JP2000205816A - Measuring device and measuring method - Google Patents

Abstract

(57) [Abstract] [Problem] Vibration from the floor, vibration generated inside the device,
Due to disturbance factors such as heat fluctuation due to ambient temperature change,
A measurement device capable of reducing a measurement error even if there is a measurement error factor, and a processing device and a measurement method including the same are provided. SOLUTION: An auxiliary body 6 is supported on a base 1 via an active vibration isolation table 15, and a first mirror 4 installed on a Z stage 3 and a first receiver 5 installed on the auxiliary body 6 are provided.
, The second mirror 4 ′ installed on the work spindle 7 and the second receiver 5 ′ installed on the auxiliary body 6
By measuring the distance, the measurement error is calculated, the feedback is provided to a control system (not shown), and the grinding amount of the work 8 is accurately measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring apparatus for measuring the amount of movement of a moving body which is used, for example, in a processing apparatus, and a measuring method therefor.

2. Description of the Related Art In recent years, a feed amount of a stage for holding a workpiece in a machining device such as a cutting process or a grinding process,
There is an increasing need to measure the amount of movement of a measuring element such as a shape measuring device or a moving stage that holds an object to be measured with high accuracy. It is known that measurement is possible. Such a device includes a fixed base, a moving body that reciprocates in one axis direction, a driving unit that drives the moving body, a measuring unit that measures a moving amount of the moving body, and a measurement value from the measuring unit. And control means for controlling the amount of movement of the moving object based on the control information. The moving body typified by the moving stage, the sliding guide with the fixed table, the rolling bearing guide, the movement in one axial direction is restricted by fluid bearing guide, etc., as a driving device to move the moving body,
A motor that can be easily controlled is generally used. Examples of the motor include a linear motor in which the moving body itself forms a part of the motor, and a rotary motor that moves the moving body via motion conversion means such as a feed screw. As the measuring means, a laser interferometer is often used to improve the moving accuracy of the moving body, and the control means detects a difference between the moving body drive command value and the measured value of the actual driving amount. Feedback control is performed to move the difference again. In general, a servomotor is often used to perform this control. The laser interferometer, which is a measuring unit, includes a laser light source, a light beam splitting unit, a receiver installed on a fixed base, and a reflecting mirror (hereinafter, referred to as a mirror) installed on a moving body. Since the movement of the moving object appears as a change in the interference fringe, the movement amount can be measured by measuring this with a receiver. The resolution of the movement amount measurement depends on the wavelength of the light source. For example, in a He-Ne laser (wavelength 632.8 nm), a resolution of several nm or less is possible.

However, in recent years,
The length measurement distance is expanding due to the increase in the size of the equipment, and the length measurement section of the processing equipment and shape measurement equipment as described above generates vibrations from the floor acting on the fixed table and the moving body, and generates inside the equipment. There is a problem that the relative measurement distance between the mirror and the receiver of the laser interferometer, which is the measuring means, fluctuates due to disturbance factors such as vibration, heat fluctuation due to ambient temperature change. In particular, when there is a factor of generating vibration or heat inside the apparatus and the rigidity of the fixed base is low, the influence on the length measuring unit appears very remarkably. Assuming that the distance between the mirror of the length measuring unit and the receiver is D, and the displacement in the length measuring direction caused by the above-described factors is δ, the reading of the length measurement value is D + δ, and the error of δ is greater than the true value D. This value is sent as an uncorrectable error to a subsequent control system and used as a reference for feedback control. Therefore, an object of the present invention is to provide a measuring apparatus capable of reducing a measuring error even if there is the above-mentioned measuring error factor, a processing apparatus including the measuring apparatus, and a measuring method.

In order to solve the above-mentioned problems and to achieve the object, according to the first aspect of the present invention, a fixed base, a movable body attached to the fixed base and reciprocating in one axis direction,
A driving unit for moving the moving body in one axis direction, a measuring unit for measuring a moving amount of the moving body, and a measuring device including a control unit for controlling the driving unit and the measuring unit, In order to make it hard to receive disturbance, an auxiliary body is supported on the fixed base via an elastic member, a first mirror installed on the moving body, and a second mirror installed on the auxiliary body facing the mirror. One receiver, a second mirror attached to the fixed base and installed on a plane orthogonal to the moving direction of the moving body, and a second mirror installed on the auxiliary body so as to face the second mirror. It is characterized by comprising a receiver and measuring means for measuring the distance between each mirror and the receiver. According to a second aspect of the present invention, the auxiliary body held by the fixing base according to the first aspect is a low thermal expansion member having extremely high rigidity. According to a third aspect of the present invention, the elastic member according to the first or second aspect is an active-controlled anti-vibration table. In the invention of claim 4,
The measuring device according to any one of claims 1 to 3,
The optical path in which the first mirror and the first receiver are installed and the optical path in which the second mirror and the second receiver are installed are arranged in parallel. Also,
According to a fifth aspect of the present invention, in the measuring device according to any one of the first to third aspects, all of the first mirror, the first receiver, the second mirror, and the second receiver are arranged on the same optical path. It is characterized by having. Claim 6
The present invention is characterized in that it is a machining device provided with the measuring device according to any one of claims 1 to 5.
According to the seventh aspect of the present invention, the measurement device or the processing device according to any one of the first to sixth aspects is used to measure a length measurement value between a first mirror and a first receiver provided in the measurement device. And measuring the length measurement values of the second mirror and the second receiver, and measuring the moving amount of the moving body from the measured values of both. (Function) In the first aspect of the present invention, both the first and second receivers are installed on the auxiliary body, and the auxiliary body itself is connected to the fixed base via an elastic member so as not to be disturbed by the above-described length measuring unit. The distance L between the first and second receivers
Is a metric with a stable length. First and second receiver distance L is, the true distance D ₂ between the true distance D ₁ of the first mirror and the first receiver and a second mirror second receiver, a first mirror It is represented by the sum of the true distance D ₃ of the second mirror, and _{L = D 1 + D 2 +} D 3. Here, the length measurement values measured by the first mirror and the first receiver are changed by the movement of the moving body, but include the displacement error δ in the length measurement direction caused by the above-described factors. Long value D ₁ + δ
As shown. On the other hand, the length measurement value measured by the second mirror and the second receiver does not move the second mirror, but includes a displacement error in the length measurement direction caused by the above-described factors. In equation (3), L is considered to be invariant as a measurement criterion, and indicates the measured value of D ₂ −δ. Thus, by measuring the distance constant second mirror and a second receiver, without measuring a first mirror the true distance D ₃ of the second mirror, calculating a displacement error δ of the length measurement direction Then, feedback to the control system can be performed, and the position of the moving body can be measured with high accuracy. Claim 2
In the invention described in (1), a low thermal expansion member having high rigidity is used for the material of the auxiliary body. Therefore, the apparatus is less susceptible to disturbances due to vibration or heat of the apparatus, and measurement accuracy is further improved. According to the third aspect of the present invention, by using the vibration-isolating table which is actively controlled as the elastic member, it is less likely to be disturbed by the vibration of the device, and the measurement accuracy is further improved. According to a fourth aspect of the present invention, in the measuring device according to any one of the first to third aspects, the length measurement system including the first mirror and the first receiver, and the second mirror and the second receiver are used. Since the optical paths installed in the configured length measuring systems are parallel and not on the same optical path, the applicable range of the measuring unit is widened. According to the fifth aspect of the present invention, the first to third aspects are provided.
In the measuring device according to any one of the above, by arranging the first and second mirrors and the receiver on the same optical path, the configuration of the measuring device is simplified and the manufacture is facilitated.
In the invention according to claim 6, by attaching the measuring device according to any one of claims 1 to 5 to a processing machine,
Processing accuracy can be improved. According to the seventh aspect of the present invention, a desired movement amount can be accurately measured by the measuring device or the processing device according to any one of the first to sixth aspects.

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a conceptual diagram of a grinding device showing an embodiment of the present invention. The grinding apparatus includes a base 1, a work spindle 7 on which a work 8 is placed via hiring, an X stage 9 capable of moving the work spindle 7 in a uniaxial direction in the horizontal direction, a diamond grindstone 10 for grinding the work, A tool spindle 11 for rotating the diamond grindstone 10, a Z stage 3 capable of moving the tool spindle 11 in a single axial direction, a column 2 provided with the Z axis stage 3 and installed on a base 1, and a laser light source 12 and the first mirror 4
, A first receiver 5, a length measuring system composed of a second mirror 4 'and a second receiver 5', a vibration isolator 14 for a grinding device main body, an auxiliary body 6, and an auxiliary body 6. And an active vibration isolation table 15 which is supported independently of the grinding device. The auxiliary body 6 uses a super-invar, which is a low thermal expansion member, and performs a structural analysis by a finite element method to achieve high rigidity in the structural design of the device, so that even if disturbance vibration is transmitted, Care is taken to keep the amplitude small. Further, in order to prevent the vibration generated due to the rotation of the diamond grindstone 10 and the like during the processing of the present grinding device from being transmitted to the auxiliary body 6 which is the measurement reference,
The auxiliary body is supported by the grinding apparatus main body by three small active vibration isolation tables 15. Furthermore, taking into account that the frequency of the vibration generated by the rotation of the diamond grindstone 10 during the processing of the present grinding device is about 30 to 50 Hz,
In order to avoid resonance, the natural frequency of the auxiliary body 6 is designed and manufactured so as to be a value several times the vibration frequency generated by the rotation of the diamond grindstone 10. Next, the processing operation of the grinding apparatus will be described. First, a work 8 which is a workpiece is placed on a work spindle 7 through hiring. Work spindle 7 is X stage 9
And can move in one axis in the horizontal direction. A diamond grindstone 10 serving as a grinding tool is mounted on a tool spindle 11 and has a Z stage 3.
It is installed in. At the time of grinding, the rotating work 8 placed on the work spindle 7 moves in the X direction with the operation of the X stage 9,
By driving the stage 3 to move the rotating diamond grindstone 10 attached to the tool spindle 11 up and down, the work 8 can be formed into an axially symmetric three-dimensional shape. Here, the first and second receivers 5 and 5 'are both mounted on the auxiliary body 6, and the auxiliary body 6 itself is actively removed from the base 1 and the column 2 so as not to be affected by the disturbance of the length measuring section. Because it is supported via the shaking table 15, the first,
The distance L between the second receivers 5, 5 'is a metric with a stable length. First and second receiver 5,5' distance L is, the first mirror 4 the true distance D ₁ of the first receiver 5 true of the second mirror 4 'and the second receiver 5' the distance D _2, expressed by the sum of the true distance D ₃ of the first mirror and the second mirror, and _{L = D 1 + D 2 +} D 3. Here, as described in the section of means for solving the problem, the distance between the first mirror 4 and the first receiver 5 and the distance between the second mirror 4 'and the second receiver 5' are measured. By doing so, it is possible to measure the amount of movement, that is, the amount of processing, of the diamond grindstone 10 attached to the Z stage 3 as a moving body via the tool spindle 11. Then, by feeding back the measured machining amount to the control system, the grinding amount of the work 8 can be accurately measured. Next, the length measurement system used in the present embodiment will be described. The laser beam for length measurement emitted from the laser light source 12 is mirror 1
3 divides into two directions (up and down directions). The downwardly directed laser beam passes through a second receiver 5 'provided below the auxiliary body 6, is reflected by a second mirror 4' provided below the work spindle 7, and is again returned to the second receiver 4 '. Returning to 5 ', the distance (D2) between the receiver 5' and the mirror 4 'is constantly measured. On the other hand, the upwardly directed laser beam passes through a first receiver 5 installed above the auxiliary body 6 and passes through a tool spindle 1 mounted on the Z stage 3.
1. The distance (D1) between the first receiver 5 installed on the auxiliary body 6 and the first mirror 4 on the Z stage 3 is constantly measured after being reflected by the first mirror 4 installed on the upper part. A change in the Z direction due to the movement of the X stage 9 accompanying the processing of the work 8 is detected from D2, and the position of the Z stage 3 is controlled so as to cancel the change. Thus, a change in the Z direction (vertical direction) due to the feed of the X stage 9 can be measured, and the distance between the work 8 and the diamond grindstone 10 can be corrected to a value calculated from the work shape.

As described above, according to the present invention, it is possible to eliminate the influence of disturbance factors such as vibration and thermal displacement on the length measurement as much as possible. When applied to the length measurement of a processing device or a measuring device, there is an effect of improving the processing accuracy and the measurement accuracy of a workpiece.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an embodiment in which the present invention is applied to a grinding device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Base 2 ... Column 3 ... Z stage 4 ... 1st mirror 4 '... 2nd mirror 5 ... 1st receiver 5' ... 2nd Receiver 6 ... Auxiliary body 7 ... Work spindle 8 ... Work (workpiece) 9 ... X stage 10 ... Diamond grindstone 11 ... Tool spindle 12 ... For laser length measurement Light source 13 ・ ・ ・ Mirror 14 ・ ・ ・ Vibration isolation table for main body 15 ・ ・ ・ Active vibration isolation table

Claims (7)

[Claims] 1. A fixed base, a moving body attached to the fixed base and reciprocating in one axis direction, a driving means for moving the moving body in one axis direction, and a measuring means for measuring an amount of movement of the moving body. And a control device for controlling the driving means and the measuring means, wherein the auxiliary body held on the fixed base via an elastic member, and a plane orthogonal to the moving direction of the moving body. The installed first reflecting mirror, the first receiver installed on the auxiliary body so as to face the reflecting mirror, and the second receiver installed on a plane orthogonal to the moving direction of the moving body on the fixed base. Two reflecting mirrors, a second receiver installed on the auxiliary body so as to face the second reflecting mirror, and a measuring unit that measures the distance between the first reflecting mirror and the first receiver, Measuring hand that measures the distance between the second reflector and the second receiver And a step. 2. The measuring device according to claim 1, wherein the auxiliary body held by the fixed base is a low thermal expansion member having extremely high rigidity. 3. A measuring apparatus, characterized in that the elastic member according to claim 1 is an active-controlled anti-vibration table. 4. The measuring apparatus according to claim 1, wherein an optical path in which the first reflector and the first receiver are installed, and a second reflector and the second receiver are installed. A measuring device, wherein the optical paths are arranged in parallel. 5. The measuring device according to claim 1, wherein the first reflecting mirror, the first receiver, the second reflecting mirror, and the second receiver are arranged on the same optical path. A measuring device characterized by the above-mentioned. 6. A machining device comprising the measuring device according to claim 1. 7. The measurement device according to claim 1, wherein a measurement value of a first reflection mirror and a first receiver provided in the measurement device, and a measurement value of a second reflection mirror are provided. A measurement method comprising: measuring a length measurement value with a second receiver; and measuring a moving amount of the moving body from the measured values.