JPH095064A - Abrasion quantity detector for stem nut in motor-operated valve driving device - Google Patents

Abstract

PURPOSE: To precisely detect the abrasion state of a stem nut with ease at any time and to accomplish easy application of a detector to an installed motor- operated valve driving device. CONSTITUTION: A driving projection 15 in a worm wheel 14 collides against a driven projection 20a in a drive sleeve 20, and vibration generated because of the collision between both projections 15, 20a when a stem nut 18 starts to rotate is detected by means of a vibration detecting sensor 32. The time from this detection to detection of elevation of a stem 16 screwed to the stem nut 18 by means of a displacement sensor 33 is measured by means of a timer 38, and on the basis of the measured time, the abrasion quantity of an internal thread part of the stem nut 18 is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for easily and accurately detecting the wear state of a stem nut used in an electric valve drive device.

[0002]

2. Description of the Related Art Generally, a motor-operated valve has a male stem threaded on a steel stem connected to a valve body, and a brass stem nut with a female thread cut on the male thread. The transmission mechanism is interposed in the middle, and it is rotated by an electric motor to raise and lower the stem. Therefore, when used for a long period of time, the internal thread of the soft stem nut gradually wears, and it is necessary to replace the stem nut before the internal thread reaches the wear limit.

However, it is impossible to visually inspect the degree of wear of the stem nut from the outside.

An example of the countermeasure is the actual Kaihei 1-158686.
No. 1 publication. In this, the entire length of the stem nut is lengthened and a notch provided in a part thereof is exposed to the outside so that the degree of wear can be visually checked.

Further, in Japanese Unexamined Patent Publication No. 4-296268, the rotation speed of the worm is detected by an absolute type rotary encoder, and the output of the encoder when the stem passes a predetermined reference position is monitored, so that it can be changed over time. There is disclosed means for detecting the amount of wear of the stem nut based on the output value of the encoder that changes to.

[0006]

According to the former means described above, even if the stem nut exceeds the usable limit, its wear amount is very small, so that it is difficult to make an accurate visual determination. However, in a large-scale plant, the motor-operated valve is often provided above, below, or on the back side of the large-scale equipment, and in such a case, it is difficult to visually check.

The latter means can be effectively implemented when a new motor-operated valve drive device is installed, but it is difficult to incorporate it into an existing motor-operated valve drive device, and the whole motor-operated valve drive device is replaced. In addition, the amount of wear could not be detected unless the stem passed a predetermined reference position, and the measurement accuracy was not sufficient.

In view of the above-mentioned problems of the prior art, the present invention can easily and accurately detect the wear state of the stem nut at any time and can be easily installed in an existing electric valve drive device. An object of the present invention is to provide a wear amount detecting device for a stem nut in an electrically operated valve drive device that can be applied.

Further, in particular, the present invention detects the amount of wear of the stem nut by detecting the vibration during the operation of the hammer blow generating mechanism and measuring the time from the detection to the actual movement of the stem. In this case, the vibration during the operation of the hammer blow generation mechanism can be detected accurately and with high sensitivity, so that the wear detection accuracy is improved and the sensor to be used is disassembled from the electric valve drive device itself. It is also an object of the present invention to be easily mounted on an existing electric valve drive device without being installed.

[0010]

According to the present invention, the above-mentioned problem is solved as follows. (1) A worm wheel that meshes with a worm that can be rotated in the forward and reverse directions by a motor, and a female screw that is disposed on the same axis as the worm wheel but is rotatable but immovable in the axial direction and that is formed on the inner surface Between the male screw formed on the stem connected to the valve body and the stem nut adapted to be screwed, the driving member connected to the worm wheel and the driven member connected to the stem nut have a required play in the rotation direction of the worm wheel. Is provided with a hammer blow generating mechanism for applying an impact force to the driven member side when the worm wheel is reversed, and the worm is resistant to the urging force of the torque spring acting in the axial direction of the worm wheel. Direction, the load torque can be detected by detecting the amount of movement of the worm in the axial direction. The electric valve driving device having a click switch mechanism, provided in the torque switch mechanism,
A vibration detection sensor that detects the vibration of the worm in the axial direction due to the operation of the hammer blow generation mechanism, a displacement sensor that detects the movement of the stem, and the time from when the vibration detection sensor operates until the displacement sensor operates. And a time measuring means for measuring.

(2) In the above item (1), the driven member of the hammer blow generating mechanism is disposed between the worm wheel and the stem nut so as to be concentric with them, and is engaged with the driving member on a part of the outer peripheral surface. The drive sleeve is provided with a follower protrusion which can be fitted, and the inner surface of which is splined with the outer surface of the stem nut.

[0012]

The stem nut starts rotating at the time when the driving member of the hammer blow generating mechanism abuts the driven member and an impact force is applied to the driven member, and the stem starts rotating from that time. The movement starts from the time when the female thread portion of the stem nut completely meshes with the male thread portion of the stem, and the amount of time between these two time points corresponds to the amount of wear of the stem nut. Therefore, the wear amount of the stem nut can be detected by detecting these time points by the vibration detection sensor and the displacement sensor and measuring the time between the two time points by the time measuring means.

The vibration detection sensor is provided in the torque switch mechanism to detect the vibration in the axial direction of the worm due to the operation of the hammer blow generating mechanism, so that the vibration due to the operation of the hammer blow generating mechanism can be accurately measured. And it can be detected with high sensitivity.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a driving portion of an electric gate valve to which the present invention is applied. A central portion of a housing (1) has a front-rear direction (a right side in FIG. A worm shaft (2) that faces the
A cylindrical worm (3) is fitted by spline connection so as to be axially movable and non-rotatable.

The rear end of the worm shaft (2) has spur gears (4) and (5).
Housing through a reduction mechanism consisting of and clutch (6)
(1) A pair of spur gears, which are connected to an electric motor (7) provided at the rear of the (1) and can rotate in forward and reverse directions.
Via (8) and (9), it is also linked to the handle shaft (11) that has the handle (10) at the front end, and the clutch (6) is disengaged.
It can also be rotated by operating the handle (10).

A sleeve (12) is provided at the front of the worm shaft (2).
However, the worm (3) is biased in the front-rear direction toward a predetermined neutral position by the torque spring (13) which is fitted and externally fitted to the sleeve (12) and which is composed of a large number of disc springs. The sleeve (12), the torque spring (13), and the worm (3) are actually intricately engaged with each other, but their configurations are well known and directly related to the present invention. Therefore, only that the above-mentioned action occurs will be described, and a detailed description thereof will be omitted.

Worm wheel that meshes with the worm (3)
At the position where the upper surface of (14) has a 180 ° relationship with each other, 1
A pair of drive projections (driving members) (15) are provided so as to project upward.

A valve body (17) is connected to the lower end of a vertically oriented stem (16) passing through the center of the worm wheel (14).

As shown in FIG. 2, the male screw portion (16a) on the upper portion of the stem (16) has a female screw portion (18a) on the inner surface of the stem nut (18) fitted in the worm wheel (14). , And the male screw portion (16a) is screwed with a slight gap (19).

The stem nut (18) has a drive sleeve (driven member) (20) pivotally supported on the housing (1) so that it cannot be moved up and down.
Is fitted on the worm wheel (14) and the stem nut (18) so as to be concentric with each other.The stem nut (18) and the drive sleeve (20) are attached to the spline (2
By 1), they are connected so that they cannot rotate relative to each other.

On the outer peripheral surface of the drive sleeve (20), a pair of driven protrusions (20a) arranged on the same circumference as the drive protrusion (15).
Is protruding.

In order to transmit the rotational force from the output shaft (not shown) of the motor (7) to the stem nut (18) screwed to the stem (16), the worm shaft (2), the worm (3), With elements such as the worm wheel (14) and drive sleeve (20),
A rotation transmission mechanism is formed. The drive projection (15) of the worm wheel (14), which is the driving member, and the drive sleeve (20), which is the driven member, allow the worm wheel (1
A hammer blow generating mechanism is formed which engages with the required play in the rotation direction of 4) and applies an impact force to the driven member side when the worm wheel (14) is reversed.

A small worm wheel is attached to a small worm (23) formed immediately after the worm (3) on the worm shaft (2).
(24) meshes, and its rotation speed detection shaft (25) is a valve opening control device (2) for setting the upper and lower limits of the stem (16).
It is linked to 6).

Rack (2) engraved on the outer peripheral surface of the sleeve (12)
The pinion (28) meshes with (7), and its axis, the torque detection shaft (29), has a rotary torque limit switch (3
It is linked to a torque control device (31) that includes 0).

The above construction is the same as that of the conventional motor-operated valve drive apparatus, and the present invention includes an apparatus for detecting the degree of wear of the female screw portion (18a) having the following construction in addition to these constructions. The feature is that it is provided.

The torque detection shaft (2
At the free end (left end in Fig. 1) of 9), the driving projection (15) has the driven projection (2
Vibration detection that detects the so-called hammer blow vibration that occurs when it collides with 0a) via the worm (3), sleeve (12), rack (27), pinion (28), and torque detection shaft (29). A sensor (32) is provided.

The vibration detection sensor (32) is preferably a known acceleration type vibration detection sensor, but may have another structure, for example, a sound detection sensor such as a microphone.

Further, the stem (16) in the housing (1)
Above the above, a displacement sensor (3
3) is provided. The displacement sensor (33) includes an elevating rod (3) that vertically penetrates a support cylinder (34) fixed to the housing (1).
5) is urged downward by the coil spring (36), and the lifting rod
The lower end of (35) is constantly in pressure contact with the upper end of the stem (16), and the movement of the lifting rod (35) is detected by a differential transformer (not shown) provided in the support cylinder (34). ing. The displacement sensor (33) may have another structure, for example, a known linear encoder, as long as it can detect the vertical movement of the stem (16).

(37) is electrically connected to the vibration detection sensor (32) and the displacement sensor (33), and indicates the time from the activation of the vibration detection sensor (32) to the activation of the displacement sensor (33). It is a measuring device provided with a timer (measuring means) (38) for measuring.

Next, the operation of this embodiment will be described. Stem (16) until the valve body (17) contacts the valve seat (not shown)
When the torque limit switch (30) operates and the motor (7) is stopped when the closing torque reaches the set torque, the stem nut (18) is moved as shown by the arrow in FIG. The lower surface of the thread of the female thread (18a) of
It is strongly pressed against the upper surface of the thread of the male screw part (16a) of 6).

When the motor (7) is rotationally driven in the valve opening direction from such a valve closed state, the rotational force is changed to the spur gear (4).
The worm wheel (14) is transmitted to the worm wheel (14) through the (5), the worm shaft (2), and the worm (3).
Is rotated in one direction, and the drive protrusion (15) of the worm wheel (14) is in contact with the drive sleeve (2
Move away from the driven protrusion (20a) of 0).

At this time, since the worm wheel (14) simply idles and is hardly loaded, the worm wheel (14)
(3) hardly moves in the axial direction from the neutral position.

When the worm wheel (14) slightly rotates about 180 °, the drive protrusion (15) of the worm wheel (14) abuts the driven protrusion (20a) of the drive sleeve (20), and the impact at that time, that is, Hammer blow, drive sleeve
In addition to being applied to the (20) side, it is also applied to the worm (3) side from the worm wheel (14) as a reaction.

The worm (3) is affected by the impact at this time.
It slightly vibrates in the direction of the worm shaft (2), and the vibration is transmitted to the torque detection shaft (29) via the rack (27) and the pinion (28) and detected by the vibration detection sensor (32). The output state of the vibration detection sensor (32) at this time is shown as hammer blow vibration (V) in FIG.

3 (M) shows the vibration of the torque detecting shaft (29) at the starting point (P1) of the motor (7), that is, the starting vibration. Since the damping time (t) of this starting vibration (M) can be known in advance, after the starting of the motor (7), the damping time (t) is
It is preferable to mask a certain time slightly longer than (t) so that the output of the vibration detection sensor (32) is not sensed during that time. As a result, the vibration detection sensor (32) can accurately detect the hammer blow vibration (V).

The time point when the hammer blow vibration (V) is detected by the vibration detection sensor (32) is defined as (P2), and the timer (38) starts timing from that time point.

Due to the impact of the hammer blow applied to the drive sleeve (20) side, as shown in FIG. 2, the female screw portion (18a) on the inner surface of the stem nut (18) which is strongly pressed against each other.
Can be easily separated from the male screw part (16a) of the stem (16), and then can be rotated with a light force.

At this time, the female thread portion (1) of the stem nut (18) is
If there is no backlash (L) as shown in Fig. 2 between 8a) and the male screw part (16a) of the stem (16), the stem
(16) will start rotating at the same time as the rotation of the stem nut (18), that is, at the time when the hammer blow vibration (V) is detected (P2), but in actuality there will be some backlash (L). Is present and wear of the stem nut (18) increases its backlash (L). If such backlash (L) exists, the lower surface of the thread of the female thread portion (18a) of the stem nut (18) will be the upper surface of the thread of the male thread portion (16a) of the stem (16) even after hammer blow occurs. Only the stem nut (18) rotates and the stem (16) does not move until it abuts against.

Therefore, the above hammer blow vibration
The time (T1) from the time (P2) when (V) is detected to the time (P3) when the output signal (G) of the displacement sensor (33) starts to change is the timer (38) of the measuring device (37). It is possible to detect the size of the backlash (L) by measuring with, and then to determine the degree of wear of the stem nut (18).

Actually, the output signal (G) of the displacement sensor (33)
It is difficult to accurately detect the point (P3) at which the change starts, so from the above point (P2), the output signal (G) becomes the minimum level (D = resolution) that can be detected as the change. The time (T1 ') up to the time (P3') reached is measured and the time (T1 ')
It is preferable that 1 ') is corrected by the delay time (T2) previously calculated and the time (T1) is calculated.

Subsequent operations are the same as those of the conventional motor-operated valve drive device having the hammer blow mechanism, and therefore detailed description thereof will be omitted.

The hammer blow as described above and the subsequent operation as described above are performed not only when the valve is closed, but after raising or lowering the stem (16) to an arbitrary position, the motor (7) is reversed. Since it always occurs when the stem nut (18) is caused to wear, the stem (16) can be set to an arbitrary height and the wear of the stem nut (18) can be measured at any time.

As described above, the stem nut according to the present invention
The measurement principle of wear in (18) is relatively simple,
Nevertheless, the reason why such measuring means has not been put to practical use in the past is that it is difficult to detect the hammer blow easily and surely.

That is, the hammer blow is not so large in general, and even if the vibrometer is attached to the outer wall of the housing (1), the rotational vibration of the motor (7), the meshing vibration of the gears, etc. Became noise and it was extremely difficult to accurately detect the hammer blow.

In this respect, in the present invention, by detecting the vibration of the worm in the axial direction using the torque detection shaft (29) in the existing torque control device (31) and the like, various noises as described above are detected. It became possible to detect a hammer blow accurately without being affected by.

That is, when a hammer blow occurs,
The shock is transmitted from the worm wheel (14) to the worm (3), and from there, through the rack (27) and the pinion (28), the torque detection shaft (29) for detecting the axial movement of the worm (3). ) Is transmitted to.

As described above, since the shock is transmitted through many parts, it seems that the detection sensitivity is lowered at first glance, but in reality, the shock of the hammer blow is caused by the rotation of the worm wheel (14). Acting in the axial direction on the worm (3) that meshes with the worm wheel (14), and the worm (3) is moved by the torque spring (13) consisting of many disc springs in the axial direction. Since it is maintained in a floating state, vibration from the outside that causes noise is absorbed by the torque spring (13), and only the impact of the hammer blow is transmitted via the rack (27) and pinion (28) to the torque detection shaft ( It can be accurately transmitted to 29) and extremely high detection sensitivity can be obtained.

In the experiment, as in the hammer blow vibration (V) shown in FIG. 2, a steep pulse vibration waveform was obtained for a moment. On the other hand, when a vibrometer was attached to the outer wall of the housing (1), such an accurate pulse vibration waveform was not obtained, and most of them were indistinguishable from noise.

[0049]

According to the present invention (the invention described in claims 1 and 2), the following effects can be obtained. (a) The amount of wear of the stem nut incorporated in the motor-operated valve drive device can be detected easily and accurately at any time without disassembling the device or relying on visual inspection.

(B) Even in the existing motor-operated valve drive device that does not have a wear amount detection function, the wear amount can be detected later without disassembling the device itself and with the device installed in a plant or the like. The device can be easily installed to detect the amount of wear on the stem nut.

(C) A vibration detection sensor is provided in the torque switch mechanism to detect vibrations in the axial direction of the worm due to the operation of the hammer blow generation mechanism. It is possible to accurately and highly sensitively detect only the vibration caused by the operation of the hammer blow generation mechanism without being affected by noise caused by vibrations, etc., and it is practical to detect the amount of wear from the time difference between the operations of both sensors. Became possible.

(D) Since the vibration detection sensor can be attached to the torque switch mechanism in the wiring case of the torque switch mechanism, it is possible to easily attach the vibration detection sensor to the existing device later and to perform maintenance. Easy to check.

(E) The displacement sensor can be easily attached from the outside by utilizing the portion where the stem cover or the like is attached.

[0054]

[Brief description of drawings]

FIG. 1 is a partially cutaway exploded view of an electric gate valve to which the present invention has been applied.

FIG. 2 is an enlarged front view of a part of the threaded portion between the stem and the stem nut, which is cut along the center.

FIG. 3 is a time chart showing an output waveform of each sensor after starting the motor.

[Explanation of symbols]

 (1) Housing (2) Worm shaft (3) Worm (4) (5) (8) (9) Spur gear (6) Clutch (7) Motor (10) Handle (11) Handle shaft (12) Sleeve (13) ) Torque spring (14) Worm wheel (15) Drive protrusion (16) Stem (16a) Male thread (17) Valve body (18) Stem nut (18a) Female thread (19) Gap (20) Drive sleeve (20a) Follower Protrusion (21) Spline (23) Small worm (24) Small worm wheel (25) Rotation speed detection shaft (26) Valve opening control device (27) Rack (28) Pinion (29) Torque detection shaft (30) Torque limit Switch (31) Torque control device (32) Vibration sensor (33) Displacement sensor (34) Support tube (34a) Bottom plate (35) Lifting rod (36) Coil spring (37) Measuring device (38) Timer (time measuring means) (P1) (P2) (P3) (P3 ') time (T1) (T1') (T2) time (t) decay time (L) backlash (M) start vibration (V) hammer blow vibration (G) output signal (D) Resolution

Claims (2)

[Claims] 1. A worm wheel meshing with a worm that is rotated in a forward and reverse direction by a motor, and a female screw formed on the inner surface of the worm wheel so as to be rotatable on the same axis and immovable in the axial direction. However, between the male screw formed on the stem connected to the valve body and the stem nut that is screwed together, the driving member connected to the worm wheel and the driven member connected to the stem nut are required in the rotation direction of the worm wheel. Engage with play,
A hammer blow generating mechanism is provided to apply an impact force to the driven member side when the worm wheel is reversed, and the worm can be moved in the axial direction against the biasing force of the torque spring acting in the axial direction. In a motor-operated valve drive device provided with a torque switch mechanism capable of detecting a load torque by detecting an amount of movement of the worm in the axial direction, an operation of a hammer blow generation mechanism provided in the torque switch mechanism. A vibration detection sensor that detects the vibration of the worm in the axial direction of the worm, a displacement sensor that detects the movement of the stem, and a timing unit that measures the time from the activation of the vibration detection sensor to the activation of the displacement sensor. A wear detecting device for a stem nut in an electric valve driving device, comprising: 2. A driven member of a hammer blow generating mechanism,
A drive that is disposed between the worm wheel and the stem nut as a concentric core with them, has a driven protrusion that can engage with a driving member on a part of the outer peripheral surface, and has an inner surface spline-coupled to the outer surface of the stem nut. A sleeve as claimed in claim 1.
A wear detecting device for a stem nut in the electric valve driving device as described above.