JPH071205Y2 - A device that optimally controls the preload on the spindle bearing of a machine tool using electric heat and oil - Google Patents

Description

[Detailed Description of the Invention] "Industrial field of application" This invention is intended to maintain the preload applied to the spindle bearing of a machine tool such as a machining center optimally according to the rotational speed of the spindle to perform accurate machining. Regarding the device.

"Prior Art" Generally, an outer ring spacer and an inner ring spacer are provided between rolling type spindle bearings such as ball bearings, which are mounted at intervals in the axial direction of a spindle of a machine tool. . Further, when the spindle bearing is assembled, a constant preload is always applied to the outer ring of the spindle bearing by hydraulic pressure or a push screw so that the spindle rotates normally during machining. When the main shaft is rotated in this state, the main shaft and the inner ring rotate together, but the outer ring remains stationary.

When the main shaft rotates, a centrifugal force acts on the main shaft bearing, so that the contact point between the main shaft bearing and the outer ring has a larger resistance than the contact point with the inner ring. As a result, at the contact point of the main shaft bearing with the outer ring, the main shaft bearing has a greater tendency to slide than at the contact point with the inner ring. This tendency becomes more remarkable as the number of rotations of the main shaft increases. Since the sliding friction produces more heat than rolling friction, the outer ring produces more heat than the inner ring.

Therefore, the outer ring spacer has a higher temperature than the inner ring spacer, and the outer ring spacer tends to expand as compared to the inner ring spacer. This tendency becomes more remarkable together with the fact that the cutting tool is cooled by the cutting oil and the cutting heat is not transmitted to the spindle.

For this reason, an extra force is applied to the preload applied to the outer ring, so that the balls of the main shaft bearing become slippery and do not rotate properly, so that accurate machining cannot be performed.
This tendency becomes more remarkable as the number of rotations of the main shaft increases.

Therefore, in order to optimally control the preload applied to the outer ring according to the spindle speed, the spindle speed is detected and the preload applied to the outer spacer is automatically changed using hydraulic pressure, or the push screw is adjusted. Then, such means as changing it are taken.

However, the means for changing the oil pressure according to the number of rotations of the main shaft has a drawback that the structure is complicated and expensive, and the viscosity of the oil used for the oil pressure changes with temperature, which makes control difficult. Further, the means for adjusting the push screw has a drawback that it is difficult to adjust and more expensive.

"Problems to be solved by the invention" The problem to be solved by this invention is to optimize the preload applied to the outer ring of the main shaft bearing according to the rotational speed of the main shaft without using hydraulic pressure or a push screw. To control.

"Means for Solving Problems" The features of the device of the present invention are as follows.

Mounted at intervals in the axial direction of the machine tool spindle,
It is provided between the outer rings of multiple rolling spindle bearings,
A preloading adjustment spacer having an oil chamber and having a heating resistor attached thereto, a passage communicating with the oil chamber provided in the spindle housing, and a temperature sensor for detecting the temperature of the adjustment spacer, The current adjustment spacer length calculated from the temperature detected by the temperature sensor is compared with the adjustment spacer length that obtains the optimum preload amount calculated from the spindle speed, and the temperature is adjusted to obtain the optimum adjustment spacer length. The spacer for heating is heated by energizing the heating resistor, and the temperature of the oil controlled at a constant temperature is supplied to the oil chamber through the passage to cool the spacer.

"Action" The heat generated in the spindle and spindle bearings due to processing is transferred from the outer ring of the spindle bearing to the adjustment spacer, and the adjustment spacer rises in temperature and expands, so extra force is applied to the preload on the outer ring.

The current adjustment spacer length is calculated from the temperature of the adjustment spacer detected by the temperature sensor, and the current preload amount is calculated from this adjustment spacer length.

On the other hand, the optimum preload amount obtained from the detected spindle speed is calculated, and the optimum adjustment spacer length is calculated by comparing the current preload amount and the optimum preload amount.

When the temperature of the adjusting spacer for correcting the current adjusting spacer length to the optimum adjusting spacer length is calculated, when the adjusting spacer temperature is lower than that temperature, the heating resistor is energized to raise the temperature. Adjust until the spacer length for optimum adjustment is reached.

On the contrary, when the temperature of the adjusting spacer is too high, the oil controlled to a constant temperature is sent to the oil chamber through the passage to lower the temperature,
Adjust until the spacer length for optimum adjustment is reached. If the spacer length for optimum adjustment is reached, no extra force will be applied to the spindle bearing.

[Embodiment] In FIGS. 1 and 2, 1a and 1b are rolling type main shaft bearings using, for example, ball bearings, and are mounted on a main shaft 22 described later at regular intervals. 2a and 2b are outer rings, and 3a and 3b are inner rings. An inner ring spacer 4 is provided between the inner rings 3a and 3b.

Reference numeral 5 is an adjusting spacer, in which a heating resistor 6 made of a nichrome wire is fixed with an adhesive 6 '. This adhesive uses a material of the adjusting spacer 5, for example, a material having a thermal conductivity close to that of iron.

In FIG. 1, the heating resistor 6 is represented by a spiral wire for convenience,
Actually, it is wound around the adjustment spacer 5 and attached. As the heating resistor 6, ceramic, plastic or the like can be used instead of the embodiment. An oil chamber 7 is recessed on the outer peripheral surface of the adjusting spacer 5. As shown in FIG. 2, the oil chamber 7 is provided with a narrow partition wall 8.

An auxiliary spacer 9 is provided between the front outer ring 2a and the adjusting spacer 5. Therefore, the adjusting spacer 5 is provided between the front and rear outer rings 2a and 2b via the auxiliary spacer 9.

Reference numeral 10 denotes a temperature sensor, which is fixed in the auxiliary spacer 9 by a material of the auxiliary spacer 9, for example, an adhesive having a thermal conductivity close to that of iron. The heat of the front outer ring 2a is transmitted to the adjusting spacer 5 via the auxiliary spacer 9 and detected by the temperature sensor 10.

It is also possible to omit the auxiliary spacer 9 and fix the temperature sensor 10 directly to the adjustment spacer 5 or to the front outer ring 2a or the rear outer ring 2b.

11a is an inflow side passage and 11b is an outflow side passage.
Both passages 11a and 11b penetrate 21 and communicate with the oil chamber 7 with the partition wall 8 interposed therebetween.

22 is the main shaft, 23 is the main shaft bearings 1a, 1b, the outer ring 2a,
Preloading is given via 2b.

FIG. 3 shows the temperature control means of the adjusting spacer 5, which is composed of a controller 12, a current adjusting device 13, a cooler 14 which is an oil supply means, a pump P, and a tank T.

That is, when the adjustment spacer 5 is heated, a constant value current is flown to the heating resistor 6 according to a command from the controller 12, and when cooled, the cooler 14 is controlled to a constant temperature according to a command from the controller 12. The oil is supplied from the pump P to the oil chamber 7 via the inflow side passage 11a, and is recirculated to the tank T via the outflow side passage 11b.

The controller 12 issues a command for controlling the temperature of the adjusting spacer 5 as follows.

As shown in FIG. 4, the optimum preload amount is calculated from the spindle rotation speed (determined from the control command value or the spindle rotation speed detection device outside the drawing) to calculate the optimum adjustment spacer length.

The length of the adjustment spacer 5 is compared with the current length of the adjustment spacer 5 calculated from the temperature of the adjustment spacer 5 detected by the temperature sensor 10 via the outside temperature conversion device, and the length of the adjustment spacer 5 is compared. Adjustment amount is required, and the adjustment spacer 5
The optimum temperature value of is determined.

The current temperature of the adjusting spacer 5 is compared with this optimum temperature, and if heating is required, the temperature of the heating resistor 6 is determined and an electric heating command is issued, and the current adjusting device (not shown) indicates the required current value. Electric current is sent to the heating resistor 6.

When cooling is required, a cooling oil supply command is issued,
Oil whose temperature is controlled to be constant by the cooler 14 is supplied to the oil chamber 7 by the pump P through the passage 11a.

"Effect of the device" By heating and cooling the adjustment spacer provided between the outer rings of the spindle bearing, the preload applied to the spindle bearing can be maintained at an optimum value according to the spindle speed, so accurate machining should be performed. The structure is extremely simple.

[Brief description of drawings]

FIG. 1 is a longitudinal cross-sectional view of the main part of the main shaft, and FIG. 2 is a schematic cross-sectional view of the main part showing the structure of the oil chamber. FIG. 3 is a schematic diagram of the temperature control means, and FIG. 4 is a control flowchart. 1a, 1b …… Main shaft bearing, 2a, 2b …… Outer ring, 5 …… Adjustment spacer, 6 …… Heating resistor, 7 …… Oil chamber, 10 ……
Temperature sensor, 11a, 11b ... passage, 12 ... control section, 14 ...
Cooler, 21 …… Spindle housing, 22 …… Spindle, P …… Pump

Continuation of the front page (72) Inventor, Hisashi Otsubo 1160 Hamanaka, Satosho-cho, Asaguchi-gun, Okayama Prefecture Yasuda Kogyo Co., Ltd. (56) References JP-A-50-20382 (JP, A) JP-A-60-135163 (JP) , A)

Claims (2)

[Scope of utility model registration request] 1. A preload-provided oil chamber provided between the outer rings of a plurality of rolling type spindle bearings mounted at intervals in the axial direction of the spindle of a machine tool and having a heat generation resistance. The adjustment spacer to which the body is attached, the passage communicating with the oil chamber provided in the spindle housing, the temperature sensor that detects the temperature of the adjustment spacer, and the current adjustment spacer length calculated from the temperature detected by the temperature sensor And the adjustment spacer length that can obtain the optimum preload amount calculated from the spindle speed, compare the adjustment spacer length to the temperature at which the optimum adjustment spacer length is obtained by heating the heating resistor by heating it to a constant value. It has a temperature control means for supplying the oil whose temperature is controlled to the oil chamber through a passage to cool the oil.
A device that optimally controls the preload on the spindle bearing of machine tools by using electric heat and oil. 2. The spindle of a machine tool according to claim 1, wherein the adjusting spacer is provided between the outer rings via the auxiliary spacer, and the temperature sensor is provided on the auxiliary spacer. A device that optimally controls the preload on the bearing by using electric heat and oil.