1. Field of the Invention
The present invention relates to a machine tool such as a lathe, a milling machine, a machining center etc. comprising feeding system to linearly feed a tool rest, a tool post, a tool slide, a tool box and a slide to be fed such as a spindle head, a table etc.
2. Description of the Prior Art
An conventional general machine tool comprises feeding system composed of linear feed-driving means such as a ball screw etc., feed-moving bodies such as a ball nut etc. which engage with the feed-driving means and move along them, and position sensors such as a rotary encoder etc. to detect positions of the feed-moving bodies along the feed-driving means. The feeding system drive above-mentioned tool rest etc. and the slide such as the spindle head, the table etc. to move them linearly.
For example, the machining center comprises a table for installing an object to be machined (hereinafter referred to as a work piece) thereto, a spindle which is rotatably supported and can hold a tool at a front end portion thereof, and three pairs of feeding system which relatively move the table and the spindle in the mutually orthogonal three axes directions. Hence, through the relative displacement of the table and the spindle in the above-mentioned three orthogonal axes directions by driving the three pairs of feeding system, a three-dimensional machining can be realized for the work piece put on the table.
The above-mentioned three pairs of feeding system are disposed so that the each feed-driving means is mutually orthogonal, the table is driven by the first feed gear provided with the horizontal feed-driving means, and the spindle is driven by the second and the third feeding system whose feed-driving means are mutually orthogonal as well as at right angles to feed-driving means of the first feed gear. Generally, one feed gear is formed of one feed-driving means, and the slide to be fed such as above-mentioned table is driven by such feed gear and also guided by linear guide mechanisms (for example a rolling guide and a sliding guide etc.) arranged at both sides of the feed-driving means, the slide moving along the linear guide mechanisms.
There are work pieces not only having the comparatively simple work surfaces such as a horizontal surface and a perpendicular surface but also having complicated surfaces that need complex machining such as an inclined surface and a curved surface.
However, in the conventional machine tool comprising above-mentioned feeding system, since the spindle is driven so that it executes a parallel movement in a three-dimensional space with keeping a previously set posture thereof, that is to say, since it is impossible to swing the spindle in such a manner that a spindle center obliquely crosses feed directions of the feeding system, the work piece having above-mentioned complicated surface cannot be machined.
For solving this problem, such a machining center as shown in FIG. 6 has been developed. As shown in FIG. 6, a machining center 100 comprises a bed 101, a pair of columns 102 and 102 respectively erected from both sides of the bed 101, and a cross beam 103 horizontally linked with upper end portions of the column 102 and 102.
A table 105 which is driven by the first feed gear (not shown) having above-mentioned construction and reciprocally moves in the X-axis direction indicated by an arrow (X) is mounted on the bed 101, and a saddle 106 which is driven by the second feed gear (not shown) and reciprocally moves in the Y-axis direction indicated by an arrow (Y) is disposed at a front face 103a of the cross beam 103, and a slide 107 which is driven by the third feed gear (not shown) and reciprocally moves in the Z-axis direction indicated by an arrow (Z) is disposed at a front of the saddle 106. A head holder 108 which is driven by a first rotary feed gear (not shown) comprising a drive motor and a worm gear etc. and rotates in the direction of an arrow A is disposed at a front of the feed slide 107. A spindle head 111 which is supported by a support shaft 110, driven by a second rotary feed gear (not shown) comprising a drive motor etc., rotating in the direction of an arrow B is disposed between a pair of support arms 109, 109 of the head holder 108. The spindle head 111 rotatably supports a spindle 112 having a front end portion to hold a tool T and axially rotates the spindle 112 by an appropriate drive means such as a built-in drive motor (not shown) etc.
Hence, above-mentioned each feed gear (not shown) and the drive means (not shown) are controlled in their operations by a controller 113.
In the machining center 100 comprising above-mentioned composing elements, the table 105 and the spindle 112 can be relatively moved in the X-axis, Y-axis and Z-axis directions respectively by driving and controlling above-mentioned each feed gear (not shown) and the drive means (not shown) owing to the controller 113, furthermore, the spindle 112 can swing so that the spindle center thereof obliquely crosses the driving directions of the feeding system (not shown). Thus, the spindle 112 can be linearly and curvilinearly moved in the three-dimensional space. Therefore, the work pieces having the complicated surfaces are continuously machined at a time with being fixed on the table 105.
However, there is another defect as described below in the machining center 100 which enabled above-mentioned complicated machining.
The head holder 108 and the spindle head 111 are driven by the rotary feeding system comprising the drive motor and the worm gear etc., rotating in the directions of the arrow A and the arrow B respectively, whereby needing complicated constructions thereof, as a result the size of a mechanism itself becomes large in view of strength thereof. In addition, since the rotary feeding system must be stored in a limited space, they cannot be produced easily, consequently a manufacturing cost is heightened. It is also problem on accuracy that the rotary feeding system using the worm gear etc., have many error factors such as a backlash which disables a precise control of the head holder 108 and the spindle head 111.
It is a general advantage of the present invention to solve above-mentioned problems and to provide an improved machine tool which can linearly move a tool rest etc. and a slide to be fed such as a spindle head, a table etc. and comprises feeding system to rotate the slide so as to obliquely cross the directions of above-mentioned linear motions. A further advantage is to provide a machine tool comprising above-mentioned feeding system to machine work pieces having complicated surfaces.
The foregoing advantages are accomplished by the present machine tool that comprises feeding system to linearly feed a slide to be fed. In the machine tool, each feed gear comprises a first and a second feed mechanisms which are provided in parallel manner spaced apart from each other by a specified interval therebetween respectively comprising: a linear feed-driving means, a feed-moving body which engages with the feed-driving means and moves along the feed-driving means and a position sensor to detect positions of the feed-moving body along the feed-driving means, a first and a second support mechanisms which are respectively connected to each feed-moving body of the first and the second feed mechanisms and rotatably support the slide to be fed, and a control means to independently control the feed motions of the first and the second feed mechanisms, wherein at least either of support portions of the first and the second support mechanisms rotatably supporting the slide to be fed is disposed so as to move in such a direction as being separated from the other, and the slide to be fed is rotated on the basis of a difference in moving amount of the feed-moving bodies.
According to the present invention, two feed-moving bodies can be synchronously moved by independently controlling the feed motions of the first and the second feed mechanisms, on the other hand, those two feed-moving bodies can be moved in such a manner that there is a difference in moving amount therebetween. For synchronously moving two feed-moving bodies, the slide to be fed can be moved in a parallel manner, while for moving them such that there is a difference in moving amount therebetween, at least either of the support portions of the first and the second support mechanisms moves so as to separate from the other on the basis of the movements of the feed-moving bodies, as a result the slide to be fed rotates within a plane including two feed-driving means, consequently the slide to be fed moves with being rotated in the feeding directions of the first and the second feed mechanisms.
As mentioned above, in the present invention, the slide to be fed can be rotated. Therefore, even though a work piece has a complicated surface, it can be easily machined. In addition, since the slide to be fed can be rotated by one feed gear, the structure of the feed gear itself is made simple, consequently there is such an advantage that the machine tool in the present invention can be produced easily in comparison with an conventional one, as a result a manufacturing cost can be lowered.
There is another advantage that the support portions in the present invention can be disposed so as to be linearly moved relative to the slide to be fed. Thus, a simple and precise mechanism to move the support portions can be attained.
In addition, the feed-driving means in above-mentioned present invention can be composed of a linear motor. The drive means with using the conventional worm gear as described above have many error factors such as a backlash, therefore the slide to be fed cannot be precisely rotated. However, by using the linear motor, such error decreases, whereby the slide to be fed can be precisely rotated.
Furthermore, when the slide to be fed is provided with a tool hold mechanism to hold a tool, the tool can be linearly moved in the feeding directions of the feeding system and also can be rotated, whereby it is possible to machine the work piece having the complicated surface such as a curved one.
Furthermore, the machine tool in the present invention can comprise a pair of columns disposed in a parallel manner being spaced away from each other by a specified interval therebetween, a cross beam linked with the columns, and a table that is provided under the cross beam and is allowed reciprocating in orthogonal direction of the cross beam, wherein the first and the second feed mechanisms are disposed at a front face of the cross beam, the slide is provided with the tool hold mechanism to rotatably hold the tool, and the tool hold mechanism is movable across the feed-driving means. In such construction, the table and the tool hold mechanism can be linearly moved in two-axial directions of a moving direction of the table and a longitudinal direction of the cross beam both of which are disposed at right angles to each other, also can be linearly moved relative to such a direction as crossing above-mentioned two axes. In addition, the tool hold mechanism can be rotated within the plane including the first and the second feed mechanisms, whereby the work pieces having the complicated surfaces such as the curved ones etc. can be continuously machined at a time with being fixed on the table. Furthermore, when a circular table which can be horizontally rotated is set on the table, it is also possible to continuously machine work pieces having more complicated shapes at a time with being fixed on the table.