Transmission gear assembly structure

Abstract

To improve assemblability.SOLUTION: In an assembling structure S of a transmission gear, a gear storage section 40 for storing a transmission gear 50 is provided in a case 24 and the gear storage section 40 is formed into a recessed shape opened in a direction (an upper side or a lower side) orthogonal to an axial direction (longitudinal direction) of the transmission gear 50. A support section 45 configured to be elastically deformable in a longitudinal direction is formed on a front wall 41 of the gear storage section 40. In the support section 45, a support hole 45A is formed to rotatably support a front end 52A of a gear shaft section 52. A rear side guide groove 47 opened in the orthogonal direction (an upper side or a lower side) is formed on a rear wall 42 of the gear storage section 40. A rear end 52B of the gear shaft section 52 is inserted into a rear side guide groove 47. As a result, a direction orthogonal to the axial direction of the transmission gear 50 is defined as an assembling direction, the transmission gear 50 is assembled to the gear storage section 40 of the case 24, and the gear shaft section 52 can be supported by the single case 24.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an assembly structure for a transmission gear. [Background technology]

[0002] The dial switch mechanism described in Patent Document 1 below has a rotary knob and a second gear part meshed with a first gear part of the rotary knob, and a digital rotary switch is fixed to the second gear part. As a result, when the rotary knob is rotated, the second gear part rotates in conjunction with the rotation of the rotary knob, and the rotation of the rotary knob can be detected by the digital rotary switch. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-184966 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the dial switch mechanism has room for improvement in the following respects. Specifically, in the dial switch mechanism, the second gear unit is moved axially to assemble one end of the shaft unit to the inner case, and then the front case is moved axially to assemble it to the other end of the shaft unit. In other words, in the dial switch mechanism, the inner case and the front case sandwich the second gear unit from both axial sides. For this reason, for example, until the front case is assembled to the second gear unit, the second gear unit is in a temporary assembled state, which may make the assembled state of the second gear unit unstable. Therefore, the dial switch mechanism has room for improvement in terms of improving assembly ease.

[0005] SUMMARY OF THE INVENTION In consideration of the above, an object of the present invention is to provide an assembly structure for a transmission gear that can improve assembly efficiency. [Means for solving the problem]

[0006] One or more embodiments of the present invention are directed to an assembly structure for a transmission gear, the assembly including: a case; a dial knob rotatably mounted on the case and having a drive gear portion on its outer periphery; a transmission gear configured to include a disk-shaped gear body mounted radially outside the dial knob and having a shaft portion and a driven gear portion meshed with the drive gear portion; a rotation detection unit connected to one end of the shaft portion and detecting rotation of the transmission gear; a accommodating portion provided in the case and formed in a recessed shape with an opening that opens in a direction perpendicular to the axial direction of the shaft portion and accommodates the transmission gear through the opening; a first guide groove formed in a wall portion on one side of the accommodating portion in the axial direction, through which the shaft portion is inserted and which guides the accommodation of the transmission gear into the accommodating portion; and a support portion provided in a wall portion on the other side of the accommodating portion in the axial direction, configured to be elastically deformable in the axial direction and having a support hole that rotatably supports the shaft portion. [Effects of the Invention]

[0007] According to the transmission gear assembly structure configured as above, it is possible to improve the ease of assembly. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective view of an operating device to which a transmission gear assembly structure according to an embodiment of the present invention is applied, viewed from diagonally front right. [Figure 2] 2 is a front view of the operating device shown in FIG. 1 with a bezel removed. FIG. [Figure 3] 3 is a cross-sectional view (cross-sectional view taken along line 3-3 in FIG. 2) seen from the left side, showing the state in which the operation dial shown in FIG. 2 is assembled to the case. [Figure 4] 4 is a cross-sectional view (cross-sectional view taken along line 4-4 in FIG. 2) seen from the right side, showing the state in which the transmission gear shown in FIG. 2 is assembled to the case. [Figure 5] 3 is a cross-sectional view seen from the front side, showing a meshing state between a drive gear portion of the operation dial and a driven gear portion of the transmission gear shown in FIG. 2. FIG. [Figure 6] 3 is an exploded perspective view of the operation dial, transmission gear, and case shown in FIG. 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an operating device 10 to which a transmission gear assembly structure S according to this embodiment is applied will be described with reference to the drawings. Note that the arrows UP, FR, and RH shown as appropriate in the drawings indicate the upper side, front side, and right side of the operating device 10, respectively. In the following description, when the up-down, front-rear, and left-right directions are used, they refer to the up-down, front-rear, and left-right directions of the operating device 10 unless otherwise specified.

[0010] The operating device 10 is arranged on an instrument panel of a vehicle (automobile) or the like, and is configured as a device for operating an air conditioning system or the like of the vehicle. As shown in FIGS. 1 and 2, the operating device 10 is formed in a generally rectangular parallelepiped shape extending in the left-right direction as a whole. The operating device 10 includes a bezel 20, a housing 22, a base plate 26, a case 24, a plurality of (three in this embodiment) operating dials 30, and three transmission gears 50 for transmitting the rotation of the operating dials 30 to a rotation detection unit 28 (see FIG. 4) of the base plate 26. Each component of the operating device 10 will be described below.

[0011] (About Bezel 20) 1 and 3, the bezel 20 is formed in a generally rectangular box shape with the left-right direction as the longitudinal direction and open to the rear. Mounting pieces 20A that protrude outward in the left-right direction are integrally formed on both left-right ends of the bezel 20. The bezel 20 and the mounting pieces 20A are attached to an instrument panel or the like of a vehicle. Three exposure holes 20B are formed through the front wall of the bezel 20 to expose an operation dial 30 (described later), and the three exposure holes 20B are aligned in the left-right direction.

[0012] (Regarding Housing 22) 1 to 4, the housing 22 is formed in a generally rectangular box shape with the longitudinal direction extending in the left-right direction and open to the front. The housing 22 is accommodated in the rear of the bezel 20 and is fixed to the bezel 20 by claw engagement.

[0013] (About Case 24) The case 24 is formed in a generally rectangular plate shape with its thickness direction in the front-rear direction and its length direction in the left-right direction. A board 26 is disposed adjacent to the rear side of the case 24, and like the case 24, the board 26 is also formed in a generally rectangular plate shape with its thickness direction in the front-rear direction and its length direction in the left-right direction. The case 24, together with the board 26, is disposed so as to close the front opening of the housing 22, and is fixed to the housing 22 with screws SC.

[0014] 5 and 6, three circular case holes 24A are formed through the case 24 at positions corresponding to the exposure holes 20B of the bezel 20. A surrounding wall 24B is formed on the front surface of the case 24 radially outward of the case holes 24A to accommodate and surround a drive gear portion 34B of the dial knob 34 (described later), and the surrounding wall 24B is formed in a generally annular rib shape. The case 24 also has three gear accommodating portions 40 as accommodating portions for assembling a transmission gear 50 (described later). The gear accommodating portions 40 will be described later.

[0015] (Regarding operation dial 30) The operation dial 30 includes a dial base 32 and a dial knob 34. The dial base 32 is formed in a generally stepped cylindrical shape with its axial direction extending in the front-to-rear direction. Specifically, the diameter of the rear end of the dial base 32 is set smaller than the diameter of the remaining parts of the dial base 32. The rear end of the dial base 32 is disposed within the case hole 24A of the case 24 and adjacent to the front side of the board 26, and is fixed to the board 26 with screws (not shown).

[0016] The dial knob 34 is formed in a generally cylindrical shape with its axial direction extending in the front-to-rear direction. The dial knob 34 is fitted onto the dial base 32 and rotatably supported by the dial base 32. The rear end of the dial knob 34 is disposed close to the radially inner side of the surrounding wall 24B. A stopper portion 34A is also formed at the rear end of the dial knob 34. The stopper portion 34A protrudes radially inward from the dial knob 34, has a tip portion bent forward, and is disposed within the rear end of the dial base 32. As a result, the stopper portion 34A limits the forward movement of the dial knob 34.

[0017] A drive gear portion 34B is formed on the outer periphery of the rear end of the dial knob 34. The drive gear portion 34B is composed of a plurality of external teeth and is formed on the entire circumferential circumference of the dial knob 34 or on a portion of the circumferential surface according to the operating range of the drive gear portion 34B. The drive gear portion 34B is disposed adjacent to the radially inner side of the surrounding wall 24B of the case 24. A flange portion 34C is formed on the outer periphery of the rear end of the dial knob 34, in front of the drive gear portion 34B. The flange portion 34C is formed in a generally annular plate shape with its thickness direction in the front-to-rear direction, and is disposed adjacent to the front side of the surrounding wall 24B. The outer diameter of the flange portion 34C is set larger than the outer diameter of the surrounding wall 24B, and the outer periphery of the flange portion 34C protrudes radially outward beyond the surrounding wall 24B.

[0018] An operation knob 36 is provided at the front end of the dial knob 34 so as to be rotatable integrally therewith. The operation knob 36 is formed in a substantially cylindrical shape with its axial direction extending in the front-to-rear direction and is extrapolated onto the dial knob 34. The operation knob 36 is disposed within the exposure hole 20B of the bezel 20 and is exposed to the front from the exposure hole 20B so as to be operable. An operator grips the operation knob 36 to rotate the dial knob 34. A push knob 38 is provided inside the dial base 32 so as to be movable in the front-to-rear direction, and a knob cover 38A constituting the front end of the push knob 38 is disposed in the center of the operation knob 36. A display unit (not shown) is also provided on the knob cover 38A.

[0019] (Regarding the gear accommodating portion 40) As shown in FIGS. 2 and 4 to 6, the gear accommodating portion 40 is provided integrally with the case 24, and is configured to be paired with the surrounding wall 24B of the case 24 and the operation dial 30. Specifically, the gear accommodating portion 40 that pairs with the left operation dial 30 is disposed diagonally above and to the right of the left operation dial 30, the gear accommodating portion 40 that pairs with the central operation dial 30 in the left-right direction is disposed diagonally below and to the left of the central operation dial 30 in the left-right direction, and the gear accommodating portion 40 that pairs with the right operation dial 30 is disposed diagonally below and to the left of the right operation dial 30 (see FIG. 2). Below, the configuration of the gear accommodating portion 40 will be described using the gear accommodating portion 40 that pairs with the left operation dial 30.

[0020] The gear accommodating portion 40 is formed in the upper portion of the case 24 and is disposed adjacent to the radially outer side of the surrounding wall 24B. The gear accommodating portion 40 is formed in a generally flat shape with a thickness direction in the front-to-rear direction and is formed in a concave shape with an opening 40A that opens upward. Specifically, the gear accommodating portion 40 has a front wall 41 and a rear wall 42 that are disposed opposite each other in the front-to-rear direction and whose thickness direction is the front-to-rear direction, and an outer peripheral wall 43 that connects the outer peripheral portions of the front wall 41 and the rear wall 42, and is protruded forward relative to the case 24. That is, the rear wall 42 is formed by the case 24, the outer peripheral wall 43 protrudes forward from the case 24, and the front wall 41 is disposed one step higher forward relative to the case 24. The opening 40A of the gear accommodating portion 40 is disposed adjacent to the lower side of the upper wall of the housing 22 so as to be blocked by the upper wall (see FIG. 4).

[0021] The outer peripheral wall 43 is formed in a generally U-shape that opens upward when viewed from the front. Specifically, the outer peripheral wall 43 includes a pair of left and right vertical walls 43A (see FIG. 5) that extend linearly in the up-down direction and a generally semicircular curved wall 43B (see FIG. 5) that opens upward, and the curved wall 43B connects the lower ends of the pair of vertical walls 43A. A portion of the curved wall 43B of the gear accommodating portion 40 and a portion of the surrounding wall 24B overlap when viewed from the front. A communication portion 44 (see FIG. 5) that communicates the interior of the gear accommodating portion 40 with the interior of the surrounding wall 24B is formed in the case 24 at this overlapping portion. The communication portion 44 penetrates radially through the curved wall 43B and the surrounding wall 24B. As a result, the drive gear portion 34B of the dial knob 34 is exposed to the gear accommodating portion 40 through the communicating portion 44. The front surface of the gear accommodating portion 40 is disposed flush with the front end surface of the surrounding wall 24B (see FIG. 6). As a result, a portion of the flange portion 34C of the dial knob 34 covers the gear accommodating portion 40 from the front side at the communicating portion 44.

[0022] A slit 41A is formed through the front wall 41 of the gear accommodating section 40 at approximately its center. The slit 41A is formed in a generally inverted U-shape that opens downward in a front view and extends vertically. The inner portion of the slit 41A in the front wall 41 is configured as a support portion 45 for rotatably supporting a gear shaft portion 52 of a transmission gear 50 (described later). Specifically, the support portion 45 is formed in a generally rectangular plate shape with its longitudinal direction extending vertically, and its lower end is connected to the front wall 41. Therefore, the support portion 45 is configured as a cantilever beam with its lower end as a support point and is elastically deformable in the front-rear direction. A circular support hole 45A is formed through the upper end of the support portion 45, and the central axis of the support hole 45A coincides with the central axis of the curved wall 43B of the outer peripheral wall 43.

[0023] A front guide groove 46 serving as a second guide groove is formed penetrating the front wall 41 of the gear accommodating portion 40 in the center in the left-right direction above the support portion 45. The front guide groove 46 extends in the vertical direction, with the upper end of the front guide groove 46 open upward and the lower end of the front guide groove 46 communicating with the slit 41A. The width dimension (left-right dimension) of the front guide groove 46 is approximately the same as the diameter dimension of the support hole 45A.

[0024] A rear guide groove 47 serving as a first guide groove is formed through the rear wall 42 of the gear accommodating portion 40 in the center in the left-right direction. The rear guide groove 47 extends in the up-down direction and is arranged opposite the front guide groove 46 in the front-rear direction. The upper end of the rear guide groove 47 is open upward, and the lower end of the rear guide groove 47 is arranged opposite the support hole 45A in the front-rear direction. The width dimension (left-right dimension) of the rear guide groove 47 is approximately the same as the width dimension of the front guide groove 46.

[0025] The gear accommodating portion 40 paired with the operation dial 30 at the center in the left-right direction is disposed diagonally below and to the left of the operation dial 30, and is formed in a concave shape that is vertically inverted from the gear accommodating portion 40 paired with the left-side operation dial 30, and is open to the bottom. A communication portion 44 radially penetrates the curved wall 43B and a portion of the surrounding wall 24B (see FIG. 6). The gear accommodating portion 40 paired with the right-side surrounding wall 24B is disposed diagonally below and to the left of the surrounding wall 24B, and is configured similarly to the surrounding wall 24B at the center in the left-right direction.

[0026] (Transmission gear 50) The transmission gear 50 includes a gear body 51 and a gear shaft portion 52 serving as a shaft portion. The gear body 51 is formed in a generally circular plate shape with its thickness extending in the front-to-rear direction. A driven gear portion 51A made up of a plurality of external teeth is formed on the outer periphery of the gear body 51, and the driven gear portion 51A is formed around the entire circumferential direction of the gear body 51. A base portion 51B is formed in the center of the front surface of the gear body 51, and is raised one step forward.

[0027] The gear shaft portion 52 is formed in a generally cylindrical shape with its axis extending in the front-rear direction, and protrudes from the center of the gear body 51 on both sides in the front-rear direction. The axial length of a front end portion 52A of the gear shaft portion 52 (the portion protruding forward from the gear body 51) is set to be significantly shorter than the axial length of a rear end portion 52B of the gear shaft portion 52 (the portion protruding rearward from the gear body 51). Specifically, the axial length of the front end portion 52A of the gear shaft portion 52 is set to be approximately half the plate thickness of the support portion 45 (see FIG. 4). The diameter of the gear shaft portion 52 is slightly smaller than the diameter of the support hole 45A.

[0028] The transmission gear 50 is accommodated in the gear accommodating portion 40 through the opening 40A of the gear accommodating portion 40 of the case 24 and is rotatably assembled to the case 24. That is, the transmission gear 50, whose axis is parallel to the axis of the operation dial 30, is assembled to the case 24 in an assembly direction perpendicular to the axial direction of the transmission gear 50. When the transmission gear 50 is accommodated in the gear accommodating portion 40, the front end 52A of the gear shaft portion 52 is rotatably inserted into the support hole 45A of the support portion 45 and is rotatably supported by the support portion 45. In this state, the base portion 51B of the transmission gear 50 is disposed adjacent to the rear side of the support portion 45, and the rear end 52B of the gear shaft portion 52 is disposed in the rear guide groove 47 and is rotatably supported by the end of the rear guide groove 47. Furthermore, in this state, the driven gear portion 51A of the transmission gear 50 is disposed in the communication portion 44 and is meshed with the drive gear portion 34B of the operation dial 30.

[0029] The rear end 52B of the gear shaft 52 protrudes rearward from the case 24 and is connected to the rotation detection unit 28 mounted on the rear surface of the substrate 26 (see FIG. 4). A hole is formed in the substrate 26, through which the rear end 52B of the gear shaft 52 is inserted. The rotation detection unit 28 is configured as, for example, a rotary variable resistor, and is electrically connected to a control unit (not shown) of the vehicle via the substrate 26. As a result, when the operation dial 30 is rotated, the transmission gear 50 rotates in conjunction with the rotation of the operation dial 30, and the rotation detection unit 28 outputs an output signal corresponding to the rotation of the transmission gear 50 to the control unit, so that the control unit detects the rotation of the operation dial 30.

[0030] Furthermore, sliding ribs 51C are integrally formed on the outer peripheral portions of the front and rear surfaces of the gear body 51. The sliding rib 51C is formed in a ring shape extending in the circumferential direction of the gear body 51, and is formed in a generally semicircular shape that convex outward in the front-to-rear direction in a cross section viewed from the longitudinal direction. The sliding ribs 51C are disposed adjacent to the inner sides of the front wall 41 and rear wall 42 of the gear accommodating portion 40 in the front-to-rear direction. This limits the relative movement of the transmission gear 50 with respect to the case 24 in the front-to-rear direction. Note that the gear body 51 may be supported by the base 51B of the transmission gear 50, and the sliding rib 51C may not be provided.

[0031] Further, an inclined surface 52C is formed on the front end surface of the gear shaft portion 52, and the inclined surface 52C is inclined rearward as it moves radially outward of the gear shaft portion 52 when viewed in the radial direction of the transmission gear 50. In the example shown in Figures 4 and 6, the inclined surface 52C is formed on the lower end of the front end surface of the gear shaft portion 52, and is inclined rearward as it moves downward when viewed in the left-right direction. Note that the inclined surface 52C may be provided around the entire outer periphery of the front end of the gear shaft portion 52, or may be provided on the tip side of the support portion 45.

[0032] (Action and effect) Next, the procedure for assembling the transmission gear 50 into the case 24 will be described, and the operation and effect of the operating device 10 of this embodiment will be described.

[0033] Below, the procedure for assembling the transmission gear 50 into the case 24 will be described using the transmission gear 50 that forms a pair with the left operating dial 30. When assembling the transmission gear 50 into the case 24, the gear body 51 of the transmission gear 50 is placed above the opening 40A of the gear accommodating section 40, and the orientation of the transmission gear 50 is set so that the inclined surface 52C of the transmission gear 50 is positioned on the opening 40A side (i.e., below) with respect to the central axis of the transmission gear 50.

[0034] In this state, the transmission gear 50 is slid downward to insert the gear body 51 into the gear accommodating portion 40. The transmission gear 50 is slid further downward to insert the front end 52A of the gear shaft portion 52 into the front guide groove 46 of the gear accommodating portion 40, and the rear end 52B of the gear shaft portion 52 into the rear guide groove 47. As a result, the gear shaft portion 52 moves downward while being guided by the front guide groove 46 and the rear guide groove 47. When the front end 52A of the gear shaft portion 52 reaches a position where it abuts against the upper end of the support portion 45, the inclined surface 52C of the gear shaft portion 52 slips behind the upper end of the support portion 45. When the transmission gear 50 is slid further downward, the inclined surface 52C of the gear shaft portion 52 presses the support portion 45 forward, causing it to elastically deform forward with its lower end serving as a support point. Then, when the gear shaft portion 52 reaches a position corresponding to the support hole 45A, the support portion 45 returns to the state before elastic deformation, and the gear shaft portion 52 is inserted into the support hole 45A. At this time, the rear end portion 52B of the gear shaft portion 52 is positioned at the lower end portion of the rear guide groove 47 and is supported by the inner circumferential surface of the rear guide groove 47. In this way, the transmission gear 50 is assembled to the case 24 in a direction perpendicular to its axial direction, and is rotatably supported by the case 24.

[0035] Then, the rear end 52B of the gear shaft portion 52 of the transmission gear 50 is connected to the rotation detection portion 28 of the board 26, and the case 24 is fixed to the housing 22 together with the board 26. After the transmission gear 50 is assembled to the case 24, the operation dial 30 is assembled to the board 26, whereby the drive gear portion 34B of the dial knob 34 and the driven gear portion 51A of the transmission gear 50 are engaged with each other. This connects the operation dial 30 and the transmission gear 50, and the rotation detection portion 28 can detect the rotation operation of the operation dial 30.

[0036] As described above, in the transmission gear assembly structure S, the gear accommodating portion 40 that accommodates the transmission gear 50 is provided in the case 24, and the gear accommodating portion 40 is formed in a concave shape that is open in a direction (upper or lower) perpendicular to the axial direction (front-rear direction) of the transmission gear 50. A support portion 45 that is configured to be elastically deformable in the front-rear direction is formed in the front wall 41 of the gear accommodating portion 40, and a support hole 45A that rotatably supports the front end portion 52A of the gear shaft portion 52 is formed in the support portion 45. Furthermore, a rear guide groove 47 that is open in the perpendicular direction (upper or lower) is formed in the rear wall 42 of the gear accommodating portion 40, and the rear end portion 52B of the gear shaft portion 52 is inserted into the rear guide groove 47. As a result, as described above, the transmission gear 50 can be assembled into the gear accommodating portion 40 of the case 24 with the direction perpendicular to the axial direction of the transmission gear 50 as the assembly direction, and the front end portion 52A and the rear end portion 52B of the gear shaft portion 52 can be supported by the single case 24. This improves the ease of assembly of the transmission gear 50.

[0037] The gear accommodating portion 40 is formed in a flat shape with its thickness direction aligned with the axial direction of the transmission gear 50 and in a concave shape that is open in a direction perpendicular to the axial direction of the transmission gear 50. Specifically, the gear accommodating portion 40 has a front wall 41 and a rear wall 42 with its thickness direction aligned with the axial direction of the transmission gear 50, and the gear main body 51 is accommodated in the gear accommodating portion 40 while being sandwiched between the front wall 41 and the rear wall 42 in the front-to-rear direction. In other words, the front wall 41 and the rear wall 42 of the gear accommodating portion 40 restrict the axial movement of the transmission gear 50. This makes it possible to rotatably assemble the transmission gear 50 to the case 24 while suppressing an increase in the size of the gear accommodating portion 40 in the axial direction of the transmission gear 50, compared to a configuration in which, for example, an engaging portion that engages with the transmission gear 50 by a claw engagement is formed in the case 24 and the axial movement of the transmission gear 50 is restricted by the engaging portion.

[0038] Furthermore, as described above, the transmission gear 50 is assembled into the gear accommodating portion 40 of the case 24 with the assembly direction being perpendicular to the axial direction of the transmission gear 50. This allows the space in front of the gear accommodating portion 40 to be effectively utilized. In other words, if the transmission gear 50 were assembled from the front along the axial direction, it would be necessary to ensure space in front of the gear accommodating portion 40 for assembling the transmission gear 50. In contrast, by assembling the transmission gear 50 from the direction perpendicular to the axial direction, it is no longer necessary to ensure space in front of the gear accommodating portion 40 for assembling the transmission gear 50. This allows the space in front of the gear accommodating portion 40 to be effectively utilized to arrange other structures, etc.

[0039] As described above, the gear accommodating portion 40 is formed in a recessed shape with the opening 40A that opens in a direction perpendicular to the axial direction of the transmission gear 50. Therefore, the gear accommodating portion 40 can be configured to cover the gear body 51 of the transmission gear 50 from the radially outer side and both axial sides. This, for example, can improve the protection performance of the transmission gear 50. Also, for example, it can prevent foreign matter from adhering to the driven gear portion 51A. Therefore, it is possible to maintain a good meshing state between the transmission gear 50 and the operating dial 30.

[0040] Additionally, a communication section 44 is formed in the case 24 to communicate between the interior of the gear accommodating section 40 and the interior of the surrounding wall 24B, and the driven gear section 51A of the transmission gear 50 and the drive gear section 34B of the dial knob 34 are meshed at the communication section 44. This allows the driven gear section 51A of the transmission gear 50 to be meshed with the drive gear section 34B of the dial knob 34 even if the gear accommodating section 40 is formed in a recessed shape that is open in a direction perpendicular to the axial direction.

[0041] Additionally, the dial knob 34 is formed with a flange portion 34C in front of the drive gear portion 34B, and the flange portion 34C covers the gear accommodating portion 40 from the front at the communicating portion 44. This makes it possible for the flange portion 34C to prevent foreign matter from entering the gear accommodating portion 40 through the communicating portion 44. This makes it possible to maintain an even better meshing state between the transmission gear 50 and the operating dial 30.

[0042] Furthermore, an inclined surface 52C is formed on the front end surface of the gear shaft portion 52 of the transmission gear 50. When viewed in the radial direction of the gear shaft portion 52, the inclined surface 52C is inclined rearward as it extends radially outward from the gear shaft portion 52. This allows the inclined surface 52C to easily slip behind the support portion 45 when inserting and assembling the transmission gear 50 into the gear accommodating portion 40. The inclined surface 52C presses the support portion 45 forward, causing it to elastically deform. That is, the inclined surface 52C prevents the front end of the gear shaft portion 52 from getting caught on the support portion 45, allowing the inclined surface 52C to effectively elastically deform the support portion 45. This effectively improves the ease of assembling the transmission gear 50 into the case 24.

[0043] Furthermore, the axial length of the front end 52A of the gear shaft portion 52 is set to be equal to or less than the plate thickness of the support portion 45. As a result, when the support portion 45 of the transmission gear 50 is assembled, the gear shaft portion 52 does not protrude forward beyond the support portion 45. Therefore, the space on the front side of the gear accommodating portion 40 can be effectively utilized.

[0044] Furthermore, the case 24 is housed within the housing 22, and the opening 40A of the gear accommodating portion 40 is covered by the peripheral wall of the housing 22. This allows the housing 22 to effectively prevent foreign matter from entering the gear accommodating portion 40 through the opening 40A. This allows the meshing state between the transmission gear 50 and the operating dial 30 to be maintained even better.

[0045] In the present embodiment, the slits 41A are formed through the front wall 41 of the gear accommodating portion 40 to allow the support portion 45 to be elastically deformable in the front-rear direction, but the configuration for elastically deforming the support portion 45 is not limited to this. For example, the support portion 45 may be configured to be elastically deformable by providing a weak portion in the front wall 41 without forming the slits 41A through the front wall 41.

[0046] Similarly, the front guide groove 46 and the support hole 45A may not be penetrated, but may be provided with a weak portion in the front wall 41, thereby making the support portion 45 elastically deformable. This makes it possible to completely cover the front side. [Explanation of symbols]

[0047] 22 Housing 24 cases 24B Enclosure Wall 28 Rotation detection unit 34 Dial knob 34C flange 40 Gear housing (housing) 40A opening 41A Slit 44 Communication part 45A support hole 46 Front guide groove (second guide groove) 47 Rear guide groove (first guide groove) 51 Gear body 51A Driven gear section 52 Gear shaft (shaft) 52C Slope S Transmission gear assembly structure

Claims

1. Case and a dial knob rotatably provided on the case and having a drive gear portion on its outer periphery; a transmission gear provided radially outward of the dial knob and including a disk-shaped gear body having a shaft portion and a driven gear portion meshed with the drive gear portion; a rotation detection unit connected to one end of the shaft unit and configured to detect rotation of the transmission gear; a receiving portion provided in the case, the receiving portion having a recessed shape with an opening that opens in a direction perpendicular to the axial direction of the shaft portion, the receiving portion receiving the transmission gear through the opening; a first guide groove formed in a wall portion on one side in the axial direction of the accommodation portion, the first guide groove having the shaft portion inserted therethrough and guiding accommodation of the transmission gear in the accommodation portion; a support portion provided on a wall portion on the other side in the axial direction of the accommodation portion, configured to be elastically deformable in the axial direction, and having a support hole that rotatably supports the shaft portion; A transmission gear assembly structure comprising:

2. a second guide groove is formed in a wall portion of the accommodation portion on the other side in the axial direction, 2. The transmission gear assembly structure according to claim 1, wherein when the transmission gear is accommodated in the accommodation portion, the shaft portion is inserted into the second guide groove, and the shaft portion is guided to the support portion by the second guide groove.

3. 3. The transmission gear assembly structure according to claim 2, wherein a slit is formed through the wall portion on the other axial side of the accommodating portion to separate the wall portion from the support portion, and the second guide groove is connected to the slit.

4. 4. The transmission gear assembly structure according to claim 3, wherein an inclined surface inclined toward one side in the axial direction is formed on an end face of the shaft portion supported by the support portion.

5. The case is provided with a surrounding wall that surrounds the drive gear portion from the radially outer side, A portion of the surrounding wall and a portion of the storage portion overlap each other when viewed from the axial direction, 5. The transmission gear assembly structure according to claim 4, wherein the case has a communication portion formed at the overlapping portion of the surrounding wall and the accommodating portion, which communicates the interior of the surrounding wall with the interior of the accommodating portion.

6. 6. The transmission gear assembly structure according to claim 5, wherein a flange portion that protrudes radially outward is formed on the outer periphery of the dial knob, and the flange portion covers the surrounding wall from the other side in the axial direction.

7. 7. The transmission gear assembly structure according to claim 1, wherein the case is accommodated in a housing, and the opening is covered by the housing.

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