JPH02250746A - Cooling method for ball screw - Google Patents

Abstract

PURPOSE:To improve an axial feeding accuracy and to prolong the life of the bearing of a ball screw, by controlling a throttle valve so as to flow the optimum amount of a coolant corresponding to a heating amount by the value that the heating state of the ball screw is found by a temperature sensor. CONSTITUTION:Two orthogonal ball screws 1 and 3 parallel to the face of the bed whose graphic display is omitted of a machine tool are provided and rotated with their NC driving by a servomotor not shown in a figure. Ball screw nuts 2, 4 screwed with the ball screws 1, 3 have temperature sensors 5, 6 and the ball screws 1, 3 have cooling holes penetrated in the axial direction. A coolant is returned to a tank 8 via a pipe 13, variable aperture 11, pipe 15 and pipe 14, variable aperture 12 and pipe 16 by a pump 10. A control device 17 controls the contractions of the variable apertures 11, 12 by the outputs of the temperature sensors 5, 6 to circulate the optimum, amount of the coolant. Thus, the thermal displacement of the ball screw is reduced, the axial feeding accuracy is improved, the fluctuation the loads of the ball screw support bearings are reduced and the life of the bearing is prolonged.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for cooling a ball screw used in a machine tool or the like.

BACKGROUND OF THE INVENTION Ball screws used in recent machine tools and the like generate more heat due to faster feed rates and heavier cutting, and are therefore required to be cooled. This cooling method generally cools the ball screw from the inside by constantly flowing a constant flow of temperature-controlled cooling oil through the cooling hole of the ball screw, excluding changes in viscosity due to temperature changes. .

Problems to be Solved by the Invention The method of circulating a constant flow of cooling oil through the cooling hole of a ball screw described in the prior art is based on the method of circulating cooling oil at a constant flow rate through the cooling hole of a ball screw fixed to a ball screw that has different heat generation conditions each time, such as the amount of heat generated and the cycle of heat generation. There is a problem in that only by circulating a constant flow of cooling oil, it is not possible to perform optimal cooling in response to changes in heat generation conditions.

The present invention has been made in view of the above-mentioned problems of the conventional technology, and its purpose is to provide a cooling method that effectively cools the ball screw in accordance with the heat generation status of the ball screw. It is.

Means for Solving the Problems In order to achieve the above object, the ball screw cooling method of the present invention detects the heat generation state of the ball screw with a temperature sensor, and uses the cough detected value to optimize the cooling fluid according to the amount of heat generated. The control device calculates the amount of throttle to obtain the flow rate, automatically adjusts the variable throttle, and constantly cools the ball with the optimally distributed cooling fluid.

The state of heat generated by the ball screw during operation is constantly detected by a temperature sensor, and the output of the temperature sensor is input to the control device, which calculates the amount of throttling that will provide the optimum flow rate according to the amount of heat generated. Then, the variable aperture is controlled by the output of the control device.
J to cool the ball screw with the cooling liquid at a flow rate that corresponds to the heat generation situation.

Embodiment An embodiment will be explained with reference to FIG. A ball screw l is rotatably provided parallel to a sliding guide surface in the X-axis direction cut on a bed (not shown) of a machine tool, and a ball screw nut 2 screwed onto the ball screw l is ,
It is fixed to a carriage (not shown) that is movably placed on the bed.

Then, the ball screw 1 is rotated by an NCII-driven servo motor (not shown), and the movement and positioning of the carriage is performed.

Furthermore, a ball screw 3 is rotatably provided parallel to the sliding guide surface in the X-axis direction cut on the carriage.
A ball screw nut 4 that is screwed onto the ball screw 3 is fixed to an intermediate base that is movably placed on the carriage. The ball screw 3 is rotated by an Nc%l-driven servo motor (not shown), and the intermediate platform is moved and positioned. The ball screws 1 and 3 are provided with cooling holes passing through them in the axial direction, and the ball screw nuts 2 and 4
Temperature sensors 5 and 6 are attached to heat generating locations.

On the other hand, a cooling oil storage tank 8 is installed outside the machine, and an oil controller 9 for adjusting the temperature of the cooling oil to a predetermined temperature is installed near the tank. The coolant pump IO is installed in or near the tank 9, and the discharge ports of the pump are communicated with the inlets of the cooling holes of the ball screws 1 and 3 through conduits 13 and 14, respectively, and Variable throttles 11 and 12 are provided in which the flow rate can be adjusted by external control signals. The outlet of the cooling hole of the ball screw is communicated with the tank 8 through pipes 15 and 16, forming a cooling oil circulation path. Furthermore, a control device 17 is provided, and the control device 17 calculates the respective optimum flow rates according to the calorific value of each ball screw l, 3 based on the output signal of the temperature sensor 5.6, and adjusts the variable throttle If, 12. It is designed to output a control signal to.

Next, the operation of this embodiment will be explained. Cooling oil whose temperature is controlled by the oil controller 9 is supplied to the cooling holes of the ball screws l and 3 during operation via the pipes L3 and I4 by the pump 10, and the ball screws are cooled while flowing through the cooling holes. and is returned to the tank via lines 15 and 16.

During operation, each ball screw 1.3 has different heat generation conditions due to changes in the frequency of rapid feed, cutting load, etc., and the temperature change of the pol screw 1 is controlled by the temperature sensor 5, and the temperature change of the ball screw 3 is controlled by the temperature sensor 6. The control device 17 calculates the optimum flow rate individually based on each input signal and outputs a control signal to the corresponding variable throttles 11 and 12. The flow rate of oil passing through the cooling hole of the ball screw l is adjusted by a variable throttle 11 provided midway through the pipe line 13, and the flow rate of oil passing through the cooling hole of the ball screw 3 is adjusted midway through the pipe line 14. Adjustment takes place by means of a variable diaphragm 12 provided. Therefore, the flow rate is distributed so that a large amount of cooling oil flows to the ball mesh that generates a large amount of heat, and a small amount of cooling oil flows to the ball mesh that generates a small amount of heat.

In addition, when the variable aperture 11.12 is stopped down to its maximum,
If you use a type that can reduce the flow rate to zero, you can also prevent cooling oil from flowing in a ball cage that does not generate heat.

Further, the temperature sensor is not limited to being attached to the ball screw nuts 2 and 4, and can be attached to any location where the state of heat generation of the ball screw can be detected, such as the ball screw support.

Effects of the Invention Since the present invention is configured as described above, it produces the following effects.

The heat generation state of the ball screw is detected by a temperature sensor, and the control device calculates the amount of throttling that will obtain the optimum flow rate from the value of the temperature sensor, controls the variable throttle, and flows the coolant at a flow rate that corresponds to the heat generation state. Since sufficient cooling is provided, it is possible to reduce thermal displacement of the ball screw and improve shaft feeding accuracy. Further, due to the reduction in thermal displacement, fluctuations in the load applied to the support bearing of the ball screw can be reduced, and the life of the support bearing can be extended.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the structure of the ball net cooling method.

Claims (1)

[Claims] (1) The temperature sensor (
5, 6), and based on the detected value, the control device (17) calculates the throttle amount that will provide the optimum flow rate of the coolant according to the calorific value, and automatically adjusts the variable throttle (11, 12). A method for cooling a ball screw, characterized in that the ball screw is cooled by a cooling liquid with an optimum flow rate distributed at all times.