amplifying a voltage between both ends of a shunt resistor SH as a current detecting section, a comparator CP, a D-flip-flop DF, and three It is composed of AND gates AG1 to AG3.

As shown in FIG. 1, the shunt resistance SH is
The shunt resistor SH is provided on the negative current path from the DC power supply E to the inverter IV.
The current flowing through V is detected, the voltage across the shunt resistor SH is amplified by the amplifier A, the output of the amplifier A is input to the non-inverting input terminal of the comparator CP, and a positive power supply (not shown)
Two voltage-dividing resistors R provided in series between
The potential of the connection point of R1 and R2 is input as a reference value to the inverting input terminal of the comparator CP, and the potential of both input terminals is compared by the comparator CP.

As shown in FIG. 1, the input terminal D of the D-flip-flop DF is connected to a positive power supply (not shown), and the clock terminal CK is connected to, for example, 16
kHz clock pulse is input and the pull-up resistor R
The output signal of the comparator CP is input to a reset terminal R connected to a positive power supply (not shown) via the terminal 3.

Further, one input terminal of each of the AND gates AG1 to AG3 is connected to an output terminal of a control signal from the control unit CO to each of the switching elements S2, S4, S6 of the lower switching element group LT, and to the other. The input terminal is connected to the Q output terminal of the D-flip-flop DF, and only when the AND condition of both inputs of each of the AND gates AG1 to AG3 is satisfied, the AND gates AG1 to AG3 output the lower switching element group LT. Each switching element S
When a control signal is output to 2, S4, and S6 and the AND condition is not satisfied, the control signal from the control unit CO to each of the switching elements S2, S4, and S6 is cut off.

Therefore, the current flowing through the shunt resistor SH exceeds the predetermined cutoff current value, and the amplifier A on the non-inverting input terminal side
Is higher than the reference value on the inverting input terminal side, the output of the comparator CP is inverted from a low level (hereinafter, referred to as L) to a high level (hereinafter, referred to as H), and as described above, each of the AND gates AG1 AND3 both inputs AND
When the condition is not satisfied, each of the AND gates AG1 to AG3
, The control signal to each of the switching elements S2, S4, S6 of the lower switching element group LT is cut off, and the current flowing through the shunt resistor SH is cut off.

At this time, in the inverter IV, a circulating current flows through the winding of the motor M via the on-state switching element of the upper switching element group LT and the flywheel diode, and the D-flip-flop is not turned on until the circulating current disappears. Control unit CO to clock terminal CK of
The AND condition of both inputs of each of the AND gates AG1 to AG3 is satisfied at the output timing of the clock pulse from the first and second switching elements S2, S4, S of the lower switching element group LT via the AND gates AG1 to AG3.
6, the control signal is output, and the current starts to flow again through the shunt resistor SH, and the current flowing through each of the windings M1 to M3 of the motor M recovers.

As described above, the lower switching element group LT
By repeatedly supplying and interrupting the control signal to each of the switching elements S2, S4, and S6, the current flowing through the inverter IV is intermittently limited to a predetermined interrupting current value or less. While being protected from damage, demagnetization of the motor M due to overcurrent is prevented.

The clock pulse from the control unit CO to the clock terminal CK of the D-flip-flop DF is not limited to 16 kHz as described above. Any frequency can be used so long as the current flowing through the device can be recovered.

By the way, as shown in FIG. 1, the inverter IV is provided with a thermistor TM as a temperature detecting section.
The thermistor TM detects the temperatures of the switching elements S1 to S6 which are substantially proportional to the winding temperature of the motor M,
The temperature detected by the thermistor TM is input to the control unit CO, and the control unit CO determines whether the detected temperature is equal to or lower than a predetermined temperature Ts at which the low temperature demagnetization of the motor M occurs.

As shown in FIG. 1, the resistors R1 and R2
A resistor R4 having a higher resistance value is provided, and both ends thereof are connected to a connection point of two voltage dividing resistors R1 and R2 functioning as a setting unit and a switching signal output terminal PO of the control unit CO,
When the temperature detected by the thermistor TM is equal to or lower than the predetermined temperature Ts, a switching signal of L is output from the switching signal output terminal PO of the control unit CO, and the reference value of the inverting input terminal of the comparator CP is lower than the predetermined temperature. Switching is performed so as to be lower than a value in a high normal state. Here, the switching signal output terminal PO and the resistor R4 of the control unit CO correspond to a switching unit.

Therefore, as shown in FIG.
If the detected temperature of M is equal to or lower than the predetermined temperature Ts at which low-temperature demagnetization occurs, a switching signal of L is output from the switching signal output terminal PO of the control unit CO, and the voltage is set by the voltage dividing resistance of the resistors R1 and R2. The reference value on the inverting input terminal side of the comparator CP is
The value is switched to a low value set by the voltage dividing resistance of the resistance R1 and the combined resistance of R2 and R4.

For this reason, as shown in FIG.
Is higher than the predetermined temperature Ts, the threshold value Vth of the input potential Vi on the side of the non-inverting input terminal when the output of the control unit CO is inverted to H is lower than that of the control unit CO. From the lower switching element L
When the control signal to the switching elements S2, S4, S6 of T is cut off, the cut-off current value flowing through the inverter IV is switched to a low value, and the low-temperature demagnetization of the motor M is prevented.

At this time, as shown in FIG. 2, the maximum torque of the motor M gradually decreases in proportion to the rise in the temperature detected by the thermistor TM. Since the magnetic flux density of the magnet of the motor M increases as the temperature decreases, the minimum value of the maximum torque of the motor M is determined by the detection temperature of the thermistor TM at a predetermined temperature Ts.
This is the same as in the case of higher temperature, the minimum value of the maximum torque at the time of low temperature does not fall below the minimum value at the time of high temperature, and there is no problem even if the switching current value is switched in this way.

On the other hand, as shown in FIG.
Is higher than the predetermined temperature Ts, the switching signal output terminal PO of the control unit CO is in a high impedance state, and the reference value on the inverting input terminal side of the comparator CP is equal to the value of the resistors R1 and R2. Set by the piezoresistor, the comparator CP
Of the input potential Vi on the side of the non-inverting input terminal when the output is inverted to H is not switched.

As described above, according to the above-described embodiment,
If the temperature detected by the thermistor TM is equal to or lower than the predetermined temperature Ts, the cutoff current value when the control signal is cut off is switched lower than when the control signal is higher than the predetermined temperature Ts. This can be prevented beforehand, and even when the temperature in the use environment is lower than or equal to a predetermined temperature, such as in a cold region, a reduction in the generated assist torque can be prevented.

Further, since the reference value itself on the inverting input terminal side, which is used as a reference for comparison in the comparator CP, is switched, the cutoff current value can be easily and reliably switched, and low temperature demagnetization of the motor M is prevented. be able to.

In the above-described embodiment, the thermistor TM is used as the temperature detecting section. However, the temperature detecting section is not limited to the thermistor, but can detect the temperatures of the switching elements S1 to S6. I just need.

At this time, the temperature of the motor M detected by the temperature detecting section is determined by the switching elements S1 to S1 as described above.
Instead of detecting the temperature of S6, a thermistor may be embedded in the windings M1 to M3 of the motor M to detect the temperature of the windings M1 to M3. Most preferably, the temperature of the permanent magnet of the motor M is detected. Is good. In this way, the low-temperature demagnetization of the motor M can be more reliably and accurately prevented.

Further, in the above embodiment, the comparator CP
Has been described in which the reference value is switched between large and small according to the temperature of the switching elements S1 to S6.
The temperature detected by the switching elements S1 to S6 is equal to a predetermined temperature Ts.
In the following cases, the cutoff current value when the control signal is cut off may be switched between two or more steps in accordance with the detected temperature at that time. In this case, the current limit control of the motor M is set to a higher level. It is possible to perform with accuracy.

In the above embodiment, the comparator CP
The switching current value is switched by switching the reference value on the inverting input terminal side, which is the comparison reference in
May be switched. In this case, by switching the gain of the amplifier A, the shunt resistor S
The cutoff current value can be switched by changing the current value detected by H, and low-temperature demagnetization can be prevented.

In the above-described embodiment, the case where the control signal to the switching elements S2, S4 and S6 of the lower switching element group LT is intermittently controlled by the current limiter CR has been described. The control signals to the HT switching elements S1, S3, S5 may be intermittent.

In the above embodiment, the control unit CO, the comparator CP, the D-flip-flop DF, the AND
The gates AG1 to AG3 and the resistors R1 to R4 may be implemented by a microcomputer.

Further, in the above embodiment, the case where the present invention is applied to a power steering for a vehicle such as an automobile is described. However, the scope of the present invention is not limited to such a power steering. In addition, the present invention can be applied to any motor having a function of driving a motor and limiting its current.

The motor to which the present invention can be applied may be a permanent magnet type brushless motor, and it is needless to say that the present invention is not limited to the three phases described above.

The present invention is not limited to the above-described embodiment, and various changes other than those described above can be made without departing from the gist of the present invention.

[0062]

As described above, according to the first aspect of the present invention, if the temperature detected by the temperature detecting unit is equal to or lower than the predetermined temperature, the switching unit changes the cutoff current value when the control signal is cut off. Since the temperature can be switched lower than when the temperature is higher than the predetermined temperature, low temperature demagnetization of the motor can be prevented beforehand, and when applied to power steering for a vehicle, the temperature in the usage environment such as a cold region becomes the predetermined temperature. Even in the following cases, the necessary assist torque can be obtained, and power steering with excellent reliability can be realized.

According to the second aspect of the present invention, the cutoff current value is switched in several steps in accordance with the relationship between the temperature at which low-temperature demagnetization occurs and the motor current, so that a more accurate motor current limit is achieved. Control can be performed.

According to the third aspect of the present invention, since the value itself set by the setting unit is switched so as to be a comparison reference in the comparator, the cutoff current value when the control signal is cut off by the cutoff unit is set. Switching can be performed easily and reliably, and low-temperature demagnetization of the motor can be prevented.

According to the fourth aspect of the present invention, the control signal is cut off by the cut-off section because the gain of the amplifier is changed to change the cut-off current value by changing the current value detected by the current detecting section. In this case, the cutoff current value can be easily and reliably switched, and low temperature demagnetization of the motor can be prevented.

According to the fifth aspect of the present invention, the current flowing through each switching element of the drive unit can be suppressed to a predetermined cut-off current value or less. Demagnetization can be prevented.

According to the sixth aspect of the present invention, low-temperature demagnetization of the motor can be prevented more reliably and accurately.

[Brief description of the drawings]

FIG. 1 is a connection diagram of an embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the embodiment of the present invention.

FIG. 3 is a connection diagram of a motor drive device as a background of the present invention.

FIG. 4 is a detailed connection diagram of a part of FIG. 3;

FIG. 5 is a timing chart for explaining the operation of FIG. 4;

[Explanation of symbols]

 E DC power supply M Permanent magnet type three-phase DC brushless motor M1 to M3 Winding CO Control unit IV Three-phase bridge inverter (Drive unit) SH Shunt resistor (Current detection unit) CR Current limiting unit A Amplifier CP Comparator DF D- Flip-flops AG1 to AG3 AND gates R1, R2 Resistance (setting unit) R4 Resistance (switching unit) PO Switching signal output terminal (switching unit) S1 to S6 Switching elements A1 to A3 Arm

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenichi Tokuno 248 Nakajuku, Aichigawa-machi, Aichi-gun, Aichi-gun, Shiga F-term in Nidec Corporation Shiga Technology Development Center (reference) 5H007 AA06 AA17 BB06 CB05 CC23 DB07 DC02 DC08 FA03 FA13 5H560 AA08 BB04 BB12 DA02 DA07 DC05 DC12 EB01 GG04 JJ19 SS01 TT04 TT07 TT15 UA10 XA12 5H611 AA01 BB01 BB07 PP05 QQ04

Claims (6)

[Claims] A control signal from a control unit switches a plurality of switching elements constituting a drive unit, and controls the opening and closing of a current path to a winding of a permanent magnet type brushless motor to drive the motor, A current detecting unit detects a current flowing through the driving unit, and a current limiting unit sends a control signal from the control unit to the switching element so as to limit a current value detected by the current detecting unit to a predetermined cutoff current value or less. In the driving device for a motor to be cut off, a temperature detection unit that detects a temperature of the switching element or the motor; and when the temperature detected by the temperature detection unit is equal to or lower than a predetermined temperature, the control signal is cut off by the current limiting unit. A switching unit that switches the cutoff current value at a time lower than when the detected temperature is higher than the predetermined temperature. Drive apparatus for a motor according to claim. 2. The switching unit according to claim 1, wherein when the temperature detected by said temperature detecting unit is equal to or lower than a predetermined temperature, said switching current value when said control signal is cut off by said current limiting unit is detected. The motor driving device according to claim 1, wherein the switching is performed in several stages in accordance with the following. A setting unit for setting the cutoff current value, wherein the current limiting unit includes a comparator for comparing the detected current value by the current detection unit with a value set by the setting unit; 3. The switching unit according to claim 1, wherein the switching unit switches a value set by the setting unit.
A driving device for a motor according to claim 1. 4. An amplifier for amplifying an output of the current detection unit, wherein the switching unit switches the cutoff current value by switching a gain of the amplifier to change a current value detected by the current detection unit. 2. The method according to claim 1, wherein
Or a drive device for a motor according to 2. 5. The motor according to claim 1, wherein the motor includes a plurality of windings, and the driving unit includes a bridge inverter including the same number of arms as the number of windings, the arm including two switching elements connected in series. Connecting each of the windings to a connection point of the two switching elements in each of the arms to control a one-side switching element group on one side of the connection point of the inverter and a second-side switching element group on the other side. By turning on one of the switching elements of the one-side switching element group and turning on the switching elements of the other-side switching element group on an arm different from the arm of the switching element, a current flows through the winding. And the switching element of the one-side switching element group and the switching element of the other-side switching element group to be turned on. Combination with the switching element
Switching the direction of current flow to each winding by switching in relation to the position of the rotor of the motor detected by the detection means to obtain the rotational force of the rotor; The motor according to any one of claims 1 to 4, wherein the control unit cuts off a control signal from the control unit to one of the one of the one-side switching element group and the other-side switching element group. Drive. 6. The motor according to claim 1, wherein the temperature detector detects a temperature of a permanent magnet of the motor.
A driving device for a motor according to any one of the above.