JPH0453457Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a spindle unit, and particularly to a spindle unit with switchable preload.

[Conventional technology]

JP-A-62-124805 discloses a technique in which the preload applied to a rolling bearing that supports the main shaft is mutually switched between constant pressure preload and fixed position preload. When adding a fixed position preload to a rolling bearing, this technology uses hydraulic pressure to force the presser fitted with the rolling bearing to position it in a fixed position, thereby creating a fixed position preload. is a technology that releases the hydraulic pressure and uses only the coil spring to provide constant preload.

[Problem that the invention attempts to solve]

In the above conventional technology, in order to switch from fixed position preload to constant pressure preload, there is no means to push the hydraulic piston back when the hydraulic pressure is released, so the hydraulic piston does not return due to the sliding resistance of the O-ring, making it impossible to switch to constant pressure preload. There was a problem that a situation might arise. The object of the present invention is to solve the above-mentioned problems and provide a spindle unit that can reliably switch from fixed position preload to constant pressure preload.

[Means for solving problems]

In order to achieve the above object, the present invention includes a housing, a main shaft supported via a bearing sleeve having one end fitted to the housing with a front rolling bearing and the other end fitted with a rear rolling bearing, and a main shaft that is supported by the bearing sleeve in the axial direction. a preload spring that biases the bearing sleeve in the axial direction to apply a constant pressure preload to the rear rolling bearing; a hydraulic piston that applies a fixed position preload to the rear rolling bearing by pressing the fixed position preload to a fixed position in the axial direction via a fixed position preload adjustment spacer, and a hydraulic piston that applies a fixed position preload to the rear rolling bearing; The device is characterized in that it includes a bias spring that biases in the opposite direction.

[Effect]

In the spindle unit of the present invention, the bias spring biases the fixed position preload adjustment spacer and pushes the hydraulic piston back when the hydraulic pressure is released, creating a gap between the fixed position preload adjustment spacer and the bearing sleeve, so that the bearing sleeve can be fixed at the fixed position. It is not restricted by the positional preload spacer and can reliably switch to constant pressure preload using only the preload spring.

〔Example〕

FIG. 1 is a sectional view showing the structure of the spindle unit of the present invention, and FIG. 2 is a partial view of the preload mechanism of the spindle unit of the present invention.

An embodiment of the present invention will be described based on FIGS. 1 and 2. A main shaft 2 is supported in a housing 1 at one end 2a by a front rolling bearing 3 and at the other end 2b via a bearing sleeve 5 into which a rear rolling bearing 4 is fitted. The bearing sleeve 5 has an outer circumferential portion fitted into the housing 1 so as to be slidable in the axial direction, and a flange portion 5a which is biased rightward in the drawing by a preload spring 6 disposed in the housing 1 and fitted into the inner surface. A constant pressure preload is applied to the rolling bearing 4. In this embodiment, a flange portion 5a formed integrally with the bearing sleeve 5 is biased in the axial direction by a preload spring 6, but the flange portion 5a is separate and connected to the bearing sleeve 5 by a connecting means such as a bolt. May be combined.

The housing 1 is provided with a hydraulic piston 7 for pressing the bearing sleeve 5 to a fixed position in the axial direction. The hydraulic piston 7 is biased toward the right in the drawing by introducing hydraulic pressure into the hydraulic chamber 8 through the oil supply hole 9, and is positioned by having a portion 7a of its tip abut against a housing cover 10 fixed to one end of the housing 1. . The other end portion 7b of the hydraulic piston 7 is in contact with one end of the low position preload adjustment spacer 11,
The other end of the fixed position preload adjustment spacer 11 is the bearing sleeve 5
is in contact with the flange portion 5a. Therefore, when hydraulic pressure is introduced into the hydraulic chamber 8, the bearing sleeve 5 is pressed to a fixed position in the axial direction by the hydraulic piston 7 via the fixed position preload adjustment spacer 11, and a fixed position preload is applied to the rolling bearing 4 fitted on the inner surface. Add. The state at this time is shown in FIG. 2a. An O-ring 12 is attached to a part of the sliding surface between the housing 1 and the hydraulic piston 7 to prevent oil leakage.

A bias spring 13 for pushing back the fixed position preload adjustment spacer 11 in the opposite direction (to the left in the drawing) with respect to the biasing direction of the hydraulic piston 7 (to the right in the drawing) when the hydraulic pressure in the hydraulic chamber 8 is released is attached to the housing. The bias spring 13 is disposed on the cover 10, and when the hydraulic pressure is released, the bias spring 13 pushes back the fixed position preload adjustment spacer 11 with a biasing force greater than the sliding resistance between the O-ring 12 and the hydraulic piston 7, thereby creating a fixed position preload with the bearing sleeve 5. Adjustment spacer 1
1, so that only a constant preload by the preload spring 6 is applied to the bearing sleeve 5. The state at this time is shown in FIG. 2b.

[Effect of idea]

As mentioned above, the present invention is equipped with a bias spring to push back the hydraulic piston in the preload type switching mechanism, which eliminates incomplete preload switching due to sliding resistance between the hydraulic piston and O-ring, and ensures reliable preload switching. can.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of the spindle unit of the present invention, and FIG. 2 is a partial view of the preload mechanism of the spindle unit of the present invention. Explanation of symbols of main parts, 1...Housing, 2
... Main shaft, 3, 4 ... Rolling bearing, 5 ... Bearing sleeve, 6 ... Preload spring, 7 ... Hydraulic piston, 11 ... Fixed position preload adjustment spacer, 13 ... Bias spring.

Claims (1)

[Scope of utility model registration request] a housing; a main shaft supported via a bearing sleeve having one end fitted to the housing with a front rolling bearing and the other end fitted with a rear rolling bearing; and axially biasing the bearing sleeve to engage the rear rolling bearing. A spindle unit having a preload means for applying a preload, a preload spring for urging the bearing sleeve in the axial direction and applying a constant pressure preload to the rear rolling bearing, and a preload means for applying a preload to the rear rolling bearing; a hydraulic piston that presses the rear rolling bearing to a fixed position in the axial direction and applies a fixed position preload to the rear rolling bearing; and a bias spring that biases the fixed position preload adjustment spacer in a direction opposite to the biasing direction of the hydraulic piston. A spindle unit characterized by being equipped with.