DAMPER APPARATUS HAVING A PLUG-ON SENSOR ELEMENT AND METHOD
FOR MOUNTING THE SENSOR ELEMENT
The invention relates to a damper apparatus having the features specified in the preamble of claim 1. The invention further relates to a method for mounting a sensor element on a damper tube of the damper apparatus.
In the automotive field in particular, vibration dampers are usually used in combination with a suspension in the chassis of a vehicle. Such vibration dampers are usually
formed by two damper parts which are movable relative to each other and are hydraulically or pneumatically damped relative to each other. It is known to use a linear
sensor system on the vibration damper in order to detect a relative position of the two
damper parts, in order, for example, to detect the current state of a wheel or axle suspension of the vehicle.
Document EP 0 486 848 A1 discloses a sensor in a vibration damper for a motor vehicle for measuring the relative speed and/or the position between a damper cylinder
and a damper piston of a vibration damper, the damper piston being connected to a
piston rod and moving in the damper cylinder, the sensor consisting of a permanent
magnet and a sensor winding which is in the form of a cylindrical coil, interacts with
the permanent magnet and has connections arranged at the ends, the sensor winding being designed as one piece and such that an elevated induced voltage becomes
tappable separately at a short winding portion at each of the ends of the sensor winding, wherein the permanent magnet is connected to the damper cylinder and the sensor winding is arranged on the inner wall of a cover which is connected to the piston
rod.
The problem addressed by the invention is that of providing a damper apparatus of
the aforementioned type, which is characterized by simplified mounting.
This problem is solved according to the invention by a damper apparatus having the
features specified in claim 1 and by a method having the features specified in claim
15. Advantageous embodiments result from the dependent claims, the drawings
and/or the description.
2

The invention relates to a damper apparatus which is designed and/or suitable, in
particular, for damping vibrations. The damper apparatus can be in the form, for example, of a hydraulic damper or a gas pressure damper. In particular, the damper apparatus can be designed and/or suitable for a chassis of a vehicle.
The damper apparatus has a damper tube and a piston rod, wherein the piston rod is
movably guided in the damper tube in an axial direction with respect to a longitudinal
axis. The damper tube can be delimited in an axial direction by a damper base on
one side and by a damper cap on the other side, wherein the piston rod is guided
through the damper cap. The end of the piston rod is preferably connected to a piston which is guided within the damper tube and the damper tube is subdivided into at
least two working spaces. In particular, the piston rod is linearly guided in an axial direction and is accommodated in the damper tube so as to be rotatable about the longitudinal axis. Preferably, the damper tube has a first connecting portion at the end
and the piston rod has a second connecting portion at the end. The two connecting
portions each form a bearing eye, into which, for example, a joint can be mounted.
The damper apparatus has a protective tube. In particular, the protective tube is used
to shield the damper cap, in particular the inlet point of the piston rod, such that the
interior of the damper apparatus is protected against contamination such as, for example, dust. The protective tube is movement-coupled to the piston rod such that the
protective tube is carried along when the piston rod moves and/or is moved relative
to the damper tube. The protective tube surrounds, or encases, the piston rod. In particular, the protective tube encases the longitudinal portion of the piston rod that is located outside the damper tube. Preferably, the protective tube is configured to be
open in an axial direction at one end and is pushed over the damper tube. For example, the protective tube can be in the form of a plastic tube.
Furthermore, the damper apparatus has a sensor unit which is designed and/or suitable for detecting a relative position between the damper tube and the piston rod in a
longitudinal direction. The sensor unit is preferably designed to detect a linear relative
movement between the damper tube and the protective tube along the longitudinal
3

axis and provide same as a sensor value to an evaluating unit. In particular, the sensor unit is in the form of a linear and/or inductive, preferably magneto-inductive, displacement sensor.
The sensor unit has at least or precisely one sensor element and a detection device,
which is designed and/or suitable for detecting the position of the sensor element. In
particular, the detection device is formed by an electrical detection circuit which is
preferably used to contactlessly detect the position, in particular an absolute position,
of the sensor element on the basis of a magnetic field. The sensor element is arranged on the damper tube and the detection device is arranged on the protective
tube. In particular, the sensor element, when installed, is fixed on the damper tube,
wherein the sensor element remains stationary on the damper tube during a relative
movement between the damper tube and the protective tube. Preferably, the sensor
element and the detection device together form the displacement sensor.
Within the scope of the invention, for that purpose, the sensor unit has a retaining device which is designed and/or suitable for retaining the sensor element on the
damper tube. In particular, the retaining device is used to fasten the sensor element
on the damper tube in a positionally fixed and/or play-free manner. In particular, the
retaining device is to be understood as a load-bearing retaining device, in, or on,
which the sensor element is captively accommodated. The retaining device is preferably made of plastic.
According to the invention, the retaining device is fastened on an outer circumference
of the damper tube via a plug connection. In particular, a plug connection is understood to be an interlocking and/or frictional connection which is established by means
of a plug-in movement. In particular, the retaining device is captively, preferably detachably, fixed on the damper tube via the plug connection. During mounting, the retaining device, preferably including the sensor element, is plugged on the outer circumference of the damper tube and retained on the damper tube by means of the
plug connection.
4

The advantage of the invention is, in particular, that, due to the plug connection, a
particularly simple mounting of the sensor element on the damper tube can be implemented. The sensor element can therefore be mounted using few handling steps
and, in addition, integrated, or retrofitted, into an existing damper assembly as simply
as possible. In addition, due to the plug connection, a mounting process can be implemented, which permits mounting to be carried out manually and in an automated
manner. Therefore, the mounting times can be shortened and the mounting costs can
be reduced.
According to the invention, in one specific embodiment, at least one or precisely one
fastening bolt is arranged on the damper tube. The retaining device can be captively
plugged onto the fastening bolt to form the plug connection. The fastening bolt can
be mounted on the outer circumference of the damper tube, in principle, in an interlocking manner and/or a frictional manner, for example, by means of a rivet connection or a screw connection. Preferably, however, the fastening bolt is integrally
mounted on the outer circumference of the damper tube, for example, by means of a
welded joint. In particular, the fastening bolt projects from the damper tube in a radial
direction with respect to the longitudinal axis and/or is oriented with its bolt axis transversely to the longitudinal axis of the damper apparatus. Preferably, the fastening
bolt is in the form of a cylindrical bolt. A retaining device is therefore provided, which
is characterized by a simple structural configuration and which can be mounted on
the damper tube in a particularly simple manner.
According to the invention, in a further specific embodiment, the retaining device has
at least one or precisely one fastening portion. The fastening portion is mounted on
the fastening bolt in an axially fixed manner in an axial direction with respect to the
bolt axis of the fastening bolt. In particular, the fastening portion is mounted, or can
be mounted, on the fastening bolt in an interlocking and/or frictional manner via the
plug connection at least in an axial direction with respect to the bolt axis. The fastening portion preferably has a receiving opening, in particular a through-hole,
through which the fastening bolt is guided, in particular pushed, in an axial direction
with respect to the bolt axis. For the sake of simplicity, the fastening portion is consid5

ered to be in the form of a tab. A retaining device is therefore provided, which is characterized by a compact and low-cost configuration and which can be mounted on the
fastening bolt in a particularly simple manner.

According to the invention, in one concretization, the fastening portion has at least
one or precisely one spring means for forming, or concurrently forming, the plug connection.The at least one spring means is supported against the fastening bolt in an
interlocking and/or frictional manner for axially and/or radially securing the retaining
device with respect to the bolt axis. In particular, the at least one spring means is resiliently deformable in a radial direction with respect to the bolt axis and/or is supported against the fastening bolt in a spring-loaded manner. In principle, the fastening bolt can have a latching contour, for example, a circumferential groove, into
which the spring means can latch, in order to form an interlocking connection in an
axial direction. Alternatively, the spring means rests against the fastening bolt in a radial direction with a preload, in a force-locking, in particular frictional, manner, in order to form a frictional connection in an axial direction. In particular, the at least one
spring means is arranged within the receiving opening of the fastening portion. In
particular, the at least one spring means and the fastening portion are made of a single material section, for example, of a single plastic injection-molded part. The fastening portion has, in particular, more than two, preferably more than four, in particular more than six spring means, which are supported against the fastening bolt, being
uniformly distributed around the fastening bolt. The invention therefore relates to a
fastening portion, which is characterized by a secure fastening on the fastening bolt
and by a simple formation of the plug connection.
According to the invention, in a specific structural implementation, at least one, preferably all spring means are in the form of a snap-in hook. In particular, snap-in hooks
have, on the joint side, a run-on surface, via which the snap-in hooks approach a
joining partner (fastening bolt) during mounting and, as a result, are resiliently deformed, with formation of the preload. The snap-in hook can, traditionally, subsequently latch together with the joining partner (latching contour) or, alternatively, form
a frictional connection with the joining partner, the preload being applied. A retaining
device is therefore provided, which is characterized by simplified mounting.
6

According to the invention, in an alternative or optionally supplementary concretization, the retaining device has a self-locking securing element. The securing element
can be plugged onto the fastening bolt in an axial direction with respect to the bolt
axis and inhibited in an opposite axial direction, or self-locking is implemented by the
securing element in the axial opposite direction. This means that the securing element, when mounted, generates a force, in particular a friction or clamping force, on
the fastening bolt, which prevents relative movement between the fastening bolt and
the retaining device in the axial opposite direction. In principle, the securing element,
after mounting, can be plugged onto the fastening bolt in order to secure the fastening portion against detachment in the axial opposite direction. Preferably, the securing element is integrated into the retaining device, preferably the fastening portion,
in order to form, or concurrently form, the plug connection.The invention therefore relates to a retaining device, which is characterized by a particularly secure, in particular inseparable, mounting on the fastening bolt.
According to the invention, in a specific structural implementation, the self-locking securing element is in the form of a toothed ring. In particular, toothed rings have multiple radially inwardly directed teeth which, during mounting on a cylindrical joining
partner (fastening bolt), are deflected and engage circumferentially on the joining
partner, such that a self-locking latching, or clamping, is achieved.The invention
therefore relates to a retaining device, which cannot be removed from the fastening
bolt in an axial direction, or only by applying a very large amount of force.
According to the invention, in one specific implementation, the fastening portion has
a seat for the securing element. The securing element is accommodated in the seat
without play, at least in a radial direction with respect to the bolt axis. In particular, the
seat is formed by an annular groove or a recess, preferably a counterbore or a countersink. Preferably, the receiving opening has the seat and/or directly adjoins the seat
in an axial direction. The securing element, in particular the toothed ring, is preferably
accommodated in the seat in a radial and/or axial direction in an interlocking manner
and/or coaxially to the bolt axis. The invention therefore relates to a retaining device,
which is characterized by a compact configuration and a simple integration of the securing ring in the retaining device.
7

According to the invention, in one development, the retaining device has a cover element. The cover element is interlockingly mounted on the fastening portion in an axial
direction with respect to the bolt axis in order to secure the securing element in the
seat in an axial direction with respect to the bolt axis. In particular, the cover element
is designed to cover the securing element at least partially or in sections, such that
the securing element is fixed in an axial direction by the seat and in an axial opposite
direction by the cover element. Preferably, the cover element can be pushed onto the
fastening portion, in particular in a radial direction. For this purpose, the fastening
portion can have a collar on the edge, the cover element engaging around the collar.
It is particularly preferred when the retaining device, the securing element and the
cover element jointly form a preassembled component. The cover element optionally
has a passage opening which, when the cover element is installed, is arranged coaxially and/or concentrically with respect to the receiving opening and/or the fastening
bolt. In particular, when the retaining device is installed, the fastening bolt is guided
at least in sections through the passage opening, such that the cover element is secured against detachment, in particular against being removed, by the fastening bolt.
Optionally, the cover element can be mountable on the fastening portion only when
the securing element has been inserted in the seat in the correct position. The invention therefore relates to a retaining device, which is characterized by a particularly secure seat of the securing element and, simultaneously, by a high degree of mounting
security.
According to the invention, in a further specific embodiment, at least one or precisely
one further fastening bolt is arranged on the damper tube. The retaining device can
be plugged onto the further fastening bolt in a rotationally fixed manner to form the
plug connection. In other words, the retaining device is fixed on the one fastening bolt
in an axial and radial direction by the one fastening portion and secured against rotation on the other fastening bolt by the other fastening portion. In particular, the one
fastening portion therefore forms a type of fixed mounting and the other fastening
portion forms a type of floating mounting. Preferably, the further fastening bolt is offset, or spaced apart, from the fastening bolt in an axial direction with respect to the
longitudinal axis. The further fastening bolt is identical, or structurally identical, to the
fastening bolt, as described above, and/or is mounted on the outer circumference of
8

the damper tube in the same way. The invention therefore relates to a retaining device, which is mounted in a rotationally fixed manner with respect to the damper tube
and, therefore, allows the sensor element to be mounted on the damper tube without
play. In addition, tolerances can be compensated for in a simple way.
According to the invention, in a further specific embodiment, the retaining device has
a further fastening portion. The further fastening portion is mounted on the further
fastening bolt in a radially fixed manner at least or precisely in a radial direction with
respect to a further bolt axis. In particular, the radial direction is to be understood as a
radial direction which is directed transversely to the longitudinal axis. Preferably, the
further fastening portion is mounted, or can be mounted, on the further fastening bolt
in an interlocking and/or frictional manner via the plug connection at least in the one
radial direction with respect to the further bolt axis. The further fastening portion preferably has a further receiving opening, in particular a further through-hole, through
which the further fastening bolt is guided, in particular pushed, in an axial direction
with respect to the further bolt axis. For the sake of simplicity, the further fastening
portion is considered to be in the form of a further tab. In particular, the retaining device has precisely the two fastening portions, which extend on either side of the retaining device in an axial direction with respect to the longitudinal axis. The invention
therefore relates to a retaining device, which is characterized by improved fastening
and a simple and low-cost configuration.
According to the invention, in a further concretization, the further fastening portion
has at least one or precisely one further spring means for forming, or concurrently
forming, the plug connection.The further spring means is supported against the further fastening bolt in an interlocking and/or frictional manner for axially and/or radially
securing the retaining device with respect to the further bolt axis. In particular, the at
least one further spring means is resiliently deformable in the radial direction with respect to the further bolt axis and/or is supported against the further fastening bolt in a
spring-loaded manner, in particular without play. Preferably, the further fastening portion has two further spring means, wherein the two further spring means, which are
positioned opposite one another, are supported against the further fastening bolt in
the radial direction. The further fastening bolt is therefore preferably arranged between the two further spring means in the radial direction in an interlocking and/or
9

frictional manner. In particular, the at least one further spring means is arranged
within the further receiving opening of the further fastening portion. In particular, the
at least one further spring means and the further fastening portion are made of a single material section, for example, of a single plastic injection-molded part. Optionally,
the further spring means can secure the retaining device on the further fastening bolt
in an axial direction with respect to the further bolt axis while forming an interlocking
and/or frictional connection and/or a self-locking. The invention therefore relates to a
retaining device, which is characterized by a particularly secure and play-free fastening on the fastening bolt.
According to the invention, in a further structural implementation, the retaining device
has a receiving portion, which is designed and/or suitable for receiving the sensor element. The sensor element is accommodated in the receiving portion in a captive
and/or positionally fixed manner. In particular, the sensor element is accommodated
in the receiving portion in an interlocking and/or frictional and/or integrally bonded
manner. The receiving portion is preferably in the form of a receiving pocket, in which
the sensor element is fixed with an exact fit. Preferably, the sensor element is accommodated and/or embedded within the receiving portion in a protected manner. In particular, the sensor element is embedded in the receiving portion by means of a sealing material. The invention therefore relates to a retaining device, which is characterized by a particularly secure and protected accommodation of the sensor element.
According to the invention, in a further specific embodiment, the sensor element is in
the form of a permanent magnet and the detection device is in the form of a coil arrangement. The coil arrangement extends in an axial direction with respect to the longitudinal axis over a linear detection range. In particular, the permanent magnet generates a consistent magnetic field. The coil arrangement can have at least one transmitting coil and one receiving coil, which are arranged along the detection range. In
particular, the transmitting coil is designed to generate an electrical and/or magnetic
signal. In particular, the receiving coil is designed to detect the electrical and/or magnetic signal. The magnet operates as an inductive coupling element and, therefore,
brings about a position-dependent inductive coupling between the transmitting coil
and the receiving coil. When the transmitting coil operates, a signal results in the receiving coil, on the basis of which the position of the magnet relative to the detection
10

device can be determined. It is particularly preferred when the coils are in the form of
flat conductor structures in a level printed circuit board. The invention therefore relates to a sensor unit, which is characterized by a compact and robust design.
The invention further relates to a method for mounting a sensor element on a damper
tube of a damper apparatus, as described above, in which the retaining device, including the sensor element, is fastened on an outer circumference of the damper
tube using a plug-in movement to form the plug connection. In particular, in a first
mounting step, the at least one fastening bolt, preferably the two fastening bolts,
is/are mounted on the outer circumference of the damper tube. Thereafter, the preassembled retaining device is mounted by plugging (plug-in movement) the retaining
device onto the fastening bolt. The invention therefore relates to a mounting process,
which is characterized by fast and low-cost mounting.
Further features, advantages, and effects of the invention result from the following
description of preferred exemplary embodiments of the invention, wherein:
FIG. 1 shows a schematic view of a damper apparatus as one exemplary
embodiment of the invention;
FIG. 2 shows a perspective detailed view of the damper apparatus with a
mounted retaining device for a sensor element;
FIG. 3 shows the damper apparatus in the same view as in FIG. 2 in a first
mounted state without a retaining device;
FIG. 4 shows the retaining device in a perspective view from underneath in
a first pre-mounted state;
FIG. 5 shows the retaining device in the same view as in FIG. 4 in a second
pre-mounted state;
FIG. 6 shows a cut detailed view of a first fastening portion of the retaining
device;
11

FIG. 7 shows a further cut detailed view of the first fastening portion with a
mounted securing element;
FIG. 8 shows the first fastening portion in the same view as in FIG. 7 with an
incorrectly mounted securing element;
FIG. 9 shows a sectional view of the first fastening portion when same is
mounted on the damper apparatus;
FIG. 10 shows an axial top view of the retaining device when same is
mounted on the damper apparatus.
FIG. 1 shows a damper apparatus 1 in a schematic view as one exemplary embodiment of the invention. For example, the damper apparatus 1 is in the form of a shock
absorber for a chassis of a motor vehicle. The damper apparatus 1 can be in the
form, for example, of a hydraulic or pneumatic shock absorber.
The damper apparatus 1 has a damper tube 2 and a piston rod 3, wherein the piston
rod 3 is movably guided in the damper tube 2 in an axial direction with respect to a
longitudinal axis L. In order to attach the damper apparatus 1, in particular in the region of a wheel suspension, the damper tube 1 has a first connecting portion 4a at
the end and the piston rod 3 has a second connecting portion 4b at the end. The two
connecting portions 4a, 4b are each formed as a bearing eye, into which, for example, a joint can be inserted. In an installation situation, the two connecting portions
4a, 4b are fixed on the vehicle.
The damper apparatus 1 has a protective tube 5, which surrounds the damper tube 2
and the piston rod 3 in the circumferential direction. The protective tube 5 is used to
protect the inlet point of the piston rod 3 into the damper tube 2 against entry by foreign particles such as, for example, dirt, dust, etc.The protective tube 5 is fixedly connected to the piston rod 3 in the region of the second connecting portion 4b, such
that the protective tube 5 is carried along by the piston rod 3 in an axial direction
12

when there is a relative movement B between the piston rod 3 and the damper tube
2. For example, the protective tube 5 is in the form of a plastic tube.
The damper apparatus 1 has a sensor unit 6, which is used to detect a relative position between the damper tube 2 and the piston rod 3. The sensor unit 6 is in the form
of a linear position-measuring system, which is designed to detect an occurring relative position of the damper tube 2 and the piston rod 3 on the basis of the relative
movement B. For this purpose, the sensor unit 6 has a sensor element 7 and a detection device 8, which is designed to detect a position of the sensor element 7.
The sensor element 7 is arranged on an outer circumference of the damper tube 2
and the detection device 8 is arranged on the protective tube 5 opposite the sensor
element 7, for example, on the outside of the protective tube 5, wherein the detection
device 8 extends over a linear detection range E in an axial direction with respect to
the longitudinal axis L. The detection range E is designed such that the sensor element 7 is permanently arranged in the detection range E and is detectable by the detection device 8 during the relative movement B. Preferably, the detection range E
extends over the complete stroke of the piston rod 3.
For example, the detection is carried out using magneto-inductive detection technology. For this purpose, the sensor element 7 is in the form of a permanent magnet
which generates a permanent magnetic field. The detection device 8 is in the form of
a coil arrangement having multiple coils (not shown) extending over the detection
range E, wherein at least one of the coils is in the form of a transmitting coil and at
least one of the coils is in the form of a receiving coil. Depending on the relative position of the magnet, a position-dependent overcoupling between the transmitting coil
and the receiving coil arises, wherein the relative position of the magnet can be detected by evaluating signals from the receiving coil. For example, the coils are arranged on a printed circuit board and/or are integrated into same.
Usually, the sensor element 7 is connected to the damper tube using an adhered retainer. In this variant, the sensor element 7 is placed into a plastic retainer and subsequently encapsulated. Once the sealing compound has cured, the adhesive is applied and, thereafter, the retainer is mounted over the piston rod 3, which has been at
13

least partially removed. The invention is based on the finding that this fastening variant is not ideal with respect to mounting, since the mounting process must be as simple as possible. In particular, the step of removing the piston rod 3 and the step of
adhering were identified as costly mounting steps.
The object, therefore, is to find a structural approach to fastening the sensor element
7, which is as simple as possible and can be implemented using few handling steps,
and which can be integrated into the existing damper assembly as simply as possible. In addition, a fastening is to be found, which can be handled both within the
scope of manual installation and within the scope of automated installation.
FIG. 2 shows the sensor element 7 in a perspective detailed view when the sensor
element 7 is mounted on the outer circumference of the damper tube 2. For this purpose, the sensor unit 6 has a retaining device 9, in which the sensor element 7 is accommodated, wherein the retaining device 9 is captively mounted on the damper
tube 2 via a plug connection 10.
A first and a second fastening bolt 11a, 11b, in particular one fastening bolt and a further fastening bolt, are arranged on the damper tube 2, the fastening bolts projecting
from the damper tube 2 in a radial direction. The retaining device 9 has a first and a
second fastening portion 12a, 12b, in particular one fastening portion and a further
fastening portion, via which the retaining device 9 will be or is plugged onto the two
fastening bolts 11a, 11b using a plug-in movement S.
The first fastening portion 12a is fixed on the first fastening bolt 11a at least in an axial direction with respect to a first bolt axis A1 and the second fastening portion 12b is
fixed on the second fastening bolt 11b at least in a radial direction with respect to a
second bolt axis A2. The fastening concept therefore corresponds to a typical fixedfloating mounting. Here, the first fastening portion 12a performs the function of a fixed
mounting and the second fastening portion 12b performs the function of a floating
mounting. In other words, the retaining device 9 is retained on the damper tube 2 in a
captive manner via the first fastening portion 12a and is retained on the damper tube
2 in a rotationally fixed manner via the second fastening portion 12b.
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FIG. 3 shows, in the same view as in FIG. 2, the damper apparatus 1 with the two
fastening bolts 11a, 11b in a first mounted state. The two fastening bolts 11a, 11b are
integrally bonded, within the scope of a first mounting step, on the outer circumference of the damper tube 2 by means of a suitable welding process. The two fastening bolts 11a, 11b are spaced apart from one another in an axial direction with respect to the longitudinal axis L and their bolts axes A1, A2 are aligned in the same direction. For example, the two bolt axes A1, A1 intersect the longitudinal axis L. The
fixed-floating mounting allows for tolerance compensation in the event of a longitudinal offset of the fastening bolts 11a, 11b with respect to the longitudinal axis L.
FIGS. 4 and 5 each show the retaining device 9 with the sensor element 7 in a perspective view from underneath in different pre-mounted states. The retaining device 9
has a receiving portion 13, in which the sensor element 7 is mounted in a positionally
fixed and captive manner. For this purpose, the receiving portion 13 is in the form of
a receiving pocket, into which the sensor element 7 is inserted, within the scope of a
first pre-mounting step, from underneath in an interlocking and/or frictional manner.
Before the retaining device 9 can be mounted, the sensor element 7 is integrally
bonded, within the scope of a further pre-mounting step, with the retaining device 13
by means of a sealing material 14, as is shown in FIG. 5.
FIG. 6 shows the first fastening portion 12a of the retaining device in a perspective
sectional view along the first bolt axis A1. The first fastening portion 12a has, for
forming the plug-in connection 10, a receiving opening 15 and a seat 16, which is
concentric thereto, for a self-locking securing element 17, as is shown in FIG. 7.
The receiving opening 15 is used to receive the first fastening bolt 11a, as is shown
in FIG. 2. Within the receiving opening 15, multiple, in particular precisely four, spring
means 18 are arranged, wherein the spring means 18 is used to axially and/or radially secure the first fastening portion 12a on the first fastening bolt 11a. For this purpose, the spring means 18 extend from the seat 16 in an axial direction AR with respect to the first bolt axis A1 and are resiliently deformable in a radial direction. The
spring means 18 are each in the form of a snap-in hook and, for this purpose, have,
on the end face, a run-on surface 19, via which the spring means 18 approach the
15

first fastening bolt 11a during mounting and are elastically deformed in a radial direction. Due to the use of the snap-in hooks, the retaining device 9 can be quickly installed. The spring means 18 are integrally connected to the fastening portion 12a.
FIG. 7 shows a sectional view along the first bolt axis A1 of the first fastening portion
12a with the self-locking securing element 17 in a further pre-mounted state. The securing element 17 is in the form of a toothed ring, which is also referred to as an axial
clamp ring, wherein the securing element 17 is used to secure the axial position of
the first fastening portion 12a on the first fastening bolt 11a. For this purpose, the securing element 17 has multiple radially inwardly directed teeth 20, which are designed such that the securing element 17 is mountable on the first fastening bolt 11a
in the axial direction AR and brings about a self-locking, or clamping, on the first fastening bolt 11a in an axial opposite direction GR.
The securing element 17 is inserted into the seat 16 in the axial direction AR within
the scope of a third pre-mounting step, the securing element 17 being accommodated in the seat 16 with an exact fit, or without play, in a radial direction with respect
to the first bolt axis A1. For this purpose, the seat 16 has a circumferential, inclined
surface 21, in particular a bevel, against which the securing element 17 is circumferentially supported. Once the securing element 17 has been inserted, a cover element
22 is installed in a fourth pre-mounting step, as is shown in FIG. 8. Thereafter, in a
further mounting step, the preassembled retaining device 9 is mounted by being
plugged onto the welded-on fastening bolts 11a, 11b, as is shown, for example, in
FIG. 2.
FIG. 8 shows, in the same view as FIG. 7, the fastening portion 12a with the securing
element 17 and the cover element 22 in the fourth pre-mounting step. For this purpose, the cover element 22 is pushed onto the first fastening portion 12a in a transverse direction Q which is directed transversely to the first bolt axis A1. The first fastening portion 12a has a circumferential collar 23. When the cover element 22 is installed, the cover element 22 engages around the circumferential collar 23. The cover
element 22 can be installed only when the securing element 17 has been correctly
placed into the seat 16. As is shown in FIG. 8, the securing element 17 has not been
16

correctly placed into the seat 16, wherein, due to the inclined surface 21, the securing element 17 forms an overhang, which blocks the cover element 22 from being
pushed on in the transverse direction Q. The invention therefore relates to a retaining
device 9, which is characterized by a high degree of mounting security.
FIG. 9 shows a sectional view of the first fastening portion 12a when the retaining device 9 is mounted on the damper tube 2. The first fastening portion 12a is retained on
the first fastening bolt 11a via the spring means 18 and via the securing element 17
in an axial direction and in a radial direction with respect to the first bolt axis A1.
When mounted, the securing element 17 brings about a clamping, which prevents the
retaining device 9 from being removed in the axial opposite direction GR. The spring
means 18 is circumferentially supported against the first fastening bolt 11a in a radial
direction with application of a preload force, such that the first fastening portion 12a is
centered on the first fastening bolt 11a via the spring means 18. In addition, a frictional connection is formed in a contact region between the spring means 18 and the
fastening bolt 11a, which frictional connection additionally secures the first fastening
portion 11a in an axial direction.
The cover element 22 is used to secure the position of the securing ring 17 by blocking the sole remaining degree of freedom in the axial opposite direction GR and is
used as a counter-holder for the securing ring 17 while the retaining device 9 is being
mounted on the damper tube 2. The cover element 22 additionally has a central passage opening 24, in which the first fastening bolt 11a is accommodated at least in
sections on the damper tube 2 when the retaining device 9 is mounted. The first fastening bolt 11a therefore secures the cover element 22 against removal.
FIG. 10 shows the retaining device 9 in an axial view with respect to the bolt axes A1,
A2 when same is mounted on the damper tube 2. The second fastening portion 12b
has a further receiving opening 25 for forming the plug connection 10, which receiving opening 25 is used to receive the second fastening bolt 11b. Within the further receiving opening 25, multiple, in particular precisely two, spring means 26 are arranged, which are used at least to radially secure the second fastening portion 12b
on the second fastening bolt 11b. For this purpose, the further spring means 26 extend in the axial opposite direction GR with respect to the second bolt axis A2 as is
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shown, for example, in FIG. 2, and are resiliently deformable in a radial direction. For
this purpose, the further spring means 26 are circumferentially supported against the
second fastening bolt 11b in precisely one radial direction R with application of a preload force, such that the second fastening portion 12b is centered on the second fastening bolt 11b in the radial direction R by means of the further spring means 26. The
radial direction R is to be understood as a radial direction with respect to the second
bolt axis A2, which is oriented transversely to the longitudinal axis L. The further
spring means 26 are integrally connected to the second fastening portion 12b. By
means of the second fastening portion 12b, the retaining device 9 is therefore secured against rotation about the first bolt axis A1, wherein, simultaneously, tolerances
can be compensated for in an axial direction with respect to the longitudinal axis L by
means of slight axial play.
The invention therefore relates to a retaining device 9, which is mounted on the
damper tube 2 without adhesive bonding. In addition, due to the simple structural
configuration, few handling steps are needed during the mounting process, which
significantly reduces the assembly costs, in particular when there is a high degree of
automation. In addition, due to the few handling steps, the mounting can also be carried out manually from an economic perspective. A further advantage is that the
damper apparatus 1 does not need to be removed in order to install the retaining device 9.
18

Reference characters
1 damper apparatus
2 damper tube
3 piston rod
4a, b connecting portions
5 protective tube
6 sensor unit
7 sensor element
8 detection device
9 retaining device
10 plug connection
11a, b fastening bolts
12a, b fastening portions
13 receiving portion
14 sealing material
15 receiving opening
16 seat
17 securing element
18 spring means
19 run-on surface
20 teeth
21 inclined surface
22 cover element
23 collar
24 passage opening
25 further receiving opening
26 further spring means
A1 first bolt axis
A2 second bolt axis
AR axial direction
AG axial opposite direction
B relative movement
19

E detection range
L longitudinal axis
Q transverse direction
R radial direction
s plug-in movement
20

We Claim:
1. A damper apparatus (1),
with a damper tube (2),
with a piston rod (3), wherein the piston rod (3) is movably guided in the damper tube
(2) in an axial direction with respect to a longitudinal axis (L),
with a protective tube (5), wherein the protective tube (5) is movement-coupled to the
piston rod (3) and surrounds at least the piston rod (3),
with a sensor unit (6) for detecting a relative position between the damper tube (2)
and the piston rod (3) in an axial direction, wherein the sensor unit (6) has at least
one sensor element (7) and a detection device (8) for detecting the position of the
sensor element (7), wherein the sensor element (7) is arranged on the damper tube
(2) and the detection device (8) is arranged on the protective tube (5),
characterized in that
the sensor unit (6) has a retaining device (9) for retaining the sensor element (7) on
the damper tube (2), wherein the retaining device (9) is fastened on an outer circumference of the damper tube (2) via a plug connection (10).
2. The damper apparatus (1) as claimed in claim 1, characterized in that at least
one fastening bolt (11a) is arranged on the damper tube (2), wherein the retaining
device (9) is pluggable onto the fastening bolt (11a) in a captive manner to form the
plug connection (10).
3. The damper apparatus (1) as claimed in claim 2, characterized in that the retaining device (9) has at least one fastening portion (12a), wherein the fastening portion (12a) is mounted on the fastening bolt (11a) in an axially fixed manner with respect to a bolt axis (A1).
4. The damper apparatus (1) as claimed in claim 3, characterized in that the fastening portion (12a) has at least one spring means (18), wherein the spring means
(18) is supported against the fastening bolt (11a) in an interlocking and/or frictional
manner for axially and/or radially securing.
5. The damper apparatus (1) as claimed in claim 4, characterized in that the at
least one spring means (18) is in the form of a snap-in hook.
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6. The damper apparatus (1) as claimed in one of claims 2 through 5, characterized in that the retaining device (9) has a self-locking securing element (17), wherein
the securing element (17) is pluggable onto the fastening bolt (11a) in an axial direction (AR) with respect to the bolt axis (A1) and is blocked in an axial opposite direction (GR).
7. The damper apparatus (1) as claimed in claim 6, characterized in that the selflocking securing element (17) is in the form of a toothed ring.
8. The damper apparatus (1) as claimed in claim 6 or 7, characterized in that the
fastening portion (12a) has a seat (16) for the securing element (17), wherein the securing element (17) is accommodated in the seat (16) without play at least in a radial
direction with respect to the bolt axis (A1).
9. The damper apparatus (1) as claimed in one of claims 6 through 8, characterized in that the retaining device (9) has a cover element (22), wherein the cover element (22) is interlockingly mounted on the fastening portion (12a) in an axial direction
with respect to the bolt axis (A1) for axially securing the securing element (17) in the
seat (16).
10. The damper apparatus (1) as claimed in one of claims 2 through 9, characterized in that at least one further fastening bolt (11b) is arranged on the damper tube
(2), wherein the retaining device (9) is pluggable onto the further fastening bolt (11a)
in a rotationally fixed manner to form the plug connection (10).
11. The damper apparatus (1) as claimed in one of the preceding claims, characterized in that the retaining device (9) has a further fastening portion (12b), wherein
the further fastening portion (12b) is mounted on the further fastening bolt (11b) in a
radially fixed manner at least in precisely one radial direction (R) with respect to a further bolt axis (A2).
12. The damper apparatus (1) as claimed in claim 11, characterized in that the further fastening portion (12b) has at least one further spring means (26), wherein the
22

further spring means (26) is supported against the further fastening bolt (11b) in an
interlocking and/or frictional manner for radial and/or axial securing.
13. The damper apparatus (1) as claimed in one of the preceding claims, characterized in that the retaining device (9) has a receiving portion (13), wherein the sensor element (7) is accommodated in the receiving portion (13) in a captive and/or positionally fixed manner.
14. The damper apparatus (1) as claimed in one of the preceding claims, characterized in that the sensor element (7) is in the form of a permanent magnet and that
the detection device (8) is in the form of a coil arrangement, wherein the coil arrangement extends over a linear detection range (E) in an axial direction with respect to the
longitudinal axis (L).
15. A method for mounting a sensor element (7) on a damper tube (2) of a damper
apparatus (1) of one of the preceding claims, in which:
- a retaining device (9) including the sensor element (7) is fastened on an outer circumference of the damper tube (2) to form a plug connection (10).