JPH08276341A - Spindle feeding device of machine tool - Google Patents

Abstract

PURPOSE: To improve the positioning accuracy of a spindle by cancelling the elongation of a spindle and/or a spindle head by a thermal displacement, and the elongation of a feed screw. CONSTITUTION: The first shaft end bearing 16 to support the shaft and of a feed screw 14 in the spindle advancing direction side under the retraining condition in the spindle direction; and the second shaft end bearing 18 to support the shaft end of the feed spring 14 in the spindle retreating direction side under the nonrestraining condition in the spindle direction; are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle feed device for machine tools such as boring machines and machining centers, and in particular, it has a function of canceling thermal displacement of a spindle and / or spindle head and thermal displacement of a feed screw. Spindle device for machine tools.

[0002]

2. Description of the Related Art In machine tools, various technical improvements have been made to improve the machining accuracy, and thermal displacement due to temperature rise of the machine has a great influence on the machining accuracy. In horizontal boring machines and machining centers, the change in positioning accuracy is mostly due to the thermal displacement of the machine. In addition, since the spindle position accuracy is also the relative relationship between the work and the tool, there is a problem that no matter how much the spindle feed accuracy is increased, as long as there is thermal displacement, it will not directly improve the spindle position accuracy. is there.

Various measures have conventionally been taken against thermal displacement. For example, various attempts have been made to cool the lubricating oil of the spindle head with a cooler in order to reduce the amount of heat generation, or to use a material having a small thermal expansion coefficient for the spindle.

[0004]

However, even if the cause of thermal displacement is the heat generated from the machine side or the heat generated by processing, they are intricately entangled in relation to the structure of the machine. The fact is that it is not easy to take preventive measures.

Further, among machine tools, in a horizontal boring machine or a machining center, a ball screw is generally used as a feed screw in a feed mechanism for feeding a spindle or a spindle head in an axial direction. Causes elongation due to heat generation due to repeated feeding. It has been pointed out that this elongation has a great influence on the spindle position accuracy together with the thermal displacement of the spindle.

Therefore, an object of the present invention is to solve the problems of the prior art and improve the spindle position accuracy by offsetting the elongation of the spindle and / or spindle head due to thermal displacement and the elongation of the feed screw. It is to provide a spindle feed device for a machine tool aiming at the above.

[0007]

In order to achieve the above object, the present invention provides a spindle feed device for a machine tool, which comprises a feed screw / nut mechanism for feeding a spindle and / or a spindle head in a spindle direction. A first shaft end bearing that supports the shaft end of the feed screw on the main shaft forward direction side in a state of being constrained in a direction;
A second shaft end bearing for supporting the shaft end of the feed screw on the main shaft retracting direction side in a non-constrained state in the main shaft direction is provided.

Further, the present invention is characterized in that, in the above-mentioned structure, the second shaft end bearing has an angular bearing slidably mounted in the main shaft direction.

[0009]

According to the present invention, the feed screw is fixed and supported in the main shaft direction by the first shaft end bearing on the side in which the main shaft moves forward. On the other hand, in the second shaft end bearing, displacement is allowed in the main shaft direction, so the thermal displacement of the spindle head and / or the spindle and the thermal displacement of the feed screw are in opposite directions. Are offset. Therefore, the absolute value of the thermal displacement that actually affects the spindle position accuracy with respect to the work is greatly reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an embodiment in which the present invention is applied to a horizontal boring machine. Reference numeral 2 denotes a base, and 4 denotes a column that holds the spindle head and is movable back and forth in the ± Z direction of the axial direction of the spindle. A spindle 8 to which a tool is attached projects from the spindle head 6.

Feed nut 1 fixed to the lower surface of column 4
2 and the ball screw 14 form a feeding device for the main shaft 8 in the z-axis direction. The end of the ball screw 14 on the main shaft 8 side is supported by a first shaft end bearing 16, and the opposite end of the ball screw 14 is supported by a second shaft end bearing 18. Of the two shaft end bearings 16 and 18, an angular bearing is used for the first shaft end bearing 16 and can support a thrust load as well as a radial load. The ball screw 14 is restrained in the axial direction. Therefore, the displacement in the ± z direction is not allowed.

On the other hand, the second shaft end bearing 18
Has a structure that supports a radial load and is unconstrained in the ± z directions. Such a ball screw 14 is connected to a servomotor 22 via a flex coupling 20 that is displaced axially behind the second shaft end bearing 18.

Next, FIG. 2 shows the second shaft end bearing 18
Shows the configuration of. The outer bearing of the angular bearing 24 that rotatably supports the ball screw 14 is fixed to the sleeve 26. A sliding key 28 is provided on the outer peripheral portion of the sleeve 26, and the sliding key 28 engages with a key groove 32 axially formed on the inner peripheral surface of a bearing holder 30 fixed to the base 2. It is supposed to do.

The angular bearing 24 supports a thrust load as well as a radial load when the ball screw 14 rotates. Therefore, when receiving this thrust load, the angular bearing 24 is configured to be slidable in the axial direction with respect to the bearing holder 30 via the slide key 28 together with the sleeve 26.

The present embodiment is configured as described above, and its operation will be described next. First, looking at the thermal displacement of the spindle head 6 and the spindle 8 that occurs with the operation of the machine without considering the feed, the change in the distance L1 between the feed nut 12 and the spindle end determines the spindle position accuracy for the workpiece. Involved.

On the other hand, regarding the thermal displacement on the side of the ball screw 14 caused by the repeated feeding during the operation of the machine, the change in the distance L2 between the first shaft end bearing 16 and the feed nut 12 changes with respect to the work spindle. It affects the position accuracy.

Here, FIG. 3 shows changes with time of the distance L1 between the main shaft end and the feed nut 12 and the distance L2 between the first shaft end bearing 16 and the feed nut 12 due to thermal displacement. FIG. The change in L1 due to thermal displacement is represented by the curve δ1, and the change in L2 is represented by the curve δ2. The spindle head 6 and the spindle 8 extend in the + z direction. On the other hand, the ball screw 14 is fixed and supported by the first shaft end bearing 16 in the z direction, but is not supported by the second shaft end bearing 1.
In No. 6, since the angular bearing 26 is slidable in the z direction, the ball screw 14 is allowed to extend only in the −z direction.

Therefore, the thermal displacement as a whole is δ1 + δ
It becomes 2, but it is offset because it is the opposite in + z direction and -z direction. Therefore, the absolute value of the thermal displacement that actually affects the spindle position accuracy with respect to the work is greatly reduced.

[0019]

As is apparent from the above description, according to the present invention, the first shaft end bearing for supporting the shaft end of the feed screw on the main shaft advancing direction side in the state of being constrained in the main shaft direction and the main shaft direction in the main shaft direction. By supporting the feed screw with the second shaft end bearing that supports the shaft end of the feed screw in the spindle retracting direction in the unrestrained state, the thermal displacement of the spindle and / or the spindle head and the thermal displacement of the feed screw are Since they are offset, the position accuracy of the spindle can be greatly improved.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a second shaft end bearing of the lead screw bearings.

FIG. 3 is a diagram showing a change over time in a change amount of a distance L1 between a spindle end and a feed nut and a distance L2 between a first shaft end bearing and a feed nut due to thermal displacement.

[Explanation of symbols]

 2 Base 4 Column 6 Spindle Head 8 Spindle 10 Feeder 12 Feed Nut 14 Ball Screw 16 First Shaft End Bearing 18 Second Shaft End Bearing 24 Angular Bearing 26 Sleeve 28 Sliding Key 30 Bearing Holder 32 Keyway

Claims (2)

[Claims] 1. A spindle feed device for a machine tool having a feed screw / nut mechanism for feeding a spindle and / or a spindle head in a spindle direction, wherein a spindle end of a feed screw on a spindle advance direction side is supported in a restrained state in the spindle direction. And a second shaft end bearing that supports the shaft end of the feed screw on the main shaft retracting direction side in a non-constrained state in the main shaft direction.
A spindle feed device for machine tools, comprising: a shaft end bearing. 2. The spindle feed device for a machine tool according to claim 1, wherein the second shaft end bearing includes an angular bearing slidably mounted in the spindle direction.