JP2000205972A - Apparatus for measuring temperature of rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure the temperature of a certain portion of a rotor by means of a simple, small, rigid, and inexpensive arrangement. SOLUTION: A primary coil 11 is disposed in the fixed part 1 of a machine tool or the like and a secondary coil 12 is disposed on the rotor 2 of a spindle or the like, the coils 11,12 constituting a rotary transformer 13. The primary coil 11 is connected to an AC power supply 9 and an ammeter 16, and a resistor 15 such as a thermistor is disposed in the vicinity of the bearing 3 of the rotor 2, with the secondary coil 12 connected to the resistor 15 via a conductor 14. Since the temperature of the resistor 15 is approximately proportional to a temperature resistance value, the temperature of the portion of the rotor 2 near the bearing is calculated by detecting using the ammeter 16 a current flowing through the primary coil 11, and converting the output of the ammeter 16 into a temperature using a temperature calculation means 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the temperature of various rotating bodies such as a main shaft of a machine tool and a rotor of an electric motor.

[0002]

2. Description of the Related Art Conventionally, as a non-contact type temperature measuring device,
There is known a method in which the temperature of a rotating body is measured by a resistor such as a thermistor, the change in current is converted into an FM signal by a transmitter, transmitted, and received by an external antenna (telemeter method). There is also known an apparatus that regards a rotating body made of a conductive material as a combination of a coil and a resistor, and detects a resistance change of the rotating body due to a temperature change based on a current change of a coil on a fixed portion side.

[0003]

However, according to the former conventional apparatus, since the transmitter and the power supply circuit are built in the rotating body, the structure is complicated and expensive, a large installation space is required, and severe conditions such as machine tools are required. Under the environment, there was a problem that durability was uneasy. Further, in the case of the latter conventional device, it is difficult to measure the temperature at an arbitrary part of the rotating body because the resistance change of the entire rotating body is detected.

An object of the present invention is to provide an apparatus capable of accurately measuring the temperature of an arbitrary portion of a rotating body with a simple, compact, robust and inexpensive configuration.

[0005]

According to a first aspect of the present invention, there is provided an apparatus for measuring a temperature of a rotating body rotatably supported by a fixed part, the apparatus comprising: A rotary transformer having a primary coil disposed therein and a secondary coil disposed on a rotating body; a power supply connected to the primary coil; current detecting means for detecting a current flowing through the primary coil; A resistor having a specific temperature characteristic connected to the coil and arranged on the rotating body near the measured part; and a temperature calculating means for calculating the temperature of the rotating body based on the output of the current detecting means. And

FIG. 1 shows the principle configuration of the temperature measuring device. A rotating body 2 is rotatably supported by a fixed portion 1 via a bearing 3. Primary coil 1
1 is arranged, and a secondary coil 12 is arranged on the rotating body 2. The primary coil 11 is provided so as to surround the secondary coil 12 through a narrow gap.
The rotary transformer 13 is constituted by 12. A power supply 9 is connected to the primary coil 11, and a resistor 15 such as a thermistor is connected to the secondary coil 12 via a conducting wire 14. The resistor 15 is arranged in the vicinity of a measured portion of the rotating body 2, for example, near the bearing 3. The power supply 9 has a constant voltage
A constant frequency AC power supply can be used. In this case, since the temperature of the resistor 15 and the temperature resistance are in a substantially proportional relationship,
The current flowing through the primary coil 11 is detected by a current detecting means such as an ammeter 16 and the output is converted into a temperature by a temperature calculating means 17 to obtain the temperature of the measured portion of the rotating body 2, that is, the temperature near the bearing 3. Calculate the temperature.

Here, the temperature calculating means 17 grasps in advance the relationship between the temperature of the part to be measured and the indicated value of the ammeter 16 by a method such as measurement or theoretical analysis or automatic adjustment, and calculates a formula or an algorithm map. And the like, and the temperature of the measured part is calculated from the current value based on the relationship. For example, the current flowing through the primary coil 11 may be kept constant, and the voltage change accompanying the temperature change may be measured. Even when a plurality of electric quantities such as current or voltage change every moment, if they are known or detectable, temperature measurement can be performed by the device of the present invention. The amount of electricity to be detected is not limited to one of the current, voltage, or power supply frequency, and may be plural. In addition to the electric quantity, for example, the rotation speed of the rotating body may be detected. The means for implementing the temperature calculating means, the current detecting means, and the power supply are not particularly limited, and dedicated hardware may be used. In the case of a machine tool or the like, a function provided in the numerical controller may be used.

As the primary coil 11 and the secondary coil 12, for example, those having an annular structure shown in FIG. 8 can be used.
The primary coil 11 has a primary winding 18 wound around a concave portion having an open inner peripheral side, and the secondary coil 12 has a secondary winding 19 wound around a concave portion having an open outer peripheral side. A magnetic circuit is formed on the rotary transformer 13. A centrifugal force acts on the secondary winding 19 with the rotation of the rotating body 2, but the projection of the secondary winding 19 can be prevented by providing the projection 12 a in the opening of the secondary coil 12.
Further, the secondary winding 19 may be molded with resin. Note that the structures of the primary coil 11 and the secondary coil 12 are not limited to the illustrated example, and there are no individual differences, and they take into account requirements such as withstanding a centrifugal force during rotation and hardly changing electrical characteristics depending on the rotation speed. Can be changed arbitrarily.

FIGS. 2 and 3 show the operation of the temperature measuring apparatus constructed as described above. When the power supply voltage V1 is applied to the primary coil 11, an induced current I2 flows through the secondary coil 12 due to the magnetic flux generated by the primary coil 11. In this state, when the temperature t of the rotating body 2 changes, the electric resistance Rs of the resistor 15 changes, and the current I2 flowing through the secondary coil 12 also changes. When the voltage V1 and the frequency of the AC power supply 9 are kept constant, the current I1 flowing through the primary coil 11 changes while maintaining a constant relationship with the current I2 of the secondary coil 12. Therefore, if the relationship between the temperature t of the rotating body 2 and the current I1 of the primary coil 11 is grasped in advance by a method such as measurement, the current I1 of the primary coil 11 is detected by the ammeter 16 so that The temperature t of the rotating body 2 can be calculated by the temperature calculating means 17.

Hereinafter, a method of calculating the temperature t will be described with reference to an ideal and simple model (see FIG. 2) in which the loss of the rotary transformer 3 can be ignored. Number of windings of primary coil 11: N1 Number of windings of secondary coil 12: N2 Electromotive force of primary coil 11: E1 Electromotive force of secondary coil 12: E2 Current of primary coil 11: I1 Secondary coil 12 If the current is I2, then the relationship of E1 · N2 = E2 · N1 1 formula I1 · N1 = I2 · N2 2 formula is established.

Further, the circuit in the illustrated example has the following equation: V1 = E1 3 Equation RsｓI2 = E2 4 Equation 1 Equation 2 E2 = E1 ・ N2 / N1 5 Equation 2 According to Equation 2, I2 = I1 ・ N1 / N2 6 From Equations 5, 6, and 3, Equation 4 becomes I1 = V1 · (N2 / N1) ² / Rs 7 Equation.

Here, assuming that the temperature characteristic of the resistor 15 is Rs = Rs ₀ (1 + αt) 8 Equation Rs ₀ : Initial Value of Resistance α: Temperature Coefficient of Resistance From Equations 7 and 8, (1 + αt) Rs ₀ = V1 / I1 · (N2 / N1) ² 9 Equation 9 Therefore, if Equation 9 is modified with respect to t, t = {V1 / I1 / Rs ₀ / (N2 / N1 ₎ ² −1} / α Equation 10 Becomes Among, V1, Rs _0, N2, N1, since the value of α is known, it is possible to calculate the temperature t of the rotary member 2 by detecting the current I1 of the primary coil 11.

However, in practice, the primary coil 11
The winding 18 of the secondary coil 12 and the winding 19 of the secondary coil 12 also have internal resistances R1 and R2 (see FIG. 3), and their values change with temperature. R1, R2 are small compared to the Rs _0, R1, R2 The measurement accuracy measurement error is required by, if sufficiently small may be considered, ignoring the presence of the R1, R2. To improve the measurement error, R1,
When R2 is taken into consideration, for example, if it is calculated in the same way as the model in FIG. 2, I1 = {(N1 / N2) ² R1− (R2 + R)} ⁻¹ (N
2 / N1) ² V1 11 Now, the temperature characteristics of R1 and R2 are expressed as follows: R1 = R1 ₀ (1 + α ₁ t) Equation 12 R1 ₀ : Reference value of resistance α ₁ : Temperature coefficient R2 = R2 ₀ (1 + α ₂ t) Equation 13 R2 ₀ : Reference value of resistance When α _{2 is the} temperature coefficient, from the formulas 11, 12 and 13, I1 = [(N1 / N2) ² R1 ₀ (1 + α ₁ t) − {R 2 ₀ (1 + α ₂ t) + R ₀ (1 + αt)}] ^-1 (N2 / N1) ² V1 14

Here, if R1 ₀ , α ₁ , R2 ₀ , and α ₂ are grasped in advance by experiments or analysis in consideration of the temperature difference between the measured part and the rotary transformer, the windings 18 and 19 can be obtained. It is possible to correct the measurement error of the temperature t due to the resistance change.
For example, Equation 14 gives I1 = [{(N1 / N2) ² R1 ₀ −R2 ₀ −Rs ₀ } + ｛(N1 / N2) ² α ₁ −R2 ₀ α ₂ −Rs ₀ α｝ t] ⁻¹ (N2 / N1) ² V1 15 formula, and further, t = [(N2 / N1) ² V1 / I1-{(N1 / N2) ² R1 ₀ -R2 ₀ -Rs ₀ }] x {(N1 / N2) 2α _{1 -R2 0 α 2 -Rs 0 α} } -1 because 16 is a _{formula, R1 0, α 1, R2} 0, if the alpha ₂ is known,
Similarly, if the current I1 of the primary coil 11 is detected, the temperature t of the rotating body 2 can be calculated.

On the other hand, the invention according to claim 2 is an apparatus for measuring the temperature of a rotating body rotatably supported by a fixed part, wherein the primary coil is arranged on the fixed part side and the primary coil is arranged on the rotating body side. A first rotary transformer having a secondary coil, a second rotary transformer having a primary coil disposed on the fixed portion side and a secondary coil disposed on the rotary body side, and first and second rotation transformers. A power supply connected to the primary coil of the transformer;
First to detect the current flowing through the primary coil of the rotary transformer
A current detecting means, a second current detecting means for detecting a current flowing through a primary coil of the second rotary transformer, and a specification connected to the secondary coil of the first rotary transformer and arranged on a rotating body side near a measured part. A first resistor having a known temperature characteristic, connected to the secondary coil of the second rotary transformer, and disposed on the side of the rotating body near the part to be measured, and a first resistor having a known temperature characteristic; (2) temperature calculating means for correcting the temperature characteristic of the first rotary transformer based on the output of the current detecting means and calculating the temperature of the rotating body.

That is, as shown in FIG. 4, the temperature measuring apparatus has a reference second rotary transformer 23 in addition to the first rotary transformer 13 for measurement. The first rotary transformer 13 is configured in the same manner as the apparatus of FIG. 1 (the same reference numerals are given in the drawings). A second rotary transformer 23 is provided at a position adjacent to the first rotary transformer 13. The second rotary transformer 23 includes a primary coil 21 disposed on the fixed unit 1 and a secondary coil 22 disposed on the rotating body 2. The secondary coil 22 is the conductor 2
4 is connected to a reference second resistor 25 such as a thermistor. The second resistor 25 has a known temperature characteristic, and is arranged near the bearing 3 and adjacent to the first resistor 15.

In FIG. 5, for example, the second resistor 25 has a constant resistance value Rr at any temperature, for example, R
If s ₀ can be maintained, the current I21 flowing through the primary coil 21 of the second rotary transformer 23 is I21 = [＝ (N1 / N2) ² R1 ₀ -R2 ₀ -Rs ₀ ｝ + ｛(N1 / N2) ² α ₁ −R _{2 0} α ₂ Δt] ⁻¹ (N2 / N1) ² V1 17 When correcting the characteristics of the first rotary transformer 13 for measuring by the current I21 to the reference, first, we obtain the _{1 / I1-1 / I2 = R 0} αt (N1 / N2) 2 / V1 18 expression. Then, the 18 formula deformed for t, and t = (1 / I1-1 / I2 ) (N2 / N1) 2 V1 / αR 0 19 expression. Since the temperature coefficients α ₁ and α ₂ of the transformer do not appear in the equation (19), the temperature of the rotating body 2 can be accurately measured regardless of the temperature coefficient of the transformer.

Further, the resistance value of the second resistor 25 does not necessarily have to be Rs ₀ . For example, if the temperature characteristic of the second resistor 25 is represented by Rr = Rr ₀ (1 + αrt) 20 Equation, instead of Equation 19, t = ｛(1 / I1-1 / I2) (N2 / N1) ² V1 − (Rs ₀ −Rr ₀ )} / (Rs ₀ α−Rr ₀ αr) 21 Equation can be used. Also in this case, the temperature of the rotating body 2 can be accurately measured regardless of the temperature coefficient of the transformer. Therefore, this method is useful when the temperature characteristics of the transformer are unclear.

The method for calculating the temperature from the detected current value is not limited to the above method. In addition, two winding transformers can be integrally formed by winding two windings around one core.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Two embodiments of the present invention applied to a machine tool will be described below with reference to the drawings. FIG. 6 shows a machine tool provided with the temperature measuring device according to the first aspect of the present invention, and FIG. 7 shows a machine tool provided with the temperature measuring device according to the second aspect of the present invention. In each figure, FIG.
The same reference numerals as in FIG. 4 and FIG. 4 indicate the same or corresponding members.

In the machine tool shown in FIGS. 6 and 7,
A main shaft 2 as a rotating body is rotatably supported inside a housing 1 as a fixed portion via a plurality of angular bearings 3, and is driven by a built-in motor including a stator 31 and a rotor 32. A tool 33 is inserted into the lower end of the main shaft 2, and a pull stud 34 of the tool 33 is connected to a pull-up shaft 36 via a collet 35, and the pull-up shaft 36 is urged by a disc spring 37 in the tool pull-in direction.

The temperature measuring device for a machine tool shown in FIG. 6 measures the inner ring temperature of the bearing 3 on the tool 33 side, and has one rotary transformer 13 near the bearing 3. The rotary transformer 13 includes a primary coil 11 disposed on the housing 1 and a secondary coil 12 disposed on the main shaft 2.
The primary coil 11 comprises an AC power supply 9 and an ammeter 1
6, and the secondary coil 12 is connected to a resistor 15 via a conductor 14. The resistor 15 is made of a thermistor or the like having a specific temperature characteristic.
Is provided on the main shaft 2 in the vicinity of.

According to this temperature measuring device, the ammeter 16 detects the current flowing through the primary coil 11 and the temperature calculating means 17 calculates the inner ring temperature of the bearing 3 on the basis of the detected value. The temperature of the bearing part can be measured. The measured temperature is input to the numerical controller 38, and is used for, for example, detecting an abnormality in the bearing 3, correcting thermal displacement of the main shaft 2, or controlling a cooling device (not shown). Also, unlike the conventional method, there is no need to incorporate a transmitter or power supply circuit in the spindle 2, so the measuring device can be configured simply and inexpensively, the installation space is small, and the durability is sufficient even in the harsh environment of machine tools. It can demonstrate the nature. Note that the resistor 15
Is not limited to the vicinity of the bearing 3, but may be near the rotor 32 of the built-in motor, or may be implemented by attaching the resistor 15 to an arbitrary part to be measured. Similarly, the mounting location of the rotary transformer 3 is
The position is not limited to the part to be measured or the vicinity of the resistor 15, and may be a position that is easy to mount in terms of design and practical use. If necessary, a plurality of resistors 15,
It is also possible to provide the rotary transformer 3 and carry out.

In the case of the temperature measuring device shown in FIG.
The first rotary transformer 13 for measurement and the second
The rotary transformer 23 is provided in parallel. Each transformer 1
3, 23 primary coils 11, 21 and secondary coil 12,
It is preferable to use 22 having the same resistance, electric characteristics, temperature characteristics, and the like. It is desirable that the reference second resistor 25 has a constant resistance value irrespective of a temperature change, but a resistor having a known temperature characteristic may be used. In this case, it is preferable to dispose the second resistor 25 adjacent to the first resistor 15 for measurement because the correction can be more easily performed. According to this temperature measuring device, the temperature characteristic of the first rotary transformer 13 can be corrected using the current value flowing through the primary coil 21 of the second rotary transformer 23, and the inner ring temperature of the bearing 3 can be accurately measured.

The present invention is not limited to the main shaft of a machine tool, but may be implemented as a temperature measuring device for various rotating bodies, for example, for measuring the temperature of a rotor in a turbine, an electric motor, a disk brake or the like. it can.
In contrast to the above embodiment, in a machine in which the rotating body is provided outside the fixed portion, a primary coil is arranged inside and a secondary coil is arranged outside, so long as the spirit of the present invention is not deviated. It is also possible to arbitrarily change the shape and configuration of each part.

[0026]

As described above in detail, according to the temperature measuring device of the present invention, there is an excellent effect that the temperature of any part of the rotating body can be accurately measured by a simple, compact, robust and inexpensive configuration. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a basic configuration of a temperature measuring device according to the first embodiment of the present invention.

FIG. 2 is a circuit diagram showing an ideal model of a rotary transformer in the measuring device of FIG.

FIG. 3 is a circuit diagram showing an actual model of a rotary transformer in the measuring device of FIG.

FIG. 4 is a schematic diagram showing a principle configuration of a temperature measuring device according to the second aspect of the present invention.

5 is a circuit diagram of a rotary transformer in the measuring device of FIG.

FIG. 6 is an elevational view of a main part of a machine tool showing an embodiment of the temperature measuring device according to the first aspect of the present invention.

FIG. 7 is an elevational view of a main part of a machine tool, showing an embodiment of a temperature measuring device according to the invention of claim 2;

FIG. 8 is a perspective view illustrating the structure of a rotary transformer.

[Explanation of symbols]

1. Housing (fixed part), 2. Spindle (rotating body),
3 ··· Bearing, 9 ··· AC power source, 11, 21 ··· primary coil, 12, 22 ··· secondary coil, 13, 23 ··· rotary transformer, 14, 24 ··· conducting wire, 15, 25 ··· resistance vessel,
16, 26 ··· ammeter, 17 · · · temperature calculating means.

Claims (2)

[Claims] An apparatus for measuring a temperature of a rotating body rotatably supported by a fixed part, comprising: a primary coil disposed on the fixed part; and a secondary coil disposed on the rotating body.
A rotary transformer having a secondary coil; a power supply connected to the primary coil; current detecting means for detecting a current flowing through the primary coil; and a secondary coil connected to the rotating body near the part to be measured A temperature measuring device for a rotating body, comprising: a resistor having a specified specific temperature characteristic; and temperature calculating means for calculating a temperature of the rotating body based on an output of the current detecting means. 2. An apparatus for measuring the temperature of a rotating body rotatably supported by a fixed part, comprising: a primary coil disposed on the fixed part;
A first rotary transformer having a secondary coil, a primary coil disposed on a fixed part, and a secondary transformer disposed on a rotating body.
A second rotary transformer having a secondary coil; a power supply connected to the primary coils of the first and second rotary transformers; and a first current detecting means for detecting a current flowing through the primary coil of the first rotary transformer. A second current detecting means for detecting a current flowing through the primary coil of the second rotary transformer; and a specific temperature characteristic connected to the secondary coil of the first rotary transformer and arranged on the rotating body near the part to be measured. A second resistor having a known temperature characteristic and connected to a secondary coil of a second rotary transformer and disposed on a rotating body near a portion to be measured; and a first and a second current detecting means. A temperature calculating means for correcting a temperature characteristic of the first rotary transformer based on the output of the first rotary transformer and calculating a temperature of the rotary body.