DE102016226105A1 - displacement sensor - Google Patents

Abstract

The invention relates to a displacement sensor (1) comprising a movement element (3), a coil (4) and a position transmitter (2) which is movable relative to the coil (4) and which reproduces the position of the movement element (3) in a direction of movement, wherein an inductance the coil (4) from a relative position of the position sensor (2) to the coil (4) is dependent, wherein the moving element (3) a first magnetic element (5) and the position sensor (2) has a second magnetic element (2c).

Description

The invention relates to a displacement sensor according to the preamble of claim 1 and a braking device with such a displacement sensor.

Displacement sensors are used for example in metalworking, in cranes, presses and in various areas of automotive engineering.

One possible field of application for a displacement sensor in a motor vehicle is a brake device which generates the hydraulic pressure for a brake system. For this purpose, a push rod is moved via a brake pedal, which is connected to a guided in a housing pressure piston, which acts on a hydraulic fluid with the necessary pressure. In order to detect the linear deflection of the pressure piston magnetoinductive displacement sensors are common in the first place.

A magnetoinductive displacement sensor measures the position of a permanent magnet attached to the moving element whose position is to be detected. The magnetoinductive displacement sensor is also able to measure through non-ferromagnetic materials, in particular through metals such as aluminum and stainless steel. In closed or enclosed systems, as in the case of a braking device, this is particularly advantageous because the permanent magnet and the sensing element can be accommodated spatially separated. However, magneto-inductive displacement sensors have the disadvantage that they are extremely sensitive to magnetic interference fields. To avert this is a complex shielding or a cost and space-consuming construction of the displacement sensor necessary.

By contrast, a purely inductive displacement sensor is based on the fact that a conductive body is moved in a magnetic field so that eddy currents occur in it. For example, a path measurement can be carried out via the quality change of a resonant flywheel thus effected. For use in a closed system whose walls are electrically conductive, this is a great disadvantage, since the distance measurement through the walls is not possible. A mechanical construction, which connects the conductive body with the moving element, whose position is to be detected, however, is very complex and requires a lot of space.

The invention has for its object to propose an insensitive and / or compact and / or inexpensive displacement sensor.

This object is achieved by the displacement sensor according to claim 1.

The displacement sensor according to the invention is in particular relatively insensitive to external interference and requires little space.

Advantageous embodiments of the invention are the subject of the dependent claims.

The term displacement sensor preferably designates a sensor which detects a position and / or a deflection and / or a position and / or a distance. Preferably, an output signal is generated from the detected quantity with a signal processing circuit. In addition, a displacement sensor may be configured to additionally detect a speed and / or an acceleration.

For the purposes of the invention, a moving element is preferably understood as meaning a movably mounted body, preferably a solid body, such as a pressure piston. Particularly preferably, the moving element is mounted so that it is linearly movable.

In the context of the invention, a magnetic element is understood to mean a body which magnetically attracts or repels other bodies, for example a permanent magnet or an electromagnet.

In a preferred embodiment, the position sensor is mechanically decoupled from the movement element. The position sensor and the movement element are therefore not mechanically connected in terms of separate components. This has the advantage that no space-demanding mechanical design is necessary.

It is expedient that the first and the second magnetic element are arranged and / or configured with respect to one another such that the movement and / or position of the position sensor is magnetically coupled to the movement of the movement element. As a result of the coupled movements, a distance traveled by the position transmitter corresponds to a distance traveled by the movement element. In other words, the position transmitter is carried along by the movement element in its movement due to the magnetic coupling of the magnetic elements. In this way, the position encoder accurately reflects the position of the moving element.

It is preferred that the position sensor is separated from the movement element by a wall, in particular a wall made of a non-ferromagnetic material, in particular spatially separated. By a non-ferromagnetic wall, the magnetic interaction of the first and second magnetic element hardly affected. At the same time, however, the wall protects the locator and electronic components from contamination.

Preferably, the first magnetic element and / or the second magnetic element is a permanent magnet. The effort in the production and operation of the displacement sensor can thus be kept low.

Preferred is an embodiment in which the first magnetic element is pressed into the movement element or pressed onto the movement element, screwed or glued. This ensures a secure hold of the first magnetic element.

Preferably, the displacement sensor according to the invention is further developed such that the first magnetic element has a ring shape or a disk shape. This has the advantage that the first magnetic element can combine a strong magnetic field with a compact design.

It is preferred that the coil is electrically connected to a circuit for detecting the inductance and for outputting a signal dependent on the inductance of the coil, in particular a displacement sensor output signal. Such a circuit can be realized easily and inexpensively.

Preferably, the position sensor is mounted in a plain bearing. In order to ensure a secure storage, in which the forces to be applied to the movement of the position sensor are kept low, such a bearing is advantageous and particularly inexpensive.

According to a further preferred embodiment of the invention, the position sensor is mounted in a rolling bearing. The applied to the movement of the position sensor forces are kept particularly low in such a camp, which allows economical dimensioning of the magnetic elements.

It is preferable that the coil is a planar coil. Such a coil can be integrated particularly space-saving. A planar coil is preferably understood to mean a coil which has an extension in the direction of movement of the position sensor or of the movement element which is greater than at least one of the corresponding other two spatial directions, in particular greater than the extent perpendicular thereto in the direction of the movement plane of the position sensor.

Preferably, the position sensor comprises an electrically conductive body, in particular a metal sheet, in particular a target. The target, also called the donor element, forms the element to be sensed and, with its effect on the coil, directly paves the way. This makes it possible to perform a distance detection precisely and reliably. In the direction of movement of the position transmitter or of the movement element, the target preferably has an extent which is greater than at least one of the corresponding other two spatial directions, in particular greater than the extent perpendicular thereto in the direction of the movement plane of the position sensor. Particularly preferably, the largest dimension of the target corresponds to the greatest extent of the coil.

Preferably, the coil and the target at least partially overlap in the direction of movement. By overlapping the coil and the target, the displacement sensor can be realized not only in the smallest space, it can also achieve more precise measurement results, since the sensitivity of the displacement sensor increases, the closer the target is arranged on the coil.

Preferably, insulation is between the coil and the target. The insulation prevents a short circuit of the elements of the displacement sensor and thus undefined measurement states.

It is preferred that the maximum possible path of the position sensor in the direction of movement corresponds to the maximum possible path of the movement element. In this way, the entire maximum travel of the movement element can be detected. The maximum travel is preferably understood to mean, in each case, the path defined by structural limitations, for example walls, also called a stroke, along which the moving object, in this case the position transmitter or the movement element, can move.

The invention also relates in particular to a brake device for generating a hydraulic pressure for a brake system, comprising a housing with a hydraulic fluid and a displacement sensor according to the invention, wherein the movement element is formed by a guided in the housing pressure piston, in particular tandem master cylinder. Due to the high pressure and the risk of contamination in a brake device, it is advantageous if all components of a displacement sensor are arranged outside this range. The displacement sensor according to the invention allows such an arrangement and is compact and insensitive to interference.

In one embodiment of the invention, the position sensor of the displacement sensor is formed on an outer side of the housing viewed from the pressure piston. This has the advantage that the position sensor can be arranged close to the coil.

• 1 eine Darstellung eines Wegsensors nach einem ersten Ausführungsbeispiel als Teil einer Bremsvorrichtung in einer Schnittansicht;
• 2 eine Darstellung des Positionsgebers des ersten Ausführungsbeispiels in einer Schnittansicht;
• 3 eine Darstellung eines Positionsgebers nach einem zweiten Ausführungsbeispiel in einer Schnittansicht;

Embodiments of the invention will be explained in more detail with reference to drawings. In a schematic representation:

• 1 a representation of a displacement sensor according to a first embodiment as part of a braking device in a sectional view;
• 2 a representation of the position sensor of the first embodiment in a sectional view;
• 3 an illustration of a position sensor according to a second embodiment in a sectional view;

Identical parts are provided with the same reference numerals in all figures.

It will open 1 Reference is made to a braking device 100 with a displacement sensor according to the invention 1 shows. The brake device 100 has a housing 101 in which a pressure piston 103 is linearly movable in a recess of the housing 105 is stored. The pressure piston 103 is designed as a tandem master cylinder. Accordingly it forms with the housing 101 two separate chambers 104 each containing hydraulic fluid and forming part of a dual-circuit brake system with two independent circuits. The pressure piston is actuated 103 with the help of a push rod 102 which is coupled to a brake pedal. By the linearly movable pressure piston 103 the force of the brake pedal is translated into a pressure of the hydraulic fluid.

The path or the linear position of the pressure piston 103 in the case 101 should be recorded. The pressure piston 103 therefore forms a moving element 3 the displacement sensor according to the invention 1 , It can be through the push rod 102 by a certain maximum distance, the stroke of the moving element 3 move linearly.

The movement element 3 has a round, disk-shaped first magnetic element 5 on, which is designed as a permanent magnet and in a recess of the moving element 3 let in and squeezed there. It is understood that the first magnetic element 5 take other forms and also in a different manner known in the art on the movement element 3 may be attached, for example by an adhesive or screw connection. Also, the movement element 3 itself be formed as the first magnetic element 5, for example by being permanently magnetized.

The wall 6 the recess of the housing 105 in which the movement element 3 is stored, consists of a non-ferromagnetic material. On the of the movement element 3 seen from another side of the wall 6 is in an electronics area 107 of the housing 101 a position transmitter 2 arranged, which is a second magnetic element 2c having. The position transmitter 2 is next to the second magnetic element 2c from a carrier 2a and for redundancy, two electrically conductive bodies 2 B , formed in this case of metallic material, each having a substantially elongated, flat shape. The second magnetic element 2c is at the non-ferromagnetic wall 6 facing side of the position sensor 2 arranged. It is designed as a permanent magnet and in the carrier 2a integrated. Other types of attachment are also useful. The second magnetic element 2c , the carrier 2a and the electrically conductive body 2 B form as position transmitter 2 a compact unit.

Due to a magnetic coupling of the second magnetic element 2c with the first magnetic element 5 This compact unit moves with the moving element 3 consistent with. It is, so to speak, magnetic to the first magnetic element 5 and thus to the movement element 3 tied up.

So that the position transmitter 2 The positional position of the movement unit exactly reproduces is the position transmitter 2 or the compact unit friction in its part of the housing 101 stored.

It will open 2 Reference is made, which shows a schematic representation of a sectional view, in addition to the plunger 103 with the first magnetic element 5 the position transmitter 2 is shown. Using the section plane labeled A - A, in which the 1 is shown, as the 2 with the 1 spatially related.

The carrier 2a of the position encoder 2 forms with the housing 101 a plain bearing 20a , This is in the case 101 a groove 106 let in, which is a corresponding counterpart of the wearer 2a linear leads. The second magnetic element 2c is included in this counterpart. Lateral characteristics of the carrier 2a Give this a T-shape and set a sliding surface 21a of the plain bearing 20a ready. On the lateral forms of the carrier 2a are the two electrically conductive bodies 2 B glued. Directly opposite the electrically conductive bodies 2b is ever a sensing element in the form of a respective coil 4 , in this case a planar coil, arranged.

The respective coil 4 is part of each circuit and causes based on that of eddy currents in the respective electrically conductive bodies 2 B triggered change in the quality of a resonant circuit, the eddy currents in the respective electrically conductive bodies 2 B is caused, the position of the position sensor 2 is detected. For this purpose, the circuit is designed in each case as LC-gate oscillator. This generates based on the inductance of the coil 4 an output signal having a frequency dependent on the inductance via a parallel flyback circuit. Alternatively, the inductance could be determined with other oscillators, such as a Meissner oscillator, or with other measuring principles, such as a detection of the impedance of the planar coil.

3 shows a schematic representation of a sectional view in the next to the pressure piston 103 with the first magnetic element 5 the position transmitter 2 is shown according to a second embodiment. The second embodiment differs from the first only by the storage described below. The storage of the carrier 2a of the position encoder 2 with the housing 101 is with the help of rolling elements 21b implemented as rolling bearings 20b. Such a rolling bearing 20b For example, it may have rollers, balls or other rolling bodies. These are rotatably mounted by means of a cage, wherein the cage on the housing 101 is attached and the carrier 2a of the position encoder 2 on the rolling elements 21b can roll. Conversely, an attachment of the cage to the carrier 2a of the position encoder 2 possible, so this unit on the housing 101 can roll. A groove 106 for guiding the position sensor 2 is not mandatory in this embodiment, but still helpful.

Claims (15)

Position sensor (1) comprising a moving element (3), a coil (4) and a position sensor (2) which is movable relative to the coil (4) and which reproduces the position of the moving element (3) in a direction of movement, wherein an inductance of the coil (4 ) is dependent on a relative position of the position sensor (2) to the coil (4), characterized in that the movement element (3) comprises a first magnetic element (5) and the position sensor (2) has a second magnetic element (2c). Distance sensor (1) to Claim 1 , characterized in that the position sensor (2) of the moving element (3) is mechanically decoupled. Displacement sensor (1) according to one of the preceding claims, characterized in that the first and the second magnetic element (5, 2c) are arranged to each other such that the movement of the position sensor (2) is magnetically coupled to the movement of the moving element (3). Displacement sensor (1) according to one of the preceding claims, characterized in that the position sensor (2) separated from the moving element (3) by a wall (6), in particular a wall (6) made of a non-ferromagnetic material, in particular spatially separated , Displacement sensor (1) according to one of the preceding claims, characterized in that the first magnetic element (5) and / or the second magnetic element (2c) is a permanent magnet. Displacement sensor (1) according to one of the preceding claims, characterized in that the first magnetic element (5) is pressed into the movement element (3) or pressed onto the movement element (3), screwed or glued. Displacement sensor (1) according to one of the preceding claims, characterized in that the first magnetic element (5) has an annular shape or a disc shape. Displacement sensor (1) according to one of the preceding claims, characterized in that the coil (4) is electrically connected to a circuit for detecting the inductance and for outputting a dependent of the inductance of the coil (4) signal, in particular Wegsensorausgangssignals. Displacement sensor (1) according to one of the preceding claims, characterized in that the position sensor (2) is mounted in a sliding bearing (20a). Distance sensor (1) according to one of Claims 1 to 8th , characterized in that the position sensor (2) is mounted in a rolling bearing (20b). Displacement sensor (1) according to one of the preceding claims, characterized in that the coil (4) is a planar coil. Displacement sensor (1) according to one of the preceding claims, characterized in that the position sensor (2) comprises an electrically conductive body (2b), in particular a metal sheet, in particular a target. Displacement sensor (1) according to one of the preceding claims, characterized in that the maximum possible path of the position sensor (2) in the direction of movement corresponds to the maximum possible travel of the movement element (3). Brake device (100) for generating a hydraulic pressure for a brake system comprising a housing (101) with a hydraulic fluid and a displacement sensor (1) according to one of the preceding claims, wherein the movement element (3) by a in the housing (101) guided pressure piston (103), in particular tandem master cylinder is formed. Braking device after Claim 14 , characterized in that the position sensor (2) of the displacement sensor (1) at one of the pressure piston (103) from seen outside of the housing (101) is formed.

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