Force sensor

• US 9,989,427 B2
• Filed: 11/04/2014
• Issued: 06/05/2018
• Est. Priority Date: 11/05/2013
• Status: Active Grant

• Current Assignee: NSK Limited
• Original Assignee: NSK Limited
• Inventors: Teshigawara, Seiichi, Tobita, Kazuteru, Kuwahara, Masaki
• Primary Examiner(s): Caputo, Lisa
• Assistant Examiner(s): COTEY, PHILIP L
• Application Number:
  US15/032,402
• Publication Number:
  US 20160252410A1
• Time in Patent Office: 1,309 Days
• CPC Class Codes: G01D 5/12 using electric or magnetic means G01D5/06 takes precedence
• CPC Class Codes: G01D 5/30 the beams of light being detected by photocells
• CPC Class Codes: G01L 1/005 by electrical means and not provided for in G01L1/06 - G01L1/22
• CPC Class Codes: G01L 1/2206 Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
• CPC Class Codes: G01L 5/166 using photoelectric means

Abstract

A force sensor includes: a base; a first movable portion arranged to face the base; a second movable portion arranged to face the first movable portion; a support that is provided on the base and rockably supports the first movable portion and the second movable portion; a joint that is provided to the support and rotatably supports the second movable portion; and a first detection unit that can detect a force component causing the first movable portion and the second movable portion to rock and a second detection unit that can detect a force component causing the second movable portion to rotate, when external force is applied to at least one of the first movable portion and the second movable portion.

Claims

1. A force sensor comprising:

a base;

a first movable portion arranged to face the base;

a second movable portion arranged to face the first movable portion, wherein the first movable portion and the second movable portion are movable to be tilted relative to the base;

a support that is provided on the base and rockably supports the first movable portion and the second movable portion;

a joint that is provided to the support and rotatably supports the second movable portion;

a first detection unit that includes three or more first sensors and that detects a first force component causing the first movable portion and the second movable portion to rock; and

a second detection unit that includes a second sensor and that detects a second force component causing the second movable portion to rotate,

wherein the first detection unit detects the first force component based on sensor outputs of the three or more first sensors, each of the outputs being changed when external force is applied to at least one of the first movable portion and the second movable portion to allow the first movable portion to be tilted relative to the base, and

wherein the second detection unit detects the second force component based on a sensor output of the second sensor, the sensor output being changed when external force is applied to at least one of the first movable portion and the second movable portion to allow the second movable portion to rotate.

2. The force sensor according to claim 1, wherein the first movable portion and the second movable portion are arranged above the base in a vertical direction.

3. The force sensor according to claim 1, wherein

the first detection unit includes the three or more first sensors, and

the three or more first sensors are configured to emit light and detect reflected light of the light.

4. The force sensor according to claim 1, wherein

the first detection unit includes four first sensors, and

two of the four first sensors are arranged on one straight line while remaining two first sensors are arranged on another straight line orthogonal to the one straight line.

5. The force sensor according to claim 1, wherein

the support includes:

a first fixture supported by the base;

a plate spring portion that has a plate-like shape and is supported by the first fixture through a spacer to be able to undergo elastic deformation; and

a second fixture supported by the plate spring portion through a spacer,

the plate spring portion includes;

a base portion having a plate-like shape; and

a

plurality of protrusions, where the protrusions are on the same plane as the base portion and protrude from the base portion, and surfaces of the protrusions come into contact with the spacer, and,

when external force is applied to the first movable portion, a part of each of the protrusions deforms depending on a displacement of the first movable portion, the part being closer to the base portion relative to a position in contact with the spacer.

6. The force sensor according to claim 5, wherein the support includes a plurality of the plate spring portions connected to face one another with spacing formed among the plate spring portions.

7. The force sensor according to claim 1, wherein the first detection unit includes the three or more first sensors that are provided on a top surface of the base and are configured to emit light and to detect reflected light of the light,

the first detection unit calculates distances from each of the three or more first sensors to a corresponding reflector based on the sensor outputs of the three or more first sensors, and

the first detection unit calculates the angle of inclination of the first movable portion by using coordinates of the three of more first sensors and coordinates of the reflectors.

8. The force sensor according to claim 1, wherein the first detection unit includes three first sensors that are arranged at equal intervals, each interval being 120°

, in a circumferential direction on a top surface of the base.

9. The force sensor according to claim 7, wherein

the first detection unit includes four or more first sensors,

the first detection unit uses three of the first sensors as a first set, to calculate an angle of inclination of the first movable portion on the basis of coordinates of the three first sensors and the coordinates of the reflectors,

the first detection unit uses three of the first sensors as a second set in which at least one first sensor is different from the first set, to calculate an angle of inclination of the first movable portion on the basis of coordinates of the three first sensors and the coordinates of the reflectors, and

the first detection unit obtains the angle of inclination of the first movable portion by averaging the angle calculated using the first sensors of the first set and the angle calculated using the first sensors of the second set.

10. The force sensor according to claim 1, further comprising:

a first stopper restricting a rocking angle of the first movable portion and the second movable portion;

a second stopper restricting an amount of displacement of the first movable portion and the second movable portion in a direction in which the support is to be extended; and

a third stopper restricting an angle of rotation about a central axis of the second movable portion.

11. The force sensor according to claim 10, wherein

the first stopper is a portion protruding from the base toward the first movable portion, is provided at three or more positions at equal intervals in a circumferential direction about a central axis of the support, and

the first stopper has a height from the base allowing a tip of the first stopper to come into contact with the first movable portion when a load exceeding a load with which the support is elastically deformed is applied to the force sensor.

12. The force sensor according to claim 10, wherein the second stopper is a flanged portion that is provided at an upper end of a housing arranged to cover a periphery of the force sensor and protrudes toward a center, and

the second stopper has a height allowing a lower end face of the second stopper to come into contact with the second movable portion when a load exceeding a load with which the support is elastically deformed is applied to the force sensor.

13. The force sensor according to claim 10, wherein

the third stopper includes permanent magnets that are provided on, respectively, a surface of the first movable portion and a surface of the second movable portion facing each other, the permanent magnet provided on the first movable portion protrudes from the surface of the first movable portion toward the second movable portion, and

the permanent magnets provided on the second movable portion protrude from the surface of the second movable portion toward the first movable portion and are provided at positions sandwiching the permanent magnet provided on the first movable portion in a circumferential direction.

14. The force sensor according to claim 1, wherein

the joint includes a shaft passing through the second movable portion, and

a first internal passage passing through the base, a second internal passage passing through the support, and a third internal passage passing through the shaft are arranged on the same straight line.

15. The force sensor according to claim 1, wherein

wherein the first movable portion and the second movable portion are movable to be tilted relative to the base in such a manner that surfaces of the first movable portion and the second movable portion facing each other remain parallel to each other.