ROBOT

A robot includes a base. A turnable portion is mounted on the base and turnable about a first axis approximately perpendicular to an installation surface on which the base is disposed. An arm is mounted on the turnable portion and swingable about a second axis parallel to the installation surface. A first motor is accommodated in the turnable portion and moves the turnable portion about the first axis. A first motor includes a body and a protrusion. The body has an axial dimension that is in a direction along an output shaft of the first motor and that is smaller than a perpendicular dimension in a direction approximately perpendicular to the output shaft. The protrusion protrudes from a surface of the body in a direction along the output shaft and is displaced from the output shaft. A second motor moves the arm about the second axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2015-015706, filed Jan. 29, 2015. The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND

1. Field of the Invention

The embodiments disclosed herein relate to a robot.

2. Discussion of the Background

Japanese Unexamined Patent Application Publication No. 2003-200376 discloses an industrial robot that includes a base, a turnable base, a lower arm, and an upper arm. The turnable base turns about an S axis relative to the base. The lower arm swings about an L axis relative to the turnable base. The upper arm swings about a U axis relative to the lower arm. The lower arm operates by a motor that is coaxial with the L axis, and the upper arm operates by a motor that is coaxial with the U axis. The turnable base operates by a motor that is coaxial with the S axis. The lower arm operates by a motor that is coaxial with the L axis. The upper arm operates by a motor that is coaxial with the U axis.

SUMMARY

According to one aspect of the present disclosure, a robot includes a base, a turnable portion, an arm, a first motor, and a second motor. The turnable portion is mounted on the base and turnable about a first axis approximately perpendicular to an installation surface on which the base is disposed. The arm is mounted on the turnable portion and swingable about a second axis parallel to the installation surface. The first motor is accommodated in the turnable portion and configured to move the turnable portion about the first axis relative to the base. The first motor includes a body and a protrusion. The body includes an axial dimension in a direction along an output shaft of the first motor and a perpendicular dimension in a direction approximately perpendicular to the output shaft of the first motor. The axial dimension is smaller than the perpendicular dimension. The protrusion protrudes from a first surface of the body in a direction along the output shaft of the first motor and is disposed at a position displaced from the output shaft of the first motor. The second motor is configured to move the arm about the second axis relative to the turnable portion.

DESCRIPTION OF THE EMBODIMENTS

Configuration of Robot

FIG. 1is a perspective view of a robot according to this embodiment.FIG. 2is a side view of the robot illustrated inFIG. 1.FIG. 3is a rear view of the robot illustrated inFIG. 1. The robot,1, illustrated in the drawings is an industrial robot that works on workpieces, not illustrated.

As illustrated inFIGS. 1 to 3, the robot1includes a base3, a turnable portion5, a first arm7, a second arm9, and an end base11. The base3, the turnable portion5, the first arm7, the second arm9, and the end base11are coupled to each other in this order from the base end of the robot1to the distal end of the robot1.

The base3is fixed to an installation surface and supports the entire robot1.

The turnable portion5is disposed on the base3. The turnable portion5is turnable about a turning axis, namely, a first axis Ax1, which extends in the vertical direction, relative to the base3. The turnable portion5is driven into turning operation about the first axis Axl by a power source, namely, a first motor, which is accommodated in the turnable portion5. The first axis Ax1will be occasionally referred to as “S axis”.

The first arm7is swingable about a swing axis, namely, a second axis Ax2relative to the turnable portion5. The second axis Ax2passes through a connection portion6(the end of the first arm7on the side of the turnable portion5), at which the turnable portion5and the first arm7are coupled to each other. The connection portion6, at which the turnable portion5and the first arm7are coupled to each other, is equipped with a second motor.

The first arm7is driven by a power source, namely, the second motor, which is parallel to the installation surface, into swing operation about the second axis Ax2. Specifically, as illustrated inFIG. 6, the first arm7is swingable in a first direction D1(frontward) up to a first swing angle θ1relative to a reference line LS. The reference line LS is in a direction approximately perpendicular to the installation surface and passes through the second axis Ax2. The first arm7is also swingable relative to the reference line LS in a second direction D2(rearward), which is opposite to the first direction D1, up to a second swing angle θ2. The second swing angle θ2is smaller than the first swing angle θ1(θ1>θ2). In a view from a direction along the second axis Ax2, the first axis Ax1is disposed at a position that is further in the second direction D2than the reference line LS. The second axis Ax2will be occasionally referred to as “L axis”.

The second arm9includes a base end9aand a distal end9b.The base end9ais on the side of the first arm7, and the distal end9bis on the side of the end base11. The base end9ais swingable about a swing axis, namely, a third axis Ax3relative to the first arm7. The third axis Ax3passes through a connection portion10(the end of the first arm7on the side of the base end9a), at which the first arm7and the second arm9are coupled to each other. This configuration makes the second arm9as a whole swingable about the third axis Ax3relative to the first arm7. The connection portion10, at which the first arm7and the second arm9are coupled to each other, is equipped with a third motor. The second arm9(base end9a) is driven by a power source, namely, the third motor, into swing operation about the third axis Ax3. The third axis Ax3extends in parallel to the second axis Ax2. The third axis Ax3will be occasionally referred to as “U axis”.

The distal end9bis turnable about a turning axis, namely, a fourth axis Ax4, relative to the base end9a.The fourth axis Ax4passes through the center of the second arm9. The distal end9bis driven by a power source, namely, a fourth motor, into turning operation about the fourth axis Ax4. The fourth axis Ax4will be occasionally referred to as “R axis”.

The end base11includes a base end11aand a distal end11b.The base end11ais on the side of the second arm9, and the distal end11bis on the side of the distal end of the robot1. The base end11a is swingable about a swing axis, namely, a fifth axis Ax5relative to the distal end9b.The fifth axis Ax5passes through a connection portion at which the second arm9(distal end9b) and the end base11(base end11a) are coupled to each other. The base end11ais driven by a power source, namely, a fifth motor, into swing movement about the fifth axis Ax5. The fifth axis Ax5will be occasionally referred to as “B axis”.

The distal end11bis mounted on the base end11ain a rotatable manner about a rotation axis, namely, a sixth axis Ax6, relative to the base end11a. The sixth axis Ax6passes through the center of the end base11. The distal end11bis driven by a power source, namely, a sixth motor, into rotational movement about the sixth axis Ax6. The sixth axis Ax6will be occasionally referred to as “T axis”. An end effector is attachable to the end base11. A non-limiting example of the end effector is a welding torch.

Configurations of Motors

Next, the first to sixth motors provided in the robot1will be described in detail. The first to sixth motors have similar configurations and may hereinafter occasionally be referred to as “motor20” collectively.FIG. 4is a perspective view of the motor illustrating an external appearance of the motor20.FIG. 5is a cross-sectional view of the motor20. As illustrated inFIGS. 4 and 5, the motor20includes a casing (body)30, a rotor40, a stator50, an encoder60, and a brake (protrusion)70.

The casing30holds elements such as the rotor40, the stator50, and the encoder60. In this embodiment, the casing30has a circular outer shape. The casing30includes a first surface30a(second surface), a second surface (first surface)30b,and a third surface30c. The first surface30aand the second surface30bare orthogonal to the output shaft, Ax, of the motor20. The third surface30chas a circular shape extending along the output shaft Ax. The casing30has an axial dimension in a direction along the output shaft Ax of the motor20and a perpendicular dimension in direction approximately perpendicular to the output shaft Ax. The axial dimension is smaller than the perpendicular dimension. Specifically, the casing30has such a flat shape that dimension L1, which is between the first surface30aand the second surface30b,is smaller than dimension L2, which is the diameter of the third surface30c(L1<L2). In this embodiment, the dimension L1is equal to or less than half the dimension L2.

The rotor40includes a rotator42and a brake pad44. The rotator42is a member that can be driven into rotation about the output shaft Ax. The rotator42is rotatable by ring-shaped bearings46aand46b,which are fixed to the casing30. The bearings46aand46bare aligned in a direction along the output shaft Ax with a predetermined distance between the bearings46aand46b.On the outer surface of the rotor40, magnets48are aligned in the circumferential direction. The rotator42includes a shaft member43. The shaft member43protrudes from the first surface30aof the casing30.

The brake pad44is a member that performs braking operation as controlled by the brake70. The brake pad44is disposed over the circumference of the rotator42. The brake pad44has a ring shape. The brake pad44is coaxial with the output shaft Ax. The outer edge of the brake pad44is further outward than the outer edge of the rotator42. That is, the outer diameter of the brake pad44is larger than the outer diameter of the rotator42. In this embodiment, the brake pad44is made of metal.

The stator50is a member that imparts rotational force to the rotor40. The stator50includes a core52and a coil54. In this embodiment, the core52has a ring shape. The core52faces the outer surface of the rotator42. The coil54is disposed on the core52.

The encoder60is a rotation detector that detects the rotation of the rotor40. A non-limiting example of the encoder60is a rotary encoder capable of detecting amounts by which the motor20is driven, such as the number of rotations of the rotor40, the rotational angle of the rotor40, and/or the rotational speed of the rotor40. The encoder60is partially disposed in a depression42aof the rotator42.

The brake70is a braking device that causes the rotating rotor40to brake. The brake70protrudes outward from the second surface30bof the casing30along the output shaft Ax. The brake70is decentered from the output shaft Ax. The brake70includes a case72, a friction material74, a holding member76, a biasing member78, and a coil79.

The case72accommodates the holding member76, the biasing member78, and the coil79. In this embodiment, the case72is fixed to the casing30with a screw. In the embodiment illustrated inFIG. 4, the case72has a solid cylindrical outer shape. The case72may be designed into any convenient shape.

The friction material74comes into sliding contact with the brake pad44of the rotor40to impart frictional force to the brake pad44. The friction material74is disposed on the holding member76. Examples of the material of the friction material74include, but are not limited to, resin mold, semi-metallic material, and sintered alloy (of iron and/or copper).

The holding member76holds the friction material74. In this embodiment, the holding member76is made of metal. The holding member76has an approximately T shape. The holding member76includes a body76aand a holder76b.

In this embodiment, the body76ahas a solid cylindrical shape. The body76aextends in the direction along the output shaft Ax. In this embodiment, the holder76bhas a disc shape. The holder76bis disposed on one end (the end closer to the brake pad44) of the body76a.The outer diameter of the holder76bis larger than the outer diameter of the body76a.The holder76bfaces the brake pad44of the rotor40. That is, the friction material74faces the brake pad44.

The holding member76is movable (sliding-movable) in the direction along the output shaft Ax. Specifically, the holding member76is movable between a first position (initial position) and a second position. At the first position, the holder76bcontacts the coil79. At the second position, the friction material74sliding-contacts the brake pad44.

The biasing member78biases the holding member76. In this embodiment, the biasing member78is a coil spring. The biasing member78is disposed on the other end of the body76aof the holding member76. When the holding member76is at the first position, the biasing member78biases the holding member76toward the rotor40.

The coil79regulates the movement of the holding member76. The coil79surrounds the body76aof the holding member76. When current is supplied through the coil79, the coil79effects electromagnetic force against the biasing force of the biasing member78to pull the holder76band holds the holding member76at the first position. When no current is supplied through the coil79, the coil79releases the holding member76.

When supply of current through the coil79is discontinued, the brake70with the above-described configuration causes the coil79to release the holding member76, and allows the biasing force of the biasing member78to move the holding member76toward the rotor40. That is, the brake70positions the holding member76at the second position. Then, the brake70causes the friction material74to sliding-contact the brake pad44to impart frictional force to the brake pad44. This configuration causes the rotating rotor40to decelerate or stop and prevents the stationary rotor40from rotating.

When current is supplied through the coil79, the brake70causes the coil79to pull the holding member76to separate the friction material74and the brake pad44from each other. That is, the brake70positions the holding member76at the first position. This configuration makes the rotor40rotatable.

Motor Arrangement

Next, arrangement of the motor20(first motor) with the above-described configuration will be described.FIG. 6illustrates an internal configuration of the base3and the turnable portion5.FIG. 7illustrates where the motor20is arranged.

As illustrated inFIG. 6, the first motor20is accommodated in the turnable portion5and is fixed to the turnable portion5. Specifically, the first motor20is arranged with the first surface30aof the casing30facing the installation surface. Specifically, the motor20is disposed in the turnable portion5with the brake70facing upward. The first motor20is fixed to the tamable portion5with the output shaft Ax of the first motor20coaxial with the first axis Axl. This configuration makes the first motor20rotatable together with the turnable portion5. The brake70of the first motor20is disposed on the casing30and between the first axis Ax1and the reference line LS. More specifically, the brake70is on a line that connects the first axis Ax1and the reference line LS to each other.

The first motor20is coupled to a reducer15. The reducer15is disposed in the base3and is fixed to the base3. The input shaft of the reducer15is coaxial with the output shaft Ax of the first motor20. Specifically, the output shaft Ax of the first motor20and the input shaft of the reducer15are coaxial with the first axis Ax1.

Advantageous Effects

As has been described hereinbefore, in the robot1according to this embodiment, the casing30of the motor20has a smaller axial dimension, which is in the direction along the output shaft Ax, than the perpendicular dimension of the casing30in the direction approximately perpendicular to the output shaft Ax. That is, the casing30has a flat shape. The brake70is disposed at a position displaced from the output shaft Ax. Thus, the motor20has a flat casing30and a brake70offset from the output shaft Ax, and the motor20is disposed with its output shaft Ax parallel to the first axis Ax1. This configuration decreases the dimension of the motor20motor20in the direction along the first axis Ax1of the turnable portion5, which accommodates the motor20(that is, the height dimension of the motor20). This configuration avoids contact between the first arm7and the turnable portion5and increases the second swing angle θ2of the first arm7. This, as a result, widens the movable range of the robot while preventing an increase in size of the apparatus.

In this embodiment, the first motor20is fixed to the turnable portion5and is rotatable together with the turnable portion5. This configuration keeps the position relationship between the first motor20and the turnable portion5unchanged even while the turnable portion5is turning. This eliminates or minimizes complications in the turnable portion5, such as wiring of the cables.

In this embodiment, the output shaft Ax of the first motor20is coaxial with the first axis Ax1, and the second surface30bof the casing30, which is opposite to the first surface30a,faces the installation surface. The first arm7is swingable in the first direction D1up to the first swing angle θ1relative to the reference line LS, which is in the direction approximately perpendicular to the installation surface and which passes through the second axis Ax2. The first arm7is also swingable relative to the reference line LS in the second direction D2, which is opposite to the first direction D1, up to the second swing angle θ2. In a view from the direction along the second axis Ax2, the first axis Ax1is disposed at a position that is further in the second direction D2than the reference line LS. The brake70of the first motor20is disposed on the casing30and between the first axis Ax1and the reference line LS. Thus, the brake70is disposed on the side of the first arm7. This configuration involves increasing the height dimension of the turnable portion5, which accommodates the first motor20, only at a portion that is on the side of the first aim7in accordance with the brake70. That is, it is not necessary to increase the height dimensions of portions of the turnable portion5that are further away from the first arm7. This configuration avoids contact between the first arm7and the turnable portion5while the first arm7is swinging in the second direction D2, and thus increases the second swing angle θ2. This, as a result, widens the movable range of the robot.

In this embodiment, the robot1includes the reducer15. The reducer15is coupled to the first motor20and has an input shaft coaxial with the output shaft Ax. The reducer15is fixed to the base3. This configuration eliminates or minimizes an increase in size of the turnable portion5and the base3in the width direction. This, as a result, minimizes the interference radius of the turnable portion5while the turnable portion5is turning.

The above-described embodiment should not be construed in a limiting sense. For example, while the above-described embodiment has been described as including the first arm7and the second arm9, an additional arm may be coupled to the second arm9.

While in the above-described embodiment the motor20has been described as having the configuration illustrated inFIG. 5, this configuration of the motor20should not be construed in a limiting sense.