The imaging principle of the electrophotographic image forming apparatus (also referred to as an electronic imaging device) is as follows: firstly, uniformly charge the photosensitive material coated surface of the photosensitive drum or the photosensitive tape; then expose the surface of the photosensitive drum or the photosensitive tape with laser beams, then the electric charges on the exposed region disappear, and the electric charges on the other regions unexposed form an electrostatic latent image; then the developing agent like carbon powder is supplied to the electrostatic latent image by a developing roller or other components, so as to develop the latent image; then the image is transferred to a print medium, and fixed by heating, thereby forming a stable image on the print medium.
In general, the electrophotographic image forming apparatus is provided with a detachable developing cartridge. Based on different design concepts, the manufacturers of electrophotographic image forming apparatus will integrate more or less processing components in the developing cartridge. For example, some manufacturers integrate a photosensitive drum, a developing device, a charging device and a cleaning device together to form an integral box, and some manufacturers integrate the photosensitive drum and the charging device together, or integrate the photosensitive drum and the developing device together to form various kinds of split boxes. Regardless of the integration modes, as long as the box is provided with any one of processing members which are required to rotate in the process of image forming, the box needs to be supplied with driving forces, so as to drive the processing components to rotate.
One of the existing driving members is designed to be a universal joint type. One end of the driving member is arranged in a cylindrical member disposed on an end part of the developing cartridge, and the other end of the driving member projects outward from the developing cartridge, so as to engage with the driving shaft of the electrophotographic image forming apparatus. When the driving member is mounted onto or detached from the electrophotographic image forming apparatus, the driving member deflects to one side relative to the axis of the cylindrical member, in order to avoid forming interference with the driving shaft. The cylindrical member may be arranged at an end of the photosensitive drum or at an end of the developing roller, and after receiving driving forces, the universal joint directly drives the photosensitive drum or the developing roller to rotate. The cylindrical member may alternatively be arranged at other positions parallel to the axis of the photosensitive drum or the developing roller, and the driving forces are transmitted to the processing components like the photosensitive drum or the developing roller through a gear assembly. This type of universal joint driving member is apt to drop out of the cylindrical member, and driving forces cannot be transmitted stably.
In order to solve the problem that this type of universal joint driving member is apt to fall off, the driving member of the exiting developing cartridge typically adopts an axially moveable connector arranged in the cylindrical member. When the connector is mounted or detached, as the driving shaft, namely the driving head, in the electrophotographic image forming apparatus abuts against the connector, the connector moves inwards to avoid interference with the driving shaft. When the developing cartridge is mounted into its position, under the action of a spring or gas pressure, the connector moves outwards and engages with the driving shaft of the electrophotographic image forming apparatus, thereby driving the driving force receiving components to rotate, such as the photosensitive drum, the developing roller, and so on. But sometimes, the axial movement of the connector is limited by other members in the electrophotographic image forming apparatus, therefore the developing cartridge cannot be detached easily. If the developing cartridge is forcibly mounted or detached, there will be a risk that the driving member cannot engage with the driving shaft of the electrophotographic image forming apparatus stably, and driving forces cannot be transmitted stably.
Chinese utility model patent No. 201120045210.4 disclosed a driving assembly, wherein, the contact head of the driving assembly is connected at a gap of the bracket body through a pivot and a rebound-reset element. When the driving assembly rotates upon receiving driving forces from the driving head of the electrophotographic image forming apparatus, the acting forces are transmitted to the bracket body through the contact head and the pivot, as a result the driving forces cannot be transmitted stably. Additionally, due to the space limitation of the gap, the pivot is usually quite thin, consequently, when the driving assembly rotates upon receiving driving forces from the driving head of the electrophotographic image forming apparatus, due to the torque generated by the rotation, the pivot is apt to be damaged. Moreover, it is not easy to install the contact head and the rebound-reset element due to the space limitation of the gap.