JP6749539B2 - Robot hand - Google Patents

Description

TECHNICAL FIELD The present invention relates to a multi-fingered and multi-jointed robot hand capable of gripping and manipulating an object.

Conventionally, various robot hands for the purpose of gripping and moving an object have been developed, and are used in large numbers for automation and labor saving mainly in production lines of various factories. In recent years, this robot hand is applicable to artificial hands, humanoid robots, and the like, and it is desired that the robot hand be more versatile, complex, and capable of highly accurate motion.

For example, Patent Document 1 includes a plurality of actuators that serve as drive sources for a plurality of joint parts, and drives the joints by decelerating the output of each actuator with a Harmonic Drive (registered trademark) speed reducer or a planetary gear speed reducer. According to the structure, a finger structure of a robot hand is disclosed, which can be controlled with high precision and can manipulate an object dexterously.

Japanese Patent No. 4469957

In the robot hand of Patent Document 1, a plurality of actuators and a HarmonicDrive (registered trademark) reduction gear corresponding to the actuators are arranged on the finger structure itself to realize a driving operation of a finger joint with less backlash and backlash. doing.

However, when a large force is applied to the finger part from the outside while the robot hand is not moving, the position of the finger cannot be held and the robot moves, or when a strong impact force is applied. There is also a risk that the mechanism of the speed reducer will be destroyed.

In particular, when it is used for a versatile prosthetic hand, a humanoid robot, or the like, an unexpected load may be applied from the outside.

In addition, even if the amount is small, there is a possibility that the gripping state cannot be maintained when the energy supply to the drive source of the robot hand that is gripping an object is stopped, even if the joint has backlash or backlash.

The present invention has been made to deal with these problems, and its problem is to incorporate a clutch mechanism capable of interrupting the load from the output side to cut off the energy supply to the drive source. However, the object is to provide a robot hand having stability and high reliability for holding the position of the finger portion.

A robot hand according to the present invention includes a motor that serves as a drive source for a finger joint and a rotational force transmission device that transmits the rotation of the motor as input torque from the input side to the output side. Then, the rotational force transmission device includes a clutch mechanism that transmits the input torque applied to the input side to the output side, but does not transmit the reverse input torque applied to the output side to the input side, and a gear mechanism including a plurality of gears. It is characterized by being configured.

In the present invention having such characteristics, the internal mechanism is protected from the load applied from the outside, and even if the drive source is stopped by cutting off the energy supply to the drive source, it is extremely reliable to maintain the current state of the finger position. Realize a robot hand with high efficiency and energy saving.

It is a perspective view showing an example of a robot hand concerning an embodiment of the present invention. FIG. 3 is a structural diagram of a robot hand according to the embodiment of the present invention. It is a figure which shows an example of the rotational force transmission device arrange|positioned at the robot hand which concerns on embodiment of this invention. It is a structural diagram showing an example of a clutch mechanism provided in the same torque transmission device. It is a sectional side view which shows the structure of the same clutch mechanism. It is an operation explanatory view of a clutch mechanism provided in a torque transmitting device arranged in a robot hand according to the present invention. It is a schematic diagram which shows the relationship between the storage chamber inner peripheral surface, an engagement element, and a cam surface. It is a schematic diagram which shows the relationship between an engagement element and an output rotary body. It is a figure which shows the other example of the robot hand which concerns on embodiment of this invention.

In a first embodiment for carrying out the present invention, in a robot hand having a plurality of fingers, a motor serving as a drive source of a finger joint and a rotation for transmitting the rotation of the motor as an input torque from an input side to an output side. And a force transmission device. The torque transmitting device is composed of a clutch mechanism that transmits the input torque applied to the input side to the output side, but does not transmit the reverse input torque applied to the output side to the input side, and a gear mechanism including a plurality of gears. doing.
According to this aspect, even if an external load is applied to the output side, the clutch mechanism does not transmit the force to the input side, so that the state of the position of the finger of the robot hand can be maintained and the internal mechanism can be protected. You can

Further, in the second mode, the clutch mechanism of the first mode is structurally a storage chamber having a cylindrical space, an output rotary member coaxially stored in the storage chamber, and a coaxial output shaft. An input rotor provided in the housing, an engagement member provided between the inner peripheral surface of the storage chamber and the outer peripheral surface of the output rotor, and a biasing member for biasing the engagement member to one side in the circumferential direction. Prepare Then, a cam surface is formed on the outer peripheral surface of the output rotary member to gradually narrow the gap between the output rotary member and the inner peripheral surface of the storage chamber, and when the input rotary member rotates to the other side with respect to the one side, After the rotor is brought into contact with the engaging element, the input rotor is brought into contact with the output rotor to push the output rotor.
According to this aspect, even if the drive source is stopped, the current state of the robot hand can be maintained, and thus absolute gripping reliability is provided. More specifically, for example, when the motor serving as the drive source is electric, the gripping state can be maintained even if the power is intentionally or unintentionally cut off while the robot hand is gripping the object. .. Further, this enables low power consumption driving.

Further, in the third mode, in the first or second mode, each of the plurality of fingers of the robot hand has one or more joints, and a motor that drives the joints with respect to one joint. One or more combinations of the above and the torque transmission device are arranged.
According to this aspect, since all the fingers are provided with the clutch mechanism, even when the drive source is stopped, it is possible to more reliably maintain the state of gripping the target object in a more stable state.

Further, in the fourth mode, in order to hold the finger position with higher accuracy, the clutch mechanism configured in the first to third modes is arranged on the output side of the gear mechanism.

Next, a particularly preferred embodiment of the above-described mode will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing the appearance of a robot hand 200 in this embodiment. The robot hand 200 includes fingers 220, 230, 240 connected to a base 210. Each finger has a plurality of links and joints. For example, the finger 240 has a first link 241, a second link 242, a first joint 243, and a second joint 244.

Each joint operates by the force of an independent drive source being transmitted via a transmission device. Further, basically, the transmission device is not affected by an external load. This structure will be specifically described below by operating the first joint 243 and the first link 241 of the finger 240.

FIG. 2 is a partial cross-sectional view of the finger 240, and particularly shows the internal structure of the second link 242. Inside the second link 242, an electric motor 60 and a torque transmission device 100 including the clutch mechanism 1 and the gear mechanism 2 are arranged.

The rotational force of the electric motor 60 is transmitted to the first joint 243 via the rotational force transmission device to operate the first joint 243 and the first link 241.

The clutch mechanism 1 transmits the rotational force of the electric motor 60 transmitted via the gear mechanism 2 to the first joint 243 to operate the first link 241, but even if a load is applied from the first link 241 side, No force is transmitted to the gear mechanism 2.

That is, even when the electric motor 60 is not energized, even if a load is applied to the first link 241 that is the fingertip of the finger 240 from the outside, the first link 241 does not move and maintains its position. Therefore, the clutch mechanism 1 functions as a lock mechanism against an external load.

In order to operate each joint, the base 210 that constitutes the robot hand 200 and each finger connected to this base 210 correspond to each joint similarly to the internal structure of the second link 242 that drives the first joint 243. The electric motor and the torque transmission device are incorporated.

FIG. 3 is an enlarged view of a portion of the torque transmission device 100 inside the second link 242. In the rotational force transmission device 100, only the portion of the retainer 80, which is also the exterior part of the rotational force transmission device, is shown in cross section in order to show the structure.
As shown in FIG. 3, the rotational force transmission device 100 axially connects the clutch mechanism 1 and the gear mechanism 2 in the retainer 80.

The cage 80 includes an upper plate 81a, a lower plate 81b, columns 83a and 83b, a housing 84, and a bearing 85.
Inside the cage 80, the fixing member 10 of the clutch mechanism 1 is fixedly arranged on the upper plate 81a.
Further, inside the cage 80, the multi-stage gear 71 that constitutes the gear mechanism 2 is rotatably held around the column 83a. Further, the multi-stage gear 72 which also constitutes the gear mechanism 2 is rotatably held around the column 83b.

The rotational force of the rotary shaft 61 that uses the electric motor 60 as a drive source is transmitted when the pinion gear 62 fixed to the rotary shaft 61 rotates while meshing with the large gear portion 71a of the multistage gear 71.
At the same time, the small gear portion 71b of the multistage gear 71 meshes with the large gear portion 72a of the multistage gear 72 to transmit the rotational force.
Then, the small gear portion 72 b of the multi-stage gear 72 meshes with the gear 34 fixed to the input side shaft portion 33 of the clutch mechanism 1 to transmit the rotational force to the clutch mechanism 1.

That is, a series of torque transmission mechanisms using the gear mechanism 2 constitutes a so-called spur reduction gear.
The rotational force transmitted to the input side shaft portion 33 of the clutch mechanism 1 via the gear 34 is output from the output shaft 24 supported by the bearing 85.

The output shaft 24 is connected to a part of the first joint 243, and operates the first joint 243 and the first link 241 held by the first joint 243.

Next, the structure of the clutch mechanism 1 will be described with reference to FIGS. 4 to 10.
The clutch mechanism 1 is shown in FIG. 4 which is a sectional view taken along the line (I)-(I) of FIG. 5 and in FIG. 5 which is a side sectional view of the clutch mechanism 1 seen from the direction of the line (II)-(II) in FIG. As described above, the fixed member 10 forming the storage chamber 11 having the cylindrical space, the output rotary body 20 coaxially stored in the storage chamber 11, and the input rotary body provided coaxially with the output rotary body 20. 30, a pair of engaging elements 41, 42 provided between the inner peripheral surface 11a of the storage chamber and the outer peripheral surface of the output rotating body 20, and one engaging element 41 on one side in the circumferential direction (according to FIG. And a biasing member 50 that biases the other engaging element 42 to the other side in the circumferential direction (counterclockwise side in FIG. 4).

The clutch mechanism 1 rotates when the input rotary body 30 receives a rotational force from the small gear portion 72b of the multistage gear 72 that meshes with the gear 34 fixed to the shaft portion 33 of the input rotary body 30. The force is transmitted to the output rotary body 20 to rotate the output rotary body 20, and when a rotational force is applied to the output rotary body 20 from the outside, the output rotary body 20 is locked so as not to rotate.

The fixing member 10 has a storage chamber 11 therein for storing the output rotary body 20, the engaging elements 41 and 42, and the biasing member 50. The storage chamber 11 secures a substantially columnar space surrounded by the inner peripheral surface 11a. The inner peripheral surface 11a is a curved surface of a cylindrical inner peripheral surface having no irregularities.

The fixing member 10 is non-rotatably fixed to the upper plate 81a of the retainer 80.
As a method of this fixing, in the fixing member 10 shown in FIG. 3, at least a part of the thickness portion 11t from the wall of the surface perpendicular to the axial direction of the storage chamber 11 to the axial output side is the upper plate 81a. Screwing, welding, etc. to.

The output rotator 20 is a substantially disk-shaped member arranged concentrically in the storage chamber 11, and its center side is rotatably supported by the fixed member 10. The axially one end side portion of the output rotary body 20 is rotatably fitted to the fixed member 10, and integrally has an output shaft 24 exposed to the outside at the center thereof.
On the outer peripheral portion of the output rotary body 20, one cam surface 21 that gradually narrows between the inner peripheral surface 11a of the storage chamber 11 toward one side in the circumferential direction (clockwise side in FIG. 4). , The concave portion 22 adjacent to the one side of the one cam surface 21 and the inside of the storage chamber 11 toward the other side (counterclockwise side according to FIG. 4) so as to be contrary to the one cam surface 21. A plurality of sets (according to the illustrated example), the other cam surface 23 that gradually narrows the gap with the peripheral surface 11a and the locking portion 25 that locks the biasing member 50 are arranged at predetermined angles (equal intervals). 3 sets) are arranged side by side.

The cam surface 21 and the cam surface 23 are provided symmetrically. Each of the cam surfaces 21, 23 is formed in a convex curved shape that curves in the circumferential direction, and more specifically, it will be more than a value obtained by subtracting the diameter of each of the engagement elements 41, 42 from the radius of the storage chamber inner peripheral surface 11a. It is formed in an arc shape having a large radius and is provided such that the center position of the arc is displaced from the center position of the output rotary body 20.

The recess 22 is recessed from the outer peripheral surface of the output rotary body 20 in the centripetal direction and penetrates in the axial direction of the output rotary body 20. At both ends of the recess 22 in the circumferential direction, there are pressed surfaces 22a and 22b that are pressed by the pressing transmission portion 31 of the input rotating body 30 to be described later. These pressed surfaces 22a, 22b are formed in a flat surface shape extending in the radial direction, one pressed surface 22a intersects one cam surface 21, and the other pressed surface 22b the other cam surface 23. Intersects with.

The locking portion 25 is a concave portion that is arranged between the one cam surface 21 and the other cam surface 23 that are opposite to each other on the outer peripheral portion of the output rotary body 20, and specifically, the biasing member 50 is inserted therethrough. It is composed of an insertion space portion 25a and a bottom space portion 25b formed on the back side (bottom side) of the insertion portion.
The insertion space portion 25a forms a space having a constant width. Further, the bottom space portion 25b forms a space having a wider width in the circumferential direction than the insertion space portion 25a. The insertion space portion 25a and the bottom space portion 25b fix the proximal end portion of the biasing member 50 to be inserted so as not to be easily pulled out.

Further, on the side surface of the input rotary body 30 on the output rotary body 20 side, a plurality (three in the illustrated example) of pressure transmitting portions 31 are provided at predetermined intervals in the circumferential direction so as to correspond to each recess 22. It is projected.

The pressure transmitting portion 31 is fitted in the recess 22 of the output rotary body 20 in a state having a circumferential play, and is formed in a substantially fan shape projecting from the inside of the recess 22 in the centrifugal direction. It has contact surfaces 31a and 31b that can contact the pressed surfaces 22a and 22b of the output rotary body 20 and can also contact the engaging elements 41 and 42.

Each of the contact surfaces 31a and 31b is continuous in the radial direction from the inside of the recess 22 to the outside of the recess 22. One abutting surface 31a is formed in a flat surface shape that is substantially parallel to the one pressed surface 22a in the recess 22, and the other contact surface 31b is a flat surface that is substantially parallel to the other pressed surface 22b in the recess 22. It is formed in a planar shape.
The circumferential width between the contact surfaces 31a and 31b is set to be slightly smaller than the circumferential width between the pressed surfaces 22a and 22b of the output rotary body 20.

The engagement elements 41, 42 are formed in a cylindrical shape or a spherical shape (a cylindrical shape in the illustrated example), and are provided in a pair corresponding to the one and the other cam surfaces 21, 23.
Of the pair of engaging elements 41, 42, one engaging element 41 is arranged so as to contact the one cam surface 21 and the storage chamber inner peripheral surface 11a, and the other engaging element 42 is arranged on the other cam surface 23 and the accommodation surface. It is arranged so as to contact the indoor peripheral surface 11a. Then, each of the engaging elements 41 and 42 is stationary at a position slightly protruding to the inside of the recess 22 from the pressed surfaces 22a and 22b of the recess 22 while being pressed by the biasing member 50 described later.

The urging member 50 is formed by bending a long flat plate-shaped spring material into a substantially Y shape, and has a fastening portion 51 fixed to the fastening portion 25 of the output rotor 20 and the fastening portion. It is composed of two pressing portions 52, 52 extending in a bifurcated manner from 51, and the pressing portions 52, 52 urge the pair of engaging elements 41, 42 to separate.
The fastening portion 51 is a substantially circular portion that follows the bottom space portion 25b of the locking portion 25 on the outer periphery of the output rotary body 20, and a narrow parallel plate that follows the insertion space portion 25a of the locking portion 25. It is composed of a shape part.
Each pressing portion 52 extends from the fastening portion 51 and inclines toward the cam surface 21 side (or cam surface 23 side), and the surface in the inclination direction is the outer circumference of the corresponding engaging element 41 (or engaging element 42). It is in contact with the surface.

Next, the characteristic effects of the clutch mechanism 1 having the above structure will be described in detail.
First, in a state where no rotational force is applied to either the output rotary body 20 or the input rotary body 30 (see FIG. 4 ), the engaging elements 41 and 42 are pressed by the biasing member 50, respectively, and the cam surface 21 is pressed. , 23 and the inner peripheral surface 11a of the storage chamber 11 are pressed against a wedge-shaped portion.
Therefore, the output rotary body 20 is maintained in a stationary state so as not to rotate in one direction (clockwise according to FIG. 4) or the other direction (counterclockwise according to FIG. 4).

From the above state, when the output rotary body 20 is externally applied with a rotational force in the one direction (clockwise according to FIG. 4), the other of the output rotary bodies 20 that tries to rotate in the one direction. Since the other engaging element 42 is strongly pressed between the cam surface 23 and the inner peripheral surface 11a of the storage chamber, the output rotating body 20 is prevented from rotating in the one direction.
Similarly, when a rotational force in the other direction (counterclockwise according to FIG. 4) is applied to the output rotary body 20 from the outside, the output rotary body 20 that tries to rotate in the other direction is rotated. Since the one engagement member 41 is strongly pressed against the one cam surface 21 and the storage chamber inner peripheral surface 11a so as to bite, the rotation of the output rotor 20 in the other direction is prevented.

Further, for example, as shown in FIG. 6, when the rotational force in one direction is applied to the input rotary body 30 [FIG. 6( a )], the pressing transmission portion 31 of the input rotary body 30 is first By contacting the engaging element 42 of FIG. 6(b), the friction between the engaging element 42 and the cam surface 23 and the friction between the engaging element 42 and the storage chamber inner peripheral surface 11a are reduced, and thereafter, Since the pressure transmitting portion 31 comes into contact with the pressed surface 22b in the recess 22 to push the output rotary body 20 [FIG. 6(c)], the output rotary body 20 smoothly rotates in the other direction.
Further, when the rotational force in the other direction is applied to the input rotating body 30, although not shown, the pressure transmitting portion 31 of the input rotating body 30 first comes into contact with the other engaging element 41, The friction between the engaging element 41 and the cam surface 21 and the friction between the engaging element 41 and the inner peripheral surface 11a of the storage chamber are reduced, and then the pressure transmitting portion 31 comes into contact with the pressed surface 22a in the recess 22 to output. Since the rotating body 20 is pushed, the output rotating body 20 smoothly rotates in the other direction.

The engagement/disengagement action by the engaging elements 41, 42 as described above can be satisfactorily obtained by appropriately setting the angle between the cam surfaces 21, 23 and the inner peripheral surface 11a of the storage chamber. Therefore, in the present embodiment, the angle formed by the tangent line between the storage chamber inner peripheral surface 11a and the engaging elements 41, 42 and the tangent line between the engaging elements 41, 42 and the cam surfaces 21, 23 is θ, and the accommodation is performed. When the coefficient of static friction between the inner peripheral surface 11a and the engaging elements 41, 42 and the coefficient of friction between the engaging elements 41, 42 and the cam surfaces 21, 23, whichever is smaller, is μ In addition, the relationship of sin θ/(cos θ+1)≦μ is established. This will be described in detail below.

In the following description, the other engagement element 42 and the other cam surface 23 are used, but the one engagement element 41 and the one cam surface 21 are also symmetrically symmetrical and operate similarly. Of course

FIG. 7 and FIG. 8 are schematic diagrams showing the relationship among the storage chamber inner peripheral surface 11a, the engagement element 42, and the cam surface 23.
In FIG. 8, with respect to the pair of engaging elements 41 and 42, the y-axis is arranged such that the engaging element 42 that locks the right rotation of the output rotary body 20 is on the left side and the engaging element 41 that locks the left rotation is on the right side in FIG. When viewed as described above, it is a straight line which is an intermediate line between the left and right engaging elements 42, 41 and which passes through the center point O of the output rotary body 20. The x-axis is a straight line orthogonal to the y-axis and passing through the center point O of the output rotary body 20.

The meanings of the symbols in FIGS. 7 to 8 and the mathematical formulas are as follows.
A: A tangent line between the engagement element 42 and the storage chamber inner peripheral surface 11a (see FIG. 7)
B: Tangent line between the engagement element 42 and the cam surface 23: Height from the x-axis to the contact point between the engagement element 42 and the output rotor 20 (see FIG. 8)
L: Moment arm (the shortest distance between the center O of the output rotary body 20 and the line of action of the load that the output rotary body 20 receives from the engagement element 42)
L _POFF : _Distance from the center O of the output rotor 20 to the intersection of the line of action of the load received by the output rotor 20 from the engaging element 42 and the y-axis L _OFF : From the center O of the output element 20 to the engaging element 42 Distance P to the intersection of the normal line and the y-axis at the contact point position: The load that the engaging element 42 receives from the cam surface 23 (see FIG. 7)
P _s : Load received by the engaging element 42 from the biasing member 50 R ₁ : Load received by the engaging element 42 from the storage chamber inner peripheral surface 11 a R ₂ : Friction force between the storage chamber inner peripheral surface 11 a and the engagement element 42 R _p : Engagement element 42 And the frictional force r of the cam surface 23: The distance from the contact point between the engaging element 42 and the output rotary body 20 to the point where the normal line at the contact point and the y-axis intersect (see FIG. 8).
θ: Angle between a tangent line A between the engaging element 42 and the inner peripheral surface 11a of the storage chamber and a tangent line B between the engaging element 42 and the other cam surface 23 (see FIG. 7)
θ ₁ : tangent line A between the engaging element 42 and the _inner peripheral surface 11a of the storage chamber and the angle with the x axis θ ₂ : tangent line B between the engaging element 42 and the other cam surface 23 and the angle with the x axis θ _POFF : Output The angle between the line of action of the load that the rotating body 20 receives from the engaging element 42 and the y-axis (see FIG. 8)
α: Constant μ: The smaller static friction coefficient of the static friction coefficient between the storage chamber inner peripheral surface 11a and the engagement element 42 or the static friction coefficient between the engagement element 42 and the cam surface 23.

First, consider the static balance of the force around the engaging element 42 that generates the holding torque. As a precondition, it is assumed that the engaging element 42 does not rotate and slips, the load from the urging member 50 is constant, and the friction between the urging member 50 and the engaging element 42 can be ignored, and the storage chamber inner peripheral surface 11 a and the cam surface 23. Also, the engagement element 42 is not elastically deformed.

Since the engaging element 42 does not rotate and the friction of the contact portion with the urging member 50 can be ignored, from the balance of the moment of the engaging element 42,
R _p =R ₂ (1)

From the static balance of the forces in the x and y directions,
_{-P s -Psinθ 2 -R P cosθ 2} + R 1 sinθ 1 -R 2 cosθ 1 = 0
Pcosθ ₂ -R _P sinθ ₂ -R ₁ cosθ ₁ -R ₂ sinθ ₁ =0 ・・・・・ (2)

Substituting equation (1) into equation (2),
R ₁ sin θ ₁ -R ₂ (cos θ ₁ +cos θ ₂ )=P _s +P sin θ ₂
R ₁ cos θ ₁ +R ₂ (sin θ ₁ +sin θ ₂ )=P cosθ ₂ (3)

Here, assuming a case where a load just before the engaging element 42 slips is applied,
R ₂ = μR ₁ (4)

Substituting equation (4) into equation (3),
R ₁ (sin θ ₁ -μ(cos θ ₁ +cos θ ₂ ))=P _s +P sin θ ₂
R ₁ (cos θ ₁ + μ(sin θ ₁ +sin θ ₂ ))=P cosθ ₂ (5)

Divide each side,
{sinθ ₁ -μ(cosθ ₁ +cosθ ₂ )}/{cosθ ₁ +μ(sinθ ₁ +sinθ ₂ )}=(P _s +Psinθ ₂ )/Pcosθ ₂

For simplicity, let α be the left side that is a constant once the structure is determined.
{sin θ ₁ -μ(cos θ ₁ +cos θ ₂ )}/{cos θ ₁ +μ(sin θ ₁ +sin θ ₂ )}=α
α=(P _s +P sin θ ₂ )/P cos θ ₂

Solving for P,
P=P _s /(α cos θ ₂ −sin θ ₂ ) (6)

The torque exerted on the output rotary body 20 by the reaction force from the engaging elements 42 is:
T=3Lsqrt(P ² +R _P ² )・・・・・(7)
(Note that sqrt() represents the square root.)

Where the moment arm L is
L=L _POFF sin θ _POFF (8)

θ _POFF is obtained by adding the P and R _P resultant force angles to the angle θ ₂ between the _engagement element 42 and the contact surface of the output rotor 20.
θ _POFF = θ ₂ +Tan ^-1 (R _P /P) (9)

In addition, the height from the x-axis passing through the center O of the output rotor 20 to the contact point between the engagement element 42 and the output rotation element 20 is h, and the normal from the contact point between the engagement element 42 and the output rotation element 20. Let r be the distance to the point where the y-axis intersects.
rsin θ ₂ =(L _POFF +h)tan θ _POFF
h=rcos θ ₂ -L _OFF

From the above formula,
L _POFF =(rsin θ ₂ /tan θ _POFF )-rcos θ ₂ +L _OFF・・・・・ (10)

From the above, from the given P _s and the dimensions, angles and static friction coefficient μ of each structure, P, R ₁ and R ₂ are obtained using the equations (6), (4) and (5), and (7) The maximum torque that the engaging element 42 can withstand can be calculated by the equation (10).

By the way, paying attention to the expression (6), the load P just before slipping increases as the denominator on the right side approaches 0, and eventually diverges to infinity. In other words, under certain conditions, no matter how much torque is applied, theoretically there is no slippage.

When the denominator on the right side of the equation (6) has a positive value, it starts sliding with a finite load.
αcos θ ₂ -sin θ ₂ >0

Under conditions other than the above, it does not slide out under a finite load.
αcosθ ₂ -sinθ ₂ ≦ 0
Here, if α is restored,
{sinθ ₁ -μ(cosθ ₁ +cosθ ₂ )}cosθ ₂ /{cosθ ₁ +μ(sinθ ₁ +sinθ ₂ )}-sinθ ₂ ≤0
Solving this,
sin(θ ₁ -θ ₂ )/{cos(θ ₁ -θ ₂ )+1}≦μ ・・・(11)

If the combination of θ ₁ and θ _{2 that} satisfy the condition of the expression (11) is adopted, the fixed member 10, the engagement element 42, and the output rotary body 20 that do not slip even if torque is applied can be designed. It is important to set the angle difference between θ ₁ and θ ₂ as little as possible.

Here, since θ ₁ -θ ₂ =θ,
sin θ/(cos θ+1)≦μ (11)
Holds.

Therefore, by setting the angle θ so as to satisfy the expression (11), the engagement and disengagement action of the engagement elements 41, 42 is satisfactorily obtained.

According to the clutch mechanism 1 having the above-described configuration, the integral pressure transmitting portion 31 is fitted into the single space inside and outside the recess 22, and the flat contact surfaces 31a and 31b of the pressure transmitting portion 31 are pressed against the pressed surface 22a. 22b and the engaging elements 41 and 42 are sequentially brought into contact with each other. With this simple structure, size reduction is easy, productivity is good, malfunctions due to foreign matter do not easily occur, and durability is good.

Further, since the cam surfaces 21 and 23 are formed into arcuate convex curved surfaces having a radius larger than the value obtained by subtracting the diameter of the engaging elements 41 and 42 from the radius of the storage chamber inner peripheral surface 11a, the storage chamber inner peripheral surface 11a is formed. The angle θ between the tangent line between the engagement element 41 and 42 and the engagement element 41, 42 and the cam surface 21, 23 is within a wider range compared to the conventional technique in which the cam surface is formed flat. Can be set appropriately. Therefore, for example, even when the engaging elements 41, 42 are made smaller by bringing them closer to the inner side of the wedge-shaped portion, the angle θ can be secured relatively large, and the engaging elements 41, 42 can be connected to the storage chamber inner peripheral surface 11a and the cam. The wedge-shaped portion formed by the surfaces 21 and 23 can be easily designed to bite. As a result, the clutch mechanism 1 as a whole can be downsized while maintaining a good engagement/disengagement action by the engagement elements 41, 42.

Further, as the description of the clutch mechanism 1, three sets of the cam surfaces 21, 23, the concave portions 22, the engaging elements 41, 42, the biasing member 50, and the like are arranged on the outer peripheral portion of the output rotary body 20, but these are described. It is also possible to provide two sets or four or more sets.

It has been confirmed that it is also effective to adopt the following configuration in the clutch mechanism 1 in order to reduce the possibility of malfunction due to mechanical wear or deformation due to long-term use or the like. One of them is to provide the cam surfaces 21 and 23 with a projection that slightly protrudes radially outward, closer to the recess 22 than the contact point with the engaging elements 41 and 42. Further, one is to set the angle between the cam surfaces 21 and 23 on the outer periphery of the output rotary body 20 and the circumferential end face without the recess 22 to be 90° or more. Further, one is to set the ratio of the outer diameters of the engagement elements 41 and 42 to the inner diameter of the storage chamber 11 to a range of 0.20 or more and 0.27 or less.

Regarding the reduction in size, more specifically, it is possible to reduce the size from an outer diameter of 12 mm, which was difficult to achieve with other clutch mechanism configurations, to about 6 mm. Since the clutch mechanism itself can be miniaturized in this manner, it can be incorporated in the finger portion of a small robot hand, as shown in the above embodiment.

In the above embodiment, the structure of a so-called spur reducer in which a stepped gear is combined is adopted as the gear mechanism 2, and the clutch mechanism 1 is arranged on the output side (joint side) of the gear mechanism 2 to externally The backlash due to the load from was completely removed. However, the clutch mechanism 1 may be intentionally arranged in the middle of the plurality of gears forming the gear mechanism 2 so that a slight backlash remains.
For example, as another example, the configuration shown in FIG. 9 may be considered. The finger 310 shown in FIG. 9 operates by transmitting the rotational driving force of the motor 301 as follows. A gear head 302 is connected to the motor 301. Inside the gear head, a plurality of stages of planetary gear reduction mechanisms and a clutch mechanism (not shown) that does not transmit the force from the output side are incorporated. The gear head 302 is held by the second link 312. The output from the gear head 302 is transmitted to the pulley mechanism 304 from the bevel gear mechanism 303 arranged on the second link 312. The joint 313 and the first link 311 are operated by the output of the pulley mechanism 304.

In the robot hand of the present invention, the clutch mechanism capable of interrupting the load from the output side and the speed reducing mechanism including a plurality of gears can be integrally configured, so that the overall size increases excessively and the weight increases. Can be avoided. In addition, it is possible to prevent a decrease in operation accuracy due to a misalignment between the reduction mechanism and the clutch mechanism. This is effective in improving responsiveness, operation efficiency, and accuracy in a small robot hand.
Further, even if the output of the drive motor is unintentionally reduced or stopped due to power failure, noise, etc., the clutch mechanism can hold the position of the finger mechanism in a non-energized state, so that the gripped object may be dropped. It is possible to provide high safety without any trouble.
Further, even when the power supply to the drive motor is cut off while gripping with the finger mechanism of the robot hand, the gripped state can be maintained, so that the current consumption can be greatly reduced.

The robot hand of the present invention is mainly used in an industrial robot as an end effector having a gripping ability, and can provide added value such as high gripping reliability and low power consumption driving.

1: Clutch mechanism 2: Gear mechanism 10: Fixed member 11: Storage chamber 11a: Peripheral surface of storage chamber 20: Output rotor 21,23: Cam surface 22: Recessed portion 22a, 22b: Pressed surface 24: Output shaft 30: Input Rotor 31: Pressing transmission part 31a, 31b: Contact surface 41, 42: Engagement member 50: Energizing member 60: Motor 51: Fastening part 52: Pressing part 71, 72: Multistage gear 80: Cage 100: Rotation Force transmission device 200: robot hand 210: bases 220, 230, 240: fingers 241: first link 242: second link 243: first joint 244: second joint

Claims (2)

In a robot hand with multiple fingers,
A motor that serves as a drive source for the finger joint, and a torque transmission device that transmits the rotation of the motor as input torque from the input side to the output side,
The torque transmission device includes a clutch mechanism that transmits the input torque applied to the input side to the output side but does not transmit a reverse input torque applied to the output side to the input side, and a gear mechanism including a plurality of gears. is composed of a,
The clutch mechanism includes a storage chamber having a cylindrical space, an output rotary body coaxially stored in the storage chamber, an input rotary body provided coaxially with the output rotary body, and the storage chamber. An engaging member provided between the inner peripheral surface and the outer peripheral surface of the output rotating body, and a biasing member for biasing the engaging member to one side in the circumferential direction, the outer peripheral surface of the output rotating body, A cam surface is formed that gradually narrows a space between the input rotary body and the inner peripheral surface of the storage chamber toward the one side, and when the input rotary body rotates to the other side with respect to the one side, the input rotary body is engaged with the engagement surface. After abutting against the mating member, the input rotating body is brought into contact with the output rotating body to push the output rotating body, which is incorporated in the finger,
The plurality of fingers, each finger having one or more of the joints;
A robot hand , wherein one or more combinations of the motor for driving the joint and the rotational force transmitting device are arranged for one joint . The robot hand according to claim 1, wherein the clutch mechanism is disposed on the output side of the gear mechanism .

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