Abstract:
The present invention provides a drive controlling apparatus used in a sheet supplying apparatus including a lift/lower sheet supporting device for supporting a sheet, a sheet supply mechanism for feeding out the sheet supported by the sheet supporting device, a biasing mechanism for biasing the sheet supporting device toward the sheet supply mechanism, and a separating mechanism for separating the sheet supporting device from the sheet supply mechanism in opposition to a biasing force of the biasing mechanism, and wherein the sheet urged against the sheet supply mechanism by the biasing mechanism is fed out by the sheet supply mechanism, said drive controlling apparatus adapted to transmit a driving force for operating the separating mechanism from a drive source and comprising a drive side device connected to the drive source, a driven side device connected to the separating mechanism, and a play setting device for providing a play for not transmitting the driving force within a predetermined range between the drive side device and the driven side device.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a drive controlling apparatus, and more particularly, it relates to a drive controlling apparatus used in a sheet supplying apparatus provided in an image forming apparatus. 
     2. Related Background Art 
     Conventional image forming apparatuses such as copying machines, printers and the like each has a sheet supplying apparatus in which a drive controlling apparatus for controlling the driving of a sheet supply roller is used. 
     An example of a conventional drive controlling apparatus for a sheet supply roller is shown in FIG. 18. Such a drive controlling apparatus includes a sheet cassette portion, a drive portion, a sheet supply roller portion and a lock portion. Now, these portions will be briefly described. 
     First of all, the sheet cassette portion comprises a sheet cassette 108 and sheets 100, and the sheet cassette is provided with an intermediate plate 108 pivotable around a fulcrum 108a, and projections 108c are provided on a downstream (in a sheet supplying direction) end portion of the intermediate plate. Springs 108d disposed below the intermediate plate serve to bias the intermediate plate 108b in a direction shown by the arrow X. 
     Forces exerted by the springs 108d act on cams 121a of the sheet supply roller portion 121 through the projections 108c to tend to rotate the cams in a direction shown by the arrow Y. Thus, a sheet supply roller 109, a notched gear 121b and a locking member 121c which are secured to a rotary shaft 120 together with the cams 121a also tend to rotate in the direction Y. However, since a locking pawl 121d formed on the locking member 121c is engaged (locked) by a stopper 122, the sheet supply roller the sheet supply roller portion is entirely held stationary. 
     When the locking pawl 121d is disengaged from the stopper 122, the entire sheet supply portion 121 is rotated in the direction Y by a predetermined angle, with the result that a toothed portion of the notched gear 121d is engaged by a drive gear 127 rotated by a motor M in a direction W. Consequently, the sheet supply portion 121 is rotated by one revolution until a condition shown in FIG. 18 is restored again. After one revolution, when a non-toothed portion 121e of the notched gear 121b is opposed to the drive gear 127 again, the locking pawl 121d is locked by the stopper 122 again. 
     The engagement and disengagement between the locking member 121c (locking pawl 121d) and the stopper 122 is effected by a spring 122c for biasing the stopper 122 in a direction Z and a lock releasing portion for urging the stopper 122 in opposition to the force of the spring 122c. 
     That is to say, when the disengagement is effected, a locking member 123c of the lock releasing portion is rotated to urge the stopper 122 in opposition to the force of the spring thereby to disengage the stopper 122 from the locking pawl 121d of the sheet supply roller portion, thus starting the rotation of the sheet supply roller portion. Other than the above disengagement, the stopper 122 is always urged against the locking member 121c of the sheet supply roller portion by means of the spring 122c. 
     Now, the lock releasing portion will be described. 
     The lock releasing portion includes a cam 123a, a notched gear 123b, a locking member 123c (which are mounted on a common rotary shaft), a leaf spring 125 for applying a rotational force to the cam 123a, and a solenoid 126 for controlling the timing of rotation. In the condition shown in FIG. 18, although the cam 123a tries to rotate in a direction V by the action of the leaf spring 125, since a locking pawl 123d of the locking member 123c is locked by a solenoid actuator 126a, the entire lock releasing portion is held stationary. 
     When current is applied to the solenoid 126 to retract the solenoid actuator 126a toward the solenoid 126, the locking pawl 123d of the locking member 123c is disengaged from the solenoid actuator 126a, with the result that the cam 123a is rotated by the action of the leaf spring 125 by a predetermined angle. During this rotation, since a toothed portion of the notched gear 123b is engaged by the drive gear 127, the cam 123a continues to rotate by one revolution. After one revolution of the cam 123a, when a non-toothed portion of the notched gear 123b is opposed to the drive gear 127 again (FIG. 18), the locking pawl 123d of the locking member 123c is locked by the solenoid actuator 126a again, thereby stopping the cam. 
     In such a drive controlling apparatus using the notched gear, a force for rotating the notched gear until the toothed portion is engaged by the drive gear (this force is referred to as &#34;rotation starting force&#34; hereinafter) is required. 
     However, in the above-mentioned conventional drive controlling apparatus, as mentioned above, since the rotation starting force is obtained by the springs 108d disposed below the intermediate plate 108b and is transmitted directly to the notched gear 121b through the cams 121a of the sheet supply roller portion 121, the rotation starting force becomes excessive. The reason is that the springs 108d must provide a strong biasing force sufficient to urge the sheets 100 stacked in the cassette against the sheet supply roller 109 and this strong biasing force acts on the cams 121a as the rotation starting force. 
     However, due to such strong rotation starting force, the following problems arise. Firstly, since the strong rotation starting force increases the locking force between the locking pawl 121d of the sheet supply portion 121 and the stopper 122, it is impossible to release such a locking force by using a solenoid, and, thus, the above-mentioned lock releasing portion must be provided. As a result, the entire apparatus becomes complicated. 
     Secondary, due to the strong rotation starting force, after the lock is released, when the notched gear 121b is engaged by the drive gear 127, the excessive force acts on the drive gear, with the result that the rotational speed of the drive gear is increased by an amount corresponding to backlash between a gear of the motor M and the drive gear (refer to FIG. 19). 
     Other than the above-mentioned arrangement in which the rotation starting force is obtained by the springs disposed below the intermediate plate, even when an arrangement in which a rotation starting force is obtained from an independent spring is used as disclosed in Japanese Patent Application Laid-open No. 2-193830, a biasing force of such a spring acts as a rotational force for rotating a sheet supply roller via a cam, and, when a notched gear is engaged by a drive gear after the lock is released, the excessive force also acts on the drive gear. 
     The increase in the rotational speed of the drive gear affects an influence upon all of gears associated with the drive gear. For example, as is in a normal case, when the drive gear is associated with a convey roller gear for directly conveying a sheet to a transfer portion, a rotational speed of the convey roller is also increased to push the sheet into the transfer portion excessively, thereby causing deviation of an image and worsening image quality. Further, the convey speed of the entire convey portion is unbalanced, thereby causing sheet jam. 
     The above problems may be caused in general drive controlling apparatuses. Thus, there is a need for providing a drive controlling apparatus for transmitting rotation from a drive source to a rotary shaft, in which the initiation of rotation of the rotary shaft does not affect an influence upon the drive source. 
     SUMMARY OF THE INVENTION 
     The present invention aims to solve the above-mentioned conventional problems by providing an adequate rotation starting force by a mechanism other than springs disposed below an intermediate plate and cams of a sheet supply portion, and an object of the present invention is to provide a drive controlling apparatus in which a construction of a lock releasing mechanism is simple and the number of parts is reduced and productivity and drive controlling accuracy are excellent. Another object of the present invention is to provide a sheet supplying apparatus in which productivity is improved and a sheet supply roller is stabilized by utilizing such a drive controlling apparatus. A further object of the present invention is to provide an image forming apparatus in which productivity is improved and sheet supplying accuracy and image forming accuracy are also improved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is an exploded perspective view of a sheet supplying apparatus according to a preferred embodiment of the present invention, and FIG. 1B is a schematic sectional view of the sheet supplying apparatus; 
     FIG. 2A is an enlarged view showing a portion indicated by the arrow A in FIG. 1B, and FIG. 2B is a view showing a condition immediately before a condition of FIG. 2A is reached; 
     FIGS. 3A, 3B, 3C and 3D are sectional views for explaining an operation of the sheet supplying apparatus; 
     FIGS. 4A, 4B, 4C and 4D are sectional views for explaining an operation of a sheet supplying apparatus according to another embodiment of the present invention; 
     FIGS. 5A, 5B, 5C and 5D are sectional views for explaining an operation of a sheet supplying apparatus according to a further embodiment of the present invention; 
     FIG. 6 is an exploded perspective view of a sheet supplying apparatus according to a still further embodiment of the present invention; 
     FIG. 7 is an exploded perspective view of a sheet supplying apparatus according to a further embodiment of the present invention; 
     FIG. 8 is an exploded perspective view of a sheet supplying apparatus according to a still further embodiment of the present invention; 
     FIGS. 9A, 9B, 9C and 9D are sectional views for explaining an operation of the sheet supplying apparatus of FIG. 8; 
     FIG. 10 is an exploded perspective view of a sheet supplying apparatus according to a further embodiment of the present invention; 
     FIG. 11 is an exploded perspective view of a sheet supplying apparatus according to a still further embodiment of the present invention; 
     FIG. 12 is an exploded perspective view of a sheet supplying apparatus according to a further embodiment of the present invention; 
     FIG. 13 is a side view, in partial section, of the sheet supplying apparatus of FIG. 12; 
     FIG. 14 is an exploded perspective view of a sheet supplying apparatus according to a further embodiment of the present invention; 
     FIG. 15 is a side view, in partial section, of the sheet supplying apparatus of FIG. 14; 
     FIG. 16 is an exploded perspective view of a sheet supplying apparatus according to a further embodiment of the present invention; 
     FIG. 17 is a schematic sectional view of an image forming apparatus having a sheet supplying apparatus according to the present invention; 
     FIG. 18 is a schematic sectional view of a conventional drive controlling apparatus; and 
     FIG. 19 is an enlarged view of a drive system of the conventional drive controlling apparatus. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be explained in connection with embodiments thereof with reference to the accompanying drawings. However, dimensions, materials, configurations and relative dispositions of constructural elements in the embodiments do not limit the scope of the present invention, except for special limitations. 
     FIGS. 1A, 1B, 2A and 2B schematically show a sheet supplying apparatus using a drive controlling apparatus according to a preferred embodiment of the present invention. FIGS. 3A to 3D show an operation of the sheet supplying apparatus. 
     First of all, the construction of the sheet supplying apparatus will be described with reference to FIGS. 1A and 1B. 
     The sheet supplying apparatus comprises a semi-circular sheet supply roller 1 secured to a rotary shaft 12, and rollers 3 rotatably mounted on the rotary shaft 12 on both sides of the sheet supply roller 1. An intermediate plate 16 is supported for pivotal movement around an upstream (in a supplying direction of a sheet 2 shown by the arrow in FIG. 1A) end thereof and is biased toward the sheet supply roller 1 by means of coil springs 16b. 
     Cams 17 are secured to the rotary shaft 12 and projections 16a are secured to the intermediate plate 16 so that the cams are contacted with the projections. As the rotary shaft 12 is rotated, the cams 17 urges the projections 16a downwardly, thereby separating the sheet supply roller 1 and the rollers 3 from the sheet stack 2 rested on the intermediate plate 16 in a condition that a cut-out portion or flat portion of the sheet supply roller 1 is opposed to the sheet stack 2. In this way, the operability for removing the sheets from the intermediate plate 16 and for replenishing the sheet onto the intermediate plate can be improved. 
     In FIG. 1B, a separation pad 8 is biased toward the sheet supply roller 1 by a coil spring 8a to separate the sheets (on the intermediate plate 16) fed to the sheet supply roller 1 one by one. The sheet separated by the separation pad 8 is conveyed toward an image forming means by means of a pair of convey rollers 24. 
     With this arrangement, in the sheet supply, if the intermediate plate 16 is in the elevated position, the sheet to be supplied is pinched not only between the separation pad 8 and the rollers 3 but also between the sheet stack 2 rested on the intermediate plate 16 and the rollers 3, with the result that a load acting on the sheet becomes great, thereby increasing the load of a drive system. To avoid this, when the sheet reaches the downstream convey rollers, the intermediate plate 16 is lowered by the cams 17 to decrease the load acting on the sheet. 
     The rollers 3 disposed on both sides of the sheet supply roller 1 have diameters slightly smaller than a diameter of a cylindrical portion of the sheet supply roller 1 so that, when the flat portion of the sheet supply roller 1 is opposed to the separation pad 8, the rollers 3 urge the sheet against the separation pad 8, thereby stabilizing the separation of the sheet on the separation pad 8. In the arrangement as mentioned above, since the rollers can be rotated in a reverse direction, if the sheet is jammed between the sheet supply roller 1 and the separation pad 8, the jammed sheet can easily be removed, thereby facilitating the jam treatment. 
     As shown in FIG. 2A, each cam 17 is provided with a recess 17a. When the recesses 17a of the cams 17 are engaged by the projections 16a of the intermediate plate 16, the rotary shaft 12 and the sheet supply roller 1 are held stationary. 
     Next, a drive controlling apparatus for the sheet supply roller which is one of characteristics of the present invention will be explained. 
     In FIG. 1A, a drive controlling apparatus for controlling the transmission of a driving force to the sheet supply roller 1 is provided on one end of the rotary shaft 12. The drive controlling apparatus includes a drive gear 4 connected to a drive source such as a motor (not shown), and first and second notched gears 14, 6 which can be engaged by the drive gear 4. 
     The first notched gear 14 is attached to the rotary shaft 12 so that, when the recesses 17a of the cams 17 are engaged by the projections 16a of the intermediate plate 16, a non-toothed portion of the first notched gear is opposed to the drive gear 4. Thus, the recesses 17a and the projections 16a act as a first regulating means for regulating the first notched gear 14. Incidentally, recesses may be provided in the projections of the intermediate plate 16 and projections may be provided on the cams 17. 
     The second notched gear 6 has a key-way 5 loosely fitted on a key portion 12a of the rotary shaft 12 so that the second notched gear can be rotated within a predetermined range. Further, the second notched gear 14 is provided with a pawl portion 13 which extends through a slot 14a formed in the first notched gear 14 and is engaged or locked by a solenoid 7 disposed at an opposite side (near the sheet supply roller 1) of the first notched gear 14 with respect to the second notched gear 6. In this case, the second notched gear 6 and the solenoid 7 are so arranged that the second notched gear 6 is held stationary by the solenoid in a condition that a non-toothed portion of the second notched gear 6 is opposed to the drive gear 4. Thus, the pawl portion 13 and the solenoid 7 act as a second regulating means for regulating the second notched gear 6. 
     The reason why the solenoid 7 is disposed nearer to the sheet supply roller 1 than the first notched gear 14 is that the entire apparatus is prevented from becoming bulky in a width-wise direction of the sheet due to the installation space of the solenoid 7. Thus, so long as the entire apparatus does not become bulky, the solenoid can be disposed at any position. 
     A spring 10 serves as a rotating means and has one end secured to a fixed portion 11 of the first notched gear 14 and the other end secured to a fixed portion 9 of the second notched gear 6. An elastic force is generated in the spring in dependence upon a relative position between the first and second notched gears 14 and 6. Since the first notched gear 14 and the sheet supply roller 1 are secured to the rotary shaft 12, the sheet supply roller 1 is rotated together with the first notched gear 14. 
     Next, an operation of the drive controlling apparatus will be explained with reference to FIGS. 3A to 3D. 
     FIG. 3A shows an initial condition. In this condition, the non-toothed portion of the first notched gear 14 is aligned with the non-toothed portion of the second notched gear 6 in the axial direction, and these gears 14, 6 are not engaged by the drive gear 4. 
     In this condition, the spring (biasing means) 10 generates a given elastic force in the compression direction, but the first and second notched gears 14, 6 are held stationary in opposition to the elastic force. 
     The reason why the first notched gear 14 is held stationary is that, as shown in FIG. 1A, the first notched gears 14 is fixed to the cams 17 via the rotary shaft 12 and the recesses 17a (first regulating means) of the cams 17 are engaged by the projections 16a of the intermediate plate 16 to provide the stable condition, as shown in FIG. 2A. On the other hand, the reason why the second notched gear 6 is held stationary is that the locking pawl (locking portion) 13 of the second notched gear is locked (engaged) by a locking pawl 7a of the solenoid (second regulating means) 7 which is now disenergized. 
     From the condition shown in FIG. 3A, when the solenoid 7 is energized to release the locking condition, a condition shown in FIG. 3B in which only the second notched gear 6 is engaged by the drive gear 4 is obtained. 
     That is to say, when the locking pawl 13 is released from the locking pawl 7a of the solenoid 7, only the second notched gear 6 is rotated in the anti-clockwise direction by the elastic force of the spring 10. Namely, since the first notched gear 14 is fixed to the sheet supply roller 1 via the rotary shaft 12 and thus has the greater resistance than the second notched gear 6 and the first notched gear 14 is held stationary due to the engagement between the recesses 17a and the projections 16a, only the second notched gear 6 is rotated by the elastic force of the spring 10 to be engaged by the drive gear 4. 
     In this case, since there is the play between the key-way 5 of the second notched gear 6 and the key portion 12a of the rotary shaft 12 to permit the normal and reverse rotations of the key-way 5 relative to the key portion 12a, when the second notched gear 6 starts to be engaged by the drive gear 4, even if the teeth of these gears 6, 4 interfere with each other, the second notched gear 6 is slightly rotated in the normal or reverse direction to prevent clogging of the teeth, thereby smoothly engaging the second notched gear with the drive gear. 
     When the second notched gear 6 is further rotated to reach a first rotation limit position (where the rotation of the second notched gear 6 relative to the first notched gear 14 is inhibited), a side wall 5a of the key-way 5 abuts against the key portion 12a to rotate the first notched gear 14 (together with the second notched gear 6) until the first notched gear is engaged by the drive gear 4. In this case, the side wall 5a of the key-way 5 is so configured that, when the side wall 5a abuts against the key portion 12a, angular phases of teeth of the first and second notched gears 14, 6 are aligned with each other, with the result that, when the first notched gear 14 is engaged by the drive gear 4, there is no interference between the teeth of the gears 14 and 4. 
     With the arrangement as mentioned above, as is in the conventional case, from when the first notched gear 14 starts to rotate to when the first notched gear 14 is engaged by the drive gear 4, the biasing force of the springs 16b acting on the intermediate plate 16 may act on the cams 17 via the projections 16a as a rotational force for rotating the first notched gear 14. 
     However, this rotational force causes the rotary shaft 12 to rotate faster than the second notched gear 6. Even when the key portion 12a is separated from the side wall 5a of the key-way 5, since there is the clearance, the rotational speed of the second notched gear 6 is not increased. Further, since the rotational force is ceased before the first notched gear 14 is engaged by the drive gear 4, the key portion 12a abuts against the side wall 5a of the key-way 5 again, thereby continuing the rotation. 
     More specifically, the biasing force from the intermediate plate 16 acts on the cams 17 as the rotational force only while the rotary shaft is rotated through an angle of about θ shown in FIG. 2A. Here, since an angle through which the rotary shaft must be rotated to engage the first notched gear 14 with the drive gear 4 is selected to be greater than the angle θ, the rotational force is not transmitted to the drive gear 4 through the first notched gear 14. 
     Thus, the first notched gear 14 and accordingly the sheet supply roller 1 can start to rotate without affecting any force to the drive gear 4 and without arising any problem due to the backlash. 
     After the first notched gear 14 is smoothly engaged by the drive gear 4 in this way, the first notched gear 14 continues to be rotated by the drive gear 4. In a condition that both first and second notched gears 14 and 6 are engaged by the drive gear 4 (i.e., condition shown in FIG. 3C in which the sheet supply roller 1 starts to pick up and convey the sheet), when the gears are further rotated, after the second notched gear 6 is rotated by one revolution, it is disengaged from the drive gear 4 (condition shown in FIG. 3D). 
     However, in this condition, the first notched gear 14 is still engaged by the drive gear 4. When the first notched gear 14 tries to further rotate, the spring 10 disposed between the first notched gear 14 and the second notched gear 6 generates the elastic force again, with the result that the second notched gear 6 is further rotated by the elastic force. Thereafter, when the locking pawl 13 is caught by the locking pawl 7a of the solenoid 7, the gear is stopped and the condition shown in FIG. 3A is restored. 
     On the other hand, immediately after the first notched gear 14 is disengaged from the drive gear 4, as shown in FIG. 2B, a condition that the recesses 17a of the cams 17 are about to be engaged by the projections 16a of the intermediate plate 16. In this condition, since the intermediate plate 16 is biased toward the sheet supply roller 1 by the springs 16b, the cams 17 are rotated in the direction for engaging the recesses 17a with the projections 16a, and, at the same time, the first notched gear 14 is also rotated to return to the condition shown in FIG. 3A. That is to say, the force of the projections 16a acting on the recesses 17a immediately before the recesses 17a are engaged by the projections 16a is set so at to act as the rotational force for rotating the cams 17 in the direction for engaging the recesses 17a with the projections 16a. 
     As mentioned above, in the sheet supplying apparatus according to the illustrated embodiment, the sheet supply roller 1 can be driven smoothly and efficiently with a simple construction and the jam treatment and the replenishment of sheets can be performed easily. 
     In the above-mentioned embodiment, while an example that the key portion 12a provided on the rotary shaft 12 and the key-way 5 formed in the second notched gear 6 constitute the cooperating means was explained, in a sheet supplying apparatus shown in FIGS. 4A to 4D, a cooperating means is constituted by key portions 14a provided on a first notched gear 14 and key-ways 6a formed in a second notched gear 6, and, the key portions 14a and key-ways 6a are not positioned on the rotary shaft 12 but are spaced apart from the rotary shaft. 
     In this arrangement, in comparison with the key portion formed on the rotary shaft, since the load acting on the key portions during the rotation is reduced because of separation of the key portions from the rotary shaft, the key portions themselves can be made small-sized. 
     In the above-mentioned embodiments, while an example that the first notched gear 14 is directly secured to the rotary shaft 12 was explained, in a sheet supplying apparatus shown in FIGS. 5A to 5D, a gear 18 is secured to the rotary shaft 12 and the first notched gear 14 is meshed with the gear 18. In this way, the rotation of the drive controlling apparatus is transmitted to the sheet supply roller 1 to supply the sheet. 
     By arranging the gear 18 between the first notched gear 14 and the rotary shaft 12 in this way, the degree of freedom of layout is increased. 
     In the above-mentioned embodiments, while an example that the first and second notched gears 14, 6 have the similar non-toothed portions was explained, in a sheet supplying apparatus shown in FIG. 6, a first notched gear 14 has a toothed portion 15 provided thereon only at a rear portion thereof in a rotational direction, as shown in FIG. 6. That is to say, while the second notched gear 6 receiving the rotation starting force from the spring 10 is being rotated while engaging with the drive gear 4, since the side wall 5a of the key-way 5 abuts against the key portion 12a of the rotary shaft 12 to impart the rotational force to the sheet supply roller 1, there is no need for providing a toothed portion on the first notched gear 14 at that portion, and, thus, any toothed portion is omitted at that portion. 
     However, when the second notched gear 6 is disengaged from the drive gear 4 and is stopped by the second regulating means, since the rotational force of the first notched gear 14 is disappeared, the toothed portion is provided on a portion of the first notched gear 14 so that the first notched gear 14 is positively rotated until the non-toothed portions of the first and second notched gears are opposed to the drive gear 4. 
     Alternatively, in a sheet supplying apparatus shown in FIG. 7, a second notched gear 6 has a toothed portion provided thereon only at a front portion thereof in a rotational direction, as shown in FIG. 7. That is to say, while the second notched gear 6 receiving the rotation starting force from the spring 10 is being rotated while engaging with the drive gear 4, the side wall 5a of the key-way 5 abuts against the key portion 12a of the rotary shaft 12 to start the rotation of the first notched gear 14. The second notched gear 6 plays an role for rotating the first notched gear 14 until the first notched gear is engaged by the drive gear 4. 
     Thereafter, since the first notched gear 14 receives the rotational force directly from the drive gear 4, it is not required that the second notched gear 6 receives the rotational force from the drive gear 4. Thus, any toothed portion is omitted from the second notched gear at that portion. 
     In the above-mentioned embodiments, while an example that the spring 10 is used as the rotating means and the key-way 5 and the key portion 12a are used as the cooperating means was explained, in a sheet supplying apparatus shown in FIGS. 8 and 9A to 9D, spring 10 is used as both rotating means and cooperating means. 
     An operation of a drive controlling apparatus associated with this sheet supplying apparatus will be explained with reference to FIGS. 9A to 9D. In an initial condition shown in FIG. 9A, the first and second notched gears 14, 6 are not engaged by the drive gear 4. From this condition, when the solenoid 7 is energized, a condition (FIG. 9B) that the second notched gear 6 is engaged by the drive gear 4 is obtained. 
     However, thereafter, when the second notched gear 6 starts to rotate while engaging with the drive gear 4, a force tending to compress the spring 10 is transmitted as a rotation force for rotating the first notched gear 14 in an anti-clockwise direction relative to the second notched gear 6, thereby starting rotation of the first notched gear 14. 
     In this case, spring constant of the spring 10 and dimension of the non-toothed portion of the first notched gear 14 are selected so that the first notched gear 14 is engaged by the drive gear 4 after the rotational force transmitted from the cams 17 is absorbed by the spring 10. 
     After a condition shown in FIG. 9C is obtained, when the gears are further rotated to disengage the second notched gear 6 from the drive gear 4 again, the pawl 13 of the second notched gear is caught by the locking pawl 7a of the solenoid 7, thereby stopping the second notched gear 6 (condition shown in FIG. 9D). 
     In the above-mentioned embodiments, while an example that the semi-circular roller is used as the sheet supply roller 1 was explained, in a sheet supplying apparatus shown in FIG. 10, a cylindrical sheet supply roller 1 is used and cams are omitted. Thus, an intermediate plate is always urged against the sheet supply roller. 
     With this arrangement, until the sheet 2 is sullied completely, i.e., until a trail end of the sheet 2 leaves the sheet supply roller 1, the sheet is always pinched between the roller 1 and the separation pad 8 (FIG. 1B). In this arrangement, in a condition that the locking of the solenoid 7 is released, since the sheet supply roller 1 cannot be rotated in the sheet supplying direction except that the roller is rotated together with the first and second notched gears 14, 6, it is difficult to supply the sheet for a predetermined amount. 
     To cope with this, a one-way clutch 19 is provided between the first notched gear 14 and the rotary shaft 12 so that the sheet supply roller alone can be rotated in the sheet supplying direction (even when the first notched gear is stopped). 
     In this embodiment, a half clutch portion of the one-way clutch 19 is integrally formed with the first notched gear 14 and the other half clutch portion is mounted on an end portion of the rotary shaft 12. A one-way clutch spring 20 is associated with the half clutch portion of the rotary shaft 12 so that said half clutch portion is biased toward the first notched gear. In this way, the rotational force from the first notched gear 14 can be transmitted to the rotary shaft 12 and the rotational force from the rotary shaft 12 can be transmitted to the first notched gear 14. 
     Alternatively, a one-way clutch including a gear may provided for cooperating with the second notched gear so that the gear can be engaged by the second notched gear to transmit the rotational force. 
     When the cylindrical sheet supply roller is used in this way, since the cams and rollers can be omitted, the entire apparatus can be simplified. 
     In a sheet supplying apparatus shown in FIG. 11, the first and second notched gears 14 and 6 in the aforementioned embodiment are disposed reversely in the axial direction of the rotary shaft. That is to say, a second notched gear 6 is rotatably supported on the rotary shaft 12 between the sheet supply roller 1 and a first notched gear 14, and key portions 14a of the first notched gear 14 and key-ways 6a of the second notched gear 6 are spaced apart from the rotary shaft 12 to increase the degree of freedom around the shaft. 
     Further, a semi-circular portion is formed at the end of the rotary shaft 12 and a similar semi-circular hole is formed in the first notched gear 14. By fitting the semi-circular hole onto the semi-circular portion, the first notched gear cannot slip on the rotary shaft during the rotation. 
     In this arrangement in which the second notched gear 6 is disposed between the sheet supply roller 1 and the first notched gear, unlike to the aforementioned embodiments, since it is not required to provide any hole (in the first notched gear) through which the locking pawl 13 associated with the locking pawl 7a of the solenoid 7 protrudes toward the solenoid 7, the construction can be simplified. Further, in this embodiment, in place of such a pawl 13, a locking portion 6b cooperating with the locking pawl 7a is formed on a surface of the second notched gear 6 near the sheet supply roller 1. The locking portion 6b and the solenoid 7 constitute a second regulating means. 
     A sheet supplying apparatus shown in FIGS. 12 and 13 is similar to that shown in FIG. 11. However, in the sheet supplying apparatus shown in FIGS. 12 and 13, a shaft portion 14b into which the semi-circular portion of the rotary shaft 12 is fitted is provided on the first notched gear 14, and the second notched gear 6 is rotatably mounted around the shaft portion 14b. 
     By providing the shaft portion 14b on the first notched gear 14 in this way, the adequate fitting length between the rotary shaft 12 and the first notched gear 14 which is subjected to great load during the rotation can be ensured without increasing a width of the first notched gear 14. That is to say, a width of the entire apparatus corresponding to the length of the shaft portion 14a can be reduced without reducing the securing strength between the first notched gear 14 and the rotary shaft 12, thereby making the apparatus compact. 
     Further, since the first notched gear 14, second notched gear 6 and spring 10 can be assembled as a single unit, the assembling ability of the sheet supplying apparatus can be improved. 
     In the apparatus shown in FIGS. 12 and 13, while the cams 17 were secured to the rotary shaft 12, in a sheet supplying apparatus shown in FIGS. 14 and 15, a shaft portion 14a of a first notched gear 14 is extended up to one of the cams 17, and such a cam 17 is fixedly supported by the shaft portion 14a. 
     By directly fixing the cam 17 to the first notched gear 14, positional accuracy in a phase relation between the first notched gear 14 and the cam 17 can be improved. 
     According to the drive controlling apparatus of the present invention, during the operation of the sheet supply roller returning to its initial position after the sheet supplying operation is completed, when the first notched gear 14 is disengaged from the drive gear 4, as shown in FIG. 2B, it is necessary that the recesses 17a of the cams 17 are about to be engaged by the projections 16a of the intermediate plate 16, and, it is necessary that the first notched gear 14 is returned to the condition shown in FIG. 2A in which the recesses 17a of the cams 17 are completely engaged by the projections 16a. Accordingly, when the positional accuracy in the phase relation between the first notched gear 14 and the cam 17 is improved, the operating accuracy of the entire apparatus is also improved. 
     In a sheet supplying apparatus shown in FIG. 16, a drive controlling apparatus therefor is similar to that shown in FIGS. 12 and 13. However, in FIGS. 12 and 13, the semi-circular roller is used as the sheet supply roller; whereas, in FIG. 16, a cylindrical sheet supply roller and a one-way clutch are used (as is in FIG. 10). As a result, cams and rollers can be omitted, thereby making the entire apparatus simpler. 
     FIG. 17 schematically shows an image forming apparatus to which the sheet supplying apparatus having the drive controlling apparatus can be applied. 
     The image forming apparatus 21 comprises an optical system 22 for emitting laser light in response to image information, an image forming portion 23 including a photosensitive drum (image bearing member) 25, a first charger (corona discharger) 26, a developing device 27 and a cleaner 28, and a sheet convey portion for supplying, conveying and discharging a sheet. 
     In the image forming portion 23, a surface of the rotating photosensitive drum 25 having a photosensitive layer is uniformly charged by applying voltage to the first charger 26, and a latent image is formed on the photosensitive drum 25 by illuminating the laser light emitted from the optical system 22 in response to the image information through an exposure portion. Then, the latent image is developed by the developing device 27 as a toner image. 
     On the other hand, in synchronous with the formation of the toner image, a sheet 2 on a tray 29 is supplied by a sheet supply roller 1 forming a part of the sheet supplying apparatus driven by the drive controlling apparatus and is conveyed to the image forming portion 23 by a pair of convey rollers 24 and the like. Then, the toner image is transferred onto the sheet by applying voltage having polarity opposite to that of the toner image to a transfer roller 30. In the image forming portion 23, residual toner remaining on the photosensitive drum 25 is removed by the cleaner 28 for preparation for next image formation. 
     The sheet to which the toner image was transferred is sent to a fixing roller 31 including a heater therein, where the toner image is fixed to the sheet. Thereafter, the sheet is discharged onto a tray 33 by a pair of discharge rollers 32. 
     In the above-mentioned embodiments, while an example that each of the notched gears has the single non-toothed portion was explained, two or more non-toothed portions may be provided on each notched gear. Further, while an example that the drive controlling apparatus is used with the sheet supplying apparatus was explained, the present invention is not limited to such an example, the drive controlling apparatus can be used in synchronous with any functioning means for generating rotation of predetermined angle at a predetermined timing.