JPS582558B2 - Electronic damper for pulse motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulsed smoke damper, and more particularly to an electronic damper for a pulsed motor that is ideal for devices that require high-speed operation of the pulsed motor.

Generally, a pulse motor is provided with a damper.

This damper is provided to quickly move the pulse motor to a stable position and keep it stationary.

Specifically, as shown in FIG. 1, when the pulse motor is rotated by θ0 from a certain position and then brought to a standstill, the pulse motor reaches θ0 after a time t1, but then oscillates to converge to θ0 for a time t2.

This vibration has an undesirable effect on the device.

For example, a typewriter using a pulse motor cannot print until vibrations are reduced.

In other words, if you print while the machine is vibrating, the characters will not be printed clearly.

Furthermore, in a disk device or the like, it has an adverse effect on the positioning of the head.

Therefore, various methods have been conventionally used as dampers.

One of them is to drive the pulse motor using a two-phase simultaneous excitation method.

The other method is to constantly interpose a capacitor between the windings of a one-phase excitation type pulse motor, and utilize the charging and discharging current when the motor is turned on and off.

However, although the former method produces a damper effect, it is more difficult to accurately control the angle than with the one-phase excitation method.

Furthermore, the latter method can only be applied to low-speed devices.

That is, excitation by discharge current cannot follow high-speed interruptions.

The effect is especially great when the capacitance of the capacitor is increased.

Therefore, for devices such as typewriters, which require precise angles to select the print head, and which require the next type to be selected at high speed and immediately come to rest,
Using pulse motors has been difficult.

The present invention has been made in view of these circumstances.

It is therefore an object of the present invention to provide a damper which allows the rotor of a pulse motor to be immediately transferred from one position to another and to be immediately stationary.

Another object of the present invention is to perform high-speed transition and immediate stop;
At the same time, it is an object of the present invention to provide a damper that does not reduce the angle n degrees of a pulse motor.

For this reason, the present invention uses a one-phase excitation type pulse motor and provides a damper effect when the pulse motor stops.

The present invention will be described below with reference to the drawings.

For convenience of explanation, a typewriter will be described as an example, but the same purpose can be achieved by using other devices as well.

In FIG. 2, 1 indicates a control circuit.

This control circuit 1 has a function of outputting a driving timing pulse of a printing hammer (not shown) from a terminal C, and a function of outputting a driving timing pulse of a printing hammer (not shown) from a terminal C, and a winding L1.
It has a function of determining in what sequence to apply current to L4 to excite it, and a function of generating a pulse from terminal B to drive relay 4, which is a switching element.

L1 to L4 indicate the windings of the pulse motor.

It is assumed that the pulse motor in this example is a four-phase machine.

Therefore, since it is a 1-phase excitation system for a 4-phase machine, the winding L
1 to L4 are excited one by one.

Further, the windings L1 and L2, L3 and L4 are configured to generate electromotive forces of opposite polarities due to vibration or rotation of the rotor of the pulse motor.

Specifically, windings L1 and L2 (or L3 and L4) are wound on the same pole in opposite directions.

TR1 to TR4 are transistors that respectively turn on and off current to the windings L1 to L4.

2 indicates a current source, and 3 indicates a hammer drive section.

Therefore, when the control circuit 1 rotates the pulse motor to the right several times, the control circuit 1 turns on/off the transistors TR1 to TR4 according to a certain sequence.
F is controlled to excite the windings L1 to L4.

The same is true when turning several times to the left.

C1 and C2 are capacitors, SW1 and SW2 are switch points, and 4 is a relay, and the switch points SW1 and SW2 and the relay 4 constitute a switching element.

The capacitors C1 and C2 and the switching element are connected to the winding L.
1-L2 and interposed in series with L3-L4,
Switch points SW1 and SW2 are initially open.

Since it is configured in this way, it works as follows.

For explanation of this operation, refer to the timing chart of FIG. 3.

For example, in order to print, the control circuit 1 outputs the necessary number of pulse motor drive pulses A.

Also, in the control circuit 1, based on this, an ON/OFF sequence for the transistors TR1 to TR4 is created and executed.

Therefore, when the pulse motor drive pulse A is finished outputting, the pulse motor rotates in a certain direction at a certain angle.

At that time, in synchronization with the fall of the final pulse of the pulse motor drive pulse A, the relay drive signal B is transmitted to the control circuit 1.
is output from to relay 4.

This causes relay 4 to overturn switch points SW1 and SW2.

Therefore, a closed loop of winding L1-capacitor C1-winding L2 and a closed loop of winding L3-capacitor C2-winding L4 are formed.

As a result, the electromotive force generated in the winding L1 has the same magnitude and opposite polarity as the electromotive force generated in the winding L2, so they cancel each other out via the capacitor C1.

Similarly, the electromotive forces generated in the windings L3 and L4 cancel each other out.

Thereafter, the control circuit 1 sends a hammer drive pulse C to the hammer drive unit 3 to perform printing.

During this printing, the electromotive forces are canceled out between the windings L1-L2 and L3-L4, so no vibration or rotation of the rotor occurs.

For this reason, the printing is completed neatly.

As explained above, according to the present invention, since no capacitor is interposed during rotation of the pulse motor, high-speed operation can be performed.

In addition, when the pulse motor stops, a capacitor is inserted,
Since the generated electromotive force is canceled out, a highly efficient damper can be provided, and the vibration and rotation of the rotor can be stopped immediately.

Furthermore, since it is a one-phase excitation method, there is no reduction in the angular accuracy of a pulse motor, making it suitable for typewriters.

The method for determining the optimum capacitor value will be described below.

When the rotor vibrates, the frequency and phase of the electromotive force excited in the stator coil do not necessarily match the frequency and phase of the rotor's vibration.

The reason for this is that the magnitude of the magnetic flux passing through the stator coil is a non-linear function of the locus position.

Moreover, this function differs depending on the structural type of the pulse motor.

This can be expressed mathematically, where B is the magnetic flux and the phase of the rotor is θ. Here, θ is the amplitude of the rotor vibration, ω is the angular frequency, and the phase φ is as follows. It can be expressed as

θ=■Sin(ωt+φ) And since the excited electromotive force is proportional to the change in magnetic flux,
Expressed mathematically, in order to obtain a damping effect, the current i flowing due to this electromotive force e must have a phase relationship that acts as a brake with respect to the angular velocity of the rotor.

That is, here Z is the impedance of the closed loop circuit formed by the capacitor and the two coils.

Therefore, the value of C forming Z must be appropriately selected based on F(θ).

In other words, in the above equation, ω so that ω2LC-1=0
When the relationship between and LC is determined, Z=R and Z becomes the minimum.

This means that it is sufficient to match the electrical series resonance frequency determined by the LC to the mechanical vibration frequency ω of the rotor.

What we must pay attention to here is the inductance L of the coil.

As is well known as a characteristic of pulse motors, the inductance of the winding coils is not constant depending on the position of the rotor and other factors.

Moreover, considering the inductance of the coil at the rotor's mechanical resonance frequency, the apparent inductance of the coil is larger than the inductance of the coil itself because the mechanical vibration of the rotor causes magnetic flux changes and, as a result, an induced voltage is generated in the coil. That's what happened.

The degree of increase varies depending on the type and shape of the pulse motor.

Incidentally, in a pulse motor for driving a type plate, which is an embodiment of the present invention, the inductance acts as approximately twice the nominal inductance of the coil.

A procedure for determining an appropriate capacitor value for this embodiment will be explained.

The nominal inductance of the coil per winding is L',
Let fM be the mechanical vibration frequency of the rotor.

When calculating the electrical resonance frequency, the inductance of the coil is doubled as mentioned above, and since the two coils are connected in series, L = 4L', so the electrical resonance frequency f
The formula for finding M is as follows.

Here, as described above, setting fE=fM represents the maximum damping effect, so it is sufficient.

From this, calculating C is as follows.

Here, if we substitute the specific numerical values according to the example, we get fM=67H2 L'=14mH ∴C≒100μF.

Expressing this in another way, if f0 is the resonance frequency calculated from the nominal inductance value L' of the coil and the capacitor, then the following equation holds true.

It will be destroyed.

In other words, it can be said that the electrical series resonance frequency f0 calculated from the nominal inductance of the coil should be selected to be low.

Figure 4 shows the results of measuring the time it takes for the pulse motor to stop vibrating by changing the capacitance of the capacitor.

As you can see from the figure, the capacitance of the capacitor is 50 μF ~ 2
When the value is 00 μF, that is, the series resonant frequency of the series resonant circuit formed by the two windings and the nominal inductance capacitor is within a range that can be practically used in mechanical systems.

That is, the capacitance of the capacitor is centered around 100 μF, and ranges from 1/2 (50 μF) to twice that (200 μF).

However, it is clear that the width may be increased depending on the intended use of the device.

By the way, as mentioned above, if the absolute value of the impedance Z of the closed loop formed by the capacitor and the two coils is small, the damping effect will theoretically be large.

Therefore, as a method for reducing the impedance Z, an attempt is made to reduce the DC resistance component present in the closed loop circuit.

This aims to further enhance the effect of immediate stop in the present invention.

FIG. 5 shows an embodiment of the present invention, and the same reference numerals as in FIG. 2 indicate the same components.

Therefore, in this example, negative resistances RN1 and RN2
is interposed between switching elements SW1, SW2 and coils L1L2.

Specifically, FIG. 6 shows an example of a circuit that provides the negative resistances RN1 and RN2.

In the figure, 61A and 61B are power supplies, r1, r2, r3
is a resistor, 62 is an operational amplifier, and 63 and 64 are transistors.

This circuit is a so-called non-inverting circuit, and the transistor 63
, 64 are connected to increase the output current.

Therefore, in the circuit, This amount of negative resistance is generated.

By interposing the negative resistance RN explained above,
The current flowing in the closed loop increases, thereby increasing the damping effect.

In the pulse motor used by the present inventor, the DC resistance of one winding is 5Ω, and the entire closed loop is 10Ω.

Therefore, the negative resistance RN may be set to 9Ω.

It has been experimentally confirmed that this results in a shape in which the original graph is translated downward in parallel, as shown by the broken line in FIG.

And when using a 100μF capacitor, 15mS
The vibration stopped.

Here, the reason why the negative resistance is not made the same as the DC resistance value in the closed loop is that although the rotor does not vibrate, the time to converge to the rotation angle of the rotor may be longer due to overdamping.

Furthermore, it is clear that oscillation occurs when the absolute value of the negative resistance is made greater than the DC resistance value.

As described above, according to the present invention, the pulse width of the relay drive signal B shown in FIG.
By applying approximately 15 mS when a negative resistance is interposed, the vibration time can be reduced to 1/20 or 1/60 of the conventional vibration time of approximately 1 sec.

In the description of the present invention, a four-phase pulse motor is used in a one-phase excitation system, but the present invention is not limited to this.

That is, it is good to use a pulse motor of an n-phase machine with a one-phase excitation method.

Further, the switching element may be a transistor or an SCR, and may be controlled by a control circuit with or without a capacitor.

As described above, in the present invention, when a pulse motor is applied to a device that requires high-speed movement and high-speed stopping, a damper effect is produced by the capacitor and the switching element, and if a negative resistance is used, the effect becomes even greater.

Therefore, according to the present invention, an optimal pulse motor damper can be provided.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the state of vibration of a pulse motor, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is a timing chart for explaining the operation of the circuit in FIG. 2. FIG. 4 is a diagram showing the effects of the present invention, FIG. 5 is a block diagram of a further improved version of the present invention, and FIG. 6 is a circuit diagram of an example of a circuit for creating a negative resistance. L1 to L4... Winding, C1, C2...
・・・・・・Capacitor, SW1, SW2・・・・・・
...Switch point, 4...Relay, SW
1, SW2, 4... Switching element,
RN1, RN2・・・・・・Negative resistance.

Claims (1)

[Claims] 1. In a one-phase excitation type pulse motor having two windings that generate electromotive force of opposite polarity due to vibration or rotation of a rotor, a capacitor and a switching element are provided between the two windings. An electronic damper for a pulse motor, in which the switching element is brought into conduction after the output of the pulse motor driving pulse is completed. 2. The series resonant frequency of the series resonant circuit formed by the capacitor and the total inductance obtained by adding the capacitance of the capacitor to the inductance of the two windings and the inductance equivalently converted from the mechanical system, including the mechanical system. Centered around 1 times the vibration frequency of the pulse motor, 1/1
An electronic damper for a pulse motor according to claim 1, characterized in that the damper is set in a range of 2 times to 2 times. 3. In a one-phase excitation type pulse motor having two windings that generate electromotive force of opposite polarity due to rotor vibration or rotation, a capacitor, a switching element, and a capacitor and a switching element are connected between the two windings. A negative resistance is interposed in series to cancel out the DC resistance component,
An electronic damper for a pulse motor that brings the switching element into a conductive state after outputting a pulse motor drive pulse.