KR860000762B1 - Preloading control device of a bearing - Google Patents

Abstract

The control appts.(200) regulates the pre-load supplied to machinery bearings that journal a rotation machinery member such as a shaft to a stationary member. Two pairs of trust sensors (137a,137b), mounted adjacent to the bearing, provide an electrical output signal indicative of bearing trusts. The output signal is supplied to an a-d converter(218) supplying an electronic processing circuit(220), typically a microcomputer. The pressure regulator(225) changes the pre-load to optimize the bearing conditions.

Description

Preload control device of bearing

1 is a block diagram of a control device of the present invention.

FIG. 1a is a block diagram of another embodiment of the lubricator shown in FIG.

2 is a graph showing the change relation between the bearing temperature and the percentage of the oil volume in the oil-air lubricated spray mixture.

3 is a side view of the high speed spindle of a machine tool.

4 is an enlarged view of a portion of the fast spin shown in FIG.

5 is a block diagram of a control device of another embodiment for controlling a machine tool having the spindles of FIGS. 3 and 4;

* Explanation of symbols for main parts of the drawings

16: temperature sensor 18: transducer

20: microcomputer (a kind of controller) 24a: oil valve

24b: air valve 25b: air supply source

110: rotating member 124a, 124b: gamma friction bearing

129: input means 137a, 137b: drust detector

139: lubrication means 140: temperature sensor

220: microcomputer (a kind of controller) 225: pressure control means

230: lubricating oil adjusting means

The present invention relates to a bearing preload control device for machine tools.

Rotating machines, such as machine tools and the like, typically include one or more ball bearings or roller bearings for journaling a rotating member such as a spindle to a stationary member such as a spindle head, the frictional forces generated between such bearings and the contacting surfaces thereof. It is already well known that lubrication of bearings with a single fluid such as oil or air or a lubricating fluid of a fluid mixture such as a spray mixture of oil and air can be reduced. Oil-air lubricating mixtures are particularly useful in that the air in the mixture reduces the heating of the bearings and the oil provides adequate lubrication for the bearing contact surfaces to extend the life of the bearings.

However, the use of oil-air mixtures to lubricate ball bearings or roller bearings causes problems in controlling the percentage of oil volume in the total mixture volume of the oil-air mixture. In other words, if the oil volume percentage in the oil-air mixture is too small, the lubrication of the bearings may not be satisfactory, resulting in premature wear of the bearings. On the other hand, if the oil volume percentage in the oil-air mixture is too large, it hinders the rolling of the bearings, resulting in overheating of the bearings, and thus shortening the life of the bearings.

Up to now, the adjustment of the oil volume percentage in the lubricating mixture of oil-air has been accomplished by artificially setting the condition of the oil and air mixing valves open-loop control. If the speed or the axial thrust of the rotating member journaled to the bearing suddenly changes, the percentage of oil volume in the lubricating mixture of oil-air will naturally change, thus causing too much oil volume in the lubricating mixture. Too little or too little will result in damage to the bearings. In addition, if the valve is blocked or the flow of oil is stopped, the volume of oil in the oil-air mixture may be insufficient.

Accordingly, the present invention has been proposed to solve such a problem, and its main object is to provide a control device for adjusting the lubrication of a bearing of a rotating machine.

Another object of the present invention is to provide a control device for automatically adjusting the lubrication of the bearing according to the temperature of the bearing to ensure the temperature decrease of the bearing to extend the life of the bearing.

Another object of the present invention is to automatically adjust the lubrication of the spindle bearings according to the spindle bearing temperature and to transfer the preload and spindle axis of the spindle bearings according to the deflection of the spindle in radial and axial directions, ie the thrust of the spindle. It is to provide a machine tool control device to adjust the rate.

According to the present invention, a control device for regulating lubrication for rollers and ball bearings for rotating machines is provided with a lubrication device for providing a bearing with a lubricating fluid which is a single fluid or oil-air mixture such as oil or air. In addition, a temperature sensor, such as a thermistor or a thermistor network, is provided to sense the bearing temperature, supplying an electrical signal indicative of the bearing temperature to a kind of controller such as a microcomputer. Depending on the bearing temperature, the microcomputer automatically adjusts the volume of lubricating fluid supplied from the lubricator to the bearing to ensure proper bearing lubrication at all times.

In particular, in the embodiment of the present invention, which is intended for use in machine tools such as horizontal or vertical boring mills, there is provided a thrust detector for generating an electrical signal by detecting radial and axial spindle thrusts. do. Therefore, the control device of the present invention not only adjusts the volume of the lubricating fluid of the spindle bearing according to the bearing temperature, but also adjusts the bearing stress by adjusting the preload of the spindle bearing and the feed rate of the spindle shaft according to the radial and axial spindle thrust. It can reduce, and thus optimize the performance of the machine tool.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention.

1, a control device for controlling a lubricating oil supplied to a mechanical bearing 12 which is used for a rotating machine such as a machine tool and supports a rotating member such as a shaft 14 to a fixed member (not shown) ( A block diagram of 10 is shown. The control device 10 includes a temperature sensor 16 in the form of a thermistor or the like, which is installed adjacent to the bearing 12 to generate an electrical output signal indicative of the bearing temperature. It is supposed to. In some cases, it is also desirable to use a pair of thermistors to measure both the temperature of the fluid entering the bearing (eg, air or oil) and the temperature of the fluid exiting from the bearing to determine the correct bearing temperature. The output signal of the temperature sensor 16 is supplied to an analog / digital (A / D) converter 18, in which the analog output signal is converted into a digital signal, which digital signal is typically It is supplied to the microcomputer 20 which is an electric signal processing circuit. The microcomputer 20 determines an appropriate amount of lubricating fluid supplied by the lubrication device 22 to lubricate the bearing 12 in response to the output signal of the A / D converter 18.

In an embodiment of the present invention, the lubricator 22 is configured to provide a lubricating oil spray mixture of oil and air, and is a pair of valves electrically connected to and electrically controlled by the microcomputer 20 ( 24a) and 24b. An air valve 24b is provided between the pressure air source 25b and the nebulizer 26 to control the amount of air flowing into the nebulizer 26 in accordance with a signal from the microcomputer 20. Typically each valve 24a, 24b consists of an ASCO model TX 8262208 produced by the United States Automatic Switch Company. The atomizer 26 atomizes the oil supplied from the oil source 25a through the oil valve 24a with the air supplied from the air source 25b through the air valve 24b to produce a spray mixture of oil and air. And the mixture is sprayed onto the bearing 12.

2 shows the relationship between the percentage of the oil volume in the lubricating oil-air mixture and the bearing temperature sense, referring to how the microcomputer 20 adjusts the percentage of the oil volume in the lubricating oil-air mixture. Can be clearly understood. As shown, the relationship diagram between the percentage of the oil volume in the lubricating mixture and the bearing temperature becomes concave upwards and has a minimum at point x. In the state where the relationship diagram between the oil volume percentage in the lubricating mixture and the bearing temperature becomes concave upward, the microcomputer 20 determines the ratio of the rate of change of the bearing temperature to the rate of change of the oil percentage in the lubricating mixture (ΔT / Write a program to calculate Δ%). If ΔT is small enough, the first derivative (dT / d%), which represents the relationship between bearing temperature and oil percentage, can be approximated. Since the first derivative (dT / d%) represents the slope of the curve and the slope of the curve shown in FIG. 2 becomes zero at the point (x) on the curve, the derivative (dT / d%) is on the curve of FIG. It becomes 0 at the relative minimum point (point x). Depending on the value of the calculated derivative (dT / d%), the microcomputer 20 can determine the percentage of oil volume required to maintain the minimum bearing temperature.

The treatment used by the microcomputer 20 to adjust the percentage of oil volume in the lubricating mixture is a dynamic treatment rather than a static control. Since the bearing temperature does not remain constant and changes due to factors such as the speed of the shaft and the load on the control ring, the microcomputer 20 continuously monitors the bearing temperature to maintain the percentage of oil volume to ensure proper bearing lubrication. Will be adjusted. Since the microcomputer 20 has a very different processing speed, the microcomputer 20 can respond to a rapidly changing bearing temperature, thereby ensuring proper bearing lubrication at all times.

In some cases it may be desirable to lubricate bearings of a rotating machine with a single lubricating fluid, such as oil or air, without lubricating the bearings using a mixture of several lubricating fluids such as air and oil. This can be done by using the lubricator 22 'of FIG. 1 instead of the lubricator 22 of FIG. The lubricator 22 'includes an electrically controlled single valve 24' installed in a pressure lubricating fluid source 25 'such as a gas such as air or a liquid such as oil, the single valve 24' being micro It acts to adjust the volume of the lubricating fluid supplied to the bearing 12 (shown in FIG. 1) in accordance with the signal from the computer 20. The volume of the lubricating fluid supplied through the valve from the lubricating fluid source 25 'is such that the bearing temperature is exactly the same as the bearing temperature varies with the percentage of the oil volume as shown in FIG. Microcomputer 20 depends on the bearing temperature exactly in the same way that microcomputer 20 controls valves 24a and 24b of lubricator 22 in FIG. Controlled by 20.

The control device of FIG. 1 is used for numerically controlled machine tools and is well suited for automatically regulating the lubrication of spindle bearings. By using the control it is possible to make the spindle speed and spindle load of the machine tool higher. In addition, as described below, the above-described control device can be adapted to control not only the bearing lubrication of the machine tool spindles, but also the preload of the spindle bearing and the feed rate of the spindle shaft. As such, the preload of the spindle bearing and By controlling the feed rate of the spindle shaft, the spindle speed and spindle load can be increased even higher. 3 and 4 show a portion of the high speed spindle assembly 100 of a numerically controlled machine tool, which is typically located within a frame, such as a machine tool spindle head (not shown), of the spindle axis. The feed rate, referred to as the feed rate, allows the machine tool to move linearly along the axis. Although the spindle assembly 100 can take the form of all known high speed spindles, in this embodiment a high speed spindle assembly as described in pending US Patent Application No. KT-1077, which is incorporated herein by reference. It consists of. As described in the mooring application, the high speed spindle assembly 100 includes a spindle 110 having an axially elongated bore formed therein for receiving shanks 112 of cutting tools therein. do. The spindle 110 is integral with the shaft of the motor 114, which is the stator 114a and the rotor 114b. The key 115 extending from the spindle 110 is coupled to an auxiliary keyway (not shown) formed in the rotor to secure the spindle to the rotor, so that the spindle 110 rotates with the rotor 114b. do.

The spindle 110 extends through the case 116 of the motor 114 and is journaled before and after the motor case 116 by the front and rear spindle bearings 118 and 120. The front spindle bearing 118 is composed of ball bearings 124a and 124b respectively installed between the shoulder 126 and the spiral portion 127 of the spindle 110, and the nut 128 is formed on the spiral portion 127. Is coupled to act to press the lower races of the ball bearings 124a and 124b against the shoulder 126. By adjusting the distance between the shoulder 126 and the nut 128, it is possible to change the pressing force or preload on the lower race of the ball bearing. The upper races of the ball bearings 124a and 124b are pressed against the vertical wall of the motor case 116 by the annular ring piston 129. The annular ring piston 129 is pressed by the bolt 134 to the motor case ( It is reciprocally positioned in the piston chamber 130 formed in the front bearing cap 132 cooperatively with 116, the bolt 134 is mounted at equal intervals around the bearing cap.

The amount of force or preload applied to the upper races of the ball bearings 124a and 124b is obtained from the pressure fluid source (not shown) with the connection passage 136 via the pressure regulator (described below). 136 is changed depending on the pressure of the pressure fluid flowing into the piston chamber 130. The pressure of the pressure fluid flowing from the pressure fluid source through the connecting passage 136 is changed by the pressure regulator in accordance with the radial and axial spindle bearing thrust. For this purpose, two pairs of spindle thrust detectors 137a, 137b, typically composed of magnetic or capacitive transducers, bearing adjacent to spindle shoulder 126 to measure radial and axial thrust respectively. Positioned in the cap 132. 4 is an enlarged view of a portion of the spindle assembly shown in FIG. 3, in which one of the pair of thrust detectors 137a measuring radial thrust is on the axis 138 of the spindle 110. FIG. It is positioned vertically in the bearing cap 132 adjacent to the shoulder 126 and the other (not shown) is positioned vertically in the bearing cap 132 adjacent to the shoulder 126 below the spindle axis. One of the pair of thrust detectors 137b that also measures the axial thrust is positioned horizontally in the bearing cap 132 adjacent the shoulder on the spindle axis and the other under the spindle axis 138. It is located horizontally in the bearing cap adjacent to it. The thrust detectors 137a and 137b are connected differently to generate a signal that varies with the spindle thrust in the radial and axial directions, respectively.

The output signal generated by each of the thrust detectors 137a and 137b controls the spindle axis feed rate and bearing ring preload as well as the percentage of oil volume in the lubricating mixture of oil-air, respectively. (Shown in FIG. 5). Controller 200 is an analog / digital (A / D) converter for converting analog signals from respective drust detectors 137a and 137b (shown in FIGS. 3 and 4) into digital signals ( 218, wherein the digital signal is transmitted to the microcomputer 220. The microcomputer 220 responds to the output signal from the A / D converter 218 to supply a pressure fluid source during a period in which the radial and axial thrusts on the spindle 110 (shown in FIG. 3) become large. And by adjusting the output signal supplied to the pressure regulator 225 installed in the connecting passage 136 (the figure 2 in Figure 2), the pressure of the pressure fluid flowing into the piston chamber 130 through the connecting passage 136 is increased. Accordingly, the force of the piston 129 relative to the upper races of the bearings 124a and 124b is increased to increase the preload of the bearing, thereby reducing the rattling of the bearing. If the radial and axial thrusts on the spindle 110 become large, they are likely to occur when the spindle speed is low and the force exerted on the cutting tool located within the spindle is large. In addition, during a period in which the radial and axial spindle thrusts become large, the microcomputer 220 supplies an output signal to the spindle head shaft drive motor amplifier (not shown) accordingly to reduce the shaft feed rate. In addition, during the period when the spindle thrust in the radial and axial directions becomes large, the microcomputer 220 is provided to the pressure regulator 225 to reduce the pressure of the fluid flowing into the piston chamber 130 through the connection passage 136. Command, thereby reducing the preload on bearings 124a and 124b. During the period in which the spindle thrust in the radial and axial directions is low, the microcomputer 220 also supplies an output signal to the spindle head shaft drive motor amplifier to increase the feed rate of the spindle shaft. In this way, microcomputer 220 dynamically adjusts the preloads for spindle bearings 124a and 124b.

In addition to the radial and axial spindle thrust, the microcomputer 220 also responds to the spindle speed of the machine tool as sensed by a tachometer or determined by the machine gear control system. During the period in which the spindle speed is increased, it is desirable to reduce the preload of the bearing, which is easily accomplished by the microcomputer 220 responding to the increase in the magnitude of the speed signal supplied thereto. Conversely, when the spindle speed decreases, the microcomputer 220 causes the piston chamber 130 (shown in FIG. 4) through the connecting passage 136 (shown in FIG. 4) to increase the preload of the bearing. The volume of fluid entering the furnace is increased by pressure regulation.

As shown in FIGS. 3 and 4, the lubrication passage 139 is provided to supply the lubricating mixture of oil air from the lubricator 230 shown in FIG. 5 to the bearings 124a and 124b. It is formed in the cap 132. The lubricator 230 is configured in the same way as the lubricator 22 shown in FIG. Within the bearing cap 132 is a temperature sensor 140 (shown in FIG. 4) located adjacent to the bearing 124a, which is mounted on the A / D converter 218 shown in FIG. Supply a signal that changes with temperature. In response to the digital output signal from the A / D converter 218, the microcomputer 220 (shown in FIG. 5) sends a pair of control signals to the lubricator 230 while adjusting the preload of the bearing and the spindle axis feed rate. The percentage of the oil volume in the lubricating mixture of oil-air supplied to the bearings 124a and 124b via the lubrication passage 139 in the manner as already described with reference to FIGS. 1 and 2 by Will be adjusted. Microcomputer 220 (shown in FIG. 5) is capable of detecting each change in radial and axial thrust that actually causes a change in spindle bearing temperature to provide a faster response of the lubricator. The output signals from the thrust detectors 137a and 137b are used. The microcomputer 220 can better control the lubrication of the spindle bearings by anticipating such changes before the spindol bearing temperature changes.

As described in pending US patent application no. KT-1977, the spindle 110 has a pair of tool fixing collets 140a and 140b, each formed integrally at both ends of the spindle. Each tool fixing collet is pressed radially inward to receive and fix the shank 112 of the cutting tool by respective collet nuts 142a and 142b which are screwed to the spindle 110 adjacent thereto. . The spindle is provided with a pair of hollow collet nut drivers 145a, 145b to prevent the collet nut from loosening at each end of the spindle during the high speed rotation of the spindle 110, the collet nut driver being adjacent to the collet nut. So that it is positioned on the spindle adjacent to the spindle end so that it can be disposed coaxially with it. The bore formed in each collet nut driver has dimensions to accommodate each collet nut. A set spline is formed on the inner surface of the bore. In the case of the collet nut driver 145a, a spline 146a is formed on the inner surface of the bore, and the spline is formed at the rear end of the collet nut 142a. The spline 146b and the collet 140a are adjacent to the outer spline 146c formed at the end of the spindle 110. Each collet nut driver is capable of sliding along the spindle between a first position, i.e., the innermost position, adjacent to the corresponding bearing cap, and a second, i.e., outermost position, away from the corresponding bearing cap. When the collet nut driver slides along the spindle to a first position adjacent to the corresponding bearing cap, the spline formed on the inner surface of the collet nut driver is engaged with the outer spline formed on the collet nut and the spindle respectively so that the collet nut is independent of the spindle. This prevents it from rotating on its own. When the collet nut driver slides along the spindle to the second position, the spline formed on the inner surface of the collet nut driver is only engaged with the outer spline formed on the collet nut, which causes the collet nut and the collet nut driver to correspond at the end of the spool line. Can be solved from Each collet nut driver is supported by axial movement once it is slid to an inner position by a pair of Vlier screws 148. The blower screw 148 extends in the radial direction of the spindle so that it can be unwound in an annular groove formed around the inner bore of the corresponding collet nut driver, and only one is shown in the figure. Proximity detection switches 150a and 150b are mounted on the bearing caps 132 and 160 adjacent to the front and rear collet nut drivers 145a and 145b, respectively. 145b acts as it slides inward adjacent bearing caps 132 and 160 to act to indicate that collet nuts 142a, 142b and spindle are engaged. That is, the proximity sensing switches 150a and 150b supply a signal to the microcomputer 220 indicating the coupling between the collet nut and the spindle during operation. When the collet nut drivers 145a and 145b are slid outward, the proximity sensing switches 150a and 150b stop operation, and thus the microcomputer 220 outputs a rotation stop signal to the driving amplifier. Supply to the control motor 114 to stop the rotation of the spindle. In this way it is possible to prevent damage to the cutting tool as well as the machine tool actuator when the cutting tool is not held firmly in the spindle.

Therefore, the control device for a rotary machine such as the machine tool of the present invention having the above configuration can adjust the percentage of the oil volume in the lubricating mixture of oil-air according to the bearing temperature, and thus the cucumber according to the bearing temperature. By adjusting the percentage of oil volume in the lubricating mixture of air, proper bearing lubrication is compensated, thus extending the life of the bearing.

While the embodiments of the present invention have been described above, the present invention is not limited to such embodiments and various other changes and modifications can be made within the scope of the invention as described in the appended claims.

Claims (5)

In the apparatus for controlling the preload of the bearing by detecting the thrust applied to the rotating member journaled by the anti-friction bearing on the frame, a signal indicating the detected thrust by detecting the thrust applied to the rotating member Sensing means (137a, 137b) for generating a pressure, pressurizing means (129) for applying pressure to the bearing to provide a preload on the bearing, pressure adjusting means (225) for adjusting the pressure to change the preload of the bearing; The controller 220 receives a signal from the sensing means indicating the thrust to the rotating member and the signal transmitted from the sensing means to continuously adjust the preload pressure applied to the bearing to obtain an optimum state. Means for connecting a controller to said pressure regulating means to regulate the operation of said regulating means accordingly. The unloaded controls. According to claim 1, Lubrication means 139 for supplying a lubricating fluid to the bearing, the temperature sensing means 140 for sensing the temperature of the bearing and transmitting a signal indicating the sensed temperature to the controller, and is supplied to the lubrication means And a lubricating fluid adjusting means (230) controlled by a controller in response to a signal transmitted from the sensing means to adjust the volume of the lubricating fluid. The machine tool spindles of claim 1 or 2, wherein the machine tool spindles are rotating members with feed means for axially moving the spindle in a movement to or away from the workpiece, thereby selectively feeding the feed rate of the spindle. And a means for connecting the regulator to the controller to operate the regulator in response to a signal transmitted from the sensing means so as to adjust the feed rate according to the optimum state. Preload Control. The speed signal according to claim 1 or 3, further comprising a tachometer for generating a speed signal indicating a rotation rate of the rotating member and the speed signal together with the thrust signal to determine the degree of preload pressure to be applied to the bearing. A preload control device for a bearing, comprising means for transmitting to a controller. 2. An annular piston according to claim 1, wherein the pressurizing means (129) consists of an annular piston positioned in the frame so as to pressurize the outer race of the bearing to provide preload to the bearing, and the adjusting means (225) is transmitted to the annular piston. The preload control device of the bearing, characterized in that composed of a pressure regulator for adjusting the hydraulic pressure.

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