Electric gas flow control valve

Abstract

To provide a flow rate control valve for moving a needle valve body 2 in an axial direction via a motion conversion mechanism by using a motor 3 in which the motion conversion mechanism comprises a guide member 5 which has a long hole 51 extending in the axial direction in which a fixed cam pin 21 is slidably engaged with the needle valve body 2 and which is connected to the motor 3, and a cam body 6 in which a spiral cam part 61 engaged with the cam pin 21 is formed and which is whirl-stopped with respect to a valve casing 1, the long hole 51 is released in a reciprocation direction at a side end part 5a in the reciprocation direction of the guide member 5 with a direction in which the needle valve body 2 approaches a valve seat 11 as the reciprocation direction, out of the axial direction, and the cam pin 21 is inserted into the long hole 51 from the reciprocation direction side, and also in which a zero seek performed by making the motor 3 step out can be accurately performed.SOLUTION: There is arranged a guide member deformation regulation member 8 having a female-type fitting part 81 to which a side end part 5a in a reciprocation direction of a guide member 5 is internally fit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electric gas flow control valve including a needle valve element that moves axially toward and away from a valve seat in a valve casing, a stepping motor, and a motion conversion mechanism that moves the needle valve element axially by rotation of the stepping motor. [Background technology]

[0002] Conventionally, as an electric gas flow control valve of this type, a motion conversion mechanism has been known which includes a cam pin fixed to a needle valve body, a guide member formed with an elongated hole extending in the axial direction in which the cam pin slidably engages, and a cylindrical cam body formed with a cam groove which serves as a spiral cam portion in which the cam pin engages, and one of the guide member and the cam body is connected to a stepping motor and the other is prevented from rotating relative to the valve casing (see, for example, Patent Documents 1 and 2).

[0003] In a first type electric gas flow control valve in which a guide member is connected to a stepping motor, the direction in the axial direction in which the needle valve element approaches the valve seat is defined as the forward direction, the direction in which it moves away from the valve seat as the backward direction, the rotation direction of the stepping motor that moves the needle valve element in the forward direction as the forward direction, and the rotation direction of the stepping motor that moves the needle valve element in the backward direction as the reverse direction, the needle valve element is moved in the forward direction and the backward direction via the cam groove and the cam pin by rotation of the cam element via the guide member caused by rotation of the stepping motor in the forward direction and the reverse direction. In a second type electric gas flow control valve in which a cam body is connected to a stepping motor, the needle valve element is moved in the forward direction and the backward direction via the cam groove and cam pin by rotation of the cam body caused by rotation of the stepping motor in the forward direction and the reverse direction.

[0004] Furthermore, in the first type of electric gas flow control valve, since the guide member is connected to the stepping motor at the end on the return movement direction side, a long hole is opened in the direction of the forward movement at the end on the forward movement direction side of the guide member, and a cam pin is inserted into the long hole from the forward movement direction side. Also, in the second type of electric gas flow control valve, since the cam body is connected to the stepping motor at the end on the return movement direction side, a cam groove is opened in the direction of the forward movement at the end on the forward movement direction side of the cam body, and a cam pin is inserted into the cam groove from the forward movement direction side.

[0005] By the way, in both the first and second types of electric gas flow control valves, with the needle valve body moved to the stroke end on the forward movement direction side, the stepping motor is demagnetized to perform homing. Here, in the first type of electric gas flow control valve, since the long hole is opened in the direction of the forward movement at the end on the forward movement direction side of the guide member, when the stepping motor is demagnetized, the guide member is deformed by the force applied via the cam pin to the side edge of the long hole such that the hole width of the long hole gradually widens toward the end on the forward movement direction side of the guide member, and the homing accuracy deteriorates. Also, in the second type of electric gas flow control valve, since the cam groove is opened in the direction of the forward movement at the end on the forward movement direction side of the cam body, when the stepping motor is demagnetized, the cam body is deformed by the force applied via the cam pin to the side edge of the cam groove such that the groove width of the cam groove gradually widens toward the end on the forward movement direction side of the cam body, and the homing accuracy deteriorates.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In view of the above points, an object of the present invention is to provide an electric gas flow control valve capable of accurately performing homing by detuning a stepping motor.

Means for Solving the Problems

[0008] In order to solve the above problems, a first invention of the present application is characterized in that, in the electric gas flow control valve of the first type, a deformation restricting member for a guide member having a female fitting portion into which an end portion on the forward movement side of the guide member is fitted is provided in the valve casing. Further, a second invention of the present application is characterized in that, in the electric gas flow control valve of the second type, a deformation restricting member for a cam body having a female fitting portion into which an end portion on the forward movement side of the cam body is fitted is provided in the valve casing.

[0009] According to the first invention, when detuning the stepping motor, the deformation restricting member for the guide member can suppress the deformation of the guide member such that the hole width of the long hole gradually widens toward the end portion on the forward movement side of the guide member due to the force applied via the cam pin to the side edge of the long hole. Similarly, according to the second invention, the deformation restricting member for the cam body can suppress the deformation of the cam body such that the groove width of the cam groove gradually widens toward the end portion on the forward movement side of the cam body due to the force applied via the cam pin to the side edge of the cam groove. Therefore, in either the first invention or the second invention, homing by detuning the stepping motor can be accurately performed.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Best Mode for Carrying Out the Invention

[0011] Referring to FIGS. 1 and 2, the electric gas flow control valve according to the first embodiment of the present invention includes a frustum-shaped needle valve body 2 that approaches and separates axially toward a valve seat 11 in a valve casing 1, a stepping motor 3, and a motion conversion mechanism that axially moves the needle valve body 2 by the rotation of the stepping motor 3. In the valve casing 1, a primary gas chamber 12 communicating with a gas inlet 12a and a secondary gas chamber 13 communicating with a gas outlet 13a are provided. And a valve seat member 4 having a valve seat 11 that partitions the primary gas chamber 12 and the secondary gas chamber 13 is mounted in the secondary gas chamber 13.

[0012] Hereinafter, the direction in which the needle valve body 2 approaches the valve seat 11 in the axial direction is referred to as the forward movement direction, the direction in which it separates from the valve seat 11 is referred to as the reverse movement direction, the rotation direction of the stepping motor 3 that moves the needle valve body 2 in the forward movement direction is referred to as the normal rotation direction, and the rotation direction of the stepping motor 3 that moves the needle valve body 2 in the reverse movement direction is referred to as the reverse rotation direction for explanation.

[0013] Referring also to FIG. 3, the motion conversion mechanism includes a cam pin 21 fixed to the needle valve body 2, a cylindrical guide member 5 having an axially extending long hole 51 with which the cam pin 21 slidably engages, and a cylindrical cam body 6 having a spiral cam portion 61 with which the cam pin 21 engages through the long hole 51. The stepping motor 3 is disposed on the outer surface of the end portion of the valve casing 1 on the reverse movement direction side.

[0014] The guide member 5 is connected to the stepping motor 3 at the end on the return movement direction side. Specifically, a non-circular connecting hole 52a is formed in a boss portion 52 protruding from the end on the return movement direction side of the guide member 5, and a non-circular shaft portion 32a of a connector 32 connected to the output shaft 31 of the stepping motor 3 is fitted into the connecting hole 52a. Thereby, the guide member 5 is connected to the output shaft 31 of the stepping motor 3 via the connector 32, and the guide member 5 rotates with the rotation of the stepping motor 3. Further, the long hole 51 formed in the guide member 5 is open in the forward movement direction at the end 5a on the forward movement direction side of the guide member 5. Then, the cam pin 21 is inserted into the long hole 51 from the forward movement direction side.

[0015] The needle valve body 2 has a cylindrical portion 22 extending in the return movement direction and inserted into the guide member 5. And a cam pin 21 protrudes radially outward at the end on the return movement direction side of the cylindrical portion 22. Further, a large-diameter portion 21a is formed at the base of the cam pin 21, and the large-diameter portion 21a is slidably engaged with a long hole 51 formed in the guide member 5. Therefore, the needle valve body 2 is axially movable with respect to the guide member 5 and is connected so as to rotate together.

[0016] The cam body 6 is prevented from rotating with respect to the valve casing 1. Specifically, the cam body 6 is prevented from rotating with respect to the valve casing 1 by engaging a rib 62 protruding from the outer peripheral surface of the cam body 6 with a groove 14 formed in the inner peripheral surface of the valve casing 1. The cam portion 61 provided on the cam body 6 is such that the cam pin 21 can abut from the return movement direction side, and is composed of a spiral inclined side inclined in the forward movement direction toward the normal rotation direction. Further, a spring member 7 that biases the cam pin 21 in the forward movement direction toward the cam portion 61 is provided. Incidentally, the cam portion 61 can also be configured as a spiral cam groove. In this case, the spring member 7 is unnecessary. Further, in order to reduce the number of parts, the cam body 6 is integrally formed with the valve seat member 4.

[0017] According to the above configuration, the rotation of the cam pin 21 through the guide member 5 due to the forward and reverse rotations of the stepping motor 3 causes the needle valve body 2 to move in the forward movement direction and the reverse movement direction via the cam portion 61 and the cam pin 21.

[0018] By the way, due to the slip of the stepping motor 3, the correlation between the rotation phase of the stepping motor 3 and the axial position of the needle valve body 2 may be disrupted. Therefore, the needle valve body 2 is moved to the stroke end in the forward movement direction at an appropriate timing, and in this state, the stepping motor 3 is detuned to perform homing. However, since the long hole 51 is open in the forward movement direction at the end portion 5a on the forward movement side of the guide member 5, when the stepping motor 3 is detuned, the force applied via the cam pin 21 to the side edge of the long hole 51 may cause the guide member 5 to deform such that the hole width of the long hole 51 gradually expands toward the end portion 5a on the forward movement side of the guide member 5. And when such deformation occurs, the origin position of the stepping motor 3 varies and the accuracy of homing deteriorates.

[0019] Therefore, a deformation restricting member 8 for the guide member having a female fitting portion 81 into which the end portion 5a on the forward movement side of the guide member 5 is fitted is provided in the valve casing 1. In the present embodiment, a concave hole in which the end portion 5a on the forward movement side of the guide member 5 is fitted and the valve seat 11 serves as the bottom of the hole is formed in the valve seat member 4, and this concave hole constitutes the female fitting portion 81. And the deformation restricting member 8 is integrated with the valve seat member 4. type According to the above configuration, when the stepping motor 3 is detuned, the deformation restricting member 8 for the guide member can suppress the guide member 5 from deforming such that the hole width of the long hole 51 gradually expands toward the end portion 5a on the forward movement side of the guide member 5 due to the force applied via the cam pin 21 to the side edge of the long hole 51. Therefore, homing by detuning the stepping motor 3 can be accurately performed.

[0020] According to the above configuration, when the stepping motor 3 is detuned, the deformation restricting member 8 for the guide member can suppress the guide member 5 from deforming such that the hole width of the long hole 51 gradually expands toward the end portion 5a on the forward movement side of the guide member 5 due to the force applied via the cam pin 21 to the side edge of the long hole 51. Therefore, homing by detuning the stepping motor 3 can be accurately performed.

[0021] Next, the electric gas flow control valve according to the second embodiment of the present invention shown in FIG. 4 and below will be described. Incidentally, the same members and parts as those of the first embodiment are denoted by the same reference numerals as above. The main difference between the second embodiment and the first embodiment is that the guide member 5 is prevented from rotating with respect to the valve casing 1, and the cam body 6 is connected to the stepping motor 3. Incidentally, the guide member 5 is integrally formed with the valve seat member 4 in order to reduce the number of parts. That is, a pair of guide members 5, 5 extending in the reciprocating direction along both outer sides around the cylindrical cam body 6 are integrally formed on the valve seat member 4. Further, each guide member 5 is formed with a long hole 51 extending in the axial direction.

[0022] The cam body 6 is connected to the stepping motor 3 at the end on the reciprocating direction side. Specifically, a non-circular cross-section connecting hole 63a is formed in a boss portion 63 protruding from the end on the reciprocating direction side of the cam body 6, and a non-circular cross-section shaft portion 32a of a connector 32 connected to the output shaft 31 of the stepping motor 3 is fitted into the connecting hole 63a. Thereby, the cam body 6 is connected to the output shaft 31 of the stepping motor 3 via the connector 32, and the cam body 6 rotates with the rotation of the stepping motor 3.

[0023] A spiral cam groove 61' with which a cam pin 21 fixed to the needle valve body 2 engages is formed in the cam body 6. This cam groove 61' is open in the forward movement direction at the end 6a on the forward movement direction side of the cam body 6. Then, the cam pin 21 is inserted into the cam groove 61' from the forward movement direction side. Further, the cam pin 21 engages with the long hole 51 formed in the guide member 5 through the cam groove 61'. According to this, with the rotation of the cam body 6 due to the forward rotation and reverse rotation of the stepping motor 3, the needle valve body 2 moves in the forward movement direction and the reverse movement direction via the cam groove 61' and the cam pin 21.

[0024] Incidentally, since the cam groove 61' is open in the forward movement direction at the end 6a on the forward movement direction side of the cam body 6, when the stepping motor 3 is demagnetized with the needle valve body 2 moved to the stroke end in the forward movement direction, the cam body 6 may be deformed by the force applied via the cam pin 21 to the side edge of the cam groove 61' such that the groove width of the cam groove 61' gradually widens toward the end 6a on the forward movement direction side of the cam body 6. When such deformation occurs, the origin position of the stepping motor 3 varies and the accuracy of homing deteriorates.

[0025] Therefore, a deformation restricting member 9 for the cam body having a female fitting portion 91 into which the end 6a on the forward movement direction side of the cam body 6 is fitted is provided in the valve casing 1. In the present embodiment, a concave hole in which the end 6a on the forward movement direction side of the cam body 6 is fitted and having the valve seat 11 as the bottom of the hole is formed in the valve seat member 4, and the female type fitting portion 91 is constituted by this concave hole. And the deformation restricting member 9 is integrated with the valve seat member 4.

[0026] According to the above configuration, when the stepping motor 3 is demagnetized, the deformation of the cam body 6 such that the hole width of the cam groove 61' gradually widens toward the end 6a on the forward movement direction side of the cam body 6 due to the force applied via the cam pin 21 to the side edge of the cam groove 61' can be suppressed by the deformation restricting member 9 for the cam body. Therefore, homing can be accurately performed by demagnetizing the stepping motor 3.

[0027] As described above, the embodiments of the present invention have been described with reference to the drawings, but the present invention is not limited thereto. For example, in the above embodiment, the deformation restricting members 8 and 9 for the guide member and the cam body are integrated with the valve seat member 4, but it is also possible to provide these deformation restricting members 8 and 9 separately and independently from the valve seat member 4 in the valve casing 1.

Explanation of Reference Numerals

[0028] 1... Valve casing, 11... Valve seat, 2... Needle valve body, 21... Cam pin, 3... Stepping motor, 5... Guide member, 5a... End portion of the guide member on the forward movement direction side, 51... Long hole, 6... Cam body, 6a... End portion of the cam body on the forward movement direction side, 61... Cam portion, 61´... Cam groove, 8... Deformation restricting member for the guide member, 9... Deformation restricting member for the cam body, 81, 91... Female type fitting portion.

Claims

1. An electric gas flow control valve comprising a needle valve body that approaches and separates axially toward a valve seat within a valve casing, a stepping motor, and a motion conversion mechanism that moves the needle valve body axially by rotation of the stepping motor, wherein, in the axial direction, the direction in which the needle valve body approaches the valve seat is the forward stroke direction, the direction in which it separates from the valve seat is the return stroke direction, the rotation direction of the stepping motor that moves the needle valve body in the forward stroke direction is the normal rotation direction, and the rotation direction of the stepping motor that moves the needle valve body in the return stroke direction is the reverse rotation direction, the motion conversion mechanism includes a cam pin fixed to the needle valve body, a guide member connected to the stepping motor in which a long hole extending axially is formed with which the cam pin slidably engages, and a cylindrical cam body that is non-rotatable with respect to the valve casing and in which a spiral cam portion with which the cam pin engages is formed, and is configured such that rotation of the cam pin via the guide member due to rotation of the stepping motor in the normal rotation direction and the reverse rotation direction moves the needle valve body in the forward stroke direction and the return stroke direction via the cam portion and the cam pin, the guide member is connected to the stepping motor at the end on the return stroke direction side, and at the end on the forward stroke direction side of the guide member, the long hole is open in the forward stroke direction and the cam pin is inserted into the long hole from the forward stroke direction side, characterized in that a deformation restricting member for the guide member that has a female fitting portion into which the end on the forward stroke direction side of the guide member is fitted and suppresses deformation of the guide member such that the hole width of the long hole gradually widens toward the end on the forward stroke direction side of the guide member is provided within the valve casing.

2. An electric gas flow control valve comprising a needle valve body that approaches and separates axially toward a valve seat within a valve casing, a stepping motor, and a motion conversion mechanism that moves the needle valve body axially by rotation of the stepping motor, wherein, in the axial direction, the direction in which the needle valve body approaches the valve seat is the forward stroke direction, the direction in which it separates from the valve seat is the return stroke direction, the rotation direction of the stepping motor that moves the needle valve body in the forward stroke direction is the normal rotation direction, and the rotation direction of the stepping motor that moves the needle valve body in the return stroke direction is the reverse rotation direction, The motion conversion mechanism includes a cam pin fixed to the needle valve body, a guide member that is rotationally fixed to the valve casing and has an axially extending long hole in which the cam pin is slidably engaged, and a cylindrical cam body connected to the stepping motor and having a spiral cam groove in which the cam pin is engaged. The rotation of the cam body due to the forward and reverse rotations of the stepping motor is configured to move the needle valve body in the forward and reverse directions via the cam groove and the cam pin. The cam body is connected to the stepping motor at the end on the reverse movement direction side, and the cam groove is open in the forward movement direction at the end on the forward movement direction side of the cam body, and the cam pin is inserted into the cam groove from the forward movement direction side. An electric gas flow rate control valve characterized in that a deformation restricting member for the cam body is provided in the valve casing to suppress deformation of the cam body such that a female fitting portion into which the end portion on the forward movement direction side of the cam body is fitted is provided, and the hole width of the cam groove gradually widens toward the end portion on the forward movement direction side of the cam body.

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