JP2001339982A - Motor drive unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To materialize a stable motor operation with an inexpensive structure. SOLUTION: A thermistor 9 is located near to one of switching elements of an upper switching group. If the temperature T detected by the thermistor 9 is higher than preliminarily set temperature T1, an energizing rate of switching elements of a lower switching element group becomes lower as the temperature T becomes higher. If the detected temperature T of the thermistor 9 exactly becomes a T2 (>T1), the energizing rate becomes zero stopping the motor M. Thus a PWM control signal is adjustably controlled by a controller 1 by decelerating a rotation speed of a motor M in inverse proportion to the temperature T from a required speed set at the beginning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive for driving a motor by switching a plurality of switching elements constituting a drive unit in accordance with a control signal of a control unit and controlling opening and closing of a current path to a winding of the motor. Related to the device.

[0002]

2. Description of the Related Art Conventionally, a driving device for driving a three-phase DC brushless motor is constructed, for example, as shown in FIG. 4, and is driven by a control signal (not shown) composed of a microcomputer. Bridge inverter IV
Are switched, and the conduction path from the DC power supply E to each winding of the three-phase DC brushless motor M is controlled to be opened and closed by the plurality of switching elements to drive the motor M.

In this three-phase bridge inverter IV, for example, as shown in FIG.
FETs).
A first arm A1 is formed by a series circuit of S1 and S2. Similarly, a second circuit of a second arm is formed by a series circuit of two switching elements S3 and S4 and a series circuit of two switching elements S5 and S6. Third arm A2, A3
Are formed, and flywheel diodes D1 to D6 are connected to the switching elements S1 to S6 respectively with opposite polarities. Note that these flywheel diodes D1
To D6 are switching elements S1 to S
It may be constituted by six parasitic diodes.

The respective arms A1 to A1 of the inverter IV
Connection point P of both switching elements in each of A3
1, P2, and P3 are connected to the star-connected three-phase windings M1, M2, and M3 of the stator of the motor M, respectively.
One end of each of the switching elements S1, S3, S5 of the upper switching element group HT above the connection points P1, P2, P3 is connected to the positive terminal of the DC power supply E, and the inverter IV
The other ends of the switching elements S2, S4, S6 of the lower switching element group LT below the connection points P1, P2, P3 are connected to the negative terminal of the DC power supply E.

A reverse connection prevention element SR composed of an FET is inserted in the current path between the inverter IV and the DC power supply E. When the inverter IV is connected to the DC power supply E in the reverse direction, The reverse connection prevention element SR
Is turned off, and each switching element S of the inverter IV is turned off.
1 to S6 are prevented from being damaged. on the other hand,
In a normal state, the reverse connection prevention element SR is turned on by the control unit, and a current from the DC power supply E is supplied to the switching elements S1 to S6 of the inverter IV and the motor M. still,
PD is a parasitic diode of the reverse connection prevention element SR, and prevents a reverse flow of current to the DC power supply E side when the reverse connection prevention element SR is off. Here, a relay may be used instead of the reverse connection prevention element SR composed of an FET.

In such a configuration, as shown in FIG. 5, the switching elements S1, S3, S5 of the upper switching element group HT are shifted by 120 ° by a control signal shifted by 120 ° from the control unit. 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.

At this time, although not shown in FIG. 4, a position detecting section comprising a Hall element for detecting the position of the rotor of the motor M is provided, and the control section controls each switching element of the upper switching element group HT. A control signal is output so that the switching element of the lower switching element group LT different from the on-switching arm of S1, S3, and S5 is turned on, and the upper switching element group HT to be turned on is output. The combination of the switching element and the switching element of the lower switching element group LT is switched in relation to the detection position of the rotor by the position detection unit. 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.

Normally, a control signal from the control unit to the lower switching element group LT of the inverter IV is subjected to pulse width modulation (PWM), and this PWM
Is controlled to control the speed of the motor M.

[0009]

However, in the above-described conventional configuration, the control unit controls the switching elements S1 to S6 regardless of the temperature of the switching elements S1 to S6.
Since the motor M is rotated at the set speed by controlling S6, the switching elements S1 to S6 including the reverse connection prevention element SR can be operated particularly at a high temperature, so that the current capacity of the switching element S1 to S6 can be controlled with a margin. Since a large FET is selected, there is a problem that the cost is increased and the cost of the entire device is increased.

Accordingly, an object of the present invention is to realize a stable motor operation with an inexpensive configuration.

[0011]

In order to achieve the above-mentioned object, the present invention provides a temperature detecting section for detecting a temperature of the switching element, and a control section, wherein a temperature detected by the temperature detecting section is a predetermined temperature. When the above is the case, the control signal is controlled to reduce the set rotation speed of the motor.

According to such a configuration, when the temperature of the switching element detected by the temperature detecting section is equal to or higher than the predetermined temperature, the control section controls the control signal so as to decrease the set rotation speed of the motor.

[0013] Therefore, heat generation of the switching element can be suppressed, and thermal destruction of the switching element can be prevented beforehand. Further, it is not necessary to select a switching element having a large current capacity as in the prior art, which leads to an increase in cost. Can be prevented.

Further, the invention is characterized in that the temperature detecting section detects the temperature of the switching element having the largest heat generation among the switching elements. According to such a configuration, by detecting the temperature of the switching element that generates the most heat, the condition of heat generation of the switching element that is conditionally strict is detected, and it is necessary to detect the temperatures of all the switching elements. And can be configured at low cost.

Further, in the present invention, the control unit performs control such that the duty ratio of the switching element decreases as the temperature increases with respect to the detected temperature equal to or higher than the predetermined temperature.

According to such a configuration, since heat generation of the switching element can be reliably suppressed, thermal destruction of the switching element can be prevented.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. However, FIG. 1 is a block diagram, and FIGS. 2 and 3 are operation explanatory diagrams.

The motor driving device according to the present embodiment is configured, for example, as shown in FIG. As shown in FIG. 1, a control signal output from the control unit 1 controls six switching elements S1 to S1 including field effect transistors and the like constituting a three-phase bridge inverter 2 as a driving unit.
6 is switched, and the DC power supply 3 is switched to a permanent magnet type 3
The energization path to each winding of the phase DC brushless motor M is controlled to open and close to drive the motor M, and the load L connected to the rotor of the motor M is rotated.

Incidentally, this three-phase bridge inverter 2
Are configured in the same manner as the three-phase bridge inverter IV shown in FIG. 4, and each of the switching elements S1, S3, S5 ( FIG. 4) is 12
They are turned on at 0 ° intervals, and similarly from the 1
Each of the switching elements S2, S constituting the lower switching element group LT is controlled by a control signal shifted in phase by 20 °.
4. S6 (see FIG. 4) is turned on with a shift of 120 °.

At this time, a position detector (not shown) comprising a Hall element for detecting the position of the rotor of the motor M is provided, and each of the arms A1 to A of the upper switching element group HT is provided.
The control unit 1 outputs a control signal so that the switching element of the lower switching element group LT different from the arm of the switching element that is on among the switching elements S1, S3, and S5 of the third switching element is on, and The combination of 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 is switched in relation to the position of the rotor of the motor M detected by the position detector.

A PWM control signal is output from the control section 1 to the lower switching element group LT of the inverter 2, and the duty cycle of the PWM is controlled to control the current of the motor M. In this way, the direction of current flow to each of the windings M1 to M3 of the motor M is switched, and the magnetic poles of the stator rotate in one direction, thereby obtaining the rotational force of the rotor.

At this time, the control unit 1 controls the switching elements S2 and S of the lower switching element group LT so that the motor M rotates at the rotation speed set by the speed setting unit 4.
4. A PWM control signal is output to S6, and the rotation speed of the motor M is maintained at the set speed.

A reverse connection preventing element 6 composed of an FET is inserted in the current path between the inverter 2 and the DC power supply 3 as in the case of FIG. When the connection is made in the direction, the reverse connection prevention element 6 is turned off by the control unit 1 and the switching elements S1 to S6 of the inverter 2 are prevented from being damaged. On the other hand, in a normal state, the reverse connection prevention element 6 is turned on by the control unit 1 and each switching element S of the inverter 2 is turned on.
A current from the DC power supply 3 is supplied to 1 to S6 and the motor M. Reference numeral 7 denotes a parasitic diode of the reverse connection prevention element 6, which prevents a reverse current from flowing to the DC power supply 3 when the reverse connection prevention element 6 is turned off.

Further, a thermistor 9 is provided as a temperature detector for detecting the temperature of each of the switching elements S1 to S6 constituting the inverter 2. This thermistor 9 is used for a specific application among the switching elements S1 to S6. In the motor to be used, it is arranged close to the one that generates the most heat.

In this case, the switching elements S1, S3, S5 of the upper switching element group HT are compared with the switching elements S2, S4, S6 and the reverse connection preventing element 6 of the lower switching element group LT under PWM control. Since the heat is easily generated, it is desirable to dispose the thermistor 9 close to any one of the switching elements S1, S3, and S5 of the upper switching element group HT.

When the detected temperature T of the thermistor 9 is equal to or higher than a predetermined temperature, the controller 1 controls the energization of the switching elements S2, S4, S6 of the lower switching element group LT as the temperature T increases. The duty of the PWM control signal is variably controlled so as to reduce the rate.

That is, if the detected temperature T of the thermistor 9 is equal to or higher than the predetermined temperature T1, as shown in FIG. 2, the switching elements S2, S4, S6 of the lower switching element group LT increase as the temperature T increases. Of the PWM control signal from the control unit 1 so that the duty ratio becomes zero and the motor M stops when the temperature T detected by the thermistor 9 becomes T2 (> T1). Is variably controlled, and the rotation speed of the motor M is gradually reduced from the initial set speed Vr as the temperature T increases.

When the motor M is decelerated at a low speed when the motor M is decelerated as the temperature T rises, as shown in FIG. 3, the detected temperature T of the thermistor 9 becomes T2 (> T1). At this time, the motor M may be stopped by forcibly setting the duty ratio of the switching elements S2, S4, and S6 of the lower switching element group LT to zero.

Therefore, according to the above-described embodiment, heat generation of the switching elements S1 to S6 of the inverter 2 can be suppressed, and thermal destruction of the switching elements S1 to S6 can be prevented. Further, since it is not necessary to select a switching element having a large current capacity as the switching elements S1 to S6, it is possible to prevent an increase in cost.

Further, by detecting the temperature of the switching element having the largest heat generation among the switching elements S1, S3, S5 of the upper switching element group HT having the largest heat generation, the heat generation condition of the switching element having the most severe condition can be determined. As a result, it is not necessary to detect the temperatures of all the switching elements, and the configuration can be made at low cost.

In the above-described embodiment, the case where the present invention is applied to the driving of the three-phase DC brushless motor M which is driven to rotate is described. However, the present invention is applicable to a three-phase DC brushless motor which is driven linearly. Can be applied in the same manner, and the same effect as in the above-described embodiment can be obtained.

Further, the detection of the temperatures of the switching elements S1 to S6 is not limited to the above-described configuration using the thermistor 9 and other temperature detecting elements. Focusing on the fact that the forward voltage of the parasitic diodes of S1 to S6 or the full-wheel diodes connected in parallel to each of the switching elements S1 to S6 decreases, the temperature detection unit is configured to detect the forward voltages of these diodes. It may be configured.

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.

[0034]

As described above, according to the first aspect of the present invention, when the temperature of the switching element detected by the temperature detecting section is equal to or higher than the predetermined temperature, the control section causes the control section to set the rotational speed of the motor. Since the control signal is controlled to reduce the switching power, the heat generation of the switching element can be suppressed, and the thermal destruction of the switching element can be prevented.

Further, since it is not necessary to select a switching element having a large current capacity as in the prior art,
An increase in cost can be prevented, and a stable motor operation can be realized with an inexpensive configuration.

According to the second aspect of the present invention, by detecting the temperature of the switching element that generates the most heat in the motor used for a specific application, the condition of the most severe switching element can be determined. It is possible to detect the temperature, and it is not necessary to detect the temperatures of all the switching elements.

Further, according to the third aspect of the present invention, since heat generation of the switching element can be reliably suppressed, it is possible to prevent thermal destruction of the switching element.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of one embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of one embodiment of the present invention.

FIG. 4 is a connection diagram of a conventional example.

FIG. 5 is a timing chart for explaining the operation of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control part 2 Inverter (drive part) S1-S6 Switching element 3 DC power supply 9 Thermistor (Temperature detection part) M Three-phase DC brushless motor

Claims (3)

[Claims] 1. A motor drive device for switching a plurality of switching elements constituting a drive unit in accordance with a control signal of a control unit, controlling opening and closing of a current path to a winding of the motor to drive the motor, A temperature detection unit that detects a temperature of the element; and the control unit controls the control signal to reduce a set rotation number of the motor when a temperature detected by the temperature detection unit is equal to or higher than a predetermined temperature. Motor drive device. 2. The motor driving device according to claim 1, wherein the temperature detecting section detects a temperature of the switching element having the largest heat generation among the switching elements. 3. The control unit according to claim 1, wherein the control unit controls the detected temperature equal to or higher than the predetermined temperature so that the duty ratio of the switching element decreases as the temperature increases. The motor drive device according to claim 1.