JPS627785B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a speed command device for an electric motor, and more particularly to a device that can directly convert the manipulated variable of an operating means into a digital signal to issue a speed command without first converting it into an analog signal as in the prior art. For devices such as sewing machines that need to change operating speed according to operator operations, it is convenient to make the speed of the electric motor that drives the device variable. A control device and a speed command device are provided for giving a speed command to the control device in accordance with an operator's operation. Among these, the motor control device expresses the speed value as a digital quantity and processes it digitally to control the firing angle of the thyristor in the power supply circuit, as shown in Japanese Patent Application No. 53-69433. Digital controllers have already been developed. Digital control devices are highly valued because they are not affected by temperature changes or voltage fluctuations like analog control devices, and they are easy to use in combination with microcomputers. However, as for a speed command device for giving a speed command to this motor control device, there is still no known completely digital speed command device. In other words, in conventional speed command devices, the amount of operation of an operating member such as a speed control pedal by an operator is first converted into an analog signal such as a voltage using a sliding resistor, etc.
This was then converted into a digital signal by an analog-to-digital converter and input to the motor control device. As mentioned above, digital control devices are not affected by temperature changes or voltage fluctuations and can perform stable control operations, but the device that provides speed commands, which is the basis of the device, includes analog circuitry. If so, its value will be halved. This is because this analog circuit portion is affected by temperature changes and voltage fluctuations, and it is difficult to say that the speed command value itself is accurate. Moreover, a device that first converts the signal into an analog signal and then converts it into a digital signal has a disadvantage that the structure is complicated and the cost is high. The present invention eliminates these drawbacks of the prior art,
The present invention has been made with the aim of enabling more accurate motor control, and the motor speed command device according to the present invention is capable of (a) being operable in both forward and reverse directions to command the speed of the motor; (b) a moving body capable of moving in both forward and reverse directions according to the operation of the operating means; (c) a stationary member disposed near the moving body; and (d) a moving body. (e) A large number of detected parts supported on the other side of the moving body and the stationary member, and (e) a large number of detected parts provided on either one of the moving body and the stationary member along the relative movement direction between the moving body and the stationary member; two detectors that detect a detected part and generate first and second detection signals, and whose positions are set relative to each other such that both detection signals have a phase difference; (g) determining whether the first detection signal is generated earlier or later than the second detection signal; and (g) determining whether the first detection signal is generated earlier or later than the second detection signal, and the determination result. Accordingly, it is configured to include a control means for causing the counting means to selectively perform an addition operation and a subtraction operation. As described above, the present invention enables the speed command signal to be generated by digitally processing the amount of operation of the operating means by the operator from the beginning, without first converting it into an analog signal as in the conventional method. To provide a speed command device that operates stably and accurately without being affected by noise such as changes in environmental temperature or fluctuations in power supply voltage, has a simple configuration and can be manufactured at low cost, and is driven by an electric motor such as a sewing machine. This has an excellent effect of reducing the cost of the device and making the speed control accurate. Further, according to the present invention, it is possible to give substantially continuous speed commands by reducing the interval between each speed command value, but for example,
It is also possible to give speed commands in steps at relatively wide intervals, such as 100 rpm, 200 rpm, etc., and this feature is particularly useful in this case. EMBODIMENT OF THE INVENTION Hereinafter, one embodiment in which the present invention is applied to a speed command device for an electric sewing machine will be described in detail based on the drawings. What is shown in FIGS. 1 and 2 is a pedal-type controller 1 that is operated by an operator in both forward and reverse directions to control the speed of a sewing machine. The controller 1 mainly includes a base 2, a pedal 3, a sector 4, and a detection section 5. The base 2 and the pedal 3 are pivotally connected to each other by a pin 6 at an intermediate portion, and coil springs 7 and 8 are installed between the front and rear ends, respectively, as shown in FIG. As shown in FIG. 2, the pedal 3 is stabilized in a state in which both the front end 3a of the pedal 3 can be depressed (this is called front depression) and the rear end of the pedal 3 can be depressed (this is called rear depression). Several protrusions 2a are made to stand upright on the base 2, and a support plate 9 is fixed onto them.
A sector 4 is rotatably attached to the lower surface of the support plate 9 by a shaft 11. The sector 4 is biased to rotate in a fixed direction (counterclockwise in FIG. 2) by a torsion coil spring 15 held on the shaft 11. The projection 16 stops the slit 4c at a neutral position (non-operating position), that is, at a position where the slit 4c exactly matches the photo switch 14. The cam protrusion 16 projects downward from the support plate 9 through an opening 9a formed in the support plate 9, and contacts a cam follower 17 formed integrally with the sector 4 at the inclined cam surface 16a. In response to the front depression, the sector 4 is rotated clockwise in FIG. 2, and in response to the rear depression, the sector 4 is rotated counterclockwise. A large number of slits 4a are provided radially at equal intervals on a circular arc centered on the axis of the shaft 11 of the sector 4. A slit 4b for detecting post-depression is provided on the same arc as these slits 4a but a little apart from the slits 4a, and a non-operating slit 4b is provided between the slits 4a and 4b and closer to the shaft 11. A slit 4c is provided for detecting the state (the state in which the pedal 3 is not depressed). A detection unit 5 for detecting the amount and direction of movement of the sector 4 in cooperation with these slits 4a, 4b, and 4c is fixedly attached to the support plate 9. As shown in an enlarged view in FIG. 3, the detection unit 5 is equipped with two photo switches 12 and 13 at positions corresponding to the slits 4a and 4b, which are offset by a small distance in the direction of movement of the slits 4a and 4b.
One photo switch 14 is placed at the position corresponding to c.
It is equipped with In this embodiment, the pedal 3 constitutes an operating means, and the sector 4 serves as a movable body that can be moved according to the operation of the operating means, and also supports a support plate 9.
constitute the stationary members. The slits 4a and 4b are provided along the direction of relative movement between the movable body and the stationary member, and form the detected parts detected by the photo switches 12 and 13, which are two detectors, while the slit 4c detects the non-operating position. This constitutes the detected part that is detected by the photo switch 14 as a device. These photo switches 12, 13, 14 are the fourth
Connected to the circuit shown in the figure. Each photo switch has a light emitting diode 12a, 13a, 1
4a and phototransistors 12b, 13b, 14
When the slits 4a, 4b, 4c of the sector 4 match these and the light from the light emitting diode 12a etc. is incident on the phototransistor 12b etc., the phototransistor 12b etc. becomes conductive, and the phototransistor 12b etc. becomes conductive. 12b, 13b, 14
A high level (hereinafter referred to as "1") signal voltage-divided by B and variable resistors 21, 22, and 23 is output to output lines 24, 25, and 26, respectively. The output signals of the photo switches 12 and 13 output to the output lines 24 and 25 are respectively output to the inverter 2.
7, 28 and inverters 29, 30, the input terminal 1D of a D-type flip-flop (latch) 31
and input into 3D. D-type flip-flop 3
1 is reset by a signal that falls to a low level (hereinafter referred to as "0") for a certain period of time when the power is turned on, and is sent to the clock terminal CK from the oscillator OSC.
Every time a 1MHz clock pulse is input, input terminal 1 is output in response to the rising edge of the clock pulse.
The input signals applied to D, 2D, 3D, and 4D are read and the state is maintained until the next clock pulse is input. D type flip-flop 31
The output terminal 1Q of is connected to the input terminal 2D of the D-type flip-flop 31 itself, and also to the select terminal S0 of the multiplexer 32. The output terminal 3Q is similarly connected to the input terminal 4D and the select terminal S1. Other output terminals 2Q, 2, 4 of the D-type flip-flop 31
Q, 4 are two data terminals 1C2, 2C0, 1C1, 2C of the multiplexer 32, respectively.
3, 1C0, 2C1, 1C3, and 2C2. As a result, the multiplexer 32 sends the input signals of the data terminals 1C and 2C whose numbers are shown in the following table to the respective output terminals 1C and 2C corresponding to the combination of the selection input signals to the selection terminals S0 and S1.
It will be output from Y and 2Y.

[Table] Output signals from output terminals 1Y and 2Y of multiplexer 32 are inverted by inverters 33 and 34, respectively, and input to input terminals UP and DN of counter 35. The counter 35 adds 1 each time the pulse signal input to the input terminal UP rises, and
Each time the pulse signal input to DN rises, 1 is subtracted, and the count contents are sent to the output terminal Q.
1, Q2...Output from Q8. This counter 35 is reset by an output signal from the photo switch 14 for detecting the non-operating (neutral) position. In other words, photo switch 14
The output signal is applied to the reset terminal RT of the counter 35 via the inverters 36, 37 and the OR gate 38 (this circuit is referred to as a first reset circuit), and the counter 35 is reset based on this. There is also a J-K in the or gate 38.
The output terminal of the type flip-flop 39 is connected via an inverter 41, and is also reset by the output signal of this circuit (which is referred to as a second reset circuit). The JK type flip-flop 39 is set when the output signal of the inverter 36 rises to "1", and is reset by the rise of a pulse signal that temporarily falls to a low level when the power is turned on. It's getting old. The counter 35 constitutes an addition/subtraction means that performs a counting operation every time a detection signal is generated from the photo switches 12 and 13 as two detectors, and the inverters 27, 28, 29, 30, the D-type flip-flop 31, the multiplexer 32, and the inverter 33, 34, etc. constitute a control means for controlling the addition/subtraction means. The output signal of the counter 35 is input to the motor control device 42 as a speed command signal. The motor control device 42 is connected to the output of a speed calculation circuit 43 that calculates the rotation speed of the DC motor based on the output signal of the tachogenerator TG, which is directly connected to the DC motor DM and emits a pulse signal with a frequency proportional to the rotation speed of the DC motor DM. The signal is compared with the speed command signal from the counter 35, and the firing angle of the thyristor of the DC motor DM power supply circuit 44 is controlled so that the difference between the two approaches zero. Next, the operation of the apparatus configured as above will be explained. When the pedal 3 is not pressed forward or backward, the slit 4c is in a position that matches the photo switch 14, so if the sewing machine is turned on in this state, the photo switch 14
The output signal of inverter 3 becomes “1”, and this
Counter 35 via 6, 37 and or gate 38
is input to the reset terminal RT of the counter 35, and the counter 35 is kept in the reset state. In addition, photo switch 1
Since the output signals of 2 and 13 remain “0”,
The output signals of the D-type flip-flop 31 are all "0", and therefore the output signals of the output terminals 1Y and 2Y of the multiplexer 32 are both "0", and the output signals of the input terminals UP and DN of the counter 35 are both "0". A signal of "1" is input, but since the counter 35 is kept in the reset state as described above, its output signal remains (0, 0...0), and the motor control device 42 The thyristor of the power supply circuit 44 is not fired at all, and the DC motor DM does not rotate. If the pedal 3 is depressed when the sewing machine is powered on, the output signal of the photo switch 14 is "0", the output signal of the inverter 36 is "1", and this signal "1" is the output signal of the J-K flip-flop 39. Input to input terminal. On the other hand, since the input signal at the K input terminal of the JK flip-flop becomes "0" for a certain period of time after the power is turned on, the JK flip-flop 39 is set and its output signal becomes "0", which is inverted by the inverter 41. becomes “1” and is input to the reset terminal RT of the counter 35 via the OR gate 38, and the counter 3
5 is also reset. Then, when the pedal 3 is released and the output signal of the photo switch 14 becomes "1", the JK flip-flop 3
The output signal of the J input terminal of the J-K flip-flop 39 becomes "0", but at this time the signal that temporarily became "0" has already returned to "1", so the J-K flip-flop 39 is reset and its The output signal becomes "1". Therefore, the signal input to the OR gate 38 via the inverter 41 becomes "0", but
At this time, the OR gate 38 is passed through the inverter 37.
Since the signal applied to the counter 35 is "1", the counter 35 remains in the reset state.
As is clear from the above explanation, the second reset circuit including the JK flip-flop 39 and the inverter 41 is configured such that when the power is turned on with the pedal 3 depressed, the DC motor DM is equal to the amount of depression of the pedal 3. This is provided to prevent rotation at unrelated speeds. That is, when the pedal 3 is depressed, the photo switch 14
Since the first reset circuit consisting of the inverters 36 and 37 does not reset the counter 35, if the second reset circuit is not provided, the counter 35 will not be reset when the power is turned on with the pedal 3 depressed. First, since it is not known what kind of output signal will be output, it is possible that the DC motor DM will suddenly start rotating at high speed as soon as the power is turned on, which is extremely dangerous, but the second reset circuit eliminates this danger. It is being avoided. If the power is turned on while the pedal 3 is depressed, the sewing machine will not start unless the pedal 3 is released and then depressed again. If the counter 35 is maintained in the reset state as described above and the pedal 3 is pressed forward from the state where the DC motor DM is stopped, the sector 4
is rotated clockwise in FIG. 2, and the slit 4a moves in the direction of arrow W in FIG. 3 relative to the photo switches 12 and 13. As a result, each time one slit 4a passes through the photo switches 12 and 13, one pulse signal with a constant phase difference is sent to the D-type flip-flop 3, as shown as 1D and 3D in the left half of FIG.
It is input to input terminals 1D and 3D of 1. and D
This input signal is latched in response to the rising edge of the clock pulse to the clock terminal CK of the type flip-flop 31. In this embodiment, the frequency of the clock pulse is extremely high, 1 MHz, as described above, so Specifically, when pulse signals are input to the input terminals 1D and 3D, similar pulse signals are output to the output terminals 1Q and 3Q. Since the output signals of the output terminals 1Q and 3Q are input to the input terminals 2D and 4D of the flip-flop 31 itself, the output terminal 1
The pulse signals output to Q and 3Q are latched in response to the rising edge of the next clock pulse, and outputs are output to output terminals 2Q and 4Q, respectively, as shown with the symbols 2Q and 4Q on the left half of Figure 5. Terminals 1Q, 3Q
A pulse signal delayed by one period of the clock pulse is output. Output terminal 1 of the D-type flip-flop 31
The output signals of Q and 3Q are input to the select terminals S0 and S1 of the multiplexer 32, and the multiplexer 32 selects the data terminals 1 of the numbers shown in the previous table according to the combination of these select input signals.
The input signals to C and 2C are output to output terminals 1Y and 2C, respectively.
Output to 2Y. Therefore, the output signals of the output terminals 1Y and 2Y are as shown in the left half of FIG. 5 with the symbols 1Y and 2Y attached. That is, every time one slit 4a passes through the photo switches 12, 13, 4 slits are output from the output terminal 1Y of the multiplexer 32.
pulse signals are output, and not a single pulse signal is output from the output terminal 2Y. The output signal of multiplexer 32 is sent to inverter 3
3 and 34 and input to the input terminals UP and DN of the counter 35, the input signal to the input terminal UP remains "1" and does not change, and the input signal to the input terminal UP is input to the slit 4a. Every time one passes, it rises from "0" to "1" four times, and the count of the counter increases by four. As a result, the speed command value given to the motor control circuit 42 increases, the firing phase angle of the thyristor in the power supply circuit is advanced, and the rotational speed of the DC motor DM is increased to the speed command value. Also, when the pedal 3 is released, the 5th pedal
As shown in the right half of the figure, the D-type flip-flop 3
A pulse signal having a phase difference opposite to that when the pedal 3 is depressed is input to the input terminals 1D and 3D of the multiplexer 32, and as a result, the output terminal 2 of the multiplexer 32
Four pulse signals are output to Y each time one slit 4a passes, and not a single pulse signal is output to 1Y. Therefore, counter 35
The counting content is 4 every time one slit 4a passes.
As a result, the speed command value to the motor control circuit 42 is decreased, and the rotational speed of the DC motor DM is decreased. The front depression of the pedal 3 has been explained above, but the rear depression will now be explained. When the pedal 3 is not operated, the counter 35 is reset as described above and its output signal is (0, 0...0), but from this state, when the pedal 3 is depressed backwards, the slit is activated. 4b passes through photo switches 12 and 13 in the opposite direction,
Four pulse signals are input to the input terminal DN of the counter 35, and in response to the rising edge of the first pulse signal, the output signal of the counter 35 is (0, 0...
0) to (1, 1...1). Therefore, if we do not use this signal (1, 1...1) as the speed command value corresponding to the above-mentioned front depression (a value smaller than that is set as the maximum speed command value), then this (1, The signal 1...1) can be taken as a signal specific to the rear depression of the pedal 3, and this unique signal can be used, for example, as an operation command signal for a thread cutting device of a sewing machine. It should be noted that in the embodiment described in detail above, the movement of the pedal 3, which is the operator operating member, is converted into a larger movement of the sector 4, which is a type of moving body, by the cam protrusion 16 and the cam follower 17. The range in which the slit 4a etc. can be provided is widened,
This has the advantage of making it easier to process the slits 4a, etc., but it is also possible to directly fix the movable body and the detector that detects the amount of movement of the movable body to the stationary member such as the base 2 and the operator-operated member such as the pedal 3, respectively. It is also possible to do so. Furthermore, the detected part provided on the moving object and the detector for detecting it are not limited to the slit and photo switch mentioned above, but also the use of a combination of a magnetic material and a magnetoresistive element, a combination of a magnet and a coil, etc. In other words, the number of first and second detection signals corresponding to the amount of operation of the operating means (including operator operating members, movable objects, etc.) is generated respectively, and the signals are generated in accordance with the forward or reverse operation of the operating means. Therefore, it is sufficient that the first detection signal can be generated earlier or later than the second detection signal. Furthermore, there are many modifications to the circuit for processing the first and second detection signals to generate the speed command signal, although they will not be illustrated individually.
In short, there is an addition/subtraction counting means that performs a counting operation each time at least one of the first detection signal and the second detection signal is generated, and whether the first detection signal is generated earlier than the second detection signal or Any device can be adopted as long as it is equipped with a control means for determining whether the count is generated late and controlling the counting operation so that the addition/subtraction means selectively performs an addition operation or a subtraction operation according to the determination result. That's why.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing a mechanical part of a speed command device according to an embodiment of the present invention. FIG. 2 is a perspective view of FIG. 1, and FIG. 3 is an explanatory diagram showing an enlarged detector portion thereof. FIG. 4 is a circuit diagram showing the electronic circuit portion of the device shown in FIG.
FIG. 5 is a time chart for explaining the operation of the circuit shown in FIG. 4. 1: Controller, 2: Base, 3: Pedal,
4: Sector, 4a, 4b, 4c: Slit, 5:
Detection unit, 12, 13, 14: Photo switch, 1
6: Cam projection, 17: Cam follower, 31: D-type flip-flop, 32: Multiplexer, 3
5: Counter, 42: Motor control device, 44: Power supply circuit, DM: DC motor.

Claims (1)

[Scope of Claims] 1. An operating means that can be operated in both forward and reverse directions to command the speed of an electric motor, a movable body that can be moved in both forward and reverse directions according to the operation of the operating means, and a vicinity of the movable body. a stationary member disposed on the movable body and the stationary member; a large number of detected portions disposed on either the movable body and the stationary member along the direction of relative movement between the movable body and the stationary member; two components supported on the other side of the member, detecting the plurality of detected parts to generate first and second detection signals, and having mutual positions set such that both detection signals have a phase difference. a detector; an addition/subtraction counting means that performs a counting operation each time at least one of the two detection signals is generated; and a means for determining whether the first detection signal is generated earlier or later than the second detection signal. and a control means for making the counting means selectively perform an addition operation and a subtraction operation according to the discrimination result, and the counting contents of the counting means are used as a speed command value of the electric motor. A speed command device for an electric motor. 2. Either one of the movable body and the stationary member is provided with a detected part different from the plurality of detected parts, and the other is provided with a detected part that is detected when the operating means is in a non-operating position. 2. A speed command device for an electric motor according to claim 1, further comprising a non-operation position detector which generates a non-operation signal, and wherein said addition/subtraction counting means is reset in response to the non-operation signal.