JP2002095287A - Motor driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor driver where the voltage applied on a motor is not affected by the voltage drop generated in a lead wire, when the lead wire from the motor to earth becomes long or the motor current becomes large. SOLUTION: This motor driver is equipped with a motor 2 connected between a DC power source 12 and earth, a switching element 8 for driving the motor 2, and a CPU 7 for controlling this switching element 8. The CPU 7 detects the voltage d of voltage drop generated in the lead wire between the switching element 8 and the earth, and outputs the specified voltage to make the sum of the voltage Vd of voltage drop and the voltage VS generated across the switching element 8 constant to the control terminal of the switching element 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor driving device, and more particularly to a fan motor driving device for a vehicle air conditioner.

[0002]

2. Description of the Related Art FIGS. 5 and 6 show a drive circuit 50 of a fan motor of a vehicle-mounted air conditioner as a prior art and an external appearance of an air conditioner unit which is a part of the vehicle-mounted air conditioner.

In a drive circuit 50 shown in FIG. 5, a voltage of a DC power supply 73 is applied to an input terminal 51, and a voltage is divided at each tap terminal 53 of a variable resistor 52 having a tap terminal. The divided voltage is drawn out by the moving slider 56. The slider 56 is rotated by a knob 63 rotatably provided on a panel 69 of the air conditioner unit 62 shown in FIG. 54 and 55 are applied to the positive terminal side. The negative terminals of the two motors 54, 55 are grounded to the vehicle body via a lead wire having a transistor 57 as a switching element and a resistor 58. Motor 54,
Since the current i flowing through the transistor 55 is as large as 4 to 50 A, an npn-type power transistor is used as the transistor 57 as a switching element.

As shown in FIG. 6, the air conditioner unit rotates the index 65 of the knob 63 for fan output to match the index 64 indicating the output of the fan on the panel 69, so that the passenger can enjoy a comfortable fan output. I'm trying to get
The knob 66 of the air conditioner unit 62 rotates the flap of the air duct to send a comfortable temperature wind to the passenger. 67 is an input switch for causing air to circulate in the vehicle interior, and 68 is an input switch for the defroster.

When the fan switch 59 is turned on, the base potential of the transistor 57 is increased by the pull-up resistor 60, the transistor 57 as a switching element is turned on, and the motor current i flows through the motors 54 and 55. Note that the resistor 61 is a protection resistor. Also, two DC motors 5
One of the fans 4 and 55 is a passenger seat side fan motor, and the other is a driver seat side fan motor. Since both motors 54 and 55 are connected in parallel, they are driven by the same voltage.

[0006]

In the case of such a motor drive circuit, when the length of the lead wire (resistor 58) is increased due to wiring in the vehicle cabin or the like, the voltage drop generated in the lead wire is reduced by the motor current i. Since the product is the product of the resistance value of the lead wire (resistance 58), even if the motor current i is not so large, if the resistance value of the resistance 58 is large, it cannot be ignored. If this voltage drop is large, the motor 5
A voltage smaller than a voltage that should be applied to both ends of the motors 54 and 55 is applied to both ends of the motors 54 and 55.

When the DC voltage applied to the motors 54 and 55 increases, the current i flowing to the ground through the motors 54 and 55 increases. In this case, even if the resistance value of the lead wire (resistor 58) is not so large, the voltage drop generated in the lead wire connected between the motors 54, 55 and the ground increases, and the motor 54, 55 The voltage applied to both ends is different from the preset voltage value. Motor current i
This effect is particularly large when the length of the lead wire is long due to the large size.

In such a state, the fan motor output based on the rotational position of the knob on the panel of the originally designed air conditioner unit is different from the design, causing a problem that accurate and stable control of the fan motor cannot be performed. It is an object of the present invention to provide a motor drive device in which a motor voltage applied to both ends of a motor is not affected even if a motor current increases or a lead wire becomes long.

[0009]

To solve the above-mentioned problems, the present invention provides a motor connected between a DC power supply and a ground, a switching element for driving the motor,
A control unit for controlling the switching element, wherein the control unit detects a voltage of a voltage drop generated in a lead wire between the switching element and ground when the motor is energized, and detects the voltage of the voltage drop and the voltage A predetermined voltage for making the sum with the voltage generated at both ends of the switching element constant was output to the control terminal of the switching element. With this configuration, even if the lead wire between the switching element and the ground becomes long or the value of the motor current increases, the voltage applied to both ends of the motor is not affected. Can be controlled.

In the present invention, the DC power supply is a power supply obtained by dividing a constant voltage power supply by a variable resistor and changing the voltage. With this configuration, it is possible to produce a preset output voltage by varying the voltage, and it is possible to perform accurate and stable variable control of the motor based on the rotational position of the variable resistor.

In the present invention, the switching element is a power transistor. According to this configuration, a transistor that is frequently used as a switching element is used, so that handling is easy.

Further, in the present invention, the switching element is an FET. With this configuration, when an FET (field-effect transistor) is used as the transistor, the driving power is small, and a preferable motor driving circuit can be provided.

Further, in the present invention, the motor is a fan motor of an air conditioner for a vehicle. With this configuration, when applied to a fan motor of an air conditioner for a vehicle, accurate and stable control of the fan motor can be performed, and a more appropriate air flow than a fan can be given to a vehicle occupant.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a motor driving device according to the present invention will be described with reference to FIGS.

FIG. 1 is a circuit diagram showing a first embodiment of the motor drive device of the present invention. The circuit 1 of the motor drive device according to the present embodiment includes two motors 2 (2a, 2b), a transistor 8 as a switching element, and a transistor 8
A control unit 7 (hereinafter, referred to as CPU 7) for driving the
And a lead wire (resistor 9) from the transistor 8 to the ground.

The motor 2 is provided as a pair of two motors.
a is a driver motor on the driver's seat side, and motor 2b is a fan motor on the passenger's seat side. Since the two motors 2a and 2b are connected in parallel, the same voltage is applied to both ends of both motors, and the same fan output is performed. The motor current Im also flows through both motors 2a and 2b.

The switch section 3 is provided with an up switch 3a and a down switch 3b, which are fan output control switches, each having one end connected to a power supply 3c and the other end having a CPU.
7 has been entered.

The transistor 8 is an npn-type power transistor whose collector terminal is connected to the negative terminal of the motor 2 and whose emitter terminal is connected to the ground, and functions as a switching element. The base terminal of the transistor 8 receives a signal output from the CPU 7 and turns on the collector-emitter of the transistor 8. Also,
The collector-emitter voltage Vs of the transistor 8 has such a characteristic that it decreases as the potential of the base terminal increases.

The CPU 7 functions as a control unit and controls the D / A
It has a port 10 and an A / D port 11. CPU7
Turns on the transistor 8 with an analog signal output from the D / A port 10. Also, the CPU 7 supplies a voltage drop V of the lead wire (resistance 9) from the A / D port
The signal based on d is captured.

The operational amplifier 13 is connected to the connection point between the lead wire (resistor 9) and the emitter terminal of the transistor 8 and the A
/ D port 11. Operational amplifier 1
Reference numerals 4 and 15 are interposed between the D / A port of the CPU 7 and the base terminal of the transistor 8 in series.

The lead wire (resistor 9) connects between the emitter terminal of the transistor 8 and the ground, and generates a voltage drop Vd substantially due to the motor current Im.

As shown in FIG. 3, the air conditioner panel of this embodiment is provided with switch knobs 71 and 72 for turning on and off the switches 3a and 3b. The other configuration is the same as that of the conventional technology, and therefore, the same portions as those of the conventional technology are denoted by the same reference numerals and description thereof will be omitted.

In the above configuration, first, the switch unit 3
Of the fan output control switches 3a, 3b of the panel 69 are pressed an appropriate number of times. This becomes an instruction signal for determining the fan output (air volume) and is input to the CPU 7. The CPU 7 determines the fan output (air volume) by comparing a table stored in advance with the input instruction signal, controls the base voltage of the transistor 8, and controls the motor current Im. In this manner, the analog voltage Vi is output from the D / A port 10 of the CPU 7, and the voltage amplified by the operational amplifier 14 is applied to the base terminal of the transistor 8, so that the transistor 8 is turned on.
In addition, a desired current Im flows. Since a DC voltage is applied to the positive terminal of the motor 2 and the emitter terminal of the transistor 8 is connected to the ground via a lead wire (resistor 9), the motor 2 is energized and the motor current Im flows.
Operate the fan of the vehicle air conditioner. At this time, a voltage drop Vd substantially multiplied by the motor current Im and the value of the resistor 9 is generated in the lead wire. The motor voltage Vm is applied between the positive and negative terminals of the motor 2, the collector-emitter voltage Vs is applied between the collector and the emitter of the transistor 8,
A voltage drop Vd is distributed to the lead wire (resistor 9).

Since the voltage Vi is a voltage of 5 V or less, it is amplified by a factor of 2 to 3 by the operational amplifier 14 so that the transistor 8 which is a power transistor can be sufficiently driven. The operational amplifier 15 is used as a buffer to supply a current sufficient to drive the transistor 8. The voltage drop Vd of the lead wire is usually 1 V or less in many cases.
The signal is amplified twice and input to the A / D port 11 of the CPU 7. The CPU 7 increases the output voltage Vi from the CPU 7 in order to correct the reduction in the motor voltage Vm applied to both ends of the motor 2 based on the value of the voltage drop Vd.
The voltage (Vs + Vd) is made substantially constant by utilizing the decrease in the collector-emitter voltage Vs of the transistor 8.

A specific correction method will be described with reference to the flowchart of FIG. First, the voltage value a of the output voltage Vi required to turn on the transistor 8 is set to D /
Output from the A port 10 (S25). At this time, the voltage value c of the voltage drop Vd of the lead wire (resistor 9) is amplified three times and input to the A / D port 11 of the CPU 7, and the CPU 7 reduces the voltage drop Vd from the input voltage value 3c. Is calculated. At this time, the collector-emitter voltage Vs of the transistor 8 is determined by the output voltage Vi. The voltage value a of the output voltage Vi is amplified three times by the operational amplifier 14 and applied to the base terminal of the transistor 8, but the base voltage of the transistor 8 is not actually measured, and the voltage value a is tripled inside the CPU 7. From the calculated voltage value 3a of the base voltage, as the characteristic value of the transistor 8, C
The voltage value d of the corresponding collector-emitter voltage Vs stored in the storage unit of the PU 7 is read, and the voltage (Vd + V
Calculate the voltage value (c + d) of s). This voltage value (c +
The CPU 7 checks whether d) is greater than a predetermined voltage value b (S26). If the voltage value (c + d) is smaller than or equal to the voltage value b, the output voltage Vi remains at the voltage value a. If not, the output voltage Vi is replaced with the voltage value (a + c) (S27). At this time, the voltage value of the output voltage Vi (a +
The voltage value e corresponding to the collector-emitter voltage Vs corresponding to c) is read out, and the voltage (Vd + Vs) is read again.
Is calculated (c + e). Then, it is checked again whether the voltage value (c + e) is larger than the predetermined voltage value b (S28). The voltage value (c + e) is a predetermined voltage value b
If smaller or equal, the output voltage Vi is set to the voltage value (a + c). Voltage (c +) of voltage (Vd + Vs)
If e) is larger than the predetermined voltage value b, the voltage value of the voltage Vi is replaced from the voltage value (a + c) to the voltage value (a + 2c) (S27). At this time, a voltage value f corresponding to the collector-emitter voltage Vs corresponding to the voltage value (a + 2c) of the output voltage Vi is read out inside the CPU 7 as described above, and the voltage value (Vd + Vs) of the voltage (Vd + Vs) is again obtained. c +
f) is calculated. Then, it is checked again whether the voltage value (c + f) is larger than the predetermined voltage value b (S2).
8). If the voltage value (c + f) of the voltage (Vd + Vs) is smaller than or equal to the predetermined voltage value b, the output voltage Vi is set to the voltage value (a + 2c). Voltage (Vd + Vs)
If the voltage value (c + f) is larger than the predetermined voltage value b, the CPU 7 repeats the above operation.

In the normal state, that is, when the motor current Im is not large and the lead wire between the switching element and the ground is not too long, the voltage (Vd + Vs) becomes equal to the motor voltage Vm.
Has a predetermined voltage value g that does not affect the voltage. Since the voltage value b is set to a value slightly larger than the predetermined voltage value g, the voltage (Vd + Vs) is controlled so as to fall between the predetermined voltage value g and the voltage value b. become. Therefore, the voltage (Vd + Vs) is kept substantially constant, so that the motor voltage V
m converges to a fixed value, and the voltage value of the motor voltage Vm is not affected by the length of the lead wire between the transistor 8 and the ground or the magnitude of the current Im flowing through the motor 2.

A second embodiment of the present invention will be described with reference to FIG. FIG. 4 shows a second embodiment of the motor drive device of the present invention.
It is a circuit diagram showing an embodiment. In the description of the present embodiment, the first
The same parts as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The description of the air conditioner unit is the same as that of the prior art, so that the description is omitted.

In the circuit 1 ′ of this embodiment, the variable resistor 4 has a DC power supply 12 connected to one end of the variable resistor, and the voltage of the DC power supply is divided at each tap terminal 6 of the variable resistor 4. The DC voltage divided by the slider 5 that rotates and slides on each tap terminal 6 is drawn out.

By rotating the slider 5 of the variable resistor 4 by rotating the knob of the air conditioner unit, the motor 2
The DC voltage applied to the positive terminals of (2a, 2b) can be changed. Thus, the fan output can be changed by changing the current Im.

In each of the above embodiments, a power transistor is used as a switching element. However, the present invention is not limited to this, and an FET (field effect transistor) may be used instead. In this case, the driving power is preferably smaller than that of the power transistor. Further, in each of the above embodiments, it is described that Vd is added to the first Vi in S27 of the flowchart of FIG. 2, but the present invention is not limited to this, and the CPU has a table, The voltage to be applied may be determined from the table.

[0031]

As described in detail above, the present invention comprises a motor connected between a DC power supply and ground, a switching element for driving the motor, and a control unit for controlling the switching element. The unit detects a voltage of a voltage drop generated in a lead wire between the switching element and the ground when the motor is energized, and a predetermined voltage for keeping the sum of the voltage of the voltage drop and the voltage generated across the switching element constant. Since the voltage was output to the control terminal of the switching element, even if the lead wire between the switching element and the ground became long or the value of the motor current increased, it could affect the voltage applied to both ends of the motor. Since there is no motor, accurate and stable motor control is possible.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a motor drive device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a first embodiment of the present invention.

FIG. 3 is a plan view of the air conditioner unit according to the first embodiment of the present invention.

FIG. 4 is a circuit diagram of a motor drive device according to a second embodiment of the present invention.

FIG. 5 shows a motor drive circuit according to the prior art of the present invention.

FIG. 6 is a plan view of a conventional air conditioner unit of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circuit of 1st Embodiment of the motor drive device of this invention 1 'Circuit of 2nd Embodiment of the motor drive device of this invention 2 Motor 3 Switch part 4 Variable resistor 5 Slider 6 Tap terminal 7 CPU 8 Transistor 9 Resistance 10 D / A port 11 A / D port 12 DC power supply Im Motor current Vm Motor voltage Vs Collector-emitter voltage Vd Voltage drop Vi Output voltage

Claims (5)

[Claims] A motor connected between a DC power supply and ground; a switching element for driving the motor;
A control unit for controlling the switching element, wherein the control unit detects a voltage of a voltage drop generated in a lead wire between the switching element and ground when the motor is energized, and detects the voltage of the voltage drop and the voltage A motor driving device, wherein a predetermined voltage for making the sum of the voltage generated at both ends of the switching element constant is output to a control terminal of the switching element. 2. The motor drive device according to claim 1, wherein the DC power supply is a power supply obtained by dividing a constant voltage power supply by a variable resistor and changing the voltage. 3. The motor driving device according to claim 1, wherein the switching element is a transistor. 4. The motor driving device according to claim 1, wherein the switching element is an FET. 5. The motor drive device according to claim 1, wherein the motor is a fan motor of a vehicle air conditioner.