JP2933428B2 - Control system for vehicle brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for a brushless motor for a vehicle .

[0002]

2. Description of the Related Art Generally, a brushless motor for a vehicle using a DC power supply includes a microcomputer for outputting a duty ratio designation signal, a drive circuit connected to a plurality of coils of the brushless motor, and a brushless motor. A rotation detection sensor that detects rotation of the motor and outputs a rotation detection pulse, and a brushless motor is rotated by outputting a coil selection pulse to a drive circuit based on the rotation detection pulse from the rotation detection sensor and sequentially driving the coils. A logic controller for controlling, and a current control for receiving a duty ratio designation signal from the microcomputer and outputting a current control pulse of the designated duty ratio to the drive circuit to control the current to the coil and, consequently, the rotational speed of the brushless motor. And a circuit.

[0003]

In the above control system, for example, there is a disadvantage that the rotational speed fluctuates under the influence of a load. Therefore, it is conceivable that the actual rotation speed is fed back to the microcomputer as a voltage signal.However, when the control unit incorporating the microcomputer and the brushless motor and the other circuit configuration attached thereto are located at a distance from each other. Has the following disadvantages. That is, there is often a difference between the ground voltage of the control unit and the ground voltage of the brushless motor, and the microcomputer cannot accurately read the feedback voltage indicating the rotation speed. For this reason, even if the duty ratio is specified so that the read rotation speed matches the set speed, the actual rotation speed of the brushless motor cannot be maintained at the set speed. It is also conceivable to connect the control unit and the brushless motor with a ground line and ground this ground line.
Also in this case, the difference in the ground voltage cannot be eliminated due to the voltage drop in the ground line. In particular, when a large current flows through the brushless motor, the difference between the ground voltages increases.

[0004]

The present invention SUMMARY OF] has been made to solve the above problems, an air conditioner for a vehicle
A brushless motor for driving the air blower fan,
A position in the vehicle away from the brushless motor
And a microcomputer provided in the
(B) The brushless motor
A drive circuit connected to the coils of the
Detects rotation of a brushless motor and outputs a rotation detection pulse
(C) From the above rotation detection sensor
Coil selection in the above drive circuit based on the rotation detection pulse of
The pulse is output to drive the coil in order,
Logic controller that controls the rotation of a brushless motor
And (d) the duty from the microcomputer
The ratio control signal receives the current control parameter of this specified duty ratio.
Output to the above drive circuit to control the current to the coil
Control the rotation speed of the brushless motor.
Motor for a vehicle accommodating a current control circuit
In the control system, the microcomputer
However, the rotation detection pulse
Feedback pulse for either the
Received a pulse, and based on this feedback pulse,
Calculates the rotation speed of the brushless motor and calculates the calculated rotation
Specify the above duty so that the rotation speed matches the set speed.
Ratio and determine the frequency corresponding to the specified duty ratio.
Command signal line with pulse as duty ratio designation signal
To the current control circuit via the
Converts the frequency of the above duty ratio designation signal to voltage
Based on this voltage, the duty ratio of the current control pulse
To a value corresponding to the above specified duty ratio
And

[0005]

In the microcomputer, the rotation speed is calculated based on one of the cycles of the coil selection pulse and the rotation detection pulse. Therefore, even if the microcomputer is separated from the brushless motor and there is a difference in the ground voltage, there is no difference. Accurate calculation of rotational speed without adverse effects, and accurate duty ratio specification
A signal can be output. Moreover, the duty ratio finger
A constant signal is generated with a pulse having a frequency corresponding to the specified duty ratio.
Output without being affected by the difference in ground potential.
The duty ratio specification signal can be accurately transmitted to the current control circuit.
Can be. Also, even if there is some noise during transmission.
Noise by converting to voltage with the current control circuit.
The effect of noise can be almost ignored. As a result,
The actual rotation speed of the brushless motor can be reliably maintained at the set speed.

[0006]

FIG. 1 shows a control system for an air conditioner for a vehicle. This control system includes a control unit CU for controlling a brushless motor M for a blower fan and other actuators (not shown). This control unit CU
Are located away from these actuators, and a microcomputer 10 is built in the housing H. The microcomputer 10
It operates with a constant voltage applied from the constant voltage circuit 11 connected to the battery VB. The microcomputer receives detection signals from various sensors via an A / D converter (not shown) and receives switch signals from various switches (including a switch for setting the rotation speed of the blower fan). Output signals for controlling various actuators.

Next, a control system for the brushless motor M will be schematically described. The brushless motor M is a three-phase brushless motor, for example, has three coils L ₁ ~L _3. These are coils L ₁ ~L ₃ are connected to the driving circuit 20. The rotation of the brushless motor M is detected by three Hall elements 30 (rotation detection sensors). The rotation of the brushless motor M is controlled by the three-phase logic controller 40. The rotation speed of the brushless motor M is controlled by the current control circuit 50. The drive circuit 20, the Hall element 30, the three-phase logic controller 40, and the current control circuit 50 are attached to the brushless motor M. That is, it is mounted on a circuit board housed in the casing C of the brushless motor M.

The drive circuit 20 includes a pair of transistors TR ₁ and TR ₂ connected in series to each other, another pair of transistors TR ₃ and TR ₄ , and another pair of transistors TR ₅ and TR ₆ , respectively. Battery VB in parallel
Is configured by being connected to. Coil L ₁
Is connected between the transistors TR ₁ and TR ₂ , one end of the coil L ₂ is connected between the transistors TR ₃ and TR ₄ , and the coil L ₃ is connected between the transistors TR ₅ and TR ₆ . The other end of the coil L ₁ ~L ₃ are connected to each other. An AND circuit 21 is connected to the bases of the transistors TR ₂ , TR ₄ and TR ₆ .

The logic controller 40 receives a rectangular rotation detection pulse Pd from the Hall element 30 via the waveform shaping circuit 31. The logic controller 40 sequentially outputs the low-level coil selection pulse Ps ′ to the transistors TR ₁ , TR ₃ , and TR ₅ , and synchronizes with the coil selection pulse Ps ′ to apply a high level to one input terminal of the AND circuit 21. The level coil selection pulse Ps is sequentially output. For example, with turn on this by outputting a coil selection pulse Ps' to the base of the transistor TR _1,
By turning on the transistor TR ₄ outputs a coil selection pulse Ps to the AND circuit 21 connected to the transistor TR _4, the battery VB to the coil L _1, L ₂
Supply current from As described above, the rotation of the brushless motor M is controlled by sequentially exciting the two coils in accordance with the rotation of the brushless motor M.

The current control circuit 50 includes a comparator 5
1, a triangular wave generation circuit 52 for supplying a high-frequency triangular wave to one input terminal of a comparator 51, and a frequency-voltage conversion circuit 53. The microcomputer 1
From 0 , the designated duty ratio
The pulse of the frequency corresponding to the signal ratio is a long command signal line 1.
01 is supplied to the frequency-voltage conversion circuit 53.
The frequency-voltage conversion circuit 53 converts this frequency into a threshold voltage and provides the threshold voltage to the other input terminal of the comparator 51. Therefore, from the comparator 51,
A current control pulse Pc having a duty ratio corresponding to the designated duty ratio is output and supplied to the other input terminal of the AND circuit 21. As a result, the two selected coils are supplied with the current having the duty ratio, and the rotation speed of the brushless motor M is controlled.

[0011] Six coil selection pulse Ps outputted from the output terminal of the logic controller 40, one of the Ps' is diode D, resistors R and a long fees
The signal is fed back to the microcomputer 10 via the signal line 102 for feedback. Note that a Zener diode Z is connected to a connection point between the diode and the resistor R. The microcomputer 10 calculates the rotation speed from the cycle of the coil selection pulse Ps, and calculates the designated duty ratio so that the difference from the set rotation speed becomes zero.
Then outputs the duty ratio specified <br/> signal based on the calculation result.

As described above, since the rotation speed is calculated based on the cycle of the coil selection pulse Ps, the difference between the ground voltage of the brushless motor M and the ground voltage of the control unit CU is completely affected. no Rukoto, can be calculated accurately rotational speed, hii
Can output an accurate duty ratio designation signal.
You. In addition, the duty ratio specification signal is
Output as a pulse with the frequency corresponding to
The duty ratio designation signal is not affected by the
It can be accurately transmitted to the number-voltage conversion circuit 53.
Also, even if some noise enters during transmission,
-If the voltage is converted by the voltage conversion circuit 53, the effect of noise
Can be almost ignored. As a result, the actual rotation speed of the brushless motor M can be accurately maintained at the set speed.

The present invention is not limited to the above-described embodiment, and various embodiments are possible. For example, as shown by the imaginary line in FIG. 1, a rotation detection pulse Pd from the Hall element 30 may be fed back to the microcomputer instead of the coil selection pulse.

[0014]

As described above, according to the present invention, the microcomputer calculates the rotation speed based on one of the coil selection pulse and the rotation detection pulse. without receiving any adverse effects even if there is a difference in voltage, Ru can be accurately calculated rotational speed. I
In the voltage control circuit, the current control pulse
The duty based on the voltage converted from the frequency of the
Because of the tee ratio, regardless of differences in ground potential and noise
The duty ratio of the current control pulse
Can be set to the value specified by the data command. As a result, the actual rotation speed of the brushless motor can be reliably maintained at the set speed. Further, since a special circuit for forming the feedback signal is not required, the circuit configuration is simple.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a control system for a brushless motor for a vehicle according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Microcomputer 20 ... Drive circuit 30 ... Rotation detection sensor (Hall element) 40 ... Logic controller 50 ... Current control circuit101 ... signal line for command 102… feedback signal line  Pd: rotation detection pulse Ps: coil selection pulse

Claims (1)

(57) [Claims] (1)Ventilation fan of vehicle air conditioner
A brushless motor for driving the
The brushless motor
Equipped with a micro computer, In the brushless motor casing,  (I) Drives connected to multiple coils of brushless motor
(B) Rotation detection pulse by detecting rotation of brushless motor
And a rotation detection sensor that outputsC) Based on the rotation detection pulse from the rotation detection sensor
Output a coil selection pulse to the drive circuit
Drives the brushless motor in rotation
Logic controller that controlsD) Duty ratio finger from above microcomputer
Receiving a constant signal, and a current control pulse of this specified duty ratio
To the drive circuit to control the current to the coil.
And the current that controls the rotation speed of the brushless motor
Control circuit andFor vehicles containingControl of brushless motor
In the system, the microcomputer is a feedback signal line.
Of the rotation detection pulse or the coil selection pulse
This feedback is received after receiving one of the feedbacks.
The rotation speed of the brushless motor is
Calculate and this calculated rotation speed matches the set speed
The specified duty ratio is determined as
Pulse with a frequency corresponding to the duty ratio
As a constant signal to the current control circuit via the command signal line
Output,The current control circuit controls the frequency of the duty ratio designation signal.
The current control pulse is converted into a voltage based on this voltage.
To the value corresponding to the above specified duty ratio.
For vehicles characterized by Control system for brushless motor
Stem.