JP2012177672A - Physical amount measurement device for rotary machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize structure for measuring deviations x, y, and z and inclinations φx and φz of five directions of a rotary member to which an encoder 1a is externally engaged and fixed in a state where the number of sensors 10 and 10 to be used by being combined with the encoder 1a is reduced to only three.SOLUTION: As an encoder 1a, the one obtained by forming a plurality of characteristic change combination parts 3a and 3a at equal pitches in the circumferential direction on the outer peripheral surface which is a surface to be detected is used. The respective characteristic change combination parts 3a and 3a consist of a first recessed groove 11a and a second recessed groove 11b inclined to the directions opposite to each other relative to the axial direction of the encoder 1a. Detection parts of three sensors 10 and 10 are made to face each other on the parts where phases in the circumferential direction are different from each other of the outer peripheral surface of the encoder 1a. Thus, deviations x, y, and z and inclinations φx and φz of five directions are able to be calculated on the basis of information to be obtained from output signals of the respective sensors 10 and 10.

Description

  The present invention relates to displacements and inclinations generated in rotating members such as main shafts of various machine tools such as lathes, milling machines, machining centers, and rotating bearing members for constituting rolling bearing units for supporting wheels of automobiles. It is used to measure physical quantities such as loads and moments acting on the.

  The main axis of a machine tool is the most main axis of the machine tool that gives a highly accurate rotational motion to the tool or workpiece while the tool or workpiece is attached to the tip. During machining of the workpiece, a load based on machining resistance is applied to the main shaft. This load decreases as the machining feed rate decreases and increases as it increases. Therefore, if the machining feed rate is adjusted so that the load falls within a predetermined range, the machining feed rate can ensure the machining efficiency and the durability of the tool and the quality of the workpiece. Can be within the proper range. In addition, when the processing conditions such as the processing feed rate are constant, the load increases as the cutting performance (sharpness) of the tool deteriorates. Therefore, if the magnitude of the load is observed in relation to the machining conditions, it can be known that the tool has reached the end of its life, and the yield is deteriorated by continuing the processing with the defective tool that has reached the end of the life. Can be prevented. Further, if the load is continuously observed in association with the machining conditions, it becomes possible to identify the cause when an accident such as tool breakage occurs.

  For such a purpose, a device having a structure described in Patent Document 1, for example, is conventionally known as a device for measuring a load applied to a rotating shaft such as a main shaft of a machine tool. The load measuring apparatus described in Patent Document 1 includes a plurality of quartz piezoelectric type load sensors arranged in series with respect to the direction of load application, and supports a cutting tool based on measurement signals of these load sensors. The load (cutting resistance) applied to the fixed rotating shaft is measured. In the case of such a load measuring device described in Patent Document 1, since an expensive quartz piezoelectric load sensor is used, it is inevitable that the cost of the load measuring device as a whole increases.

  On the other hand, Patent Document 2 describes an invention relating to a rolling bearing unit with a load measuring device, which includes a magnetic encoder and sensor, which can be procured at a lower cost than a quartz piezoelectric load sensor. For example, in paragraphs [0066] to [0068] of Patent Document 2, an encoder 1 as shown in FIG. 10 is used, and the amount of displacement in the axial direction of a rotating member that concentrically supports the encoder 1 is extended. A technique for measuring an axial load applied to a rotating member is described.

  The encoder 1 is made entirely cylindrical by a magnetic metal plate such as a steel plate. In the intermediate portion in the axial direction of the encoder 1, a first through hole 2a that is a first characteristic changing portion and a second through hole that is a second characteristic changing portion that are provided at a predetermined pitch in the circumferential direction. A plurality of characteristic change combination portions 3 and 3 including holes 2b are provided at equal pitches in the circumferential direction. The first through hole 2a and the second through hole 2b constituting each of the characteristic change combination units 3 and 3 are inclined at the same angle in opposite directions with respect to the axial direction of the encoder 1. Yes. In other words, the inclination angles of the first through-hole 2a and the second through-hole 2b with respect to the axial direction of the encoder 1 have the same absolute value and positive and negative signs (inclination directions). They are opposite to each other. Such an encoder 1 is fixed to a part of a rotating member such as a main shaft of a machine tool concentrically with the rotating member. At the same time, in a state where a magnetic detection type sensor is supported on a part of a stationary member provided in a portion adjacent to the rotating member, the detection unit of the sensor is connected to the outer peripheral surface of the encoder 1 through a minute gap. And make them face each other.

In this state, when the encoder 1 rotates together with the main shaft, the detection unit of the sensor scans the outer peripheral surface of the encoder 1 which is a detected surface. Since the magnetic characteristics of the outer peripheral surface of the encoder 1 change in the circumferential direction due to the presence of the first and second through holes 2a and 2b, the output signal of the sensor changes as the encoder 1 rotates. Change. For example, when the detection unit of this sensor scans the chain line a position in FIG. 11A on the outer peripheral surface of the encoder 1, the output signal of this sensor changes as shown in FIG. 11B. To do. In FIG. 11 (b), a period between a pair of pulses generated based on a pair of first through holes 2a and 2a constituting a pair of characteristic change combination portions 3 and 3 adjacent in the circumferential direction. Is the total period L ₁ . Further, the first, second double holes 2a, 2b to the period between a pair of pulses with sub-periods s ₁ generated based on configuring the same characteristic change combination unit 3. When the detection unit of the sensor scans the chain line b position, the pulse period ratio s ₁ / L ₁ , which is the ratio between the partial period s ₁ and the total period L ₁ , becomes a relatively small value. On the other hand, when the detection unit of the sensor scans the position of the chain line in FIG. 11 (a), the output signal of the sensor changes as shown in FIG. 11 (c). The pulse cycle ratio s ₂ / L ₂ , which is the ratio between the partial cycle s ₂ and the total cycle L ₂ , is a relatively large value.

  As described above, the pulse cycle ratio s / L related to the output signal of the sensor changes depending on the axial position (the width direction position of the detected surface) of the outer peripheral surface of the encoder 1 scanned by the detection unit of the sensor. And this axial position changes with the axial displacement of the rotating member which fixed the encoder. Therefore, if software that incorporates an arithmetic expression for calculating the axial displacement amount of the rotating member is installed in an arithmetic unit for processing the output signal of the sensor, the arithmetic unit calculates the pulse period. Based on the ratio s / L, the axial displacement amount of the rotating member can be calculated. Further, when the rotating member is rotatably supported by a rolling bearing to which a preload is applied, the axial displacement amount of the rotating member changes according to the magnitude of the axial load applied to the rotating member. In other words, there is a reproducible and reproducible correlation between the axial load applied to the rotating member and the axial displacement of the rotating member. And this correlation is calculated | required not only by calculation by the elastic contact theory widely known in the field of a rolling bearing but also by experiment. Therefore, if software that incorporates an arithmetic expression for calculating the axial load in consideration of the correlation is installed in the calculator, the calculator calculates the pulse period ratio s / L based on the pulse period ratio s / L. The axial load applied to the rotating member can be calculated.

  By the way, when the tool fixed to the front-end | tip part of the said main axis | shaft is a milling machine or an end mill, for example, although an axial load is added to this main axis | shaft, a radial load and a moment are added to a bigger ratio. Therefore, in such a case, not only the axial load but also the radial load and moment (or displacement and inclination of the spindle generated based on them) are measured, and these are measured at the above-mentioned machining feed rate. It can be said that it is preferable to use it for adjustment and the like from the viewpoint of performing this adjustment and the like at a higher level. On the other hand, in Patent Document 3, a total of five directions of load and moment (displacement and displacement) including an axial load (displacement), a radial load (displacement) in two directions, and a moment (tilt) in two directions applied to the rotating member. An invention relating to a physical quantity measuring apparatus capable of measuring (tilt) is described. Therefore, if the present invention is applied to a machine tool, the above-described adjustment of the machining feed rate can be performed at a higher level.

However, in the case of the invention described in the above-mentioned Patent Document 3, it is necessary to use a total of six sensors, two of which are used in combination with three encoders. For this reason, the cost of each of these sensors increases. Further, it becomes difficult to make the detection parts of all the sensors face a predetermined portion of the detection target surface of the encoder with high accuracy, and there is a possibility that productivity is deteriorated accordingly.
In addition, the following patent document 4 exists as another prior art document relevant to this invention.

JP 2002-187048 A JP 2006-317420 A JP 2008-64731 A JP 2010-54256 A

  In view of the circumstances as described above, the present invention reduces the number of sensors used in combination with the encoder to less than six, and further, the displacement and inclination of the rotating member in five directions (the five directions applied to the rotating member). The invention was invented to realize a structure capable of measuring external force.

The physical quantity measuring device for a rotary machine of the present invention includes a rotary machine, an encoder, a sensor, and a calculator.
Among these, the rotating machine includes a stationary member that does not rotate, and a rotating member that is rotatably supported with respect to the stationary member by a plurality of rolling bearings each provided with a preload.
The encoder is supported and fixed to a part of the rotating member and has a detected surface concentric with the rotating member. The detected surface includes a plurality of characteristic change combination portions arranged at equal pitches in the circumferential direction, and each of the characteristic change combination portions is separately arranged at a predetermined pitch in the circumferential direction. It consists of a first characteristic change part and a second characteristic change part that are different in inclination angle in consideration of positive and negative signs with respect to the width direction of the surface.
Further, the sensor is supported by the stationary member in a state where the detection portion faces the detected surface. And each said characteristic change part changes an output signal in the moment of passing through the part which the said detection part opposes among the said to-be-detected surfaces.
Further, the computing unit processes an output signal of the sensor.
In particular, in the physical quantity measuring device for a rotating machine according to the present invention, only three of the sensors are provided, and the detection units of these sensors are arranged in portions where the phases in the circumferential direction are different from each other on the detected surface. They are facing each other. Further, the computing unit is based on the information obtained from the output signals of the sensors, and includes the displacement of the encoder with respect to the stationary member in three orthogonal directions and the inclination in two orthogonal directions. It has a function of calculating part or all of it.
In addition, it is preferable that the opposing position of the detection part of each sensor with respect to the detected surface is a circumferentially equidistant position of the detected surface.
In addition, as the displacement in the three directions orthogonal to each other, for example, a three-dimensional orthogonal coordinate system in which the y-axis of the x-axis, y-axis, and z-axis orthogonal to each other coincides with the central axis of the stationary member is set. In this case, the displacement x in the x-axis direction, the displacement y in the y-axis direction, and the displacement z in the z-axis direction can be employed. As the inclination in the two directions orthogonal to each other, the inclination φ _x around the x axis and the inclination φ _z around the z axis when the three-dimensional orthogonal coordinate system is set can be adopted.

  When carrying out the present invention, as in the invention described in claim 2, for example, the arithmetic unit is used when calculating a part or all of the displacement in the three directions and the inclination in the two directions. The information obtained from the output signals of the sensors includes the pulse period ratio of the output signals of the sensors and the output signals of the sensors included between the output signals of the sensors. A phase difference ratio between pulses generated based on one characteristic changing unit is employed.

  Further, when the present invention is carried out, preferably, the inclination angle of the first characteristic change portion with respect to the width direction of the detected surface is set to zero as in the invention described in claim 3. That is, only the second characteristic changing portion is inclined with respect to the width direction of the detected surface.

  Further, when the present invention is implemented, preferably, as in the invention described in claim 4, the computing unit includes a part of the displacement in the three orthogonal directions and the inclination in the two orthogonal directions. Alternatively, based on all, an external force acting between the stationary member and the rotating member (for example, the load Fx in the x-axis direction and the load Fy, z in the y-axis direction when the three-dimensional orthogonal coordinate system is set) A function of calculating a part or all of the axial load Fz, the moment Mx around the x-axis, and the moment Mz around the z-axis) is provided.

According to the physical quantity measuring device for a rotating machine of the present invention configured as described above, the displacement of the encoder relative to the stationary member (the portion of the rotating member on which the encoder is supported and fixed) in three directions orthogonal to each other, and the mutual A part or all of the inclinations in two orthogonal directions can be obtained. In addition, in the case of the invention described in claim 4, an external force acting between the stationary member and the rotating member is required. In particular, in the case of the present invention, the number of sensors used in combination with the encoder can be reduced to only three. For this reason, the cost of each of these sensors can be suppressed. Furthermore, it becomes relatively easy to make the detection parts of all the sensors face a predetermined portion of the detection surface of the encoder with high accuracy, and the productivity can be improved accordingly.
Further, if the configuration of the invention described in claim 3 is adopted, compared to a case where a configuration in which the inclination angles of both the first and second characteristic change portions with respect to the width direction of the detected surface are not zero is adopted, The amount of calculation when calculating the displacement of the encoder can be reduced. For this reason, it is possible to improve the calculation speed of the displacement and to reduce the cost by reducing the specifications of the calculator.

Sectional drawing which shows the 1st example of embodiment of this invention. The schematic perspective view which shows the arrangement | positioning relationship between an encoder and three sensors. The expanded view which shows a part of to-be-detected surface of an encoder. The perspective view which takes out a sensor unit and shows in the state (a) which is not coat | covering the sensor mounting part of a front-end | tip, and the state (b) covered. The figure which shows the circumferential direction position of a sensor. The figure which shows the output signal of one sensor by the state (a) before a displacement and inclination of 5 directions arise in an encoder, and the back state (b). The figure which shows the state which has produced the phase difference between the output signals of two sensors. The schematic perspective view which shows the 2nd example of embodiment of this invention which shows the arrangement | positioning relationship between an encoder and three sensors. The expanded view which shows a part of to-be-detected surface of an encoder. The perspective view of the encoder known conventionally. The schematic diagram for demonstrating the reason which can measure a physical quantity based on the output signal of a sensor.

[First example of embodiment]
A first example of an embodiment of the present invention corresponding to claims 1, 2, and 4 will be described with reference to FIGS. This example is an example in which the present invention is applied to a structure for measuring a displacement and an inclination of a main shaft 4 that constitutes a machine tool and a load and a moment that are external forces acting on the main shaft 4. is there. In the machine tool, the main shaft 4 is rotatably supported by a multi-row rolling bearing unit 6 on the inner diameter side of a housing 5 which is a stationary member, and the main shaft 4 is rotatably driven by an electric motor 7. Among the plurality of rolling bearings 8a to 8d constituting the multi-row rolling bearing unit 6, two rolling bearings 8a and 8b arranged near the distal end and two rolling bearings 8c and 8d arranged near the proximal end. In addition to applying contact angles opposite to each other, a preload is applied to each of the rolling bearings 8a to 8d.

  During operation of the machine tool, a tool (not shown) fixed to the tip end portion (left end portion in FIG. 1) of the main spindle 4 is pressed against the workpiece while rotating at an appropriate rotation speed, and cutting or the like is applied to the workpiece. The processing of. When machining is performed in this manner, a load and a moment in each direction are applied to the main shaft 4 as a reaction of pressing the tool against the workpiece. In the structure of this example, the displacement and inclination of the main shaft 4 based on the loads and moments in these directions and the loads and moments in these directions as required are obtained. For this purpose, the structure of this example includes one encoder 1a, three sensor units 9, and a calculator (not shown).

  Of these, the encoder 1 a is fitted and fixed between the rolling bearings 8 b and 8 c constituting the multi-row rolling bearing unit 6 at the portion near the tip of the intermediate portion of the main shaft 4. The encoder 1a also serves as an inner ring spacer, is made of a magnetic metal such as steel, and has a cylindrical shape as a whole. A plurality of characteristic change combination portions 3a and 3a are formed at equal pitches in the circumferential direction at the axially central portion of the outer peripheral surface of the encoder 1a, which is the detected surface. Each of these characteristic change combination parts 3a and 3a is spaced apart by a predetermined pitch with respect to the circumferential direction and has a linear first concave groove 11a that is a first characteristic change part and a linear shape that is a second characteristic change part. The second concave groove 11b. The first groove 11a and the second groove 11b are inclined at the same angle in opposite directions with respect to the axial direction of the encoder 1a. In other words, the inclination angles of the first through-hole 2a and the second through-hole 2b with respect to the axial direction of the encoder 1a are equal in absolute value and have positive and negative signs (inclination directions). They are opposite to each other.

  Each of the three sensor units 9 and 9 is formed by embedding a sensor 10 at the tip of a synthetic resin holder 12 as shown in detail in FIG. The sensor 10 includes a magnetic sensing element such as a Hall IC, a Hall element, an MR element, and a GMR element constituting a detection unit, and a permanent magnet. Such three sensor units 9 and 9 are supported by the housing 5 in a state in which the detection portions of the sensors 10 and 10 are close to and opposed to three places at equal intervals in the circumferential direction of the detected surface. It is fixed. In this state, when the encoder 1 a rotates together with the main shaft 4, the detection units of the sensors 10 and 10 scan the outer peripheral surface of the encoder 1. Since the magnetic characteristics of the outer peripheral surface of the encoder 1 change in the circumferential direction due to the presence of the first and second concave grooves 11a and 11b, the sensors 10, 10 are rotated with the rotation of the encoder 1a. Output signal changes.

In the case of this example, a three-dimensional coordinate system including an x-axis, a y-axis, and a z-axis orthogonal to each other is set for the machine tool in which the encoder 1a and the sensor units 9 and 9 are assembled as described above. . The y-axis of this three-dimensional coordinate system is the left-right direction axis in FIG. 1, which coincides with the central axis of the housing 5, and the x-axis is also the front-back direction axis in FIG. The axis is the axis in the vertical direction in FIG. In the case of this example, the central axis of the main shaft 4 coincides with the central axis of the housing 5 in a neutral state where no external force is applied to the main shaft 4. For this reason, in this neutral state, the central axis of the main shaft 4 is an axis coinciding with the y-axis. The origin O of the three-dimensional coordinate system is located at the geometric center point of the encoder 1a in the neutral state. However, in FIG. 1, for convenience of illustration, the origin O is arranged on the y axis at a position greatly deviated to the left from the geometric center point of the encoder 1a. Further, the circumferential position (angle) θ around the y-axis is set as shown in FIG. In the case of this example, the detection units of the three sensors 10 and 10 are disposed at a zero position in the y-axis direction, and θ ₁ = 0 degrees, θ ₂ = 120 degrees, and θ ₃ = 240 in the circumferential direction. It is arranged in three places.

Further, the computing unit is configured to determine the displacement x in the x-axis direction, the displacement y in the y-axis direction, and the z-direction of the encoder 1a relative to the housing 5 based on information obtained from the output signals of the sensors 10 and 10. It has a function of calculating an axial displacement z, an inclination φ _x around the x axis, and an inclination φ _z around the z axis by a predetermined arithmetic expression. First, the contents of the predetermined arithmetic expression will be described below.

この（１）式の右辺中のＲ、δの意味は、それぞれ以下の通りである。
Ｒ：被検出面である前記エンコーダ１ａの外周面の半径。
δ：前記各センサ１０、１０の検出部のｚ軸からのｙ軸方向のずれ量。
本例の場合、このうちのずれ量δは零（δ＝０）である（実際には不可避な寸法誤差や組付誤差がある為、δ≠０となる事も予想されるが、その場合でもδは十分に小さな値となる為、δ＝０と仮定しても、その影響を無視できる）。そうすると、前記（１）式は、次の（２）式で表す事ができる。

又、この（２）式を変形して、次の（３）式が得られる。

更に、この（３）式に、θ₁＝０度、θ₂＝１２０度、θ₃＝２４０度を代入すると、次の（４）式が得られる。

Now, in the outer peripheral surface of the encoder 1a, the y-axis direction displacement of the portion of θ ₁ = 0 ° is y ₁ , the y-axis direction displacement of the portion of θ ₂ = 120 ° is y _2, and θ ₃ = 240 °. The y-axis direction displacement of the portion is assumed to be y ₃ . In this case, the relationship of the following equation (1) is established between each displacement y _i (i = 1, 2, 3) and the displacement y and the inclinations φ _x and φ _z .

The meanings of R and δ in the right side of the equation (1) are as follows.
R: radius of the outer peripheral surface of the encoder 1a which is a detected surface.
δ: The amount of deviation in the y-axis direction from the z-axis of the detectors of the sensors 10 and 10.
In the case of this example, the deviation amount δ is zero (δ = 0) (in reality, it is expected that δ ≠ 0 because there are inevitable dimensional errors and assembly errors, but in that case However, since δ is a sufficiently small value, the effect can be ignored even if δ = 0. Then, the formula (1) can be expressed by the following formula (2).

Further, the following equation (3) is obtained by modifying the equation (2).

Further, by substituting θ ₁ = 0 degrees, θ ₂ = 120 degrees, and θ ₃ = 240 degrees into the expression (3), the following expression (4) is obtained.

この（５）式の右辺中のＰ、αの意味は、それぞれ以下の通りである。
Ｐ：前記エンコーダ１ａの円周方向に関する前記各特性変化組み合わせ部３ａ、３ａのピッチ。
α：第一凹溝１１ａ及び第二凹溝１１ｂの、前記エンコーダ１ａの軸方向に対する傾斜角度（図示の例では、４５度）。
尚、前記（５）式の右辺中のδは、前述した通り、零（δ＝０）である。前記各センサ１０、１０の出力信号に関する自己位相差比ε（０）、ε（１２０）、ε（２４０）は、前記（５）式中のθ_iに、それぞれの配置角度θ₁＝０度、θ₂＝１２０度、θ₃＝２４０度を代入すると共に、同式中のα、δに、α＝４５度、δ＝０を代入する事により、次の（６）〜（８）式で表される。

On the other hand, when displacements x, y, z and inclinations φ _x , φ _z in the five directions are generated in the encoder 1a, the phases of the output signals of the sensors 10, 10 are accordingly changed, as shown in FIG. → Changes as illustrated in (b). Here, paying attention to the self-phase difference k, which is the phase change amount of the pulse p ₁ generated based on the first concave grooves 11a, 11a included in the output signal, this self-phase difference k and the entire period The ratio k / L with L is defined as the self phase difference ratio ε (θ _i ) (i = 1, 2, 3). The relationship of the following equation (5) is established between such a self-phase difference ratio ε (θ _i ) and the displacements x, y, z and inclinations φ _x , φ _{z in the} five directions.

The meanings of P and α in the right side of the equation (5) are as follows.
P: The pitch of the characteristic change combination units 3a and 3a in the circumferential direction of the encoder 1a.
α: An inclination angle of the first concave groove 11a and the second concave groove 11b with respect to the axial direction of the encoder 1a (45 degrees in the illustrated example).
Note that δ in the right side of the equation (5) is zero (δ = 0) as described above. The self-phase difference ratios ε (0), ε (120), and ε (240) related to the output signals of the sensors 10 and 10 are set to θ _i in the equation (5), and the respective arrangement angles θ ₁ = 0 degrees. , Θ ₂ = 120 degrees, θ ₃ = 240 degrees, and by substituting α = 45 degrees and δ = 0 into α and δ in the same expression, the following expressions (6) to (8) It is represented by

このうちの（９）式は、θ₁＝０度の位置とθ₂＝１２０度の位置とに配置した２個のセンサ１０、１０の出力信号同士の間の相互位相差比「ε（１２０）−ε（０）」を表す式であり、前記（１０）式は、θ₁＝０度の位置とθ₃＝２４０度の位置とに配置した２個のセンサ１０、１０の出力信号同士の間の相互位相差比「ε（２４０）−ε（０）」を表す式である。これら（９）式及び（１０）式をまとめて整理すると、次の（１１）式が得られる。

更に、この（１１）式を変形して、次の（１２）式が得られる。

Further, when displacements x, y, z and inclinations φ _x , φ _z in the five directions occur in the encoder 1a, two of the three sensors 10, 10 are arbitrarily selected accordingly. FIG. 7 illustrates between the output signals of the sensors 10 and 10 (between the pulses p ₁ and p ₁ generated based on the first concave grooves 11a and 11a included in the output signals). A phase difference (mutual phase difference) m occurs. Here, the ratio m / L between the mutual phase difference m and the total period L is defined as a mutual phase difference ratio. Such a mutual phase difference ratio is obtained by taking the difference between two expressions arbitrarily selected from the expressions (6) to (8), for example, the following expressions (9) and (10): It can be expressed like a formula.

Of these, the expression (9) is obtained by calculating the mutual phase difference ratio “ε (120) between the output signals of the two sensors 10 and 10 arranged at the position θ ₁ = 0 degree and the position θ ₂ = 120 degrees. ) −ε (0) ”, where the output signals of the two sensors 10 and 10 arranged at the position of θ ₁ = 0 degrees and the position of θ ₃ = 240 degrees Is a formula representing a mutual phase difference ratio “ε (240) −ε (0)”. When these equations (9) and (10) are arranged together, the following equation (11) is obtained.

Further, this equation (11) is modified to obtain the following equation (12).

In the case of this example, the computing unit calculates the displacements x, y, z and inclinations φ _x , φ _z in the five directions based on information obtained from the output signals of the sensors 10, 10 (4). It calculates with a type | formula and said Formula (12).
At this time, the computing unit first calculates the displacement y _i (i = 1, 2, 3) at the circumferential position θ _i (i = 1, 2, 3) of the outer peripheral surface of the encoder 1a. Calculation is based on the pulse period ratio s / L (see FIG. 11) of the output signal of the sensor 10 existing at the same circumferential position θ _i (i = 1, 2, 3). The calculation principle of each displacement y _i (i = 1, 2, 3) at this time is the same as the calculation principle of the axial displacement in the conventional structure shown in FIGS. Then, the displacement y and the inclinations φ _x and φ _z are calculated by substituting the displacement y _i (i = 1, 2, 3) calculated in this way into the right side of the equation (4).
Further, the arithmetic unit calculates the mutual phase difference ratio “ε (120) − between the output signals of the two sensors 10 and 10 disposed at the position of θ ₁ = 0 degree and the position of θ ₂ = 120 degrees. ε (0) ”and the mutual phase difference ratio“ ε (240) − between the output signals of the two sensors 10 and 10 arranged at the position of θ ₁ = 0 ° and the position of θ ₃ = 240 °. ε (0) ”is calculated by calculating the ratio m / L of FIG. Then, the mutual phase difference ratios “ε (120) −ε (0)” and “ε (240) −ε (0)” calculated in this way and the inclinations φ _x and φ calculated by the above equation (4). _The displacements x and z are calculated by substituting z into the right side of the equation (12).

Further, the five-direction displacements x, y, z and inclinations φ _x , φ _z calculated as described above, and the corresponding five-direction loads and moments acting on the main shaft 4 (the load Fx in the x-axis direction) , The load Fy in the y-axis direction, the load Fz in the z-axis direction, the moment Mx around the x-axis, and the moment Mz around the z-axis) are determined by the rigidity of the multi-row rolling bearing unit 6 and the like. A relationship is established. And this predetermined relationship is calculated | required not only by calculation based on the elastic contact theory etc. widely known in the field of a rolling bearing, but also by experiment. Therefore, if software in which an arithmetic expression representing the predetermined relationship is installed is installed in the computing unit, the computing unit calculates the displacement x, y, z and inclinations φ _x , φ _z in the five directions. Based on these, the loads Fx, Fy, Fz and moments Mx, Mz in the five directions are obtained. The method for obtaining the loads Fx, Fy, Fz and the moments Mx, Mz in the five directions in this way is described in detail in, for example, Patent Documents 3 and 4, and further detailed description thereof is omitted. .

According to the physical quantity measuring apparatus for a rotary machine of this example configured as described above, the displacements x, y, z and the inclination in five directions of the encoder 1a (the portion of the main shaft 4 that supports and fixes the encoder 1a). phi _x, and phi _z, 5 direction of the load Fx which acts on the spindle 4, Fy, Fz and moments Mx, asked to Mz. In particular, in the case of this example, the number of sensors 10, 10 used in combination with the encoder 1a can be reduced to three. For this reason, the expense of each of these sensors 10 and 10 can be suppressed. Furthermore, it becomes relatively easy to make the detection parts of all the sensors 10 and 10 face a predetermined portion of the detection surface of the encoder 1a with high accuracy, and the productivity can be improved accordingly.

[Second Example of Embodiment]
FIGS. 8-9 has shown the 2nd example of embodiment of this invention corresponding to Claims 1-4. In the case of this example, the configuration of the plurality of characteristic change combination units 3b and 3b provided on the outer peripheral surface of the encoder 1b, which is the detected surface, is slightly different from that of the above-described first example. That is, in the case of this example, only the second concave grooves 11d and 11d among the first and second concave grooves 11c and 11d constituting the characteristic change combination portions 3b and 3b are used as the shaft of the encoder 1b. The first concave grooves 11c and 11c are formed in the axial direction of the encoder 1b. That is, the inclination angle of each of the first concave grooves 11c and 11c with respect to the axial direction of the encoder 1b is set to zero.

又、この（５′）式中のδが零（δ＝０）である事を考慮すると、この（５′）式に基づいて、前記（６）〜（８）式に対応する、次の（６′）〜（８′）式が得られる。

又、これら（６′）〜（８′）式に基づいて、前記前記（９）式及び（１０）式に対応する、次の（９′）式及び（１０′）式が得られる。

又、これら（９′）式及び（１０′）式に基づいて、前記（１１）式に対応する、次の（１１′）式が得られる。

更に、この（１１′）式に基づいて、前記（１２）式に対応する、次の（１２′）式が得られる。

本例の場合、前記演算器は、前記（１２）式の代わりに、この（１２′）式を利用して、前記各変位ｘ、ｚを算出する。 And in this embodiment, calculator, not shown, in the first example of a case similar to the procedure described above, i.e., the displacement y _i (i based on the pulse period ratio of the output signals of the three sensors 10, 10 = 1, 2, 3), the displacement y and the inclinations φ _x and φ _z are calculated using the equation (4). At the same time, displacement x and z are calculated using pulses generated based on the first concave grooves 11c and 11c included in the output signals of the sensors 10 and 10, respectively. Here, in the case of this example, the inclination angle α of each of the first concave grooves 11c and 11c with respect to the axial direction of the encoder 1b is zero (α = 0). Therefore, the above equation (5) can be expressed by the following equation (5 ′) by substituting α = 0 into α in the equation.

Further, considering that δ in the equation (5 ′) is zero (δ = 0), the following corresponding to the equations (6) to (8) based on the equation (5 ′) Equations (6 ′) to (8 ′) are obtained.

Further, based on these equations (6 ′) to (8 ′), the following equations (9 ′) and (10 ′) corresponding to the equations (9) and (10) are obtained.

Further, the following equation (11 ′) corresponding to the equation (11) is obtained based on these equations (9 ′) and (10 ′).

Further, based on the equation (11 ′), the following equation (12 ′) corresponding to the equation (12) is obtained.

In the case of this example, the computing unit calculates the displacements x and z using the equation (12 ′) instead of the equation (12).

  In the case of such a physical quantity measuring device for a rotary machine of this example, the second term on the right side of the equation (12) is omitted in the equation (12 ′) used when calculating the displacements x and z. It is a formula. For this reason, in the case of this example, compared with the case of the 1st example mentioned above, the amount of calculation at the time of the said calculator calculating each said displacement x and z can be decreased. Therefore, it is possible to improve the calculation speed of these displacements x and z and reduce the cost by reducing the specifications of the calculator. Other configurations and operations are the same as those of the first example described above.

  In each of the above-described embodiments, the shift amount δ in the equations (1) and (5) {(5 ')} is zero (δ = 0). If this deviation amount δ cannot be made zero (or sufficiently small), the equations corresponding to the above equations (1) to (4) can be calculated with the deviation amount δ included. In addition, an equation corresponding to the equation (12) {the equation (5 ′) to the equation (12 ′)} may be derived from the equation (5).

Moreover, when implementing this invention, the 1st, 2nd characteristic change part provided in the to-be-detected surface of the encoder made from a magnetic material can also be made into a through-hole and a convex part, for example instead of a concave groove. The encoder can also be made of a permanent magnet (of the detected surface, the first and second characteristic changing portions and the other portions having different polarities). In this case, it is not necessary to provide a permanent magnet on each sensor side.
Further, the present invention is not limited to a structure that measures a physical quantity related to a spindle of a machine tool, but can be applied to a structure that measures a physical quantity related to a rotating bearing ring member that constitutes a rolling bearing unit for supporting a wheel of an automobile, for example. .

DESCRIPTION OF SYMBOLS 1, 1a Encoder 2a, 2b Through-hole 3, 3a, 3b Characteristic change combination part 4 Main shaft 5 Housing 6 Multi-row rolling bearing unit 7 Electric motor 8a-8d Rolling bearing 9 Sensor unit 10 Sensor 11a, 11b, 11c, 11d Groove 12 Holder

Claims (4)

A stationary machine that does not rotate, and a rotating machine that includes a rotating member that is rotatably supported with respect to the stationary member by a plurality of rolling bearings each preloaded, and is supported and fixed to a part of the rotating member. An encoder having a detected surface concentric with the rotating member, a sensor supported by the stationary member in a state where the detection unit faces the detected surface, and an arithmetic unit that processes an output signal of the sensor And
The detected surface of the encoder has a plurality of characteristic change combination parts arranged at equal pitches in the circumferential direction, and each of these characteristic change combination parts is arranged separately at a predetermined pitch in the circumferential direction. The first characteristic change part and the second characteristic change part are different from each other in inclination angles in consideration of positive and negative signs with respect to the width direction of the detected surface,
In the physical quantity measuring apparatus for a rotating machine, the sensor changes an output signal at a moment when each of the characteristic changing units passes through a portion of the detected surface that the detecting unit faces.
The sensor includes only three sensors, and the detection unit of each of the sensors is opposed to a portion of the detected surface that has different phases in the circumferential direction.
Based on information obtained from the output signals of the sensors, the computing unit calculates a part or all of the displacement in the three orthogonal directions and the inclination in the two orthogonal directions of the encoder relative to the stationary member. A physical quantity measuring apparatus for a rotating machine characterized by having a function of calculating.   As information obtained from the output signals of the sensors, which is used when the computing unit calculates part or all of the displacements in the three directions and the inclinations in the two directions, the pulses of the output signals of the sensors. The period ratio and the phase difference ratio between the pulses generated based on the first characteristic change part included in the output signals of the sensors, which are present between the output signals of the sensors, are employed. The physical quantity measuring device for a rotary machine according to claim 1.   The physical quantity measuring apparatus for a rotating machine according to any one of claims 1 to 2, wherein an inclination angle of the first characteristic change portion with respect to a width direction of the detected surface is zero.   The computing unit calculates an external force acting between the stationary member and the rotating member based on part or all of the displacement in the three orthogonal directions and the inclination in the two orthogonal directions. The physical quantity measuring device for a rotating member according to any one of claims 1 to 3, comprising:

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