Patent Description:
<CIT> discloses a joint structure including a first robot member, a second robot member, and a speed reducer incorporated in a joint portion that connects the first robot member and the second robot member. <CIT> discloses a drive device that can detect torque output from the drive device with high accuracy and can keep the cost of parts for detecting the torque low.

As customers need, there are various requests regarding a fixing mode in which a speed reducer is fixed to the first robot member. As an example of this, there is a fixing mode in which a part of the speed reducer and the first robot member are brought into pressure contact with each other in a radial direction. In a case where this is adopted, a radial load that may adversely affect meshing between an internal gear and an external gear acts on the speed reducer. A technique devised in relation to this problem has not yet been proposed.

One object of the present disclosure is to provide a technique capable of suppressing an adverse effect on meshing between an internal gear and an external gear when a part of a speed reducer and a first robot member are brought into pressure contact in a radial direction.

A robot joint structure according to the present disclosure is a robot joint structure including a first robot member; a second robot member; and a speed reducer incorporated in a joint portion that connects the first robot member and the second robot member to each other, in which the speed reducer includes an external gear, an internal gear that meshes with the external gear, a fixing member that is provided so as to be non-rotatable relative to the internal gear and is disposed on an input side in an axial direction with respect to the internal gear, the fixing member is fixed to the first robot member by bringing an inner peripheral surface of the first robot member and an outer peripheral surface of the fixing member into pressure contact with each other by fastening using the first fastening member, and at least a part of an axial range of the first fastening member does not overlap internal teeth of the internal gear when viewed in a radial direction.

According to the present disclosure, it is possible to suppress an adverse effect on meshing between the internal gear and the external gear.

Embodiments will be described below. The same reference numerals will be given to the same components, and overlapping descriptions will be omitted. In the respective drawings, for convenience of explanation, components are appropriately omitted, enlarged, or reduced. The drawings should be viewed in accordance with the orientation of the reference numerals.

<FIG> will be referred to. A robot <NUM> in which a joint structure <NUM> of the present embodiment is used is an articulated robot, and is used as an industrial robot, a service robot (for example, a cooking robot, a domestic robot, a medical robot, or the like). Although not illustrated, the robot <NUM> includes a base, and a plurality of arms supported by the base and connected in series.

The robot joint structure <NUM> includes a first robot member <NUM> and a second robot member <NUM>, and an actuator <NUM> including a speed reducer <NUM> incorporated in a joint portion <NUM> that connects the first robot member <NUM> and the second robot member <NUM> to each other. The first robot member <NUM> and the second robot member <NUM> are either arms or bases of the robot <NUM>. Here, an example in which both the first robot member <NUM> and the second robot member <NUM> serve as arms is shown, but one of the members may serve as a base. The first robot member <NUM> of the present embodiment serves as a support member that supports the actuator <NUM>, and the second robot member <NUM> serves as a driven member driven by the actuator <NUM>.

The first robot member <NUM> of the present embodiment includes a tubular first casing 14a that accommodates the speed reducer <NUM>, and a second casing 14b that accommodates a driving device <NUM>. The first casing 14a and the second casing 14b of the present embodiment are separate members and are fixed to each other by using bolts or the like. The second robot member <NUM> includes a tubular third casing 16a provided on an extension of the first casing 14a in an axial direction X.

In addition to the speed reducer <NUM>, the actuator <NUM> includes a driving device <NUM> that inputs rotational power to the speed reducer <NUM>. Although the driving device <NUM> of the present embodiment is a motor, a specific example thereof is not particularly limited and may be a gear motor, an engine, or the like. The actuator <NUM> is formed with a hollow portion 22a that penetrates the actuator <NUM> in the axial direction X (described below). A wiring member such as a cable used for the robot <NUM> is inserted through the hollow portion 22a.

The speed reducer <NUM> includes an input shaft <NUM> to which rotational power is input from the driving device <NUM>, an external gear <NUM> driven by the input shaft <NUM>, and a plurality of internal gears <NUM> and <NUM> that mesh with the external gear <NUM>. In addition to this, the speed reducer <NUM> includes a fixing member <NUM> that is provided so as to be non-rotatable relative to the internal gear <NUM> and fixed to the first robot member <NUM>, a main bearing <NUM> that connects (supports) the first robot member <NUM> and the second robot member <NUM> so as to be rotatable relative to each other, a bearing housing <NUM> that accommodates the main bearing <NUM>, and a synchronization member <NUM> that is fixed to the second robot member <NUM> and is synchronizable with an axial rotation component of the external gear <NUM>. Descriptions relating to the fixing member <NUM>, the main bearing <NUM>, the bearing housing <NUM>, and the synchronization member <NUM> will be given below, and the surrounding structure will be described first.

In the present specification, a direction along a center C32 of the internal gear <NUM> is referred to as the axial direction X, and a radial direction and a circumferential direction having the center C32 as the center of a circle are also simply referred to as a radial direction and a circumferential direction. Additionally, for convenience of description, one side (right side in <FIG>) in the axial direction X is referred to as an input side, and the other side in the axial direction X is referred to as a counter-input side.

The external gear <NUM> and the internal gears <NUM> and <NUM> constitute a gear mechanism that outputs the output rotation decelerated with respect to the rotation of the input shaft <NUM>. The gear mechanism can rotate one of the external gear <NUM> and the internal gears <NUM> and <NUM> by driving the external gear <NUM> via the input shaft <NUM>. The speed reducer <NUM> of the present embodiment is a bending meshing type speed reducer in which the external gear <NUM> serves as a flexible gear. Additionally, the speed reducer <NUM> of the present embodiment is a tubular bending meshing type speed reducer having a first internal gear <NUM> and a second internal gear <NUM> as the internal gears <NUM> and <NUM>. The first internal gear <NUM> is relatively non-rotatably connected to the first robot member <NUM> via the fixing member <NUM>. The second internal gear <NUM> is relatively non-rotatably connected to the second robot member <NUM> via the synchronization member <NUM>. In the present embodiment, the first internal gear <NUM> is a stationary-side internal gear that is fixed to a support member (first robot member <NUM>) so as not to rotate. Additionally, the second internal gear <NUM> is a drive-side internal gear that drives a driven member (second robot member <NUM>) by outputting the output rotation.

The input shaft <NUM> is provided so as to be capable of transmitting rotational power from an output shaft 26a of the driving device <NUM>. In order to realize this, the input shaft <NUM> of the present embodiment is integrally rotatably connected to the output shaft 26a by using a connection member <NUM>. The input shaft <NUM> includes a gear drive unit 28a that drives the external gear <NUM> by rotating around a rotation center line C28 thereof. The gear drive unit 28a of the input shaft <NUM> used in the bending meshing type speed reducer <NUM> is a wave generator that is driven by flexibly deforming the external gear <NUM>. The gear drive unit 28a serving as the wave generator has an elliptical shape in a cross section perpendicular to the axial direction X. The term "ellipse" herein is not limited to a geometrically exact ellipse but also includes a substantial ellipse.

The external gear <NUM> serving as the flexible gear is a tubular member having flexibility that can be flexibly deformed by the rotation of the gear drive unit 28a of the input shaft <NUM>. The external gear <NUM> is relatively rotatably supported by the input shaft <NUM> via a gear bearing <NUM> disposed between the external gear <NUM> and the gear drive unit 28a of the input shaft <NUM>. Although the gear bearing <NUM> of the present embodiment is a double-row bearing, the type thereof is not particularly limited and may be, for example, a single-row bearing such as a roller bearing, a needle bearing, or a ball bearing.

Unlike the external gear <NUM> serving as the flexible gear, the internal gears <NUM> and <NUM> of the present embodiment have a stiffness such that the internal gears <NUM> and <NUM> are not deformed following the rotation of the input shaft <NUM>. The first internal gear <NUM> is provided on an inner peripheral portion of a first internal tooth member <NUM> as a part of the first internal tooth member <NUM>. The first internal tooth member <NUM> is integrally formed of the same material as the first internal gear <NUM>. The first internal gear <NUM> is configured by providing a plurality of first internal teeth 32b on an inner peripheral portion of a first annular portion 32a provided on the first internal tooth member <NUM>. The second internal gear <NUM> is provided on an inner peripheral portion of a second internal tooth member <NUM> as a part of the second internal tooth member <NUM>. The second internal tooth member <NUM> is integrally formed of the same material as the second internal gear <NUM>. The second internal gear <NUM> is configured by providing a plurality of second internal teeth 33b on an inner peripheral portion of a second annular portion 33a provided on the second internal tooth member <NUM>.

The operation relating to the above speed reducer <NUM> will be described. In the case of the bending meshing type speed reducer <NUM>, when the gear drive unit 28a of the input shaft <NUM> serving as the wave generator rotates, the external gear <NUM> (flexible gear) is flexibly deformed so as to form an elliptical shape that matches the shape of the gear drive unit 28a. When the external gear <NUM> is flexibly deformed in this way, a meshing position between the external gear <NUM> and the internal gears <NUM> and <NUM> changes in a rotation direction of the input shaft <NUM>. In the present example, the number of teeth (for example, <NUM>) of the first internal gear <NUM> is <NUM> × n (n is a positive integer) more than the number of teeth (for example, <NUM>) of the external gear <NUM>, and the number of teeth of the second internal gear <NUM> is the same as the number of teeth of the external gear <NUM>. Thus, each time the input shaft <NUM> makes one rotation, the external gear <NUM> rotates by a difference in the number of teeth between the first internal gear <NUM> and the external gear <NUM>, and an axial rotation component thereof is output from the second internal gear <NUM> serving as the drive-side internal gear to the second robot member <NUM> serving as the driven member. In this case, the output rotation decelerated at a reduction ratio according to the number of teeth of the external gear <NUM> and the internal gears <NUM> and <NUM> is output with respect to the input rotation of the input shaft <NUM>.

<FIG> will be referred to. The description of the fixing member <NUM> and the like will be made. The fixing member <NUM> is disposed on the input side with respect to the first internal gear <NUM> (first internal tooth member <NUM>). The fixing member <NUM> of the present embodiment is a member separate from the first internal gear <NUM> (first internal tooth member <NUM>). The fixing member <NUM> has a continuous disk shape around the center C32 of the first internal gear <NUM>, and the input shaft <NUM> penetrates the inside thereof.

The fixing member <NUM> is relatively non-rotatably fixed to the first robot member <NUM> by bringing an inner peripheral surface of the first robot member <NUM> and an outer peripheral surface of the fixing member <NUM> into pressure contact with each other in the radial direction by fastening using the first fastening member B1. The expression "fastening the fastening member herein means fastening a plurality of fastened members by applying a fastening force along a shaft portion of the first fastening member B1 to the plurality of fastened members. The first fastening member B1 of the present embodiment fastens the first robot member <NUM> and the fixing member <NUM> in the radial direction as the plurality of fastened members. The expression "fastening in the radial direction" herein means fastening a plurality of fastened members by applying a fastening force in the radial direction.

The fixing member <NUM> is made of the first internal tooth member <NUM>, that is, a material having a Young's modulus [N/mm<NUM>] larger than that of the first internal gear <NUM>. In order to realize this, for example, the first internal tooth member <NUM> may be made of a resin-based material, and the fixing member <NUM> may be made of a metal-based material. The resin-based material refers to a material having resin as a main material. The resin-based material may be, for example, a material using only a resin such as a general-purpose engineering plastic or a special engineer plastic, or a composite material using a resin such as a carbon fiber reinforced resin or a glass fiber reinforced resin. The metal-based material refers to a material having metal as a main material The metal-based material may be, for example, a material using only a metal such as an iron-based material, an aluminum-based material, or an alloy, or a composite material using a metal such as a fiber reinforced metal. In addition, the material of each member is not particularly limited.

However, in the present embodiment, not only the first internal gear <NUM> but also the second internal gear <NUM> and the synchronization member <NUM> are made of the resin-based material, whereby weight saving is achieved. On the other hand, the bearing housing <NUM> is made of a material having a Young's modulus higher than that of the first internal gear <NUM>, for example, the metal-based material.

Although the first fastening member B1 of the present embodiment is a bolt, a specific example thereof is not particularly limited and may be, for example, a rivet (for example, a blind rivet). The first robot member <NUM> includes a first counterbored hole 14c that is provided on an outer peripheral surface of the first robot member <NUM> to accommodate a head portion of the first fastening member B1. The first counterbored hole 14c is formed as a recessed portion that is recessed radially inward in the first casing 14a of the first robot member <NUM>. The fixing member <NUM> includes a first female screw hole 34a for screwing the first fastening member B1 in the radial direction.

An axial range A1 of the first fastening member B1 is assumed.

At least a part of the axial range A1 does not overlap the first internal teeth 32b of the first internal gear <NUM> when viewed in the radial direction. In the present embodiment, the entire axial range A1 does not overlap the first internal teeth 32b when viewed in the radial direction. In order to satisfy this condition, the first fastening member B1 of the present embodiment is disposed on the input side with respect to the first internal teeth 32b.

The first robot member <NUM> includes a first inner step portion 14d capable of positioning the fixing member <NUM> in the axial direction X by coming into contact with the fixing member <NUM> from the input side. The fixing member <NUM> is fixed to the first robot member <NUM> by screwing the first fastening member B1 in the radial direction in a state in which the fixing member <NUM> has come into contact with the first inner step portion 14d of the first robot member <NUM>.

<FIG> will be referred to. The fixing member <NUM> of the present embodiment is provided so as to be non-rotatable relative to the first internal gear <NUM> (first internal tooth member <NUM>) by the second fastening member B2. Although the second fastening member B2 of the present embodiment is a bolt, a specific example thereof is not particularly limited and may be, for example, a rivet (for example, a blind rivet or the like). The second fastening member B2 fastens the first internal gear <NUM> and the fixing member <NUM> in the axial direction X, thereby making the first internal gear <NUM> and the fixing member <NUM> non-rotatable relative to each other. The first internal tooth member <NUM> includes a second female screw hole 46a for screwing the second fastening member B2 in the axial direction. The first internal tooth member <NUM> has a first protrusion portion 46b that protrudes further to the input side than the first internal teeth 32b of the first internal gear <NUM>. The second female screw hole 46a is formed in an axial range including the first protrusion portion 46b. The fixing member <NUM> includes a second counterbored hole 34b that accommodates a head portion of the second fastening member B2. The second counterbored hole 34b is provided at a position that overlaps the axial position of a pressure contact spot <NUM> of the fixing member <NUM> with respect to the first robot member <NUM> in the radial direction. The second counterbored hole 34b is formed as a recessed portion that is recessed from an input-side side surface of the fixing member <NUM> toward the counter-input side.

The fixing member <NUM> has a second protrusion portion 34c that is disposed radially inside the first protrusion portion 46b and protrudes to the counter-input side. The second protrusion portion 34c comes into contact with the external gear <NUM> from the input side and restricts the axial movement of the external gear <NUM>. In order to realize this, the fixing member <NUM> of the present embodiment directly comes into contact with the external gear <NUM> but may come into contact with the external gear <NUM> via a spacer.

<FIG> will be referred to. The main bearing <NUM> is disposed between the bearing housing <NUM> and the synchronization member <NUM>. The bearing housing <NUM> is provided so as to be non-rotatable relative to the first robot member <NUM>, and the synchronization member <NUM> is provided so as to be non-rotatable relative to the second robot member <NUM>. In the main bearing <NUM> of the present embodiment, such bearing housing <NUM> and synchronization member <NUM> are relatively rotatably connected (supported) to each other, thereby relatively rotatably connecting (supporting) the first robot member <NUM> and the second robot member <NUM>.

The main bearing <NUM> of the present embodiment is a cross roller bearing and includes a dedicated outer ring 36b and a dedicated inner ring 36c in addition to the rolling element 36a. A specific example of the main bearing <NUM> is not particularly limited and may be configured to include a plurality of bearings (angular ball bearing, taper bearing) disposed at intervals in the axial direction, in addition to another single bearing such as a ball bearing. The main bearing <NUM> does not include the dedicated outer ring 36b, and an inner peripheral surface of the bearing housing <NUM> may also serve as the main bearing <NUM>. Additionally, the main bearing <NUM> does not include the dedicated inner ring 36c, and an outer peripheral surface of the synchronization member <NUM> may also serve as the inner ring 36c.

The main bearing <NUM> is disposed so as to deviate from the first internal tooth member <NUM> and the second internal tooth member <NUM> in the axial direction X. The main bearing <NUM> is disposed so as to deviate in the axial direction X from a certain axial range of the first internal tooth member <NUM> and the second internal tooth member <NUM>. An inner diameter R36-<NUM> of the main bearing <NUM> is smaller than outer diameters R46 and R47 of the internal tooth members <NUM> and <NUM>. Here, the outer diameters R46 and R47 refer to the largest outer diameter of each of the first internal tooth member <NUM> and the second internal tooth member <NUM>.

Additionally, the "inner diameter" and the "outer diameter" in the present specification both refer to a radius. In a case where a plurality of internal tooth members <NUM> and <NUM> are present as in the present embodiment, this condition has only to be satisfied between any internal tooth members <NUM> and <NUM>. The inner diameter R36-<NUM> of the present embodiment is smaller than both of the outer diameters R46 and R47. The outer diameter R36-<NUM> of the main bearing <NUM> is smaller than the outer diameters R46 and R47 of the internal tooth members <NUM> and <NUM>. In a case where a plurality of internal tooth members <NUM> and <NUM> are present as in the present embodiment, this condition has only to be satisfied between any internal tooth members <NUM> and <NUM>. The outer diameter R36-<NUM> of the present embodiment is smaller than both of the outer diameters R46 and R47. In addition, in the present embodiment, the inner diameter R36-<NUM> is smaller than the inner diameter of a tooth tip circle of each of the first internal tooth member <NUM> and the second internal tooth member <NUM>. Additionally, the outer diameter R36-<NUM> is larger than the inner diameter of the tooth tip circle of each of the first internal tooth member <NUM> and the second internal tooth member <NUM>.

The bearing housing <NUM> is disposed radially outside the main bearing <NUM>. The bearing housing <NUM> of the present embodiment is made of a member separate from the first robot member <NUM>. The first robot member <NUM> of the present embodiment includes a second inner step portion 14e capable of positioning the bearing housing <NUM> in the axial direction by coming into contact with the bearing housing <NUM> from the input side.

The bearing housing <NUM> of the present embodiment is configured by combining a plurality of housing members 38a and 38b. The plurality of housing members 38a and 38b include a first housing member 38a disposed radially outside the main bearing <NUM> and a second housing member 38b disposed radially inside the first housing member 38a. The first housing member 38a is provided with a first movement restricting part 38c that restricts the axial movement of the main bearing <NUM> to the input side by coming into contact with the main bearing <NUM> from the input side. The first movement restricting part 38c of the present embodiment is configured by an inner step portion provided on the first housing member 38a but may be configured by a retaining ring or the like provided on the first housing member 38a. The second housing member 38b is provided with a second movement restricting part 38d that restricts the axial movement of the main bearing <NUM> to the counter-input side by coming into contact with the main bearing <NUM> from the counter-input side. The second movement restricting part 38d of the present embodiment is configured by an inner step portion provided on the second housing member 38b but may be configured by a retaining ring or the like provided on the second housing member 38b. The main bearing <NUM> is positioned in the axial direction with respect to the bearing housing <NUM> by coming into contact with the first movement restricting part 38c and the second movement restricting part 38d of the bearing housing <NUM>.

The bearing housing <NUM> is radially fastened to the first robot member <NUM> by the third fastening member B3. The bearing housing <NUM> is fixed to the first robot member <NUM> by bringing the inner peripheral surface of the first robot member <NUM> and the outer peripheral surface of the bearing housing <NUM> into pressure contact with each other by fastening using the third fastening member B3. Although the third fastening member B3 of the present embodiment is a bolt, a specific example thereof is not particularly limited and may be, for example, a rivet (for example, a blind rivet or the like). The first robot member <NUM> includes a third counterbored hole 14f that is provided on the outer peripheral surface of the first robot member <NUM> to accommodate a head portion of the third fastening member B3. The third counterbored hole 14f is formed as a recessed portion that is recessed radially inward in the first casing 14a of the first robot member <NUM>. The bearing housing <NUM> includes a third female screw hole 38e for screwing the third fastening member B3 in the radial direction. The third female screw hole 38e is formed in the second housing member 38b of the bearing housing <NUM>. An insertion hole 38f having no thread for allowing a shaft portion of the third fastening member B3 to pass therethrough in the radial direction is formed in the first housing member 38a of the bearing housing <NUM>.

An axial range A3 of the third fastening member B3 is assumed.

At least a part of the axial range A3 does not overlap each of the first internal teeth 32b of the first internal gear <NUM> and the second internal teeth 33b of the second internal gear <NUM> when viewed in the radial direction. In the present embodiment, the entire axial range A3 satisfies this condition. In order to satisfy this condition, the third fastening member B3 of the present embodiment is disposed on the counter-input side with respect to the second internal teeth 33b of the second internal gear <NUM>. Both the entire axial range A1 of the first fastening member B1 and the entire axial range A3 of the third fastening member B3 do not overlap the first internal teeth 32b of the first internal gear <NUM> and the second internal teeth 33b of the second internal gear <NUM> when viewed in the radial direction.

The synchronization member <NUM> is disposed on one side (here, the counter-input side) in the axial direction with respect to the external gear <NUM>. The synchronization member <NUM> of the present embodiment includes a first synchronization component 40a disposed on the external gear <NUM> side in the axial direction X, and a second synchronization component 40b provided on a side opposite to the external gear <NUM> in the axial direction with respect to the first synchronization component 40a.

The synchronization member <NUM> is radially fastened to the second robot member <NUM> by a fourth fastening member B4 such as a bolt. A flange portion 40i (described below) of the second synchronization component 40b of the synchronization member <NUM> is provided with a fourth female screw hole 40c for screwing the fourth fastening member B4 in the radial direction. The third casing 16a of the second robot member <NUM> includes a fourth counterbored hole 16b that accommodates a head portion of the fourth fastening member B4. The fourth counterbored hole 16b is formed as a recessed portion that is recessed radially inward in the third casing 16a of the second robot member <NUM>.

The first synchronization component 40a includes a first outer diameter portion 40d that is fastened to a second internal tooth member <NUM> in the axial direction X by a fifth fastening member B5 such as a bolt, and a second outer diameter portion 40e having an outer diameter smaller than that of the first outer diameter portion 40d. The main bearing <NUM> is disposed in the second outer diameter portion 40e. The second outer diameter portion 40e is provided with a stepped shoulder portion 40f that restricts the axial movement of the main bearing <NUM> by coming into contact with the main bearing <NUM> from the axial input side. The second internal tooth member <NUM> includes a fifth female screw hole 47a for screwing the fifth fastening member B5 in the axial direction. The second internal tooth member <NUM> has a third protrusion portion 47b that protrudes further to the counter-input side than the second internal teeth 33b of the second internal tooth member <NUM>. The fifth female screw hole 47a is formed in an axial range including the third protrusion portion 47b.

The first synchronization component 40a has a fourth protrusion portion <NUM> that is disposed radially inside the third protrusion portion 47b and protrudes to the input side. The second internal tooth member <NUM> and the first synchronization component 40a are relatively non-rotatably provided by being fastened to each other in the axial direction X by the fifth fastening member B5 in a state in which the third protrusion portion 47b and the fourth protrusion portion <NUM> are spigot-fitted to each other. The fourth protrusion portion <NUM> comes into contact with the external gear <NUM> from the counter-input side and restricts the axial movement of the external gear <NUM>. In order to realize this, the fourth protrusion portion <NUM> of the present embodiment directly comes into contact with the external gear <NUM> but may come into contact with the external gear <NUM> via a spacer.

The second synchronization component 40b is fastened to the first synchronization component 40a in the axial direction X by screwing a sixth fastening member B6 such as a bolt in the axial direction. The second synchronization component 40b includes a movement restricting part <NUM> that is provided on an input-side side portion of the second synchronization component 40b and protrudes to the input side. The movement restricting part <NUM> of the second synchronization component 40b is spigot-fitted to a counter-input-side end portion of the first synchronization component 40a. The movement restricting part <NUM> of the second synchronization component 40b restricts the axial movement of the main bearing <NUM> by coming into contact with the main bearing <NUM> from the counter-input side in the axial direction X. The second synchronization component 40b includes a flange portion 40i that is provided on a counter-input-side portion of the second synchronization component 40b and overhangs radially outward. The flange portion 40i of the second synchronization component 40b is disposed inside the third casing 16a of the second robot member <NUM>. A fitting portion 16c into which the flange portion 40i of the second synchronization component 40b is spigot-fitted is provided inside the third casing 16a.

In addition, a gear unit <NUM>, which is a combination of the input shaft <NUM>, the internal gears <NUM> and <NUM>, the external gear <NUM>, and the gear bearing <NUM> used in the joint structure <NUM> of the present embodiment, can be handled as a component independent of other elements used in the joint structure <NUM>. A user of the gear unit <NUM> can obtain the joint structure <NUM> by combining the gear unit <NUM> provided by a provider (for example, a manufacturer or a seller) with another element prepared by the user himself/herself separately from the gear unit <NUM>.

The effects of the above joint structure <NUM> will be described.

A radial load F1 caused by fastening using the first fastening member B1 acts on the speed reducer <NUM> in order to bring a part of the speed reducer <NUM> (here, the fixing member <NUM>) and the first robot member <NUM> into pressure contact with each other in the radial direction. In the present embodiment, due to the fastening of the first fastening member B1, a tensile force directed radially outward acts on the fixing member <NUM> serving as each fastened member as the radial load F1 (refer to <FIG>). When the fixing member <NUM> is deformed together with the first internal gear <NUM> including the first internal teeth 32b due to the radial load F1, the meshing between the first internal gear <NUM> and the external gear P <NUM> may be adversely affected.

The bearing housing <NUM> is radially fastened to the first robot member <NUM> by the third fastening member B3. Thus, as compared to a case where the bearing housing <NUM> and the first robot member <NUM> are fastened in the axial direction X, it is not necessary to extend the diameter of the seating surface (bottom surface of the third counterbored hole 14f) for the third fastening member B3 in the first robot member <NUM> in the radial direction. Consequently, the outer diameter of the first robot member <NUM> can be easily reduced around the third fastening member B3.

In fastening the bearing housing <NUM> and the first robot member <NUM> in the radial direction via the third fastening member B3, a radial load F3 acts on the bearing housing <NUM> due to the fastening of the third fastening member B3. In the present embodiment, due to the fastening of the third fastening member B3, a tensile force directed radially outward acts on the bearing housing <NUM> as the radial load F3 (refer to <FIG>). Here, the axial range A3 of the third fastening member B3 does not overlap the second internal teeth 33b of the second internal gear <NUM> when viewed in the radial direction. Thus, as compared to a case where the axial range A3 of the third fastening member B3 overlaps the second internal teeth 33b, it is possible to make it difficult for the radial load F3 acting due to the fastening of the third fastening member B3 to act on the second internal gear <NUM>. Consequently, the second internal gear <NUM> is less likely to be deformed by the radial load F3 caused by the third fastening member B3, and the adverse effect of the radial load F3 on the meshing between the second internal gear <NUM> and the external gear <NUM> can be suppressed.

In order to suppress such an adverse effect on the meshing between the second internal gear <NUM> and the external gear <NUM>, it is more preferable to adopt a configuration described next. The axial range A3 of the third fastening member B3 does not overlap the second internal tooth member <NUM> when viewed in the radial direction. The third fastening member B3 of the present embodiment is disposed on the counter-input side with respect to the second internal tooth member <NUM>. At least a part of the axial range A3 does not overlap the main bearing <NUM> when viewed from the radial direction and is disposed on the counter-input side with respect to the main bearing <NUM>. The entire axial range A3 of the present embodiment is disposed on the counter-input side with respect to the main bearing <NUM>.

The synchronization member <NUM> is radially fastened to the second robot member <NUM> by the fourth fastening member B4. Thus, in the second robot member <NUM>, it is not necessary to extend the seating surface (bottom surface of the fourth counterbored hole 16b) for the fourth fastening member B4 in the radial direction. Consequently, the outer diameter of the second robot member <NUM> can be easily reduced around the fourth fastening member B4.

(E) The inner diameter R36-<NUM> of the main bearing <NUM> is smaller than the outer diameters R46 and R47 of the internal tooth members <NUM> and <NUM>. Thus, compared to a case where the inner diameter R36-<NUM> of the main bearing <NUM> has a size equal to or larger than the outer diameters R46 and R47 of the internal tooth members <NUM> and <NUM>, the outer diameter of the first robot member <NUM> can be easily reduced.

<FIG>, <FIG>, and <FIG> will be referred to. A joint structure <NUM> of the second embodiment is different from the joint structure <NUM> of the first embodiment mainly in terms of the first robot member <NUM>, the second robot member <NUM>, the bearing housing <NUM>, and the synchronization member <NUM>.

The bearing housing <NUM> of the present embodiment also serves as a part of the first robot member <NUM> (here, the first casing 14a) and is integrally made of the same member as a part of the first robot member <NUM>. The bearing housing <NUM> of the present embodiment also includes the same first movement restricting part 38c and second movement restricting part 38d as those of the first embodiment and positions the main bearing <NUM> in the axial direction X.

The synchronization member <NUM> of the present embodiment includes only the first synchronization component 40a out of the first synchronization component 40a and the second synchronization component 40b and does not include the second synchronization component 40b. The second robot member <NUM> is fastened to the synchronization member <NUM> by the sixth fastening member B6 and includes the same movement restricting part <NUM> as the second synchronization component 40b.

The first robot member <NUM> includes a plurality of (two in the present embodiment) divided portions <NUM> obtained by dividing a part (here, the first casing 14a) of the first robot member <NUM> in the circumferential direction. As a whole, the plurality of divided portions <NUM> form a tubular cross section in a cross section perpendicular to the axial direction X. The adjacent divided portions <NUM> are provided at circumferential end portions of the individual divided portions <NUM> and include butted end portions 80a that are butted against each other. The plurality of divided portions <NUM> are fastened in the circumferential direction (tangential direction) by the first fastening member B1 disposed on the input side and the third fastening member B3 disposed on the counter-input side.

The first fastening member B1 of the present embodiment fastens the plurality of divided portions <NUM> as the plurality of fastened members in the circumferential direction, thereby bringing a part (here, the first casing 14a) of the first robot member <NUM> configured by the plurality of divided portions <NUM> into pressure contact with the fixing member <NUM>. The expression "fastening in the circumferential direction" herein means fastening the plurality of divided portions <NUM> by applying a fastening force in the tangential direction on the outer peripheral surface of the first robot member <NUM>. The fixing member <NUM> is fixed to the first robot member <NUM> by the friction applied to the pressure contact spot <NUM> with the first robot member <NUM> due to the fastening force of the first fastening member B1. The first fastening member B1 is individually used for each of the butted end portions 80a on both sides of the divided portion <NUM> in the circumferential direction and fastens the butted end portions 80a of the adjacent divided portions <NUM>.

At least a part of the axial range A1 of the first fastening member B1 is disposed at a position not overlapping the fixing member <NUM> when viewed in the radial direction. In order to satisfy this condition, at least a part of the first fastening member B1 is disposed on a side (input side) opposite to the first internal gear <NUM> in the axial direction X with respect to the fixing member <NUM>. At least a part of the axial range A1 of the first fastening member B1 of the present embodiment is disposed on the input side with respect to the first inner step portion 14d of the first robot member <NUM>.

The third fastening member B3 of the present embodiment fastens the plurality of divided portions <NUM> in the circumferential direction, thereby bringing a part (here, the first casing 14a) of the first robot member <NUM> serving as the bearing housing <NUM> and constituted by the plurality of divided portions <NUM> into pressure contact with the main bearing <NUM>. Similarly to the first fastening member B1, the third fastening member B3 is also individually used for each of the butted end portions 80a on both sides of the divided portion <NUM> in the circumferential direction and fastens the butted end portions 80a of the adjacent divided portions <NUM>.

The axial range A3 of the third fastening member B3 is assumed. The axial range A3 of the third fastening member B3 has the same features as those of the axial range A3 of the third fastening member B3 of the first embodiment. For example, at least a part of the axial range A3 of the third fastening member B3 does not overlap each of the first internal teeth 32b of the first internal gear <NUM> and the second internal teeth 33b of the second internal gear <NUM> when viewed in the radial direction.

The first fastening member B1 and the third fastening member B3 of the present embodiment include a bolt <NUM> and a nut <NUM>. The bolt <NUM> is inserted through insertion holes 80b provided in the butted end portions 80a of the adjacent divided portions <NUM>. The outer peripheral surface of the first robot member <NUM> includes the first counterbored hole 14c that accommodates each of a head portion of the bolt <NUM> and the nut <NUM>.

In the present embodiment, due to the fastening of the first fastening member B1, a load directed radially inward from each divided portion <NUM> serving as the fastened member to the fixing member <NUM> acts as the radial load F1 (refer to <FIG>). As mentioned above, at least a part of the axial range A1 of the first fastening member B1 does not overlap the first internal teeth 32b of the first internal gear <NUM> when viewed in the radial direction. Thus, as mentioned above, it is possible to make it difficult for the radial load F1 caused by the first fastening member B1 to act on the first internal gear <NUM>. Consequently, even in a case where the plurality of divided portions <NUM> are fastened in the circumferential direction, an adverse effect on the meshing between the first internal gear <NUM> and the external gear <NUM> caused by the radial load can be suppressed similarly to the above-mentioned (A).

Additionally, due to the fastening of the third fastening member B3, a load directed radially inward from the divided portion <NUM> to the main bearing <NUM> acts as a radial load (not shown). Here, the axial range A3 of the third fastening member B3 does not overlap the second internal teeth 33b of the second internal gear <NUM> when viewed in the radial direction. Thus, as compared to a case where the axial range A3 of the third fastening member B3 overlaps the second internal teeth 33b, it is possible to make it difficult for a radial load acting due to the fastening of the third fastening member B3 to acts on the second internal gear <NUM>.

In addition to this, the joint structure <NUM> of the present embodiment includes the components (not shown) described in the above-mentioned (B) to (E), and the effects corresponding to the description can be obtained.

Next, modifications of the respective components described so far will be described.

Although an example has been described in which the speed reducer <NUM> is a bending meshing type speed reducer, the type of the speed reducer <NUM> is not limited thereto. For example, the speed reducer <NUM> may be an eccentric oscillation type speed reducer that uses a crankshaft as an input shaft. In this case, a center crank type in which a crankshaft is disposed on the center of an internal gear may be adopted, or a sorting type in which a plurality of crankshafts are disposed at positions offset from the center of the internal gear may be adopted. In this case, the number of internal gears may be one. Additionally, in the case of the bending meshing type speed reducer, a tubular type including the two internal gears <NUM> and <NUM> has been described as a specific example thereof, but the type thereof is not limited thereto. For example, a cup type or a silk hat type including one internal gear may be adopted. Additionally, the type of the speed reducer <NUM> may be a simple planetary gear device.

In the embodiments, an example has been described in which the first robot member <NUM> serves as a support member and the second robot member <NUM> serves as a driven member. In addition to this, the first robot member <NUM> may be a driven member, and the second robot member <NUM> may be a support member. In this case, when the tubular bending meshing type speed reducer is used, the first internal gear <NUM> may be a drive-side internal gear that drives the first robot member <NUM> serving as a driven member, and the second internal gear <NUM> may be a stationary-side internal gear fixed to the second robot member <NUM> serving as a support member.

In the case of the eccentric oscillation type speed reducer, the gear drive unit 28a of the input shaft <NUM> may be an eccentric body driven by oscillating the external gear <NUM>. In this case, the synchronization member <NUM> may be a carrier that is disposed on one side in the axial direction with respect to the external gear <NUM> and is synchronizable with the axial rotation component of the external gear <NUM> by a pin that penetrates the external gear <NUM>.

The fixing member <NUM> has only to be fixed to the first robot member <NUM> by bringing the first robot member <NUM> and the fixing member <NUM> into pressure contact with each other in the radial direction by fastening using the first fastening member B1, and a specific structure therefore is not limited to the contents of the embodiments. The fixing member <NUM> may be integrally made of the same member as that of the internal gear <NUM>. The Young's modulus of the fixing member <NUM> may be equal to or lower than the Young's modulus of the internal gear <NUM>.

At least a part of the axial range A1 of the first fastening member B1 has only not to overlap the internal teeth 32b of the internal gear <NUM> when viewed in the radial direction, and a part thereof may not overlap the internal teeth 32b of the internal gear <NUM>.

The means for relatively non-rotatably providing the internal gear <NUM> and the fixing member <NUM> is not limited to the second fastening member B2. In order to realize this, for example, fitting of a spline, a key, or the like may be used.

The means for relatively non-rotatably providing the bearing housing <NUM> and the first robot member <NUM> is not limited to the third fastening member B3. In order to realize this, for example, fitting of a spline, a key, or the like may be used. Additionally, the bearing housing <NUM> may be fastened to the first robot member <NUM> in the axial direction X by the third fastening member B3.

An example in which the bearing housing <NUM> is configured by combining a plurality of housing members 38a and 38b has been described. However, the bearing housing <NUM> may be configured by a single member. Also in this case, the bearing housing <NUM> may include the plurality of movement restricting parts <NUM>.

The third fastening member B3 may overlap any one of the first internal teeth 32b of the first internal gear <NUM> and the second internal teeth 33b of the second internal gear <NUM> when viewed in the radial direction.

In providing the synchronization member <NUM> so as to be non-rotatable relative to the second robot member <NUM>, specific means thereof is not particularly limited. In order to realize this, for example, fitting of a spline, a key, or the like may be used.

The main bearing <NUM> may be disposed at a position that does not deviate from the internal tooth members <NUM> and <NUM> in the axial directionX, that is, at a position that overlaps the internal tooth members <NUM> and <NUM> when viewed from the radial direction. In this case, the inner diameter R36-<NUM> of the main bearing <NUM> may have a size equal to or larger than the outer diameters R46 and R47 of the internal tooth members <NUM> and <NUM>.

The above embodiment and modifications are exemplary. The technical ideas in which these are abstracted should not be interpreted as being limited to the contents of the embodiments and modifications. Many design changes such as changes, additions, and deletions of components are possible for the contents of the embodiments and modifications. In the above-mentioned embodiments, the contents that allow such design changes are emphasized with the notation "embodiment". However, the design changes are allowed even in the contents with no such notation. The hatching given to the cross sections of the drawings does not limit the material of a hatched object. Structures referred to in the embodiments and modifications naturally include those that can be regarded as the same when manufacturing errors are taken into consideration.

Claim 1:
A robot joint structure (<NUM>) comprising:
a first robot member (<NUM>);
a second robot member (<NUM>); and
a speed reducer (<NUM>) incorporated in a joint portion (<NUM>) that connects the first robot member (<NUM>) and the second robot member (<NUM>) to each other,
characterized in that the speed reducer (<NUM>) includes an external gear (<NUM>), an internal gear (<NUM>) that meshes with the external gear (<NUM>), a fixing member (<NUM>) that is provided so as to be non-rotatable relative to the internal gear (<NUM>) and is disposed on an input side in an axial direction (X) with respect to the internal gear (<NUM>),
the fixing member (<NUM>) is fixed to the first robot member (<NUM>) by bringing an inner peripheral surface of the first robot member (<NUM>) and an outer peripheral surface of the fixing member (<NUM>) into pressure contact with each other by fastening using a first fastening member (B1), and
at least a part of an axial range (A1) of the first fastening member (B1) does not overlap internal teeth (32b) of the internal gear (<NUM>) when viewed in a radial direction.