Force detection device and robot

Abstract

This force detection device comprises: a worm constituting a worm gear; a case that is displaced together with the worm; an elastic body which, when the worm is displaced, biases the case or the worm in a direction suppressing the displacement; and a sensor that detects the displacement of the case or the worm.

Description

Force detection device and robot

[0001] The present invention relates to a force detection device and a robot.

[0002] As a torque sensor using a worm gear consisting of a worm wheel and a worm, there is a technology in which the torque of the worm wheel is received by the axial force of the worm biased by an elastic body, and the torque is detected by detecting the displacement of the elastic body (see, for example, Patent Document 1).

[0003] Patent No. 4096816

[0004] An example of the configuration of a conventional torque sensor is shown in Fig. 11. In the conventional configuration, a bearing 1113 supports a worm 1110, which is a movable part, and the worm 1110 moves in the axial direction relative to the bearing 1113. When the worm 1110 moves in this manner, the contact between the worm 1110 and the bearing 1113 is sliding contact.

[0005] When the worm 1110 stops moving axially, the force acting on the worm 1110 due to the torque of the worm wheel 1120 is equal to the elastic force of the elastic body 1130 due to the displacement of the worm 1110, so the torque can be measured by detecting the displacement of the worm 1110.

[0006] Here, when a leaf spring is used as the elastic body 1130, the position of the contact point between the protrusion of the worm 1110 and the leaf spring 1130 changes due to the displacement of the worm 1110, so that the contact between the protrusion of the worm 1110 and the leaf spring 1130 becomes a sliding contact.

[0007] Since friction in sliding contact is sliding friction, the slidability is low and it is difficult to measure torque accurately.

[0008] An object of the present disclosure is to provide a force detection device and a robot that are capable of measuring force with high accuracy by reducing friction.

[0009] In one embodiment of the present disclosure, a force detection device includes a worm that constitutes a worm gear, a case that displaces together with the worm, an elastic body that biases the case or the worm in a direction that suppresses displacement when the worm displaces, and a sensor that detects displacement of the case or the worm.

[0010] In one embodiment of the present disclosure, the robot includes a force detection device having a worm that constitutes a worm gear, a case that displaces together with the worm, an elastic body that biases the case or the worm in a direction that suppresses displacement when the worm displaces, and a sensor that detects displacement of the case or the worm.

[0011] According to the present disclosure, it is possible to provide a force detection device and a robot that are capable of measuring force with high accuracy by reducing friction.

[0012] Figure showing an example of a force detection deviceFigure showing an eddy current displacement sensorFigure showing a photo sensorFigure showing a capacitive displacement sensorFigure showing a capacitive displacement sensorFigure showing a laser displacement sensorFigure showing an example using multiple leaf springs with different spring constantsEnlarged view of the bearing section and leaf springFigure showing another example using multiple leaf springs with different spring constantsEnlarged view of the bearing section and leaf springFigure showing which springs are related to the repulsive force and what happens to the leftward force depending on the magnitudes of D1 and D2 when the movable section is displaced to the rightFigure showing which springs are related to the repulsive force and what happens to the leftward force depending on the magnitudes of D1 and D2 when the movable section is displaced to the rightFigure explaining the principle of detecting torque by displacement

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the embodiments described below are merely examples, and the present disclosure is not limited to the following embodiments.

[0014] However, more detailed explanations than necessary may be omitted, for example, detailed explanations of well-known matters or redundant explanations of substantially the same configurations may be omitted, in order to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art.

[0015] First, the principle of force detection for detecting torque based on displacement will be described with reference to FIG.

[0016] The worm 1110 and the worm wheel 1120 constitute a worm gear. When a force is applied to the worm wheel 1120, a torque is generated in the worm wheel 1120 about an axis 1121. The torque generated in the worm wheel 1120 displaces the worm 1110 in the thrust direction.

[0017] When the worm 1110 is displaced, the elastic body 1130 biases the worm 1110 in a direction that suppresses the displacement, so the worm 1110 displaces in the thrust direction until the force based on the torque of the worm wheel 1120 and the repulsive force of the elastic body 1130 generated by the displacement of the worm 1110 become equal to each other. In this example, a leaf spring is used as the elastic body 1130.

[0018] If the torque of the worm wheel 1120 is T, the radius of the worm wheel 1120 is r, the elastic constant of the elastic body 1130 is k, the force in the thrust direction of the worm 1110 generated by T (hereinafter referred to as the "worm thrust force") is f, and the thrust displacement is x, then T = r x f (1) f = k x x (2) and therefore the relationship between the torque T and the thrust displacement x is T = r x k x x (3)

[0019] In other words, if r and k are known, the torque T can be detected from the thrust displacement x.

[0020] On the other hand, by transforming equation (1), we obtain: f=T / r (4) Equation (4) describes the relationship between the torque T of the worm wheel 1120 and the worm thrust force f.

[0021] Here, sliding friction is taken into consideration. For example, sliding friction exists in the bearing portion 1113 of the worm 1110.

[0022] When the worm 1110 is held by sliding bearings 1113 at n locations, if the friction coefficients of the bearings 1113 are μ0, μ1, ..., μn and the normal forces of the sliding bearings 1113 are F0, F1, ..., Fn, the total friction force is μ0×F0+μ1×F1+ ...+μn×Fn, and therefore the worm thrust force f is given by f=T / r-μ0×F0-μ1×F1- ...-μn×Fn (5) In the conventional example shown in Fig. 11, sliding bearings 1113 are present at at least two locations.

[0023] If T / r is smaller than the maximum frictional force and is balanced with the frictional force, the worm thrust force f becomes 0 and no thrust displacement x occurs, so the torque T cannot be detected.

[0024] Furthermore, if T / r is greater than the frictional force, the frictional force will cause an error when calculating the torque T from the thrust displacement x, and the accuracy of force detection will deteriorate.

[0025] In the following embodiments, we will first describe a device that improves this deterioration in accuracy, and then we will describe a device that solves the problem of reduced torque measurement accuracy due to sliding friction between the worm and the elastic body.

[0026] First Embodiment FIG. 1 is a diagram showing an example of a force detection device 100 equipped with a displacement sensor that detects displacement of a case.

[0027] In the present disclosure, the worm 110 is supported by a case 112 that is integrated with the worm 110. This allows the number of contact parts to be reduced, and also allows the entire case to be supported by the rolling contact support parts 140.

[0028] Friction in rolling contact is rolling friction, which is much smaller than sliding friction, so the device shown in Fig. 1 can make the friction during thrust displacement rolling friction, whose friction force is much smaller than sliding friction. As a result, most of the torque of the worm wheel 120 becomes a worm thrust force, making it possible to detect torque with high accuracy.

[0029] The force detection device 100 includes a worm 110, a case 112, a worm wheel 120, an elastic body 130, a support portion 140, and a sensor 150. The case 112 includes a bearing portion 113. The worm 110 and the case 112 are integrated to form a movable portion 114.

[0030] The worm 110 is a worm that constitutes a worm gear together with the worm wheel 120. The worm gear has a structure in which, when the worm 110 rotates, the spiral teeth 111 of the worm 110 cause the worm wheel 120 to rotate about an axis 121.

[0031] It is desirable to apply pressure to the worm 110 or the case 112 using an elastic body 130. The elastic body 130 may be a metal spring such as a leaf spring, cylindrical spring, or conical spring, or may be a flexible solid part such as a rubber member or elastomer. Instead of applying pressure to the worm 110, pressure may be applied to the case 112.

[0032] The case 112 is integrated with the worm 110 to form a movable part 114. The case 112 houses the worm 110 therein, and has a hole therein through which the worm 110 and the worm wheel 120 come into contact with each other.

[0033] The case 112 is not limited to a box-shaped case, but may have any shape as long as it supports the worm 110, displaces together with the worm 110, and is supported by rolling contact with another member.

[0034] The case 112 includes a bearing portion 113. The bearing portion 113 supports the worm 110, and the worm 110 is fixed to the case 112 in the thrust direction. In other words, the worm 110 and the case 112, which are the movable portion 114, move together in the thrust direction.

[0035] The worm wheel 120 constitutes a worm gear together with the worm 110. The worm wheel 120 rotates due to the rotation of the worm 110. When torque is applied to the worm wheel 120 by an external force and the worm wheel 120 rotates, the worm 110, which is the movable part, is displaced in the thrust direction.

[0036] When a force is applied to the worm 110 and the worm 110 is displaced, the elastic body 130 biases the worm 110 in a direction that suppresses the displacement. The elastic body 130 biases at least one of the worm 110 and the case 112. Note that, although a spring such as a leaf spring is an example of the elastic body 130, anything other than a leaf spring can be used as long as it can bias the worm 110.

[0037] The support part 140 supports the movable part 114, for example, the case 112. The support part 140 is, for example, a linear slider, and is displaced in the thrust direction by rolling contact. Note that the structure of the support part 140 may be a structure using rolling contact other than a linear slider.

[0038] The sensor 150 detects the displacement of the movable part 114. The sensor 150 is preferably a non-contact type displacement sensor. In FIG. 1 , for example, the displacement sensor may be disposed on the outside of the metal worm 110, and the distance between the worm 110 and the displacement sensor may be measured in a non-contact manner. Alternatively, the sensor 150, which is a displacement sensor, may measure the distance between the case 112 and the displacement sensor in a non-contact manner. The sensor will be described later.

[0039] In the present disclosure, as shown in FIG. 1 , the worm 110 is fixed to the case 112 to form the movable part 114, thereby eliminating sliding contact (rubbing contact) of the bearing part 113, and the worm 110 and the case 112 operate as the movable part 114.

[0040] The movable portion 114 is supported at one point by the support portion 140, reducing the number of contact points and allowing the contact associated with displacement in the thrust direction to be rolling contact, thereby reducing friction in the thrust direction.

[0041] Furthermore, the present disclosure uses a worm gear. In a worm gear, the worm wheel 120 rotates when the worm 110 rotates, but the worm 110 cannot be rotated even if the worm wheel 120 rotates, so self-locking is effective. Therefore, the displacement of the worm 110 can be maintained without the need for additional parts such as a brake.

[0042] Furthermore, even when the worm 110 is rotated, no thrust force is generated in the worm 110, and thrust displacement occurs in response only to the load on the worm wheel 120. In other words, thrust displacement occurs only due to the torque of the worm wheel 120 caused by an external force, so that external forces can be detected efficiently.

[0043] <Sensor> As a non-contact type displacement sensor, an eddy current displacement sensor shown in Fig. 2 can be used. A high-frequency magnetic field is generated by passing a high-frequency current through a coil inside the sensor head 210, and when metal 220 is present in this magnetic field, an eddy current is generated on the metal surface due to electromagnetic induction according to the distance between the metal 220 and the sensor head 210, and the oscillation amplitude changes.

[0044] The eddy current displacement sensor is a sensor that measures the distance between the sensor head 210 and the metal 220 by utilizing the fact that the magnitude of the oscillation amplitude correlates with the distance between the sensor head 210 and the metal 220. When the worm 110 has a portion made of the metal 220, the displacement of the worm 110 can be detected by detecting how much the oscillation amplitude has changed.

[0045] Another example of a non-contact displacement sensor is a photosensor shown in Fig. 3. The photosensor has a light-emitting section made up of a light-emitting element 310 that emits light, and a light-receiving section made up of a light-receiving element 320 that receives light and outputs a signal, facing each other, and utilizes the phenomenon that when an object 330 passes between the light-emitting element 310 and the light-receiving element 320, part of the light emitted by the light-emitting element 310 is blocked, causing a change in the amount of light received by the light-receiving element 320.

[0046] The worm 110 is disposed as the object 330, and the displacement of the worm 110 can be detected by detecting how much the amount of light received by the light receiving element 320 has changed.

[0047] As another example of a non-contact type displacement sensor, a capacitance displacement sensor shown in Fig. 4A or 4B can be used. The capacitance displacement sensor shown in Fig. 4A is a sensor that utilizes the fact that the distance between a movable electrode 420 and a fixed electrode 430 that constitute capacitance changes due to the displacement of an object 410, thereby changing the capacitance.

[0048] Alternatively, as shown in FIG. 4B, a movable electrode 420, which displaces integrally with the object 410, moves in and out between fixed electrodes 430 arranged opposite to the movable electrode 420, and the opposing area between the movable electrode 420 and the fixed electrode 430 changes, thereby changing the capacitance.

[0049] In this embodiment, the target object 410 is a worm 110. By disposing a fixed electrode 430 across a space from the metal worm 110, the displacement of the worm 110 can be detected from a change in the capacitance of a capacitor formed by the fixed electrode 430 and the worm 110.

[0050] As yet another example of a non-contact type displacement sensor, a laser displacement sensor shown in Fig. 5 can be used. The laser displacement sensor is a sensor that emits laser light from a light-emitting element 510 toward an object 520 and detects the light-receiving position on a light-receiving element 530 or the time until the light is received, thereby detecting position information of the object.

[0051] By using the worm 110 as the object 520, the displacement of the worm 110 can be detected from the light receiving position or the time until the light is received.

[0052] By using a non-contact displacement sensor as described above, the displacement sensor does not affect the displacement of the worm 110. Furthermore, a displacement sensor that is less expensive than a torque sensor can detect force. A photo sensor or laser displacement sensor can also be used for a worm 110 made of a material other than metal. Furthermore, sensors other than those exemplified in FIGS. 2 to 5 can also be used as non-contact displacement sensors.

[0053] <Elastic Body> Instead of the elastic body 130, a combination of a first elastic body and a second elastic body having a larger elastic constant than the first elastic body may be used. Three or more elastic bodies may also be combined. By using only the first elastic body to apply force for small displacements and using the first elastic body and a second elastic body having a larger elastic constant than the first elastic body to apply force for large displacements, it is possible to accurately detect displacements caused by small forces.

[0054] 6 shows an example in which a plurality of leaf springs with different spring constants are used as the elastic body. Note that in FIG. 6, the worm 110, case 112, and other components within the movable part 614 are not shown.

[0055] The worm wheel 620 and the worm 110 inside the movable part 614 form a worm gear, and the worm 110 is fixed to the movable part 614 in the thrust direction.

[0056] The movable part 614 has a hole for contacting the internal worm 110 and worm wheel 620. The leaf spring 631 with a small spring constant comes into contact with the movable part 614 in advance, and the leaf spring 632 with a large spring constant comes into contact with the movable part 614 when the movable part 614 has been displaced to a certain extent.

[0057] Therefore, when the displacement of the movable part 614 is small, the movable part 614 is biased only by the leaf spring 631 with a small spring constant, and when the displacement is large, the leaf spring 631 with a small spring constant and the leaf spring 632 with a large spring constant bias the movable part 614. In this way, by using two types of leaf springs, it is possible to switch the rate of change of the external force relative to the displacement between two levels. Note that the movable part 614 can be biased by biasing the worm 110 or the case 112.

[0058] Therefore, highly accurate detection can be performed even with small forces. Also, three or more elastic bodies with different elastic constants may be used so that the worm 110 or the case 112 is biased as the displacement increases. Furthermore, multiple elastic bodies with different elastic constants other than leaf springs may also be used.

[0059] When the leaf springs 631 and 632 bias the movable part 614, the leaf springs 631 and 632 come into contact with the movable part 614, and the leaf springs 631 and 632 are bent due to the displacement of the movable part 614. As the leaf springs 631 and 632 bend, the contact points between the movable part 614 and the leaf springs 631 and 632 change, generating a frictional force.

[0060] Therefore, rollers are used in the portions where the movable portion 614 comes into contact with the leaf springs 631 and 632, thereby reducing friction caused by contact between the bearing portion 113 and the elastic body 130.

[0061] FIG. 7 is a diagram showing an example of an enlarged contact area between the movable part 614 and the leaf springs 631 and 632, which is the dotted line area in FIG.

[0062] The contact portion 660 includes protrusions 711 and 712. The protrusions 711 and 712 may be provided on the worm 110 or on the case 112. Alternatively, the protrusions 711 and 712 may be provided on the leaf springs 631 and 632.

[0063] The protrusion 711 has a roller 721 at its tip, and the protrusion 712 has a roller 722 at its tip. The roller 721 contacts the leaf spring 631, and the roller 722 contacts the leaf spring 632. The rollers 721 and 722 may be cylindrical rollers or spherical rollers. The rollers 721 and 722 bring the movable part 614 and the leaf springs 631 and 632 into contact with each other through rolling friction.

[0064] When the leaf springs 631 and 632 are bent due to displacement of the movable part 614, the parts of the leaf springs 631 and 632 that come into contact with the protrusions 711 and 712 of the movable part 614 change, but by providing rollers 721 and 722 at the tips of the protrusions 711 and 712, the friction caused by contact between the worm 110 or the case 112 and the elastic body 130 can be reduced.

[0065] In the first embodiment, in the initial state, the leaf spring with the small spring constant is simply in contact with the movable part 614 and does not bias it, but in the second embodiment, the leaf spring with the small spring constant is biased in advance in the initial state. In order to bias it in advance, it is sufficient to pre-bend the leaf spring.

[0066] Fig. 8 is a diagram showing another example in which a plurality of leaf springs with different spring constants are used as elastic bodies. Fig. 9 is a diagram showing an example in which the dotted line portion in Fig. 8 shows an enlarged view of the contact area between the movable part 614 and the leaf springs 831 and 832.

[0067] The contact portion 860 has protrusions 911 and 912. The protrusion 911 has a roller 921 at its tip, and the protrusion 912 has a roller 922 at its tip. The roller 921 contacts the leaf spring 831, and the roller 922 contacts the leaf spring 832. The rollers 921 and 922 may be cylindrical rollers or spherical rollers. The rollers 921 and 922 bring the movable portion 614 and the leaf springs 831 and 832 into contact with each other through rolling friction.

[0068] In the second embodiment, in the initial state (the displacement of the movable part 614 is 0), the leaf springs 831 and 833, which have a small spring constant, are fixed by a distance D1 inward (toward the center of the movable part 614) from the protrusion 911 of the movable part 614. That is, in the initial state, the leaf springs 831 and 833 flex and come into contact with the movable part 614, thereby biasing the movable part 614.

[0069] If the movable part 614 is displaced to the right by less than D1, the leaf springs 831 and 832 urge the movable part 614 from both sides, and if the movable part 614 is displaced to the right by D1 or more, the leaf spring 832 stops urging the movable part 614, and only the leaf spring 831 urges the movable part 614. In other words, depending on the displacement of the movable part 614, the movable part 614 transitions between a mode in which the first elastic body urges the movable part from both sides and a mode in which the first elastic body urges the movable part from one side.

[0070] In the initial state, the leaf springs 832 and 834, which have a large spring constant, are fixed outward by a distance D2 from the protrusion 912 of the movable part 614. In other words, the leaf springs 832 and 834 come into contact when the movable part 614 is displaced in the respective directions by D2 or more.

[0071] When the movable part 614 is displaced by less than D2, only the leaf spring with the small spring constant biases the movable part 614, and when the movable part 614 is displaced by D2 or more, both the leaf spring with the small spring constant and the leaf spring with the large spring constant bias the movable part 614. In other words, depending on the displacement of the movable part 614, the movable part transitions between a mode in which only the first elastic body biases the movable part, and a mode in which both the first elastic body and the second elastic body bias the movable part.

[0072] Alternatively, protrusions 911 and 912 may be provided on the leaf springs 831 and 832. In this case, the movable part 614 is initially fixed outward by a distance D1 and is in contact with a roller 921 provided on the leaf spring 831, and when the movable part 614 is displaced by a distance D2, it comes into contact with a roller 922 provided on the leaf spring 832.

[0073] As described above, the biasing mode, which determines which elastic body applies biasing force, changes depending on whether the displacement of the movable part 614 is equal to or greater than D1 and whether it is equal to or greater than D2. An example in which the movable part 614 is displaced by x to the right in the strass direction when both D1 and D2 are taken into consideration will be described using Figures 8 and 9. The total force applied to the left side of the movable part 614 by the elastic bodies can be calculated by adding the repulsive force of leaf spring 831 to the repulsive force of leaf spring 832 minus the repulsive force of leaf spring 833 minus the repulsive force of leaf spring 834.

[0074] When the movable part 614 is displaced by a predetermined distance (D1) or more, the leaf spring 833 no longer comes into contact with the movable part 614 and no longer applies any force. If the deflection of the leaf spring 831 and the deflection of the leaf spring 833 are the same in the initial state, the leaf spring 833 will bias the movable part 614 to the right until the movable part 614 is displaced by D1 to the right.

[0075] On the other hand, the leaf spring 831 biases the movable part 614 to the left regardless of the displacement, and the leaf spring 834 does not bias the movable part 614 regardless of the displacement.

[0076] Furthermore, when the movable part 614 is displaced to the right by a predetermined distance (D2) or more, the leaf spring 832 biases the movable part 614 to the left. Specifically, when the movable part 614 is displaced to the right by D2, the movable part 614 and the leaf spring 832 come into contact with each other, and the leaf spring 832 begins biasing the movable part 614 to the left.

[0077] Therefore, if the spring constant of the leaf springs 831 and 833, which have a small spring constant, is A [N / mm], and the spring constant of the leaf springs 832 and 834, which have a large spring constant, is B [N / mm], and D1 < D2, the total force acting on the left side for a displacement x [mm] of the movable part 614 is as follows:

[0078] When 0<x<D1, the total repulsive force is the "repulsive force of leaf spring 831" minus the "repulsive force of leaf spring 833." Since the repulsive force of leaf spring 831 increases by Ax in response to displacement x, and the repulsive force of leaf spring 833 decreases by Ax, the total repulsive force changes by 2Ax with respect to displacement x.

[0079] When D1<x<D2, the total repulsive force is the "repulsive force of the leaf spring 831." Since the repulsive force of the leaf spring 831 increases by Ax in response to the displacement x, the total repulsive force changes by Ax with respect to the displacement x.

[0080] When D2<x, the total repulsive force is the sum of the repulsive force of the leaf spring 831 and the repulsive force of the leaf spring 832. Since the repulsive force of the leaf spring 831 increases by Ax and the repulsive force of the leaf spring 832 increases by Bx in response to the displacement x, the total repulsive force changes by (A+B)x with respect to the displacement x.

[0081] Furthermore, if D2<D1, the total force acting on the left side relative to the displacement x of the movable part 614 is as follows:

[0082] When 0<x<D2, the total repulsive force is the "repulsive force of leaf spring 831" minus the "repulsive force of leaf spring 833." Since the repulsive force of leaf spring 831 increases by Ax in response to displacement x, and the repulsive force of leaf spring 833 decreases by Ax, the total repulsive force changes by 2Ax with respect to displacement x.

[0083] When D2<x<D1, the total repulsive force is "repulsive force of leaf spring 831" - "repulsive force of leaf spring 833" + "repulsive force of leaf spring 832." According to the displacement x, the repulsive force of leaf spring 831 increases by Ax, the repulsive force of leaf spring 833 decreases by Ax, and the repulsive force of leaf spring 832 increases by Bx, so the total repulsive force changes by (2A+B)x with respect to the displacement x.

[0084] When D1<x, the total repulsive force is the sum of the repulsive force of the leaf spring 831 and the repulsive force of the leaf spring 832. Since the repulsive force of the leaf spring 831 increases by Ax and the repulsive force of the leaf spring 832 increases by Bx in response to the displacement x, the total repulsive force changes by (A+B)x with respect to the displacement x.

[0085] Furthermore, when D1=D2, the total force acting on the left side with respect to the displacement x of the movable part 614 is as follows:

[0086] When 0<x<D1=D2, the total repulsive force is "repulsive force of leaf spring 831" - "repulsive force of leaf spring 833." Since the repulsive force of leaf spring 831 increases by Ax in response to displacement x, and the repulsive force of leaf spring 833 decreases by Ax, the total repulsive force changes by 2Ax with respect to displacement x.

[0087] When D1 = D2 < x, the total repulsive force is "the repulsive force of leaf spring 831" + "the repulsive force of leaf spring 832." Since the repulsive force of leaf spring 831 increases by Ax according to the displacement x, and the repulsive force of leaf spring 832 increases by Bx, the total repulsive force changes by (A + B)x with respect to the displacement x.

[0088] Therefore, by pre-bending the leaf spring with a small spring constant, it is possible to switch the rate of change of external force relative to displacement between three levels using two types of leaf springs. Also, by adjusting the values ​​of D1 and D2, it is possible to change the biasing force in the initial state.

[0089] Figure 10 shows the rate of change of the leftward force when the worm 110 is displaced to the right, with the spring constant of the weak spring being A [N / mm] and the spring constant of the strong spring being B [N / mm]. Figure 10 also shows which springs are related to the repulsive force depending on the magnitude of D1 and D2. The spring constants are given in parentheses.

[0090] 10A shows the case where D1<D2, FIG. 10B shows the case where D1>D2, and FIG. 10C shows the case where D1=D2. When the worm 110 is displaced to the left, the left and right are reversed, but the result is the same.

[0091] By changing D1 and D2, the rate of change can be changed, and therefore the force measurement range can be changed. D1 and D2 can be changed by changing the installation position of the leaf spring, by changing the height of the protrusion, or by changing the size of the roller.

[0092] 10, modes a and d are cases where the displacement of the movable part 614 is less than D1, and modes b and c are cases where the displacement of the movable part 614 is D1 or more. Also, modes a and c are cases where the displacement of the movable part 614 is less than D2, and modes b and d are cases where the displacement of the movable part 614 is D2 or more.

[0093] Although the embodiments have been described above with reference to the drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims. It is understood that such modifications or alterations also fall within the technical scope of the present disclosure. Furthermore, the components in the embodiments may be combined in any manner without departing from the spirit of the present disclosure.

[0094] (1) In one embodiment of the present disclosure, a force detection device includes a worm that constitutes a worm gear, a case that displaces together with the worm, an elastic body that biases the case or the worm in a direction that suppresses displacement when the worm displaces, and a sensor that detects displacement of the case or the worm.

[0095] (2) In one embodiment of the force detection device of the present disclosure, in the force detection device of (1), the case or the worm and the elastic body come into contact with each other by rolling friction.

[0096] (3) In one embodiment of the force detection device of the present disclosure, in the force detection device of (1), the case has a support portion, and the support portion is a linear slider that contacts and supports the case by rolling friction.

[0097] (4) In one embodiment of the present disclosure, the force detection device is the force detection device of (1), wherein the sensor is a non-contact sensor.

[0098] (5) In one embodiment of the force detection device of the present disclosure, in the force detection device of (1), the elastic body is a leaf spring.

[0099] (6) In one embodiment of the force detection device of the present disclosure, in the force detection device of (1), the elastic body is made up of a plurality of elastic bodies having different elastic constants.

[0100] (7) In one embodiment of the force detection device of the present disclosure, in the force detection device of (6), the elastic body includes a first elastic body and a second elastic body having an elastic constant greater than that of the first elastic body, and transitions between a first mode in which only the first elastic body or the worm is biased, and a second mode in which the first elastic body and the second elastic body or the worm are biased, depending on the displacement.

[0101] (8) In the force detection device according to one embodiment of the present disclosure, in the force detection device of (7), the first elastic body pre-biases the worm.

[0102] (9) In one embodiment of the force detection device of the present disclosure, the force that is biased against the worm or that is biased against the worm is changed by changing the position of the first elastic body relative to the worm in the force detection device of (8).

[0103] (10) In one embodiment of the force detection device of the present disclosure, in the force detection device of (8) or (9), the force detection device transitions between a third mode in which the first elastic body or the worm is biased from both sides and a fourth mode in which the first elastic body or the worm is biased from one side, depending on the displacement.

[0104] (11) A robot according to an embodiment of the present disclosure includes the force detection device of (1).

[0105] The present disclosure is applicable to force detection devices and robots.

[0106] 100 Force detection device 110, 1110 Worm 111 Spiral teeth 112 Case 113, 1113 Bearing portion 114, 614 Movable portion 120, 620, 1120 Worm wheel 121 Shaft 130, 1130 Elastic body 140 Support portion 150 Sensor 210 Sensor head 220 Metal 310, 510 Light-emitting element 320, 530 Light-receiving element 330, 410, 520 Object 420 Movable electrode 430 Fixed electrode 631, 632, 831, 832, 833, 834 Leaf spring 711, 712, 911, 912 Protrusion 721, 722, 921, 922 Roller

Claims

1. A force detection device comprising: a worm that constitutes a worm gear; a case that displaces together with the worm; an elastic body that biases the case or the worm in a direction that suppresses the displacement of the worm when the worm is displaced; and a sensor that detects the displacement of the case or the worm.

2. The force detection device according to claim 1, wherein the case or the worm and the elastic body are in contact with each other by rolling friction.

3. The force detection device according to claim 1, wherein the case has a support portion, and the support portion is a linear slider that contacts and supports the case by rolling friction.

4. The force detection device according to claim 1, wherein the sensor is a non-contact sensor.

5. The force detection device according to claim 1, wherein the elastic body is a leaf spring.

6. The force detection device according to claim 1, wherein the elastic body is composed of a plurality of elastic bodies having different elastic constants.

7. A force detection device as described in claim 6, wherein the elastic body includes a first elastic body and a second elastic body having an elastic constant greater than that of the first elastic body, and transitions between a first mode in which only the first elastic body biases the case or the worm, and a second mode in which the first elastic body and the second elastic body bias the case or the worm, depending on the displacement.

8. The force detection device according to claim 7, wherein the first elastic body biases the case or the worm in advance.

9. A force detection device according to claim 8, wherein the biasing force that biases said case or said worm in advance is changed by changing the position of said first elastic body relative to said case or said worm.

10. A force detection device as described in claim 8 or 9, which transitions between a third mode in which the first elastic body biases the case or the worm from both sides and a fourth mode in which the first elastic body biases the case or the worm from one side in response to the displacement.

11. A robot comprising the force detection device according to claim 1.