JPS622607Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vibration damping and buffering device for an optical scanning system or a document mounting table of a copying machine or the like.

The optical scanning system used in conventional high-speed copying machines scans at a constant speed when an image is formed on a photoreceptor, and returns at a high speed to save wasted time. However, the higher the speed of return, the greater the acceleration, which makes damping and damping the optical scanning system more difficult. If the next copying operation is started before this vibration is sufficiently attenuated, a clear image cannot be obtained due to the remaining vibration, which is an obstacle to increasing the speed of the copying machine.

Generally, in the optical scanning system of a high-speed copying machine, the displacement of the optical scanning system upon return is returned smoothly along a cycloid curve or a displacement curve of a high-order polynomial in order to prevent vibration of the optical scanning system. FIG. 1 shows changes in displacement 1, velocity 2, and acceleration 3 of the optical scanning system with respect to time t in that case.

In Figure 1, 4 is the scanning time, 5 is the scanning return time, and 6
is one copy cycle.

The force 9 transmitted from the optical scanning system to the prime mover system, which moves as shown in Figure 1, is the resultant force of the force 8 caused by the spring used as a means to return the optical scanning system and the inertial force 7 of the optical scanning system, and is the force caused by the spring. 8 is proportional to the displacement 1 of the optical scanning system, and the inertial force 7 is proportional to the acceleration 3. As a result, if the direction of the force is set opposite to the scanning direction, the result will be as shown in FIG.

In high-speed copying machines, the optical scanning system is generally driven by a cam. For example, the optical scanning system shown in FIG. 3 obtains a desired movement of the scanning lens 16 by rotating a cam 10 using a prime mover.

At this time, the cam 10 is the cam follower 1 during scanning.
Push up spring 1 and press return spring 1 when scanning back.
8 presses the cam follower 11 against the cam 10. This is called a positive scan.

It is well known that the pressure angle of the cam follower 11 changes as the cam 10 rotates, and as a result, a load torque (the direction of which is negative during scanning and when returning from scanning) is generated on the camshaft, and the prime mover is activated as shown in Fig. 4. It is operated with a load torque curve such as 20.

Since the operating direction of the cam follower 11 changes at the top dead center P and bottom dead center Q of the cam 10, the differential coefficients of the displacements of the cam 10 and the cam follower 11 are reversed before and after this point.

That is, it is 0 at point P and point Q. To illustrate this mechanically, as shown in FIG. 11, the tangent line coincides with the rotation direction, and there is no load torque.

On the other hand, in the middle of P-Q, as shown in FIG. 12, there is a torque (in the negative direction) due to the spring force, and the magnitude of the load torque differs depending on the rotation angle of the cam 10.

The load torque curve described above is positive in the direction in which it rotates to overcome the load. In other words, this indicates that the prime mover is being rotated by a reverse load between P and Q.

Reference numeral 19 in FIG. 4 is a force transmitted to the cam 10, which is the same as the force when motion is transmitted simply in a system where a spring force acts, regardless of the presence of the cam 10. Therefore, when the cam follower shaft or the drive shaft itself is driven by the prime mover without using the cam 10, the torque of the prime mover corresponds to the inverted sign of 9.

It is also possible to use the force of the return spring during scanning so that the cam 10 pushes up the cam follower 11 during the scanning return (this is called positive return).

In other words, the cam follower 11 is always in contact with the cam 10 under pressure, and in a stationary state, the bottom dead center Q
It is in.

When moving from the bottom dead center Q to the top dead center P, either a long stroke (scanning→scanning return) or a short stroke (scanning return→scanning) can be selected.
The former is the positive scan mentioned above, and the 12th
In the case shown, the cam 10 rotates in a counterclockwise direction.

The latter is called a positive return, and in the case of FIG. 12, the cam 10 rotates clockwise.

Therefore, in positive scan, one rest,
2 scans (uniform motion), 3 scans back, and 4 rests, while positive return has 1 rest and 2 rests.
Return to scan, 3 scans (uniform motion), and 4 rest.

The force 22 exerted on the prime mover system in this case is the fifth
It will look like the figure. 21 is the force transmitted to the cam.
Positive return has the disadvantage that the load is maximum when it is positive, and the output of the prime mover required for driving must be increased, making it unsuitable for high speeds.

However, when positive scanning is selected, the maximum load becomes negative, causing rotational fluctuations in the prime mover, and as a result, the cam does not rotate at a constant speed, and therefore the required cycloidal or high-order polynomial displacement curve cannot be obtained.

In order to improve this problem, it is conceivable to incorporate into the optical scanning system a known damping damper (hereinafter referred to as a damper) that absorbs energy in proportion to the operating speed, such as an air damper or an oil damper. If the damper is activated during the return of the optical scanning system, it will provide more effective damping and the force exerted by the return spring will be smaller.

FIG. 6 shows the force 25 transmitted from the optical scanning system to the prime mover system when the damper is operated during the return 23 of the optical scanning system. 24 is the damping force by the damper.

When the damper is incorporated into the optical scanning system as shown in FIG. 6, the fluctuations in the force 25 transmitted to the prime mover system are smaller than in FIG. 3.

However, clear images (especially fine resolution)
It is still insufficient to obtain the

This is because vibrations still remain at the start of scanning.

Therefore, in order to obtain the desired image, it is necessary to perform an extra scan to start copying after this vibration has started to a certain extent, or to extend the return time to a certain extent to slow down the fluctuations in force and perform optical scanning. Because system vibration was suppressed, there was a limit to how fast optical scanning copying machines could be made.

The present invention was developed in view of the above circumstances, and its purpose is to reduce the absolute value of the prime mover load torque that occurs when the optical scanning system returns to scanning, so that it can be used for the next scanning by returning to scanning. In addition to preventing vibrations, we also use vibration absorption devices during scanning to suppress vibrations or vibrations that occur due to unspecified reasons during scanning. It is about providing.

Hereinafter, the present invention will be explained with reference to FIG. 7 and subsequent figures. In the drawing, 10 is a rotationally driven cam, and 3
6 is a shaft body supported by the frame.

A lever 11 is attached to the shaft body 36, and a cam follower 11a at the end of the lever 11 is in external contact with the cam 10. A pulley 12 is fixed to the shaft body 36.

In the drawing, 26 is a drive shaft supported by the frame, and pulleys 37 and 14 are fixed to this drive shaft 26. A drive wire 13 is hung between the pulley 12 and the pulley 37. In addition, 38 in the drawing is a pulley that is pivotally supported by the frame, and this pulley 38
A drive wire 15 is hung between the pulley 14 and the pulley 14.
A scanning carriage 17 is attached to this drive wire 15, and a lens 16 is provided on the scanning carriage 17. 18 in the drawing is a return spring.

The drive shaft 26 drives the optical scanning system A as described above, and has an angular velocity W during scanning and _{a normal angular velocity W 1 during} scanning return, at a specified velocity having the relationship (W ₁ > W ₀ ) therebetween. (e.g. cycloid) Rotates due to change.

Gears 29 and 29 are connected to the drive shaft 26 via one-way clutches 27 and 28 that engage in different rotational directions.
There are 30.

The one-way clutch 27 is engaged during scanning, and the other one-way clutch 28 is engaged when returning from scanning.

31 in the drawing is a vibration absorber 31, and the vibration absorber 31 is a sealed container 42 as shown in FIG.
A rotor 44 is attached to the stator 4 and has a rotor 44 sealed with a liquid having an appropriate viscosity therein and supported by a support 43 of a container 42.
When the liquid between the rotor 44 and the stator 45 is sheared, a resistance force is generated and vibrations are absorbed. Gears 34 and 35 are attached to the shaft 32 of the vibration absorber 31 by a key 33, and the gear 34 is attached to the gear 29, and the gear 3 is attached to the gear 29.
5 are meshed with the gears 30, respectively.

Thus, the rotation of the cam 10 causes the cam follower 11a, the arm 11, the shaft 36, the pulley 12,
Drive shaft 26 via drive wire 13 and pulley 37
When rotates in the scanning direction, the shaft 32 of the vibration absorber 31 is rotated by the one-way clutch 27 via the gears 29, 34.

The vibration absorber 31 is preferably one that generates force in proportion to speed, and for example, a fluid dumppot filled with viscous fluid, a brake motor, or the like may be used.

When residual vibration due to scanning return or vibration due to unspecified reasons occurs in the drive shaft 26, the vibration absorber 31 generates a force to resist it and damps the vibration.

The force generated by the vibration absorber 31 is transmitted through the gears 27 and 34.
It can be adjusted by selecting the gear ratio. During scanning, the one-way clutch 28 is in a free state, so that the rotation of the shaft 32 of the vibration absorber 31 causes the gear 30 to idle on the drive shaft 26 by means of the gear 35.

When the drive shaft 26 rotates in the return scan direction, the one-way clutch 28 is engaged and therefore the gears 30,3
5, the shaft 32 of the vibration absorber 31 is rotated in the opposite direction to that during scanning.

Since the load torque at the time of scanning return has a peak at a fixed position, it is desirable to know in advance the load torque change of the optical scanning device and to operate the vibration absorbing device so that the change is minimized.

For this purpose, gear ratios are given to the gears 30, 35 so as to generate an optimum damping force.

When returning from scanning, the one-way clutch 27
is free, so the rotation of the shaft 32 of the vibration absorber 31 causes the gear 29 to idle on the drive shaft 26 via the gear 34.

When the damper equipped with the vibration absorber 31 is used in the optical scanning system of a copying machine, the relationship between the damping force 40 by the damper and the force 41 transmitted to the prime mover is as shown in FIG.

As the present invention has been described in detail above, the vibration absorber 31 absorbs vibrations generated during scanning, and when returning from scanning, suppresses fluctuations in the load torque due to the optical scanning system and prevents speed fluctuations of the prime mover. Since it acts on vibrations in the scanning system, by applying it to high-speed copying machines, it is possible to obtain clear images that were previously impossible.

It goes without saying that the present invention can also be applied to free-flyback copying machines and moving platen copying machines.

[Brief explanation of drawings]

Figure 1 is a displacement, velocity, and acceleration diagram of the scanning lens or mirror during the copying cycle. Figure 2 is an explanatory diagram of the inertial force, spring force, and force transmitted to the prime mover of the optical scanning system. Figure 3 is an illustration of the force transmitted to the prime mover using a cam. A perspective view of the optical scanning system drive device, Figures 4 and 5 are explanatory diagrams of the force transmitted to the cam and the force transmitted to the prime mover in the optical scanning system drive device using a cam, and Figure 6 is a diagram during the scanning return. An explanatory diagram of the force transmitted to the cam and the force transmitted to the prime mover when a damper is inserted, Figure 7 is a front view of an embodiment of the present invention, Figure 8 is a longitudinal sectional view of the same, and Figure 9 is the optical system according to the present invention. FIG. 10 is a perspective view of an optical scanning system drive device equipped with a scanning system damping damping device; FIG.
Figure 12 is an explanatory diagram of the operation of the cam and cam follower.
FIG. 13 is a longitudinal sectional view of the vibration absorber. 26 is a drive shaft, 27 and 28 are one-way clutches,
31 is a vibration absorber, and 29, 30, 34, and 35 are gears.

Claims (1)

[Scope of utility model registration request] Drive shaft 2 that drives the optical scanning system or document mounting table
6, a one-way clutch 27 that has a rotation transmission function when the optical scanning system or the document placement table reciprocates, a one-way clutch 28 that has a rotation transmission function when the scanning system or the document placement table moves back and forth, and a one-way clutch 28 that rotates together with these clutches 27 and 28. The shaft 3 of the vibration absorber 31 is provided with gears 29 and 30 to absorb vibrations by rotating a rotor provided on the shaft 32 in a viscous fluid in a closed container.
2. A vibration damping and buffering device for an optical scanning system of a copying machine or the like or a document mounting table, characterized in that gears 34 and 35 are provided which mesh with the gears 29 and 30 at an appropriate reduction ratio.