JPH0678658U - Feeding mechanism - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a feed screw that contributes to downsizing and cost reduction of a device to be incorporated, such as an XY table, and has high reliability in nut positioning. A detected part 11 is formed between the thread grooves 1a of the screw shaft 1 along the thread grooves, and detection means 15, 19, 20 for detecting the detected part 11 are provided on the nut 2 side. The above effect is obtained.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a feeding mechanism.

[0002]

[Prior art]

 FIG. 9 shows a ball screw as an example of a conventional feeding mechanism.

In the figure, the screw shaft 1 is a single thread in this case, and the nut 2 is loosely fitted in the screw shaft 1. As shown in FIG. 10, the nut 2 is formed with a ball circulation path including a load raceway groove 2a corresponding to the thread groove 1a of the screw shaft 1, and a large number of balls 3 are arranged in the ball circulation path. It is housed. These balls 3 circulate as the screw shaft 1 rotates, and apply a load between the screw shaft 1 and the nut 2. The screw shaft 1 is connected to the output shaft 5a of the servomotor 5 shown in FIG. 9 via a coupling (not shown).

The ball screw having the above-mentioned configuration is incorporated, for example, as a so-called XY table driving device that moves a provided movable table in mutually orthogonal X and Y directions, and the nut 2 is attached to the movable table. The screw shaft 1 is connected and operates by being rotationally driven.

[0005]

[Problems to be solved by the device]

 In the case of a device such as an XY table that requires extremely high operating accuracy, it is necessary to detect the position of the nut 2 with high accuracy, and as a position detecting means therefor, a long linear scale 6 as shown in FIG. 9 is used. And a sensor 7 are installed side by side. The linear scale 6 is, for example, one that is finely magnetized in multiple poles in the longitudinal direction, and is provided on the fixed side. The sensor 7 is a magnetic sensor and is attached to the nut 2.

As is apparent from the above, in the conventional feed mechanism, the position detecting means provided for detecting the position of the nut occupies a large space for the components constituting the nut, is relatively expensive, and is incorporated. This is a problem to be solved in order to reduce the size and cost of an XY table or the like.

The screw shaft 1 is mounted on a predetermined base member (not shown) via a bearing, and the linear scale 6 is also mounted on the base member via a bracket or the like. Therefore, a large number of members such as a base member, a bearing and a bracket are mechanically interposed between the screw shaft 1 and the linear scale 6. Therefore, even if the detection accuracy of the position detecting means is set to be high, it is not always easy to increase the reliability of the nut positioning due to the assembly error between these members.

Therefore, the present invention has been made in view of the above-mentioned drawbacks of the prior art, and contributes to downsizing and cost reduction of a device to be incorporated such as an XY table and the reliability of nut positioning. The purpose of the present invention is to provide a feeding mechanism having high performance.

[0009]

[Means for Solving the Problems]

 The feed mechanism according to the present invention is configured such that a detected portion is formed between the screw grooves of the screw shaft along the screw groove, and a detecting means for detecting the detected portion is provided on the nut side. .

[0010]

【Example】

 Next, embodiments of the present invention will be described with reference to the accompanying drawings. The ball screw as each of the following embodiments has the same structure as the conventional ball screw shown in FIGS. 9 and 10 except for the parts described below, and therefore the description thereof as a whole will be omitted. Further, in the following description, the same reference numerals are used for the same components as those of the conventional ball screw.

FIG. 1 shows a ball screw as a first embodiment of the present invention.

As shown in the figure, in the ball screw, a detected portion 11 is formed between the screw grooves 1a of the screw shaft 1 along the screw groove 1a. Then, on the flange portion 2c provided on the nut 2, a small case 12 incorporating a detecting means (described later) for detecting the detected portion 11 is attached.

A magnetic film 14 is provided on the surface between the screw grooves 1a as shown in FIG. 2, and the detected portion 11 is formed by magnetizing the magnetic film 14 as described below. Is made. The magnetic film 14 is formed by applying a molten magnetic agent between the thread grooves 1a of the screw shaft 1 and solidifying the magnetic agent. However, it is also possible to directly magnetize the surface layer portion of the screw shaft 1 itself without forming the magnetic film 14 in this way.

FIG. 3 shows a state in which the detected portion 11 provided along the spiral thread groove 1a is linearly developed.

As shown in the figure, the detected part 11 is multi-polarized along the thread groove 1a. In this case, for detecting the position of the nut 2, N and S magnetic poles are finely and alternately arranged and magnetized along the thread groove 1a. In FIG. 3, the respective magnetized portions are indicated by reference numeral 16, but the non-magnetized portions are indicated by reference numeral 17 with hatching (by dots). As shown, each of the magnetized portions 16 has a boundary 16a in the direction along the thread groove 1a that is perpendicular or substantially perpendicular to the thread groove 1a. A magnetizing part 18 as an origin serving as a measurement reference is provided corresponding to the one located at the extreme end of each of the magnetizing parts 16.

On the other hand, the detecting means provided in the case 12 for detecting the detected portion 11 is composed of the following magnetic sensors.

That is, as shown in FIG. 3, two magnetoelectric conversion elements 19 and 20 such as Hall effect elements provided for detecting each magnetized portion 16 and a magnetized portion 18 serving as an origin are detected. And a magnetoresistive element (MR element) 15 for doing so.

The magnetoelectric conversion element 20 is provided so as to be displaced from the magnetoelectric conversion element 19 by 1/2 of the pitch P between the magnetized portions 16, so that the waveform shown in FIG. On the other hand, a waveform having a phase difference of π / 2 is obtained. As shown in FIG. 5, the waveforms obtained by the magnetoelectric conversion element 19 and the magnetoelectric conversion element 20 are continuous positive and negative sine waves with the O level as a reference, but as shown in FIG. Amplification processing is performed so that the O level is changed to the Vmax level by passing through 21a and 21b. This is to facilitate signal processing in the subsequent stage.

Next, the configuration of the control system that controls the position of the nut 2 based on the detection signal generated by the detection means will be described.

As shown in FIG. 4, the waveforms output from the magnetoelectric conversion element 19 and the magnetoelectric conversion element 20 are input to the amplifier circuits 21a and 21b. A / D conversion circuits 22a and 22b, latch circuits 23a and 23b, and a multiplexer (MPX) 24 are sequentially connected to the amplifier circuits 21a and 21b, and an output of the multiplexer 24 is input to a CPU (control circuit) 25. It is composed. Further, a memory (ROM) 27, an up / down counter 28 as a counting means, and a D / A conversion circuit 29 are connected to the CPU 25.

The A / D conversion circuits 22a and 22b convert the analog waveforms, which have been level-amplified by the amplification circuits 21a and 21b at the preceding stage, into binarized data and input the respective data to the latch circuits 23a and 23b. To do. The latch circuits 23a and 23b latch and hold the data of the A / D conversion circuits 22a and 22b in order to synchronously process the data which is converted by the A / D conversion circuits 22a and 22b at the previous stage. . The held data is input to the multiplexer (MPX) 24. Since this multiplexer (MPX) 24 cannot output the data latched by the latch circuits 23a and 23b at the same time when outputting to the CPU 25 in the subsequent stage, it performs time-division processing and outputs to the CPU 25 separately. Then, arithmetic processing is performed.

Next, the arithmetic processing of the CPU 25 will be described.

First, as an initial operation, the screw shaft 1 is rotationally driven to move the nut 2 to a reference position, and the magnetoresistive element 15 detects a magnetized portion 18 which is an origin point. ) The scale position data stored in 30 is reset. By this reset command, the screw shaft 1 is rotated and the nut 2 starts moving to a desired position. In response to this, the level-amplified continuous waveforms having different phases as shown in FIGS. 5A and 5B are obtained from the magnetoelectric conversion element 19 and the magnetoelectric conversion element 20.

As shown in FIGS. 5A and 5B, for example, regarding the region of m, the output data of the magnetoelectric conversion element 19 and the magnetoelectric conversion element 20 are as shown in FIGS. It can be seen that the corresponding waveforms are different. As a result, the CPU 25 can determine the moving direction of the nut 2 by comparing the different data.

Next, the movement amount of the nut 2 is obtained as follows.

That is, in FIG. 3, when the amount of movement of the detected portion 11 with respect to the magnetoelectric conversion elements 19, 20 and the magnetoresistive element 15 provided in the case 12 is S, the amount of movement L of the nut 2 is L = Ssinβ Required at. Here, β is a lead angle of the screw groove 1a of the screw shaft 1 and is set in advance.

As shown in FIGS. 5 (A) and 5 (B), for example, the movement amount S is V when the output of the magnetoelectric conversion element 19 is V _A and the output of the magnetoelectric conversion element 20 is V _{B. Calculate} the voltage ratio of _A / V _B. This is because, for example, a voltage of α × V _A and α × V _B can be obtained due to a change in the gap between the magnetoelectric conversion element 19 and the magnetoelectric conversion element 20 and each magnetized portion 16 to be detected. , Even if such a gap changes, there is a possibility that arithmetic processing will be carried out as if it had moved. Therefore, if processing is performed as α × V _A / α × V _{B in} order to prevent such a mechanical error, α can be obtained as V _A / V _B because it has nothing to do with position data.

However, since the fine position data within one pitch (P) corresponding to V _A / V _B is previously stored in the memory 27, the CPU 25 obtains the above-described arithmetic processing. can determine the distance α as shown in FIG. 3 by which read from V _a / V _B values and one worthy value memory (ROM) 27 is compared with. Since the position data of the obtained distance α is already stored in the memory 30 (not stored at the time of the first writing from the reference position), the position data previously obtained is stored. After the CPU 25 reads out, the distance α obtained this time is added, and the distance S thus calculated is written in the memory 30 as position data.

By repeating such arithmetic processing, the distance S is stored in the memory 30 as position data.

By the way, the CPU 25 is connected to an up / down counter 28 for up / down a pulse given by a control means (not shown). The up / down counter 28 is configured to operate in response to the reset command of the memory 30, and the number of pulses generated in one pitch (P) shown in FIG. The distance S ′ can be calculated by counting the number of pulses output from the up / down counter 28.

The obtained distance S ′ is compared with the distance S stored in the memory 30 to obtain the deviation amount. The CPU 25 outputs the calculated deviation amount by the D / A converter 29. Based on this output, the nut 2 is driven to the regular position.

As is clear from FIG. 3, in the present embodiment, the magnetized portions 16 to be detected by the magnetoelectric conversion elements 19 and 20 are formed without a gap therebetween. The pitch P between the magnetized portions 16 may be set large by interposing the non-magnetized portions between the portions 16.

Further, in the present embodiment, the magnetizing portion 16 for detecting the movement amount and the magnetizing portion 18 as a measurement reference are also provided between the screw grooves 1a of the screw shaft 1, but this groove is also provided. If the width between 1a is relatively small and it is difficult to provide the magnetized portion 18, a switch indicated by reference numeral 32 in FIG. 1 is provided corresponding to the measurement reference position. That is, when the nut 2 returns to the measurement reference position, it engages with and operates the actuator 32a of the switch 32 to generate the origin signal.

Next, a ball screw as a second embodiment of the present invention will be described with reference to FIGS. 6 and 7. The ball screw has the same structure as that of the ball screw according to the first embodiment shown in FIGS. 1 to 4 except for the parts described below, and therefore only the essential parts will be described. Further, in the following description, the same or corresponding components as those of the ball screw as the first embodiment are designated by the same reference numerals. The same applies to the third embodiment described later.

As shown in FIGS. 6 and 7, in the ball screw, each magnetized portion 16 provided in the detected portion 11 for detecting the movement amount is arranged in the direction along the screw groove 1 a of the screw shaft 1. The boundary 16a is parallel or substantially parallel to the axial direction of the screw shaft 1. Incidentally, FIG. 7 shows a state in which the detected part 11 provided along the spiral thread groove 1a is linearly expanded.

In this way, when the boundary 16a of each magnetized portion 16 is parallel to the axial direction of the screw shaft 1, the magnetic pole of the magnetizing head (not shown) for magnetizing is not changed, and The magnetizing work is extremely easy because it is completed by simply magnetizing the screw shaft 1 linearly in the axial direction with respect to the magnetizing head. As in the case of the ball screw as the first embodiment described above, when the boundaries of the magnetizing portions 16 are substantially perpendicular to the thread groove 1a, the magnetic poles of the magnetizing head are switched alternately, It is necessary to feed the screw shaft 1 in a spiral manner.

By the way, in the present embodiment, the detection of the nut 2 reaching the measurement reference position is performed by the switch 32 shown in FIG. Therefore, the detected portion 11 is not provided with a magnetized portion as an origin. With this configuration, the magnetizing work for forming the detected portion 11 is completed only by completing the above steps. However, a magnetized portion serving as the origin may be provided. In this case, after the magnetization of each magnetized portion 16 for detecting the movement amount is completed as described above, one side of the detected portion 11 shown in FIG. 7 is magnetized by a magnetic eraser (not shown) by a predetermined width. The magnetism is erased, and one magnetized portion (similar to the magnetized portion 18 in FIG. 3) to serve as a measurement reference is provided at the origin position. Then, a magnetoresistive element (not shown) for detecting the magnetized portion serving as the origin is provided in the case 12.

Also in the ball screw as the second embodiment having the above-mentioned configuration, the position of the nut 2 can be detected based on the same measurement principle as in the ball screw of the above-mentioned first embodiment. The description is omitted. As is apparent from FIG. 7, the two magnetoelectric conversion elements 19 and 20 provided in the case 12 to detect the magnetized portions 16 are attached so as to be parallel to the magnetized portions 16.

Next, a main part of a ball screw as a third embodiment of the present invention will be described with reference to FIG.

As shown in the figure, in the present embodiment, each magnetized portion 16 for detecting the amount of movement is provided with a non-magnetized portion 17 sandwiched therebetween. In this case, the size of the non-magnetized portion 17 in the direction along the thread groove 1a is set to be the same as that of the magnetized portion 16.

Each magnetized portion 16 is magnetized so that one side in the width direction of the thread groove 1a has an N pole and the other side has an S pole.

In such a configuration, in the configurations of the first and second embodiments described above, magnetic flux is generated between the magnetized portions 16 provided adjacent to each other, whereas the magnetic flux is generated by each magnetized portion 1. It occurs between 6 north and south poles. However, although the density of this magnetic flux becomes maximum in the central portion of the magnetized portion 16 in the direction along the thread groove 1a, it gradually weakens but reaches the range of the adjacent non-magnetized portion 17 as well. It becomes the minimum in the center of the section. Therefore, the waveforms obtained by the magnetoelectric conversion elements 19 and 20 are also positive and negative continuous sine waves, and the movement amount can be obtained based on the same principle as in the first and second embodiments.

By the way, in the above-mentioned first to third embodiments, the structure using magnetism is shown as the means for detecting the position of the nut 2, but as another embodiment, as the structure for optically detecting. Good. That is, for example, in FIG. 8, each of the magnetized portions 16 and 18 and the non-magnetized portion 17 is changed to a reflecting portion that reflects light and a non-reflecting portion, and each magnetoelectric conversion element 19 that functions as detection means. , 20 and the magnetoresistive element 15 are changed to optical means such as a reflection type photocoupler so that light is emitted from the optical means and reflected light from the reflecting portion is received, and based on the received reflected light. To generate a detection signal.

It should be noted that the present invention is not limited to the configurations of the above-described embodiments, and it goes without saying that a wide variety of configurations can be realized by appropriately combining the configurations included in these examples with each other.

In each of the above-described embodiments, the ball 3 circulates with the movement of the nut 2. However, a non-circulation type ball screw or a ball and a nut and a screw shaft are not directly provided. It goes without saying that the present invention can be applied to a normal screwing mechanism.

Furthermore, in the above-described position detection utilizing magnetism, two magnetoelectric conversion elements 19 and 20 are used for the purpose of determining the moving direction of the nut 2, but it is necessary to determine the moving direction. If there is no, this may be one.

If a high resolution for detecting the movement of the nut 2 is not required, the value of α shown in FIGS. 3, 7 and 8 is not calculated, and the detected peak value of the magnetism is simply calculated. It is enough to count with a counter.

[0048]

[Effect of device]

 As described above, in the feed mechanism according to the present invention, the detected portion which constitutes the position detecting means for detecting the position of the nut is arranged between the screw grooves of the screw shaft. The space occupied by is substantially limited to the occupied space of the magnetic sensor or the like serving as the detection means, and can be kept extremely small, which has the effect of contributing to downsizing of the device such as the XY table to be incorporated. In addition, since a separate linear scale or the like that has been conventionally used is unnecessary, the effect of reducing the cost can be achieved. Further, according to the present invention, since the screw shaft itself acts as a scale, there is an effect that the positioning of the nut is highly reliable.

[Brief description of drawings]

FIG. 1 is a perspective view of a ball screw as a first embodiment of the present invention.

2 is a vertical cross-sectional view of a part of the ball screw shown in FIG.

FIG. 3 is a plan view showing a state in which a part of the detected portion provided on the ball screw shown in FIG. 1 is linearly expanded and a detecting means for detecting the detected portion. is there.

FIG. 4 is a block diagram of a control system that controls the operation of the ball screw shown in FIG.

FIG. 5 is a diagram showing a waveform obtained by the magnetoelectric conversion element included in the ball screw shown in FIGS. 1 to 3.

FIG. 6 is a perspective view of a ball screw as a second embodiment of the present invention.

FIG. 7 is a plan view showing a state in which a part of the detected portion provided on the ball screw shown in FIG. 6 is linearly developed and a detecting means for detecting the detected portion. is there.

FIG. 8 shows a state in which a part of a detected portion provided on a ball screw as a third embodiment of the present invention is linearly developed, and a detecting means for detecting the detected portion. It is a top view shown.

FIG. 9 is a perspective view showing a conventional ball screw and its peripheral members.

10 is a vertical cross-sectional view of the ball screw shown in FIG.

[Explanation of symbols]

 1 Screw Shaft 1a Screw Groove 2 Nut 3 Ball (Rolling Element) 11 Detected Part 14 Magnetic Coating 15 Magnetoresistive Element 16 Magnetized Part (for Moving Distance Detection) 17 Non-Magnetized Part 18 Magnetized Part (Origin) 19, 20 Magnetoelectric conversion element

Claims (12)

[Scope of utility model registration request] 1. A feeding mechanism, wherein a detected portion is formed between the screw grooves of a screw shaft along the screw groove, and a detecting means for detecting the detected portion is provided on the nut side. 2. The feed mechanism according to claim 1, wherein the detected portion has an origin serving as a measurement reference. 3. The feeding mechanism according to claim 1, wherein the detected portion is multi-polarized along the screw groove, and the detecting means is a magnetic sensor. 4. The feed mechanism according to claim 3, wherein different magnetic poles are alternately arranged and magnetized along the thread groove. 5. A plurality of magnetized portions are arranged side by side along the thread groove with a non-magnetized portion sandwiched therebetween, and one side in the width direction of the thread groove of each magnetized portion is an N pole. The feed mechanism according to claim 3, wherein the other side is magnetized as an S pole. 6. The boundary of each magnetized portion in the direction along the thread groove is substantially perpendicular to the thread groove, according to any one of claims 3 to 5. Feeding mechanism. 7. The magnetized portion according to claim 3, wherein a boundary in a direction along the thread groove is substantially parallel to an axial direction of the screw shaft. Feeding mechanism. 8. The feed mechanism according to claim 3, wherein the magnetic sensor comprises a magnetoelectric conversion element. 9. The feed mechanism according to claim 3, wherein the magnetic sensor comprises a magnetoresistive element. 10. The feed mechanism according to claim 3, wherein a magnetic film is provided on the surface between the thread grooves, and the magnetic film is magnetized. 11. The detection section is provided with a reflection section that reflects light and a non-reflection section, and the detection section is an optical section that emits light and receives reflected light from the reflection section. The feed mechanism according to claim 1 or 2, wherein 12. The feed mechanism according to claim 1, wherein the feed mechanism is a ball screw.