Abrading – Precision device or process - or with condition responsive... – Controlling temperature
Reexamination Certificate
2000-08-10
2003-12-30
Rose, Robert A. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
Controlling temperature
C451S449000, C451S053000
Reexamination Certificate
active
06669532
ABSTRACT:
TECHNICAL FIELD
The present invention relates to machining apparatus and process in which a cold-gas-blow cooling is used.
BACKGROUND ART
In a grinding, cutting or other machining operation, a grinding or cutting oil or other liquid coolant (hereinafter referred to as a liquid coolant) is used conventionally for cooling a workpiece and a machining tool, thereby preventing a burning at a grinding or cutting point and removing cutting chips during the machining operation. Recently, in the interest of improving the working environment, there is designed a machining process with cold-gas-blow cooling in which a flow of cold gas (a stream of a gas having a low temperature) is used in place of the liquid coolant. This machining process with the cold-gas-blow cooling is advantageous over the conventional machining process in which the liquid coolant is used for cooling the workpiece and the machining tool, for example, in terms of freedom from splashes of the liquid coolant and also easier recycling of the cutting chips. However, since the gas used in the machining process with the cold-gas-blow cooling has a lower thermal conductivity and a smaller thermal capacity than those of the liquid, heat generated at the machining point is not sufficiently removed by the gas. Thus, the workpiece and the machining tool are likely to be affected by the generated heat, possibly causing problems such as deterioration of dimensional accuracy due to thermal expansion of the workpiece and deterioration of machining performance of the machining tool.
JP-A-56-9166 discloses a machining process including a machining step of machining the workpiece with a supply of a liquid coolant, and a cold-gas-blow machining-tool cooling step of cooling the machining tool with a supply of a cold gas blow. That is, when the workpiece has a predetermined dimension as a result of machining of the workpiece in the machining step, the machining step is followed by the cold-gas-blow machining-tool cooling step. In the cold-gas-blow machining-tool cooling step, the cold gas blow is supplied to the machining tool until the temperature of the machining tool (the temperature of the atmosphere within a cover covering the machining tool) is lowered to a predetermined temperature or less.
It is possible to apply this technique disclosed in the publication to a machining process having a machining step in which the liquid coolant is replaced by the cold gas blow such that the flow rate of the cold gas blow is controlled on the basis of the temperature of the machining tool during the machining operation. However, in this machining process, it is not possible to assure a sufficient cooling effect, thereby causing thermal expansion of the workpiece and deterioration of cutting performance of the machining tool, and possibly deteriorating machining accuracy.
DISCLOSURE OF INVENTION
The object of the present invention is to obtain a cold-gas-blow cooling machining process and a cold-gas-blow-cooling type machining apparatus which are capable of minimizing thermal influences on the workpiece and the machining tool. This object may be achieved by a machining apparatus or process according to any one of the following modes of the present invention, which are numbered and dependent from each other, where appropriate. It is to be understood that the following modes are provided to facilitate the understanding of the present invention, and that the technical features and the combinations of the technical features disclosed in the present specification are not limited to the following modes.
(1) A cold-gas-blow-cooling type machining apparatus including a relative movement device which moves a workpiece and a machining tool relative to each other, and a cold-gas-blow supply device which supplies a cold gas blow to a machining point at which the workpiece is machined by the machining tool, the machining apparatus being characterized by including:
a workpiece-temperature detecting device which detects a temperature of the workpiece; and
a machining-condition control device which controls at least one of the relative movement device and the cold-gas-blow supply device, on the basis of the temperature of the workpiece which is detected by the workpiece-temperature detecting device.
In the cold-gas-blow-cooling type machining apparatus described in the present mode, the temperature of the workpiece is detected by the workpiece-temperature detecting device. This workpiece-temperature detecting device may include a contact-type surface-temperature detecting device which is adapted to detect the temperature of the surface of the workpiece with its temperature sensor being brought into contact with the surface of the workpiece, or alternatively may include a non-contact-type surface-temperature detecting device which is adapted to detect the temperature on the basis of a radiant energy radiated from the workpiece. Since the workpiece radiates an electromagnetic wave having a wavelength distribution and an intensity which vary depending upon the temperature of the workpiece, the non-contact-type surface-temperature detecting device can detect the temperature of the workpiece without contact thereof with the workpiece, for example, by detecting a temperature rise of a subject body which is irradiated with the electromagnetic wave, or by detecting the intensity or wavelength of the electromagnetic wave. The non-contact-type surface-temperature detecting device may be a radiation thermometer or a thermography, for example.
The workpiece is one of sources which generate heat during the machining operation, and the generated heat directly affects the machining accuracy of the workpiece. In this view, it is appropriate to control the machining condition on the basis of the temperature of the workpiece. Where the cold-gas-blow supply device and the relative movement device are controlled on the basis of the temperature of the workpiece, the machining point can be effectively cooled, even where the cold gas blow has thermal capacity smaller than that of the liquid coolant, making it possible to obtain a suitable cooling effect. Thus, it is possible to minimize thermal expansion of the workpiece and deterioration of the machining performance of the machining tool, and accordingly minimize deterioration of the machining accuracy. That is, since the machining accuracy eventually affects the workpiece, the machining accuracy can be more effectively improved where the machining condition is controlled on the basis of the temperature of the workpiece, than where the machining condition is controlled on the basis of the temperature of the machining tool.
Further, in the cold-gas-blow-cooling type machining apparatus described in the present mode in which the liquid coolant is not used at all, there is no risk of deterioration of the working environment due to use of the liquid coolant.
It is noted that the cold-gas-blow-cooling type machining apparatus described in the present mode can be advantageously applied to a metallic-workpiece machining apparatus designed to machine a metallic workpiece which tends to be considerably thermally expanded in the machining operation. The cold-gas-blow-cooling type machining apparatus of the present mode in which the cutting condition is controlled on the basis of the temperature of the workpiece is suitable for machining a workpiece made of aluminum, copper, casting or other material having a comparatively large coefficient of linear expansion.
(2) A cold-gas-blow-cooling type machining apparatus according to mode (1), wherein the relative movement device includes a spindle which holds the workpiece and rotates the workpiece about an axis of the workpiece.
In the cold-gas-blow-cooling type machining apparatus described in the present mode, the workpiece is held and rotated by the spindle. The rotated workpiece and the machining tool are further moved relative to each other in at least one direction, whereby the workpiece is machined by the machining tool. The cold-gas-blow-cooling type machining apparatus of the present mode
Katsuta Mamoru
Kobayashi Yasunori
Kubo Yuji
Kumazawa Tadashi
Mizutani Yoshihiro
Burns Doane , Swecker, Mathis LLP
Rose Robert A.
Toyota Jidosha & Kabushiki Kaisha
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