JPH0985582A - Thermal displacement estimating device of machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately estimate the relative displacement between a tool cutting edge and a work by grasping the temperature distribution of the whole main spindle system. SOLUTION: The temperature of an outer race of a bearing 10 for supporting the tip of a main spindle 1 is measured by a first sensor 21. The temperature of the outer periphery of a stator 15b in a motor 15 is measured by a second sensor 22. A third sensor 23 is provided on a main spindle head 2 at the position separated from the first sensor 21 and the second sensor 22, and the temperature of the intermediate part to be heated by thermal transfer in rotating of the main spindle is measured. A fourth sensor 24 for measuring the reference temperature is provided on a bed not to be heated with the rotation of the main spindle. Outputs of respective sensors are input into an NC device 26 through an analog-to-digital converter 25, and the relative displacement between a tool 18 at the tip of the main spindle and a work is calculated by the calculating means on the basis of the measured temperatures of respective sensors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for estimating a relative displacement between a tool edge and a workpiece generated by heat generated when a spindle rotates in a machine tool.

[0002]

2. Description of the Related Art Conventionally, as a method for estimating the thermal displacement of a spindle, a temperature near a bearing, which is a heat source, and a reference temperature of a portion (for example, a bed) that does not generate heat when the spindle rotates are measured by sensors, and the measured temperature is measured. A technique for estimating the relative displacement between the spindle end and the workpiece based on the difference between the two has been proposed.

[0003]

However, according to the conventional estimation method, since the heat source is limited to the bearing, it is not possible to accurately grasp the temperature condition of the entire main spindle system, and the estimated value of the thermal displacement is obtained. There was a problem that an error occurred with the actual value. This is because the heat generation factor of the spindle includes not only the bearing loss but also the spindle drive motor loss. Moreover,
The heat generation amount of the bearing basically increases as the main shaft rotation speed increases, whereas the heat generation amount of the motor changes depending on the motor efficiency and the load condition. In other words, since there is no relationship between the temperature rise characteristics of the bearing and the temperature rise characteristics of the motor, the temperature distribution of the entire main spindle system cannot be uniquely specified only by the temperature in the vicinity of the bearing. It causes an error. Even if the temperature of the motor is measured and the thermal displacement is estimated based on the difference between the motor temperature, the bearing temperature, and the reference temperature, the heat source of the temperature change cannot be identified, so the temperature distribution of the entire main spindle system is understood. Is difficult.

Therefore, an object of the present invention is to provide a thermal displacement estimating device for a machine tool which can grasp the temperature distribution of the entire spindle system and accurately estimate the relative displacement between the spindle end and the workpiece.

[0005]

In order to solve the above-mentioned problems, the thermal displacement estimation device of the present invention is
A device that estimates the relative displacement between the tool edge and the workpiece that is generated by heat generated when the spindle rotates, and measures the temperature near the bearing that supports the spindle and the temperature near the motor that drives the spindle. The second sensor, the third sensor that measures the temperature of the portion where the temperature changes at the time of the spindle at the positions distant from the first sensor and the second sensor, and the position that is distant from the first to third sensors does not generate heat when the spindle rotates. It is composed of a fourth sensor for measuring the temperature of the part and a means for calculating the relative displacement between the spindle end and the workpiece based on the temperatures measured by the first to fourth sensors.

Here, in the case of an NC machine tool, the calculation means is constituted by a part of the NC device, and a predetermined functional expression is stored in the program memory of the NC device, and the first to fourth sensors are stored in this functional expression. By substituting the measured temperature of 1 as a variable, the relative displacement between the tool edge and the workpiece can be obtained.
Further, by storing the relative displacement amount obtained in advance for each temperature using this functional expression in the program memory, it may be possible to reduce the calculation processing amount of the NC device during machine operation.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a machining center will be described below with reference to the drawings. As shown in FIG. 1, a spindle 1 of a horizontal machining center is rotatably supported by a spindle head 2. Spindle head 2 is saddle 3
It is supported by the column 4 via the and is positioned at an arbitrary position in the Y direction by a servo motor (not shown). The column 4 is installed on the bed 5 and is positioned at an arbitrary position in the Z direction by a servo motor (not shown). The work 6 is placed on the table 7, and the table 7 is positioned at an arbitrary position in the XY direction with respect to the bed 5 by a servo motor (not shown).

As shown in FIG. 2, three bearings 10, 11, 12 are arranged on the main shaft 1. Bearing 10, 11
Via a sleeve 13 and the bearing 12 via a sleeve 14 inside the spindle head 2. Spindle head 2
Has a built-in motor 15 for driving the spindle 1 to rotate. The motor 15 is composed of a rotor 15a on the spindle 1 side and a stator 15b on the spindle head 2 side. A cooling passage 16 is formed in the spindle head 2 and the sleeve 13, and the spindle 1 is cooled by a cooling liquid 17 flowing therethrough. A tool 18 for processing the work 6 is inserted into the tip of the main shaft 1 and held by a spring 19 via a draw shaft 20.

A first sensor 21 for measuring the outer ring temperature T1 of the bearing 10 is provided in the sleeve 13 near the bearing 10 supporting the tip of the main shaft 1. Motor 15
A second sensor 22 for measuring the outer peripheral temperature T2 of the stator 15b is provided on the spindle head 2 in the vicinity of. At a position apart from the first sensor 21 and the second sensor 22, the spindle head 2 mainly has the bearings 10 and 11 when the spindle 1 rotates.
Also, a third sensor 23 for measuring the temperature T3 of the intermediate portion that generates heat due to heat conduction from the motor 15 is provided. In addition, as shown in FIG. 1, the first to third sensors 2
A fourth sensor for measuring, as a reference temperature, a temperature T4 of a portion of the bed 5 located far away from the bearings 1, 22, 23 and 23, which does not generate heat due to heat conduction from the bearings 10, 11, 12 and the motor 15 when the spindle 1 rotates. 24 are provided. Then, the outputs of the respective sensors 21, 22, 23, 24 are converted into numerical information by the analog-digital converter 25, and then N
C is input to the device 26, and the processing described below is executed by the calculating means of the device 26 so that the relative displacement between the tool 18 at the tip of the spindle 1 and the workpiece 6 is calculated based on the temperature measured by each sensor 21-24. It has become.

That is, in the flow chart shown in FIG. 3, first, temperature information numerically converted based on the outputs of the respective sensors 21 to 24, that is, the bearing temperature T1, the motor temperature T2, the intermediate portion temperature T3, and the reference temperature T4. Is input to the NC device 26 (step S1). Then T1 and T
3 difference ΔT13 and T2 and T3 difference ΔT2
3 is calculated (step S2). Next, the temperature distribution correction coefficient Tk is calculated from the constants a and b obtained in advance by experiments and the differences ΔT13 and ΔT23, and T3 is calculated.
And the difference ΔT34 between T4 and T4 is calculated (step S
3). Then, ΔT34 and Tk are added to calculate the effective temperature increase amount ΔT (step S4). Further, ΔT is multiplied by a constant c previously obtained by experiments or the like to calculate the relative displacement amount Δl between the tool 18 and the workpiece 6 during the spindle rotation (step S5). Then, the relative displacement amount Δl is output to the correction unit of the NC device 26 (step S6), and then the relative displacement between the tool and the work is corrected according to a known correction method by the NC device 26.

The constants a, b, and c are preferably coefficients obtained from the relationship between the relative displacement and the temperature measured in advance. The approximate expression shown in the flowchart of FIG. 3 can be commonly applied to machines of the same design, but if the constants a, b, and c are adjusted according to the characteristics of each machine, the estimation accuracy is further improved. be able to. In the above embodiment,
The temperature distribution correction coefficient ΔTk was calculated using the linear form,
Depending on the temperature measurement position and the characteristics of the spindle cooling mechanism, it is of course possible to use a non-linear expression to approximately calculate.
In addition to the temperature measurement value, it is also effective to use the change history information of the temperature measurement value, the time average value, or the like as the variable.

[0012]

As described in detail above, according to the present invention,
The temperature distribution of the entire spindle system can be grasped based on the temperatures measured by the four sensors, and the relative displacement between the tool cutting edge and the workpiece can be accurately estimated, which is an excellent effect. In particular, by taking the difference between the bearing temperature and the motor temperature, which are the heat generating parts, and the temperature of the intermediate part affected by that, calculating the correction coefficient from this, and estimating the temperature distribution from this and the reference temperature, The relative displacement of the work can be estimated with higher accuracy.

[Brief description of drawings]

FIG. 1 is a schematic view of a machining center showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a spindle head showing a thermal displacement estimation device of the machining center.

FIG. 3 is a flowchart showing the contents of arithmetic processing of the estimation device.

[Explanation of symbols]

1 ... Spindle, 5 ... Bed, 10, 11, 12 ... Bearing, 15 ... Motor, 18 ... Tool, 21 ... First sensor, 22 ... Second sensor, 23 ... Third sensor, 24.
4th sensor, 26 ... NC device.

Claims (1)

[Claims] 1. A machine tool, comprising: a device for estimating relative displacement between a tool cutting edge and a workpiece, which is generated by heat generated when a spindle rotates, a first sensor for measuring a temperature near a bearing supporting the spindle, and the spindle. Second sensor for measuring the temperature in the vicinity of the motor for driving the motor, a third sensor for measuring the temperature of a portion distant from the first and second sensors when the spindle rotates, and first to third sensors Machine tool comprising a fourth sensor for measuring the temperature of a portion which does not generate heat when the spindle rotates at a position distant from and a means for calculating the relative displacement between the spindle end and the workpiece based on the temperature measured by the first to fourth sensors. Thermal displacement estimation device.