JPH04175551A - Drive device - Google Patents

Abstract

PURPOSE:To damp effectively the overshooting phenomenon at the transfer from acceleration to constant speed movement by fitting a rotary shaft with an inertia body which is capable of rotating in a single piece with the rotary shaft and can make relative rotation therewith only within a certain angle range. CONSTITUTION:An optical table 5 and a rotary inertia body 26 receive a transmissive force from a drive shaft 11 rotating in the direction of arrow X while a joining pawl 28 is in contact with the surface (d) of a groove 19 and are rotational accelerated consolidatedly. Then an overshoot will be generated and the optical table 5 begin decelerating, but the inertia body 26 continues moving at a constant speed with the inertial force because it is relative rotatable with the drive shaft 11 during the period when the pawl 28 moves from the surface (d) to (e) in with a groove 29 in a disc 30 i.e., within a specific angle range. When the pawl 28 comes in contact with the surface (e) of the groove 19, the optical table 5 will be in decelerating, but it integrally rotates again while receiving the drive force of the inertia body 26. Meantime the inertia body 26 continues emitting the rotational energy, and the two members 5, 26 are stabilized at constant speed, and scan over a document is made thereafter with this constant speed.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a reciprocating device used in a copying machine, a document reading device, etc., which illuminates the document by relatively moving an optical system as a movable body and the document. It relates to a drive device for a mechanism.

(Prior Art) Conventionally, copying machines and document reading devices have been provided with an optical system or a scanning device that reciprocates the document table in order to scan (illuminate) a document placed on the document table. The main driving methods for these are to use a DCC gear motor or stepping motor as the driving source, and to transmit the driving force using a gear train, timing belt (pulley), etc., or a combination of these to perform scanning. be.

In recent years, there has been a tendency for stepping motors to be used frequently because they have little positional deviation and are easy to control.

FIG. 6 shows an example of the above scanning device. In the figure, a document (
(not shown) is illuminated by a light source 101, and its reflected light is imaged onto a linear reading sensor (reading unit) 103 by a rod lens array 102. As a result, image information for one line of the original can be obtained. Furthermore, the optical system is fixedly installed on the optical bench 104, and the sliding member 10
By moving (scanning) the document in the direction of the arrow a on the rail 106 via the guide 5, image information of the entire document is obtained.

On the other hand, the driving force for moving the optical bench 104 is a wire 107 fixed to the optical bench 104 and a wire 107 attached to the optical bench 104.
Drive pulley 108 that winds up 7, idle pulley 110
This is performed by a drive device including a drive source (not shown) such as a motor that rotates a drive shaft 109 integrated with a drive pulley 108.

Furthermore, when the scanning of the entire document is completed, the optical bench 104
returns to the leading edge of the document in preparation for the next scan (return, move in the direction of the arrow in the figure).

FIG. 7 shows the moving speed of the optical bench 104 on the vertical axis and time on the horizontal axis. The optical bench 104, which was initially in a stationary state, was accelerated to a scanning speed of 1
=1, vl is achieved (accelerated movement process).

The optical bench 104, which has reached a constant speed, starts reading the original at t=tz (the leading edge of the original) and ends at t=t3 (constant speed movement process). Thereafter, the optical bench 104 enters a deceleration movement process and stops. Next, it enters an acceleration movement process in the opposite direction to the scanning direction, accelerates to a return speed V2, moves at a constant speed, and returns to its original position through a deceleration movement process.

(Problems to be Solved by the Invention) However, the above drive device has the following problems.

■ A phenomenon in which the speed increases (overshoot phenomenon) occurs when the optical bench 104 transitions from an accelerated movement process to a constant speed movement process, and the speed fluctuation caused by this is not sufficiently attenuated even when 1=12 (Fig. Middle A): So-called image blur occurs, where the read image expands and contracts compared to the original.

■ Normally when returning, it is necessary to move much faster than when scanning the original to increase the copy speed (v +
<V 2 ), the overshoot phenomenon at this time is larger than that during scanning, and the overshoot phenomenon causes vibrations in the entire document reading device (C in the figure).

In order to solve the above problem, it is possible to increase the run-up distance of the optical bench 104 and start reading the original after the overshoot phenomenon has sufficiently attenuated, or to extremely increase the rigidity of the entire device to make it less likely to vibrate. . but,
This approach is not practical because it not only makes the document reading device extremely large due to the run-up distance of the optical bench 104, but also increases the weight of the entire device and increases the copying time.

This invention is intended to solve the above problem, and effectively damps the overshoot phenomenon when a moving object shifts from accelerated movement to constant speed movement without changing the size and weight of the device or the moving time of the moving object. The purpose of the present invention is to provide a drive device that can

Another purpose is to reduce the overshoot phenomenon when the optical bench shifts from accelerated movement to constant speed movement without changing the size and weight of the entire device such as a document reading device or copying machine, or the illumination time by the optical bench. It is an object of the present invention to provide a drive device that can effectively damp.

(Means for Solving the Problem) In order to achieve the above object, the present invention provides a drive source that generates a driving force, a power transmission means that has a rotating shaft that transmits the driving force, and a power transmission means that transmits the driving force through the power transmission means. A drive device having a moving body that moves reciprocatingly by a driving force of It is characterized by the installation of an inertial body that can rotate relative to the rotation axis only within an angle of .

The moving body is an optical bench that includes a light source that illuminates the original and a reading section that reads the original image using light reflected from the original.

(Function) The function of the present invention based on the above configuration is that the driving force generated by the drive source is transmitted to the movable body via the power transmission means, and the movable body reciprocates.

When the moving body shifts from accelerated movement to constant speed movement, it once exceeds a constant speed, and then decelerates in response to the driving force of the driving source. When moving at an accelerated rate, the inertial body rotates integrally with the rotation axis, but when the speed of the moving body attempts to decrease below a constant speed, the inertial body rotates independently within a predetermined angle. death,
The speed of the moving object is stabilized at a constant speed because rotational energy due to inertia force is applied to the rotating shaft to suppress a decrease in speed.

Further, the driving force generated by the driving source is transmitted to the optical bench via the power transmission means, and the optical bench reciprocates. At this time, the light source illuminates the original when the optical bench moves at a constant speed, and the reflected light is guided to the reading section to read the original image.

When the optical bench shifts from accelerated movement to constant speed movement, it once exceeds a constant speed, and then decelerates in response to the driving force of the driving source. During accelerated movement, the inertial body rotates integrally with the rotation axis, but when the speed of the optical bench decreases below a constant speed, the inertial body rotates independently within a predetermined angle. death,
The speed of the optical bench is stabilized at a constant speed because rotational energy due to inertia force is applied to the rotation axis to suppress a decrease in speed.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, taking a document reading device as an example.

In FIG. 1.2, an original (not shown) placed on a transparent original platen glass l is illuminated by a light source 2, and the reflected light is sent to a line-shaped reading sensor (reader) by a rod lens array 3. Section) 4. The reading sensor 4 outputs a signal corresponding to the intensity of light of this image, and this signal is transmitted to an arithmetic circuit (not shown) to obtain image information for one line of the original. The optical system is fixedly mounted on an optical bench (moving body) 5, and on both sides of the optical bench 5, drive pulleys 10 (10a, 10b) are wound around, and rotatable idler pulleys 8 are rotated. Two driving wires 9 (9a, 9b) are stretched, and both ends thereof are fixed to fixing parts 5a at both ends of the optical bench. A tension coil spring 12 is applied to the idler pulley 8 to apply appropriate tension to the drive wire 9.

The drive pulley 10 is fixed to a drive shaft (rotating shaft) 11, and the driving force of a stepping motor 20, which is a drive source, is transferred to a drive timing pulley 22 fixed to an output shaft 21 of the motor and to the drive shaft 11. The power is transmitted to a fixed driven timing pulley 23 via a power transmission means 25 such as a rotated timing belt 24, and rotates. Then, the optical bench 5 receives the above driving force and moves to the rail 7 via the sliding member 6.
(7a, 7b) can be moved arbitrarily in the force directions a' and b' in the figure.

Further, in the present invention, as shown in FIG. 3, an inertial body 26 is rotatably supported on the drive shaft 11 via a bearing portion 27 in the power transmission means 25, and a connecting claw 28 is provided on one end surface of the inertial body 26.
is permanently installed. Further, a disk 30 having a groove 29 having a certain width is fixed on the drive shaft 11 side, and the connecting claw 2
8 is located within the groove 29.

The operation of the drive device with the above configuration will be explained using FIG. 3.4.5. FIG. 4 shows the moving speed of the optical bench 5 on the vertical axis and time on the horizontal axis. The optical bench 5, which is initially in a stationary state (start position), begins to move when the stepping motor 20 starts operating, and the driving force is accelerated to the scan speed V, and at t=t, l, the optical bench 5 achieves the scan speed v1 (acceleration movement process )
. Here, the stepping motor 2o is controlled to stop accelerating and move at a constant speed V, but an overshoot phenomenon occurs in the scanning system including the optical bench 5, and The optical bench 5 moves while performing the fluctuation.

FIG. 5 shows details of section A' in FIG. 4. Conventionally, as shown by the dotted line in the figure, the overshoot phenomenon continues without slowing down, but according to the present invention, the optical bench 5 and the inertial body 26 move in the direction of the arrow X with the connecting claw 28 in contact with the surface d of the groove 19. The rotating drive shaft 11 receives a transmission force and is integrally accelerated in rotation. Next, overshoot occurs and t ” t a
The speed of the optical bench 5 starts to decrease when Since it is relatively rotatable, it continues to move (rotate) at a constant speed v3 due to inertia force. Then, when the connecting claw 28 comes into contact with the surface e of the groove 19 at t'' ts, the speed of the optical bench 5 is decreasing, but it rotates as a unit again while receiving the driving force from the rotating inertia body 26. During this period, the inertial body 26 continues to emit rotational energy, and at t = j s, the optical bench 5 and the rotating inertial body 26 stabilize at a constant speed v1, and thereafter scan the original at a constant speed (constant speed movement process). .

As described above, according to the present invention, speed fluctuations due to overshoot of the optical bench 5 are attenuated much faster than in the conventional example. This prevents expansion and contraction of the read image, so-called image blurring.

Further, after the optical bench 5 finishes the constant speed movement process, it enters a deceleration movement process, moves to a certain extent, and then stops. Immediately after stopping, the optical bench 5 starts moving in the b' force direction to return to its original position (the disc 30 rotates in the direction of arrow Y).

Normally, when returning, the moving speed v2 is much faster than when scanning the original because the copying speed is increased, so the speed fluctuation amplitude of overshoot is large and causes vibrations to the entire machine, but as mentioned earlier, according to the present invention, , the overshoot decays very quickly (0 parts), so the oscillations are very small. The optical bench 5 then moves further in the direction b', continues at a constant speed, then goes through a deceleration movement process, returns to its original position, and stops, preparing for the next scan.

Furthermore, although the inertial body 26 is provided on the drive shaft 11 in this embodiment, the same effect can be obtained anywhere within the power transmission means 25 of the drive device. It goes without saying that you may support the 21st.

(Effects of the Invention) As explained above, according to the drive device according to the present invention,
Quickly attenuates the overshoot phenomenon when moving a moving object from accelerated movement to constant speed movement, without increasing the run-up distance of the moving object, increasing the size of the device, or reducing the speed and spending a lot of time. effective.

Therefore, if used to drive the scanning of the optical bench of a copying machine or original reading device, a high-quality device with high accuracy and low vibration without image expansion/contraction (image blurring) can be achieved while minimizing the size and cost of the device. There is an effect that can be provided.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the main parts of the present invention applied to a drive device of a document reading device, FIG. 2 is a side view of FIG. 1, and FIG. 3(a)
, (b) is a sectional view and side view showing the inertial body according to the present invention, FIG. 4.5 is a graph showing the relationship between the moving speed of the optical table and time in the present invention, and FIG. 6 is a document reading in the conventional example. FIG. 7, a side view of the apparatus, is a graph showing the relationship between the moving speed of the optical bench and time in a conventional example. Explanation of symbols 5... Optical bench (moving body) 2... Light source 11... Drive shaft (rotating shaft) 4... Reading sensor (reading section) 20... Stepping motor (drive source) 25. ...Inertia body 26...Power transmission means Fig. 2 Fig. 3 TI! J (o) (b) Figure 4 a' Figure 5

Claims (2)

[Claims] (1) A drive source that generates a driving force, a power transmission means that has a rotating shaft that transmits the driving force, and a reciprocating movement due to the driving force transmitted through the power transmission means, and during the reciprocating movement, the acceleration movement becomes constant. In a drive device having a moving body that moves at high speed, the rotary shaft has an inertia that can freely rotate integrally with the rotary shaft and can rotate relative to the rotary shaft only within a predetermined angle. A drive device characterized by having a body attached thereto. (2) The drive device according to claim 1, wherein the movable body is an optical bench having a light source that illuminates the document and a reading section that reads the document image using reflected light from the document.