JPH08135751A - Cooling device for ball screw - Google Patents

Abstract

PURPOSE: To suppress heating of a ball screw properly by controlling the feed amount of refrigerant based on the rotating amount of the ball screw and also cool the heating part of the ball screw directly and efficiently by spouting the refrigerant at a contact part between the nut and screw shaft of the ball screw. CONSTITUTION: A mixer 15 to generate the mixed refrigerant of compressed air and lubricating oil is provided in a refrigerant feeding circuit 8. Also a refrigerant path 20 to flow the mixed refrigerant is provided in a nut 2 and a mobile body 4, and the mixed refrigerant is spouted from the inside of the nut 2 to a contact part between the nut 2 and a screw shaft 3. Then, based on a rotating amount reference value for each unit time of the ball screw 1, an opening and closing selector valve 13 is controlled and, based on the rotating amount for each unit time, the opening degree of a flow control valve 14 is controlled by a NC controller 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for cooling a ball screw used in NC machine tools and the like.

[0002]

2. Description of the Related Art Generally, in an NC machine tool, the rotation of a servomotor is converted into a linear motion by a ball screw to drive a moving body such as a table. In order to suppress the heat generation of the ball screw, the screw shaft is usually supported by rolling bearings, but in recent years when high-speed driving of the moving body and high-precision positioning are required, the thermal expansion of the screw shaft is more strictly suppressed. Forced cooling for is needed. Therefore, in the related art, for example, in Japanese Patent Laid-Open No. 2-250746, a temperature sensor provided in the nut detects the heat generation state of the ball screw, and the coolant supply circuit is controlled based on the detected value to respond to the temperature of the nut. A technique has been proposed in which a cooling liquid having a flow rate is caused to flow from one end of a hollow screw shaft to the inside to forcibly cool a ball screw.

[0003]

However, according to the conventional cooling device, the heat generation state of the ball screw is estimated from the temperature of the nut. Therefore, if the ball screw is rotating and the temperature is in a steady state, it can be estimated relatively accurately. However, when the ball screw is stopped, there is a difference in temperature change between the nut and the screw shaft, so the estimated value becomes inaccurate, which may lead to overcooling of the screw shaft. Moreover, when focusing on the transient state of heat generation, since the thermal time constants of the nut and the screw shaft are different from each other, it is difficult to control the temperature accurately only by the temperature of the nut. Further, since the conventional cooling device is configured to flow the cooling liquid inside the screw shaft, it is not possible to directly cool the contact portion between the nut that is the heat generating portion of the ball screw and the screw shaft, In particular, there is a problem that the cooling efficiency is lowered in a processing state in which this portion is far away from the cooling liquid introduction end of the screw shaft.

Therefore, an object of the present invention is to provide a device capable of cooling a ball screw accurately and efficiently.

[0005]

In order to solve the above-mentioned problems, a cooling device of the present invention comprises a refrigerant supply means, a nozzle means for ejecting a refrigerant to a contact portion between a nut of a ball screw and a screw shaft, and a ball screw. Control means for controlling the refrigerant supply means based on the rotation amount per unit time.

In the above cooling device, preferably, the refrigerant supply means includes an open / close switching valve, and the control means is configured to control the open / close switching valve based on a rotation amount reference value of the ball screw per unit time.

Further, a flow rate adjusting valve is provided in the refrigerant supply means,
The control means may be configured to control the flow rate adjusting valve according to the amount of rotation of the ball screw per unit time.

Further, it is preferable that the refrigerant supply means comprises a mixer for producing a mixed refrigerant of compressed air and lubricating oil, and the nozzle means comprises a refrigerant passage through which the mixed refrigerant flows in a nut.

[0009]

Since the heat generation of the ball screw is generated at the time of rotation of the screw shaft and at a rate according to the rotation amount, the cooling device of the present invention controls the refrigerant supply means based on the rotation amount per unit time. Thus, heat generation of the ball screw can be properly suppressed. Further, since the nozzle means of the present invention ejects the refrigerant to the contact portion between the nut of the ball screw and the screw shaft, it is possible to directly and efficiently cool the heat generating portion of the ball screw regardless of the relative position of the nut and the screw shaft. it can.

When the opening / closing switching valve is provided in the refrigerant supply means, when the rotation amount of the ball screw exceeds the reference value, the switching valve is opened to start supplying the refrigerant, and conversely, the rotation amount is the reference value. If the following occurs, the switching valve is closed and the supply of refrigerant is stopped. By doing this, cooling can be performed only when the heat generation condition reaches a level that poses a problem in terms of accuracy, and cooling is not performed if heat generation is negligible, avoiding overcooling when the ball screw is stopped or at very low speed rotation. be able to.

Further, when the refrigerant supply means is provided with a flow rate adjusting valve, the adjusting valve is controlled according to the amount of rotation of the ball screw per unit time so that the cooling capacity is adjusted to the actual heat generation state of the ball screw. Can be adjusted by
Rather than the total displacement of the screw shaft, the amount of change in displacement over time can be suppressed and stable feed accuracy can be obtained.

Further, when the nut is provided with a refrigerant passage through which a mixed refrigerant of compressed air and lubricating oil flows, the refrigerant passage can be shared as a cooling pipe and a lubricating pipe, so that the structure of the nozzle means is simplified. There are advantages. Further, since the refrigerant is composed of compressed air and lubricating oil, the pressure of the compressed air can be set to a relatively low level, which is also effective as a noise countermeasure.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the ball screw 1 includes a nut 2 and a screw shaft 3, the nut 2 is connected to a moving body 4 such as a table in a machine tool, and the screw shaft 3 is connected to a servomotor 5. And the servo motor 5
Is converted into a linear movement of the nut 2 via the screw shaft 3 so that the movable body 4 can be positioned at any position within the effective length range of the screw shaft 3.

A cooling device 7 for the ball screw 1 comprises a refrigerant supply circuit 8, a nozzle 9 and an NC control device 10. The refrigerant supply circuit 8 supplies the compressed air from the air source 12 to the mixer 15 via the open / close switching valve 13 and the flow rate adjusting valve 14 in the compressed air pipeline 11, and the lubricating oil is pumped into the mixer 15 in the lubricating oil pipeline 16 by the pump 17. The mixer 15 is configured to supply a constant amount and a constant interval to the mixer 15 through the formula distributor 18, and the mixer 15 mixes the compressed air and the lubricating oil to generate a mixed refrigerant.

The nozzle 9 is a refrigerant passage 2 through which the mixed refrigerant flows.
0 is provided in the nut 2 and the moving body 4, and the mixed refrigerant is jetted from the inside of the nut 2 to the contact portion between the nut 2 and the screw shaft 3. The NC control device 10 is a control unit that controls the refrigerant supply circuit 8 based on the rotation amount of the ball screw 1 per unit time, and controls the open / close switching valve 13 based on the rotation amount reference value per unit time. The opening degree of the flow rate adjusting valve 14 is controlled according to the rotation amount per unit time.

Next, the cooling device 7 configured as described above.
The operation will be described with reference to the flowchart of FIG. When positioning the moving body 4, when the ball screw 1 is rotated by the servo motor 5 (step S1), the NC control device 10 determines the ball screw 1 based on the rotation signal of the servo motor 5.
The rotation amount per unit time is calculated (step S2), and this rotation amount is compared with a previously stored reference value (step S3).

When the rotation amount of the ball screw 1 exceeds the reference value, the open / close switching valve 13 is opened in the refrigerant supply circuit 8 (step S4), and the compressed air is supplied to the mixer 15 through the compressed air line 11. The mixer 15 mixes with the lubricating oil from the lubricating oil line 16. Then, the mixed refrigerant is the refrigerant passage 1
It is jetted from the inside of the nut 2 to the contact portion between the nut 2 and the screw shaft 3 via 2, and the contact portion is lubricated with lubricating oil and at the same time cooled by compressed air. Therefore, the heat generating portion of the ball screw 1 can be directly and efficiently cooled regardless of the relative positions of the nut 2 and the screw shaft 3. In addition, the refrigerant passage 12 can be shared as a cooling pipe and a lubricating pipe, the nozzle 9 can be easily configured, and the pressure of compressed air can be set relatively low by using a mixed refrigerant of compressed air and lubricating oil. It is also possible to suppress noise.

During the cooling period, the NC control device 10 controls the opening degree of the flow rate adjusting valve 14 according to the rotation amount of the ball screw 1 per unit time (step S5). That is, when the ball screw 1 is rotated at a high speed and a large amount of heat is generated,
The flow control valve 14 has a large opening, and conversely, the ball screw 1
Is rotated at a low speed and the amount of generated heat is small, the opening of the flow rate adjusting valve 14 is controlled to be small. Therefore, the supply amount of compressed air, that is, the cooling capacity can be accurately adjusted according to the actual heat generation state of the ball screw 1. In addition, since the cooling capacity is controlled for each unit time, it is possible to suppress the change amount of the displacement amount over time, rather than the total displacement amount of the screw shaft 3,
Stable feed accuracy can be obtained.

On the other hand, when the rotation amount of the ball screw 1 per unit time becomes equal to or less than the reference value, the switching valve 13 is closed (step S6) and the supply of compressed air is stopped. Therefore, if the heat generation state of the ball screw 1 is negligible in terms of accuracy, the ball screw 1 is not cooled, and by doing so, it is possible to avoid overcooling when the ball screw 1 is stopped or rotates at a very low speed.
After the switching valve 13 is closed, it is determined whether the servomotor 5 is rotated or stopped (step S7), the cooling program is continued during rotation, and the program is ended by stopping.

[0020]

As described in detail above, according to the first aspect of the invention, the coolant is supplied to the nut of the ball screw and the screw shaft by controlling the coolant supply means based on the rotation amount of the ball screw per unit time. Since it is configured to jet to the portion, it has an excellent effect that the ball screw can be cooled accurately and efficiently.

According to the second aspect of the present invention, the refrigerant supply means is provided with the open / close switching valve, and this is configured to be controlled based on the rotation amount reference value of the ball screw per unit time.
There is an effect that cooling can be performed only when the heat generation state reaches a level that poses a problem in terms of accuracy, and cooling is not performed when heat generation is negligible, and supercooling when the ball screw is stopped or at a slow speed rotation can be avoided.

According to the third aspect of the present invention, the refrigerant supply means is provided with the flow rate adjusting valve, and the flow rate adjusting valve is controlled in accordance with the rotation amount of the ball screw per unit time. There is an effect that it can be adjusted according to the heat generation state, and that the amount of change in the amount of displacement of the ball screw over time can be suppressed and stable feeding accuracy can be obtained.

According to the fourth aspect of the present invention, the compressed air and the lubricating oil are mixed in the mixer, and the mixed refrigerant is made to flow through the refrigerant passage provided in the nut. There is an effect that it can be shared as a lubricating pipe, the structure of the nozzle means can be simplified, and in addition, the pressure of the compressed air can be set relatively low to suppress noise.

[Brief description of drawings]

FIG. 1 is a schematic view of a cooling device showing an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the device.

[Explanation of symbols]

1 ... Ball screw, 2 ... Nut, 3 ... Screw shaft, 4 ...
・ Movable body, 5 ・ ・ Servo motor, 7 ・ ・ Cooling device, 8 ・
・ Refrigerant supply circuit, 9 ・ ・ Nozzle, 10 ・ ・ NC control device, 13 ・ ・ Open / close switching valve, 14 ・ ・ Flow control valve, 15 ・
・ Mixer, 20 ・ ・ Refrigerant passage.

Claims (4)

[Claims] 1. A refrigerant supply means, a nozzle means for ejecting a refrigerant to a contact portion between a nut of a ball screw and a screw shaft, and a control means for controlling the refrigerant supply means based on a rotation amount of the ball screw per unit time. Ball screw cooling device. 2. The refrigerant supply means includes an open / close switching valve,
The ball screw cooling device according to claim 1, wherein the control means is configured to control the on-off switching valve based on a rotation amount reference value of the ball screw per unit time. 3. The refrigerant supply means includes a flow rate adjusting valve,
2. The ball screw cooling device according to claim 1, wherein the control means is configured to control the flow rate adjusting valve according to the rotation amount of the ball screw per unit time. 4. The ball screw cooling according to claim 1, wherein the refrigerant supply means includes a mixer for generating a mixed refrigerant of compressed air and lubricating oil, and the nozzle means includes a refrigerant passage through which a mixed refrigerant flows in a nut. apparatus.