Planetary gear mechanism

Abstract

To provide a planetary gear mechanism having a reasonable structure which is excellent in attachability.SOLUTION: A planetary gear mechanism P is provided at a linear motion device including: a housing 4; a drive part M; and a rod 3 which is formed with a screw part 10 to which a driving force is transmitted from the drive part M and which reciprocates along an axis X with rotation restricted. The planetary gear mechanism P includes: a first carrier K1 which threadedly engages with a nut 2 while contacting with an inner member 11a of a bearing part 11; a second carrier K2 which is attached to the first carrier K1 and holds a planetary gear P2; and a removal prevention ring 14 which is attached to an inner surface of the housing 4 so as to fix an outer member 11b of a bearing part 11 to the housing 4, so that the nut 2 which threadedly engages with the screw part 10, the bearing part 11 which rotatably supports the nut 2 on the housing 4, and a carrier K which holds the planetary gear P2 are fixedly inserted into the housing 4 in a state that the bearing part 11 is located at the depth side.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a planetary gear mechanism that transmits the rotational drive of a drive unit to a rod that reciprocates in a state where rotation is restricted in a linear motion device. [Background technology]

[0002] Conventionally, such a planetary gear mechanism is disclosed, for example, in Patent Document 1 (see

[0006] ,

[0024] and FIG. 2).

[0003] This linear motion mechanism includes a housing 1a connected to the suspension mechanism, an electric motor housed inside this housing 1a, a planetary gear mechanism that reduces the output of the electric motor, and a rod 2 that is the object to be driven. A carrier that holds a planetary gear 32 of the planetary gear mechanism also serves as a nut member 36 that screws onto the rod 2. The rod 2 is equipped with a magnet block 50 for measuring displacement, and by guiding this magnet block 50 inside the housing 1a, the rod 2 moves back and forth while its rotation is restricted.

[0004] The planetary gear mechanism is fixed to the housing 1a as follows: The innermost sun gear 31 is integrally molded with the hollow rotary shaft 20 of the electric motor. The outermost ring gear 33 is non-rotatably supported by a cylindrical holder 34, which is in turn non-rotatably supported on the inner surface of the housing 1a. At this time, a snap ring 14 is held in an annular groove 10a formed on the inner surface of the housing 1a, and one position of the ring gear 33 is determined.

[0005] Between the sun gear 31 and the ring gear 33, a carrier is disposed, which is formed integrally with a nut member 36 and which supports three planetary gears 32. A bearing 37 is provided between the outer surface of the end of the carrier and the inner surface of the holder 34. The inner member 37a of the bearing 37 is fixed in position by a spacer 37c attached to the end face of the carrier and a groove in the outer surface of the carrier. The outer member 37b of the bearing 37 is fixed in position by a step portion of the holder 34 and a connecting cover 11 attached so as to cover the end opening of the housing 1a. As a result, the outer member 37b of the bearing 37, the holder 34, and the ring gear 33 are firmly clamped between the snap ring 14 and the connecting cover 11, and are held non-rotatable relative to the housing 1a. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-60393 Summary of the Invention [Problem to be solved by the invention]

[0007] In the conventional planetary gear mechanism described above, the carrier and the nut member 36 are integrated into one structure. Therefore, in order to improve the thrust and durability of the linear motion mechanism, it was necessary to change the trapezoidal thread formed on the nut member 36 to be threadedly engaged with the rod 2 to a material with high wear resistance, such as brass. If the entire carrier were made of brass, the weight and cost of the linear motion mechanism would increase.

[0008] Furthermore, in this planetary gear mechanism, a holder 34 is used to fix the ring gear 33 to the housing 1a. This is presumably because the holder 34 is provided to simultaneously hold the large-diameter ring gear 33 and the small-diameter bearing 37 in order to fix the bearing 37, which has a smaller diameter than the ring gear 33. However, providing such a holder 34 increases the number of parts and the number of assembly steps, resulting in increased costs.

[0009] If the holder 34 is omitted, the difference in outer diameter between the ring gear 33 and the bearing 37 is too great, making it particularly difficult to form a mounting portion for the bearing 37. That is, the inner member 37a of the bearing 37 is fixed to the carrier while the outer member 37b of the bearing 37 is fixed to the housing 1a. In this case, the large-diameter ring gear 33 and the small-diameter bearing 37 are close to each other along the longitudinal direction of the rod 2, so it is necessary to configure the inner surface of the housing 1a so that it tapers significantly from the ring gear 33 toward the bearing 37. Furthermore, in this case, when fixing both ends of the outer member 37b of the bearing 37 in position, the presence of the large-diameter ring gear 33 near one end makes fixing that end extremely difficult.

[0010] As described above, conventional planetary gear mechanisms have various problems to be solved in order to simplify the mechanism itself or to make the mechanism easier to install, and there has been a demand for a planetary gear mechanism with a rational configuration. [Means for solving the problem]

[0011] (Features and configuration) The planetary gear mechanism according to the present invention has the following characteristic configuration: Housing and a drive unit provided in the housing; a rod having a threaded portion to which a driving force is transmitted from an output gear of the drive unit, the rod reciprocating along an axis while being prevented from rotating relative to the housing, a nut that is screwed onto the threaded portion; a bearing portion that rotatably supports the nut on the housing; a carrier for holding a planetary gear, and a carrier for holding a planetary gear, the carrier being inserted and fixed into the housing with the bearing portion facing the rear side; a first carrier that abuts against an inner member of the bearing portion and is threadedly engaged with the nut; a second carrier attached to the first carrier and holding the planetary gear; a retaining ring attached to an inner surface of the housing to fix the outer member of the bearing portion to the housing; Equipped with The first carrier has a fixing screw portion that meshes with the nut, and the bearing portion is configured so that the inner member of the bearing portion is clamped between a bulge protruding from the surface of the nut and the end face of the first carrier.

[0012] (effect) When a planetary gear mechanism, which is made up of multiple parts such as a carrier that holds the planetary gear, bearings, and nuts, is inserted and fixed deep inside a housing, the assembly order of the components becomes complicated.

[0013] Therefore, in this configuration, by dividing the carrier that holds the planetary gears into a first carrier and a second carrier, the bearings and retaining rings that are located at the rear of these carriers can be installed before the second carrier is installed. The bearings are fixed by fastening the retaining ring to the inner surface of the housing, so the sizes of the bearings and retaining rings are not restricted by the size of the carrier. This makes it possible to reduce the size of the bearings, allowing for a compact planetary gear mechanism.

[0014] In addition, since the nut and carrier are separate components in this configuration, they can be constructed using appropriate materials, resulting in a lighter, lower-cost planetary gear mechanism compared to conventional systems where the entire mechanism is constructed from brass. Furthermore, with this configuration, the fixing of the bearing portion and the first carrier to the nut can be simplified, and the efficiency of these assembly operations can be improved.

[0015] In the planetary gear mechanism according to the present invention, the outer diameter of the second carrier can be configured to be larger than the inner diameter of the retaining ring.

[0016] (effect) As a result of the present configuration in which the first carrier and the second carrier are separate, the bearings can be installed before the second carrier is installed. Therefore, as in this configuration, the outer diameter of the second carrier can be set larger than the inner diameter of the retaining ring, increasing the flexibility in selecting the dimensions of the second carrier. This simplifies the installation procedure for the bearings and improves the efficiency of the assembly process.

[0017] Furthermore, since the size of the bearing portion and the size of the second carrier can be set separately, the degree of freedom in setting the components of the planetary gear mechanism is increased.

[0018]

[0019]

[0020] In the planetary gear mechanism according to the present invention, the first carrier and the second carrier are fitted together by a first fitting portion and a second fitting portion that are connected in two stages along the direction of the axis, and it is advantageous if the second fitting portion is a spline-shaped fitting portion.

[0021] (effect) With this configuration in which the first carrier and the second carrier are fitted together along the axial direction, the second carrier can be attached very easily.

[0022] Furthermore, by configuring the mating portion in two stages, a first mating portion and a second mating portion, and making one of the second mating portions spline-shaped, the first carrier and the second carrier can rotate stably as a single unit, and the rotation of the planetary gear can be reliably transmitted to the nut.

[0023] Furthermore, before the second carrier is fitted to the first carrier, the first carrier is threaded onto the nut with the splined portion of the first carrier exposed. At this time, the splined portion can serve as the input portion of the fastening tool, making the first carrier easier to fasten.

[0024] In the planetary gear mechanism according to the present invention, an annular spacer that prevents the outer member of the bearing portion from coming into contact with the retaining ring can be provided, and the spacer can be fixed to the inner surface of the housing.

[0025] (effect) With this configuration, the dimensions of the spacer that prevents the outer member of the bearing from slipping out can be set regardless of the dimensions of the second carrier. This increases the degree of freedom in designing the part that secures the bearing. Furthermore, when using a spacer, the spacer can be installed before attaching the second carrier, which makes the installation of the bearing more efficient. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is an explanatory diagram showing an example of use of a displacement detection device according to an embodiment of the present invention; [Figure 2] An explanatory diagram showing the configuration of the drive unit [Figure 3] An exploded perspective view showing the configuration of the drive unit [Figure 4] 1 is a cross-sectional side view showing the configuration of a displacement detection device; [Figure 5] FIG. 1 is a perspective view showing the configuration of a main part of a displacement detection device; [Figure 6] A longitudinal cross-sectional view showing the configuration of the main part of the displacement detection device. [Figure 7] FIG. 1 is a perspective view showing the configuration of a control unit. [Figure 8] FIG. 1 is a perspective view showing the configuration of a spacer substrate; [Figure 9] FIG. 1 is a perspective view showing a fitting structure of a first substrate and a second substrate; [Figure 10] An explanatory diagram showing the grounding structure of the control unit [Figure 11] An explanatory diagram showing the heat dissipation structure of the control unit [Figure 12] An explanatory diagram showing the sealing structure of the control unit DETAILED DESCRIPTION OF THE INVENTION

[0027] (overview) The displacement detection device S according to the present invention can be used, for example, in a linear motion mechanism provided in a rear wheel steering device of a vehicle. In the linear motion mechanism, for example, a cylindrical nut 2 is rotated by an electric motor 1, which is a drive unit M, and a rod 3 threadedly inserted into the nut 2 is moved back and forth. A sliding surface that abuts against the inner surface of a housing 4 of the linear motion mechanism is formed on a part of the rod 3, and the rod 3 is configured to move back and forth without rotating.

[0028] 1 and 2 show the configuration of the linear motion mechanism according to this embodiment. The linear motion mechanism includes a control unit C provided on the left side of FIG. 1 and a drive unit M provided on the right side. The control unit C has a linear motion sensor 25 that measures the displacement state of the rod 3, and calculates the position of the rod 3 based on a signal from this linear motion sensor 25. Based on the calculation result, the control unit C supplies a drive signal to the drive unit M to move the rod 3 to a desired position.

[0029] (Drive unit) 2 and 3, the drive unit M of this embodiment includes a stator 5 having an axis X along the movement direction of the linear motion mechanism, and a cylindrical rotor 6 that rotates inside the stator 5. A rod 3 is inserted inside the cylindrical rotor 6. The rotor 6 is supported on both sides of the housing 4 by rotor bearings 7 on both outer sides along the axis X, sandwiching the opposing position of the stator 5.

[0030] (planetary gear mechanism) A planetary gear mechanism P is connected to one end of the rotor 6. Specifically, a sun gear P1 is formed on the outer surface of the end of the rotor 6. Three planetary gears P2 mesh with the sun gear P1, and a ring gear P3 fixed to the housing 4 meshes with the outer surface of the planetary gear P2.

[0031] The carrier K of the planetary gear P2 is screwed and fixed to the outer periphery of the nut 2 which is screwed onto the rod 3. The carrier K has a first carrier K1 which is fixed to the outer surface of the nut 2, and a second carrier K2 which is fitted and fixed to the outside of the first carrier K1. Three shaft members 8 which respectively support the three planetary gears P2 are fixed to the second carrier K2.

[0032] The nut 2 is cylindrical, and has a female trapezoidal thread 9a formed on its inner surface as an output gear 9 for the drive unit M. On the other hand, the rod 3 has a male trapezoidal thread 10a formed on its outer surface as a threaded portion 10. The nut 2 is made of brass to provide wear resistance. The rod 3 moves back and forth without rotating relative to the housing 4 by abutting a sliding contact member 21 (described below) against the inner surface of the housing 4. A bearing portion 11 using a thrust bearing is fitted onto the outer surface of the nut 2, and this bearing portion 11 is fitted inside the inner surface of the housing 4.

[0033] The first carrier K1 is fitted onto one end of the nut 2 and screwed and fixed via a fixing screw portion 12. A radially protruding bulge 2a is formed on the other end of the nut 2, and the inner member 11a of the bearing portion 11 is sandwiched between the bulge 2a and the end face of the first carrier K1 along the axis X. This configuration simplifies the fixing of the bearing portion 11 and the first carrier K1 to the nut 2, thereby improving the efficiency of the assembly work.

[0034] The second carrier K2, which holds the planetary gear P2, is fitted and fixed to the outside of the first carrier K1. This fitting and fixing is performed using two types of fitting portions. One is a cylindrical first fitting portion Ka formed on the far side in the fitting direction along the axis X when viewed from the second carrier K2 side. This is formed by a cylindrical fitting outer surface formed on the outer surface of the first carrier K1 and a cylindrical fitting inner surface formed on the inner surface of the second carrier K2. The other is a spline-shaped second fitting portion Kb adjacent to the first fitting portion Ka and positioned on the near side in the fitting direction when viewed from the second carrier K2 side.

[0035] The second fitting portion Kb is configured, for example, in a star-shaped cross section perpendicular to the axis X. This prevents the first carrier K1 and the second carrier K2 from rotating relative to each other, making it possible to configure a durable carrier K. Furthermore, when threading the first carrier K1 into the nut 2, the second fitting portion Kb can be used as an engagement portion for a fastening tool. The first carrier K1 and the second carrier K2 are formed of steel instead of the conventional brass, thereby achieving weight reduction and cost reduction.

[0036] In this embodiment, the housing 4 has a particularly narrow shape, and the bearing portion 11 needs to be located deep inside the carrier K. Therefore, the installation procedure is as follows: the bearing portion 11 is attached to the nut 2, the bearing portion 11 is clamped by the first carrier K1, and then these are fixed to the housing 4. The second carrier K2 is then attached to the first carrier K1.

[0037] The bearing 11 is fixed using an annular spacer 13 that abuts against the outer member 11b of the bearing 11, and a retaining ring 14 that abuts against the spacer 13 to hold the bearing 11 and spacer 13 in place. The retaining ring 14 is, for example, a C-shaped snap ring that fits into a groove 15 formed on the inner surface of the housing 4.

[0038] With this configuration, the spacer 13 can be attached before the second carrier K2 is attached, and the dimensions of the spacer 13 can be set regardless of the dimensions of the second carrier K2, which tends to have a relatively large diameter. This increases the degree of freedom in designing the attachment location of the bearing 11 and improves the efficiency of the attachment work of the bearing 11. Furthermore, since the size of the bearing 11 and the size of the second carrier K2 can be set separately, the degree of freedom in designing the components of the planetary gear mechanism P is increased.

[0039] Furthermore, by using the spacer 13, even if there is an error in the formation position of the groove portion 15, by using a spacer 13 of an appropriate thickness, the outer member 11b can be fixed to the housing 4 without any rattle. Furthermore, by making the spacer 13 a completely annular member, the spacer 13 abuts against the entire circumference of the outer member 11b, improving the effect of preventing the outer member 11b from coming off.

[0040] After the bearing portion 11 has been fixed, the second carrier K2 is fitted and fixed to the first carrier K1. The planetary gear P2 may be attached to the second carrier K2 either before or after the second carrier K2 is attached to the first carrier K1. The ring gear P3 is fitted to the inner surface of the housing 4 as shown in FIG. 2.

[0041] (Guide part) When the rod 3 is reciprocated by the driving unit M, the rotation of the rod 3 is prevented by the housing 4. For this reason, as shown in Figures 4 to 6, a guide unit G is formed on the rod 3 opposite the threaded unit 10, spanning the rod 3 and the housing 4.

[0042] The guide portion G is composed of a slider 20 provided on the rod 3, a sliding member 21 attached to the slider 20, and a guide surface 22 provided on the housing 4 so that the sliding member 21 slides over a predetermined distance.

[0043] The slider 20 is a member having a U-shaped cross section perpendicular to the axis X, as shown in Figures 5(a) and (b). The slider 20 is fixed to the rod 3 by a mounting bolt, which is a fastening member 23, through a mounting hole 20b provided in a bottom 20a forming the U-shape. The mounting procedure involves inserting the rod 3 into the housing 4, and aligning the slider mounting position on the rod 3 with the positions of the opposing guide surfaces 22 formed in the opening of the housing 4. In this state, the slider 20, to which the sliding contact member 21 has been attached in advance, is positioned and fastened by the fastening member 23.

[0044] The sliding contact member 21 is attached to the slider 20 by inserting a groove-shaped insertion portion 21a formed in the sliding contact member 21 into a pair of U-shaped protrusions 20c of the slider 20. Claw portions are formed as engaging portions 21c on the inner wall 21b that forms the insertion portion 21a of the sliding contact member 21, and the claw portions are engaged with holes that are provided as engaged portions 20d in the pair of protrusions 20c. By engaging in this way using a so-called snap fit, the attachment work of the sliding contact member 21 to the slider 20 is simplified and the work costs can be reduced.

[0045] Furthermore, the tip edge of each protruding portion 20c is formed with a step portion 20e by cutting both ends along the direction of the axis X. As a result, when the insertion portion 21a of the sliding contact member 21 is inserted into the protruding portion 20c, the part of the tip edge excluding the step portion 20e is exposed on the upper surface of the sliding contact member 21, as shown in Fig. 5(a), and the sliding contact member 21 is prevented from rattling along the direction of the axis X relative to the protruding portion 20c.

[0046] Furthermore, the outward facing surface of each of the pair of sliding contact members 21 serves as sliding contact surface 21d, which comes into sliding contact with guide surface 22 provided on housing 4 to prevent rotation of rod 3. To ensure this prevention of rotation, the outward facing surfaces of the pair of protruding portions 20c of slider 20 are formed as flat receiving surfaces 20f, which come into face-to-face contact with flat surface 21e formed on the inside of insertion portion 21a of sliding contact member 21. By providing such receiving surfaces 20f and flat surface 21e, the rotation restriction function of rod 3 is reliably exerted, enabling the linear motion mechanism to have a high torque.

[0047] The slider 20 is made of a metal material such as steel or stainless steel, and can reliably withstand the anti-rotation torque of the rod 3 that is received as a reaction force from the guide surface 22 when the rod 3 moves back and forth. On the other hand, the sliding contact member 21 is made of a material with a low coefficient of friction, such as fluororesin.

[0048] Furthermore, by separating the slider 20 and the sliding contact member 21, the sliding contact member 21 can be attached to the slider 20 after the slider 20 is attached to the rod 3. If the sliding contact member 21 is attached before the slider 20 is attached, it becomes easy to fix the fastening member 23 between the pair of protruding portions 20c. With this configuration, when assembling the slider 20, there is no need to change the position of the rod 3, such as by inverting it, and an efficient assembly operation is possible.

[0049] (Control unit) The position of the rod 3 is detected by the control unit C. This detection is performed by a magnet 24 provided between the pair of sliding contact members 21 and a linear motion sensor 25 provided on a control board 26 in a state where it faces the magnet 24 closely.

[0050] 5, the magnet 24 is formed as a magnet block 24a by inserting a long piece of resin material. This magnet block 24a is fixed to the rod 3, but is attached so that an external force that would prevent the rod 3 from rotating is not input from the sliding contact member 21 to the magnet 24.

[0051] 5(b), the magnet block 24a is inserted between a pair of sliding contact members 21, and is arranged so that the back surface of the magnet block 24a abuts against the first seats 20g at two locations formed on the bottom 20a of the slider 20. As a result, the detection surface of the magnet 24 is set at a predetermined height relative to the surface of the rod 3.

[0052] Moreover, protruding portions 24b are provided near both ends of the magnet block 24a, and second seats 24c formed on these protruding portions 24b sandwich each of the two sliding contact members 21 in the direction along the axis X. At this time, if the second seats 24c are made to lightly abut against the sliding contact members 21, the magnet block 24a will not rattle when the rod 3 moves back and forth, and the accuracy of measuring the position of the rod 3 will be further improved.

[0053] Furthermore, the positioning of magnet 24 in the width direction, i.e., the direction intersecting axis X when viewed in a direction perpendicular to the surface of magnet 24, is performed by housing 4. That is, second guide surface 27, which is provided in the housing 4 near guide surface 22 and parallel to said guide surface 22, comes into sliding contact with protruding portion 24b, thereby positioning magnet 24 and guiding its movement.

[0054] In this way, after fixing the slider 20 and the sliding member 21 to the rod 3 inserted into the housing 4, the magnet block 24a is positioned relative to the sliding member 21 and the housing 4, whereby the magnet 24 can be easily installed relative to the rod 3.

[0055] With this configuration, when the rod 3 moves back and forth, no force that would prevent the rotation of the rod 3 acts on the magnet 24 from the sliding contact member 21. This eliminates the risk of damaging the magnet 24, and makes it possible to obtain a displacement detection device S with a rational structure and increased durability.

[0056] 4 and 7 show the configuration of the control unit C. The magnet 24 constituting the control unit C is fixed to the side of the rod 3 and is disposed with its detection surface facing upward. A linear motion sensor 25 is disposed facing and close to this magnet. The linear motion sensor 25 is mounted on a first substrate 26a (described later) and detects the position information of the rod 3. Based on the signal obtained by the linear motion sensor 25, the control unit C calculates the position of the rod 3 and transmits a drive signal to the drive unit M to move the rod 3 to the desired position.

[0057] 7(a) and 7(b), the control unit C includes, for example, a first board 26a and a second board 26b as the control board 26. The first board 26a is the board facing the magnet 24 and is a so-called control system board provided with the linear motion sensor 25 and the like. The second board 26b is a so-called power system board provided with a power supply circuit and the like.

[0058] In this embodiment, a spacer substrate 26c having, for example, an annular rectangular overall shape is provided between the first substrate 26a and the second substrate 26b, electrically connecting the first substrate 26a and the second substrate 26b. The first substrate 26a, the second substrate 26b, and the spacer substrate 26c are attached to a frame member 38 before being fixed to the housing 4. The frame member 38 also includes a connector 38a that connects the first substrate 26a and the like to the vehicle's ECU. By stacking multiple substrates in this manner, the overall planar area of the control unit C can be reduced, improving the mountability of the control unit C to a target device such as a linear motion mechanism.

[0059] 8, the spacer substrate 26c is provided with a plurality of relay terminals 30 that connect the soldered portions of the first substrate 26a and the soldered portions of the second substrate 26b. Here, the relay terminals 30 are configured in the shape of straight rods. The relay terminals 30 are made of a material that has excellent mechanical strength, electrical conductivity, thermal conductivity, and corrosion resistance, such as a Cu alloy-based material or an Fe alloy-based material.

[0060] Each relay terminal 30 is disposed to penetrate the spacer substrate 26c. For example, a plurality of holes are formed in the spacer substrate 26c in advance, and the relay terminals 30 are inserted into the holes. Alternatively, the spacer substrate 26c can be insert-molded with the relay terminals 30 embedded in predetermined positions.

[0061] To connect the first board 26a and the second board 26b to each of the relay terminals 30, it is necessary to accurately position the first board 26a and the second board 26b with respect to all of the relay terminals 30. For this reason, as shown in Fig. 9, a first positioning portion 31 is provided between the spacer board 26c and the first board 26a to position them relative to each other.

[0062] For example, the spacer substrate 26c may be provided with a first convex member 31a that protrudes toward the first substrate 26a and is fitted into a first fitting hole 31b provided in the first substrate 26a. On the other hand, the spacer substrate 26c and the second substrate 26b may also be provided with a second convex member 32a provided on the spacer substrate 26c and a second fitting hole 32b provided in the second substrate 26b as second positioning portions 32.

[0063] The provision of such first positioning portion 31 and second positioning portion 32 facilitates the connection of spacer substrate 26c to first substrate 26a and second substrate 26b, improving the efficiency of assembling multiple layers of substrates, thereby achieving a low-cost substrate mounting structure.

[0064] (heat resistant structure) Numerous electronic components are mounted on the first and second substrates 26a and 26b, which generate a certain amount of heat during normal use. This heat can cause changes in the dimensions of each substrate, which can change the mechanical properties of the heated soldered joints. As a result, the relative positions of the soldered joints on the first and second substrates 26a and 26b can shift along the planar direction of the substrates, causing problems such as cracking of the soldered joints.

[0065] Therefore, the spacer substrate 26c of this embodiment is provided with slits 33a as partitions 33 that separate the regions A in which a predetermined number of relay terminals 30 are arranged. Specifically, as shown in Fig. 8, a plurality of slits 33a extending perpendicularly to the periphery of the spacer substrate 26c are formed for each region A of a predetermined area. To achieve this, only the portions of the slits 33a are protruded toward the center of the spacer substrate 26c, and the slits 33a are formed inside these protruding portions 34. This ensures connection rigidity between the regions A on both sides of the slits 33a.

[0066] This configuration allows relative displacement between predetermined regions A of spacer substrate 26c, absorbing changes in the posture of relay terminal 30 that occur as the temperature of first substrate 26a and second substrate 26b rises. Therefore, excessive bending force is not applied to the soldered portions of first substrate 26a and second substrate 26b, and the soldered portions can be effectively protected.

[0067] (Grounding structure) In the substrate mounting structure of this embodiment, the first substrate 26a and the second substrate 26b are provided with the following grounding structure to suppress noise generation: A ground terminal 36 is provided for at least one of the first fixing portion 35a used to fix the first substrate 26a to the housing 4 and the second fixing portion 35b used to fix the second substrate 26b to the housing 4.

[0068] This ground terminal 36 grounds the second substrate 26b etc. to the frame member 38 by attaching the second substrate 26b etc. to the frame member 38. Furthermore, the frame member 38 is fixed to the housing 4 using screw members 39 etc., so that the second substrate 26b etc. are grounded to the housing 4.

[0069] 10(a) and 10(b), a ground terminal 36 formed by bending a metal plate is attached to a fixing screw 37 that fixes the second substrate 26b to a frame member 38, for example. The ground terminal 36 is in contact with the ground circuit of the second substrate 26b. One side of the ground terminal 36 is provided with an elastic portion 36a that protrudes away from the fixing screw 37. The elastic portion 36a protrudes outward from the second substrate 26b, and is configured so that the second substrate 26b and the housing 4 are electrically connected simply by attaching the frame member 38 having the second substrate 26b to the housing 4.

[0070] This configuration can reduce the effects of noise on first substrate 26a and second substrate 26b from surrounding devices. Furthermore, when first substrate 26a and second substrate 26b are attached to various devices, grounding work can be performed at the same time, resulting in a highly reliable substrate mounting structure with excellent attachment workability.

[0071] (heat dissipation structure) The first board 26a and second board 26b of this configuration generate heat during use. In particular, the amount of heat generated by the second board 26b, which is a power supply board, is greater than that of the first board 26a. If the amount of heat generated becomes excessive, there is a possibility that the mounted components and soldered portions of the second board 26b may be damaged. Therefore, the board mounting structure of this configuration is provided with the following heat dissipation structure.

[0072] 11, a pressing portion 40 that presses, for example, a portion of second substrate 26b toward housing 4 is formed on a portion of frame member 38. A heat dissipation portion 41 is formed on the back surface of the portion of second substrate 26b that faces pressing portion 40, and when second substrate 26b etc. are attached to housing 4, this heat dissipation portion 41 abuts against a heat dissipation sheet 42 provided on housing 4. In other words, the pressing portion 40 is configured to press the back surface of second substrate 26b so that heat dissipation portion 41 abuts against heat dissipation sheet 42 reliably.

[0073] With this configuration, simply by attaching the frame member 38, which already holds the second substrate 26b, etc., to the housing 4, the heat dissipation section 41 provided on the second substrate 26b is reliably pressed against the heat dissipation sheet 42 of the housing 4, thereby achieving a good heat dissipation effect.

[0074] As in this configuration, the necessary control boards 26 are divided into the first control board 26a and the second power board 26b, and the heat dissipation section 41 is provided on the second board 26b, thereby enhancing the heat removal effect. Furthermore, because the control boards 26 are divided according to the level of heat generation, damage to soldered portions caused by heat, particularly on the second power board 26b, can be more effectively prevented.

[0075] Furthermore, the pressing portion 40 of this configuration simply presses the heat dissipation portion 41 against the heat dissipation sheet 42, and does not restrict the thermal expansion of the second substrate 26b etc. along its planar direction. Therefore, no unexpected stress is generated in the second substrate 26b, and damage to the soldered portions can be effectively prevented.

[0076] (Seal structure) The first substrate 26a, the second substrate 26b, and the spacer substrate 26c are fixed to the housing 4 while being attached to one side of a frame member 38, and the opposite side of the frame member 38 is covered with a cover member 43. When the frame member 38 and the cover member 43 are attached to the housing 4, annular seal members 44 are disposed between the peripheral edge of one side of the frame member 38 and the housing 4, and between the peripheral edge of the other side of the frame member 38 and the peripheral edge of the cover member 43.

[0077] This seal member 44 is made of, for example, any of various rubber materials having a circular cross section, and has a planar shape that corresponds to the peripheral shape of the frame member 38. At least one of the frame member 38, cover member 43, and housing 4, which are arranged opposite each other, has a fixing groove 45 formed therein, into which the seal member 44 fits.

[0078] This makes it easier to install the seal member 44 by making it less likely to shift position when installing the frame member 38 and the cover member 43. Also, since the seal member 44 is prevented from shifting position after installation, it is possible to obtain a substrate mounting structure that has excellent dustproof and waterproof properties over the long term. [Industrial Applicability]

[0079] The planetary gear mechanism of the present invention can be widely used in linear motion devices configured to transmit the rotational driving force of a drive motor to a rod that moves back and forth while its rotation is restricted. [Explanation of symbols]

[0080] 2 nuts 2a Bulge 3 rods 4. Housing 9 Output Gear 10 Threaded part 11 Bearing section 11a Inner member 11b Outer member 12 Fixing screw part 13 Spacer 14 Retaining ring K Carrier K1 1st Carrier K2 Second Carrier Ka 1st fitting part Kb 2nd fitting part M Drive Unit P planetary gear mechanism P2 planetary gear X-axis center

Claims

1. Housing and a drive unit provided in the housing; a rod having a threaded portion to which a driving force is transmitted from an output gear of the drive unit, the rod reciprocating along an axis while being prevented from rotating relative to the housing, a nut that is screwed onto the threaded portion; a bearing portion that rotatably supports the nut on the housing; a carrier for holding a planetary gear, and a carrier for holding a planetary gear, the carrier being inserted and fixed into the innermost part of the housing with the bearing portion facing the innermost part; a first carrier that abuts against an inner member of the bearing portion and is threadedly engaged with the nut; a second carrier attached to the first carrier and holding the planetary gear; a retaining ring attached to the inner surface of the housing so as to fix the outer member of the bearing portion to the housing; a planetary gear mechanism in which the first carrier has a fixing screw portion that meshes with the nut, and the bearing portion is configured so that an inner member of the bearing portion is sandwiched between a bulge protruding from the surface of the nut and an end face of the first carrier.

2. 2. The planetary gear mechanism according to claim 1, wherein the outer diameter of the second carrier is larger than the inner diameter of the retaining ring.

3. 3. The planetary gear mechanism according to claim 1, wherein the first carrier and the second carrier are fitted together by a first fitting portion and a second fitting portion that are connected in two stages along the direction of the axis, and the second fitting portion is a spline-shaped fitting portion.

4. 4. The planetary gear mechanism according to claim 1, further comprising an annular spacer for preventing the outer member of the bearing portion from coming into contact with the retaining ring, the spacer being fixed to an inner surface of the housing.

5. A housing, a drive unit provided in the housing; a rod having a threaded portion to which a driving force is transmitted from an output gear of the drive unit, the rod reciprocating along an axis while being prevented from rotating relative to the housing, a nut that is screwed onto the threaded portion; a bearing portion that rotatably supports the nut on the housing; a carrier for holding a planetary gear, and a carrier for holding a planetary gear, the carrier being inserted and fixed into the innermost part of the housing with the bearing portion facing the innermost part; a first carrier that abuts against an inner member of the bearing portion and is threadedly engaged with the nut; a second carrier attached to the first carrier and holding the planetary gear; a retaining ring attached to the inner surface of the housing to fix the outer member of the bearing portion to the housing, A planetary gear mechanism in which the outer diameter of the first carrier is smaller than the inner diameter of the retaining ring, and the outer diameter of the second carrier is larger than the inner diameter of the retaining ring.

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