Abstract: In a resin double-helical gear formed by injection-molding, smooth meshing of teeth can be performed for rotation of the resin double-helical gear in both directions, and occurrences of thrust-direction load and noise can be prevented. Peak-side tooth flanks 7c and 7d and valley-side tooth flanks 7e and 7f of a tooth 7 in a resin double-helical gear 1 are formed such as to become farther away from peak-side tooth flanks 9c and 9d and valley-side tooth flanks 9e and 9f of a standard tooth 9 in an inward direction, the closer the peak-side tooth flanks 7c and 7d and the valley-side tooth flanks 7e and 7f are to a tooth width direction center section 3 from one tooth width direction end section 4a and another tooth width direction end section 4b. As a result, meshing escape sections g (g1 and g2) and h (h1 and h2) having dimensions in a tooth thickness direction that increase towards the tooth width direction center section 3 are formed on the peak-side tooth flank side and the valley-side tooth flank side.

Abstract: Noise can be effectively reduced without rotative power transmission accuracy being compromised. In a tooth 2 of a resin gear 1, a tooth face that is a predetermined area from a tooth crest 8 towards a tooth root 10 side serves as a tooth profile modification area 11. A tooth surface excluding the tooth profile modification area 11 serves as an involute profile area 12. The tooth profile modification area 11 includes a linear standard profile portion 14 formed by an involute curved line from the tooth crest 8 of the tooth towards the tooth root 10 side and a profile modification portion 16 in which a tooth thickness gradually and smoothly decreases from the standard profile portion 14 along a tooth width direction and the tooth thickness gradually and smoothly decreases from a tooth root end side 15 towards the tooth crest 8. In the tooth profile modification area 11, a contacting section becomes elastically deformed as a result of the resin gear coming into contact with a meshing mating gear.

Abstract: In a resin gear formed such that a first teeth section formed into a spiral and a second teeth section formed into a spiral having an opposite twist direction from the first teeth section are joined at a tooth width direction center section, reductions in quietness and smoothness caused by a decrease in contact ratio can be suppressed. A diameter D1 of a pitch-circle of a first teeth section 10 and a diameter D2 of a pitch-circle of a second teeth section are the same. A module m1 of the first teeth section 10 is an integral multiple (for example, double) of a module m2 of the second teeth section 20. Contact ratio can be enhanced by the module m2 of the second teeth section 20 being made smaller.

Abstract: Noise can be effectively reduced without rotative power transmission accuracy being compromised. In a tooth 2 of a resin gear 1, a tooth face that is a predetermined area from a tooth crest 8 towards a tooth root 10 side serves as a tooth profile modification area 11. A tooth surface excluding the tooth profile modification area 11 serves as an involute profile area 12. The tooth profile modification area 11 includes a linear standard profile portion 14 formed by an involute curved line from the tooth crest 8 of the tooth towards the tooth root 10 side and a profile modification portion 16 in which a tooth thickness gradually and smoothly decreases from the standard profile portion 14 along a tooth width direction and the tooth thickness gradually and smoothly decreases from a tooth root end side 15 towards the tooth crest 8. In the tooth profile modification area 11, a contacting section becomes elastically deformed as a result of the resin gear coming into contact with a meshing mating gear.

Abstract: In a resin double-helical gear formed by injection-molding, smooth meshing of teeth can be performed for rotation of the resin double-helical gear in both directions, and occurrences of thrust-direction load and noise can be prevented. Peak-side tooth flanks 7c and 7d and valley-side tooth flanks 7e and 7f of a tooth 7 in a resin double-helical gear 1 are formed such as to become farther away from peak-side tooth flanks 9c and 9d and valley-side tooth flanks 9e and 9f of a standard tooth 9 in an inward direction, the closer the peak-side tooth flanks 7c and 7d and the valley-side tooth flanks 7e and 7f are to a tooth width direction center section 3 from one tooth width direction end section 4a and another tooth width direction end section 4b. As a result, meshing escape sections g (g1 and g2) and h (h1 and h2) having dimensions in a tooth thickness direction that increase towards the tooth width direction center section 3 are formed on the peak-side tooth flank side and the valley-side tooth flank side.

Abstract: A plastic molded gear capable of reducing teeth knocking noises due to backlash during engagement. A protruding portion 5 for eliminating backlash is formed so as to protrude from both end portions in facewidth directions on one tooth flank 6 of each tooth 2, and the protruding portion 5 is not formed on the other tooth flank 12 of the tooth 2. If the protruding portion 5 is elastically deformed so as to absorb backlash, the protruding portion 5 has the same plane as that of the one tooth flank 6, and the other tooth flank 12 of the tooth 2 serves as a main power transmission surface. With this construction, the protruding portion 5 elastically contacts the tooth flank of a companion gear engaged with the plastic molded gear, so that the elastic deformation of the protruding portion 5 absorbs rotational energy of the companion gear during intermittent rotation.

Abstract: If only an operating button 14 is pushed, an electrically opening and closing mechanism 1 disengages a first clutch K1 while engaging a second clutch K2 to operate an electrically driving means 2 to automatically open or close a second member (e.g., a liquid crystal display panel) 4 which is rotatable with respect to a first member (e.g., a body having a plurality of keys) 3. If the operating button 14 is pushed, the second member 4 automatically rotates to an optional angular position with respect to the first member 3, and if the operating button 14 is released (if the operating button 14 is returned to the original angular position by the spring force of a second spring 23), the first clutch K1 is engaged at the optional angular position to hold the attitude of the second member 4.

Abstract: In a gear having teeth 2 on the outer periphery thereof, each of the teeth 2 has an elastically deformable overhanging portion 7 which is formed on one end face 6 in facewidth directions of a corresponding one of the teeth 2 so as to protrude from a portion near a tooth flank 8 of the corresponding one of the teeth 2 toward adjacent one of the teeth 2, and a portion of the overhanging portion 7 contacting one of teeth of a companion gear is formed so as to have the same plane as that of the tooth flank 8 when the overhanging portion 7 is pressed by the one of teeth of the companion gear to be elastically deformed.

Abstract: There is provided a plastic molded gear capable of reducing teeth knocking noises due to backlash during engagement. A protruding portion 5 for eliminating backlash is formed so as to protrude from both end portions in facewidth directions on one tooth flank 6 of each tooth 2, and the protruding portion 5 is not formed on the other tooth flank 12 of the tooth 2. If the protruding portion 5 is elastically deformed so as to absorb backlash, the protruding portion 5 has the same plane as that of the one tooth flank 6, and the other tooth flank 12 of the tooth 2 serves as a main power transmission surface. With this construction, the protruding portion 5 elastically contacts the tooth flank of a companion gear engaged with the plastic molded gear, so that the elastic deformation of the protruding portion 5 absorbs rotational energy of the companion gear during intermittent rotation.

Abstract: If only an operating button 14 is pushed, an electrically opening and closing mechanism 1 disengages a first clutch K1 while engaging a second clutch K2 to operate an electrically driving means 2 to automatically open or close a second member (e.g., a liquid crystal display panel) 4 which is rotatable with respect to a first member (e.g., a body having a plurality of keys) 3. If the operating button 14 is pushed, the second member 4 automatically rotates to an optional angular position with respect to the first member 3, and if the operating button 14 is released (if the operating button 14 is returned to the original angular position by the spring force of a second spring 23), the first clutch K1 is engaged at the optional angular position to hold the attitude of the second member 4.