Heat exchange – Movable heating or cooling surface – Rotary drum
Patent
1989-10-02
1993-03-30
Ford, John K.
Heat exchange
Movable heating or cooling surface
Rotary drum
165 47, 236 78B, 236 91F, 62210, 62201, 62211, 62434, 62435, 62DIG10, F28F 2700, B23Q 1114
Patent
active
051975378
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a method of and apparatus for controlling the temperature of a machine tool. More particularly, the present invention relates to a method of controlling the temperature of the body of a machine tool which enables a reduction in the size of the transient deviation and steady-state deviation and also pertains to an apparatus for carrying out the temperature control method.
2. Background Art
The body of a machine tool is deformed by the environmental temperature, heat from a heat generating portion, etc. The deformation of the machine body affects the machining accuracy and therefore it has heretofore been general practice to control the temperature of each part of the machine body to be a constant temperature. Although a variety of temperature control methods for this purpose have been proposed, an indirect control method wherein a temperature-controlled fluid is arranged to flow through a heat generating portion of a machine tool to thereby cool the heat generating portion is generally carried out. The set temperature for the fluid is controlled so as to follow up the room temperature or the temperature of one of the constituent elements that has the largest time constant. This method minimizes the thermal deformation and reduces machining errors. This is a known art, and these methods are called the room temperature follow-up control or the machine body temperature follow-up control.
Hitherto, two position control has been employed as a control action used when the indirect control of a machine tool by the fluid temperature is effected by the room temperature follow up control or the machine body temperature follow-up control. In the case of two-position control, the temperature fluctuation range .sigma.(k) of the fluid temperature controlled may be expressed as follows: apparatus; Kr: the coefficient of heat dissipation (Kcal/h..degree.C.); .DELTA.: the differential gap (.degree.C.) of the two-position (ON-OFF action) temperature controller; L: the dead time (h) from the time when the control action is initiated to the time when a temperature change is detected with a temperature detector (sensor); T: the time constant (h) of an object of temperature control; .gamma.: the load factor (the ratio of the quantity of heat generated to the cooling capacity); and exp: natural logarithm.
In two-position control, the steady-state deviation .DELTA..theta..sub.0 of the control variable (controlled fluid temperature) that may be expressed by the following equation is produced: deviation .DELTA..theta..sub.0 increase as QR increases. As the quantity of heat generated in the machine tool increases, QR is increased, as a matter of course. Therefore, in recent machine tools in which a large quantity of heat is generated, the temperature fluctuation range .sigma. and the steady-state deviation .DELTA..theta..sub.0 may exceed the allowable values.
If PID control which includes an integral control action is employed, the steady-state deviation .DELTA..theta..sub.0 becomes 0, but the PID control has the problem that, if detection is not carried out at a point where the dead time is minimized (i.e., at the outlet of the heat exchanger in the case of the temperature control of a machine tool), the transient deviation of the control variable increases and the settling time becomes longer. Indirect control in which the fluid temperature at the outlet of the heat exchanger is detected to effect control, however, leads to the steady-state deviation .DELTA..theta.w.sub.1 (.degree.C.) of the machine body (i.e., the difference between the temperature of the machine wall temperature and the temperature of the heat transfer fluid) expressed by the following equation: heat transfer fluid; .alpha.: the mean heat transfer coefficient (kcal/m.sup.2 h.degree.C.) between the machine wall and the heat transfer fluid; F: the heat exchanging surface area (m.sup.2); and W: the water equivalent of the heat transfer fluid, i.e., the product (kcal/h.degree.C.) of the volumetric rate
REFERENCES:
patent: 2606747 (1952-08-01), Williams
patent: 3066578 (1962-12-01), Olton
patent: 3315892 (1967-04-01), Hoake
patent: 3480076 (1969-11-01), Tomita
patent: 3581986 (1971-06-01), Magri
patent: 3772896 (1973-11-01), Rao
patent: 3859812 (1975-01-01), Panlak
patent: 4719830 (1988-01-01), Kawada et al.
patent: 4922996 (1990-05-01), Rees
Chigira Junji
Urano Koichi
Ford John K.
Kanto Seiki Co. Ltd.
LandOfFree
Apparatus for controlling temperature of machine tool does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for controlling temperature of machine tool, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for controlling temperature of machine tool will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1275137