Brake system for vehicle

Abstract

To improve durability of a brake mechanism and fuel economy during vehicle operation by suppressing drag resistance during brake release in the brake mechanism of an EPB.SOLUTION: The vehicle braking device includes a cylinder to which a brake fluid is supplied, a piston that slides by a fluid pressure in the cylinder, an adjuster that is disposed in the piston so as to be movable along a sliding direction of the piston and presses the piston by forward rotation of an electric motor in the electric parking brake, and an engagement mechanism that integrally engages the adjuster and the piston when the adjuster moves by reverse rotation of the electric motor and releases the engagement between the adjuster and the piston by an increase in the fluid pressure in the cylinder.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a braking system for a vehicle. [Background technology]

[0002] Conventionally, electromechanical parking brakes (EPBs) that transmit the rotational force of an electric motor to a brake mechanism have been known. When the brake is applied, the EPB rotates the electric motor in one direction (forward rotation) to transmit the rotational force of the electric motor to the brake mechanism, and stops the electric motor while generating braking force. When the brake is released, the EPB rotates the electric motor in the opposite direction (reverse rotation), thereby releasing the braking force (see Patent Document 1 below).

[0003] Furthermore, the braking mechanism of a conventional EPB includes a mechanism that slides the cylinder using the hydraulic pressure of the brake fluid supplied to the cylinder, in addition to a mechanism that presses the piston inside the cylinder against the brake pad, and a mechanism that slides the piston using the driving force of an electric motor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2011 / 158855 Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional technology, when the EPB brakes are applied, no hydraulic pressure is generated in the brake fluid, and the electric motor rotates the spindle in the forward direction, moving the adjuster and pushing up the piston with the shoulder of the adjuster. At this time, the pressing force of the piston causes pressure deformation of the brake pads and distortion of the caliper, pushing the piston out by an amount equal to the pressure deformation of the brake pads and the distortion of the caliper, ensuring braking.

[0006] In contrast, when the EPB brake is released, the adjuster is returned by the reverse rotation of the spindle, but the piston does not follow the movement of the adjuster. Although the piston returns slightly due to the seal structure installed on the piston, it is not able to fully return the amount of pressure deformation of the brake pad and the amount of distortion of the caliper, which creates a temporary drag resistance in the brake mechanism, creating a mechanical problem.

[0007] The present invention aims to solve these problems of the prior art by suppressing the drag resistance when the brake is released in the EPB brake mechanism, thereby improving the durability of the brake mechanism and fuel economy during vehicle operation. [Means for solving the problem]

[0008] In order to solve such problems, the present invention has the following configuration. a piston that slides due to hydraulic pressure within the cylinder; an adjuster that is disposed within the piston and is free to move along the sliding direction of the piston, and that presses the piston when an electric motor in an electric parking brake rotates in the forward direction; and an engagement mechanism that engages the adjuster and the piston together when the adjuster moves due to reverse rotation of the electric motor, and that disengages the adjuster from the piston when hydraulic pressure within the cylinder increases. [Effects of the Invention]

[0009] According to the present invention having such characteristics, in the brake mechanism of an EPB, drag resistance when the brake is released can be suppressed, thereby improving the durability of the brake mechanism and fuel economy when driving the vehicle. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an explanatory diagram showing a vehicle braking device according to an embodiment of the present invention; [Figure 2] FIG. 4 is an explanatory diagram of an engagement mechanism (a cross-sectional view taken along line BB in FIG. 3). [Figure 3] FIG. 3 is an explanatory diagram of an engagement mechanism (a cross-sectional view taken along the line AA in FIG. 2). [Figure 4] 3 is an explanatory diagram showing the operation of the vehicle braking system when the EPB is activated. FIG. [Figure 5] 4 is an explanatory diagram showing the operation of the vehicle braking device when the EPB is released. FIG. [Figure 6] 4 is an explanatory diagram showing the operation of the vehicle braking system when the main brake is applied after the EPB is released. FIG. [Figure 7] 5A and 5B are explanatory diagrams showing the operation of the vehicle braking system when the brake pads are worn; [Figure 8] 5A and 5B are explanatory diagrams showing the operation of the vehicle braking system when the brake pads are worn; DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals in different drawings denote parts with the same functions, and duplicated descriptions in each drawing will be omitted as appropriate.

[0012] As shown in Fig. 1, a vehicle braking device 1 includes at least a cylinder 10, a piston 20, and an adjuster 30. The cylinder 10 slidably supports the piston 20 via a piston seal 11, and brake fluid is supplied to the interior of the cylinder 10. When brake fluid is supplied into the cylinder 10, the piston 20 slides due to the hydraulic pressure. When the hydraulic pressure in the cylinder 10 increases, the piston 20 slides in the direction of arrow a and presses against brake pads (not shown), thereby braking the vehicle.

[0013] The adjuster 30 is disposed within the piston 20 so as to be movable along the sliding direction of the piston 20, and is driven by an electric motor 2 of an electric parking brake (hereinafter referred to as EPB). When the electric motor 2 of the EPB rotates forward, the adjuster 30 presses the piston 20 in the direction of the arrow a shown in the figure, and when the electric motor 2 of the EPB rotates backward, the adjuster 30 moves within the piston 20 in the direction opposite to the direction of the arrow a shown in the figure.

[0014] In the illustrated example, the adjuster 30 has a female thread portion 30a that screws onto the male thread portion 31a of the spindle 31, and when the electric motor 2 rotates the spindle 31 in one direction, it moves in the direction of arrow a, and a shoulder portion 30b of the adjuster 30 presses against a contact portion 20a inside the piston 20. When the electric motor 2 rotates the spindle 31 in the opposite direction, the adjuster 30 moves inside the piston 20 in the direction opposite to that of arrow a. The shaft portion 31b of the spindle 31 is rotatably supported by the cylinder 10 via the seal portion 12, and the male thread portion 31a mentioned above is inserted into the adjuster 30 via the seal portion 32 and screws onto the female thread portion 30a mentioned above.

[0015] The vehicle braking device 1 is provided with an engagement mechanism 40 that engages the piston 20 with the adjuster 30. This engagement mechanism 40 engages the adjuster 30 and the piston 20 together when the adjuster 30 moves due to reverse rotation of the electric motor 2, and disengages the adjuster 30 from the piston 20 as the hydraulic pressure in the cylinder 10 increases.

[0016] The engagement mechanism 40 includes an engagement pin 41 that protrudes from the inside of the adjuster 30 toward the inner surface of the piston 20, and an engagement groove 42 that is provided on the inner surface of the piston 20 and into which the engagement pin 41 engages; when the hydraulic pressure in the engagement groove 42 increases, the engagement pin 41 sinks into the inside of the adjuster 30.

[0017] 2 and 3, the specific configuration of the engagement mechanism 40 will be described. The base end side of an engagement pin 41 is disposed in the internal space of the adjuster 30, and a spring 43 is provided on the base end side of the engagement pin 41. The tip side of the engagement pin 41 is urged toward the inner surface of the piston 20 by the spring 43, and slides along the inner surface of the piston 20 when not fitted into the engagement groove 42.

[0018] When spindle 31 rotates with no brake fluid pressure inside piston 20, guide protrusion 30c of adjuster 30 engages with guide groove 20b on the inner surface of piston 20, causing adjuster 30 to move inside piston 20. Then, when the tip side of engagement pin 41 comes over engagement groove 42 on the inner surface of piston 20, the biasing force of spring 43 causes the tip side of engagement pin 41 to protrude from the outer peripheral surface of adjuster 30 and fit into engagement groove 42. This causes piston 20 and adjuster 30 to engage together.

[0019] The interior of adjuster 30 is sealed with cover 33, and a seal 32 is provided around shaft 31b of spindle 31. This isolates the interior of adjuster 30 from brake fluid entering piston 20. In addition, spindle 31 is provided with vent hole 31c along shaft 31b, and the interior of adjuster 30, where engagement pin 41 is located, is open to the atmosphere via communication hole 30d and vent hole 31c.

[0020] When the hydraulic pressure of the brake fluid in the cylinder 10 increases, the hydraulic pressure of the brake fluid entering the inside of the piston 20 also increases. Then, when the hydraulic pressure in the engagement groove 42 becomes greater than the biasing force of the spring 43, the engagement pin 41 is pushed by the hydraulic pressure and sinks into the inside of the adjuster 30. This causes the engagement between the piston 20 and the adjuster 30 to be released.

[0021] The operation of such a vehicle braking system 1 will now be described. In the state shown in Fig. 1, when the main brake is activated while the EPB is not activated and brake fluid pressure is applied to the inside of the cylinder 10, the fluid pressure in the engagement groove 42 increases, disengaging the piston 20 from the adjuster 30, and the piston 20 slides alone in the direction of arrow a, pressing against a brake pad (not shown).

[0022] In contrast, when the EPB is activated without hydraulic pressure being applied to the cylinder 10, as shown in Figure 4, the rotation of the spindle 31 causes the adjuster 30 to move in the direction of the arrow inside the piston 20, and when the engagement pin 41 comes above the engagement groove 42, the engagement pin 41 is pushed by the spring 43 and fits into the engagement groove 42. The adjuster 30 also pushes the piston 20, which in turn presses against a brake pad (not shown).

[0023] 5, when the EPB is released and the adjuster 30 is returned to its original position by the reverse rotation of the spindle 31, the absence of hydraulic pressure within the piston 20 maintains the engagement between the piston 20 and the adjuster 30 by the engagement mechanism 40, and the piston 20 slides in the direction of the arrow as the adjuster 30 moves, forming gaps between the piston 20, the brake pads, and the rotor. This reduces drag resistance when the EPB is released.

[0024] Furthermore, when the main brake is activated while the piston 20 and the adjuster 30 are engaged as shown in Fig. 5, the application of fluid pressure within the cylinder 10 increases the fluid pressure within the piston 20 as shown in Fig. 6, and when the fluid pressure within the engagement groove 42 exceeds the biasing force of the spring 43, the engagement pin 41 sinks into the adjuster 30, and the engagement between the piston 20 and the adjuster 30 is released. Then, due to the increase in fluid pressure within the piston 20, the piston 20 moves independently in the direction of the arrow as shown in Fig. 1, and the piston 20 presses against a brake pad (not shown).

[0025] 7 and 8 show the operation of the vehicle braking system 1 when the brake pads are worn. At this time, when the EPB is activated, the spindle 31 rotates until the piston 20 presses the brake pads with a set pressing force (for example, 20 MPa). As a result, as shown in Fig. 7, the position of the tip of the piston 20, which is pushed and moved by the adjuster 30, moves from a position (X1) before the EPB is activated to a position (X2) after the EPB is activated.

[0026] Then, when the EPB is released, as shown in Figure 8, the spindle 31 rotates in the reverse direction, returning the tip position of the piston 20 by a set distance (for example, 1 mm from X2). This returns the tip position of the piston 20 from the position (X2) after the EPB is activated to the position (X3) when the EPB is released. As a result, the tip position of the piston 20 before the EPB is activated shifts from the initial position (X1) to a position (X3) that is shifted toward the brake pad by the amount of brake pad wear (ΔX). In this way, even if the brake pads wear out, the tip position of the piston 20 before the EPB is activated shifts to an appropriate position relative to the brake pads, thereby maintaining responsiveness in brake operation.

[0027] As described above, in the vehicle braking system 1 according to the embodiment of the present invention, when the main brake is activated and the hydraulic pressure of the brake fluid in the cylinder 10 rises, the piston 20 disengages from the adjuster 30, and the piston 20 slides independently in response to the hydraulic pressure, pressing against the brake pads. When the EPB is activated, the piston 20 slides, pressed by the adjuster 30, which moves with the rotation of the spindle 31, and applies a set pressing force to the brake pads. When the EPB is released, the piston 20 and the adjuster 30 engage with each other, and the piston 20 moves back a set distance, following the adjuster 30, which moves with the reverse rotation of the spindle 31. This ensures that gaps are formed among the rotor, brake pads, and piston when the EPB is released, thereby suppressing the drag resistance that was a problem in the past.

[0028] Furthermore, in the vehicle braking system 1 according to the embodiment of the present invention, as the brake pads wear, the position of the tip of the piston 20 before the EPB operation shifts toward the brake pads in accordance with the amount of wear of the brake pads, as described above. This makes it possible to maintain appropriate brake operation responsiveness even when the brake pads wear.

[0029] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configurations are not limited to these embodiments, and the present invention also includes design changes within the scope of the present invention. Furthermore, the above-described embodiments can be combined by utilizing each other's technologies as long as there are no particular contradictions or problems in their purposes, configurations, etc. [Explanation of symbols]

[0030] 1: Vehicle braking device, 2: Electric motor, 10: Cylinder, 11: Piston seal, 12: Seal part, 20: piston, 20a: contact portion, 20b: guide groove, 30: Adjuster, 30a: Female thread, 30b: shoulder portion, 30c: guide projection, 30d: communication hole, 31: spindle, 31a: male thread portion, 31b: shaft portion, 31c: ventilation hole, 32: Seal portion, 33: Lid body, 40: Engagement mechanism, 41: Engagement pin, 42: Engagement groove, 43: Spring

Claims

1. a cylinder supplied with brake fluid; a piston that slides due to hydraulic pressure in the cylinder; an adjuster that is disposed within the piston and is movable along a sliding direction of the piston, and that presses the piston when an electric motor in an electric parking brake rotates forward; a brake device for a vehicle, comprising an engagement mechanism that engages the adjuster and the piston together when the adjuster moves due to reverse rotation of the electric motor, and that releases the engagement between the adjuster and the piston due to an increase in hydraulic pressure in the cylinder.

2. The engagement mechanism includes: an engagement pin protruding from the inside of the adjuster toward the inner surface of the piston; and an engagement groove formed on the inner surface of the cylinder with which the engagement pin engages, 2. The vehicle brake device according to claim 1, wherein the engagement pin sinks into the adjuster when hydraulic pressure in the engagement groove increases.

3. 2. The vehicle brake device according to claim 1, wherein the inside of the adjuster is open to the atmosphere through a vent hole provided in a spindle that transmits the rotation of the electric motor.

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