Overload detection device and valve drive equipment including the same

Abstract

To provide an overload detection device and valve drive equipment including the same, which enable stable detection of overload through a potentiometer.SOLUTION: An overload detection device 10 includes: a rotary member 53 that is secured to a movable member of an external device, which moves in an amount in accordance with the magnitude of a load generated in the external device, and is rotated with movement of the movable member; a potentiometer 44 configured to output an electric signal whose magnitude corresponds to the rotational angle of the rotary member 53; a detection unit 45 configured to detect generation of an overload in the external device when the electric signal from the potentiometer 44 reaches a specified magnitude; and force application means 49 for applying a force in a direction to return the rotary member 53, rotated from a reference angle, back to the reference angle.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an overload detection device for detecting an overload and a valve drive facility including the same. [Background technology]

[0002] Valve drive equipment uses a motor to raise and lower or rotate valves (including gates, etc.) (hereinafter, both "raise and lower" and "rotate" may be referred to as "move") to open and close flow paths such as pipes and waterways. When a load greater than a predetermined magnitude, i.e., an overload, occurs on the valve drive equipment, the moving valve is stopped to prevent malfunctions, etc. For this reason, valve drive equipment is equipped with an overload detection device that detects the occurrence of an overload.

[0003] Incidentally, while overload normally means a load greater than a predetermined magnitude, in this document, the concept of overload also includes a load less than a predetermined magnitude, i.e., an insufficient load. For example, in a floodgate, when the gate body suspended from the chain is positioned at a height where it does not touch the riverbed, the weight of the gate body normally acts as a load on the valve drive equipment, but if an object such as driftwood gets caught between the gate body and the riverbed, the load acting on the valve drive equipment becomes smaller than expected.

[0004] A conventional overload detection device, a specific example of which is disclosed in Patent Document 1, comprises a movable member (U-shaped plate feed 24) that moves by an amount corresponding to the magnitude of the load acting on the valve drive equipment, a sensor shaft (shaft to which actuator 28 is attached) that rotates as the movable member moves, and a microswitch or limit switch (limit switch 27) that detects the occurrence of an overload from the rotation angle of the sensor shaft. Hereinafter, microswitches and limit switches will be collectively referred to as "microswitches."

[0005] As shown in Figure 7(A), the microswitch is in the OFF state when the rotation angle of the sensor shaft is within a predetermined range, and turns ON when the rotation angle of the sensor shaft goes outside the predetermined range. Therefore, to detect overload using a microswitch, it is necessary to design various components related to the rotation of the sensor shaft so that the microswitch switches from OFF to ON (or from ON to OFF) at the timing when an overload begins to occur. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Jitszen No. 56-062457 Summary of the Invention [Problem to be solved by the invention]

[0007] To enable a common overload detection device to be used at various installation sites for valve-driven equipment (e.g., installation sites with different gate weights), the overload detection device must be designed so that the magnitude of the detected overload can be adjusted by physically adjusting various components related to the rotation of the sensor shaft (e.g., adjusting the bolt protrusion length). Furthermore, individual differences in the relationship between the load acting on the valve-driven equipment and the amount of movement of the moving components and sensor shaft will inevitably occur depending on the manufacturing precision and assembly state of each device. For this reason, too, overload detection devices are required to be designed with an adjustable overload magnitude. However, a design that allows for an adjustable overload magnitude introduces the problem of a complex structure for the overload detection device.

[0008] To solve this problem, it is possible to use a potentiometer instead of a microswitch. As shown in Figure 7(B), a potentiometer outputs an electrical signal (voltage, etc.) whose magnitude corresponds to the rotation of the sensor shaft. Therefore, when an overload begins to occur, the magnitude of the electrical signal output from the potentiometer can be set to indicate the occurrence of an overload, and there is no need to physically adjust the various components involved in the rotation of the sensor shaft. In the example shown in Figure 7(B), P1 and P2 are the magnitudes of the electrical signals corresponding to the occurrence of an overload.

[0009] Here, even though it would be ideal to have no clearance at the connection points between components, etc., it may be necessary to provide clearance at the relevant points for reasons of production accuracy, etc. As shown in Figure 8(A), if the diameter of the handle 100 connected to the sensor shaft is shorter than the distance between the left contact portion 102 and the right contact portion 103 of the movable member 101 that contact the handle 100, for example, when the movable member 101 moves to the left while the handle 100 is in contact with the right contact portion 103 but not with the left contact portion 102, as shown in Figure 8(B), the handle 100 moves to the left together with the movable member 101 and rotates the sensor shaft, but when the movable member 101 moves to the right in the same state, the handle 100 does not move and the sensor shaft does not rotate, as shown in Figure 8(C).

[0010] Furthermore, even when the movable member 101 is stopped, vibrations or the like can cause the handle 100 to move by the amount of clearance, causing the sensor shaft to rotate. In other words, when there is clearance, the movement of the movable member, which moves by an amount corresponding to the magnitude of the load, and the rotation of the sensor shaft are not always linked, and it may happen that an overload cannot be detected at the correct time. The present invention has been made in view of the above circumstances, and has an object to provide an overload detection device that can stably detect an overload using a potentiometer, and a valve drive facility equipped with the same. [Means for solving the problem]

[0011] The overload detection device of the first invention that meets the above-mentioned objective is an overload detection device that has a rotating member that is engaged with a movable member of an external device that moves an amount corresponding to the magnitude of the load generated in the external device and rotates as the movable member moves, and is equipped with a potentiometer that outputs an electrical signal of a magnitude corresponding to the rotation angle of the rotating member, a detection unit that detects the occurrence of an overload in the external device when the electrical signal output from the potentiometer reaches a predetermined magnitude, and force application means that applies a force to the rotating member that has rotated from a reference angle in a direction that returns it to the reference angle.

[0012] A second invention that meets the above-mentioned objective is a valve drive equipment that includes a power transmission mechanism that transmits the rotational force of a motor to a valve, a movable member that moves an amount corresponding to the magnitude of the load acting on the power transmission mechanism, and an overload detection device that has a rotating member that is engaged with the movable member and rotates as the movable member moves, wherein the overload detection device includes a potentiometer that outputs an electrical signal whose magnitude corresponds to the rotation angle of the rotating member, a detection unit that detects the occurrence of an overload in the external device when the electrical signal output from the potentiometer reaches a predetermined magnitude, and force applying means that applies a force to the rotating member, which has rotated from a reference angle, in a direction that returns it to the reference angle. [Effects of the Invention]

[0013] The overload detection device of the first invention comprises a potentiometer that outputs an electrical signal whose magnitude corresponds to the rotation angle of a rotating member, a detection unit that detects the occurrence of an overload in an external device when the electrical signal output from the potentiometer reaches a predetermined magnitude, and force applying means that applies a force to a rotating member that has rotated from a reference angle in a direction returning it to the reference angle, thereby making it possible to stably detect an overload using the potentiometer.

[0014] In the valve drive equipment of the second invention, the overload detection device comprises a potentiometer that outputs an electrical signal whose magnitude corresponds to the rotation angle of the rotating member, a detection unit that detects the occurrence of an overload in the external device when the electrical signal output from the potentiometer reaches a predetermined magnitude, and force application means that applies a force to the rotating member that has rotated from a reference angle in a direction returning it to the reference angle, so that overload can be detected stably using the potentiometer. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is an explanatory diagram of an overload detection device and a power transmission mechanism according to an embodiment of the present invention; [Figure 2] FIG. [Figure 3] FIG. 2 is an explanatory diagram of an overload detection device. [Figure 4] 1A and 1B are explanatory diagrams of a cam and a torsion spring of an overload detection device, respectively. [Figure 5] FIG. 10 is an explanatory diagram showing a state in which the cam is rotated. [Figure 6] FIG. 10 is an explanatory diagram of a modified example of the overload detection device. [Figure 7] 10A and 10B are explanatory diagrams of the output signals of a microswitch and a potentiometer, respectively. [Figure 8] 10(A) to 10(C) are explanatory diagrams of the clearance between the movable member and the handle, respectively.

[0016] Next, embodiments of the present invention will be described with reference to the accompanying drawings to facilitate understanding of the present invention. 1 to 3, an overload detection device 10 according to one embodiment of the present invention is used in valve drive equipment that includes a motor 11, a power transmission mechanism 12 that transmits the rotational force of the motor 11 to a valve (not shown), and a movable member 13 that moves an amount corresponding to the magnitude of the load acting on the power transmission mechanism 12, and is a device that detects the occurrence of an overload in the power transmission mechanism 12. A detailed description will be given below.

[0017] 1 and 2, the power transmission mechanism 12 includes a gear 15 to which the rotational force of the motor 11 is applied via an input shaft 14, a sun gear 17 rotatably attached to a sun shaft 16 and meshing with the gear 15, and a planetary gear 19 rotatably attached to a planetary shaft 18. The center of the gear 15 is fixed to the input shaft 14, the sun gear 17 is rotatably attached to the sun shaft 16 via a bearing 20, and the planetary gear 19 is keyed to the planetary shaft 18.

[0018] The input shaft 14, sun shaft 16, and planetary shaft 18 are arranged in parallel, and the gear 15, sun gear 17, and planetary gear 19 are arranged on the same plane. Note that in Figures 1 and 2, the positions of the input shaft 14, gear 15, output shaft 30, and gear 31, which will be described later, are depicted differently in Figures 1 and 2, but this is to make it easier to understand the meshing of the gears, etc., and in reality, they are arranged as shown in Figure 2.

[0019] The sun shaft 16 has both ends fitted and fixed in the supports 22 and 23. In contrast, the axial center position of the planetary shaft 18 is not fixed and is movable. A plate-shaped rotating member 24 is rotatably attached to the sun shaft 16. The rotating member 24 is formed in a fan shape when viewed along the axis of the sun shaft 16, and has a tooth portion 25 consisting of a plurality of teeth in an arc region on the tip side of the rotating member 24.

[0020] The sun shaft 16 penetrates the base side of the rotating member 24, and the rotating member 24 is rotatable around the axis of the sun shaft 16. The toothed portion 25 (the plurality of teeth of the toothed portion 25) is formed along the outer edge of an imaginary circle (hereinafter referred to as "imaginary circle T") centered around the rotation center of the rotating member 24 (the axis of the sun shaft 16). The central portion of the planetary shaft 18 (a position having a certain distance from the rotation center of the rotating member 24) penetrates the tip side of the rotating member 24, and the other end portion is inserted into the center of the planetary gear 26. In this embodiment, the rotating member 24 is rotatably attached to the planetary shaft 18 via a bearing 27, and the planetary gear 26 is keyed to the planetary shaft 18.

[0021] A sun gear 28 meshing with a planetary gear 26 is rotatably attached to the sun shaft 16 via a bearing 29. A gear 31 meshing with the sun gear 28 is fixed to an output shaft 30 that outputs a rotational force toward the valve. In this embodiment, the axial positions of the input shaft 14 and the output shaft 30 are fixed.

[0022] The planetary shaft 18 does not have a fixed axial position, and the planetary gears 19 and 26 are meshed with the sun gears 17 and 28, respectively. Therefore, the planetary gears 19 and 26 can revolve around the sun gears 17 and 28 together with the planetary shaft 18 while rotating around the planetary shaft 18, and the rotating member 24 rotates around the axial center of the sun shaft 16 as the planetary gears 19 and 26 and the planetary shaft 18 revolve (move) around the sun gears 17 and 28.

[0023] In addition, in this embodiment, as shown in Figures 1 and 2, the movable member 13 is rod-shaped and is rotatably supported by a bearing 35 fixed to the support 34 and bearings 37 and 38 attached to a support 36 arranged at a position some distance from the support 34 (in this embodiment, to the left of the support 34), and is arranged so as to form an angle of 90 degrees with respect to the sun axis 16, etc.

[0024] Bearing 37 is disposed to the left of bearing 38 with a gap therebetween. A spring member 33 (a coil spring in this embodiment) is attached to movable member 13, with its left end in contact with bearing 37 and its right end in contact with bearing 38. The axis of spring member 33 is disposed so as to align with the axis of movable member 13.

[0025] While bearing 35 is fixed to support body 34, bearings 37 and 38 are movable relative to support body 36. Support body 36 is provided with a left limit position where bearing 37 can move to the left and a right limit position where bearing 38 can move to the right. Movable member 13 is movable left and right (toward one side and the other side in the axial direction of movable member 13) relative to supports 34 and 36.

[0026] Bearing 37 moves left and right integrally with movable member 13 in an area to the right of the left limit position, and bearing 38 moves left and right integrally with movable member 13 in an area to the left of the right limit position. With movable member 13 disposed at the reference position, bearing 37 is disposed at the left limit position, and bearing 38 is disposed at the right limit position. As shown in FIG. 1, the movable member 13 has a locking portion 39 that meshes with the teeth 25 of the rotating member 24 between the portion supported by the bearing 38 and the portion supported by the bearing 35.

[0027] The rod-shaped movable member 13 is disposed along a tangent line (hereinafter referred to as "tangent line S") to the imaginary circle T. The locking portion 39 is composed of a plurality of disk-shaped protruding pieces provided on the movable member 13 at equal intervals in the axial direction of the movable member 13, and the locking portion 39 as a whole is disposed along the tangent line S. When the motor 11 is stopped, in principle, no load is applied to the power transmission mechanism 12. Hereinafter, the position of the movable member 13 when no load is applied to the power transmission mechanism 12 will be referred to as the reference position, and the angular position of the rotating member 24 in this state will be referred to as the reference angular position.

[0028] When the motor 11 rotates in the direction to open or close the valve, a load is generated in the power transmission mechanism 12 . When the motor 11 is rotating in the direction to open the valve and the load acting on the power transmission mechanism 12 reaches a predetermined magnitude or greater, the rotating member 24 rotates clockwise from the reference angle position around the axis of the sun shaft 16, and the movable member 13 is exerted with force from the tooth portion 25 moving clockwise, and moves linearly to the right together with the bearing 37 along the tangent line S (locking portion 39) against the elastic force of the spring member 33.

[0029] As a result, bearing 37 moving to the right contracts spring member 33, and the contracted spring member 33 applies a leftward force to movable member 13 via bearing 37, and movable member 13 applies a counterclockwise force to rotating member 24. The amount of movement (movement length) of movable member 13 to the right increases as the load acting on power transmission mechanism 12 increases.

[0030] On the other hand, when the motor 11 is rotating in the direction to close the valve and the load acting on the power transmission mechanism 12 reaches a predetermined magnitude or greater, the rotating member 24 rotates counterclockwise from the reference angle position around the axis of the sun shaft 16, and the movable member 13 is exerted with force from the tooth portion 25 moving counterclockwise, and moves linearly to the left together with the bearing 38 along the tangent line S against the elastic force of the spring member 33.

[0031] As a result, bearing 38 moving to the left contracts spring member 33, and the contracted spring member 33 applies a rightward force to movable member 13 via bearing 38, and movable member 13 applies a clockwise force to rotating member 24. The amount of movement (movement length) of movable member 13 to the left increases as the load acting on power transmission mechanism 12 increases.

[0032] In this embodiment, the external device in which the overload detection device 10 is used is configured by the motor 11, the power transmission mechanism 12, the movable member 13, etc. (i.e., the valve drive equipment excluding the overload detection device 10). Therefore, the movable member 13 moves an amount corresponding to the magnitude of the load occurring in the external device. It should be noted that a movable member made of a rack gear can be used instead of the movable member 13, and in that case, the locking portion is formed by a plurality of teeth of the rack gear.

[0033] The movable member 13 also has annular portions 40 and 41 that are spaced apart from each other between the locking portion 39 and the portion supported by the bearing 35. The annular portions 40 and 41 are each provided so that their respective axes coincide with the axis of the movable member 13. 1 and 3, the overload detection device 10 includes a handle 42 whose tip is disposed between the annular portions 40 and 41 and engaged with the annular portions 40 and 41 (i.e., the movable member 13). The state in which the tip of the handle 42 is engaged with the annular portions 40 and 41 (in this embodiment, the state in which the handle 42 is disposed between the annular portions 40 and 41) is maintained even when the movable member 13 moves left and right.

[0034] The base side of the handle 42 is fixed to one end of a rod 43 arranged parallel to the planetary shaft 18, and the tip of the handle 42 is arranged at a position away from the planetary shaft 18 and from an extension of the planetary shaft 18. The rod 43 is provided rotatably, and the other end of the rod 43 is connected to a potentiometer 44 as shown in FIG. A control means 45 that controls the operation of the motor 11 is connected to the potentiometer 44, and the control means 45 can acquire an electric signal (a voltage signal in this embodiment) output from the potentiometer 44. The potentiometer 44 outputs an electric signal whose magnitude corresponds to the rotation angle of the rod 43.

[0035] As shown in Figures 3, 4(A), and 4(B), a cam 46 that rotates integrally with the bar 43 is attached to the bar 43. The cam 46 is fan-shaped when viewed in the axial direction of the bar 43, and a torsion spring (an example of a spring member) 49 is disposed near the cam 46 so as to sandwich the cam 46 between two arms (straight portions) 47 and 48. A bolt 51 that positions the coil portion 50 is inserted into a coil portion 50 provided in the torsion spring 49, and the bolt 51 is fixed to a fixing portion 52.

[0036] In this embodiment, the rotating member 53 is engaged with the annular portions 40, 41 (i.e., the movable member 13) and rotates as the movable member 13 moves, and is made up of the handle 42, the rod 43, the cam 46, etc. The rotation angle of the rotating member 53 when the motor 11 is stopped and no load is applied to the power transmission mechanism 12 is set as a reference angle, and in a state where the rotating member 53 is disposed at the reference angle, the torsion spring 49 does not substantially apply a force to the cam 46 to rotate it.

[0037] "Substantially no force is being applied to cam 46 to rotate cam 46" means that no force is being applied to cam 46 from torsion spring 49, and that the magnitude of the clockwise force being applied to cam 46 from arm 47 and the magnitude of the counterclockwise force being applied to cam 46 from arm 48 are substantially equal. The rotating member 53 rotates clockwise (in this embodiment, spins on its own axis) around the rod 43 when the movable member 13 moves to the left, and rotates counterclockwise (in this embodiment, spins on its own axis) around the rod 43 when the movable member 13 moves to the right.

[0038] 5, when the rotating member 53 (cam 46) rotates clockwise from a reference angle, the cam 46 applies a clockwise force to the arm 48 (the arm 48 receives a clockwise force from the cam 46), and the arm 48 rotates clockwise while applying a counterclockwise force to the cam 46. At this time, the shapes and arrangements of the cam 46 and the torsion spring 49 are adjusted so that no force is applied from the arm 47 to the cam 46 (or so that a force is applied from the arm 47 to the cam 46, but the direction or magnitude of the force is such that it does not substantially rotate the cam 46).

[0039] When rotating member 53 rotates counterclockwise from the reference angle, cam 46 applies a counterclockwise force to arm 47 (arm 47 receives a counterclockwise force from cam 46), and arm 47 rotates counterclockwise while applying a clockwise force to cam 46. At this time, the shapes and arrangements of cam 46 and torsion spring 49 are adjusted so that no force is applied from arm 48 to cam 46 (or so that a force is applied from arm 48 to cam 46, but the direction or magnitude of the force is such that it does not substantially rotate cam 46).

[0040] Therefore, the force applying means that applies a force in a direction returning rotational member 53 that has rotated from the reference angle to the reference angle can be configured to include torsion spring 49. In this embodiment, torsion spring 49 corresponds to a spring member that elastically deforms upon receiving a force in the rotational direction of rotational member 53 from rotational member 53 that has rotated from the reference angle, and applies a restoring force to rotational member 53.

[0041] When the electric signal output from potentiometer 44 reaches a predetermined magnitude, control means 45 detects the occurrence of an overload in power transmission mechanism 12 (external device) and stops the operation of motor 11. In this embodiment, control means 45 corresponds to the detection unit. Also, in this embodiment, control means 45 detects both an overload when the valve is moving in the opening direction and an overload when the valve is moving in the closing direction.

[0042] Specifically, when the electrical signal output from potentiometer 44 becomes equal to or less than a predetermined Q1, control means 45 detects that an overload has occurred while the valve is moving in the closing direction, and when the electrical signal output from potentiometer 44 becomes equal to or greater than a predetermined Q2 (Q2 > Q1), control means 45 detects that an overload has occurred while the valve is moving in the opening direction. The magnitudes of Q1 and Q2 are adjusted by settings for control means 45. Therefore, by adjusting the values ​​of Q1 and Q2, the overload detection device 10 can be used in different valve drive equipment and adapted to different installation sites.

[0043] Here, the width (length along the axis of the movable member 13) of the tip of the handle 42 arranged between the annular portions 40 and 41 is shorter than the distance between the annular portions 40 and 41, and the tip of the handle 42 does not come into contact with both the annular portions 40 and 41 at the same time. In this regard, in this embodiment, when the rotating member 53 is rotated from the reference angle, the tip of the handle 42 is stably maintained in contact with either the annular portion 40 or 41 due to the restoring force of the torsion spring 49.

[0044] Therefore, the change in the magnitude of the electrical signal output from the potentiometer 44 is stably synchronized with the change in the amount of movement of the movable member 13 from the reference position, and as a result, the control means 45 can reliably detect the occurrence of an overload.

[0045] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and all changes in conditions that do not depart from the gist of the present invention are within the scope of application of the present invention. For example, the overload detection device may be designed to detect only an overload when the valve is moving in the opening direction or only an overload when the valve is moving in the closing direction.

[0046] In addition, an overload detection device or the like can be designed so that the detection unit can detect when the load acting on the external mechanism falls below a predetermined value. Furthermore, the force applying means does not need to include a spring member, and may, for example, be a pusher that applies force to the rotating member. Furthermore, if the force applying means includes a spring member, the spring member is not limited to a torsion spring. For example, as shown in FIG. 6, the spring member may be a coil spring 55, 56 that applies a force to the cam 46 that has rotated from the reference angle in a direction returning the cam 46 to the reference angle.

[0047] Furthermore, it goes without saying that the structure of the rotating member that rotates due to the movement of the movable member is not limited to the above embodiment, and the design related to the engagement of the rotating member with the movable member is also not limited to the above embodiment. [Explanation of symbols]

[0048] 10: Overload detection device, 11: Motor, 12: Power transmission mechanism, 13: Movable member, 14: Input shaft, 15: Gear, 16: Sun shaft, 17: Sun gear, 18: Planet shaft, 19: Planet gear, 20: Bearing, 22, 23: Support, 24: Rotating member, 25: Tooth portion, 26: Planet gear, 27: Bearing, 28: Sun gear, 29: Bearing, 30: Output shaft, 31: Gear, 3 3: spring member, 34: support, 35: bearing, 36: support, 37, 38: bearing, 39: engaging portion, 40, 41: annular portion, 42: handle, 43: rod, 44: potentiometer, 45: control means, 46: cam, 47, 48: arm portion, 49: torsion spring, 50: coil portion, 51: bolt, 52: fixed portion, 53: rotating member, 55, 56: coil spring

Claims

1. An overload detection device having a rotating member that is engaged with a movable member of an external device, the rotating member moving by an amount corresponding to the magnitude of a load generated in the external device, and that rotates with the movement of the movable member, a potentiometer that outputs an electric signal having a magnitude corresponding to the rotation angle of the rotary member; a detection unit that detects an occurrence of an overload in the external device when the electrical signal output from the potentiometer reaches a predetermined magnitude; and a force applying means for applying a force to the rotating member that has rotated from a reference angle in a direction to return the rotating member to the reference angle.

2. 2. The overload detection device according to claim 1, wherein the force applying means includes a spring member that elastically deforms upon receiving a force from the rotating member in the rotational direction of the rotating member rotated from the reference angle, and applies a restoring force to the rotating member.

3. 3. The overload detector according to claim 2, wherein the spring member is a torsion spring whose arm receives a force from the rotating member.

4. A valve drive facility comprising: a power transmission mechanism that transmits the rotational force of a motor to a valve; a movable member that moves an amount corresponding to the magnitude of the load acting on the power transmission mechanism; and an overload detection device having a rotating member that is engaged with the movable member and rotates due to the movement of the movable member, The overload detection device a potentiometer that outputs an electric signal having a magnitude corresponding to the rotation angle of the rotary member; a detection unit that detects an occurrence of an overload in the external device when the electrical signal output from the potentiometer reaches a predetermined magnitude; a force applying means for applying a force to the rotating member that has rotated from a reference angle in a direction that returns the rotating member to the reference angle.

5. 5. The valve drive equipment according to claim 4, wherein the force applying means includes a spring member that elastically deforms upon receiving a force from the rotating member in the rotational direction of the rotating member that has rotated from the reference angle, and applies a restoring force to the rotating member.

6. 6. The valve drive system according to claim 5, wherein the spring member is a torsion spring whose arm receives a force from the rotating member.

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