JPS6051416A - Motor drive device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field] The present invention includes a means for detecting when a motor rotor does not rotate or when the rotation stops during rotation, and stops the motor drive means when the means detects rotation failure. It relates to an electric motor drive device.

[Prior art]

In recent years, LBP (
Laser beam printers) and digital copiers that convert images into digital signals and have many functions not found in conventional analog copying machines, use lasers and rotating polygon mirrors for their high-speed printing performance and high image quality. (hereinafter referred to as polygon) and an optical system are commonly used.

In order to take full advantage of these features, a faster polygon drive motor is required. In addition, motor configurations are not limited to the conventional type using pole bearings (Fig. 1), but also types using hydrodynamic bearings using air as a medium (Fig. 1), which have very good high-speed performance, have been used. There is.

Figure 1 shows an example of a motor using a hydrodynamic bearing using air as a medium.A sleeve 8 rotates around a shaft 6 with a spiral groove through a layer of air. A polygon 10, a magnet 1, balance rings 5a, 5b, etc. are fixed to the stator coil 2. and a Hall element 3 are provided. The Hall element 3 detects a change in the polarity of the magnet l, and this signal causes the stator phase to be switched. Further, a white and black pattern is drawn on the lower balance ring 5b, and the rotation is controlled by reading the pattern with the reflective sensor 4.

FIG. 2 shows an example of a similar motor using a pole bearing 14, in which the upper bearing 14a is fixed to the bearing holder 13 and screwed to the motor plate 17.
The lower bearing 14b is preloaded by a spring 15 and maintains highly accurate rotation. The rest forms a so-called DC Hall motor similar to the motor described above.

A common problem with these motors is motor lock. That is, problems such as seizure of the pole bearing, rotational breakdown of the rotor, seizure of the dynamic pressure bearing, etc. may cause the motor to not rotate at the start, or the motor to lock during rotation. In this case, a large current that is normally allowed only for a very short period of time, such as when the motor starts up, will continuously flow into the motor, which will thermally damage the motor driver parts such as the power transistors in the motor drive circuit. Otherwise, there is a high possibility of damage to other parts due to temperature rise of the motor coil, short circuit, electric leakage, etc.

This was particularly noticeable when a large current was supplied at startup to shorten the startup time for a high-speed rotating motor, or when the temperature inside the product was high.

Conventionally, power transistors had to be made with a large capacity that was completely disproportionate in terms of cost and volume, or they had to use large heat sinks, large capacity fans, etc., which is extremely useful when trying to make them more compact and inexpensive. It was a disadvantage.

〔the purpose〕

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to provide a highly safe electric motor drive device. Another object of the present invention is to provide a motor drive device which includes a rotation failure detection means for detecting abnormal rotation of the motor when the motor starts up and during rotation, and which cuts off input to the motor and drive circuit when rotation failure is detected. This is provided in 5.

〔Example〕

A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a motor drive circuit diagram of one embodiment of the present invention.

In the figure, 20 is an abnormality detection circuit, 30 is a motor control circuit, 40 is a switch circuit that controls input to the motor drive section 75, 50 is an abnormality confirmation circuit, 60 is a reset circuit, and 7
0 is a polygon scanner motor, 71 is a stator coil of the polygon scanner motor 70, 72 and 73 are Hall elements, 74 is a rotation detection section that detects the motor rotation speed, and 75 is a motor drive section that rotates the polygon scanner motor 70. The motor drive unit 75 configures a switching circuit using semiconductors such as transistors, and controls the pole position of the rotor magnet (not shown) of the motor 70 by using Hall elements fH1 (72), H
2 (73), switches the aforementioned switching circuits based on this detection output, and drives the stator coils 71 connected to each switching circuit. By switching the magnetic poles of the stator coil 71, the rotor magnet starts rotating, and a desired rotation speed is obtained based on the input level to the motor drive section 75.

The rotation detection unit 74 reads the white and black patterns drawn on the lower balance ring 5 shown in the motor using the hydrodynamic bearing shown in FIG. 1 using the reflective sensor 4. The output signal of the light-receiving element is input to the waveform shaping section 64, where it is waveform-shaped and output as a rectangular wave from which waveform distortion and noise components in the detection section have been removed. The output of this waveform forming component 64 is input to the integrating circuit 21 of the abnormality detection circuit 20 and the phase comparator 31 of the motor control circuit 30.

To explain the motor control circuit 30 in detail, the motor control circuit 30 is a phased lock loop (hereinafter referred to as PLL).
The phase comparator 31 receives as input the reference period input from the reference oscillator 62 and the aforementioned waveform shaping section 64.
It has a comparison input synchronized with the rotation of the motor 70, and outputs the comparison result of the internal input as an output. The comparison input and the reference period input are compared, and if the input frequency of the comparison input is smaller than the reference period input, a high level signal is output, and if the input frequency of the comparison input is larger than the reference period input, a low level signal is output. The reference period input signal is compared with the input signal.If the input signal and the input signal have the same period, a pulse waveform corresponding to the phase difference of the re-input signal is output. At the same time, the synchronization detection terminal output is turned on to output that frequency synchronization has been achieved.

The low-pass filter 32 is for converting this pulse waveform output into a DC signal, and obtains a DC level signal according to the output state of the phase comparator 31. The DC output signal from the low-pass filter 32 is input to a phase correction section 33, where the delay in the phase characteristics of the closed-loop control circuit due to the phase delay caused by the low-pass filter 32 is corrected.

As described above, by making the output frequency of the waveform shaping section 64 obtained from the desired rotation speed by this PLL control circuit the same as the output frequency of the reference oscillator 62, the crystal oscillator of the reference oscillator 62 is oscillated. Accurate rotation speed can be obtained with precision.

A switch circuit 40 is provided between the motor control circuit 30 and the motor drive unit 75, and the motor control circuit 3
Enables/disables signals starting from 0. When the motor drive control signal 29 is on and at a high level, the input from the motor control circuit 30 is valid, and when it is off and at a low level, the signal from the motor control circuit 30 is invalidated, and the drive signal of the motor drive unit 75 is invalidated.

Next, the abnormality detection circuit 20 will be explained with reference to the timing chart of FIG. 4. FIG. 4(a) is an operation timing chart of the abnormality detection circuit 30 when the motor rotation is normal, and FIG. 4(b) is an operation timing chart of the abnormality detection circuit 30 when the motor rotation is abnormal. The operation of the abnormality detection circuit 30 at the time is 0. It is the timing chart.

First, when the motor 70 is stopped in the lz state m1, there is no output from the rotation detection section 74, there is no pulse output from the waveform shaping section 64, and the output from the phase correction section 33 of the motor control circuit 30 is in the motor drive level output mode.

However, the drive signal 61 is off, and the abnormality detection circuit 20
AND gate 27 is not satisfied, and AND gate 28 is also not satisfied. Therefore, the motor drive control signal 29 becomes low level, invalidating the output signal of the phase correction section 33, and the motor drive section 75 receives no drive signal.

When the drive signal 61 changes from off to on in this state, the reset circuit 60 operates, outputs a reset signal for a time constant determined by R1 and CI, and resets the flip-flop (hereinafter referred to as F/F) 26. . (This reset signal has been output for more than T1 time, which will be described later.) Therefore, the Q output of F/F26 becomes high level, and the above-mentioned AND game) 27.28
is satisfied, the motor drive control signal 29 is turned on, a motor drive signal is output to the motor drive unit 75, and the stator coil 71 is sequentially excited to rotate the motor 70.

At the same time, the drive signal 61 is input to a delay circuit 23 consisting of a monostable multivibrator, and the output is kept at a low level for a time constant time (T1) determined by R2 and C2. When the delay circuit 23 becomes high level after the time T1 has elapsed, both inputs A and B of the multivibrator 24 become high level, and the astable multivibrator 24 starts oscillating.

During the time width T1 of the delay circuit 23, even if a drive signal is applied to the motor 70, the motor 70 does not rotate immediately due to the inertia of the rotor. For this reason, this is to prevent erroneously detecting that the motor 70, which will be described later, is malfunctioning during this period.

In this way, the delay circuit 23 determines the start point of rotation failure detection operation.
The period (TZ) of the astable multivibrator 24, which is the period of abnormality detection during rotation of the motor 70, can be shortened, and the period (TZ) of the astable multivibrator 24, which is the period of abnormality detection during motor 70 rotation, can be shortened. It is now possible to quickly perform protection processing.

When the output of the delay circuit 23 changes to a high level and the drive signal 61 is on and at a high level, the astable multivibrator 24 starts oscillating at a constant period T2, and this oscillation signal is transmitted to the clock input terminal f of the F/F 26. is input.

Now, when the motor 3 70 driven by the motor drive section 75 starts rotating, a rectangular wave output is input from the waveform shaping section 64 to the integrating circuit 21 . The input rectangular wave output is integrated by the integrating circuit 21, and as the rotational speed increases, the output level of the integrating circuit 21 also increases. When the number of revolutions exceeds a certain number (point P in FIG. 4(a)), it exceeds the threshold level of the Schmitt trigger 22, and the output of the Schmitt trigger 22 becomes low level. This Schmitt trigger 22 output is connected to the D input terminal of the F/F 26, and the F/F 24 output is the astable multivibrator 24 output.
If the motor rotation speed exceeds a certain number before the clock input terminal of /F26 reaches the falling edge, F/F26 will not be set and the motor drive control signal 29 will go to high level as shown in FIG. 4(a). The motor is rotated and stopped in accordance with the drive signal 61.

4 If the motor 70 does not rotate even when the motor drive signal is applied by the motor drive unit 75, there is no output from the waveform shaping unit 64 as shown in FIG. 4(b), and the output of the integrating circuit 21 is also at a low level. It remains as it is. Therefore, the Schmitt trigger 22 output also remains at high level, and when the clock terminal input of the F/F 26 falls, that is, after the T time in the delay circuit 23 and the 12-hour oscillation period (TI+TZ time) of the multivibrator 24 have elapsed. F/F 26 is set, the output becomes low level, AND gates 27 and 28 are not satisfied, motor drive control signal 29 is turned off, becomes low level, and the motor drive signal to motor drive unit 75 is output by the action of switch circuit 40. is inhibited.

Here, we have described an example in which the motor 70 did not rotate from the beginning of the drive, or if the rotation of the motor 70 stops due to some abnormality after it has started rotating normally, the rotation detection signal output from the rotation detection section 74 will be stop,
Since the output from the waveform shaping section 64 is also stopped, the output of the integrating circuit 21 of the abnormality detection circuit 20 becomes low level, and the output of the Schmitt trigger 22 becomes high level. For this reason F
The D input terminal of /F26 becomes high level, F/F26 is set in synchronization with the fall of the clock from astable multivibrator 24, the output of F/F26 becomes low level, and the output of AND gate 27.28 becomes low level. The level becomes low, and the drive signal for the motor drive section 75 from the motor control circuit 30 is inhibited by the switch circuit 40, which serves as a safety circuit against motor lock while the motor is rotating.

Furthermore, in the above explanation, the switch circuit 40 is referred to as the motor drive section 7.
The motor drive unit 75 has been described as a selection circuit for validating or invalidating the drive control signal 6.
Turn on/off the drive power supply for the motor 70, for example, the drive power supply for the driver section that drives the stator coil 71 of the motor 70.
It is obvious that the same effect can be obtained even with a configuration in which the power is turned off.

Furthermore, as shown in FIG.
This abnormality confirmation circuit 50 also includes a flip-flop 51.0. , a reset switch RSWI, and an LED 1 indicating whether it is normal or abnormal. The D input terminal of the D-type flip-flop 51 of the abnormality confirmation circuit 50 is held at high level, and the clock input terminal is connected to the F/F.
When the F/F 26 is set, the Q output terminal changes from low level to high level, and this flip-flop 51 is set. In other words, when an abnormality occurs in the motor rotation, the abnormality is detected.7 When the circuit 20 detects the abnormality, the flip-flop 51
is set. A light emitting diode LED 1 is connected to the Q output terminal of the flip-flop 51, and LED 1 is connected to Vcc via a protective resistor. For this reason,
When the flip-flop 51 is reset, the LED 1 is on, but when the flip-flop 51 is set, it goes out, indicating that the motor 70 is malfunctioning.

Further, the reset terminal of this flip-flop 51 cannot be reset unless the reset switch R3WI is operated, so that if the drive signal 61 is turned on by mistake after detecting an abnormality in the motor 70, T + T motor drive section 7
5 from driving the motor 70, and the motor 70 will not be driven by mistake.

When the flip-flop 8 knob 51 of the abnormality confirmation circuit 50 is set in this way, its Q output becomes low level, and a low level signal is applied to the input of the AND gate 28 of the abnormality detection circuit 20, and the output of the AND gate 28 A certain motor drive control signal 29 is kept at a low level to prevent the motor drive unit 75 from being driven.

Then, by operating the reset switch RSWI after removing the cause of the motor rotation stopping f1-, the flip-flop 51 is reset and the motor drive prohibited state is released.

As mentioned above, by providing a detection circuit like the one described in F in the motor drive device, the problem occurs when dirt or the like gets into the gap of the motor's dynamic pressure bearing or when a large #shock is applied. Even if the rotation of the 90-meter stops due to problems such as bearing seizure, locking due to rotational damage of the magnet, seizure due to deterioration of the pole bearing, etc., the input to the drive circuit and motor will be cut off. An electric motor drive device that does not damage other functional parts by simply replacing the motor can be realized.

This is particularly effective as a safety device for motors using air bearings, which are characterized by high speed and long life, and high-load, high-speed motors with large input power.

Also, the motor startup time is relatively long (for example, 10 se
c) This is a safety device for the motor drive circuit that is also effective for motors.

Additionally, in the event that an abnormality occurs in the motor drive section and an excessive current flows through the stator coil of the motor and the motor cannot rotate, a method such as turning off the motor drive power of the motor drive section described above is provided. By doing so, it is possible to prevent damage to the motor.

Also, as can be seen from the above, this method is not limited to DC motors, and even AC motors can be controlled in exactly the same way, just by changing the specific driving method, and the motor has no rotation detection means. All you have to do is have it. This rotation detecting means is not limited to the above-mentioned one, but also a magnetic head,
It is also possible to detect changes in the magnetic pole of a magnet using an encoder using a photocoupler or a Hall IC, or to directly use the signal from a Hall element for controlling a DC Hall motor.

[Effects] As described above, according to the present invention, the rotation detection function provided in the motor is used to inhibit the drive circuit of the motor when the motor does not rotate correctly, so that the drive circuit detects whether the motor is operating normally. 1 Motor drive that can use standard elements for rotation in each driver stage, eliminates the need for large-capacity transistors and resistors, and reduces component costs and space. The device was realized.

Furthermore, an electric motor drive device has been realized that minimizes failures and does not cause failures in other parts even when a failure occurs in the motor, motor driver, etc.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a motor using a hydrodynamic bearing using air as a medium, Fig. 2 is a sectional view of a motor using a pole bearing as a bearing, and Fig. 3 is a motor drive wh circuit according to an embodiment of the present invention. 4(a) is an operation timing chart of the motor drive circuit of this embodiment when the motor rotates normally, and FIG. 4(b) is an operation timing chart of the motor drive circuit of this embodiment when the motor is malfunctioning. In the figure, ■... Magnet, 2,71... Stator coil, 3.72, 73... Hall element, 4... Reflective sensor, 10... Polygon, 20... Abnormality detection circuit , 21... Integral circuit, 30... Motor control circuit,
40... Switch circuit, 50... Abnormality confirmation circuit, 6
0... Reset circuit, 62... Reference oscillator, 70...
...Motor, 74...Motor rotation detection section, 75...
This is a motor drive unit. 3 Figure 1

Claims (2)

[Claims] (1) A driving means for rotationally driving an electric motor, a rotation detecting means for detecting rotation of the electric motor driven by the driving means, and a monitoring means for monitoring the state of the electric motor, and the monitoring means includes the An electric motor drive device, characterized in that the rotational drive of the electric motor by the drive means is stopped when no rotation is detected by the rotation detection means after a predetermined period of time has elapsed after the drive means is activated. (2) The electric motor drive device according to claim 1, wherein after the elapse of a certain period of time, the electric motor is rotated -1 time.