CN104595361A - Bearing and screw equipped roller unit and manufacturing method for the same - Google Patents

Abstract

The invention starts with a roller unit comprising a roller bearing (12), a screw (14) and retaining means for retaining the screw (14) in a pre-assembled configuration of the roller unit. It is proposed that the retaining means is formed as an elastic ring (16) which is in direct contact with the central hole (20) of the inner ring (18) of the bearing (12) and the parts (22, 26) of the screw (14), said A portion of the screw has a diameter at least as large as the diameter of the threaded portion of said screw.

Description

Roller unit with bearing and screw and method of manufacturing the same

technical field

The invention relates to a roller unit, in particular an idler unit or a belt tensioner comprising a roller bearing, a screw and holding means for holding the screw in a pre-assembled state of the roller unit.

Background technique

Roller units of this type are often used to tension or guide traction devices, such as belts or chains in automobiles, and are delivered to car manufacturers as pre-assembled units. For safety reasons, accidental disassembly of the unit should be avoided during assembly or installation, especially considering the risk that the unit may be reassembled in the wrong way.

Document DE 19836191 A1 discloses a belt tensioner in which the screw is provided with an undercut, ie with a portion of reduced diameter and with a C-shaped retaining ring engaging the undercut. However, DE19836191A1 requires the use of expensive non-standard screws with undercuts and is therefore not cost-effective.

Other documents, such as EP2339211A1 and DE10003208A1, relate to belt tensioner units comprising distance elements or spacers which are arranged between the screw and the inner ring of the roller bearing and which secure the axial end face of the inner ring A given distance from the motor base or other support on which the unit should be mounted. The spacers are then secured to the screws by elastic o-rings.

Changes in the spacer elements and/or the inner ring during shipping can cause impacts between the spacer elements and the inner ring, which can cause the elastic o-ring to loosen, making the assembly not very shockproof. Furthermore, the introduction of spacer elements inevitably increases the geometrical risk of the unit after mounting on its support.

Contents of the invention

The invention solves the above problems by providing a roller unit and a method of manufacturing the same according to the independent claims. Preferred embodiments of the invention can be derived from the dependent claims.

The invention starts from a roller unit comprising a roller bearing, a screw and holding means for holding the screw in a pre-assembled configuration of the roller unit.

It is proposed that the retaining means is formed as an elastic ring which is in direct contact with the central bore of the inner ring of the bearing and with a part of the screw having a diameter at least as large as the diameter of the threaded part of the screw. The advantage of the solution of the invention is to avoid the use of expensive special screws with reduced diameter portions, while ensuring reliable retention of the screws.

Preferably, the roller unit is a belt tensioner or an idler pulley for tensioning or guiding a traction device in an automobile, wherein the pulley is attached to the outer ring of the bearing. A high degree of reliability is particularly important in this highly automated technical field with highly optimized processes.

The pulleys can be made of plastic, molded in one piece with the outer ring or can be fabricated from stamped sheet metal. Roller bearings may be single or double row ball bearings or bearings with cylindrical or other types of roller elements. It is entirely possible to implement the invention using cost-effective pulleys, bearing rings or simple bearings.

The expression "diameter of the threaded portion" refers to the major or outer diameter of the thread.

In a preferred embodiment of the invention, the elastic ring is arranged completely within the axial range covered by the bearing inner ring. The function of the elastic ring is to hold the screw during shipping and assembly. Once the unit is mounted to the engine housing or gearbox housing, the belt tensioner is secured and the screw is clamped between the screw head or washer and the unit's support (i.e. motor mount or gearbox housing) Inner ring of a roller bearing, wherein additional distance elements may or may not be provided between the inner ring and the support.

Preferably, the screw has a shank whose smallest diameter corresponds to the diameter of the threaded portion, ie without undercut portions. This results in a cost reduction compared to a shank with an undercut.

In addition, it is proposed that the central bore of the inner ring of the bearing has a simple cylindrical inner surface, in particular can be without grooves or other structures and does not require high precision. The present invention enables the use of cost-effective standard inner rings.

In a preferred embodiment of the invention, the elastic ring is radially compressed by the inner surface of the bore. This produces a good press-fit engagement between the inner ring and the elastic ring.

Preferably, the inner diameter of the elastic ring is larger than the outer diameter of the threaded portion of the screw in an uncompressed state of the elastic ring, and when the elastic ring is installed in the roller unit, the inner diameter of the elastic ring leans against the threaded portion of the screw by contact force. If no screw is provided, the inner diameter of the elastic ring will be smaller than the outer diameter of the threaded portion of the screw when compressed by the inner ring of the bearing.

In an alternative embodiment of the invention, the elastic ring is integrally molded with the inner ring. This reduces the assembly costs of the unit.

In addition, the pulley can be combined with the bearing outer ring by overmolding. In particular, the elastic ring and the pulley can be produced in the same injection molding process in order to achieve a further cost reduction.

Another aspect of the invention contemplates a method for manufacturing the above-mentioned roller unit. It is proposed that the method comprises the step of radially compressing the elastic ring to fit the elastic ring into the central bore of the inner ring of the bearing. This achieves a good and reliable press-fit engagement between the inner ring and the elastic ring, while keeping the assembly process simple.

In one possible embodiment of the invention, the elastic ring fits on the threaded portion of the screw before being compressed and fitted into the central hole of the inner ring. As a result of the uncompressed inner diameter of the elastic ring, the step of fitting the elastic ring on the threaded part is very simple, even with bare hands.

Furthermore, it is proposed to carry out the step of radially compressing the elastic ring when the screw is placed in the central hole of the inner ring. Inserting the screws into the inner ring before providing the elastic retaining ring greatly simplifies the assembly step.

Description of drawings

The above description of the invention together with the appended claims, the drawings and the following description of the preferred embodiments present several salient features of the invention in particular combinations. A skilled person can easily consider other combinations or subcombinations of these features in order to adapt the invention defined by the claims according to specific requirements.

1 is a sectional view of a roller unit according to the present invention;

2a to 2c are schematic diagrams of a first assembly process of the roller unit according to FIG. 1; and

3a to 3c are schematic illustrations of a second assembly process of the roller unit according to FIG. 1 .

Detailed ways

FIG. 1 is a sectional view of a roller unit formed as a belt tensioner according to the present invention.

The belt tensioner unit comprises a pulley 10, a roller bearing 12, a screw 14 and holding means for holding the screw 14 in the pre-assembled state of the belt tensioner unit.

The holding means is formed as an elastic ring 16 which is in direct contact with the inner wall of the central hole 20 of the inner ring 18 of the bearing 12 , the threaded portion 22 of the screw 14 and the tapered portion 26 of the screw 14 . The diameter of the conical portion 26 is greater than the diameter of the threaded portion 22 of the screw 14 and increases from the conical portion 22 to a cylindrical centering portion 28 having an inner diameter substantially equal to that of the central hole 20 diameter.

The elastic ring 16 is arranged completely within the axial range covered by the inner ring 18 of the bearing 12 , ie does not extend beyond the axial end face of the inner ring 18 . The belt tensioner unit is configured to be mounted to the motor mount or transmission case (not shown) of the vehicle using screws 14 . In the mounted state, the inner ring 18 of the bearing 12 is clamped between the base plate of the head of the screw 14 and the housing.

In the mounted configuration, the axial end faces of the inner ring 18 serve as contact surfaces for transmitting the clamping force and aligning the unit. The arrangement of the elastic ring 16 within the axial extension of the inner ring 18 avoids any interference of the elastic ring 16 with the contact surfaces, ensuring this fixation.

One of the advantages of the present invention is that the screw 14 is of a cost-effective standard type, ie the screw 14 has a shaft without undercut portions.

Similarly, the bearing 12 is of the standard type, ie the central bore 20 of the inner ring 18 of the bearing 12 has a simple cylindrical inner surface.

The resilient ring 16 is radially compressed by the inner surface of the central bore 20 of the inner ring 18, thereby establishing a press-fit engagement therebetween.

In the uncompressed configuration of the elastic ring 16, the inner diameter of the elastic ring 16 is larger than the outer diameter of the threaded portion 22 of the screw 14, so that no external force is required to fit the uncompressed ring 16 onto the threaded portion 22. Meanwhile, as shown in FIG. 1, when the elastic ring is compressed by the inner ring 18 and installed in the belt tensioner unit, the inner diameter of the elastic ring 16 abuts against the threaded portion 22 and the tapered portion 26 of the screw 14 by contact force .

In an alternative embodiment of the invention, the elastic ring 16 is integrally molded with the inner ring 18 . This reduces the number of parts and enables synergies to be exploited when the pulley 10 is also joined to the outer ring of the bearing 12 by overmolding, especially when the elastic ring 16 and the pulley 10 are produced in the same injection molding process.

2a to 2c are schematic diagrams of a first assembly process of the belt tensioner unit shown in FIG. 1 . For clarity, the conical portion 26 of the screw 14 is not shown. It is entirely possible with the invention to use screws 14 which are not provided with conical portions.

First, the screw 14 is freely inserted into the bore of the inner ring 18 of the bearing 12 . The elastic ring 16 is then fitted onto the threaded portion 22 of the screw 14 until it abuts against the axial end face of the inner ring 18 (Fig. 2a). Since the inner diameter of the elastic ring 16 in an uncompressed state is larger than the outer diameter of the threaded portion 22 of the screw 14 , the elastic ring 16 can be easily fitted onto the screw 14 .

Next, the elastic ring 16 is compressed radially inwards by means of a suitable compression tool 24 ( FIG. 2 b ) and then pressed axially into the central bore 20 of the inner ring 18 while being guided by the inner surface of the tool 24 . Compression tool 24 preferably includes multiple sections that are movable radially inwardly. Alternatively suitable clamps can be used.

The axial transfer force required to press the elastic ring 16 into the space between the screw 14 and the ring 18 can be generated by another tool (not shown) having an annular pressing surface.

When the elastic ring 16 is fully inserted into the space between the screw 14 and the inner ring 18, the radially inner surface maintains a compressive force on the ring 16 and the tool can be removed (Fig. 2c). This sequence of radial compression and axial displacement constitutes the step of radially compressing the elastic ring 16 in order to fit the elastic ring 16 into the central hole 20 of the inner ring 18 of the bearing 12 . The step of radially compressing the elastic ring 16 is performed when the screw 14 is placed in the central hole 20 of the inner ring 18 .

The elastic ring 16 is optionally provided with a chamfered radially outer edge, thereby facilitating the ring fit into the inner ring 18, possibly even without the need for tools to generate radial compressive forces. A further chamfer can optionally be provided on the radially inner edge of the elastic ring 16 to adapt the shape of the cone 26 of the screw 14 .

During compression of the elastic ring 16 , as a result of the radial compression, the inner diameter of the elastic ring 16 decreases until it abuts the radially outer surface of the threaded portion 22 of the screw 14 . Further compression results in a contact force by which the inner diameter of the elastic ring 16 pushes against the thread, thereby moving the elastic ring 16 axially against strong frictional forces. The material of the inner ring 18 is selected such that this axial movement does not lead to significant material fragmentation, such that a reduction in contact force or the like occurs. The material can be rubber or plastic, for example.

3a to 3c are schematic diagrams of a second assembly process of the belt tensioner unit according to FIG. 1 . According to the second assembly process, the elastic ring 16 is first fitted onto the screw (fig. 3a), then the bearing with the pulley (not shown) and the inner ring 18 is fitted onto the screw 14, or the screw 14 with the elastic ring 16 is inserted into the central hole 20 until the elastic ring 16 adjoins the axial end face of the inner ring 18 ( FIG. 3 b ). The inner ring 18 is then radially compressed by a suitable tool 24 and pushed into the central bore 20 of the inner ring 18 . Preferably, the axial thickness of the tool 24 is less than the thickness of the elastic ring 16 .

Claims (12)

1. a roller unit, comprise roller bearing (12), screw (14) and for screw (14) being remained on the holding device under the pre-assembled state of roller unit, it is characterized in that, described holding device is formed as elastic ring (16), the center hole (20) of inner ring (18) of itself and bearing (12) and a part (22 for screw (14), 26) directly contact, the diameter of a part for described screw (14) is at least equally large with the diameter of the described helical thread portion (22) of described screw (14).

2. roller unit according to claim 1, is characterized in that, described elastic ring (16) is arranged within the axis extension of the inner ring (18) of bearing (12) completely.

3. according to the roller unit wherein described in of aforementioned claim, it is characterized in that, described screw (14) has bar portion, and the minimum diameter in described bar portion is greater than the diameter of the described helical thread portion (22) of described screw (14).

4. according to the roller unit wherein described in of aforementioned claim, it is characterized in that, the center hole (20) of the described inner ring (18) of described bearing (12) has simple cylindrical form interior surface.

5. according to the roller unit wherein described in of aforementioned claim, it is characterized in that, described elastic ring (16) is compressed by the inner surface radial direction of center hole (20).

6. roller unit according to claim 5, it is characterized in that, under described elastic ring (16) uncompressed state, the internal diameter of described elastic ring (16) is greater than the external diameter of the helical thread portion (22) of described screw (14), and when described elastic ring (16) is arranged in roller unit, the internal diameter of described elastic ring (16) is resisted against on the described helical thread portion (22) of described screw (14) by contact force.

7. according to the roller unit wherein described in of Claims 1-4, it is characterized in that, described elastic ring (16) is Unitarily molded with described inner ring (18).

8. according to the roller unit wherein described in of aforementioned claim, it is characterized in that, described roller unit comprises the pulley (10) of the outer shroud being attached to bearing (12).

9. the roller unit according to claim 7 and 8, is characterized in that, described elastic ring (16) manufactures in identical injection-molded process with pulley (10).

10. for the manufacture of the method for the roller unit wherein described according to claim 1 to 6, it is characterized in that, the method comprises radially pressure elasticity ring (16) to make elastic ring (16) be coupled to step in the center hole (20) of the inner ring (18) of bearing (12).

11. methods according to claim 10, it is characterized in that, described elastic ring (16) is being compressed and on the helical thread portion (22) being assemblied in described screw (14) before being coupled in the center hole (20) of described inner ring (18).

12. methods according to claim 10, it is characterized in that, when described screw (14) is arranged in the center hole (20) of described inner ring (18), perform the step radially compressing described elastic ring (16).