Valve body drive mechanism

Abstract

To provide a valve body drive device which enables a resin lead screw to be supported at both ends so as to enable reduction of a frictional load and to maintain the rotational axis alignment.SOLUTION: A valve body drive device comprises: a lead screw 3 which directly transmits torque from an output shaft 23 of a stepping motor 2; a carriage 4 comprising a linear feed section 40 which moves linearly along an output axis R by engaging with a part of the lead screw 3, and a pair of parallel arm portions 41t that extends from the linear feed section 40 toward a valve body 6; an axial support guide 5 which is provided with insertion holes to prevent rotation of the pair of arm portions 41t and which is movable relative to the carriage 4; a valve guide 61 configured to integrally move the valve body 6 and the carriage 4; and a coil spring 7 arranged between the valve guide 61 and the axial support guide 5. The distal end portion 31 of the lead screw 3 is in contact with the axial support receiving portion 53 of the axial support guide 5 with a minimal contact area.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a valve element drive mechanism that converts the rotational output of an electric motor into linear motion to move a valve element back and forth in a linear direction. [Background technology]

[0002] Conventionally, a valve body drive mechanism that blocks a gas flow port when necessary to cut off gas flow has been known to include a linear motion mechanism in which the rotational power from the output shaft of an electric motor is converted into a linear motion conversion mechanism to move the valve body back and forth in a linear direction to close and open the gas flow port. Such a valve body drive mechanism is disclosed in, for example, Patent Document 1.

[0003] This disclosed invention uses a lead screw made of metal with high dimensional accuracy to reduce the friction load of the linear feed section, and requires the use of expensive ball bearings to maintain the axis of rotation of the metallic lead screw and reduce the friction load caused by the axial load. Meanwhile, in view of the above-mentioned drawbacks, an invention has been disclosed in Patent Document 2 in which the ball bearing is eliminated and the outer periphery of the lead screw is made of a resin material.

[0004] This uses a metal round bar as the shaft, with a screw section made of resin attached to its outer periphery.The rotational force (torque) is transmitted by penetrating the rotor shaft with either the outer periphery resin layer or just the shaft. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2005-233203 [Patent Document 2] Patent Publication 2014-190455 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the configuration of the invention disclosed in Patent Document 1, the lead screw is machined to high-precision dimensions and is made of a metal that has low friction resistance but is expensive.

[0007] In addition, to reduce friction loss in the lead screw bearing, materials with the lowest possible friction coefficient are used. In particular, since a load is also applied in the direction of the rotation axis when the valve body is in operation, the bearing on the valve body side must also reduce friction caused by thrust load (load in the direction of the rotation axis). For this reason, ball bearings were used in conventional examples. The need to use a highly accurate metal lead screw and expensive ball bearings posed a challenge in reducing manufacturing costs.

[0008] On the other hand, the disclosed invention of Patent Document 2 uses a plastic lead screw instead of ball bearings, but when made of plastic, it needs to be molded with a larger diameter and thickness than a metal lead screw to eliminate core runout of the rotating shaft. Also, because it is made of plastic, it has a larger friction coefficient than metal materials, so there was an issue that the friction load increases when it is screwed together.

[0009] Therefore, the present invention (hereinafter referred to as "the present invention") focuses on these problems and aims to solve them, by making the lead screw out of resin to reduce costs and providing a valve body drive device in which the lead screw is supported at both ends, making it possible to maintain the rotational axis while reducing frictional load. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, the present invention provides a valve body drive device that converts the rotational output of an electric motor into a linear motion to move a valve body linearly back and forth to close and open a gas flow port, comprising: a resin lead screw connected to the output shaft of the electric motor so as to be capable of directly transmitting torque;

[0011] a carriage including a linear feed section that engages with a part of the screw section of the lead screw to move it linearly along an output axis, and a pair of parallel arms that extend from the linear feed section toward the valve body along the output axis; a shaft support guide having an insertion opening for allowing the arm portion of the carriage to pass therethrough and including a shaft support portion that moves relatively on an output axis with respect to the carriage; a valve guide that holds the valve body and is coupled to the carriage to move together therewith; a spring means disposed between the valve guide and the shaft support guide with an expanding biasing force; The tip end of the lead screw is characterized in that it abuts against the shaft support portion of the shaft support guide with an area as small as possible on the output axis. The linear motion feed unit that engages with a part of the screw portion of the lead screw to linearly move the carriage along the output axis may be configured as follows: The lead screw may be screwed into the carriage, or a convex portion that moves along the helical groove of the screw may be formed on the inside of the carriage.

[0012] As a specific example of the connection of the lead screw to the output shaft of the electric motor, a support rod for the lead screw, one end of which is formed into a non-circular cross section, may be fitted onto the output shaft.

[0013] In addition, it is preferable that the tip of the lead screw and the bearing are brought into contact with each other through the intermediation of a sphere, which, together with the rotation of the sphere, reduces the rotational friction between the lead screw and the bearing.

[0014] In addition to the above-mentioned use of a sphere, the end face of the tip of the lead screw and / or the face of the bearing portion may be formed with any one of a truncated cone shape, a hemisphere shape, or a gradually tapering mountain shape for abutment.

[0015] Furthermore, if necessary, a metal shaft may be inserted (or fitted) into the output axis of the lead screw from the output shaft of the electric motor without penetrating the tip of the lead screw, which makes it possible to maintain the center of the lead screw's rotating shaft (= output shaft) and improve its strength.

[0016] The lead screw with the metal shaft inside may be connected to the output shaft of the electric motor by forming an external fitting part (made of resin) integrally with the output shaft side end of the screw part and fitting it in. This makes it more suitable to directly transmit torque to the lead screw. Effect of the Invention

[0017] With the above configuration, even if a resin lead screw is used, the load increase is suppressed, so that a low-cost valve body drive mechanism can be realized that can be driven with low power without using costly metal lead screws and ball bearings. In particular, when a battery is used as the power source, this contributes to reducing the battery capacity.

[0018] Furthermore, since the lead screw is supported in a spanning manner between its tip and the output shaft of the rotor, it is possible to suppress core runout of the lead screw, and even in the case of a plastic lead screw, the threaded engagement length of the screw portion with the carriage can be reduced, thereby reducing the rotational load due to friction. [Brief description of the drawings]

[0019] [Figure 1] 1 is a vertical cross-sectional view of a valve body drive mechanism according to an embodiment of the present invention (hereinafter, referred to as the present embodiment). [Diagram 2] 2 is an enlarged cross-sectional view of a region indicated by an arrow A in FIG. [Diagram 3] FIG. 2 is an exploded perspective view of the valve body drive mechanism according to the present embodiment. [Figure 4]FIG. 1A is a longitudinal cross-sectional view showing the assembled state of the valve guide, the journal guide, and the carriage that constitute the valve body drive mechanism, FIG. 1B is a cross-sectional view of the valve guide, FIG. 1C is a cross-sectional view of the journal guide, and FIG. 1D is a cross-sectional view of the carriage. [Diagram 5] FIG. 1A is a cross-sectional view showing another embodiment of the lead screw, and FIG. 1B is a vertical cross-sectional view of a valve body drive mechanism to which the lead screw is attached. [Figure 6] These are cross-sectional views showing the contact state between the tip of the lead screw and the support portion, where (A) shows the contact state between the flat surface of the support portion and a hemisphere, and (B) shows the contact state between the truncated cone-shaped parts. [Figure 7] 5A and 5B are cross-sectional views showing the operation of the valve body drive mechanism of the present embodiment, in which (A) shows the process of closing the valve body to the gas flow port, and (B) shows the process of opening the valve body from the gas flow port. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present embodiment will be described below with reference to the drawings.

[0021] In this embodiment, there are no limitations on the installation position, vertical position, or horizontal / vertical position. For ease of explanation, however, the vertical and left / right directions will be used based on FIG. 1, which shows the output axis as being horizontal. [Overall configuration]

[0022] The valve body drive device 1 shown in Fig. 1 is attached to a gas flow passage, and is maintained in an airtight state by an airtight member 11. The rotational output of a stepping motor 2, which serves as an electric motor, is directly transmitted to a lead screw 3, and a carriage 4 engaged with the lead screw 3 is linearly moved, whereby a valve body 6 engaged with the carriage 4 is moved forward and backward in a linear direction along the output axis, thereby closing and opening a gas flow port 10. [Drive source configuration] The stepping motor 2 serving as the drive source has a general known configuration.

[0023] A stator 20 having a coil 20c wound around its outer periphery and a rotor 22 having a permanent magnet 22m arranged around its outer periphery are arranged so as to be rotatable about the axis with an air gap between the stator 20. The stepping motor 2 is arranged in an airtight state on a mounting plate 24 via an airtight member 11, facing the gas flow port 10 in the gas flow path.

[0024] The stepping motor 2 is powered by a battery (not shown), but this is not limiting and an external power supply may be used. However, in consideration of power outages during disasters such as earthquakes, batteries (dry batteries or storage batteries) are preferable. [Output shaft configuration]

[0025] A resin lead screw 3 configured to enable direct torque transmission is attached to the output shaft 23 of the rotor 22. The lead screw 3 is integrally formed with a screw section 30 of a predetermined length formed from the vicinity of a tip 31 toward the rotor 22, and a support rod 32 (on the right side of the drawing) extending from the end of the screw section 30 to the rotor 22 side. The support rod 32 is formed into a rod-like body having a non-circular cross-sectional shape (e.g., rectangular cross-section or D-shaped cross-section) for torque transmission, and is tightly fitted into the output shaft 23 of the rotor 22. Alternatively, a key groove (not shown) may be formed in the support rod 32.

[0026] With the above-mentioned configuration, the lead screw 3 is driven to rotate integrally with the output shaft 23 of the rotor 22. In other words, the shaft support rod 32 passes through the output shaft of the rotor 22 in a tight contact state, and is supported rotatably by a bearing 21 exposed from the right end of the rotor 22 and formed on the inner bottom of the stator 20.

[0027] As a result, torque (rotational force) is directly transmitted to the lead screw 3, and the lead screw 3 rotates on the output axis R of the rotor 22 while the axis is maintained.

[0028] The lead screw 3 having the above-mentioned configuration is engaged with a part of the carriage 4 on the rotor 22 side. The carriage 4 is made up of a linear feed part 40 which engages with a part of the screw part 30 of the lead screw 3 on the rotor 22 side, and a pair of parallel arms 41, 41 extending from the linear feed part 40 towards the valve body 6.

[0029] In this embodiment, the engagement in the linear feed portion 40 is by screwing. However, since this screwing is aimed at linear feed action along the output axis R rather than maintaining the axis of the lead screw 3, the screwing is performed by forming a spiral of about one revolution.

[0030] Furthermore, the engagement in the linear feed portion 40 is not limited to the above-mentioned screw engagement, and may be any configuration that linearly moves the carriage 4 along the output axis R. For example, a convex shape (preferably at least two or more opposing points to eliminate core runout) that moves along the helical groove (thread groove) of the screw portion 30 may be formed on the inside of the carriage 4. [Other Examples of Lead Screws]

[0031] In this embodiment, the lead screw 3 is molded only from resin material, but a composite lead screw 300 may also be used in which a small-diameter wire metal shaft 301 is inserted along the output axis R to near the tip in a non-penetrating state into a screw portion formed from resin material (see FIG. 5).

[0032] The metal shaft 301 having such a configuration differs from the conventional example in that it does not actively transmit torque from the rotor 22, but is used as a reinforcing material for maintaining the axis of the composite lead screw 300. Therefore, to enable direct torque transmission, an external fitting portion 303 is integrally formed on the rotor side end of the screw portion 30 so as to be directly fitted on the outside.

[0033] As described above, the metal shaft 301 is not intended to transmit torque, so its shaft diameter can be made smaller than that of the conventional example. This allows the composite lead screw 300 to have a smaller diameter, thereby reducing the rotation load.

[0034] In other words, for the same pitch, a smaller diameter composite lead screw 300 increases the lead angle of the screw, improves screw efficiency, and allows the screw to rotate with low torque. This reduces the moment of inertia during rotation and improves responsiveness during acceleration and deceleration. Using a smaller diameter wire also leads to lower costs. [Direct conversion configuration]

[0035] A pivot guide 5 is disposed on the tip side (left direction in the drawing) of the arm portion 41 of the carriage 4. The pivot guide 5 has a bottomed cylindrical body 50 that is guided by the pair of arms 41, 41 of the carriage 4 and moves linearly so as to be freely slidable. The bottom surface 51 of the cylindrical body 50 has two insertion holes 52, 52 (top and bottom in the drawing) through which the pair of arms 41 can be inserted. Furthermore, a bottomed cylindrical pivot support portion 53 exposed on the valve body 6 side is formed in the center of the bottom surface 51. The pivot support portion 53 is guided between the pair of arms 41, 41 and is positioned so as to slide relatively.

[0036] Due to the above-mentioned configuration of the shaft support guide 5 and the carriage 4, the carriage 4 moves linearly by inserting the pair of parallel arms 41, 41 into the insertion hole 52, preventing the carriage 4 from rotating in a driven manner caused by threading friction with the lead screw 3. As a result, the rotational force of the lead screw 3 is converted into a linear force for the carriage 4.

[0037] Also, an annular flange 54 is formed on the outer periphery of the cylindrical body 50 of the shaft support guide 5. The flange 54 of the cylindrical body 50 abuts against the rotor 22 side surface of the mounting plate 24 in a state where it is exposed from the opening 25 of the mounting plate 24, and the case 26 that contains the rotor 22 is attached to the rotor side via the airtight member 11. This prevents gas leakage.

[0038] Furthermore, a coil spring 7 having an expanding force as a spring means (described later) is fitted between the support guide 5 and the valve guide 61, which are arranged to penetrate the opening 25 of the mounting plate 24, and one side of the coil spring 7 abuts against the edge of the opening 25.

[0039] Furthermore, a sphere 55 is rotatably disposed in a bearing portion 53 formed in a cylindrical shape with a bottom on the bottom surface portion 51 of the bearing guide 5. The tip portion 31 of the lead screw 3 abuts against the sphere 55. At the same time, the tip outer peripheral surface 33 of the tip portion 31 of the lead screw 3 fits smoothly and slidingly into the cylindrical inner peripheral surface 56 of the bearing portion 53 with a bottom.

[0040] As a result, the outer peripheral surface 33 of the tip end of the lead screw 3 is rotatably supported by the cylindrically formed shaft support portion 53, and the rotation axis of the lead screw 3 is maintained.

[0041] In addition, the contact area on the rotation axis of the lead screw 3 with the tip 31 can be made small by contacting the tip 31 with the sphere 55. This, combined with the rotation of the sphere 55, reduces the rotational friction force generated at the tip 31 as much as possible.

[0042] The contact between the lead screw 3 and the bearing portion 53 is not limited to the above-mentioned sphere 55. Alternatively, either one of the inner bottom surface 53b of the bearing portion 53 and the tip portion 31 of the lead screw 3 may be a flat surface, and the other may be a hemisphere 57, a truncated cone 58, a truncated polygonal pyramid, or a mountain shape with a gradually decreasing diameter (see Figures 6(A) and (B)). [Valve body configuration]

[0043] The valve body 6 mainly comprises a valve guide 61 that holds a valve seat 60 made of an elastic material. The valve guide 61 is engaged with the tip portions 41t of the pair of parallel arms 41, 41 at the center thereof sandwiching the output axis R therebetween.

[0044] In detail, the valve guide 61 has a substantially cylindrical base frame 62 that holds a disk-shaped valve sheet 60 that closes the gas flow port 10 (usually a circular opening), and in the center of the base frame 62 is a fitting opening 63 into which the tip portions 41t of the pair of arms 41 fit. By fitting the arm portions 41 into the fitting openings 63, the parallel spacing of the arm portions 41 extending in parallel is maintained.

[0045] Further, a locking key portion 64 is formed at the outer periphery of the fitting opening 63, extending toward the carriage 4 and having a tip processed into a hook shape. This locking key portion 64 is configured to lock with a locking protrusion 42 formed on the outside of the arm portion 41 of the carriage 4.

[0046] Furthermore, a coil spring 7 having an expanding biasing force is annularly arranged on the valve guide 61 between the base frame 62 of the valve guide 61 and the shaft support guide 5 with the mounting plate 24 sandwiched therebetween.

[0047] With the above-mentioned structure, the valve guide 61 and carriage 4 move linearly together as a unit due to the interaction between the engagement of the engagement projection 42 and the engagement key portion 64 and the expansive force of the coil spring 7 opposed thereto.

[0048] The valve guide 61 and the carriage 4 are also integrated by fitting the tip 41 t of the arm 41 into the fitting opening 63 . [Activation] With the above configuration, this embodiment operates as follows.

[0049] As shown in Fig. 7(A), when the stepping motor 2 is started, the lead screw 3 directly connected to the rotor 22 rotates about its axis (rightward rotation Tr). This causes a pushing force along the output axis R to act on the linear feed section 40 that is screwed into a part of the screw section 30. At this time, the carriage 4 is prevented from rotating because the arm section 41 is engaged with the engagement opening 63, and only a linear moving force acts on it, causing it to move leftward (arrow Cl). This movement (to the left in the drawing) occurs along the output axis R of the lead screw 3.

[0050] As a result, the valve guide 61 moves linearly to the left (arrow Bl) together with the carriage 4. This movement causes the valve seat 60 of the valve body 6 to move closer to the gas circulation port 10 (arrow C) and enter a closed state. Furthermore, in this state, the expanding biasing force of the coil spring 7 is applied, making the gas circulation port 10 more reliably airtightly closed.

[0051] Next, to open the gas flow port 10 from the above-mentioned closed state, the lead screw 3 is rotated left (arrow Tl) as shown in FIG. 7(B), the carriage 4 moves right (arrow Cr), and the valve guide 61 moves right (arrow Br), thereby moving the valve seat 60 to the right (arrow O) by operating them in the opposite directions.

[0052] By the above operation, the present invention can close and restore the gas flow port automatically or by remote signal. [Explanation of symbols]

[0053] 1 Valve body drive device 2 Stepping motor 20 Stator 21 Bearings 22 Rotor 23 Output shaft 24 Mounting plate 3 Lead Screw 30 Screw section 31 Tip 32 Support rod 33 Tip outer periphery 300 Compound Lead Screw (Other Examples) 301 Metal Shaft 302 Resin part 303 External fitting part 4 Carriage 40 Linear feed section 41 Arm 5 Axis support guide 50 Cylinder 51 Bottom part 52 Insertion port 53 Bearing 55 Sphere 56 Inner surface 6 Valve body 60 Valve seat 61 Valve Guide 63 Fitting port 7 Coil spring

Claims

1. A valve body drive device that converts the rotational output of an electric motor into a linear motion to move a valve body linearly back and forth to close and open a gas flow port, a resin lead screw connected to the output shaft of the electric motor so as to be capable of directly transmitting torque; a carriage including a linear feed section that engages with a part of the screw section of the lead screw to move it linearly along an output axis, and a pair of parallel arms that extend from the linear feed section toward the valve body along the output axis; a shaft support guide having an insertion opening for allowing the arm portion of the carriage to pass therethrough and including a shaft support portion that moves relatively on an output axis with respect to the carriage; a valve guide that holds the valve body and is coupled to the carriage to move together therewith; a spring means disposed between the valve guide and the shaft support guide with an expanding biasing force; 2. A valve body drive mechanism, comprising: a tip end of said lead screw abutting against a bearing portion of said bearing guide with an area as small as possible on said output axis.

2. a linear motion feed section that engages with a part of the screw section of the lead screw to linearly move the carriage along an output axis line, 2. The valve body drive mechanism according to claim 1, wherein the lead screw is screwed into the carriage.

3. a linear motion feed section that engages with a part of the screw section of the lead screw to linearly move the carriage on an output axis line, 2. The valve body drive mechanism according to claim 1, wherein a convex portion that moves along the helical groove of the screw portion is formed on the inside of the carriage.

4. A connection capable of directly transmitting torque to an output shaft of the electric motor is provided.

2. The valve body drive mechanism according to claim 1, wherein a support rod of the lead screw, one end of which is formed to have a non-circular cross section, is fitted onto the output shaft.

5. When the tip of the lead screw contacts the bearing, 2. The valve body drive mechanism according to claim 1, further comprising a sphere interposed therebetween.

6. When the tip of the lead screw contacts the bearing, 2. The valve body drive mechanism according to claim 1, wherein one or both of the surfaces is formed in a truncated cone shape, a truncated polygonal pyramid shape, a hemisphere shape, or a gradually tapering mountain shape.

7. In the lead screw configuration, 7. The valve body drive mechanism according to claim 1, wherein a metallic shaft is disposed inside the output axis of the electric motor in a state where the tip of the lead screw does not extend from the output shaft of the electric motor.

8. The coupling of the lead screw according to claim 7 to the output shaft of the electric motor is A valve body drive mechanism, comprising: an outer fitting portion integrally formed on an end portion of a screw portion on an output shaft side, the outer fitting portion being fitted onto the output shaft.

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