JPS6129232B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a speed control device for an electric motor.

A conventional motor speed control device compares a set speed signal corresponding to a desired speed with a speed signal corresponding to the actual speed of the motor, and determines the conduction angle of a thyristor interposed in the motor main circuit according to the speed of the motor. Generally, the configuration is such that feedback control is performed so that the speed changes in a direction that matches the set speed. In the case of such a method, conventionally, the set speed signal and the speed signal express the speed value with an analog amount of DC voltage,
Since it is an analog circuit system in which the firing of the thyristor is controlled by processing these in an analog manner, it has the disadvantage that it is susceptible to temperature and voltage fluctuations and that it is difficult to obtain a stable rotational speed.

Therefore, the present invention eliminates the influence of temperature and other factors by controlling the speed of the electric motor using a digital circuit, thereby making it possible to obtain a stable rotational speed and also to enable speed control using a so-called microcomputer. The object is to provide a speed control device.

EMBODIMENT OF THE INVENTION Hereinafter, the specific content of this invention will be explained by each Example with reference to drawings. 1 to 7 show a first embodiment. In addition, in Figures 1 and 2, the symbols A, B, C, etc. are shown inside the circular marks, but this means that those with the same symbols are connected to each other. It is. FIG. 1 shows a motor drive circuit 1, and FIG. 2 shows a speed control circuit. In the motor drive circuit 1, 2 is one AC bus bar connected to one end of the AC power supply 3, and 4 is the other AC bus bar connected to the other end of the AC power supply 3 via the power switch 5. A rectifying bridge circuit 10 consisting of two diodes 6, 7 and semiconductor switch elements such as two thyristors 8, 9 is connected between the bus bars 2, 4, and a motor 11 is connected between the DC output terminals of this bridge circuit 10. There is. 12 is an ignition circuit, which includes a transistor 13, a resistor 14, a pulse transformer 15 and a freewheel diode 1.
6, and a high level (positive potential, meaning logical value "1") trigger pulse, which will be described later, is applied to the base of the transistor 13 via line 17.
When SO is received, an ignition pulse is supplied to the thyristors 8 and 9 via the pulse transformer 15 to turn them on. 18 is a step-down transformer connected between both AC buses 2 and 4, and a full-wave rectifier circuit 20 is connected to the secondary winding 19 of this transformer.
The DC voltage output from the full-wave rectifier circuit 20 is stabilized by a stabilizing circuit 21, and is then converted into a DC voltage Vcc and supplied to the power input section of each part of the speed control circuit. Next, the speed control circuit will be explained. The basic configuration of the speed control circuit shown in the drawings is as follows: with a pulse width proportional to the actual speed of the electric motor 11 and the synchronous pulse S
a speed pulse generation circuit 23 for generating a speed pulse S3 temporally related to the generation of speed pulse S3; and a standard for generating a reference pulse S4 (in this embodiment, the pulse period is 0.05 msec) at a predetermined high frequency. a pulse generation circuit 24; an AND circuit (first gate circuit) 25 that passes the reference pulse S4 while the speed pulse S3 is being generated; and a manual circuit for setting the speed of the electric motor 11 to a desired speed. Speed selection switch (speed setting means) 26 to be operated
a first comparison circuit 27 that compares the number of speed setting pulses corresponding to the set speed set according to the operation of the speed selection switch 26 and the number of reference pulses S4 that have passed through the AND circuit 25; A start command signal S5 is generated when the actual speed of the electric motor 11 is lower than a predetermined reference speed, and a return command signal S6 is generated when the actual speed is higher than the reference speed.
a command signal generating circuit 28 that generates a command signal generating circuit 28, and an initial pulse number predetermined based on the period of the AC voltage and the frequency of the reference pulse S4,
a first counting circuit 29 consisting of an addition/subtraction counter that is set before the start of operation;
a first calculation pulse generation circuit 30 which supplies a subtraction pulse S7 to the first counting circuit 29 in response to the synchronization pulse S2 while the signal S5 is being generated; According to the comparison result of the comparison circuit 27, the first counting circuit 2
9, a second arithmetic pulse generation circuit 31 that supplies an addition pulse S8 or a subtraction pulse S9, and an AND circuit that is opened in response to the synchronization pulse S2 and passes the reference pulse S4 from the reference pulse generation circuit 24. (second gate circuit) 32 and a subtraction counter that counts the reference pulses that have passed through the AND circuit 32 and generates a coincidence signal S1 when the number of reference pulses matches the count content of the first counting circuit 29. and the above-mentioned ignition circuit 12 which responds to the coincidence signal S1.

Next, to explain in detail the above configuration and related configurations, the circles shown at the input terminals of each counting circuit and one-shot multivibrator in Fig. 2 mean a negation circuit that inverts the signal level. . In addition, the one-shot multivibrator is
If the input of one input terminal A having a negation circuit is held at a low level (negative potential, corresponding to a logical value (10)), the input of the other input terminal B is held at a high level. (It is a positive potential and corresponds to the logical value (1)), one high-level pulse is output from the Q output terminal, and the input of the input terminal B is held at a high level. It is configured to output one high-level pulse from the Q output terminal the moment the negative circuit input of input terminal A becomes low level, and the output terminal has a signal that is inverted from the output signal from the Q output terminal. A signal is now being output.

Now, the synchronization circuit 22 includes a comparator 34,
The output voltage of the potentiometer 35 is applied to the positive input terminal, and the full-wave rectified voltage S10 as shown in FIG. 4 outputted from the full-wave rectifier circuit 20 is applied to the negative input terminal. By comparing these two inputs, a synchronizing pulse S2 as shown in FIG. 4 is output at a phase angle near the approximately zero value of the AC voltage. This synchronization pulse S
The second pulse width can be set to a desired value by adjusting the potentiometer 35. 36 is a rotation signal generator that generates a rotation signal 11 (see FIG. 4) with a pulse width proportional to the rotation speed of the electric motor 11, and as shown in FIG. A slitted disk 39 that rotates integrally with the output shaft of the electric motor 11 (in this embodiment, a sewing machine motor is assumed) is interposed between the two, and as the slitted disk 39 rotates, the output from the phototransistor 38 is generated. The on/off signal is amplified by a transistor 40 and outputted to a line 41 as a rotation signal S11. In this embodiment, one rotation of the slitted disc 39 generates 120 pulses. As will be understood later, this rotation signal S11 is exactly the same as the speed pulse S3 in terms of the pulse width and phase of one pulse, and is only the speed pulse S11.
3 differs only in that it occurs or does not occur depending on the time relationship with the synchronizing pulse S2. Reference numeral 42 denotes a pulse number setting circuit, and by operating the speed selection switch 25, a speed setting pulse number Pan corresponding to the set speed is set. In this embodiment, the speed of the electric motor 11 is set to the seventh speed.
As shown in the figure, super low speed (100rpm), low speed (200rpm), medium speed (500rpm), high speed (1000rpm)
It is possible to set the speed selection switch 26 to four stages of terminals 26a, 26b, 26.
By setting the speeds to c and 26d, the speed can be set in the above order, and in this case, the speed setting pulse number set in the pulse number setting circuit 42
Pan is determined to be 50, 25, 10, and 5, respectively, in the order of speed settings, and one speed setting pulse number Pan is transmitted to one input terminal B of the first comparator circuit 27 via a line 43. It is now supplied as a 6-bit binary code. On the other hand, the firing phase angles (turn-on start times) of the thyristors 8 and 9 corresponding to the above-mentioned set speeds of the electric motor 11 are input to the second counting circuit 33 between the generation of the synchronizing pulse S2 and the generation of the coincidence signal S1. The number of reference pulses S4 (ie, borrow condition) and the pulse width of the rotation signal S11 at each set speed are determined in advance as shown in FIG. 7, respectively. Now, the pulse generating circuit 23 generates a rotation signal S
11 and the synchronization pulse S2, the speed pulse S
3, which is a JK type flip-flop circuit 44, 45 and an AND circuit 4.
6, an OR circuit 47, and inverters 48 and 49. The flip-flop circuits 44 and 45 of this pulse generation circuit 23 become trigger inputs when a falling edge of the pulse is input to the input line of the T terminal, and the Q terminal is input while a low level signal is input to the input line of the clear terminal CLR. In general, it becomes a low level and is forced into a reset state, and can only respond to the trigger input of the T terminal while the input line of the clear terminal CLR is at a high level, and is always reset once when the power is turned on. As can be understood by considering the principle of operation of the pulse generating circuit 23, the operation of the pulse generating circuit 23 is as shown in FIG. Note that the small numbers shown in FIG. 5 represent the order of changes in operation. In this way, the pulse generating circuit 23 outputs only one complete pulse to the line 50 as the speed pulse S3, excluding the incomplete pulse shown by S11a in FIG.
The reason for doing this is that the pulse width of the speed pulse S3 corresponds to the rotational speed information of the electric motor 11,
This is because, in this embodiment, since the ignition phase control as speed control is performed every half wave of the full-wave rectified voltage S10, the speed information only needs to be obtained once every time the synchronization pulse S2 is generated. 51 is a speed information circuit,
Two counting circuits 52a and 5 consisting of addition counters
2b, AND circuits 53a and 53b, and an inverter 54. The command signal generation circuit 28 is composed of a second comparison circuit 55 and a flip-flop circuit 56, and one input section E of the second comparison circuit 55 is connected to the counting circuit 52.
The count contents Pbn of a and 52b are always supplied via a wired OR circuit 57.
The other input section F of the second comparison circuit 55 is always supplied with specific numerical information S50 of (50), which is fixedly preset as a reference value in the numerical information circuit 58. . In this embodiment, the numerical value (50) of the specific numerical information S50 is equal to the speed setting pulse number Pan set in the pulse number setting circuit 42 when the speed selection switch 26 sets the ultra-low speed. Further, 59 is another numerical information circuit, in which startup start numerical information S148 of (148) is preset as the initial pulse number, and this is supplied to the preset input section PN of the first counting circuit 29. It's becoming like that. As will be understood later, the numerical value (148) of the starting numerical value information S148 corresponds to the numerical value required to start the electric motor 11 at a firing angle of 160 degrees of the thyristors 8 and 9. 60 is an auxiliary synchronous pulse generation circuit, which is a one-shot multivibrator 60
a and 60b, and its operation is performed as shown in FIG. That is, the first-stage one-shot multivibrator 60a is triggered at the rising edge of the synchronizing pulse S2 every time it receives the synchronizing pulse S2.
2, and at the falling edge of this pulse S12, the next stage one-shot multivibrator 60b generates the output signal S13 shown in FIG. Other detailed configurations will be made clear in the following explanation of the operation.

Now, before starting the electric motor 11, the power source switch 5 is turned on. As a result, all flip-flop circuits and counting circuits are reset and cleared to zero counting contents, respectively.
The reference pulse generation circuit 24 starts generating the reference pulse S4, and furthermore, the comparator 34 of the synchronization circuit 22 starts generating the synchronization pulse S2. On the other hand, after or before turning on the power switch 5, the speed selection switch 26 is set to the terminal 26a corresponding to ultra-low speed. Then, the speed setting pulse number Pan of (50) is set in the pulse number setting circuit 42, and this is always supplied to one input section B of the first comparison circuit 27. After the above operation, the time TS (fourth time) is set to start the electric motor 11.
(see figure), press the automatic return type start/stop switch 61 to temporarily close it. As a result, the one-shot multivibrator 62 is triggered by its A terminal input line temporarily changing to a low level, and the output of that terminal changes to a low level, and the falling signal at this time is transmitted to the first counting circuit. Since it is supplied to the load terminal LD of 29,
The activation start numerical information S148 of (148) of the numerical information circuit 59 is set as an initial value in the first counting circuit 29, and 148 initial pulses are stored and the count content becomes (148). Further, the falling signal outputted from the one-shot multivibrator 62 is applied to the T of the JK type flip-flop circuit 63.
Also supplied to the terminal to reverse it from the reset state to the set state. Then, the line 63a changes from high level to low level. On the other hand, since the output line 65 of the one-shot multivibrator 64 forming part of the ignition circuit 12 is currently at a low level, as will be understood later, the output line 67 of the NOR circuit 66 is As a result of the change to a low level, the level becomes high, and therefore, the clear terminal CLR of the JK type flip-flop circuit 68 becomes high level. On the other hand, at time TP when the start/stop switch 61 is pressed, the electric motor 11 is not being driven and the slit disk 39 is in a stopped state, and the rotation signal generator 36 outputs its rotation signal S11.
maintains a high or low level of

In this embodiment, the following description will be made assuming that the level of the rotation signal S11 from the rotation signal generator 36 is at a low level as shown in FIG. The rotation signal S11 is input to one input terminal of the AND circuit 53a, and is also input to the clear terminal of the counting circuit 52a to clear the counting circuit 52a.
It is also inputted to one input terminal of the AND circuit 53b via the inverter 54. As shown in FIG. 4, while the rotation signal S11 is at a low level, the AND circuit 53a is closed and the AND circuit 53a is closed.
Reference pulse S4 supplied to the other input terminal of a
The AND circuit 53b is opened to allow the reference pulse S4 supplied to the other terminal to pass, thereby preventing the reference pulse S4 from being supplied to the input terminal of the counting circuit 52a.
2b, and its counting circuit 52b adds and counts the supplied reference pulse S4. The count content Pbn of the counting circuit 52b that changes every moment is compared with specific numerical information S50 of (50) received from the numerical information circuit 58 in the second comparing circuit 55. This comparison is performed in synchronization with the AC power supply voltage so that it is performed every half wave of the full-wave rectified voltage S10. That is, the flip-flop circuit 56 receives the output signal S13 of the one-shot multivibrator 60b.
is cleared each time it is input to the clear terminal, and if the level of the comparison output line 71 is high or changes from low to high within the clear period, the high level signal is cleared. It stores and retains information. As mentioned above, since the electric motor 11 is in a stopped state, the counting circuit 5
The second comparison circuit 55 outputs a high level signal under the condition that the count content Pbn of 2b becomes larger than the numerical information S50 from the numerical information circuit 58 and Pbn>S50.
outputs a high level signal from its output G to the comparison output line 71, and the flip-flop circuit 56 receives the high level signal at its set terminal and is set, making its Q output terminal high level. This high level signal is sent to the AND circuit 7 as a start command signal S5.
is supplied to one input terminal of 2.

Now, if the synchronization pulse S2a is first generated at time _T0 shown in FIGS. 4 and 6 after the start/stop switch 61 is pressed, the one-shot multivibrator 60a is triggered by the rising edge of the synchronization pulse S2a. A pulse S12 is generated from the Q output terminal of , which is inputted to the other input terminal of the AND circuit 72 and supplied to the subtraction input terminal of the first counting circuit 29 as a subtraction pulse S7. Thereby, the first counting circuit 29 subtracts one from the initial value (148) and changes the count to (147). Then, the one-shot multivibrator 60b is triggered by the fall of the pulse S12 from the one-shot multivibrator 60a, and the output signal S13 is triggered.
is output, and the load terminal LD of the second counting circuit 33
When the falling edge of the output signal S13 is inputted, the counting circuit 33 stores the numerical value (147) which is the count content of the first counting circuit 29 as an initial value via the preset input section PN. After this, time T ₁
When the synchronizing pulse S2a falls, the flip-flop circuit 68 is activated by the falling signal.
is inverted to the set state, and the output signal S14 (see FIG. 4) at its Q terminal becomes high level. Then, the reference pulse S from the reference pulse generation circuit 24
4 passes through an AND circuit 32 which is fed via a subtraction input line 69 to a second counting circuit 33. The second counting circuit 33 subtracts one value from the preset initial value (147) each time it receives the reference pulse S4 that has passed through the AND circuit 32, and counts (147) until the count becomes zero. The borrow terminal changes from low level to high level in synchronization with the falling of the reference pulse S4 when
is output. Then, a high-level trigger pulse SOa is output from the one-shot multivibrator 64 to the line 65, and based on this, an ignition pulse is generated from the pulse transformer 15 of the ignition circuit 12, turning on the thyristors 8 and 9. This turn-on time is determined by the second counting circuit 33 (147).
It corresponds to the number of pieces counted, and the phase angle is approximately 160.
corresponds to degrees. In this way, the electric motor 11 is first started. On the other hand, when a trigger pulse SOa is output to the line 65 based on the coincidence signal S1, the output of the NOR circuit 66 is set to a low level only during this period, and the flip-flop circuit 68 is cleared by this low level signal. This clearing time is illustrated as T ₂ in FIG. When flip-flop circuit 68 is thus cleared and its Q terminal goes low, reference pulse S4 is prevented from passing through AND circuit 32. That is, after this, the AND circuit 32 blocks input of the reference pulse S4 to the second counting circuit 33 until the next synchronizing pulse S2b is generated.

As described above, the electric motor 11 is started and the slitted disc 39 begins to rotate, and the time T shown in FIG.
3, when the rotation signal S11 from the rotation signal generator 36 rises from a low level to a high level, the high level rotation signal S11 is input to one input terminal of the AND circuit 53a and is counted via the inverter 54. The signal is input to the clear terminal of the circuit 52b, and the counting circuit 52b is cleared. Then, the reference pulse S4 inputted to the other input terminal of the AND circuit 53a passes through the AND circuit 53a and is supplied to the counting input terminal of the counting circuit 52a, and the counting circuit 52a receives the passed reference pulse S4. Add and count. Counting contents of the counting circuit 52a
Pbn is determined by the numerical information S in the second comparison circuit 55.
50, but the comparison circuit 55 is Pbn>
Since the level of the output section G is held at a low level until the condition of S50 is satisfied, the comparison output line 7
The level of 1 changes from high level to low level at time T3 and is maintained at a low level state. The flip-flop circuit 56 maintains the set state and continues to output the startup command signal S5 (high level signal) from its Q output terminal. Further, the output terminal of the flip-flop circuit 56 is held at a low level state and the feedback command signal S6 is not outputted, and the AND circuit 25a whose one input terminal is connected to the output terminal continues to be in a closed state.

Further, at the above-mentioned time T3, the JK flip-flop circuit 44 is set by the rise of the rotation signal S11 from the rotation signal generator 36, and the level of its Q output terminal changes from low level to high level as shown in FIG. A speed pulse S3 is then generated. While the speed pulse S3 is being generated, the reference pulse S4 from the reference pulse generation circuit 24 can pass through the AND circuit 25, but the passed reference pulse S4 is passed through the AND circuit 25 as described above.
5a is in the closed state, the AND circuit 25
cannot pass through a, and its AND circuit 25
The output signal S16 of the output signal a remains at a low level as shown in FIG. 4 and does not change. Next, when the second synchronizing pulse S2b is generated after time T3, the one-shot multivibrator 60a outputs the pulse S12 based on this pulse and inputs it to one input terminal of the AND circuit 72, which inputs the pulse S12 to the other input terminal of the AND circuit 72. Since the start command signal S5 (high level signal) is input to the input terminal of
, and supplies the subtraction pulse S7 to the subtraction input terminal of the first counting circuit 29, whereby the first counting circuit 29 subtracts 1 from the numerical value (147) that is the count content.
Subtract 1 and change the count to (146). After that, one-shot multivibrator 6
0b is generated as the output signal S13 as a load signal by the fall of the pulse S12, the second counting circuit 33 is preset with the value (146) that is the count content of the first counting circuit 29, and at the same time, the flip-flop circuit 56 receives the output signal S13 at its clear terminal and is cleared. continue,
The flip-flop circuit 68 is set at the fall of the synchronizing pulse S2b, and since the reference pulse S4 passes through the AND circuit 32, the second counting circuit 33
subtracts this and calculates (146) reference pulses S4
When receiving the match signal, it outputs a match signal S1 to the borrow output line 70. Therefore, thyristors 8 and 9 are
Since it is fired when the counting circuit 33 completes counting of (146) pieces, the reference pulse S4 takes about one cycle time longer than when it is fired when counting of (147) pieces is completed.
The conduction angle becomes longer, and the motor 11 is supplied with a correspondingly higher effective value voltage and speeds up. During the subtraction counting operation of the second counting circuit 33,
Counting circuit 52a input to second comparison circuit 55
When the count content Pbn becomes larger than the numerical information S50 and the level of the output part G of the comparison circuit 55 changes from a low level to a high level, the flip-flop circuit 56 is set and the AND circuit 25a is closed. The output signal of the AND circuit 25a differs depending on the relationship between the level change time t of the output section G and the generation time of the synchronization pulse S2b. That is, if the level change time t is earlier than the generation time of the synchronization pulse S2b, the flip-flop circuit 56 is cleared by the output signal S13 generated in synchronization with the synchronization pulse S2b, and then the second comparison circuit 55 is cleared. It is immediately set by the high level signal output from the terminal, and a low level signal is output from that terminal to close the AND circuit 25a. Conversely,
If the level change time t is later than the generation time of the synchronization pulse S2b, the level change time t, In other words, a high level signal (feedback command signal) is sent from the output terminal of the flip-flop circuit 56 to the AND circuit 25a for a short period of time until the flip-flop circuit 56 receives the high-level output signal from the second comparator circuit 55 and is set. is supplied, the AND circuit 25a is opened, and the reference pulse S4 that has passed through the AND circuit 25 is supplied to the addition count input terminal of the counting circuit 74 via the AND circuit 25a. However, as will be understood later, it should be taken into consideration that the second calculation pulse generation circuit 31 generates the addition pulse S8 or the subtraction pulse S9 in response to the fall of the speed pulse S3 output from the pulse generation circuit 23. For example, unless the falling edge of the speed pulse S3 is supplied to the second arithmetic pulse generation circuit 31, the first computation pulse is not affected by the change in the counting contents of the counting circuit 74, that is, the comparison result of the first comparator circuit 27. The count content of the counting circuit 29 of No. 1 is maintained at the numerical value (146). Furthermore, when the speed pulse S3 falls at time T4 shown in FIG.
6 is in the set state and a low level signal is output from its output terminal, AND circuits 75 and 76 which receive the low level signal at their input terminals are both closed and the comparison result from the first comparator circuit 27 is output. A blocking operation is performed to prevent the input pulse from being input to the second calculation pulse generation circuit 31. From the above explanation, the count content of the first counting circuit 29 is a numerical value (146) without being influenced by the relationship between the level change time t of the output section G of the second comparator circuit 55 and the generation time of the synchronization pulse S2b. is maintained.

After the electric motor 11 is started as described above, if the speed is lower than the speed corresponding to the specific numerical information S50 set in the numerical information circuit 58, the motor is operated based on the comparison output from the second comparison circuit 55. The flip-flop circuit 56 receives a high-level startup command signal S5 from the Q terminal every cycle CT (half wave of AC power supply voltage) of the synchronizing pulse S2 shown in FIG.
A pulse S12 is generated in synchronization with the synchronizing pulse S2 at the beginning of the next cycle CT following the cycle CT in which the activation command signal S5 is generated.
In response to this, a subtraction pulse S7 is supplied from the first calculation pulse generation circuit 30 to the first counting circuit 29,
The electric motor 11
The speed is gradually increased.

Now, the rotational speed of the electric motor 11 increases, and based on this, the counting contents of either of the counting circuits 52a and 52b
For the numerical information S50 set in the Pbn numerical information circuit 58, (S50=Pbn) or (S50
>Pbn), the second comparison circuit 5
The comparison output line 71 of 5 is maintained at a low level during one cycle CT, and the flip-flop circuit 56
remains cleared by the output signal S13 of the one-shot multivibrator 60b generated every cycle CT, so the high-level feedback command signal S6 remains output from the terminal of the flip-flop circuit 56. AND circuit 25a is left open. During the period of such one cycle CT, the pulse generation circuit 23
When the speed pulse S3 is output from the speed pulse S3, the reference pulse S4 passes through the AND circuits 25 and 25a for the pulse width period of the speed pulse S3 and is supplied to the addition type counting circuit 74, where it is added and counted. By the way, since the pulse width of the speed pulse S3 is proportional to the rotational speed of the electric motor 11, the number of pulses of the reference pulse S4 passing through the AND circuit 25 is also proportional to the rotational speed of the electric motor 11. 11 is equal to the ultra-low speed selected by the speed selection switch 26, the number of pulses of the reference pulse S4 passing through the AND circuit 25 by one speed pulse S3 is equal to the number of pulses in advance. This is the same as the speed setting pulse number Pan of (50) set in the setting circuit 42. Therefore, the count content Pcn until the counting circuit 74 is cleared by the falling edge of the speed pulse S3 is (50), and the first comparison circuit 27 compares this count content Pcn with the speed setting pulse number Pan. Ru. here,
The first comparator circuit 27 outputs a high level signal from the output section C if (Pcn<Pan), outputs a high level signal from the output section D if (Pcn>Pan), and outputs a high level signal from the output section D if (Pcn=Pan). ), the configuration is such that no output is produced, and in the present example, since (Pcn=Pan), the outputs of both output sections C and D of the first comparator circuit 27 are both at low level. As a result, none of the subtraction pulses S7, S9 and addition pulse S8 are input to the first counting circuit 29, and the set value of the first counting circuit 29 is a constant value (134) corresponding to the ultra-low speed.
Based on this, the thyristors 8 and 9 are fired at a phase angle of 145 degrees for each cycle CT, and the electric motor 11 is rotated at a very low speed of 100 rpm. If the rotational speed is increased or decreased due to load fluctuation or the like during rotation at such a very low speed, the following operation is performed. That is, when the rotational speed of the electric motor 11 changes in the increasing direction, in this case, the pulse width of the speed pulse S3 becomes narrower, so the number of reference pulses S4 passing through the AND circuit 25 decreases, for example, 40 pulses. Suppose that the value decreases to . Then, in this case, of course, the count content Pbn of the counting circuit 52a or 52b
Since also (40), the second comparison circuit 55 calculates (S
50>Pbn) and flip-flop circuit 5
Since the AND circuit 25a is kept open while the feedback command signal S6 is output from the AND circuit 72, the counting circuit 74 counts the 40 reference pulses S4 that have passed through the AND circuit 72. On the other hand, AND circuits 75, 7
6 is already in the open state by the return command signal S6. Then, the first comparison circuit 27 compares the count content Pcn of the counting circuit 74 and the speed setting pulse number Pan, but in this case, since (Pan>Pcn), a high level signal is output to the line 77. A high level signal is supplied to the one-shot multivibrator 78 of the second arithmetic pulse generating circuit 31 at its B terminal. Since the speed pulse S3 is supplied to the A terminal of the one-shot multivibrator 78 via the differentiating circuit 49, the one-shot multivibrator 78
8 is a predetermined number, for example, one (subtraction pulse to be described later), in response to the fall of the speed pulse S3 that occurs first after receiving the high level signal at the B terminal as described above.
The first counting circuit 29 outputs an addition pulse S8 (the same applies to S ₇ and S ₉ ), which is added and counted by the first counting circuit 29, and the setting content is increased from (134) to (135).
Therefore, in the next cycle CT, the thyristors 8 and 9 are fired at a phase angle corresponding to (135) above, their conduction angle is reduced by one cycle of the reference pulse S4, and the motor 11 is decelerated accordingly. . The above operation is repeated until the number of reference pulses S4 passing through the AND circuit 25 reaches 50, that is, until the feedback command signal S6 disappears, and the motor 11 is returned to the set ultra-low speed.
In contrast to the above, suppose that the rotational speed of the electric motor 11 is reduced to a very low speed or less, and the number of reference pulses S4 passing through the AND circuit 25 becomes 60, for example. In this case, as understood from the above description, the command signal generation circuit 28 is connected to the second comparison circuit 55.
(S50<Pbn)
5 is output, the same operation as at the time of startup described above is performed, and the subtraction pulse S7 from the AND circuit 72 of the first calculation pulse generation circuit 30 is supplied to the first counting circuit 29, so that the motor 11 is increased in speed until it reaches a very low speed. Incidentally, regarding speed reduction fluctuations at a set speed higher than the ultra-low speed of the electric motor 11, the second calculation pulse generation circuit 31 acts to output a subtraction pulse S9, which will be described in detail later.

The above explanation is about startup to ultra-low speed and constant speed maintenance operation at ultra-low speed when the speed selection switch 26 is set to the terminal 26a corresponding to ultra-low speed. The operation will be explained. That is, the speed selection switch 26 has terminals 26b and 2 corresponding to low speed, medium speed, and high speed, respectively.
When the speed setting pulse number Pan is set to either 6c or 26d, the speed setting pulse number Pan set in the pulse number setting circuit 42 is smaller than the numerical information S50 of (50) set in the numerical information circuit 58. First, the activation starts with numerical information S5 by the same operation as described above.
The speed is increased to a speed corresponding to 0. After this (S
50=Pbn), the command signal generation circuit 28
The feedback command signal S6 is outputted from the input signal S6, and therefore, the reference pulse S4 passes through the AND circuit 25a and is counted by the counting circuit 74, and the count contents are
Pcn and the speed setting pulse number Pan are compared by the first comparison circuit 27, and if the set speed has not been reached yet, since (Pcn>Pan), the line 80 is connected from the output part D of the first comparison circuit 27. A high level signal is outputted to the B terminal of the one-shot multivibrator 81 of the second arithmetic pulse generation circuit 31 via the AND circuit 76. As a result, the second calculation pulse generation circuit 31 generates one subtraction pulse S in response to the falling edge of the speed pulse S3.
9 and supplies it to the first counting circuit 29 via the OR circuit 73;
decrements the count by one, and therefore, as described above, in the next cycle CT, the conduction angle of the thyristors 8 and 9 is increased by one cycle with the reference pulse S4, and the motor 11 is accelerated. By repeating the above operations, the speed of the electric motor 11 is increased to the set speed. During operation with the electric motor 11 reaching the set speed, if the rotational speed is increased or decreased due to load fluctuations, first of all, if the speed increases or decreases, as described above,
A feedback command signal S6 is output from the command signal generation circuit 28, and the feedback command signal S6 is outputted from the command signal generation circuit 28, and the second calculation pulse generation circuit 3
1 outputs an addition pulse S8, and the electric motor 11 is controlled to decelerate. On the other hand, when the deceleration fluctuates, first, the motor 11 is at a speed considerably higher than the speed corresponding to the specific numerical information S50 set in the numerical information circuit 58, and the motor 11 is at a speed considerably higher than the speed corresponding to the specific numerical information S50 set in the numerical information circuit 58. , or the count contents of 52b
Before Pbn exceeds the specific numerical information S50 due to deceleration fluctuations of the electric motor 11, the reference pulse S4 passes through the AND circuit 25a due to the feedback command signal S6 output from the command signal generation circuit 28, and this pulse is transmitted to the counting circuit. 74, and the counting contents
Pcn and the speed setting pulse number Pan are compared by a first comparison circuit 27. Therefore, in this case, naturally (Pan<Pcn), a high level signal is output to the line 80, and based on this, the subtraction pulse S9 is output from the one shot multivibrator 81 of the second calculation pulse generation circuit 31. Since this is outputted and supplied to the first counting circuit 29 via the OR circuit 73, the speed of the electric motor 11 is increased in the same manner as described above. By repeating this operation, the speed of the electric motor 11 is increased until it returns to the set speed.

Therefore, according to the above device, the pulse number setting circuit 4
Set speed set to 2 (speed setting pulse number
When a deviation occurs between the actual speed output from the counting circuit 74 (the signal is the count content Pcn), the first counting circuit 29 sends a predetermined number of speeds per cycle, for example, one, regardless of the amount of deviation. Since the configuration is such that the addition pulse S ₈ or the subtraction pulses S ₇ and S ₉ are applied, the amount of change in the conduction angle of the thyristors 6 and 7 is constant regardless of the above deviation. As a result, no sudden acceleration or deceleration action is applied to the electric motor, and even when the speed is changed over a wide range, no wave phenomenon occurs in the motor speed, and a stable control action can be obtained.

By the way, since the counting circuits 52a and 52b sequentially add and count the reference pulse S4 from zero in response to the rotation signal S11 during the startup mentioned above, the state of (S50>Pbn) is formed, and during that time , the reference pulse S4 is connected to the AND circuit 25a.
may pass through and be counted by the counting circuit 74. However, the second calculation pulse generation circuit 31 generates the addition pulse S8 according to the comparison result of the first comparison circuit 27 unless it receives the fall of the speed pulse S3 generated during the period of one cycle CT of the synchronization pulse S2. and the subtraction pulse S9 is not generated, and even if the farthest pulse S3 falls, by the time the falling edge occurs, the counting circuit 52a has generated the reference pulse S4 corresponding to the actual speed of the motor 11. Adding and counting the numbers,
The second comparison circuit 55 determines that the count content Pbn of the counting circuit 52a is larger than the numerical information S50, and sends a start command signal S to the flip-flop circuit 56.
In order to output 5, there is no difference.

Next, to explain the case of stopping the electric motor 11, in this case, the start/stop switch 6
Press 1 only momentarily. Then, a pulse is generated from the one-shot multivibrator 62,
Since the flip-flop circuit 63 is inverted from set to reset, the line 63a goes high, the output of the NOR circuit 66 is always low regardless of the signal level on the line 65, and the flip-flop circuit 68 is forced into the reset state. is held, and the AND circuit 32 is closed. Therefore, the coincidence signal S1 is no longer output from the second counting circuit 33, the thyristors 8 and 9 are not fired, and the motor 11 is stopped.

Next, a second embodiment will be explained with reference to FIG. 8. In this embodiment, the speed selection switch 26, pulse number setting circuit 42, and start/stop switch 61 are omitted from FIG. , foot controller 82, pulse number setting circuit 8
3 and a NAND circuit 84 are provided, and this NAND circuit 8
This corresponds to connecting the output terminal of No. 4 to the A terminal of the one-shot multivibrator 62 shown in FIG. The foot controller 82 is equipped with a potentiometer whose output voltage changes in proportion to the amount of depression, and the voltage output from this potentiometer that is inversely proportional to the amount of depression is generated by an A-D converter provided in the pulse number setting circuit 83. The speed setting pulse number Pan is converted to the output line 85a corresponding to each bit.
85h to the input section B of the first comparison circuit 27. In a released state where the foot controller 82 is not depressed, all output lines 85a to 85h are at a high level, and as the amount of depression of the foot controller 82 increases, the number of speed setting pulses of the pulse number setting circuit 83 increases.
Pan is starting to decrease. On the other hand, a line 85a corresponding to the least significant bit is connected to one input terminal of the NAND circuit 84 via an inverter 86, and an output line 85a is connected to the other remaining input terminals.
b to 85h are connected. Now, when the foot controller 82 is released, all the output lines 85a to 85h are at a high level, so the output of the NAND circuit 84 is at a high level. When the foot controller 82 is pressed in this state, only the output line 85a corresponding to the least significant bit changes to low level during the pressing process, so the output of the NAND circuit 84 changes from high level to low level. . The one-shot multivibrator 62 is triggered by this level change, the flip-flop circuit 63 is reversed to the set state, and the electric motor 11 starts to be activated as described above. The rotational speed is maintained at a speed corresponding to the speed setting pulse number Pan set in the pulse number setting circuit 83. When the foot controller 82 is released, only the line 85a becomes low level during the release operation, and the remaining lines 85b to 85h
Since there is a moment when all of the signals become high level, at this point the output of the NAND circuit 84 changes from high level to low level, and this change causes the one-shot multivibrator 62 to generate a pulse and set the flip-flop circuit 63. The state is reversed to reset, and the motor 11 is stopped as in the first embodiment.

As is already clear from the above embodiments, the present invention is implemented by a so-called digital circuit that controls the motor from the time it starts until it reaches a set speed, and processes control pulse signals to maintain the set speed. Therefore, the operation is stable against fluctuations in temperature or power supply voltage, etc., and a stable rotation speed can be obtained.
Since control by a so-called microcomputer becomes possible, it is very effective when controlling the speed of an electric motor provided in equipment controlled by a computer.
Further, even when a wide speed change is performed, a stable control action can be obtained without suddenly accelerating or decelerating the electric motor.

[Brief explanation of the drawing]

Figures 1 to 7 relate to the first embodiment of the present invention. Figure 1 is a wiring diagram showing the motor drive circuit together with the DC power supply section, Figure 2 is a wiring diagram of the speed control circuit, and Figure 3 is the wiring diagram of the speed control circuit. A wiring diagram of the rotation signal generation circuit, FIGS. 4 to 6 are time charts for explaining the operation of the embodiment, FIG. 7 is an explanatory diagram for explaining the operation of the embodiment, and FIG. 8 is a diagram of the second embodiment. It is a wiring diagram showing an example. In the figure, 3 is an AC power supply, 8 and 9 are thyristors (semiconductor switch elements), 11 is an electric motor, 12 is an ignition circuit, 22 is a synchronous circuit, 23 is a pulse generation circuit,
24 is a reference pulse generation circuit, 25 is an AND circuit (first gate circuit), 26 is a speed selection switch (speed setting means), 27 is a first comparison circuit, 28 is a command signal generation circuit, and 29 is a first Counting circuit, 30
and 31 are first and second calculation pulse generation circuits;
32 is an AND circuit (second gate circuit), 33 is a second counting circuit, 36 is a rotation signal generator, 42 is a pulse number setting circuit, 52a and 52b are counting circuits, 82 is a foot controller (speed setting means) ),
83 is a pulse setting circuit.

Claims (1)

[Scope of Claims] 1. A semiconductor switch element for controlling power supplied from an AC power source to a motor, a synchronous circuit that generates a synchronous pulse in synchronization with generation of an AC voltage from the AC power source, and a synchronous circuit for generating a synchronous pulse in synchronization with generation of an AC voltage from the AC power source. a speed pulse generation circuit for generating a speed pulse with a pulse width proportional to the actual speed and temporally related to the generation of the synchronization pulse; and a reference pulse generator for generating a reference pulse at a predetermined high frequency. a first gating means for passing said reference pulse while said speed pulse is occurring; a speed setting means manually operated for setting the speed of said motor to a desired speed; comparison means for comparing the number of speed setting pulses corresponding to the set speed set according to the operation of the means and the number of reference pulses that have passed through the first gate means; A predetermined number of addition pulses are generated when the number of pulses is greater than the number of pulses, a predetermined number of subtraction pulses are generated when the number of speed setting pulses is less than the number of passed reference pulses, and a pulse is generated when the number of both pulses match. a calculation pulse generating means for stopping the motor; and a predetermined number of initial pulses stored in memory in connection with the start of operation of the motor, and counting from the initial number of pulses upon receiving the predetermined number of addition pulses or the predetermined number of subtraction pulses. a first counting means whose content increases or decreases, and is opened in response to said synchronization pulse;
a second gate means for passing a reference pulse from the reference pulse generating circuit; and a second gate means for counting the reference pulses that have passed through the second gate means, and the number of the reference pulses being the count content of the first counting means. a second counting means for generating a coincidence signal when there is a coincidence; and a firing circuit for supplying a firing pulse to the semiconductor switch element in response to the coincidence signal, the circuit comprising a second counting means for generating a coincidence signal when a coincidence occurs; A speed control device for an electric motor, characterized in that the conduction angle of the element is increased or decreased by an amount corresponding to the predetermined number of the addition pulses or subtraction pulses. 2 The second counting means stores the count content of the first counting means as an initial value in response to the synchronization pulse from the synchronization circuit, and subtracts the reference pulse that has passed through the second gate means. 2. The speed control device for an electric motor according to claim 1, wherein the coincidence signal is generated when the counted value becomes zero. 3. Said second gate means is closed in response to a coincidence signal from said second counting means and provides a reference pulse to said second counting means until the next synchronizing pulse is generated from said synchronizing circuit. 3. The speed control device for an electric motor according to claim 2, wherein the speed control device for an electric motor is configured to block input of the speed of the motor.