Valve unit for anti-lock braking system
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- RAICAM DRIVELINE SRL
- Filing Date
- 2021-12-23
- Publication Date
- 2026-06-05
Smart Images
Figure 0007870770000001 
Figure 0007870770000002 
Figure 0007870770000003
Abstract
Description
Technical Field
[0001] The present invention relates to a valve unit for a hydraulic brake system that controls the anti-lock function of wheels.
Background Art
[0002] An anti-lock brake system (ABS) is installed in a vehicle equipped with a hydraulic brake, and prevents skidding or uncontrolled skidding and reduces the effect of sudden stops. This type of system is shown in FIG. 1 where the four wheels of an automobile are functionally opposed to associated sensors S1 - S4 that are fixed for rotation with brake discs E1 - E4 and phonic wheels F1 - F4, or equivalent elements, associated with the brake discs. In a known method, the sensors S1 - S4 detect the rotational speed of the wheels to which they are associated and transmit a signal indicating the rotational speed to an ECU (Electronic Control Unit) that processes the received speed signals, for example, via wiring N1 - N4. Brake calipers G1 - G4 are associated with each brake disc. A master cylinder M actuated by a pedal control unit C actuates the brake calipers via respective hydraulic pipes H1 - H4 in which valve units ABS1 - ABS4 are installed. Each ABS valve unit controls the flow and pressure of the brake fluid towards the associated brake caliper in response to an electrical control signal from the electronic control unit. When the ECU detects a state indicating an inadvertent lock of a wheel, it actuates each ABS valve, reducing the hydraulic pressure of the brake of the affected wheel, and thus reducing the braking force of this wheel, so that as a result, the wheel can rotate while being braked. This process is repeated several times continuously per second during braking to prevent the vehicle from skidding.
[0003] A valve unit has been proposed for a vehicle anti-lock braking system, having a valve body with a discharge port hydraulically connectable to a brake caliper, a suction port hydraulically connectable to a master cylinder, a first hydraulic chamber fluidly communicating with the discharge port, and a second hydraulic expansion chamber. The discharge passage provides fluid communication between the first hydraulic chamber and the expansion chamber, and the bypass passage provides fluid communication between the suction port and the discharge port. The piston is movable along its longitudinal axis within the hydraulic chamber and is actuated by a solenoid controlled by an electronically controlled unit, in opposition to the force of an elastic element. Under normal braking conditions, the force of the elastic element holds the piston in a position where it closes the discharge passage but not the bypass passage. In the braking state of a locked wheel, the piston moves to a position where it closes the bypass passage while clearing the discharge passage, and a portion of the brake fluid is discharged from one of the first hydraulic chambers into the discharge chamber. As a result, the pressure in the caliper decreases, and the wheel is unlocked. [Overview of the Initiative]
[0004] The primary objective of the present invention is to provide an improved and simplified ABS valve unit that can operate more progressively than known ABS valve units. The present invention proposes to solve the aforementioned technical problems by gradually adjusting the temporary removal of brake fluid from the portion of the hydraulic brake circuit, including the brake caliper of the locked wheel, during braking while the wheel is locked. According to one embodiment, the present invention provides a valve unit for a hydraulic brake system that controls the anti-lock function of a wheel, as defined in claim 1. In summary, the ABS valve unit has a single hydraulic chamber configured to receive brake fluid and having a piston that is movable in a single longitudinal direction. The hydraulic chamber has a discharge port for delivering brake fluid to a brake caliper, and a passage through which the hydraulic chamber can receive brake fluid delivered from a master cylinder. The piston has one or more first transverse faces facing the discharge port and defining a first transverse region, and one or more second transverse faces facing away from the discharge port and defining a second transverse region as a whole. The second transverse region is larger than the first transverse region. An axial cavity extends within the piston, establishing fluid communication between the first and second transverse faces. This causes the displacement of the piston toward the discharge port to close the passage and gradually increase the volume available for brake fluid in the hydraulic chamber. [Brief explanation of the drawing]
[0005] To ensure that the present invention is fully understood, the present invention describes several preferred embodiments, which are given by reference to the accompanying drawings, as an example. Figure 1 is a schematic diagram illustrating the operation of the vehicle's antilock braking system. Figures 2 to 6 are longitudinal axial views of the valve unit according to the first embodiment of the present invention under different operating conditions. Figure 7 is a cross-sectional view of a valve unit according to another embodiment, showing the longitudinal axis. Figure 8 is a schematic diagram showing a valve unit of the type shown in Figure 7, related to a vehicle's air suspension system. Figure 9 is a schematic diagram showing the valve unit of Figure 7 related to the vehicle's hydropneumatic suspension system. Figures 10 to 12 are schematic diagrams showing the longitudinal axis cross-section of the valve unit of Figure 7 under different operating conditions. Figure 13 is a cross-sectional view of a valve unit according to another embodiment, showing the longitudinal axis. Figures 14-17 schematically show ABS valve units applied to vehicle suspensions under various operating conditions. Detailed description of the invention
[0006] Referring to Figures 2–6, reference numeral 10 shows the entire ABS valve unit for the wheel anti-lock braking system. The valve unit 10 has an elongated shape in the longitudinal or axial direction, which defines a longitudinal axis x. In this context, terms indicating position and orientation, such as “longitudinal,” “lateral,” and “radial,” should be interpreted with reference to the x-axis. The valve unit 10 has a body 11 that defines the longitudinal direction of operation. In this embodiment, the body 11 has a generally cylindrical tubular shape having a first end 12 and a second end 13 opposite the first end. The end 12 of the main body 11 forms a discharge port (or outlet port) 14 which can be hydraulically connected to the brake caliper G of the wheel brake, and a suction port 17 which can be hydraulically connected to the master cylinder M which is operationally associated with the vehicle's pedal or manual lever operating control unit C. The main body 11 has a single hydraulic chamber 15 that communicates with a discharge port 14 and receives a single piston 18 in the longitudinal direction. The hydraulic chamber 15 forms a first end region 19 (or tip region) with a diameter D1 that is close to the discharge port 14, a second intermediate region 20 with a diameter D2 that is larger than diameter D1, and a third region 21 (or base region) with a diameter D3 that is furthest from the discharge port 14 and is smaller than diameter D1. Correspondingly, the piston 18 has an end portion 22 that is received in the first end region 19 of the hydraulic chamber 15, an intermediate portion 23 that is received in the second intermediate region 20 of the hydraulic chamber 15, and a base portion 24 that is received in the third base region 21 of the hydraulic chamber 15. A pair of end seals 26, 27 are positioned longitudinally adjacent to each other and spaced a short distance apart from one another at the end 22 of the piston 18. The seals 26, 27 slide against the end region 19 of the hydraulic chamber 15. At least one intermediate seal gasket 28 is positioned at the middle portion 23 of the piston 18, engaging with the intermediate region 20 of the hydraulic chamber 15. A base seal 30 is positioned at the base 24 of the piston to engage in a sealing manner with a third region 21 of the hydraulic chamber 15. The piston 18 forms a longitudinal cavity 31 that extends through the piston from the end face 32 of the piston end facing the discharge port 14. The longitudinal cavity 31 communicates with a transverse passage 33 that opens on the side of the piston. The transverse passage 33 faces the intermediate region 20 of the hydraulic chamber 15. The elastic element 34 biases the piston 18 away from the discharge port 14. In the embodiments shown in Figures 2 to 6, the elastic element 34 is received at the end 13 of the valve body 11 opposite to the end 12 having the suction port 17 and the discharge port 14. In the embodiments shown in Figures 2 to 6, the elastic element 34 is formed as a single compression spring that is compressed vertically between the shoulder portion 35 of the main body 11 and the lateral contrast wall 36 that faces the shoulder portion 35 and is positioned vertically spaced away from it. The lateral contrast wall 36 is accommodated with lateral play and is movable vertically within the chamber 38, which is advantageously formed by the main body 11. Rod 37 connects the lateral contrast wall 36 to the piston 18 in the vertical direction. The longitudinal compression of the elastic element 34 biases the lateral contrast wall 36 to the left, thereby pulling the piston 18 to the left via the rod 37. The vertical distance between the lateral contrast wall 36 and the shoulder portion 35 can be adjusted, and the vertical elastic force that causes the elastic element to move the piston 18 away from the release port 14 can be changed. According to one embodiment, the stem 37 can be formed as a threaded stem that engages through a corresponding threaded through-hole 39 formed through a lateral contrast wall 36. The rod 37 may have an enlarged terminal head 40, for example, spherical, with a circular cross-section, which engages with a corresponding recess 41 formed in a portion 24 of the piston 18. An actuator 42, electrically connectable to the electronic control unit (ECU) mounted on the vehicle, is positioned to actuate the valve unit 10. The actuator 42 is operably connected to the piston 18. In the embodiments shown in Figures 2 to 6, the actuator 42 has the function of moving the piston longitudinally toward the discharge port 14. The same actuator 42 also has the function of temporarily changing the elastic force that the elastic element biases the piston 18 toward the discharge port 14. The actuator 42 can actually change the longitudinal position of the lateral contrast wall 36 along the stem 37, and thus adjust the distance between the lateral contrast wall 36 and the shoulder 35, and consequently the length of the elastic body 34 and its compressive force. By rotating the rod 37 in a predetermined rotational direction around its longitudinal axis 37A in a manner that compresses the elastic body 34 more and shortens it longitudinally, the actuator 42 can consequently increase the traction force that moves the piston 18 toward the discharge port 14. Conversely, by rotating the rod 37 in the opposite rotational direction, the elastic body 34 can be depressurized and lengthened longitudinally, thereby reducing the traction force that moves the piston 18 toward the discharge port 14. The rod 37 preferably has a central longitudinal axis 37A that is eccentric with respect to the longitudinal central axis 18A of the piston 18. This prevents the rotation of the rod 37 around its own axis 37A during the step of adjusting the position of the lateral contrast wall 36 from causing undesirable rotation of the piston 18 around its axis 18A, resulting in wear of the seal gasket positioned on the piston 18 and wear acting on the walls of the hydraulic chamber 15. The lateral clearance between the edge of the lateral contrast wall 36 and the chamber 38 is desirable to reduce friction during the longitudinal movement of the piston 18 together with the wall 36. To prevent the rotation applied to the rod 37 from causing screwing or unscrewing with respect to the contrast wall 36, it is preferable that at least a portion of the periphery of the wall 36 has a lateral distance P1 from the shaft 37A that is greater than the minimum lateral distance P2 between the shaft 37A and the inner surface of the chamber 38. Here, the inner surface of the chamber 38 functions as a contrast surface for rotationally locking the lateral wall 36 when the stem 37 rotates. The actuator 42 that rotates the threaded rod 37 has an electric motor controlled by an electronic control unit (ECU, Figure 1) mounted on the vehicle. In the hydraulic chamber 15, the brake fluid present in the first end region 19 closest to the discharge port 14 acts on a circular region of the piston 18 having a circumference of diameter D1, as defined by the seals 26 and 27. The brake fluid present in the first region between the discharge port 14 and the seal 27 acts on the piston 18 with a longitudinal thrust directed to the left in the attached drawing, away from the discharge port 14. The brake fluid contained in the second intermediate region 20 of the hydraulic chamber 15 acts a longitudinal hydraulic thrust on the piston region defined by a ring having an outer circumference of diameter D2 corresponding to the diameter of the second intermediate region 20 of the hydraulic chamber 15, and an inner circumference of diameter D3 corresponding to the diameter of the third region 21 of the hydraulic chamber 15, which is furthest from the discharge port 14. The hydraulic thrust of the brake fluid in the second intermediate region 20 of the hydraulic chamber is directed to the right in the attached drawing and pushes the piston 18 toward the discharge port 14. The diameters D1, D2, and D3 of the three regions 19, 20, and 21 of the hydraulic chamber, and the diameters of the corresponding portions 22, 23, and 24 of the piston 18, are selected such that the region defined by diameters D2 and D3 is an annular region larger than the circular region having diameter D1. Consequently, the hydraulic pressure acting on the piston 18 has a longitudinal resultant force acting on the piston 18 and pushing it toward the discharge port 14. This resultant force will hereafter be defined as the "hydraulic resultant force." The hydraulic resultant force is directed longitudinally, in the opposite direction to the force provided by the elastic element 34 that acts on the piston 18 toward the discharge port 14. The piston 18 has one or more lateral surfaces, defined here as the "first lateral surface," that face the discharge port 14 and define the first lateral surface as a whole equivalent to the region of a circle having the aforementioned diameter D1. The piston 18 also has one or more lateral surfaces, defined here as the "second lateral surface," that face away from the discharge port 14, i.e., in the opposite direction to the first lateral surface. The second lateral surface as a whole defines the second lateral surface as a second lateral surface corresponding to an annular region defined by the outer circumference of diameter D2 and the inner circumference of diameter D3. In the embodiments described herein, the first transverse surface has a radially outermost annular surface given by the piston end face 32, a transverse shoulder 56 of the longitudinal cavity 31, and a radially intermediate annular surface formed by the central circular region 57 at the bottom of the cavity 31. Alternative embodiments of the piston 18 (not shown) can provide the first surface to be differently configured, sized, and / or distributed on the piston surface facing the discharge port 14. For example, the shoulder 56 may be omitted by forming a longitudinal cavity 31 of a certain width.
[0007] In the exemplary embodiments shown in Figures 2 to 6, the second transverse surface has two annular bodies 58, 59 provided by the second intermediate portion 23, which is the widest part of the piston 18. Embodiments of the piston 18 (not shown) may be provided such that the second surface is configured or arranged differently. For example, instead of the two surfaces 58, 59 which are longitudinally offset from each other, a single annular surface in a single transverse geometric plane can be provided. The passage 50 is formed in the valve body 11 and opens to the end region 19 of the hydraulic chamber 15, establishing fluid communication between this chamber and the suction port 17. In the embodiments described herein, for structural reasons to facilitate the construction of the passage 50, the lateral bore 72 is formed in the body 11. The lateral bore 72 is permanently closed by a closure schematically represented by 73. For structural reasons, the main body 11 can be composed of two or more complementary parts, in this example, a right-side portion 11a and a left-side portion 11b. The right-side portion 11a forms the chamber 15, the suction port 17, and the discharge port 14. The left-side portion 11b is hermetically connected to the right-side portion 11a by a gasket 74. Figures 2 and 3 show the valve unit 10 in a normal braking state, i.e., when the vehicle is braking, but the caliper receiving brake fluid from the discharge port 14 does not lock the wheel and therefore does not slip. The brake fluid fills the hydraulic chamber 15 in both the first terminal region 19 and the second intermediate region 20 through the longitudinal cavity 31. Under normal braking conditions, i.e., without reaching a wheel lock state, the resulting hydraulic pressure is less than the longitudinal force exerted by the elastic element 34 due to the moderate hydraulic pressure generated. In other words, the elastic element 34 exerts a force F2 that pulls the piston 18 to the left, exceeding the hydraulic pressure F1 that tends to move the piston 18 to the right. In this state, the length of the elastic element 34 is denoted by L1. The end face 32 of the piston is positioned at a distance E from the end stop 43 near the discharge port 14. Under normal braking conditions, the force of the elastic body 34 maintains the piston 18 in a resting position (or retracted position) shifted to the left, away from the release port 14. In the resting position, the piston 18 can contact the lateral shoulder portion 75 formed by the main body 11. When piston 18 is in the resting position (Figure 3), piston 18 does not block passage 50, allowing brake fluid to pass through passage 50 and to move from suction port 17 to discharge port 14 toward the brake caliper. The anti-lock braking system is not activated. In the braking state of a locked wheel (Figure 4), the vehicle's electronic control unit (ECU) receives a speed signal from a wheel sensor indicating the locking or slipping status of at least one of the wheels. Under these conditions, the electronic control unit transmits an activation signal to the actuator 42 of the valve unit 10. The actuator 42 begins to rotate the rod 37 with respect to the lateral contrast wall 36 in a rotational direction such that the rod moves to the right and the piston 18 begins to move to the right, closer to the discharge port 14. The elastic element 34 does not change its original length L1 and still exerts an elastic force F2. Next, the piston 18 closes the passage 50 (Figure 4), thereby blocking the flow of brake fluid from the master cylinder to the brake caliper through the valve unit. When this occurs, the brake fluid pressure in the hydraulic chamber 15, as well as in the portion of the hydraulic circuit including the discharge port and the brake caliper, remains equal to the brake fluid pressure upstream of the valve unit 10. The actuator 42 continues to rotate the rod 37, causing the piston to move toward the discharge port (Figure 5). At this stage, the total volume available for brake fluid in the hydraulic chamber 15 increases because the area of the piston's lateral surface facing the discharge port 14 (to the right) is smaller than the area of the piston's lateral surface facing away from the discharge port 14 (to the left). Therefore, the displacement of the piston toward the discharge port decreases the volume of the hydraulic chamber 15 on the discharge port side (right side), but at the same time, the displacement of the piston increases the volume of the chamber 15 on the opposite side of the discharge port, and the increase in volume on the left side has a greater absolute value than the simultaneous decrease in volume on the right side. The brake fluid then flows through the piston cavity 31 and can also pass from the right side of the hydraulic chamber toward the left side where more volume is available. As described above, the displacement of the piston 18 toward the discharge port reduces the pressure in the hydraulic chamber. This pressure drop in the hydraulic chamber simultaneously reduces the brake fluid pressure at the branch of the hydraulic circuit extending from the discharge port to the brake caliper. This reduces the braking force acting on the brake caliper, releasing the wheel. The displacement of the piston 18 toward the discharge port is determined by the rotation of the rod 37 provided by the drive unit 42 and by the combined hydraulic force. When the end face 32 of the piston comes into contact with the end of the stroke contact portion 43 (Figure 5), the lateral contrast wall 36 moves further away from the shoulder portion 35 due to the continued rotation of the rod 37, due to the effect of the screw connection between the rod 37 and the lateral wall 36. As a result, the elastic member 34 can be stretched, and its length becomes L2 (L2 > L1). The stretching of the elastic element reduces the elastic force acting on the piston, and consequently reduces both the elastic force and the hydraulic thrust in the balance between them. When the brake caliper is released, the electronic control unit (ECU) controls the actuator 42 by reversing the rotation direction of the rod 37 (Figure 6). Thus, the rod 37 pulls the piston to the left, moving the piston 18 away from the release port 14, and moving the contrast wall 36 toward the release port 14, recompressing the elastic element 34. The passage 50 is opened, and as a result, the master cylinder is once again in fluid communication with the brake caliper. The pressure of the brake fluid supplied to the brake caliper can be increased by repeating the cycle of steps shown in Figures 3 to 6. Preferably, the actuator 42 is rotatably connected to the rod 37, but can be disengaged longitudinally from the rod 37, for example by a spline coupling 44, so as not to increase the inertial mass that is longitudinally integrated with the piston 18. Referring here to Figures 7 to 12, embodiments may provide that the force of the elastic element is assisted by a servo mechanism that utilizes the pressure of a pressurized fluid provided by the vehicle suspension system. In the following description of Figures 7 to 12, only elements that differ from the embodiments in Figures 2 to 6 will be described.
[0008] The elastic element 34 is housed in a longitudinal cavity 31, and in this example, a compression spring is elastically compressed between the shoulder 56 of the piston and the stop portion 43 at the stroke end relative to the piston, which is provided by a hydraulic chamber adjacent to the discharge port 14. The elastic element 34 biases the piston 18 away from the discharge port 14. The valve unit 10 (Figure 7) can be associated with the electromagnetic solenoid 80, thereby electrically actuated to displace the piston 18 longitudinally toward the discharge port 14. The solenoid 80 may also be electrically connected to an electronic control unit (ECU) capable of controlling the rotational speed of the wheel, detecting conditions indicating unintentional wheel locking, and providing a control signal for energizing the solenoid 80. The piston 18 is operatively associated with a solenoid actuator 80 and has an actuating part 61 which is integrated or fixed to the base 24 of the piston 18. The actuating part 61 may be made of a ferromagnetic material. The pressure servo mechanism has a cylindrical auxiliary fluid chamber 62, here defined as an auxiliary part, which surrounds a part 65 of the piston 18 intermediate between the actuating part 61 and the base 24 of the piston. The auxiliary part 62 of the piston has an auxiliary seal 63 which engages slidably and sealingly with the cylindrical wall of the auxiliary fluid chamber 62. The auxiliary seal 63 is attached to the piston 18 at a position further away from the discharge port 14 with respect to the base end seal 30 disposed at the base end portion 24 of the piston 18. An auxiliary suction port 64, which can be fluidly connected to a vehicle suspension system, opens onto the auxiliary fluid chamber 62 at an intermediate position between the auxiliary seal 63 and the proximal seal 30. Pressurized fluid flowing into the hydraulic chamber can be provided, for example, by an airbag 95 of an air suspension (FIG. 8).
[0009] A self-leveling pneumatic suspension system as schematically shown in FIG. 9 is known in the art and will not be described in detail herein. Here, it is sufficient to show that a pair of compressors 90, which control the supply of pressurized air to each airbag 95 using a duct 92 having an inflation valve 93 and a bleed valve 94, dynamically balance the suspension of each wheel (not shown) of the vehicle. According to a possible embodiment, each airbag 95 can supply pressurized fluid (pressurized air in the example of FIG. 8) to the valve unit 10 of the vehicle's ABS system. A pressurized air line 96 supplies the pressurized air from each airbag 95 to each suction port 64 of the ABS valve unit 10. Alternatively, the pressurized suspension fluid may be oil from a hydraulic or hydro-pneumatic suspension system (FIG. 9). For structural reasons, the body 11 may have two or more complementary parts, in this example, the main part 11a and the connection part 11b fixed to the actuating solenoid 80. The main part 11a forms the hydraulic chamber 15, the suction port 17, and the discharge port 14. The connection part 11b, in the example described here, has the auxiliary suction port 64 and can be hermetically coupled to the main part 11a by means of the gasket 74. For assembly reasons, the piston 18 may be expediently composed of several parts that are manufactured separately and then mechanically joined together when the piston is incorporated into the body 11.
[0010] In FIG. 10, the valve unit is shown in the normal braking state. The hydraulic pressure of the suspension system exists in the auxiliary fluid chamber, and as a result, a supplementary force Fsus is generated that biases the piston 18 away from the discharge port 14 and cooperates with the force Fspr provided by the elastic element 34. In the normal braking state, that is, if the locked state of the braked wheel is not reached, the hydraulic resultant force FBR is not stronger than the longitudinal coupling forces FSUS + FSPR exerted by the suspension and the elastic element 34 (Fsus + Fspr > Fbr). For this reason, in the normal braking state, the piston 18 is arranged in the rest position (or the retracted position) to the left, away from the discharge port 14. In the rest position, the piston 18 abuts against the lateral shoulder 75 formed by the body 11. In the rest position (FIG. 10), the piston 18 does not obstruct the passage 50 and allows the brake fluid to pass directly through it from the suction port 17 to the discharge port 14 towards the brake caliper. The antilock braking system is not operating.
[0011] Figure 11 shows the valve unit during braking stages where the brake fluid pressure in the brake circuit increases within the brake circuit, and therefore within the hydraulic chamber 15 of the ABS valve unit 10. Therefore, due to the shape of the piston 18, the hydraulic force Fbr increases as the brake fluid pressure in the hydraulic circuit of the brake system increases. The auxiliary force Fsus applied to the piston 18 can be dynamically changed by load transmission between braking stages. When the combined hydraulic force Fbr exceeds the sum of the auxiliary force and the elastic element, Fbr > (Fsus + Fspr), the piston 18 moves to the right and closes the passage 50 (Figure 11). The brake fluid pressure acting on the brake caliper cannot be increased further.
[0012] In a locked-wheel braking state (Figure 12), the vehicle's electronic control unit (ECU) receives a speed signal from a wheel sensor indicating the locking or slipping condition of at least one wheel. Under these conditions, the ECU energizes a solenoid actuator 80 that transmits an additional force Fsol to the piston 18, causing the piston to move further to the right. As the piston moves to the right, the area of the right cross-section of the hydraulic chamber 15 (facing the discharge port 14) is smaller than the area of the left cross-section, so the brake fluid in the hydraulic chamber 15 passes through the left longitudinal cavity 31, which gradually widens. As a result, the increased volume available to the brake fluid reduces the pressure acting on the brake caliper circuit, thus reducing the braking torque acting on the wheel, and the wheel is released. When the brake caliper is released, the electronic control unit (ECU) cuts off power to the solenoid, and the pressure of the pressurized fluid from the elastic element 34 and the suspension returns the piston 18 to the left, away from the discharge port 14. The passage 50 is opened, thereby allowing the master cylinder to communicate with the brake caliper again. The pressure of the brake fluid supplied to the brake caliper can be increased by repeating the cycle of steps shown in Figures 9 to 12. It can be observed that as the brake fluid pressure increases, the combined hydraulic force Fbr increases, but the force Fsol generated by the actuating solenoid increases in order to move the piston and reduce the pressure acting on the brake.
[0013] Generally, it will be understood that during braking, the load acting on the front wheels increases, while the rear wheels are released. Therefore, even at very high braking pressures, a higher force is needed to hold the piston in the ABS valve in the released position. For this reason, during braking, the front wheel airbags of a vehicle with pneumatic suspension will be compressed more than the rear wheel airbags, and the increase in air pressure inside them will generate an increase in the Fsus force. This allows a greater braking torque to be applied to the heavier-loaded front wheels, thereby providing the advantage of higher grip. A lower-intensity force Fsus is applied to the ABS valve of the rear wheels, which are lighter and therefore more susceptible to sliding during braking, thereby reducing the risk of wheel lock due to the decrease in rear wheel grip during braking. The valve unit described herein will be understood to allow the volume of the hydraulic circuit on the brake caliper side to be gradually increased, and therefore the pressure within the brake caliper to be gradually decreased. The current valve unit offers better performance than conventional valve units that have a second hydraulic expansion or storage chamber, which requires a pump to replenish the part of the circuit by returning the fluid temporarily removed from the caliper, as the pressure is rapidly released at the moment the passage is opened and brake fluid is removed from the part of the brake circuit having the caliper.
[0014] Figure 13 shows a simplified embodiment as an alternative to Figures 2-6 and Figures 7-12. The piston actuation device has an electromagnetic solenoid 80 which is electrically actuated by an electronic control unit (ECU) and moves the piston 18 longitudinally toward the discharge port 14. The elastic element 34 is received in the longitudinal cavity 31 and is elastically compressed between the shoulder 56 of the piston and the hydraulic chamber adjacent to the discharge port 14, and the contact portion 43 which acts as the end of the piston's stroke. The elastic element 34 biases the piston 18 away from the discharge port 14. The piston 18 is operationally associated with the solenoid 80 and has an operating (ferromagnetic?) part 61 that is integrated with or fixed to the base 24 of the piston 18. The operating part 61 may have a ferromagnetic material.
[0015] In Figure 13, the valve unit is shown in the normal braking state. In this state, the force provided by the elastic element 34 is greater than the combined hydraulic force. The piston 18 is positioned to the left, away from the discharge port 14, in a resting position (or retracted position) in contact with the lateral shoulder 75 formed by the body 11. In the resting position, the piston 18 does not close the passage 50, allowing brake fluid to pass from the suction port 17 towards the brake caliper and then to the discharge port 14. The anti-lock braking system is not activated. During braking, due to the shape of the piston 18 described above, the hydraulic force increases as the pressure of the brake fluid in the hydraulic circuit of the brake system increases. When the hydraulic force exceeds the force of the elastic element, the piston 18 moves to the right, closing the passage 50 (as described with reference to Figures 10 and 11). The brake fluid pressure acting on the brake caliper cannot be further increased. In the braking state of a locked wheel, the electronic control unit (ECU) biases the actuating solenoid 80, which transmits additional force to the piston 18, to move the piston further to the right. The area of the right cross-section (discharge port 14 side) of the hydraulic chamber 15 becomes smaller than the area of the left cross-section as the piston moves to the right. The brake fluid in the hydraulic chamber 15 passes through the left longitudinal cavity 31 and has a larger volume. The volume on the left side of the hydraulic chamber is larger than the volume on the right side. The hydraulic chamber is simultaneously depressurized. Therefore, the displacement of the piston toward the discharge port increases the volume of the hydraulic chamber 15 and the hydraulic circuit downstream of the ABS valve. The unit includes a locked brake caliper. As a result, the increased volume available for brake fluid reduces the pressure acting on the brake caliper circuit. This reduces the braking torque acting on the wheel and unlocks the wheel. When the brake caliper is released, the electronic control unit (ECU) cuts off power to the solenoid, causing the elastic element 34 to move the piston 18 away from the release port 14. The passage 50 is opened again, thereby allowing the master cylinder to re-establish fluid communication with the brake caliper. The pressure of the brake fluid supplied to the brake caliper can be increased by repeating the aforementioned operating cycle. An alternative embodiment may be provided such that an auxiliary force Fsus generated by the suspension is transmitted to the piston 18 by a mechanism connected to the suspension arm, thereby utilizing the gravitational force acting on the suspension.
[0016] In the examples shown in Figures 14-17, a spring 66 connected to a suspension arm 67 by a linkage mechanism 70 is associated with a piston 18 of an ABS valve unit to transmit an increased auxiliary force Fsus when the vertical load on the suspension increases. The valve unit 10 is fixed to a bracket 68 that is integrated with the vehicle body 69. When the load acting on the suspension is low (Figure 16), the auxiliary force transmitted to the vertically oriented piston 18 is low. Conversely, when the load acting on the suspension is high (Figure 17), the auxiliary force Fsus transmitted to the piston 18 increases. Advantageously, the control of the actuating solenoid is performed using PWM (Pulse Width Modulation), which changes the ratio of the on-time to the off-time of the solenoid coil during its rapid on / off switching.
[0017] Figure 1 illustrates a system having separate ABS valves for each wheel, but in some embodiments, the ABS valves for some or all of the vehicle may be physically grouped together or enclosed within a single valve body. While certain embodiments of the present invention are disclosed, it should be understood that such disclosures are for illustrative purposes only and do not limit the present invention in any way. Various modifications will be apparent to those skilled in the art from these examples. The scope of the present invention is limited only by the appended claims.
Claims
1. A valve unit (10) for a vehicle antilock braking system, The valve unit is A hydraulic chamber (15) configured to receive brake fluid, having a discharge port (14) for supplying brake fluid to a brake caliper (G), and a passage (50) for allowing brake fluid to flow from a master cylinder (M) into the hydraulic chamber (15), Within the aforementioned hydraulic chamber (15), there is a piston (18) that is movable in the vertical direction, One or more first lateral surfaces facing the discharge port and defining the first lateral region as a whole, One or more second lateral surfaces that face away from the discharge port (14) and define a second lateral surface as a whole that is larger than the first lateral region, A longitudinal cavity (31) extending within the one piston (18) establishes fluid communication between the first transverse surface and the second transverse surface. Those that possess, It has, The displacement of the piston (18) toward the discharge port (14) closes the passage (50) and increases the volume available for the brake fluid in the hydraulic chamber. Valve unit.
2. A valve unit according to claim 1, The hydraulic chamber (15) is A first region (19) is located near the discharge port (14) and has a first diameter (D1), A third region (21) located furthest from the discharge port (14) and having a third diameter (D3) smaller than the first diameter (D1), A second region (20) is located midway between the first region (19) and the third region (21) and has a second diameter (D2) that is larger than the first diameter (D1), Forming, The piston (18) is In the first region (19) of the hydraulic chamber, a first portion (22) slides while sealing, An intermediate portion (23) that slides while sealing the second region (20) of the hydraulic chamber, A third portion (24) that slides while sealing the third region (21) of the hydraulic chamber, It has, The first lateral surface has a circular region having the first diameter (D1), The second lateral surface has an annular region having an outer circumference with a diameter corresponding to the second diameter (D2) and an inner circumference with a diameter corresponding to the third diameter (D3). Valve unit.
3. In the valve unit according to claim 1 or 2, further, At least one elastic element (34) exerts an elastic force that moves the piston (18) away from the discharge port (14), A valve unit having
4. In the valve unit according to claim 1, 2, or 3, further, An actuator (42, 80) that can be electrically connected to an electronic control unit (ECU) mounted on the vehicle, and which moves the piston (18) vertically toward the discharge port (14) in response to an electrical signal from the electronic control unit, A valve unit having
5. A valve unit according to claim 4, The valve unit is The one hydraulic chamber (15) and the valve body (11) which forms a lateral shoulder portion (35) facing away from the discharge port (14), A horizontal contrast wall (36) facing the aforementioned horizontal shoulder portion (35) and positioned vertically at intervals therefrom, A vertical rod (37) and an elastic element (34) connect the lateral contrast wall (36) to the piston (18) in the vertical direction. It has, The elastic element (34) has at least one compression spring that is compressed in the longitudinal direction between the lateral contrast wall (36) and the lateral shoulder portion (35), The actuator (42) is configured to rotate the vertical rod (37) about the vertical axis (37A), thereby adjusting the vertical distance between the horizontal contrast wall (36) and the piston (18). Valve unit.
6. A valve unit according to claim 4, The aforementioned operating device is The electronic control unit (ECU) has an actuation solenoid (80) that can be electrically operated, The piston (18) is Having an actuation part (61) associated with the actuatable actuation solenoid (80), Valve unit.
7. In the valve unit according to claim 2, The operating part (61) of the piston (18) is The third portion (24) of the piston is integrated with or fixed to it. Valve unit.
8. In the valve unit according to claim 3, The elastic element (34) is The piston is received in the longitudinal cavity (31) and is elastically compressed between the shoulder (56) of the piston and the end stop (43) for the piston, which is provided by the hydraulic chamber (15) adjacent to the discharge port (14). Valve unit.
9. In a valve unit according to any one of claims 6 to 8, The valve unit is The vehicle suspension is configured to transmit an auxiliary force (Fsus) to the piston (18), The aforementioned auxiliary force is, The piston is biased so as to move away from the discharge port (14) in the vertical direction. Valve unit.
10. A valve unit according to claim 9, A pressure servo mechanism operably associated with the piston (18), It has, The aforementioned servo mechanism is A cylindrical auxiliary fluid chamber (62) is integrated with the valve body (11) of the valve unit (10), and the auxiliary fluid chamber surrounds the auxiliary portion (65) of the piston. An auxiliary suction port (64) that opens into the auxiliary fluid chamber (62) and is fluidically connectable to the vehicle's suspension system in order to introduce pressurized fluid of the vehicle's suspension system into the auxiliary fluid chamber (62), An auxiliary seal (63) that seals and engages with the cylindrical wall of the auxiliary fluid chamber (62), wherein the auxiliary seal (63) is positioned on the piston (18) and is located further away from the discharge port (14) than the auxiliary suction port (64), A valve unit having the following features.
11. A valve unit according to claim 10, The pressurized fluid is pressurized air coming from the airbag (95) of the pneumatic suspension system, or the pressurized fluid is a hydraulic or hydropneumatic suspension system. Valve unit.
12. A valve unit according to any one of claims 1 to 11, It does not have a second hydraulic expansion chamber that can be fluidly connected to the one hydraulic chamber (15) by a flow path that can be closed by the piston (18), Valve unit.
13. A valve unit according to claim 9, The aforementioned piston is When the load on the suspension increases, the vehicle's suspension is mechanically connected to the suspension such that it receives thrust away from the release port (14) from the suspension. Valve unit.
14. A valve unit according to claim 2, The first lateral surface is, The outermost radial annular surface provided by the piston end face (32), and the central circular region (57) at one end of the cavity (31) furthest from the end face (32), Valve unit.
15. A valve unit according to claim 14, The first lateral surface is, Having a radial intermediate annular surface provided by the lateral shoulder portion (56) of the longitudinal cavity (31), Valve unit.
16. A valve unit according to claim 2, The second lateral surface is, The annular shape (58, 59) provided by the intermediate portion (23) of the piston (18) has one or two lateral surfaces, Valve unit.