JPH05231516A - Rotation transmitting drive gear - Google Patents

Abstract

PURPOSE:To provide a rotation transmitting drive gear which is used in a magnetic drive mechanism so that the number of circumferential pulses of an encoder can be set within a range in which picture quality is almost the same as when an encoder of high density is used and that the cost of the encoder can be set to be as low as possible as long as its control performance is not affected. CONSTITUTION:A friction member 3 is interposed between a drive shaft 2 and a driven shaft 4 so that driving forces derived from the drive shaft 2 are transmitted to the driven shaft 4 by means of the frictional force of the friction member 3, and an encoder 6 is connected to the driven shaft 4 and the difference between the output frequency and the reference frequency of the encoder 6 is detected so as to variably control the speed at which the driven shaft 4 rotates. A circumferential pulse number setting means is provided which sets the number of circumferential pulses of the encoder 6 to be equal to or less than the number of circumferential dots of the driven shaft 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation transmission drive device applicable to, for example, a printer, a copying machine, a facsimile and the like.

[0002]

2. Description of the Related Art Conventional rotation transmission drive devices include a drive method using a gear and a drive method using magnetic force. Now, taking the latter as an example, JP-A-61-1
There is one disclosed in Japanese Patent No. 53048 as a "magnetic rotation transmission device". This is because a cylindrical magnet is interposed between the drive shaft and the driven shaft made of a magnetic material, and the attraction force of this magnet causes a frictional force between the outer peripheral surface of the drive shaft and the driven shaft and the cylindrical surface of the magnet. By this, the rotational force on the drive shaft side can be transmitted to the driven shaft side.
Further, in this case, the vibration is absorbed by applying a rubber coating to the cylindrical surface of the magnet.

In such a rotation transmission drive mechanism,
Rotation is transmitted by frictional force, causing slippage, which causes gentle and large uneven rotation with respect to rotation of the driven pulley. In other words, such a slip causes the rotational speed of the driven shaft to be substantially proportional to the change in the load torque even if the load torque applied to the driven shaft slightly changes for one rotation of the driven shaft. And change. Especially when the drum shaft of a copier or printer is attached to the driven shaft,
Even if the dot "single pitch error" or "adjacent pitch error" is small, the rotation speed of the driven shaft is large over the entire rotation angle where the load torque is small in one rotation of the driven shaft. Further, there is a problem that the "cumulative pitch error" is gentle on the slope or the peak to peak is large because the rotation speed becomes small in the portion where the load torque is large. Further, the eccentricity of the driven shaft also causes a cumulative pitch error.

[0004]

Conventionally, a method of mounting an encoder on a driven shaft and controlling the output frequency of the encoder has been used as a measure against a gentle and large accumulated pitch error. However, it was considered that the higher the frequency of the output pulse of the encoder, the higher the accuracy of control of the accumulated pitch error. Therefore, an encoder having a large number of round pulses and high cost was used. The reason for increasing the number of output pulses of the encoder in this way is that when the frequency corresponding to the number of teeth of the gear is controlled as in a gear drive mechanism, the finer the number of output pulses of the encoder, the more This is because it was known that the accuracy increased. However, in the case of a magnetic drive mechanism,
Since the purpose is to control a gradual and large accumulated pitch error, it seems possible to control using a coarser encoder than in the case of a gear drive mechanism. There is no way to control a large cumulative pitch error in. Moreover,
Even from the viewpoint of recording an image by attaching a drum shaft to the driven shaft, it seems that there is a certain relationship between the number of peripheral dots on the drum and the number of peripheral pulses on the encoder. There is no control that takes such points into consideration.

[0005]

According to a first aspect of the present invention, a friction member is interposed between the drive shaft and the driven shaft so that the driving force obtained by the drive shaft is generated by the friction force of the friction member. In the rotation transmission drive device for transmitting to the driven shaft, connecting an encoder to the driven shaft, detecting a difference between an output frequency of the encoder and a reference frequency, and changing and controlling the rotation speed of the driven shaft, the encoder. There is provided a peripheral pulse number setting means for setting the number of peripheral pulses to be equal to or less than the number of peripheral dots on the driven shaft.

According to a second aspect of the invention, in the first aspect of the invention, the control sampling frequency is set to be the same as the frequency of the output pulse of the encoder.

[0007]

According to the first aspect of the present invention, it is possible to reduce the number of circumferential pulses of the encoder while maintaining the control accuracy of the gradual and large cumulative pitch error almost in the same state.

According to the second aspect of the invention, since the sampling frequency can be reduced, the operating rate of the CPU can be reduced.

[0009]

An embodiment of the present invention will be described with reference to the drawings. FIG. 4 shows the entire structure of the rotation transmission drive device. A motor shaft 2 as a drive shaft is attached to the stepping motor 1, and the motor shaft 2 is connected to a driven pulley 4 as a driven shaft via a magnetic idler 3 as a friction member. A drum shaft 5 is attached to the center axis of the driven pulley 4, and an encoder 6 is attached to the opposite side thereof. A control circuit 7 is connected to the encoder 6, and the control circuit 7 is connected to a stepping motor driver 8. The stepping motor driver 8 can control the rotation speed of the stepping motor 1.

In such a rotation transmission drive device, in the present embodiment, as a first condition, a peripheral pulse number setting means (not shown) for setting the number of peripheral pulses of the encoder 6 to be equal to or less than the number of peripheral dots of the driven pulley 4. Is provided.
As a second condition, the control sampling frequency is set to be the same as the frequency of the output pulse of the encoder 6.

Before entering into the reason why these two conditions are set, the overall configuration of the apparatus and the outline of its control mechanism will be described with reference to FIGS. 4 to 7. In FIG. 4, the rotation of the stepping motor 1 is transmitted to the magnetic idler 3 by the motor shaft 2, and the rotational force of the magnetic idler 3 is driven by the driven pulley 4.
Be transmitted to. A drum shaft 5 is coaxial with the driven pulley 4 so that recording can be performed. Also,
The rotation of the driven pulley 4 is detected by the encoder 6, the output pulse obtained by this is input to the control circuit 7, and the driving frequency changed from this control circuit 7 is sent to the stepping motor driver 8 to drive the stepping motor 1 It can be driven to rotate.

Next, the control method of the control circuit 7 will be described with reference to FIGS. FIG. 5 is a graph showing the control method of the control circuit 7.

In FIG. 5, the horizontal axis is

[0014]

[Equation 1]

And the vertical axis represents

[0016]

[Equation 2]

[0017] is shown.

In this case, the drive frequency of the stepping motor 1 is changed and controlled within a range of ± 1% from the reference value of the rotational speed of the driven pulley 4, and the difference from the reference value is ± 1%.
If it exceeds, the drive frequency is controlled so as to be set to ± 1% so that the dot interval at the time of recording by the drum shaft 5 does not become extremely large or small in a part.

FIG. 6 shows a flow chart for performing control in the control circuit 7 shown in FIG. First, it is judged whether the input pulse is valid or not based on the set sampling frequency, and if it is valid, the driven pulley is calculated by calculating the number of pulses input to the control circuit 7 within the sampling frequency. The rotation speed of 4 is calculated, and the difference from the reference rotation speed is calculated. If the difference is within ± 1%, the drive frequency of the stepping motor 1 is changed by the difference. If the difference between the rotation speed of the driven pulley 4 and the reference value is ± 1% or more, the drive frequency of the stepping motor 1 is changed by ± 1%. As a result, it is possible to prevent the dot interval from becoming conspicuous in a part when recording by the drum shaft 5.

FIG. 7 is a block diagram showing the configuration of the drive device shown in FIG. In this case, a main CPU 9 is provided in the control circuit 7, and the CPU 9 has a rotary switch 10 in addition to the encoder 6 described above.
And a TIMER with a ROM 11 and a CLOCK 12
And 13 are connected. With such a configuration of the control circuit 7, the operation as shown in FIG. 6 described above can be performed.

Next, the reasons for setting the first and second conditions as described above will be sequentially described below with reference to FIGS. In the past, speed control has been performed using an extremely expensive encoder 6 having a peripheral pulse number of about 81,000. However, the cumulative pitch error of magnetic drive differs from the cumulative pitch error of gears. FIG. 2A shows the cumulative pitch error of the magnetic drive mechanism, and FIG. 2B shows the cumulative pitch error of the gears. First, the cumulative pitch error of magnetic drive is gentle and large, as shown in FIG. This shows an example of the cumulative pitch error of the magnetic drive mechanism without control. The drum diameter φ20 coaxial with the driven pulley 4, the dot density 200 DPI, the reduction ratio of the magnetic drive mechanism = the diameter of the driven pulley 4 is shown. / Motor shaft diameter = 10.4. On the other hand, as for the cumulative pitch error of the gear, as shown in FIG. 2B, since the meshing frequency of the gear teeth appears,
In order to control the gear, the control must be performed at a time interval sufficiently smaller than the frequency of the gear teeth. Therefore, when controlling the gear, the greater the number of circumferential pulses of the encoder 6, the higher the control accuracy.
However, in the case of the magnetic drive mechanism, as shown in FIG. 2A, since it is a gradual and large cumulative pitch, if the number of circumferential pulses of the encoder 6 is increased to some extent or more, it is considered that sufficient control is performed. .. Further, it is considered that the control accuracy hardly changes even if the number of circumferential pulses of the encoder 6 is increased further.

Further, in the driven pulley 4 of the magnetic drive mechanism,
A drum shaft 5 (or a driving roller of a recording belt) of a copying machine or a printer is coaxially connected. For this reason,
Since the inter-dot distance is controlled, it is considered that there is a certain relationship between the number of circumferential dots of the drum shaft 5 and the minimum number of circumferential pulses of the encoder 6 that does not reduce the control accuracy. First, the drum shaft 5 is considered first.
This is the case where the number of circumferential dots of and the number of circumferential pulses of the encoder 6 are equal. In such a case, since speed control is always performed once for each dot, it is conceivable that both the single pitch error and the cumulative pitch error are controlled to some extent. As a result of actual measurement, when the number of circumferential pulses of the encoder 6 is almost equal to the number of circumferential dots of the drum and when the number of circumferential pulses of the encoder 6 is further increased, a single pitch error of the driven pulley 4 or There was almost no difference in cumulative pitch error. From this, it is considered that the number of circumferential pulses of the encoder 6 may be made as small as the number of circumferential dots of the drum shaft 5. Therefore, from the viewpoint of cost, it is cheaper to reduce the number of circumferential pulses of the encoder 6 as much as possible. Therefore, reducing the number of circumferential pulses of the encoder 6 to the number of circumferential dots of the drum shaft 5 or less reduces the cost. Necessary considering.

Next, as a second conceivable case, the number of peripheral pulses of the encoder 6 is further reduced. Rotation speed of the driven pulley 4, dot density, drum diameter,
It is considered that it depends on the magnitude of the load torque applied to the drum, the reduction ratio of the magnetic drive mechanism, and the like, but in some cases, the control performance may deteriorate. For example,
As shown in FIGS. 3 (a) and 3 (b), considering a case where control is performed once for one dot and once for two dots, there is a difference between controlled dots and non-controlled dots. They will be lined up, and this will make them stand out on the image.

Considering the measurement results of FIG. 2 (a),
Since the number of circumferential dots is about 500, a cumulative pitch error of about 1.2 μm occurs between dots unless control is performed. Figure 1
Shows the state of the accumulated pitch error of the magnetic drive mechanism when the control is applied. In this case, the cumulative pitch error was reduced to about 1/10. Therefore, from the results of FIG. 2A and FIG. 1, it is considered that the cumulative pitch error is sufficiently reduced by the control, and it is considered that the cumulative pitch error of 1.2 μm is controlled between dots. However, if the control is performed once between two dots, the cumulative pitch error of 2.4 μm will be controlled by the control once.
In the case of a magnetic drive mechanism, since the single pitch error is about 2 μm (standard deviation σ), the single pitch error is significantly increased (when the standard deviation σ of the single pitch error is 2 μm, 1.
Even if the cumulative pitch error of 2 μm is controlled, it is hardly noticeable, but if the cumulative pitch error of 2.4 μm is controlled, the single pitch error obviously becomes large).

The standard deviation σ of the single pitch error is 2μ.
When m, a maximum cumulative pitch error of 3σ = 6 μm occurs between 1 dot, but it becomes 12 μm between 2 dots, and 12 μm at the cumulative pitch error of ± 15 μm as shown in FIG.
When the cumulative pitch error of the driven pulley 4 is increased, the cumulative pitch error is obviously increased.
The amplitude of the waviness of the accumulated pitch error of one cycle per 1 rotation is about 15 μm, and further, it is 12 μm locally.
The cumulative pitch error of may be added). In addition to the accumulated pitch error, there is a cause of color deviation (color recording) such as a difference in average peripheral speed, so that the allowable range is exceeded.

Summarizing what has been described so far, the amplitude of the cumulative pitch error of the magnetic drive mechanism without control is expressed as a
(150 μm in FIG. 2A), the number of circumferential dots is n, the cycle of load fluctuation is T, the amplitude of the cumulative pitch error is b (about a / 10 in actual measurement up to now), and α and α ′ are 1 or less. And the coefficient of

[0027]

[Equation 3]

If N is satisfied, it is considered that the control once between N dots does not significantly affect the cumulative pitch error or the single pitch error. However, as shown in FIG.
Considering the measurement results of FIG. 1 by the equations (1) and (2), N = 1.

From the above, the maximum number of circumferential pulses of the encoder 6 is the number of circumferential dots of the drum, and the cost is low even if the single pitch error or the cumulative pitch error becomes a little large. If this is not the case, it is sufficient to reduce the number of circumferential pulses of the encoder 6 as shown in the above-mentioned “first condition” within the permissible range of the single pitch error and the cumulative pitch error, thereby improving the control performance. The cost can be reduced without lowering. Further, even if the sampling frequency for control is made higher than the frequency of the output pulse of the encoder 6, it is useless, so that the sampling frequency is set to the encoder 6 as shown in the above-mentioned “second condition”.
It is preferable that the output frequency is substantially the same as the output frequency of the CPU. By reducing the sampling frequency in this way, the operating rate of the CPU 9 can be lowered. Therefore, from the above, when the CPU 9 of the printer body has a margin,
The control can be performed by the CPU 9 of the printer body.

Therefore, in this embodiment, the drum shaft 5
When the number of circumferential dots of the encoder 6 is determined, how large the number of circumferential pulses of the encoder 6 is, the encoder 6 having a high image quality (that is, rotation unevenness such as a single pitch error of the driven pulley 4 and a cumulative pitch error) is obtained. Therefore, it is possible to clarify that the cost of the encoder 6 is almost the same as the above, and the cost of the encoder 6 can be suppressed as low as possible within the range where the control performance is not affected.

[0031]

According to the first aspect of the present invention, by interposing a friction member between the drive shaft and the driven shaft, the driving force obtained by the drive shaft is applied to the driven shaft by the frictional force of the friction member. In the rotation transmission drive device for transmitting and transmitting the encoder to the driven shaft, detecting the difference between the output frequency of the encoder and the reference frequency, and changing the rotational speed of the driven shaft, the number of peripheral pulses of the encoder Since the peripheral pulse number setting means for setting the number below the number of peripheral dots of the driven axis is provided, it is possible to reduce the number of peripheral pulses of the encoder while keeping the control accuracy of the gentle and large accumulated pitch error almost the same. Moreover, since the encoder can be manufactured easily, the cost can be further reduced.

According to a second aspect of the invention, in the first aspect of the invention, the sampling frequency for control is set to be the same as the frequency of the output pulse of the encoder. CP
Since the operating rate of U can be reduced, the cost can be further reduced.

[Brief description of drawings]

FIG. 1 is a waveform diagram showing a state of a cumulative pitch error of a magnetic drive mechanism when the number of circumferential pulses of an encoder is the same as the number of circumferential dots of a drum.

2A is a waveform diagram showing a state of cumulative pitch error of a magnetic drive mechanism, and FIG. 2B is a waveform diagram showing a state of cumulative pitch error of a gear.

FIG. 3A is an explanatory diagram showing a state of 1 control between 1 dots, and FIG. 3B is an explanatory diagram showing a state of 1 control between 2 dots.

FIG. 4 is a configuration diagram showing an overall configuration of a rotation transmission drive device.

FIG. 5 is a characteristic diagram showing a control method of a control circuit.

FIG. 6 is a flowchart of a control method.

FIG. 7 is a block diagram of a rotation transmission drive device.

[Explanation of symbols]

 2 Drive shaft 3 Friction member 4 Driven shaft 6 Encoder

Claims (2)

[Claims] 1. A friction member is interposed between a drive shaft and a driven shaft, whereby the driving force obtained by the drive shaft is transmitted to the driven shaft by the frictional force of the friction member and the driven shaft. In the rotation transmission drive device for connecting the encoder to, detecting the difference between the output frequency of the encoder and the reference frequency, and changing and controlling the rotation speed of the driven shaft,
A rotation transmission drive device comprising a peripheral pulse number setting means for setting the number of peripheral pulses of the encoder to be equal to or less than the number of peripheral dots of the driven shaft. 2. The rotation transmission drive device according to claim 1, wherein the sampling frequency for control is set to be the same as the frequency of the output pulse of the encoder.