Assembly Having Rotary Encoder and Tolerance Ring

Abstract

To provide an assembly that enables a rotary encoder to operate reliably with high measurement accuracy permanently.SOLUTION: An assembly includes a rotary encoder (1), a tolerance ring (2), and an enclosure (3) accommodating the rotary encoder and the tolerance ring (2). A housing (1.21) has an outer wall with a special geometry. The enclosure (3) has a concavity (3.1), and an inner wall (3.11) of the concavity (3.1) is also specially shaped. The tolerance ring (2) surrounds the housing (1.21). In the concavity (3.1), the tolerance ring (2) is positioned to be radially clamped.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The invention relates to an assembly comprising a rotary encoder and a tolerance ring according to claim 1 and a housing that accommodates the rotary encoder and the tolerance ring. [Background technology]

[0002] Rotary encoders are used, for example, to determine the angular position or rotational speed of two machine parts that are rotatable relative to one another. In inductive rotary encoders, the excitation conductor track and the receiving track, e.g., in the form of a conductor track, are often mounted on a common, usually multilayer, printed circuit board, which is fixedly connected, e.g., to the stator of the rotary encoder. A scale element, on which a graduation structure is provided, is located opposite the printed circuit board and is non-rotatably connected to the rotor of the rotary encoder. When a time-alternating excitation current is applied to the excitation coil, a signal dependent on the angular position is generated in the receiving coil during the relative rotation between the rotor and the stator. These signals are then further processed in the evaluation electronics.

[0003] Rotary encoders that operate on optical principles often use a light beam modulated by a rotatable disk carrying graduation structures. This modulated light is then received by a photodetector. The received light intensity contains information about the relative angular position.

[0004] Such rotary encoders are often used as measuring instruments for electric drives to determine the relative movement or relative position of corresponding machine parts, with the generated angular position values ​​being transmitted to the electronics for controlling the drive via a corresponding interface arrangement.

[0005] From US Patent Application Publication No. 2009 / 0027043 A1 a rotary encoder is known which can be attached to a further housing by means of an annular tolerance ring. Such an arrangement has the disadvantage that, during operation, conditions can arise therein that reduce the measurement quality or accuracy of the rotary encoder. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent Application Publication No. 2009 / 0027043(A1) Summary of the Invention [Problem to be solved by the invention]

[0007] The problem underlying the present invention is to provide an assembly which permanently allows reliable operation of a rotary encoder with high measurement accuracy. [Means for solving the problem]

[0008] This problem is solved according to the invention by the features of claim 1. According to the disclosure, the assembly includes a rotary encoder, a tolerance ring, and a housing that accommodates the rotary encoder and the tolerance ring. The rotary encoder has a shaft, and a scale element is fixed to the shaft so as not to rotate. The rotary encoder further has a housing, and a scanning unit is disposed within the housing, and the scanning unit is non-rotatably coupled to the housing. The shaft is disposed relative to the housing so as to be rotatable about its axis. The scale element is scannable by the scanning unit. The housing further has an outer wall, preferably formed to be closed and circumferential, that has a first radial spacing relative to the axis within a first section. The outer wall has a second radial spacing relative to the axis within a second section. It is important in this regard that the first spacing be greater than the second spacing. Additionally, the housing has a recess in which the rotary encoder and the tolerance ring are accommodated. The recess is defined radially relative to the axis by a first inner wall, and the first inner wall has a third radial spacing relative to the axis within a third section. Furthermore, the first inner wall has a fourth radial distance relative to the axis within the fourth section. The housing is formed so that the fourth distance is greater than the third distance. The recess is further defined by a second inner wall, which serves as an axial stop for the housing relative to the axis, with the fourth section being axially disposed between the second inner wall and the third section. The fourth section is axially closer to the second inner wall than the third section. The tolerance ring surrounds the housing and is disposed within the recess so as to be radially between the first and fourth sections. Similarly, in this assembled state of the assembly, the tolerance ring is also between the second and third sections, in which case the tolerance ring is radially sandwiched between the housing and the housing.

[0009] The first, second, third and fourth sections each extend in the axial direction, and in this regard the first and / or second section can be a region on the convex side of the outer cylindrical contour of the housing, while the third and / or fourth section can be a region on the concave side of the inner cylindrical contour of the recess, although the sections do not necessarily have to be closed, circumferential surfaces, but rather these surfaces can be discontinuous, in particular over the periphery.

[0010] That is, the second inner wall is oriented so that the normal vector on this inner wall has a directional component parallel to the axis. Advantageously, the assembly is formed such that the second inner wall is an axial stop for the tolerance ring.

[0011] In a further aspect of the invention, the housing has a first conical surface between the first section and the second section. Advantageously, the first inner wall has a second conical surface between the third and fourth sections.

[0012] The conical surfaces are arranged obliquely relative to the axis and can be formed as closed, continuous surfaces or as discontinuous surfaces over the circumference. Advantageously, the housing has a surrounding outer wall.

[0013] In a further aspect of the invention, the first inner wall has a circumferential inner contour. In principle, a distinction is made between rotary encoders with self-supporting bearings and rotary encoders without self-supporting bearings (hereinafter referred to as bearing-less rotary encoders). Rotary encoders with self-supporting bearings usually have relatively small ball bearings, so that the parts within the rotary encoder that can rotate relative to one another are arranged at defined axial and radial positions relative to one another. In contrast, in the case of bearing-less rotary encoders, care must be taken when mounting them on a machine to ensure that the parts that can rotate relative to one another are positioned correctly relative to one another, in particular with an appropriate axial spacing, and that this position remains unchanged during operation of the rotary encoder. The present invention is particularly advantageous in connection with bearing-less rotary encoders.

[0014] Advantageous configurations of the invention can be seen from the dependent claims. Further details and advantages of the rotary encoder according to the invention will become apparent from the following description of one exemplary embodiment based on the attached drawings. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is an exploded view of the assembly. [Figure 2] FIG. 1 is a cross-sectional view of a rotary encoder. [Figure 3] Here, it is a cross-sectional view of a housing used as a motor housing. [Figure 4] FIG. 2 is a cross-sectional view of the assembly. [Figure 5] FIG. 5 is a detailed view of the cross section based on FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0016] The invention relates to an assembly based on FIG. 1, which includes a rotary encoder 1, a tolerance ring 2 and a housing 3, for example a motor housing of an electric powertrain. According to this, the rotary encoder 1 comprises a first component group 1.1 and a second component group 1.2, which are rotatable relative to each other about an axis A. The first component group 1.1 is often used as a rotor and the second component group 1.2 as a stator.

[0017] The first component group 1.1 includes a shaft 1.11, i.e., a rotary encoder shaft. A scale element 1.12, i.e., a scale, is fixed non-rotatably to the shaft 1.11 of the rotary encoder 1. The scale element 1.12 includes a graduation, which in the illustrated exemplary embodiment is configured as an annular disk made of printed circuit board material, with the graduation arranged on its annular end surface. In the illustrated exemplary embodiment, the scale element 1.12 consists of a substrate made of epoxy resin, on which one or more graduation tracks are arranged annularly and centered relative to the axis A. Each graduation track typically consists of a periodic sequence of alternating conductive and non-conductive graduation areas.

[0018] The housing 1.21, belonging to the second component group 1.2, includes a cover 1.213 and serves to protect the interior space of the rotary encoder 1 from environmental influences. Inside the housing 1.21, a scanning unit 1.22 is located, fixed to the housing 1.21 and non-rotatably, and determines the angular position between the scanning unit 1.22 and the scale element 1.12. In the illustrated embodiment, the rotary encoder is based on the inductive scanning principle. The scanning unit 1.22 includes a multilayer printed circuit board 1.221. Two of these layers are structured to serve as receiving and excitation conductors. Furthermore, electronic components 1.222 are mounted on the printed circuit board 1.221. An electronic circuit is required for the operation of the excitation conductor and for processing the signals received by the receiving conductor. The electronic components 1.222 are the components of this circuit that power the excitation conductor and process the received signals. Additionally, an electrical coupling piece is mounted on the printed circuit board 1.221 to establish a plug connection with a mating cable connector.

[0019] In the exemplary embodiment shown, the rotary encoder 1 is configured as a bearing-free rotary encoder, i.e. no bearings, in particular ball bearings, are arranged between the first component group 1.1 and the second component group 1.2, so that the first component group 1.1 can be displaced relative to the second component group 1.2 within certain limits, in particular in the axial direction.

[0020] 2, the housing 1.21 has a convex outer wall, which has a first radial distance R1 relative to the axis A within a first section 1.211. In the exemplary embodiment shown, the first section 1.211 is formed as a cylindrical side surface. The first distance R1 can be considered as the distance between a point on the side surface and the axis A.

[0021] In other words, the outer diameter of the housing 1.21 in the first section 1.211 is twice the first spacing R1 (2 x R1). The outer wall of the housing 1.21 has a second section 1.212 axially offset relative to the first section 1.211. Within the second section 1.212, which can also be considered a cylindrical side, the outer wall of the housing 1.21 has a second radial distance r2 relative to the axis A. Since the outer diameter of the housing 1.21 in the second section 1.212 is reduced compared to the outer diameter of the housing 1.21 in the first section 1.211, it applies that the first distance R1 is greater than the second distance r2.

[0022] The assembly according to Fig. 1 further includes a tolerance ring 2. The tolerance ring 2 is mounted around the housing 1.21. As is customary, the tolerance ring 2 has an embossed groove 2.1. When properly mounted, the groove 2.1 of the tolerance ring 2 acts like a radially compressed compression spring.

[0023] Finally, the assembly includes a housing 3, which is the motor housing as mentioned above. The housing 3 has a recess 3.1, which can also be described as a hole with an undercut. According to FIG. 3, the recess 3.1 is radially bounded by a first, surrounding inner wall 3.11. This first inner wall 3.11 has a third radial spacing r3 relative to the axis A in a third section 3.113 and a fourth radial spacing R4 relative to the axis A in a fourth section 3.114. The fourth spacing R4 is greater than the third spacing r3.

[0024] The recess 3.1 is further defined by a second inner wall 3.12, which is oriented in space so that the normal vector on the surface of this wall 3.12 runs parallel to the axis A. In the illustrated exemplary embodiment, the second inner wall 3.12 is flat. The housing 3 is formed so that the fourth section 3.114 is axially disposed between the second inner wall 3.12 and the third section 3.113. The second inner wall 3.12 also has a central hole in which the motor shaft 4 can be accommodated. This hole is oversized relative to the motor shaft 4, so that the motor shaft 4 can rotate freely within the hole.

[0025] During the installation of the rotary encoder 1 in the housing 3, i.e. in the motor housing, the rotary encoder 1 together with the tolerance ring 2 is pressed into the recess 3.1 of the housing 3. The second inner wall 3.12 in this connection serves as an axial stop for the housing 1.21 and the tolerance ring 2 relative to the axis A (FIG. 4). The housing 1.21 of the rotary encoder 1 is therefore fixedly and centered in the housing 3 by the tolerance ring 2 via a press fit.

[0026] Finally, based on FIG. 4, the first component group 1.1 of the rotary encoder 1, in particular the shaft 1.11, can be screwed to the motor shaft 4, in which case the first component group 1.1 is pressed against a shoulder of the motor shaft 4 by a central screw.

[0027] The first component group 1.1 is precisely positioned axially relative to the second component group 1.2 by the bearing of the shaft 1.11 of the rotary encoder 1 against the motor shaft 4 and the bearing of the housing 1.21 against the second inner wall 3.12. Therefore, the so-called scanning distance z between the scale element 1.12 and the scanning unit 1.22 after mounting is precisely adjusted.

[0028] When the scale element 1.12 and the scanning unit 1.22 rotate relative to each other, a signal that depends on the respective angular position is generated in the scanning unit 1.22 by an inductive effect. For precise measurement of the angular position, it is important that the signal amplitude is sufficient. The height of the signal amplitude depends, among other things, on the scanning distance z. To avoid even small changes in the scanning distance z, for example when the assembly is exposed to temperature fluctuations and / or vibrations, the outer wall of the housing 1.21 and the first inner wall 3.11 of the recess are shaped accordingly.

[0029] FIG. 5 shows a detailed view D (FIG. 4) of the housing 1.21 and the housing 3. The tolerance ring 2, which surrounds the housing 1.21, is arranged in the recess 3.1 radially between the first section 1.211 and the fourth section 3.114. Similarly, the tolerance ring 2 is radially sandwiched between the second section 1.212 and the third section 3.113. The tolerance ring 2 is radially clamped by the compressed, i.e., radially crushed, groove 2.1. The housing 1.21 is designed so that a first conical surface 1.215 exists between the first section 1.211 and the second section 1.212. Furthermore, the housing 3 is designed so that the first inner wall 3.11 has a second conical surface 3.115 between the third section 3.113 and the fourth section 3.114. The tolerance ring 2 is clamped between, inter alia, the first conical surface 1.215 and the second conical surface 3.115. This configuration increases the holding force, which in turn effectively prevents the first part group 1.1 of the rotary encoder 1 from moving significantly relative to the second part group 1.2 due to temperature fluctuations or differences within the components of the assembly. An unchanging scanning distance z can therefore be guaranteed. [Explanation of symbols]

[0030] 1 rotary encoder 1.11 Shaft 1.12 Scale Elements 1.21 Housing 1.211 First Section 1.212 Second Section 1.215 First cone surface 1.22 Scanning Unit 2 Tolerance Ring 3. Housing 3.1 Recess 3.11 First Inner Wall 3.113 Third Section 3.114 Fourth Section 3.115 Second conical surface 3.12 Second Inner Wall A-axis R1 First interval r2 Second interval r3 third interval R4 Fourth interval

Claims

1. An assembly including a rotary encoder (1), a tolerance ring (2), and a housing (3) that houses the rotary encoder and the tolerance ring (2), The rotary encoder (1) - a shaft (1.11) on which a scale element (1.12) is fixed so as not to rotate, and - it has a housing (1.21) in which a scanning unit (1.22) is arranged, the scanning unit (1.22) being non-rotatably connected to the housing (1.21), the shaft (1.11) is arranged to be rotatable about an axis (A) relative to the housing (1.21), and the scale element (1.12) is scannable by the scanning unit (1.22); and The housing (1.21) has an outer wall, the outer wall having: Within the first section (1.211), a first distance (R1) relative to the axis (A), and Within the second section (1.212), it has a second spacing (r2) relative to the axis (A), The first distance (R1) is greater than the second distance (r2), and The housing (3) has a recess (3.1), and the recess (3.1) - defined radially relative to said axis (A) by a first inner wall (3.11), said first inner wall (3.11) being Within a third section (3.113), it has a third spacing (r3) relative to the axis (A), and Within a fourth section (3.114), it has a fourth distance (R4) relative to the axis (A), The fourth distance (R4) is greater than the third distance (r3), and the recess (3.1) is - defined by a second inner wall (3.12), said second inner wall (3.12) being an axial stop for said housing (1.21) with respect to said axis (A), said fourth section (3.114) being arranged axially between said second inner wall (3.12) and said third section (3.113); The tolerance ring (2) surrounds the housing (1.21) and is arranged in the recess (3.1) so that the tolerance ring (2) is radially sandwiched between the first section (1.211) and the fourth section (3.114) and between the second section (1.212) and the third section (3.113).

2. Assembly according to claim 1, wherein the second inner wall (3.12) is an axial stop for the tolerance ring (2).

3. Assembly according to claim 1, characterized in that the housing (1.21) has a first conical surface (1.215) between the first section (1.211) and the second section (1.212).

4. 2. The assembly according to claim 1, wherein the first inner wall (3.11) has a second conical surface (3.115) between the third section (3.113) and the fourth section (3.114).

5. Assembly according to claim 1, characterized in that the housing (1.21) has a surrounding outer wall.

6. Assembly according to claim 1, characterized in that the first inner wall (3.11) has a circumferential inner contour.

7. 7. The assembly according to any one of claims 1 to 6, wherein the rotary encoder (1) is formed as a bearing-less rotary encoder (1).

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