Pedal force simulator and braking system

Abstract

Pedal force simulator (1) for a hydraulic brake system (10) of a vehicle, wherein the pedal force simulator (1) has a simulator chamber (2) and a simulator piston (3) movable within the simulator chamber (2) along an operating path (100), wherein the pedal force simulator has a line arrangement via which the simulator chamber (2) can be brought into fluid communication with a pressure chamber of a brake cylinder (11) of the hydraulic brake system (10), characterized in that the line arrangement has a valve arrangement whose throttling effect depends on the position of the simulator piston (3) along the operating path (100).

Description

[0001] The present invention is based on a pedal force simulator for a hydraulic brake system of a vehicle according to the preamble of claim 1.

[0002] Such pedal force simulators are known, for example, from the publication WO 2012 / 150 108 A1 and serve to give the user of a braking system a familiar brake pedal feel, even if the braking force is no longer generated directly by the actuation force manually applied by the user to the brake pedal, but rather, as a result of electronic signal transmission, the braking torque is controlled by an external force, such as an electric motor, a compressor, or the like, depending on the user's foot force (also known as "brake-by-wire"). By means of the pedal force simulator, the user is given haptic feedback in the form of a predetermined force-displacement behavior when the vehicle brake pedal is actuated. This corresponds to the actual braking behavior of the vehicle brake system, making it easier for the driver to dose the braking force.In particular, the specified force-displacement behavior can be used to simulate the braking feeling familiar from conventional hydraulic vehicle braking systems.

[0003] It is an object of the present invention to provide a pedal force simulator which provides the user of the brake system with an improved and more realistic braking feeling.

[0004] This object is achieved with a pedal force simulator for a hydraulic brake system of a vehicle, wherein the pedal force simulator has a simulator chamber and a simulator piston movable within the simulator chamber along a working path, wherein the pedal force simulator has a line arrangement via which the simulator chamber can be brought into fluid connection with a pressure chamber of a brake cylinder of the hydraulic brake system, and wherein the line arrangement has a valve arrangement whose throttling effect depends on the position of the simulator piston along the working path.

[0005] The pedal force simulator according to the invention has the advantage over the prior art that the throttling effect of the valve arrangement depends on the position of the simulator piston, whereby the damping of the brake system is changed or switched depending on the position of the simulator piston. This can improve the braking feel for the driver, which in particular improves the suitability of the pedal force simulator for circuit use.

[0006] Advantageous embodiments and further developments of the invention can be found in the dependent claims and the description with reference to the drawings.

[0007] According to a preferred embodiment of the present invention, the line arrangement comprises a main line and a secondary line connected in parallel with the main line, wherein the main line and the secondary line open independently of one another into the simulator chamber. The valve arrangement comprises a main valve arranged in the main line and a secondary valve arranged in the secondary line. Damping is thus achieved via two separate valves.

[0008] According to a further preferred embodiment of the present invention, the pedal force simulator is designed such that the simulator piston is moved from an initial position along the working travel with increasing deflection of a brake pedal of the brake system. The pedal force simulator is preferably designed such that the secondary line is in fluid communication with the simulator chamber when the simulator piston is in the initial position, and that the fluid connection between the secondary line and the simulator chamber is blocked when the simulator piston is moved a predetermined distance along the working travel. Advantageously, the fluid connection between the secondary line and the simulator chamber is automatically released when the simulator piston is in or near its initial position and blocked when the simulator piston is deflected the distance from the initial position.Blocking the secondary line also deactivates the secondary valve, leaving only the main valve to allow equalizing flow between the pedal force simulator chamber and the brake system's master cylinder. Damping therefore increases dramatically when the simulator piston is deflected beyond its travel distance.

[0009] According to a further preferred embodiment of the present invention, the secondary line opens into the simulator chamber in such a way that the opening of the secondary line is open when the simulator piston is in or near the starting position, and that the opening of the secondary line is blocked by the simulator piston when the simulator piston is moved along the working path by a predetermined distance. Preferably, the simulator piston has a channel extending from a wall of the simulator piston to a functional surface of the simulator piston facing the simulator chamber, wherein the wall faces the opening of the secondary line when the simulator piston is in the starting position.It is conceivable that the simulator piston comprises a base body in which the channel is formed, and that the base body blocks the opening of the secondary line into the simulator chamber when the simulator piston is deflected beyond the specific distance.

[0010] According to a further preferred embodiment of the present invention, a recess is formed in the simulator piston in the region of the wall, from which the channel extends to the functional surface. Preferably, the size of the recess, parallel to the working direction, determines the distance by which the simulator piston can be deflected from its initial position until the opening of the secondary line is blocked and the secondary valve is thus deactivated.

[0011] Preferably, the maximum extension of the recess parallel to the working direction therefore essentially corresponds to the predetermined path length.

[0012] According to a further preferred embodiment of the present invention, the throttling effect of the secondary valve is adjustable, particularly during operation of the pedal force simulator. Thus, the resistance of the pedal force simulator can advantageously be optimally adapted to the requirements of the braking system or to the individual needs of the user. It would also be conceivable for the throttling effect of the secondary valve to be adjustable during operation.

[0013] According to a further preferred embodiment of the present invention, the pedal force simulator comprises a return means for returning the simulator piston to its initial position opposite to the working travel, wherein the return means is designed to be elastic and / or deformable. The return means preferably comprises a torsion spring designed as a compression spring and a rubber buffer arranged behind the torsion spring along the working travel.

[0014] A further subject of the present invention is a brake system for a vehicle comprising a brake cylinder coupled to a foot brake pedal and a pedal force simulator according to the invention, wherein the pedal force simulator is operatively connected to a pressure chamber of the brake cylinder.

[0015] Further details, features, and advantages of the invention will become apparent from the drawings and the following description of preferred embodiments with reference to the drawings. The drawings merely illustrate exemplary embodiments of the invention, which do not limit the essential inventive concept. Fig. 1 shows a schematic view of a braking system of a vehicle with a pedal force simulator according to an exemplary embodiment of the present invention. Fig. 2 shows the pedal damping of the pedal force simulator according to the exemplary embodiment of the present invention.

[0016] In Fig. 1 is a schematic view of a brake system 10 of a vehicle with a pedal force simulator 1 according to an exemplary embodiment of the present invention.

[0017] The brake system 10 comprises a brake cylinder 11 in which a brake piston 12 is movably mounted. The brake piston 12 is coupled to a brake pedal (not shown) of the vehicle and can be deflected by a driver using the brake pedal against the force of two return springs 13. The brake piston 12 moves along a deflection direction 14.

[0018] The present brake system 10 is a so-called “brake-by-wire” brake system, ie the braking force is not generated directly by the actuating force manually applied by the user to the brake piston, but rather the deflection of the brake piston is electronically evaluated by a brake electronics unit 15 (not explained in more detail) and transmitted by means of electronic signal transmission to a brake force generator, which then generates the braking force.

[0019] To still convey the real braking feel of a hydraulic brake system to the user, the present brake system 10 includes a pedal force simulator 1, which provides the user with haptic feedback in the form of a predefined force-displacement behavior when the vehicle brake pedal is depressed. This haptic feedback corresponds to the actual braking behavior of the vehicle brake system, making it easier for the user to dose the braking force.

[0020] For this purpose, the pedal force simulator 1 has a simulator chamber 2 in which a simulator piston 3 is mounted so as to be displaceable along a travel 100. The simulator piston 3 is sealed against the wall 5 of the simulator chamber 2 by means of a circumferential sealant 4. A return means is also arranged within the simulator chamber 2. In the present example, the return means comprises a torsion spring 6 designed as a compression spring and a rubber buffer 7. The torsion spring 6 moves the simulator piston 3, when the brake pedal is not actuated, counter to the travel 100 to its initial position.

[0021] The simulator chamber 2 and the brake cylinder 11 are fluidly connected to one another via a main line 9 and a separate secondary line 8. A main valve 20 is located in the main line 9, while a secondary valve 21 is located in the secondary line 8. Depending on their settings, the main valve 20 and the secondary valve 21 throttle the fluid flow through the main line 9 and the secondary line 8, respectively. It is conceivable that the throttling effect of the main valve 20 and / or the secondary valve 21 is adjustable during operation of the pedal force simulator 1.

[0022] The pedal force simulator 1 is now designed such that the secondary line 8 is only in fluid communication with the simulator chamber 2 when the simulator piston 3 is in or near its starting position, and such that the fluid connection between the secondary line 8 and the simulator chamber 2 is blocked by the simulator piston 3 when the simulator piston 3 is moved along the working path 100 by at least a predetermined distance 25. This is achieved in that the wall of the simulator piston 3 facing the opening of the secondary line 8 into the simulator chamber 2 has a recess 23 which, parallel to the working path 100, has a maximum extension that defines the value of the predetermined distance 25. The recess 23 also opens into an inner channel 24 formed within the simulator piston 3, which opens into the simulator chamber 2 on a side facing away from the torsion spring 6.

[0023] When the user of the brake system 10 now operates the brake pedal and the brake piston 12 is thereby deflected, fluid flows from the brake cylinder 11 via the main line 9 into the simulator chamber 2. Since the secondary line 8 is also in fluid communication with the simulator chamber 2 via the recess 23 and the inner channel 4, fluid also flows through the secondary line 8 from the brake cylinder 11 into the simulator chamber 2. The fluid is throttled by the main valve 20 and the secondary valve 21. The simulator piston 12 is deflected from its initial position along the working path 100 (see Fig. 1).

[0024] At some point, the simulator piston 12 is deflected by the predetermined distance 25 along the working path 100 and the opening of the secondary line 8 reaches the outer limit of the recess 23. The opening of the secondary line 8 is then blocked by the wall of the simulator piston 3. From this point on, only fluid can reach the simulator chamber 2 through the main line 8. The resistance therefore increases abruptly because the flow cross-section available to the fluid is reduced due to the elimination of the secondary line 8. The damping by the pedal force simulator 1 is therefore dependent on the position of the simulator piston 3 along the working path 100 and adjusts automatically after the working piston 3 moves the predetermined distance 25.

[0025] In Fig.Figure 2 illustrates the pedal damping 26 of the pedal force simulator 1 as a function of the position of the simulator piston 3 along the working travel 100 for different throttle settings. The diagram shows that upon reaching the predetermined travel distance 25, the damping increases abruptly, since the secondary line 8 is blocked by the simulator piston 3 from the time the predetermined travel distance 25 is reached.

Claims

[1] Pedal force simulator (1) for a hydraulic brake system (10) of a vehicle, wherein the pedal force simulator (1) has a simulator chamber (2) and a simulator piston (3) movable within the simulator chamber (2) along a working path (100), wherein the pedal force simulator has a line arrangement via which the simulator chamber (2) can be brought into fluid connection with a pressure chamber of a brake cylinder (11) of the hydraulic brake system (10), characterized by that the line arrangement has a valve arrangement whose throttling effect depends on the position of the simulator piston (3) along the working path (100). [2] Pedal force simulator (1) according to claim 1, wherein the line arrangement comprises a main line (9) and a secondary line (8) connected in parallel to the main line (9), wherein the main line (9) and the secondary line (8) open independently of one another into the simulator space (2), wherein the valve arrangement comprises a main valve (20) arranged in the main line (9) and a secondary valve (21) arranged in the secondary line (8). [3] Pedal force simulator (1) according to claim 2, wherein the pedal force simulator (1) is designed such that the simulator piston (3) is moved from an initial position along the working path (100) with increasing deflection of a brake pedal of the brake system (10). [4] Pedal force simulator (1) according to claim 3, wherein the pedal force simulator (1) is designed such that the secondary line (8) is in fluid communication with the simulator chamber (2) when the simulator piston (3) is in or near its initial position, and that the fluid connection between the secondary line (8) and the simulator chamber (2) is blocked when the simulator piston (3) is moved along the working path (100) by a predetermined distance (25). [5] Pedal force simulator (1) according to claim 4, wherein the secondary line (8) opens into the simulator chamber (2) in such a way that the opening of the secondary line (8) is released when the simulator piston (3) is in or near the starting position, and that the opening of the secondary line (8) is blocked by the simulator piston (3) when the simulator piston (3) is moved along the working path (100) by a predetermined distance (25). [6] Pedal force simulator (1) according to claim 5, wherein the simulator piston (3) has a channel (24) which extends from a wall of the simulator piston (3) to a functional surface of the simulator piston (3) facing the simulator chamber (2). [7] Pedal force simulator (1) according to claim 6, wherein the wall faces the mouth of the secondary line (8) when the simulator piston (3) is in the starting position. [8] Pedal force simulator (1) according to claim 7, wherein in the region of the wall a recess (23) is formed in the simulator piston (3), from which the channel (24) extends to the functional surface. [9] Pedal force simulator (1) according to claim 8, wherein the maximum extension of the recess (23) parallel to the working path (100) substantially corresponds to the predetermined path length (25). [10] Pedal force simulator (1) according to one of the preceding claims, wherein the throttling effect of the secondary valve (21) is adjustable, in particular during operation of the pedal force simulator (1). [11] Pedal force simulator (1) according to one of the preceding claims, wherein the throttling effect of the secondary valve (21) is adjustable during operation. [12] Pedal force simulator (1) according to one of the preceding claims, wherein the pedal force simulator (1) has a return means for returning the simulator piston (3) counter to the working path (100) to its initial position, wherein the return means is designed to be elastic and / or deformable. [13] Pedal force simulator (1) according to claim 12, wherein the return means comprises a torsion spring (6) designed as a compression spring and a rubber buffer (7) arranged behind the torsion spring (6) along the working path (100). [14] Brake system (10) for a vehicle comprising a brake cylinder (11) coupled to a foot brake pedal and a pedal force simulator (1) according to one of the preceding claims, wherein the pedal force simulator (1) is operatively connected to a pressure chamber of the brake cylinder (11).

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