JP7723344B2 - Planetary gear mechanism - Google Patents

Description

The present invention relates to a planetary gear mechanism that transmits the rotational drive of a drive unit to a rod that moves back and forth while its rotation is restricted in a linear motion device.

An example of such a conventional planetary gear mechanism is shown in Patent Document 1 (see [0006], [0024] and Figure 2).

This linear motion mechanism comprises a housing 1a connected to the suspension mechanism, an electric motor housed inside the 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. The carrier that holds the 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 against the inner surface of the housing 1a, the rod 2 moves back and forth while its rotation is restricted.

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

Between the sun gear 31 and the ring gear 33, a carrier is positioned, integrally formed with a nut member 36 and supporting three planetary gears 32. A bearing 37 is provided between the outer surface of the carrier's end 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 on the holder 34 and a connecting cover 11 attached 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, preventing them from rotating relative to the housing 1a.

JP 2016-60393 A

In the conventional planetary gear mechanism described above, the carrier and nut member 36 were 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 thread onto the rod 2 to a more wear-resistant material, such as brass. If the entire carrier were made of brass, the weight and cost of the linear motion mechanism would increase.

In addition, this planetary gear mechanism uses a holder 34 to secure 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 secure 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 assembly labor, resulting in increased costs.

If the holder 34 were to be omitted, the difference in outer diameter between the ring gear 33 and the bearing 37 would be too great, making the formation of the mounting portion for the bearing 37 particularly complicated. 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 would be 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 nearby makes fixing that end extremely difficult.

As such, conventional planetary gear mechanisms have various issues that need to be resolved 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 more rational configuration.

(Characteristics)
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 the inner surface of the housing so as to fix the outer member of the bearing portion to the housing ;
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.

(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.

In this configuration, the carrier that holds the planetary gears is divided into a first carrier and a second carrier, allowing the bearings and retaining rings located at the rear of these carriers to 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 size of the bearings and retaining rings is no longer 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.

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 assembling work can be made more efficient.

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.

(effect)
As a result of the present configuration in which the first carrier and the second carrier are separate, the bearing assembly 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 bearing assembly and improves the efficiency of the assembly process.

In addition, the size of the bearing portion and the size of the second carrier can be set separately, which increases the degree of freedom when designing the components of the planetary gear mechanism.

In the planetary gear mechanism according to the present invention, the first carrier and the second carrier are engaged with each other by first and second engaging portions that are connected in two stages along the axis, and it is preferable that the second engaging portion be a spline-shaped engaging portion.

(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.

In addition, by configuring the mating portion in two stages, a first mating portion and a second mating portion, with one of the second mating portions being splined, the first carrier and second carrier can rotate stably as a single unit, ensuring that the rotation of the planetary gear is reliably transmitted to the nut.

Furthermore, before the second carrier is mated with the first carrier, the first carrier is threaded onto the nut with the spline portion of the first carrier exposed. At this time, the spline portion can serve as the input portion for the fastening tool, making the first carrier easier to secure.

The planetary gear mechanism according to the present invention can be configured to include an annular spacer that prevents the outer member of the bearing portion from coming into contact with the retaining ring, and that is fixed to the inner surface of the housing.

(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 a spacer is used, it can be installed before attaching the second carrier, which makes the installation of the bearing more efficient.

FIG. 1 is an explanatory diagram showing an example of use of a displacement detection device according to an embodiment of the present invention; An explanatory diagram showing the configuration of the drive unit An exploded perspective view showing the configuration of the drive unit 1 is a cross-sectional side view showing the configuration of a displacement detection device; FIG. 1 is a perspective view showing the configuration of a main part of a displacement detection device; A longitudinal cross-sectional view showing the configuration of the main part of the displacement detection device. FIG. 1 is a perspective view showing the configuration of a control unit. FIG. 1 is a perspective view showing the configuration of a spacer substrate; FIG. 1 is a perspective view showing a fitting structure of a first substrate and a second substrate; An explanatory diagram showing the grounding structure of the control unit An explanatory diagram showing the heat dissipation structure of the control unit An explanatory diagram showing the sealing structure of the control unit

(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, to reciprocate a rod 3 that is threadedly inserted into the nut 2. 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 reciprocate without rotating.

Figures 1 and 2 show the configuration of the linear motion mechanism according to this embodiment. The linear motion mechanism comprises a control unit C located on the left side of Figure 1 and a drive unit M located 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 signals from this linear motion sensor 25. Based on the calculation results, the control unit C supplies a drive signal to the drive unit M to move the rod 3 to the desired position.

(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.

(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.

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

The nut 2 is cylindrical, with a female trapezoidal thread 9a formed on its inner surface as the output gear 9 of the drive unit M. On the other hand, the rod 3 has a male trapezoidal thread 10a formed on its outer surface as the threaded portion 10. The nut 2 is made of brass for wear resistance. The rod 3 moves back and forth without rotating relative to the housing 4 by abutting the 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 internally into the inner surface of the housing 4.

The first carrier K1 is fitted onto one end of the nut 2 and screwed into place via the 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 clamped along the axis X by this bulge 2a and the end face of the first carrier K1. This configuration simplifies the fixing of the bearing portion 11 and the first carrier K1 to the nut 2, improving the efficiency of these assembly operations.

The second carrier K2, which holds the planetary gear P2, is fitted and fixed further outward from the first carrier K1. This fitting and fixing is achieved using two types of fitting portions. One is a cylindrical first fitting portion Ka formed on the rear side in the fitting direction along the axis X when viewed from the second carrier K2 side. This is formed by a cylindrical outer fitting surface formed on the outer surface of the first carrier K1 and a cylindrical inner fitting 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 front side in the fitting direction when viewed from the second carrier K2 side.

The second mating portion Kb is configured, for example, with 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, resulting in a durable carrier K. Furthermore, when threading the first carrier K1 into the nut 2, the second mating portion Kb can be used as the engagement portion of a fastening tool. The first carrier K1 and the second carrier K2 are made of steel instead of the conventional brass, resulting in lighter weight and lower costs.

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 to attach the bearing portion 11 to the nut 2, clamp the bearing portion 11 with the first carrier K1, and then secure them to the housing 4. The second carrier K2 is then attached to the first carrier K1.

The bearing 11 is secured 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.

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 be relatively large. This increases the degree of freedom in designing the attachment location of the bearing portion 11 and improves the efficiency of the attachment work of the bearing portion 11. Furthermore, since the size of the bearing portion 11 and the size of the second carrier K2 can be set separately, there is increased freedom in designing the components of the planetary gear mechanism P.

Furthermore, by using a spacer 13 of an appropriate thickness, even if there is an error in the formation position of the groove portion 15, 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 prevention effect of the outer member 11b from slipping out.

After the bearing portion 11 has been secured, the second carrier K2 is fitted and secured to the first carrier K1. The planetary gear P2 can 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 Figure 2.

(Guide part)
When the rod 3 is reciprocated by the drive 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.

The guide section G is composed of a slider 20 attached to the rod 3, a sliding contact member 21 attached to the slider 20, and a guide surface 22 provided on the housing 4 so that the sliding contact member 21 can slide over a predetermined distance.

As shown in Figures 5(a) and (b), the slider 20 is a member having a U-shaped cross section perpendicular to the axis X. The slider 20 is fixed to the rod 3 by fastening members 23, which are mounting bolts, through mounting holes 20b provided in the bottom 20a of 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 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 already been attached, is positioned and fastened with the fastening members 23.

The sliding contact member 21 is attached to the slider 20 by inserting the groove-shaped insertion portion 21a formed on the sliding contact member 21 into a pair of U-shaped protrusions 20c on the slider 20. The inner wall 21b forming the insertion portion 21a of the sliding contact member 21 has a claw portion formed as an engaging portion 21c, which engages with holes provided as engaged portions 20d in the pair of protrusions 20c. This so-called snap-fit engagement simplifies the attachment process of the sliding contact member 21 to the slider 20, reducing installation costs.

Furthermore, the tip edge of each protrusion 20c has a step 20e formed 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 protrusion 20c, the tip edge excluding the step 20e is exposed on the upper surface of the sliding contact member 21, as shown in Figure 5(a), preventing the sliding contact member 21 from rattling along the direction of the axis X relative to the protrusion 20c.

The outward facing surface of each of the pair of sliding contact members 21 forms 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 planar receiving surfaces 20f, which come into surface 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.

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.

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 has been attached to the rod 3. If the sliding contact member 21 is attached before the slider 20 is attached, the fastening member 23 can be easily secured between the pair of protrusions 20c. With this configuration, there is no need to invert the rod 3 or otherwise change its position when assembling the slider 20, allowing for efficient assembly work.

(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.

As shown in Figure 5, the magnet 24 is formed into 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.

Specifically, as shown in Figure 5(b), the magnet block 24a is inserted between a pair of sliding contact members 21, and the back surface of the magnet block 24a is positioned so that it abuts against two first seats 20g formed on the bottom 20a of the slider 20. This positions the detection surface of the magnet 24 at a predetermined height relative to the surface of the rod 3.

In addition, protrusions 24b are provided near both ends of the magnet block 24a, and second seats 24c formed on these protrusions 24b sandwich each of the two sliding contact members 21 in the direction along the axis X. If the second seats 24c are made to lightly abut the sliding contact members 21, the magnet block 24a will not rattle when the rod 3 moves back and forth, further improving the accuracy of measuring the position of the rod 3.

Furthermore, the magnet 24 is positioned in the width direction, i.e., in the direction intersecting the axis X when viewed in a direction perpendicular to the surface of the magnet 24, by the housing 4. In other words, a second guide surface 27, provided near and parallel to the guide surface 22 of the housing 4, slides against the protruding portion 24b, thereby positioning the magnet 24 and guiding its movement.

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

With this configuration, the force that prevents the rotation of the rod 3 during reciprocating movement of the rod 3 is not applied from the sliding contact member 21 to the magnet 24. This eliminates the risk of damage to the magnet 24, resulting in a displacement detection device S with a rational structure and increased durability.

Figures 4 and 7 show the configuration of control unit C. The magnet 24 that constitutes control unit C is fixed to the side of rod 3 and is positioned with its detection surface facing upward. A linear motion sensor 25 is positioned facing this magnet in close proximity. The linear motion sensor 25 is mounted on a first board 26a (described below) and detects the position information of rod 3. Based on the signal obtained by linear motion sensor 25, control unit C calculates the position of rod 3 and sends a drive signal to drive unit M to move rod 3 to the desired position.

As shown in Figures 7(a) and 7(b), the control unit C includes a control board 26, which includes, for example, a first board 26a and a second board 26b. The first board 26a is the board facing the magnet 24 and is a so-called control system board equipped with a linear motion sensor 25 and the like. The second board 26b is a so-called power system board equipped with a power supply circuit and the like.

In this embodiment, a spacer substrate 26c, which is, for example, rectangular and annular in shape overall, is provided between the first substrate 26a and the second substrate 26b, electrically connecting the first substrate 26a and the second substrate 26b. These three substrates, the first substrate 26a, the second substrate 26b, and the spacer substrate 26c, are attached to a frame member 38 in advance 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 mountability on target equipment such as a linear motion mechanism.

As shown in Figure 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. These 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.

Each relay terminal 30 is positioned to penetrate the spacer substrate 26c. For example, multiple holes can be pre-formed in the spacer substrate 26c, and the relay terminals 30 can be inserted and fitted into them. Alternatively, the spacer substrate 26c can be insert-molded with the relay terminals 30 embedded in predetermined positions.

To connect the first board 26a and the second board 26b to each relay terminal 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. To that end, as shown in Figure 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.

For example, a first convex member 31a that protrudes toward the first substrate 26a is provided on the spacer substrate 26c, and is fitted into a first fitting hole 31b provided in the first substrate 26a. Meanwhile, 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 on the second substrate 26b as second positioning portions 32.

By providing such first positioning portion 31 and second positioning portion 32, the work of connecting spacer substrate 26c to first substrate 26a and second substrate 26b becomes easier, and the work of assembling multiple layers of substrates becomes more efficient. This makes it possible to obtain a low-cost substrate mounting structure.

(Heat-resistant structure)
The first and second substrates 26a and 26b are mounted with numerous electronic components, generating a certain amount of heat during normal use. This heat can cause changes in the dimensions of each substrate, which can affect 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.

In this embodiment, the spacer substrate 26c is provided with slits 33a as partitions 33 that separate the areas A, each of which has a predetermined number of relay terminals 30 arranged therein. Specifically, as shown in FIG. 8, for each area A of a predetermined area, multiple slits 33a extending perpendicularly to the periphery of the spacer substrate 26c are formed. To achieve this, only the portions of the slits 33a protrude toward the center of the spacer substrate 26c, and the slits 33a are formed inside these protruding portions 34. This ensures the connection rigidity between the areas A on either side of the slits 33a.

This configuration allows relative displacement between predetermined areas A of the spacer substrate 26c, absorbing changes in the position of the relay terminal 30 as the temperature of the first substrate 26a and second substrate 26b rises. This prevents excessive bending forces from acting on the soldered portions of the first substrate 26a and second substrate 26b, effectively protecting the soldered portions.

(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.

This ground terminal 36 grounds the second board 26b, etc. to the frame member 38 by attaching the second board 26b, etc. to the frame member 38. Furthermore, the frame member 38 is fixed to the housing 4 using screw members 39, etc., thereby grounding the second board 26b, etc. to the housing 4.

Specifically, as shown in Figures 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 board 26b to a frame member 38, for example. This ground terminal 36 is in contact with the ground circuit of the second board 26b. One side of the ground terminal 36 is provided with an elastic portion 36a that protrudes away from the fixing screw 37. This elastic portion 36a protrudes outward from the second board 26b, and is configured so that electrical continuity between the second board 26b and the housing 4 is achieved simply by attaching the frame member 38 equipped with the second board 26b to the housing 4.

This configuration reduces the effects of noise on the first and second boards 26a and 26b from surrounding devices. Furthermore, when attaching the first and second boards 26a and 26b to various devices, grounding work can be performed at the same time, resulting in a highly reliable board mounting structure with excellent installation workability.

(heat dissipation structure)
The first and second boards 26a, 26b of this configuration generate heat during use. In particular, the second board 26b, which is a power supply board, generates more heat than the first board 26a. If the heat generation becomes excessive, 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.

As shown in Figure 11, a pressing portion 40 is formed on a portion of the frame member 38, for example, to press a portion of the second board 26b toward the housing 4. A heat dissipation portion 41 is formed on the back surface of the portion of the second board 26b facing the pressing portion 40, and when the second board 26b etc. is attached to the housing 4, this heat dissipation portion 41 abuts against a heat dissipation sheet 42 provided on the housing 4. In other words, the pressing portion 40 is configured to press against the back surface of the second board 26b so that the heat dissipation portion 41 abuts against the heat dissipation sheet 42 reliably.

With this configuration, simply by attaching the frame member 38, which already holds the second board 26b, etc., to the housing 4, the heat dissipation section 41 on the second board 26b is reliably pressed against the heat dissipation sheet 42 on the housing 4, achieving excellent heat dissipation effects.

As in this configuration, the necessary control boards 26 are separated 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 separated according to the level of heat generated, damage to soldered joints caused by heat, particularly on the second power board 26b, can be more effectively prevented.

Furthermore, the pressing portion 40 in 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 and other components along their planar direction. This prevents unexpected stress from occurring in the second substrate 26b, effectively preventing damage to the soldered portions.

(Seal structure)
The first substrate 26a, the second substrate 26b, and the spacer substrate 26c are fixed to the housing 4 while 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.

This sealing member 44 is made of, for example, various rubber materials with 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 in it into which the sealing member 44 fits.

This makes it difficult for the seal member 44 to shift position when attaching the frame member 38 and cover member 43, making the attachment process easier. Furthermore, this prevents the seal member 44 from shifting position after attachment, resulting in a board mounting structure that remains dustproof and waterproof for a long period of time.

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.

2 Nut 2a Bulging portion 3 Rod 4 Housing 9 Output gear 10 Threaded portion 11 Bearing portion 11a Inner member 11b Outer member 12 Fixing threaded portion 13 Spacer 14 Retaining ring K Carrier K1 First carrier K2 Second carrier Ka First fitting portion Kb Second fitting portion M Drive portion P Planetary gear mechanism P2 Planetary gear X Shaft center

Claims (5)

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. A planetary gear mechanism as described in claim 1, wherein the outer diameter of the second carrier is larger than the inner diameter of the retaining ring. 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. 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. 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 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 .