Pedal travel simulator for hydraulic external force-vehicle brake systems

Abstract

The invention proposes limiting the travel of a piston (4) of a pedal travel simulator (1), which has a spring ring (19) which is inserted into a circumferential groove in a cylinder (3) of the pedal travel simulator (1). The spring ring (19) relieves a cover (5) of the pedal travel simulator (1) which closes the cylinder (3) of the pedal travel simulator (1).

Description

Technical Field

[0001] The invention relates to a pedal stroke simulator.

[0002] In hydraulic vehicle brake systems actuated by external forces, a pedal travel simulator enables the pedal travel (lever travel in the case of a hand brake) to be realized when the master brake cylinder is actuated. When actuated by external forces, the master brake cylinder serves as a setpoint value transmitter for a hydraulic brake pressure that is not generated by the master brake cylinder but by external energy, for example, by a hydraulic pump or a piston-cylinder unit. When braking by external forces, the master brake cylinder is hydraulically separated from the rest of the vehicle brake system, for example, by a shut-off valve, and when it is actuated, brake fluid is displaced into the pedal travel simulator, which is connected to the master brake cylinder during external braking. Background Art

[0003] Publication DE 102017210041 A1 discloses a pedal travel simulator having a piston that can be axially displaced in a cylinder and a helical compression spring as a piston spring, which loads the piston into the cylinder. The piston spring is accommodated in a bowl-shaped cover, which is arranged on the side end of the cylinder to axially extend the cylinder and closes the cylinder in a fluid-tight manner. Summary of the invention

[0004] The pedal travel simulator according to the invention is provided for connection to a master brake cylinder which can be actuated by muscle force of a hydraulic external force vehicle brake system. It has a cylinder and a piston which can be axially displaced in the cylinder. A bowl-shaped cover preferably closes the side end of the cylinder in a fluid-tight manner. "Bowl-shaped" means in particular a tubular and in particular a cylindrical tubular shape with an open and a closed side end, wherein the open side end faces the cylinder.

[0005] A first spring element is arranged in the cover, which loads the piston into the cylinder. The first spring element can be, for example, a helical compression spring, in particular a disc spring assembly. It can load the piston directly or indirectly via another component, and it does not have to load the piston over the entire stroke of the piston.

[0006] In order to limit the stroke of the piston in the direction of the cover, the invention provides a spring ring, which is inserted into a circumferential groove between the piston and the cover and protrudes inward from the groove, so that the spring ring forms a piston stop, which limits the stroke of the piston in the direction of the cover. The piston stop keeps the cover from the piston force generated by the brake pressure acting on the piston on the side facing away from the cover. In addition, the spring ring forming the piston stop limits the spring force with which the first spring element is supported in the cover, because the limitation of the stroke of the piston also limits the tensioning stroke of the first spring element.

[0007] One embodiment of the invention provides a mount which holds the first spring element in the cover of the pedal travel simulator and, if the first spring element is a disc spring assembly, in particular also holds its disc springs together. The mount allows the first spring element to move in order to tension the first spring element. The cover, the mount and the first spring element form a preassembled component which can be assembled before assembling the pedal travel simulator and simplifies the assembly of the pedal travel simulator according to the invention.

[0008] All features disclosed in the description and the drawings can be implemented in an embodiment of the invention either individually or in principle in any combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The invention is explained in more detail below with reference to the embodiments shown in the drawings. The single FIGURE shows an axial section through a pedal travel simulator according to the invention. DETAILED DESCRIPTION

[0010] The pedal travel simulator 1 according to the invention shown in the drawing is arranged in a hydraulic block 2 of a hydraulic external force-brake pressure- and slip control device of a vehicle brake system (not shown in the rest of the figure). The hydraulic block 2 is a cuboid metal block which has receptacles for solenoid valves and other components of the brake pressure- and slip control device, which are connected to one another via bores in the hydraulic block 2 according to the circuit diagram of the hydraulic vehicle brake system. Such hydraulic blocks 2 and brake pressure- and slip control devices are known and will not be explained in detail here.

[0011] The hydraulic block 2 has a cylindrical blind hole which forms a cylinder 3 of the pedal travel simulator 2. A piston 4 is accommodated in the cylinder 3 so as to be axially displaceable.

[0012] The cylindrical tubular cover 5 with an open end and a closed end closes the side end of the cylinder 3 in a fluid-tight manner, wherein the open end of the cover 5 faces the cylinder 3. Due to its shape, the cover 5 can be called "bowl-shaped". In this embodiment, it is made of sheet metal as a deep-drawn part, but this is not mandatory for the present invention.

[0013] At its open end, the cover 5 has a circumferential, outwardly projecting flange 6 , on which the cover is fastened to the cylinder 3 in the manner of a lock nut by means of a threaded ring 7 which is screwed into the cylinder 3 at a bore.

[0014] A disc spring assembly is arranged in the cover 5 as the first spring element 8. A force transmitter 9 is arranged between the piston 4 and the first spring element 8, which has two tappets 10, 11, which protrude coaxially in opposite directions from a flange 12 of the force transmitter 9. One of the two tappets 10 protrudes into the central bore of a disc spring 13 of the disc spring assembly forming the first spring element 8 of the pedal travel simulator 1 and centers or guides the disc spring 13.

[0015] Another tappet 11 projects into a conical and coaxial depression 14 in the piston 4, wherein, when the piston 4 is located on the bottom 15 of the cylinder 3 as shown in the figure, the tappet 11 does not rest on the bottom of the depression 14, so that the piston 4 can move a short distance without the force transmitter 9. If the tappet 11 of the force transmitter 9 rests on the bottom of the depression 14 of the piston 4 and the flange 12 of the force transmitter 9 rests on the first spring element 8, the first spring element 8 transmits its spring force to the piston 4.

[0016] The pedal travel simulator 1 has a support 16 for the first spring element 8 or for the disc springs 13 of its disc spring group. In this exemplary embodiment, the support 16 is a cylindrical tubular sleeve with a continuous longitudinal slit 17, so that it is radially elastic and radially resilient. The support 16 rests on the cover 5 with prestress on the inside, so that it is clamped in the cover 5. In this exemplary embodiment, the support 16 is axially longer than the cover 5 like the first spring element 8 and therefore protrudes from the cover 5 into the cylinder 3, but this is not mandatory for the invention.

[0017] For example, it is also possible to have a support 16 without longitudinal slots 17, which is pressed into the cover 5 and / or the support 16 is not exactly circular and / or has outwardly projecting grooves, ridges or the like and is thus held clamped in the cover 5. This list is intended to illustrate alternatives and is not exhaustive.

[0018] At the end facing the piston 4, the edge of the support 16 is deformed inwardly and overlaps the flange 12 of the force transmitter 9, whereby the support 16 holds the force transmitter 9 on its flange 12 and holds the first spring element 8 in the cover 5 via the flange 12. The cover 5, the support 16, the force transmitter 9 and the first spring element 8 form a preassembled component that can be assembled before assembling the pedal travel simulator 1, which simplifies the assembly of the pedal travel simulator 1.

[0019] The first spring element 8 is axially movable in the abutment 16 so that it can be axially elastically compressed, ie tensioned, by the piston 4 via the force transmitter 9 . The abutment 16 forms a guide for the first spring element 8 .

[0020] In the cover 5, between its closed end and the first spring element 8, a perforated disk is arranged as a support disk 18, the diameter of which is almost as large as the inner diameter of the cover 5. The support disk 18 thus bears against the interior of the cover 5 in the circumferential vicinity of the transition from the circumferential wall of the cover 5 to the closed end and thus transmits the spring force of the first spring element 8 to the cover 5 in the circumferential vicinity, whereby the spring force acts essentially as a tensile force in the circumferential wall of the cover 5 and does not or hardly acts in the closed end of the cover 5. “In the circumferential vicinity” means that there is no spacing from the inner circumference of the cover 5 or a spacing from the inner circumference of the cover of at most approximately the wall thickness of the cover 5.

[0021] Between the flange 12 of the force transmitter 9 and the piston 4, the cylinder 3 has a circumferential groove, which is V-shaped in the exemplary embodiment, into which a spring ring 19 is inserted, which projects inwardly from the groove and forms a piston stop which limits the travel of the piston 4 in the direction of the cover 5. If the piston 4 abuts against the spring ring 19, the first spring element 8 is no longer tensioned further and its spring force no longer increases, even if the hydraulic pressure on the side of the piston 4 facing away from the first spring element 8 continues to increase. In this way, the spring ring 19 limits the spring force with which the first spring element 8 is pressed from the inside against the cover 5. In addition, the spring ring 19 prevents the first spring element 8 from "sticking", i.e., the coils of the helical compression spring are prevented from abutting against each other when the first spring element 8 is a helical compression spring, or the flat pressing and flat abutment of the disc springs 13 when the first spring element 8 is a disc spring assembly.

[0022] A relief hole 20 is introduced into the bottom of the groove into which the spring ring 19 is inserted, through which the brake fluid can flow out and in from the cover 5 and the cylinder 3 on the side of the piston 4 facing the cover 5 when the piston 4 moves in the cylinder 3. In this embodiment, the relief hole 20 intersects the groove tangentially at its bottom, but the relief hole 20 can also be introduced into the groove from other directions, such as parallel to the axis (not shown).

[0023] A helical compression spring is arranged between the flange 12 of the force transmitter 9 and the piston 4 as a second spring element 21, which presses the piston 4 and the force transmitter 9 away from each other, wherein spring elements other than helical compression springs are also possible (not shown). The second spring element 21 has only a fraction of the spring force of the first spring element 8. It loads the piston 4 until the tappet 11 of the force transmitter 9 abuts against the bottom of the depression 14 of the piston 4. The second spring element 21 simulates the so-called "jumping in", i.e. a low actuation force of the master brake cylinder of the vehicle brake system, until the brake lining of the hydraulic wheel brake abuts against the brake disc, brake drum or other brake body.

[0024] The flange 12 of the force transmitter 9 has three radially extending ribs 22 on its side facing the piston 4, which are arranged uniformly or unevenly distributed around the tappet 10 in the circumferential direction. The second spring element 21 is supported on the ribs 22, which enable the adjustment of the spring force of the second spring element and thus the "jump-in" adjustment by plastic upsetting. The flange 12 of the force transmitter 9 can also have more than three ribs 22 or other supports for the second spring element 21 (not shown).

[0025] On the side of the piston 4 facing away from the cover 5, the cylinder 3 of the pedal travel simulator 1 is connected to a master brake cylinder (not shown) via a connecting hole 23 that is bent in this exemplary embodiment. During actuation, brake fluid is pressed from the master brake cylinder into the cylinder 3 of the pedal travel simulator 1, causing the piston 4 of the pedal travel simulator 1 to move without a counterforce until the tappet 11 of the force transmitter 9 strikes the bottom of the depression 14 of the piston 4, then against the low spring force of the second spring element 21 and as soon as the tappet 11 of the force transmitter 9 rests in the depression 14 of the piston 4 against the significantly higher spring force of the first spring element 8, wherein the spring elements 8, 21 generate the actuation force of the master brake cylinder via the hydraulic pressure in the brake fluid. Usually, a solenoid valve is arranged between the master brake cylinder and the pedal travel simulator 1, via which the pedal travel simulator 1 is connected to the master brake cylinder during external force actuation of the vehicle brake system.

Claims

1. A pedal travel simulator for a hydraulic external force vehicle brake system, comprising a cylinder (3) in which a piston (4) is axially movably accommodated, a bowl-shaped cover (5) which is arranged to axially extend the cylinder (3) and close the side end of the cylinder (3), and a first spring element (8) which is arranged in the cover (5) and loads the piston (4) into the cylinder (3), characterized in that The pedal travel simulator (1) has a spring ring (19) as a piston stop, the spring ring being arranged in a circumferential groove between the piston (4) and the side end of the cylinder (3) in the cylinder (3), the cylinder (3) being closed by the cover (5), and the spring ring protruding inwardly from the groove so that the spring ring limits the travel of the piston (4) in the direction of the cover (5). A force transmitter (9) is arranged between the piston (4) and the first spring element (8), wherein the force transmitter transmits the spring force of the first spring element (8) to the piston (4). A second spring element (21) is arranged between the piston (4) and the force transmitter (9), the second spring element pressing the piston (4) and the force transmitter (9) away from each other. The force transmitter has two push rods (10, 11), which extend coaxially in opposite directions from a flange (12) of the force transmitter (9), one of the two push rods extending into a central hole of a first spring element (8), and the other push rod extending into a conical and coaxial depression (14) in the piston (4), wherein, when the piston (4) is located on the bottom (15) of the cylinder (3), the push rod does not rest on the bottom of the depression (14), so that the piston (4) can move a short distance without the force transmitter (9).

2. The pedal stroke simulator according to claim 1, characterized in that: The pedal travel simulator (1) has a bearing (16) which holds the first spring element (8) in the cover (5).

3. The pedal stroke simulator according to claim 2, characterized in that: The support (16) is held in the cover (5) in a clamped manner.

4. The pedal stroke simulator according to claim 2 or 3, characterized in that: The support (16) is tubular and radially elastic.

5. The pedal stroke simulator according to claim 2 or 3, characterized in that: The support (16) also holds the force transmitter (9) in or on the cover (5).

6. The pedal travel simulator according to claim 1 or 2, characterized in that: On the side of the first spring element (8) facing away from the piston (4), a support disk (18) is arranged in the cover (5), which transmits the spring force of the first spring element (8) to the cover (5) approximately in the circumferential direction.

7. The pedal stroke simulator according to claim 1 or 2, characterized in that: The first spring element (8) has a disc spring assembly.

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