JPH1169859A - Motor control circuit - Google Patents

Abstract

[PROBLEMS] To provide a motor control circuit which can supply a sufficient drive current under a heavy load without using a semiconductor switch such as an FET having a large withstand voltage and, consequently, without increasing the size of the device. A control circuit for controlling the number of revolutions of an electric motor such as an electric lawnmower or an electric tool, comprising: a motor; a FET provided in an energizing circuit for the motor; and a pulse corresponding to the number of revolutions of the motor. Pulse generation means 3 and a rotation pulse detection circuit 4 for detecting the speed, an integration circuit 5 for generating a voltage corresponding to the number of rotations, an overload detection circuit 6 for detecting an overload state, and a speed setting for setting the rotation speed of the motor 1 Circuit 7, the output of the overload detection circuit 6 and the output of the speed setting circuit 7
FET drive circuit 8 for turning on / off ET2, FET2
And a flip-flop circuit 10 for controlling the energization of the coil of the relay 9 according to the load state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit for an electric lawnmower or a power tool using an electric motor, and more particularly to a motor control circuit capable of increasing the driving current of the electric motor when the electric motor is under a high load. To apply to effective technology.

[0002]

2. Description of the Related Art As a technique studied by the inventor, for example, a motor control circuit generally uses a semiconductor switch such as an FET on a power supply side or a ground side of a motor. This is based on FET ON / OFF control (PW
M control) makes it possible to control the drive current, and the motor speed and torque can be controlled freely, which is effective as motor control.

[0003]

In the above-described motor control circuit, since the driving current of the motor increases as the load increases, a semiconductor switch such as an FET that can sufficiently withstand the driving current is required. This requires the use of a device that takes into account the increase in the size of the elements and heat dissipation, which leads to an increase in the size of the control circuit and an increase in cost.

Therefore, an object of the present invention is to provide a high withstand voltage F
It is an object of the present invention to provide a motor control circuit that can supply a sufficient drive current under a heavy load without using a semiconductor switch such as an ET, and thus without increasing the size of the device.

[0005] The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0006]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, a motor control circuit according to the present invention comprises: a motor; switch means provided in an energizing circuit for the motor; rotation number detection means for detecting the rotation number of the motor; Control means for comparing the motor speed detected by the speed detection means with the set speed of the speed setting circuit to control ON / OFF of the switch means; bypass means provided in parallel with the switch means; Power supply switching means for turning on the bypass means when the number is equal to or less than a predetermined value. Further, a setting rotation speed varying means for changing the setting rotation of the rotation speed setting circuit is added.

According to the motor control circuit, the number of rotations of the motor is compared with the set number of rotations to control ON / OFF of a switch provided in a circuit for energizing the motor, and the motor speed is controlled to a predetermined value. The bypass means provided in parallel with the switch means can be turned on in accordance with the load state determined by the fall below the value.
That is, the energization switching means can turn on the bypass means at a high load, for example, at a high load in which the rotation speed of the motor has decreased by a predetermined number.

As a result, even when a semiconductor element such as an FET is used as the switch means, a drive current suitable for the load can be supplied to the motor while reducing the size of the semiconductor switch. Further, when the setting rotation speed varying means is added, the setting of the rotation speed of the motor can be easily changed.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram schematically showing an electric motor control circuit using a motor control circuit according to Embodiment 1 of the present invention in an electric lawn mower, an electric tool, or the like. FIG. 3 is a timing chart showing control at the time of startup in the electric motor control circuit using the motor control circuit according to the first embodiment, and FIG. 3 is a timing chart showing control at the time of overload.

First, a schematic configuration of an electric motor control circuit using the motor control circuit according to the first embodiment will be described with reference to FIG.

An electric motor control circuit using the motor control circuit according to the first embodiment is a control circuit for controlling the number of revolutions of an electric motor such as an electric lawn mower or an electric tool. F provided in the current supply circuit to 1
ET2, a rotation pulse generating means 3 for generating a pulse corresponding to the rotation speed of the motor 1, a rotation pulse detection circuit 4 for detecting the rotation pulse, and a rotation speed while repeating charging and discharging according to the voltage of the rotation pulse. , An overload detection circuit 6 for detecting an overload state from this voltage, a speed setting circuit 7 for setting the rotation speed of the motor 1, an overload detection circuit 6, and a speed setting. FE for comparing the output with the circuit 7 and controlling ON / OFF of the FET 2
It comprises a T drive circuit 8, a contact point of a relay 9 provided in parallel with the FET 2, and a flip-flop circuit 10 for controlling energization of a coil of the relay 9 according to a load state.

The motor 1 includes a stator that generates a magnetic field by a permanent magnet, and a rotor that rotates by generating a torque in the magnetic field generated by the stator. For example, the armature of the rotor is formed by winding coils in six parallel circuits in a superimposed manner. And a brush is provided for each parallel circuit,
It has a six-pole motor structure having six brushes, and a plurality of energizing circuits are connected to these brushes. Through these energizing circuits, three positive brushes are commonly connected via a switch 11. Connected to the power supply voltage of the DC power supply 12,
The negative brushes are grounded via the FET 2 and the contact of the relay 9 which are commonly connected in parallel.

The FET 2 is switch means for turning on / off the negative electrode of the motor 1 by using an output signal from the FET drive circuit 8 as an input.
For the signal, the negative brush of the motor 1 is connected to the ground side, and the brush circuit of the motor 1 is turned on.
For the signal, the connection from the negative brush to the ground side is cut off, and the signal is turned off. This switch means can be applied to other semiconductor switches such as transistors, for example, in addition to the FET2.

The rotation pulse generating means 3 is means for generating a rotation pulse of the rotor rotating in the magnetic field generated by the stator of the motor 1.
A method for generating a rotation pulse using a Hall element by fixing a rotation detection magnet to the drive shaft of the motor is used. The rotation pulse generated by the rotation pulse generating means 3 is output to a rotation pulse detection circuit 4. You.

The rotation pulse detection circuit 4 is a circuit for detecting a rotation pulse from the rotation pulse generation means 3. The rotation of the motor 1 is detected as a pulse by a combination of the rotation pulse detection circuit 4 and the rotation pulse generation means 3. It is supposed to be. As a method of detecting the rotation of the motor 1, there is a method of detecting the number of rotations using a tachogenerator.

The integration circuit 5 receives the rotation pulse detected by the rotation pulse detection circuit 4 as an input, and repeats charging and discharging in accordance with the input of the rotation pulse to generate a voltage corresponding to the number of rotations. The integration circuit 5 converts the rotation speed of the motor 1 into a voltage, which is output to the overload detection circuit 6 and the speed setting circuit 7.

The overload detection circuit 6 is a comparison circuit which takes the output voltage from the integration circuit 5 as a negative input (-) and compares this input voltage with a voltage of a preset reference value of a positive input (+). The comparison result is inverted through an inverter. When the input voltage is lower than the reference voltage, the voltage is low (“L”), and when the input voltage exceeds the reference voltage, the voltage is high (“H”). Are respectively output.

The speed setting circuit 7 is a comparison circuit which takes the output voltage from the integration circuit 5 as a negative input (-) and compares this input voltage with a voltage of a predetermined reference value of a positive input (+). When the input voltage is lower than the reference voltage, a "H" voltage is output, and when the input voltage exceeds the reference voltage, a "L" voltage is output.

The FET drive circuit 8 receives the output voltage from the speed setting circuit 7 and the non-inverted output voltage of the flip-flop circuit 10 as inputs, compares these voltages, and turns the FET 2 on.
A circuit for performing N / OFF control. When the output voltage from the speed setting circuit 7 is “H” and the normal output voltage of the flip-flop circuit 10 is “H”, the “H” voltage that turns on the FET 2. Is output, otherwise, FET
2 is turned off, an “L” voltage is output.

The relay 9 has this coil connected between the power supply voltage and the inverted output of the flip-flop circuit 10, and the normally closed contact is connected in parallel with the FET2. Voltage is “L”
In this case, the coil is energized to be in an excited state. In this excited state, the contact is opened and the connection from the negative brush of the motor 1 to the ground side is cut off, so that the motor 1 is de-energized. Sometimes, the coil is in a non-excited state and the contact is kept closed, so that the negative brush of the motor 1 is connected to the ground side and the brush circuit of the motor 1 is energized. That is, the contact of the relay 9 is closed when the rotation speed of the motor 1 is lower than a preset rotation speed.

The output of the flip-flop circuit 10 is reset when there is a reset input (R), conversely, the output is set when there is a set input (S). An RS flip-flop for holding the output voltage from the overload detection circuit 6 as a reset input and the output voltage from the speed setting circuit 7 as a set input.
The drive circuit 8 is controlled, and the relay 9 is controlled by the voltage of the inverted output (/ Q) so that the FET 2 and the contact of the relay 9 are not energized at the same time.

Next, the operation of the first embodiment will be described with reference to FIG. 2 showing the control timing at the time of starting the operation of the electric motor control circuit.

(1) Prior to starting the motor 1, the reference value voltage of the overload detection circuit 6 is set to TH1, and the reference value voltage of the speed setting circuit 7 is set to TH2.

(2) Since the motor 1 is in the stopped state in the initial state at the time of starting, the voltage waveform B output from the integration circuit 5 through the rotation pulse generation means 3 and the rotation pulse detection circuit 4 is 0V. is there. At this time, the overload detection circuit 6
Is "L", the output voltage D of the speed setting circuit 7 is "H", and the normal output E of the flip-flop circuit 10 is output.
Is "L" and the inverted output F is "H".

Therefore, the OFF signal is output from the FET drive circuit 8 and the FET 2 is turned off, while the coil of the relay 9 is de-energized and the contact is kept closed. And is connected to the ground side via the contact.

(3) When the switch 11 is turned on for starting, the positive brush of the motor 1 is connected to the power supply voltage of the DC power supply 12 via the switch 11, and the negative brush is connected via the contact of the relay 9. Since the motor 1 is grounded, the motor 1 starts rotating.

(4) As the number of rotations of the motor 1 increases gradually, the number of rotation pulses output from the rotation pulse detection circuit 4 via the rotation pulse generation means 3 increases, and the integration circuit 5 The voltage waveform B output from the terminal gradually increases.

(5) If the voltage exceeds the reference value voltage TH1 of the overload detection circuit 6 during the rise of the voltage waveform B from the integration circuit 5 accompanying the increase in the rotation speed of the motor 1, overload detection is performed. Although the output voltage C of the circuit 6 shifts from “L” to “H”, the flip-flop circuit 10 keeps its state, and the energization of the motor 1 is continued through the contact of the relay 9.

(6) When the rotation speed of the motor 1 further increases and the voltage output from the integration circuit 5 exceeds the reference value voltage TH2 of the speed setting circuit 7, the output voltage D of the speed setting circuit 7 becomes "H". "" To "L". Accordingly, the flip-flop circuit 10 is set, the normal output E changes from "L" to "H", the inverted output F changes from "H" to "L", and the coil of the relay 9 is set in the excited state. The contact is opened, the connection from the negative brush of the motor 1 to the ground side is cut off, and the motor 1 is turned off. At this time, the input from the speed setting circuit 7 of the FET drive circuit 8 is "L" and the FE
T2 is in the OFF state.

Until this point, that is, when the switch 11 is turned on at the time of the start of the above (3), until the output voltage from the integration circuit 5 exceeds the reference value voltage TH2 of the speed setting circuit 7, the motor 1 is turned on. The state can be controlled by the contacts of the relay 9 being closed. As a result, a large starting current at the time of starting flows through the contact of the relay 9.

(7) When the motor 1 is de-energized, the rotation speed of the motor 1 gradually decreases, and the rotation pulse output from the rotation pulse detection circuit 4 via the rotation pulse generating means 3 accordingly. The number decreases, and the voltage waveform B output from the integration circuit 5 shifts from rising to falling.

(8) When the voltage becomes lower than the reference value voltage TH2 of the speed setting circuit 7 during the fall of the voltage waveform B from the integrating circuit 5 accompanying the decrease in the rotation speed of the motor 1, the speed setting circuit 7 Changes from “L” to “H”. Along with this, an ON signal is output from the FET drive circuit 8 to turn on the FET 2, and the negative brush of the motor 1 is connected to the ground side via the FET 2 and
Is turned on. At this time, the flip-flop circuit 1
Since 0 does not change, the contact of the relay 9 remains open.

(9) When the motor 1 is energized, the rotation speed of the motor 1 gradually increases again, and the rotation pulse output from the rotation pulse detection circuit 4 via the rotation pulse generating means 3 accordingly. As the number increases, the voltage waveform B output from the integration circuit 5 shifts from falling to rising.

(10) During the rise of the voltage waveform B from the integrating circuit 5 accompanying the increase in the rotation speed of the motor 1, if this voltage again exceeds the reference value voltage TH2 of the speed setting circuit 7, the speed setting circuit 7, the output voltage D changes from “H” to “L”. Along with this, the OF drive from the FET drive circuit 8
When the F signal is output, the FET 2 is turned off, and the connection from the negative brush of the motor 1 to the ground side is cut off.
Is turned off again.

(11). Thereafter, the operation from the above (7) is repeated, and the comparison result between the output voltage from the integrating circuit 5 corresponding to the rotation speed of the motor 1 and the reference value voltage TH2 of the speed setting circuit 7 is obtained. Based on this, the ON / OFF control of the FET 2 by the ON / OFF signal from the FET drive circuit 8 can control the energized / de-energized state of the motor 1 and keep the rotation speed of the motor 1 constant. In this state, the output of the flip-flop circuit 10 does not change.
Keep the open state.

Next, the control timing at the time of overload will be described with reference to FIG.

(21). ON of FET2 in the above control
During the repetitive control of the energized / deenergized state of the motor 1 by the / OFF control, for example, when a large load is applied to the motor 1, the rotation speed of the motor 1 gradually decreases, and the rotation pulse generation means 3 As a result, the number of rotation pulses output from the rotation pulse detection circuit 4 decreases, and the voltage waveform B output from the integration circuit 5 drops significantly.

That is, when a large load is applied to the motor 1, the voltage output from the integration circuit 5 becomes lower than the reference value voltage TH 2 of the speed setting circuit 7 and lower than the reference value voltage TH 1 of the overload detection circuit 6. Become. At this time, the output voltage C of the overload detection circuit 6 shifts from “H” to “L”.

Accordingly, the flip-flop circuit 10
Output E is from "H" to "L", and inverted output F is "L".
To “H”, an OFF signal is output from the FET drive circuit 8 and the FET 2 is turned off. However, since the coil of the relay 9 is de-energized and the contact is closed, the negative brush of the motor 1 is turned off. Is connected to the ground side via the contact of the relay 9 and the motor 1 continues to be energized.

(22) In the energized state from the brush via the contact of the relay 9, a current corresponding to the load is supplied to the motor 1, and if the load is not reduced, the rotation speed of the motor 1 does not increase ( (Dotted line in FIG. 3), when the contact of the relay 9 is kept closed and the load is reduced, the number of rotations of the motor 1 gradually increases, and the rotation pulse is detected via the rotation pulse generating means 3 accordingly. As the number of rotation pulses output from the circuit 4 increases, the voltage waveform B output from the integration circuit 5 shifts from falling to rising.

(23). If the voltage exceeds the reference value voltage TH1 of the overload detection circuit 6 during the rise of the voltage waveform B from the integration circuit 5 accompanying the increase in the rotation speed of the motor 1,
The output voltage C of the overload detection circuit 6 shifts from “L” to “H”, but the flip-flop circuit 10 holds the reset state.

(24). The rotation speed of the motor 1 further increases,
When the voltage output from the integration circuit 5 exceeds the reference value voltage TH2 of the speed setting circuit 7, the output voltage D of the speed setting circuit 7
Changes from “H” to “L”. Accordingly, the normal output E of the flip-flop circuit 10 changes from “L” to “H”,
The inverted output F shifts from “H” to “L”, the coil of the relay 9 is excited and the contacts are opened, the connection from the negative brush of the motor 1 to the ground side is cut off, and the motor 1 is turned off. Become.

Up to this point, that is, after the output voltage from the integration circuit 5 becomes less than the reference value voltage TH1 of the overload detection circuit 6 after the overload is applied to the motor 1 of the above (21), the speed setting circuit 7 At the time of a high load exceeding the reference value voltage TH2, the energized state of the motor 1 can be controlled by closing the contact of the relay 9.

(25). Thereafter, the operation from the above (7) in the control at the start-up is repeated again, and the output voltage from the integrating circuit 5 corresponding to the rotation speed of the motor 1 and the reference of the speed setting circuit 7 Based on the result of comparison with the value voltage TH2, the energizing / deenergizing state of the motor 1 is repeated by ON / OFF control of the FET 2 by an ON / OFF signal from the FET driving circuit 8 in place of the relay 9 to keep the rotation speed constant Can be kept.

Therefore, according to the electric motor control circuit of the first embodiment, the contact of the relay 9 is connected in parallel to the FET 2 that controls ON / OFF of the negative electrode of the motor 1,
Is turned on / off, and the contacts of the relay 9 are opened and closed in accordance with the load state, so that the contact of the relay 9 is started via the FET 2 when the motor 1 is started or overloaded, and via the FET 2 when the load is small. Since the brush can be connected to the ground side, F
By switching to the ET 2 or the contact of the relay 9, a drive current suitable for the load can be supplied to the motor 1.

In particular, when the motor 1 is started or overloaded, by connecting via the contact of the relay 9, there is no need to consider the drive current flowing through the FET 2, and it is not necessary to use the FET 2 having a large withstand voltage. The size of the FET 2 can be reduced.

(Embodiment 2) FIG. 4 is a block diagram schematically showing an electric motor control circuit in which the motor control circuit according to Embodiment 2 of the present invention is used for an electric lawn mower, a power tool or the like.

An electric motor control circuit using the motor control circuit according to the second embodiment includes a control circuit for controlling the number of revolutions of an electric motor such as an electric lawn mower or an electric tool, as in the first embodiment. Then, as shown in FIG.
ET2, rotation pulse generating means 3, rotation pulse detection circuit 4, integration circuit 5, overload detection circuit 6, speed setting circuit 7,
FET drive circuit 8, relay 9, flip-flop circuit 1
0 and the like, and the difference from the first embodiment is as follows.
The difference is that reference value changing means 13 for changing the reference values of the overload detection circuit 6 and the speed setting circuit 7 is added.

That is, in the second embodiment, the reference value variable means 13 sets the plus input reference value voltage of the overload detection circuit 6 and the plus input reference value voltage of the speed setting circuit 7 to arbitrary voltage values, respectively. The motor 1 corresponding to the reference value voltage of the overload detection circuit 6
Can be changed, and the rotation speed of the motor 1 corresponding to the reference value voltage of the speed setting circuit 7 can also be changed.

Therefore, according to the electric motor control circuit of the second embodiment, similarly to the first embodiment, the drive current suitable for the load is supplied to the motor 1 while the FET 2 is downsized. In addition to the above, the addition of the reference value varying means 13 for varying the reference values of the overload detection circuit 6 and the speed setting circuit 7 makes it possible to determine the number of rotations of the motor 1 and the condition for determining the overload of the motor 1. The setting of the number of rotations can be easily changed.

Although the invention made by the inventor has been specifically described based on the first and second embodiments of the present invention, the present invention is not limited to the above-described embodiment and does not depart from the gist of the invention. It goes without saying that various changes can be made within the range.

For example, in the above embodiment, 6
Although the description has been given of the case of a six-pole motor having three brushes, the present invention is not limited to the above-described embodiment, and a multi-pole brush having a large number of brushes such as two, four, eight, etc. It is widely applicable to motors.

In the above embodiment, the case where the negative brush side is energized or the energization is cut off to de-energize is described. Conversely, the positive brush side may be energized / de-energized. Needless to say,

In the above description, the case where the invention made by the present inventor is mainly applied to a motor control circuit used for an electric lawnmower, a power tool, or the like, which is a technical field to which the invention belongs, has been described. However, the present invention is widely applicable to motor control circuits of other devices and devices having a DC brush motor.

[0057]

Advantageous effects obtained by typical ones of the inventions disclosed in the present application will be briefly described.
It is as follows.

(1) The number of rotations of the motor is compared with the set number of rotations, and a switch provided in a circuit for supplying power to the motor is turned on / off.
By turning off the bypass means provided in parallel with the switch means when the rotation number of the motor is lower than a preset rotation number while turning off the motor, a large current at the time of high load flows through the bypass means. Therefore, even when a semiconductor element such as an FET is used as the switch means,
It is possible to supply a drive current corresponding to the load to the motor while reducing the size of the semiconductor switch.

Since it is not necessary to provide a means for detecting a load current in series with the load, the power consumption can be reduced.

(2) In the case where the setting rotation speed variable means is added, it is possible to easily change the setting of the rotation speed of the motor and the overload condition determined by the rotation speed of the motor.

(3) According to the above (1) and (2), a motor control circuit capable of supplying a sufficient drive current under a high load without using a semiconductor switch having a large withstand voltage and, consequently, without increasing the size of the device. Can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing an electric motor control circuit in which a motor control circuit according to a first embodiment of the present invention is used for an electric lawnmower, a power tool, or the like.

FIG. 2 is a timing chart showing control at the time of startup in an electric motor control circuit using the motor control circuit according to the first embodiment of the present invention;

FIG. 3 is a timing chart showing control at the time of overload in the electric motor control circuit using the motor control circuit according to the first embodiment of the present invention;

FIG. 4 is a configuration diagram schematically showing an electric motor control circuit in which the motor control circuit according to the second embodiment of the present invention is used for an electric lawnmower, a power tool, or the like.

[Explanation of symbols]

 Reference Signs List 1 motor 2 FET 3 rotation pulse generation means 4 rotation pulse detection circuit 5 integration circuit 6 overload detection circuit 7 speed setting circuit 8 FET drive circuit 9 relay 10 flip-flop circuit 11 switch 12 DC power supply 13 reference value variable means

Continued on the front page (72) Inventor Naoya Hida 1-4-1 Chuo, Wako-shi, Saitama Pref.

Claims (2)

[Claims] 1. A motor, a switch provided in an energizing circuit for the motor, a rotation speed detector for detecting a rotation speed of the motor, a rotation speed setting circuit of the motor, and a rotation speed detector. Control means for comparing the detected motor speed with the set speed of the speed setting circuit to control ON / OFF of the switch means; bypass means provided in parallel with the switch means; And a power supply switching means for turning on the bypass means when is less than or equal to a predetermined value. 2. The motor control circuit according to claim 1, further comprising a set speed variable means for changing a set speed of said speed setting circuit.