WO2015144159A1

WO2015144159A1 - Master cylinder for a hydraulic system

Info

Publication number: WO2015144159A1
Application number: PCT/DE2015/200141
Authority: WO
Inventors: Richard Dubas; Yannick Christiaens
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2014-03-24
Filing date: 2015-03-11
Publication date: 2015-10-01
Also published as: DE112015001418A5

Abstract

A master cylinder for a hydraulic system, in particular for a hydraulic clutch system or for a hydraulic brake system, has a cylinder (14) for the movable guidance of a piston (16), in which cylinder the piston (16) is guided in displaceable fashion, wherein, for determining the position of the piston (16), an inductive sensor (30) is provided adjacent to the cylinder (14) and outside the cylinder. In this case, the piston (16) is at least partially formed from a material that can be detected by the inductive sensor. In summary, a master cylinder as described above can, in a particularly simple and inexpensive manner, permit improved position determination or travel measurement of the piston in the guide sleeve.

Description

Master cylinder for a hydraulic system

The present invention relates to a master cylinder for a hydraulic system, in particular for a hydraulic clutch system or for a hydraulic brake system, which has an improved functionality.

There are master cylinder for a hydraulically actuated clutch or brake of vehicles with a housing arranged in a guide sleeve, which forms a portion of a cylinder in which a connected via a piston rod with a manually operated pedal or with an electromagnetically or hydraulically actuated actuator piston is guided axially displaceable. It may be necessary, for example, for controlling the master cylinder to determine the position of the cylinder in the guide sleeve.

For this purpose, a piston may be provided, to which a so-called target is attached, so as to enable an inductive displacement measurement of the master piston. Targets of this type can be space-consuming both axially and radially, which can be disadvantageous even in the case of limited space conditions. In addition, the target is a separate component, which extends the assembly time of the master cylinder. In addition, a suitable attachment is needed to create the smallest possible gap between the target and the inner wall of the corresponding pressure chamber. For tolerance compensation squish ribs are provided in the prior art, which are pressed. Overall, this requires more target material than is necessary for a suitable signal strength or signal quality of a path measurement. Even with squish ribs optimal centering of the target is difficult.

On this basis, it is the object of the present invention, at least partially overcome the disadvantages known from the prior art. In particular, it is the object of the invention to provide a master cylinder for a hydraulic system, in particular for a hydraulic engagement system or disengagement system of a clutch, which allows a travel measurement, in particular an inductive travel measurement, in particular with reduced space requirement. The object is achieved by a master cylinder with the

Features of claim 1. The solution of the object according to the invention is further carried out by a hydraulic system with the features of claim 7. Preferred embodiments of the invention are specified in the dependent claims.

The master cylinder according to the invention is particularly suitable for a hydraulic system, in particular for a hydraulic clutch system or for a hydraulic brake system. He has for displaceably guiding a piston to a cylinder in which the piston is displaceably guided, wherein for determining the position of the piston adjacent to the cylinder and outside of the cylinder, an inductive sensor is provided. The master cylinder is characterized in that the piston is at least partially made of a detectable by the inductive sensor material, in particular metal, designed.

The above-described, in particular also referred to as CMC, master cylinder is

in particular suitable for installation or use in a hydraulically actuated brake system or particularly preferably in a hydraulically actuated clutch system, in particular in a clutch engagement system or a clutch release system. A prescribed master cylinder allows in particular an inductive displacement measurement or an inductive position determination of the piston in a small footprint.

Such a master cylinder has to displaceably guide a piston on a cylinder, which is to serve as a pressure chamber for receiving a fluid to be delivered, the hydraulic fluid. As a hydraulic fluid can serve in non-limiting brake fluid. The cylinder may be bounded by a housing or at least partially by a guide sleeve. In other words, the housing or the guide sleeve, which is also referred to as a bushing, can have or limit the cylinder in its interior, wherein the piston is arranged in the cylinder and guided axially displaceably there. The guide sleeve can in turn be arranged in a housing of the master cylinder or be part of the housing. Furthermore, the cylinder can define the primary pressure chamber of the master cylinder or at least partially limit it. By displacing the piston in the cylinder, the hydraulic fluid can thus be conveyed from the master cylinder into a hydraulic line connected to the cylinder and from there to a slave cylinder, in order to operate a hydraulic system, in particular a hydraulic clutch system. To realize this, for example, on the piston, a piston rod may be movably arranged, which ensures a connection to a pedal device, via which the piston is displaceable in the sleeve and thus the master cylinder is manually operable. However, it will be readily apparent to those skilled in the art that operating the master cylinder is not limited to a manual operation described above.

In order to enable a control of the respective hydraulic system, it can by

Be important to determine the instantaneous position of the piston in the cylinder. In order to realize this, an inductive sensor is provided for determining the position or for determining the travel of the piston adjacent to the cylinder and outside the cylinder, for example on the housing, embedded in the housing and / or on the side of the guide sleeve opposite the cylinder. Such an inductive sensor serves in particular as an inductive displacement sensor or as an inductive position sensor. An inductive position determination is particularly advantageous, since this allows a highly accurate and further contactless position determination, which does not adversely affect the actual work of the master cylinder. The sensor is arranged adjacent to the cylinder, which may in particular mean that the sensor is positioned in such a way to the cylinder that a displacement measurement or a position determination of the piston in the cylinder is made possible or that the sensor monitors the cylinder.

In this case, the inductive sensor can be configured as such, as is well known from the prior art for inductive position sensors or for inductive displacement sensors per se. Such a sensor may, for example, be based on the principle that the inductance of the coil changes in accordance with the immersion depth of the piston into a coil due to the changing permeability of the material located inside the coil, which is detectable in a manner known to the person skilled in the art. Thus, in the case of a previously described master cylinder, the inductive sensor may have one or a plurality of optionally connected coils which frame the cylinder and whose inductance can be detected by a corresponding means, whereby the position of the piston can be directly deduced.

In order to carry out an inductive measurement, a so-called target is thus to be provided as object to be detected and penetrating into the coil. Due to the fact that the piston is at least partially made of a material which can be detected by the inductive sensor, it can be advantageously made possible according to the invention that the target does not need to be applied to the piston or needs to be fixed there, but rather that the target can be formed in a particularly simple manner by the piston itself. This embodiment can provide significant advantages over the solutions known from the prior art. In particular, a master cylinder can be created, which is constructed by a component reduction from as few individual parts. In this way costs can be saved and the manufacturing process can be simplified.

Thus, on the one hand, the production of such a piston may be possible in a particularly cost-effective manner, since the further working step of applying the target, for example comprising screwing or clipping, can be dispensed with. Furthermore, a waiver of such additional process steps allows a saving of additional parts, which can also have a positive effect on the cost. By saving such process steps, the manufacturing process can be significantly simplified.

Moreover, in addition to the saving of the process step of applying the target, the piston can be constructed much simpler, since it can be dispensed with special receptacles for the target on the piston. Thus, it is often provided in the known from the prior art solutions to provide special structures, such as recesses, in which or on which the target can be positioned. Such structures are not necessary in the solution according to the invention.

A simple production of the piston can be realized in that the piston is completely formed from the corresponding detectable by the inductive sensor material. While it is not excluded within the scope of the present invention that only a portion of the piston is formed of the corresponding material, complete formation of the piston with respect to a simplified manufacturing process is even more preferred. In this case, complete formation of the piston from such a material does not preclude the integration of further functional components, such as a connector for a piston rod, seals or the like, into the piston after the piston has been manufactured, and such components may differ from one another Material, such as plastic, can be shaped.

Furthermore, a solution according to the invention can be realized very space-saving, since no additional space for a target needs to be maintained. Furthermore, the piston can be realized in a desired length and there are no requirements related to the piston length are met by the target.

Finally, measuring using a master cylinder as described above may be particularly accurate since attachment of a target is often associated with some tolerance in the exact position of the target on the piston as well as the gap between the guide sleeve, for example, and the target. Such tolerances can be reduced according to the invention or even completely avoided, so that measuring tolerances can be particularly small and therefore the measured values obtained can be particularly accurate.

In summary, a prescribed master cylinder in a particularly simple and cost-effective manner allow improved position determination or displacement measurement of the piston in the guide sleeve.

In a preferred embodiment of the master cylinder, the piston may be at least partially made of aluminum. Again, the piston may be partially or entirely formed of aluminum, as generally described above. In particular, aluminum can have the advantage of good measurement behavior using an inductive sensor. In addition, aluminum has a very light weight, which makes it possible, especially in mobile applications, not only to form a target but also the piston as a whole made of aluminum. As a result, a prescribed master cylinder is also suitable for use in mobile applications provided hydraulic systems, such as hydraulic clutch systems in motor vehicles, without problems.

In a further preferred embodiment of the master cylinder of the inductive sensor for monitoring a primary pressure chamber may be arranged. In other words, the inductive sensor may be arranged to detect a position or movement of the piston in the primary pressure space. In particular, in this embodiment, a particularly space-saving enabling an inductive position determination of the piston can be realized, since the piston can be made much shorter compared to an arrangement of the sensor in the secondary pressure chamber. In addition, it can be made possible that the piston is located substantially at every deflection within the primary pressure chamber, so that at any time a position determination of the piston is possible. In a further preferred embodiment of the master cylinder, the piston can be dynamically sealed. In other words, a seal may be provided which is not fixed directly to the piston and moves along the sleeve or a housing part, but rather, for example, a seal attached to the guide sleeve or a housing part may be provided on the piston move along and thus the piston against the sleeve or a housing part, for example, dynamically seal. In particular, in this embodiment, the piston can thus be particularly easy to produce, since the piston need not be designed for securing a seal, in particular a secondary seal. Thus, the piston may have a substantially cylindrical shape at least in the region of the secondary pressure chamber.

In a further preferred embodiment of the master cylinder, the inductive sensor may have a PCB coil for generating an electromagnetic field. In particular, using such a coil, a particularly accurate position detection can be possible and the necessary space can be limited. In this case, a PCB coil (PCB: printed circuit board) can be understood in a manner which is generally known to a person skilled in the art, in particular a planar coil which is printed on a dielectric, such as a printed circuit board, for example. The master cylinder or the housing can be formed in one or more parts.

In a further preferred embodiment of the master cylinder of the master cylinder can be arranged in a hydraulic system, such as in particular in a hydraulic clutch system or in a hydraulic brake system.

With regard to further technical features and advantages of the master cylinder according to the invention, reference is hereby explicitly made to the explanations in connection with the hydraulic system according to the invention, the figure and the description of the figures.

The invention further relates to a hydraulic system, in particular a hydraulic clutch system or a hydraulic brake system, such as for a motor vehicle, wherein the hydraulic system is characterized in that it comprises a master cylinder, which is configured as described in detail above.

In summary, such a hydraulic system has the advantage that, by using a master cylinder according to the invention, it is particularly simple and cost-effective. tengünstige manner can allow improved position determination or displacement measurement of the piston in the cylinder such as in the guide sleeve of the master cylinder and thereby allow, for example, an improved control behavior of the hydraulic system.

With regard to further technical features and advantages of the hydraulic system according to the invention, reference is hereby explicitly made to the explanations in connection with the master cylinder according to the invention, the figure and the description of the figures.

In the following, a particularly preferred embodiment of the invention will be explained with reference to the accompanying drawings, wherein it is explicitly pointed out that the object according to the invention is not limited to the exemplary embodiment described. Showing:

Fig. 1 is a schematic representation of an embodiment of a master cylinder according to the invention for a hydraulic system.

Fig. 1 shows an embodiment of a master cylinder 10, which may be part of a hydraulic system, in particular power transmission system, such as a hydraulic clutch system, or a hydraulic brake system.

The master cylinder 10 has a housing 12 arranged in a cylinder 14 which can form a primary pressure chamber. In the cylinder 14 while a piston 16 is axially movable or displaceable guided such that the piston 16 is axially displaceable in the cylinder 14 and in the primary pressure chamber. In Figure 1, the master cylinder 10 is shown such that the piston 16 is in a release position or rest position and thus is ready to promote by an axial displacement hydraulic fluid to a slave, not shown.

It will further be appreciated that a piston rod 18 is provided which may be connected to a manually operable pedal or to an electromagnetically / hydraulically operated actuator and further acts on the piston 16 to move or axially displace it to operate the master cylinder 10. For improved guidance of the piston 16, furthermore, the axial length of the cylinder 14 can be adapted to a travel or stroke of the piston 16. This structural design causes the piston 16 is sufficiently supported and guided regardless of its position, which has an advantageous effect on the operation and the service life of the master cylinder 10.

The piston 16 can also by corresponding seals 20, 22 against the

Be sealed housing 12, as is generally known in the art. In this case, the seals 20, 22 in particular such, for example, on the housing 12, arranged, that the piston 16 is dynamically sealed. To provide an effective seal, a further seal is also provided at a free end of the housing 12, which bears against the piston rod 18 under prestress and thus effectively prevents dirt entering the housing 12, for example when the piston 16 is actuated in the primary pressure space.

The housing 12 is also connected via a connection 26 with a liquid reservoir not shown in FIG. 1, from which hydraulic fluid can flow without pressure into the cylinder 14 for filling or refilling the hydraulic system at a piston position, as shown in FIG. Upon displacement of the piston 16 in the cylinder 14 or in the primary pressure space in which a spring may be provided for spring biasing of the piston 16, the hydraulic fluid therein is displaced via a port 28 and passes through a pressure line to a with the master cylinder 10 in Connecting, not shown in Fig. 1 slave cylinder.

For a position determination of the piston 16 in the cylinder 14, for example, in order to be able to control the master cylinder 10 in a suitable manner, adjacent to the cylinder 14 and, for example embedded in the housing 12, an inductive sensor 30 is provided. It is further provided that the piston 16 at least partially, in particular completely, from a detectable by the inductive sensor 30 material, such as metal, in particular made of aluminum, is configured. Alternatively, the piston 16 itself could also consist of a material which can not be detected by the sensor 30 and a coating may be provided on the piston 16 which is detectable by the sensor 30. In FIG. 1, it is shown that the inductive sensor 30 is arranged to monitor the primary pressure space. In detail, the inductive sensor 30 may include a coil 32, such as a PCB coil, for generating an electromagnetic field, the piston 16 being in the inductance. Onsfeld the induction coil 32 is located. When the master cylinder 10 is actuated, the metallic piston 16 moves or displaces axially within the cylinder 14. As the piston 16 of the electromagnetic field penetrates the coil 32, the sensor 30 can detect the exact position of the piston 16. This information can then be transmitted to a recipient.

Master cylinder

casing

cylinder

piston

piston rod

poetry

connection

inductive sensor

Kitchen sink

Claims

claims

1 . Master cylinder for a hydraulic system, in particular for a hydraulic clutch system or for a hydraulic brake system, comprising a cylinder (14) for displaceably guiding a piston (16) in which the piston (16) is displaceably guided, wherein for determining the position of the piston ( 16) adjacent to the cylinder (14) and outside the cylinder (14) an inductive sensor (30) is provided, characterized in that the piston (16) is at least partially made of a detectable by the inductive sensor (30) material.

2. master cylinder according to claim 1, characterized in that the piston (16) is at least partially, in particular completely, made of aluminum.

3. master cylinder according to claim 1 or 2, characterized in that the inductive sensor (30) is arranged for monitoring a primary pressure chamber.

4. master cylinder according to one of claims 1 to 3, characterized in that the piston (16) is dynamically sealed.

The master cylinder according to claim 1, wherein the inductive sensor has a coil for generating an electromagnetic field.

6. master cylinder according to one of claims 1 to 5, characterized in that the master cylinder (10) is arranged in a hydraulic coupling system.

7. Hydraulic system characterized in that the hydraulic system comprises a master cylinder (10) according to one of claims 1 to 6.