JPS5883593A - Speed controller for dc motor - Google Patents

Abstract

PURPOSE:To obtain a tape tension of substantially constant from the start to the end of a winding tape by switching the high resistance side of a bridge at recording, reproducing and quick forwarding times. CONSTITUTION:A changeover switch 25 is closed at the recording and reproducing times, thereby conducting a transistor 22 and interrupting a transistor 23, and a bridge circuit is composed of a DC motor 11, and resistors 12, 13, 14. The switch 25 is opened at the quick forwarding time, thereby interrupting the transistor 22 and conducting the transistor 23, and the bridge circuit is composed of the motor 11 and resistors 12, 13', 14'. In this manner, the tape can be obtained at substantially constant tension from the start to the end of the winding tape.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a direct current control device that is effective for use in a control device for a tape winding reel motor in a tape drive device such as a tape recorder (including cases that have only one of the recording and playback chairs). This invention relates to a motor speed control device.

Conventionally, two-motor type tapes have a capstan shaft that drives the tape at a constant speed with a pinch roller, and a dedicated motor for driving the reel stand that winds the tape sent out by the capstan shaft. In a drive device, for example, during recording or playback, the capstan shaft is required to rotate at a constant speed, whereas in a winding machine, the rotation speed changes depending on the amount of tape wound. , ideally to keep the tape winding tension constant3.
-5. To achieve this, a torque proportional to the tape winding radius is required.

As a means for keeping the tape winding tension constant, for example, there is a method in which the reel stand is provided with a frequency generator that generates a frequency proportional to the rotation of the reel stand. In other words, by detecting the rotational speed of the reel stand using the frequency generator and giving a torque command proportional to the rotation period of the reel stand to the reel drive motor, constant tape tension can be obtained from the beginning of tape winding to the end of winding. It was designed so that Although the above method provides extremely accurate constant tape tension depending on the tape winding diameter, it requires a frequency generator to be installed on the reel stand (or reel motor).
The structure becomes complicated. Furthermore, since the torque command is output in accordance with the period of the signal obtained by the frequency generator, there is a drawback that the control circuit becomes complicated.

The present invention does not require a rotation speed detection device such as a frequency generator, and has a relatively simple circuit configuration.
The present invention provides a direct current motor speed control device that is effective for use in a direct current reel motor control device that can provide a substantially constant tape tension from the beginning of tape winding to the end of tape winding.

The present invention will be explained in detail below.

FIG. 1 is a block diagram of the main parts of a tape drive device such as a tape recorder. In Fig. 1, 1 is the capstan shaft;
A pinch roller 2 pinches the tape 3 between the capstan shaft 1 and the pinch roller 2 and runs it at a constant speed. 4
is a reel stand on the tape winding side, which is rotated by a reel motor 6;

6 is a recording/reproducing head.

Now, the tape running speed is ut [(m/7]), the tape radius of the reel stand on the tape winding side is R [cra], the reel stand torque is TR [yw-α], and the reel stand rotation speed is NnCrpi.
) If the % tape tension is t and [yvr], then R 2πR-1d=vt・・・・・・・・・・・・(1)
Ret==TR・・・・・・・・・・・・・・・・・・
...(2) Formula 02 holds true.

If R is eliminated from the above equation (13, (2)), the following equation holds true.

Tn @Nn = -77t 11t - (s12π In equation (3), tape running speed vt and tape tension t are constant, so from equation (3), reel stand torque TR and reel stand rotation speed NR are inversely proportional. In Fig. 2, a is the reel stand torque T, and the reel stand rotation speed N.
This is a conflict that illustrates the relationship between R.

In other words, depending on the number of rotations of the reel stand on the tape winding side, (3)
If the reel motor is controlled to satisfy the equation, the tape can be wound onto the take-up reel stand with constant tape tension from the beginning of tape winding to the end of tape winding. However, in order to perform the above-described control, it is first necessary to provide a rotation speed detection device such as a frequency generator to detect the rotation speed of the reel stand (or reel motor). Furthermore, there are eight control circuits for causing the reel drive motor to generate torque to obtain a constant tape tension in accordance with the signal detected by the rotation speed detection device. The control circuit for the reel motor needs to generate a torque that satisfies the equation (3) above in accordance with the detection signal obtained by the rotation speed detection device, so it is a complicated circuit. t) It was not practical.

The present invention uses a bridge circuit as a motor rotation speed detecting means to extract the generated voltage of the motor proportional to the rotation speed, and furthermore, the rotation speed during constant tape tension control shown by a in FIG. By approximating the torque curve with a straight line as shown by b in Figure 2, the speed of a DC motor is such that an approximately constant tape tension can be obtained from the beginning of tape winding to the end of tape winding with a simple circuit configuration. A control device is provided. 3 is a circuit diagram showing the principle of the present invention.

In FIG. 3, a DC flow motor 11 having an internal resistance Ra and a first resistor 12 having a DC resistance value R+ are shown.
are connected in series to constitute a low resistance side, and a second resistor 13 having a DC resistance value R2 and a third resistor 14 having a DC resistance value R5 are connected in series to constitute a high resistance side. ,
Said first resistor 72. .

12 and the second resistor 13 are connected in parallel with the low resistance sides so as to be opposite sides to form a bridge circuit. The voltage between the detection terminals a and b of the Kamiko bridge circuit is input to the comparison amplifier 15, and the output of the comparison amplifier 16 is used to energize the power supply control transistor 17 connected in series in the power supply path of the bridge circuit. Configured to control the amount. Reference numeral 16 denotes a reference voltage source that provides a reference for the rotational speed of the DC reel motor 110, and the magnitude of the voltage is Xs. Note that 18 is a DC voltage source whose DC voltage is EO.

Generally, the equal circuit of a DC motor is represented by a series circuit of a back electromotive force IC & and an internal resistance RIL, and the back electromotive force ICa
changes in proportion to the rotational speed H. In other words, the following equation (4)
It is expressed as n.

Ha = Ka −N −−−−−1, −−−−, −,
,00,(4) However, Xa is the power generation constant of the DC motor.

In FIG. 3, the armature current flowing through the DC motor 11 is Xt, the current flowing through the second resistor 3 and the third resistor 14 is Il), and the current current n is between the detection terminals a and b of the bridge circuit. To find the voltage, Vab = engineering a R+ −
IbR3------f6) Also Ia (Ra+R+) 10Ea=Ib (R2+R3)+
IC5=(11(6)t I6) By eliminating the equation, we get...
The control circuit of the DC motor in the figure is the detection terminal a of the bridge circuit.
Since the potential difference Tab between , and b is controlled to be zero, Vab=O......S... (8
) holds true.

Furthermore, the torque generated by the motor can be expressed by the following equation.

T=[i・xa・n1・・concave・・(9) Tatami,
Kt is the torque constant of the motor (61t (8
) t From formula (9), the number of revolutions N is determined as follows: N=l□−μ t...

Therefore, in equation (10), by appropriately determining the values of No and μ, the rotation speed -
Torque control characteristics can be obtained.

In addition, since the values of No and μ can be expressed by equations (11) and (12), the three constants Ka and Kt of the DC reel motor
.

Once Ra is determined, the 1st, 2nd, .
The values of the third resistors R1, R2, R3 and the reference voltage source EsQ can be calculated.

As mentioned above, 1. Second. Third resistor R1, R2゜R
3 and the reference voltage Is, it is possible to obtain approximately constant tape tension from the beginning of winding of the tape to the end of winding of the tape during steady running of recording and reproduction in the tape drive device.

The above is an explanation of the basic operating principle of the present invention.

In general, in recording/playback devices, the reel motor 1° is often used not only for the recording/playback device but also for fast-forwarding the tape. It is normal that they are different.

As mentioned above, a control system that satisfies the above equation (3) can always provide a constant tape tension during recording and reproduction. Even during fast forwarding, the tape tension remains constant from the beginning of winding to the end of winding (not necessarily the same as when recording/reproducing 74E)
However, only the rotation speed of the reel stand increases (normally, recording/
It is desirable that the playback speed be several 1° times faster than the playback speed.

C in Figure 2 shows the rotational speed-torque curve when the tape tension /l in equation (3) is set to be the same as that during recording and playback for convenience, and the tape speed let is six times that during recording and playback. be. Further, d in FIG. 2 is a linear approximation of the rotation speed-torque curve.

As is clear from b and d in FIG. 2, recording/reproduction 11.
The required motor rotation speed-torque control characteristics are completely different between 2 o'clock and rapid traverse. Therefore, when one motor is used to drive the reel not only during recording and reproduction but also during fast forwarding, it is necessary to switch the control characteristics of the motor according to each mode.

The present invention provides a speed control device for a DC motor, such as a reel motor, which can easily realize completely different control characteristics depending on each mode during recording/playback and fast forwarding using a simple switching circuit. be.

FIG. 4 is a circuit diagram of a speed control device for a DC motor according to a specific embodiment of the present invention. In this figure, elements that perform the same functions as those shown in FIG. 3 are given the same reference numerals.

In FIG. 4, the circuit within the dotted line is the comparison detection circuit 16.
shows. '21, 22.23 are the 1st and 2nd, respectively. The emitters of the third transistor are connected to form a differential amplifier. 26 is a changeover switch for changing the control characteristics of the rotation speed and torque of the direct reel motor according to each mode during recording/playback and fast forwarding, and is closed during recording/playback and open during fast forwarding. be done. Zener diodes 24 and 24' are used to provide a rotational speed reference for the DC motor 11 during recording/reproducing and fast forwarding, and the Zener voltages are respectively expressed as Eg' and Eg'.

13 and 14 are the second components of the DC motor control device during recording and reproduction. A third resistor, which connects the Zener diode 24 and the second . A third resistor 13.14 is connected in series. Second. The base of the second transistor 22 is connected to the detection terminal which is the connection point of the third resistor 13, 14. Similarly, the second motors 13' and 14' are components of the DC motor control device during rapid traverse. A third resistor is connected in series with the Zener diode 24'.

Second. The base of a third transistor 23 is connected to the connection point b' between the third resistors 13' and 14'. Note that the base of the first transistor 21 is connected to the detection terminal a, which is the connection point between the DC reel motor 11 and the first resistor 1a, -].

Next, the operation of the DC motor speed control device shown in FIG. 4 will be explained.

During recording and reproduction, the changeover switch 26 is closed. Comparing the rotation speed-torque control characteristics of the DC reel motor required for both recording and playback modes and fast-forward mode, in equation (1o), the values of No and μ are both higher in the fast-forward mode. is large. Therefore, (11).

From equation (12), IC5(Xs’ holds true.

If the positions t between points b and b' when the changeover switch 26 is closed are nVb, vb/, then vb and vb' can be expressed as 4. When the changeover switch 26 is closed, Wb
>Wb' holds true, the base potential of the second transistor 220 is higher than the base potential of the third transistor 23, so the emitter-e pace of the third transistor 23 is reverse biased and in a cutoff state. It has become.

As a result, 1. Second. Third transistor 21°22
．． Of the transistors 23, only the first and second transistors 21 and 22 are in operation, forming a differential amplifier during recording and reproduction, and connecting the DC motor 11, the first resistor 12, and the transistors 21 and 22 during recording and reproduction. Together with the bridge circuit consisting of the third and fourth resistors 13 and 14 in FIG.

Next, during fast forwarding, the selector switch 25 is open, so the emitter of the second transistor 22
Reverse biased between bases, the second transistor 22 is now cut off.

16 During hard feeding, the first transistor 21 and the third transistor 23 constitute a differential amplifier, and the DC reel motor 11. The first resistor 12° and the third resistor during fast forwarding. Fourth resistor 13'.

Together with the bridge circuit consisting of 14', the control fi II characteristic of the DC motor (d in FIG. 2) required for fast forwarding can be obtained.

In the above explanation, the base voltages vb and vb' of the second transistor 22 and the third transistor 23 when the changeover switch 26 is closed have a relationship of vb>vb', but in the case of Wb <Wb' is the selector switch 2
6 may be provided on the bridge side where ' is connected to the third resistor 13' and the reference voltage during fast forwarding. In this case, when the selector switch 25 is closed, the mode is set to fast-forward mode, and when it is opened, the mode is set to record/playback mode.

As is clear from the above description, the DC motor speed control device of the present invention not only provides a substantially constant tape tension from the beginning to the end of tape winding during recording and playback with a simple circuit configuration. , the desired rotation speed-torque control characteristics can be easily and smoothly switched for each mode during recording/reproduction and fast forwarding.

Although the above explanation deals with the case of a reel motor used in a recording/reproducing device, it can also be used in other applications where it is necessary to switch the rotation speed/torque control characteristics of a DC motor, and the effect will be great. is obtained.

Furthermore, in the above explanation, only two types of control characteristics of the rotation speed-torque of the DC motor could be selected, but in FIG. Second. In addition to the third transistor, it is also possible to switch between two or more types of rotation speed-torque control characteristics by adding a transistor whose emitters are connected in common and a switch means, and in this case, the present invention also applies. Needless to say, it is included in the invention.

[Brief explanation of drawings]

, Figure 1 is a configuration diagram of the main parts of the recording/reproducing device, and Figure 2 is a diagram of the main parts of the recording/reproducing device.
．． - Reel rotation speed-torque control characteristics for obtaining constant tape tension from the start to the end of tape winding in a recording/reproducing device; Figure 3 shows the principle of the DC motor speed control device of the present invention; Circuit Connection Diagram FIG. 4 is a circuit connection diagram showing a specific embodiment of the speed control device for a DC motor according to the present invention. 11...DC motor, 12...First resistor, 13, 13'...Second resistor, 1
4, 14'...Third resistor, 16...
... Comparison amplifier, 17 ... Power supply control transistor, 18 ... DC power supply, 16, 24°24'.
...Reference circuit voltage source, 21...First transistor, 22...Second transistor, 23.
...Third transistor, 26... Changeover switch. Name of agent: Patent attorney Toshio Nakao and one other person - Must Figure 1 Figure 2 - Tp Figure 3 t

Claims (1)

[Claims] The controlled DC motor and the first resistor are connected in series to constitute a low resistance side, the second resistor and the third resistor are connected in series to constitute a high resistance side, and the first resistor is connected in series to constitute a high resistance side. configuring a bridge circuit by connecting the low resistance side and the high resistance side in parallel so that the resistor and the second resistor are opposite sides of each other,
The voltage between the detection terminals of the bridge circuit is input to an error detection means, and the output of the error detection means controls the amount of current supplied to a power supply control means connected to a power supply path of the bridge circuit, and 1st. Second. The error detection means is constituted by a differential amplifier formed by connecting the emitters of the third transistor, and a switch means for switching the operating state of the differential amplifier, 1. Second. By opening and closing the switch means by selecting either one of the differential amplifier section consisting of the first and second transistors and the differential amplifier section consisting of the first and third transistors among the third transistors, 1. A speed control device for a DC motor, characterized in that the control characteristic of the rotation speed-torque of the controlled DC motor is switched.