JP2603002Y2 - Preload switching spindle unit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preload switching type spindle unit capable of adjusting a preload amount for a bearing supporting a main shaft.

[0002]

2. Description of the Related Art A spindle for a machine tool is provided with a mechanism for axially pressing a bearing for supporting a spindle in order to obtain an optimal spindle rigidity in a wide rotation range from low speed to high speed. In some cases, the preload of the bearing is switched according to the change of the preload. The spindle having such a preload switching means is required to have a means for measuring a preload applied to the bearing and a change amount thereof during the rotation of the main shaft in order to optimally switch the preload.

Conventionally, as a method of measuring the amount of preload of such a spindle bearing, as shown in FIG. 9, a strain gauge 74, which is an electric resistance strain gauge, is provided on a spacer 73 abutting on an outer ring 72 of a bearing 71. Is attached, and the strain amount of the spacer 73 is detected from the signal of the strain gauge 74 to calculate the preload amount of the bearing. The method of extracting the signal from the strain gauge 74 is as follows. The lead wire 75 that has been drawn out is inserted into an axial cutout groove 76 provided in the outer cylinder 1.
It is done by pulling out to the outside.

However, in the above method, when assembling the spindle, the lead wire 75 is inserted into the notch groove 76 during the assembly of the bearing 71 and the spacer 73 on the main shaft 2 so that each of the lead wires 75 does not interfere with the lead wire 75. It is necessary to assemble parts, and there is a drawback that assemblability is poor.

[0005] Further, since the notch groove 76 is provided in the outer cylinder 1 in the axial direction, the outer ring 72 of the bearing 71 is easily deformed.
There is a problem that the support accuracy of the main shaft is easily reduced.

Accordingly, an object of the present invention is to provide a spindle unit of a preload switching type capable of measuring a preload of a bearing while maintaining good accuracy and assemblability of a main shaft.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method in which a main shaft is rotatably supported via a bearing inside an outer cylinder, and a bearing is provided between the main shaft and the outer cylinder in an axial direction. In the preload switching spindle unit provided with a preload switching means for pressing the bearing, the spacer of the bearing has a plurality of protrusions projecting in one axial direction in the circumferential direction, and each of the protrusions is directly or indirectly provided on the outer ring of the bearing. And an electric resistance strain gauge is provided on this projection, an output terminal is provided on the outer peripheral surface of the spacer, an output end of a lead wire of the electric resistance strain gauge is connected to the output terminal, and the output terminal is connected to the output terminal. facing the connector insertion hole penetrating the outer cylinder in the radial direction is formed on the peripheral surface of the outer cylinder, strain measurement device to the connector insertion hole
Insert the output connector connected to
Connected to the sensor
The amount of strain in the spacer is detected by the above-mentioned strain measuring device, and the
The preload switching spindle unit is configured to calculate the preload of the bearing from the detected strain and control the preload switching means.

[0008]

In the preload switching spindle unit according to the present invention having the above structure, a plurality of projections are provided on the spacer, and each projection is directly or indirectly brought into contact with the outer ring of the bearing. When the preload is applied to the spacer, this preload concentrates locally on each protrusion of the spacer and causes each protrusion to be greatly distorted. And since the electric resistance strain gauge was provided for each projection, this electric resistance strain meter detects not the strain of the entire spacer, but a larger strain concentrated on each projection, and the detection output becomes larger. The apparent sensitivity increases.

Further, an output terminal is provided on the spacer, and a connector insertion hole which penetrates the outer cylinder is formed on a peripheral surface of the outer cylinder facing the output terminal. Just connect to the terminal,
When assembling the main shaft, bearings, and the like, it is not necessary to pull out the lead wire to the outside of the assembled spindle unit, and the assembling operation is simplified. Then, the signal from the electric resistance strain gauge is connected to the output terminal of the spacer by connecting the output connector inserted from the connector insertion hole of the outer cylinder with the bearing and spacer inserted in the outer cylinder. Take out.

[0010] Further, since the outer cylinder is not provided with a notched groove or the like in the axial direction, the bearing is not deformed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

As shown in FIGS. 1 and 4, the outer cylinder 1 is composed of two cylindrical members 1a and 1b which are fitted inside and outside, and both ends of the main shaft 2 are provided inside the outer cylinder 1 in a pair. It is rotatably supported via angular ball bearings 3, 4, 5, and 6. Each of the angular ball bearings 3, 4, 5 and 6
Are arranged in parallel via spacers 8 each provided with an air oil nozzle 7 for lubrication, and are attached to each other with their backs facing each other.

The bearings 3 and 4 at one end are directly incorporated into the outer cylinder 1, and the outer ring is fixed to the inner diameter surface of the outer cylinder 1, and the inner ring is fixed to the outer diameter surface of the main shaft 2.

A spacer 8 and a measuring spacer 9 are incorporated between the outer ring of the right bearing 4 and an end wall formed on the outer cylinder 1. As shown in FIGS. 2 and 3, the measurement spacer 9 has three protrusions 10 formed on the end surface thereof, which are in contact with the spacer 8, and a strain gauge 11 is attached to the inner diameter surface of each protrusion 10. Have been. In addition, each strain gauge 1
The lead wire 12 drawn out from the groove 1 is provided in the groove 1 provided in the spacer 9.
3 is connected to an output terminal 14 provided at the center of the measuring spacer 9.

The output terminal 14 is formed of a base 15 made of an insulating resin and a plurality of connecting pin terminals 16 protruding from the surface of the base 15. 9 is exposed in a recess 17 provided on the outer diameter surface.

On the other hand, a connector insertion hole 18 that penetrates the outer cylinder 1 in the radial direction is formed on the peripheral surface of the outer cylinder 1 facing the output terminal 14, and the connector insertion hole 18 is connected to a strain measuring device 20. The output connector 19 is freely inserted. This output connector 19
Is the pin terminal 1 on the surface facing the output terminal 14.
6 is provided with a socket hole for press-fitting.
And the strain gauge 11 are electrically coupled. As the output connector 19 and the output terminal 14, a commercially available multipolar coupling connector, a mini-plug or a socket for minute current, or the like can be used.

The strain measuring device 20 includes an AC bridge circuit, an amplifier, and the like, measures a resistance change in the strain gauge 11 from a signal obtained from the output connector 19, and obtains a strain amount of the measuring spacer 9 from the measured value. Is detected. This detected value is output to the preload control device 22.

The preload control device 22 includes a strain measuring device 20
From the strain amount of spacer 9 input from
The preload applied to 6 is calculated. Further, the obtained preload is compared with the allowable preload (Pmax) of the bearing, and a control signal is output to a hydraulic control circuit 32 described later based on the comparison result.

On the other hand, a bearing 5 at the other end supporting the main shaft 2,
In FIG. 6, as shown in FIGS. 1 and 4, the inner ring is fixed to the outer diameter surface of the main shaft 2 and the outer ring is fixed to the inner surface of a bearing box 23 inserted into the outer cylinder 1. Box 23
Are in contact with the outer ring end surface of the bearing 5 via the spacer. In this structure, when the bearing housing 23 moves in the axial direction,
The spacer presses the outer ring of the bearing 5, and a preload is applied to each of the bearings 3, 4, 5 and 6.

An axially movable intermediate ring 24 is inserted into the side of the bearing housing 23.
An adjustment member 25 for limiting the movement amount of the bearing housing 23 and the intermediate ring 24 is incorporated between the main shaft 2 and the main shaft 2. The adjusting member 25 includes a plurality of step portions 26 and 27. When the spindle unit is assembled (the state shown in FIG. 4), the adjusting member 25 is located between the intermediate ring 24 and the step portion 26, and between the bearing housing 23 and the step portion 27. Are provided with gaps δ ₁ , δ ₂ (where δ ₁ <δ ₂ ) having different sizes.

On both sides of the intermediate ring 24, a first pressure chamber 28 and a second pressure chamber 29 are formed.
Hydraulic control circuits 32 are connected to 8 and 29 via oil passages 30 and 31 inside the outer cylinder 1, respectively. The hydraulic control circuit 32 includes an electromagnetic control valve, a hydraulic pump, and the like, and supplies or discharges high-pressure oil to or from each of the pressure chambers 28 and 29 based on a signal from the preload control device 22.

A spiral groove 35 connected to the hydraulic control circuit 32 is formed on the outer surface of the bearing housing 23. When high-pressure oil is introduced from the hydraulic control circuit 32 into the spiral groove 35, The diameter of the box 23 is reduced to create a gap between the outer cylinder 1 and the bearing box 23 so that the bearing box 23 can move smoothly.

The spindle unit of this embodiment has the above-described structure. In this structure, the strain cage 11 and the output terminal 14 are mounted on the measuring spacer 9 installed between the bearing and the outer cylinder. Since there is no need to draw out the lead wire from the spacer 9 to the outside of the unit, the main shaft 2 and the bearings 3 and 4 can be assembled without worrying about drawing out and interference of the lead wire, and the unit can be easily assembled. it can.

On the other hand, in order to switch the preload of the bearing, an output connector 19 is inserted from the connector insertion hole 18 of the outer cylinder 1 and connected to the output terminal 14 in a state where the spindle unit is assembled. Strain cage 1
1 is connected.

In this state, in order to give the main shaft a large rigidity at the time of low-speed rotation and apply a reasonable preload at the time of high-speed rotation, first, in FIG. The high pressure oil is supplied to the pressure chamber 28 and the bearing housing 23 is supplied.
Is moved to a position where it contacts the step 27 of the adjustment member 25. Thus, since the bearing box 23 to move by a gap amount of [delta] _2, the bearing 3, 4, 5, 6 joined by a pressing force corresponding to the amount of movement of [delta] _2, the preload P ₁₀ is applied (see FIG. 5 ).

This pressing force is applied to the measuring spacer 9 via the outer ring of the bearing 4 and distorts the spacer 9, so that this strain is detected by the strain gauge 11, and the output terminal 14 and the output connector 19 are connected. It is sent to the strain measuring device 20 via the Strain measurement device 20 detects the amount of distortion from the input signal, and calculates the preload P ₁₀ acting from the strain amount detected that the preload control unit 22 to the bearing 3, 4, 5, 6.

When the rotation of the main shaft 2 increases from the above state, the preload of the bearing gradually increases as shown in FIG. 5A due to centrifugal force and thermal expansion of the main shaft. The increase is measured by the preload control device 22 via the strain gauge 11 and the strain measurement device 20, and the preload control device 22 measures the measured preload and the preload Pm of the allowable capacity of the bearing.
ax. When the preload exceeds the allowable maximum preload Pmax (time point N _1), the hydraulic control rotation 32
The control signal is output to the first pressure chamber 28, and the hydraulic pressure is released from the first pressure chamber 28, and hydraulic oil is introduced into the second pressure chamber 29. This allows
Due to the pressure of the second pressure chamber 29, the intermediate ring 24 is
Go until it abuts against the 6, the bearing 3-6, the amount of preload P ₂₀ which corresponds to the [delta] ₁ is added. For this reason, FIG.
As shown in the figure, the preload applied to the bearing is reduced and the medium preload P
Switch to ₂₀ .

Further, the number of revolutions of the main shaft 2 increases, and FIG.
Preload as shown in (c) and again reaches the allowable maximum preload Pmax (point of N _2), first and second pressure chambers 28,2
Drain hydraulic fluid from 9 (state shown in FIG. 4). This allows
Preload P ₃₀ corresponding to the amount of initial clearance during assembly the bearing 3-6 is added, the preload applied to the bearing as shown in FIG. 5 (d) is further reduced, it switched to a light preload P _30.

In the above embodiment, the preload of the bearing is set to 3
Although the structure of switching in stages has been described, if the number of steps or intermediate rings of the adjusting member is changed, two-stage switching or switching of four or more stages can be performed.

In order to generate the pressure for moving the bearing housing 23, compressed air or other fluid can be used without using high-pressure oil.

FIGS. 6 to 8 show another embodiment.
In FIG. 6, reference numeral 41 denotes a ball bearing for supporting the main shaft 2,
In this ball bearing 41, one end of an inner ring 42 protrudes in the axial direction to form a scoop 44, and a hole 45 penetrating in the axial direction is formed inside the scoop 44. An oil supply hole 61 extending from the hole 45 toward the raceway surface is formed.

The spacer 4 arranged on the side of the ball bearing 41
6, as shown in FIGS. 6 to 8, a lubricating projection 47 is provided at one location on the inner peripheral surface, and the lubricating passages 47, 49, the inner ring 42 of the ball bearing 41, Scoop 4
Injection ports 50 and 51 are formed toward the oil supply passages 48 and 49, respectively.
Is connected.

The end face of the spacer 46 is provided with a ball bearing 4.
Three or more projections 54 are formed in contact with one outer ring 43, and a strain gauge 55 is attached to the inner diameter surface of each projection 54. A radial through-hole 56 is formed on the peripheral surface of the spacer 46, and an output terminal 57 is incorporated in the through-hole 56.
Each strain cage 55 is connected via a lead wire 59 inserted into a groove 58 of the spacer 46.

Further, the output coupling 57 and the connector 19 inserted from the connector insertion hole 18 of the outer cylinder 1 are connected to the output terminal 57.

In the structure of this embodiment, the temperature of the oil injected from the injection ports 50 and 51 of the spacer 46 is controlled by the oil temperature control means 5.
The optimum preload can be set by controlling the temperature of the inner and outer rings 42 and 43 of the bearing 41 by controlling the preload 2 and 53. For example, when the inner ring temperature is higher than that of the outer ring at low speed rotation, the preload increases, and a large bearing stiffness suitable for low speed heavy cutting is obtained. Further, when the inner ring temperature is lower than that of the outer ring at the time of high-speed rotation, the preload decreases, and heat generation of the bearing is suppressed.

In this case, a change in the preload amount of the bearing 41 results in a change in the strain amount of the spacer 46, which is detected by the strain measuring device 20 via the strain gauge 55.

[0037]

The preload switching type spindle unit according to the present invention has a plurality of protrusions provided on the spacer, and each of the protrusions is brought into contact with the outer ring of the bearing. When the preload is applied to the spacer, the preload locally concentrates on each protrusion of the spacer and distorts each protrusion greatly.The electric resistance strain gauge detects a larger strain concentrated on each protrusion and detects , The detection output becomes larger, and the apparent sensitivity increases. Therefore, the preload of the bearing and the amount of change thereof can be measured more accurately.

Further, an output terminal is provided at the spacer of the bearing, and after assembling the unit, an output connector is inserted from the outside of the outer cylinder to connect the strain gauge to an external device.
The assembly of the main shaft and the bearing can be easily performed, and the workability of the assembly can be greatly improved. Further, since it is not necessary to provide a notch groove or the like in the axial direction on the inner diameter surface of the outer cylinder, deformation of the outer ring of the outer cylinder or the bearing can be suppressed, and the support accuracy of the main shaft can be maintained well.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment.

FIG. 2 is an enlarged cross-sectional view showing an output connector part according to the first embodiment;

FIG. 3 is a front view showing the measurement spacer according to the first embodiment;

FIG. 4 is an enlarged cross-sectional view showing the same preload switching mechanism.

FIG. 5 is a graph showing a preload switching process according to the first embodiment;

FIG. 6 is a sectional view showing another embodiment.

FIG. 7 is a front view showing the spacer shown in FIG.

FIG. 8 is a partially longitudinal side view of the spacer shown in FIG.

FIG. 9 is a sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer cylinder 2 Main shaft 3, 4, 5, 6 Bearing 9 Measurement spacer 11 Strain gauge 12 Lead wire 14 Output terminal 18 Connector insertion hole 19 Output connector 20 Strain measuring device 23 Bearing box 32 Hydraulic control circuit 41 Ball bearing 46 Spacers 48, 49 Oil supply passage 54 Projection 55 Strain gauge 58 Output terminal 59 Lead wire

Claims (1)

(57) [Scope of request for utility model registration] 1. A preload switching type spindle unit comprising: a main shaft rotatably supported through a bearing inside an outer cylinder; and a preload switching means for pressing the bearing in the axial direction between the main shaft and the outer cylinder. The bearing spacer has a plurality of protrusions projecting in one axial direction in the circumferential direction, and each of the protrusions directly or indirectly abuts the outer ring of the bearing, and an electric resistance strain gauge is provided on the protrusion. An output terminal is provided on the outer peripheral surface of the spacer, an output end of a lead wire of the electric resistance strain gauge is connected to the output terminal, and a connector that radially penetrates the outer cylinder on the outer peripheral surface of the outer cylinder facing the output terminal. Forming an insertion hole,
For output connected to a strain measurement device in this connector insertion hole
Insert the connector, connect to the output terminal, and
Amount of strain in the above spacers detected by an electric resistance strain gauge
A preload switching type spindle unit, wherein the preload switching unit is controlled by detecting the preload in the bearing from the detected strain and calculating the preload of the bearing from the detected strain .