Reverse modulating electrohydraulic brake valve with adjustable pressure reducing valve

Abstract

An electrohydraulic valve is disclosed that includes a pressure reducing valve in a single unitary valve body. In one example, the valve is a reverse modulating valve whose body has an output port (B), a pressure supply port (P), and a tank port (T). The electrohydraulic valve is configured as a spool valve having a return spring, a feedback pin, and a proportional solenoid, wherein the proportional solenoid is arranged opposite the return spring and the feedback pin. An externally adjustable pressure reducing valve is located between the pressure supply port (P) and the electrohydraulic spool valve. Above a current threshold, increasing current to the solenoid proportionally reduces the pressure at the output port (B). An example of a braking system including the valve is also disclosed.

Description

Technical Field

[0001] The present disclosure relates generally to electrohydraulic brake valves (EBVs), and more particularly to reverse-modulating electrohydraulic brake valves including an adjustable pressure reducing valve (PRV). Background Art

[0002] In a conventional hydraulic brake system, such as a hydraulically applied spring-release (HASR) brake system, pressing the brake pedal applies a force on a piston in a master cylinder, causing hydraulic fluid to flow from a fluid reservoir and an increase in downstream pressure, ultimately forcing the brakes to engage. For example, pressure may be applied to a caliper, which creates a clamping force to engage the brake pads on a brake rotor, or pressure may be applied to a wheel cylinder, which forces the brake shoes outward to engage the inside of a rotating drum. Upon releasing the brake pedal, the piston in the master cylinder returns to a resting position, releasing the hydraulic pressure to release the brakes. Other brake systems utilize a spring-applied hydraulic-release (SAHR) method, in which a spring mechanically applies the brakes, and hydraulic brake pressure is used to counteract the spring force in normal operation to allow the wheels to rotate freely.

[0003] Whether used in a HASR or SAHR braking system, hydraulic brake pressure can be applied and modulated in a variety of ways. Instead of using a master cylinder to generate brake pressure, many off-highway vehicles utilize a three-way proportional spool valve to modulate supply pressure (P) to brake pressure (B). The spool valve can be actuated directly by mechanical means, hydraulically via a pilot valve, or electromechanically via a solenoid. In an inverse modulating valve, brake pressure is inversely proportional to the force applied to it. Summary of the invention

[0004] The present disclosure relates to electrohydraulic brake valves, and in particular, a reverse modulating electrohydraulic brake valve (EBV) that includes an adjustable pressure reducing valve (PRV) in a single valve body. The PRV allows the system supply pressure to be modulated downward to a desired maximum brake pressure, which is the default pressure that would be applied downstream of the brake pressure port (B) when no current is applied to the solenoid. As the current increases, the brake pressure decreases. In an example embodiment, the EBV is configured as a dual spool valve with a solenoid, where the PRV is externally adjustable. When the solenoid is not energized, the valve simply acts as a pressure reducing valve (PRV), which can be set with a discrete adjustment screw. When the solenoid is activated and after an offset or deadband current is reached, the output (brake) pressure is modulated downward to zero, inversely proportional to the increase in solenoid current.

[0005] The features and advantages described herein are not all-inclusive, and in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, description, and claims. In addition, it should be noted that the language used in the specification is selected primarily for readability and instructional purposes, and does not limit the scope of the disclosed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a graph of brake pressure versus current showing a modulation curve for a variation of a direct operated, reverse modulating electro-hydraulic brake valve according to some embodiments of the present disclosure.

[0007] Figure 2 is a graph of brake pressure versus current for two different inlet pressures provided to an inverse modulating electro-hydraulic brake valve according to another embodiment of the present disclosure.

[0008] Figure 3A and Figure 3B A perspective view and a top view, respectively, of a reverse-modulating electro-hydraulic brake valve with an integrated adjustable PRV, according to an embodiment of the present disclosure, are shown.

[0009] Figure 4 A reverse-modulating electro-hydraulic brake valve with an integrated adjustable pressure reducing valve is schematically illustrated according to an embodiment of the present disclosure.

[0010] Figure 5 A brake system including a combination valve according to an embodiment of the present disclosure is schematically illustrated.

[0011] The accompanying drawings depict various embodiments of the present disclosure for purposes of illustration only. Numerous variations, configurations, and other embodiments will be apparent from the following detailed discussion. DETAILED DESCRIPTION

[0012] An electrohydraulic brake valve (EBV) is disclosed that includes an adjustable pressure reducing valve in a single valve body. In one example embodiment, the EBV is a reverse modulating EBV configured as a dual spool valve with a solenoid. When the solenoid is not energized, the valve functions as a pressure reducing valve (PRV), wherein the PRV is adjustable by a discrete adjustment screw. When the solenoid is activated with a current greater than an offset current or a deadband current, the output pressure to the brake is modulated down to zero inversely proportional to the increasing solenoid current.

[0013] Advantageously, the proposed reverse-modulating electrohydraulic brake valve provides more consistent performance in reverse-modulating applications compared to existing approaches. For example, the integrated PRV alleviates the difficulties associated with requiring a constant supply pressure for optimal performance. Adjustability allows for repeatable and predictable brake pressure output without current to the solenoid, thereby avoiding downstream overpressure that could cause damage to the brake system.

[0014] Among other applications, an EBV as variously disclosed herein may be used in a hydraulically applied spring-release (HASR) braking system. For example, in a HASR braking system, a solenoid may be activated during normal vehicle operation to allow the wheels to spin freely. As a failsafe, such as in the event of a loss of electrical power, the brakes are applied at a preset pressure via an integrated adjustable PRV to slow the vehicle to a stop. Alternatively, in normal operation, when voltage is available, the vehicle may be programmed to electro-hydraulically apply / modulate the brakes for remote or autonomous operation, accident avoidance, downhill descent, and other applications. Many variations and advantages will be apparent in light of this disclosure. Overview

[0015] One type of direct-operated, reverse-modulating electrohydraulic brake valve (e.g., referred to as an EBV-R valve) has a bias spring that provides a spring force that opposes the hydraulic pressure acting on the reaction area. The spring force corresponds to a set maximum brake pressure. A force balance is created between the bias spring force and the hydraulic pressure acting on the reaction area. The valve also includes a solenoid that provides a proportional reaction force on the spring. As the current to the solenoid increases, the reaction force increases, thereby reducing the net bias spring force and modulating the brake pressure proportionally downward to zero. This type of brake valve is designed to maintain a preset output pressure and is not significantly affected by changes in supply pressure as long as the supply pressure is greater than the set output pressure.

[0016] Figure 1Graphs of pressure versus current for five variants of the EBV-R are shown in . The five variants differ by varying the bias spring force and / or the reaction area. For each variant, the brake pressure decreases in proportion to the increasing solenoid current for currents above a threshold current of approximately 0.1 A. Note that the slope of the reduction in pressure is different for each variant. In order to achieve zero brake pressure at approximately the same solenoid current, a different slope is required. In this example, the brake pressure decreases to zero at approximately 1.3 amps for each variant. However, one challenge is that this type of valve has difficulty maintaining its set pressure when no power is applied to the solenoid. This is due to its additional internal components (compared to other valves) contributing to the overall friction within the valve without the benefit of dithering. This condition can result in pressure oscillations of varying amplitude and frequency of the spool at the output port of the EBV-R when trying to find a consistent modulation position (also known as pressure oscillation) and can lead to difficulties in setting the pressure at the factory.

[0017] Another type of electrohydraulic brake valve, such as the solenoid-type EBV-A valve, is a direct-operated electrohydraulic brake valve designed for use in anti-lock brake systems (ABS). This valve includes a bias spring and a solenoid that act in opposition to each other. When no power is supplied to the solenoid, the valve is fully open between the inlet pressure and the brake port. In this case, the brake pressure is equal to the inlet pressure. When current is applied to the solenoid and exceeds a current threshold or deadband value, the solenoid force increases in opposition to the bias spring. For currents above the threshold, the brake pressure decreases proportionally and inversely to the increasing solenoid current.

[0018] In the EBV-A brake pressure versus current diagram, for example Figure 2 , the brake pressure is equal to the supply pressure until a threshold current value of approximately 0.5 A, at which point the brake pressure decreases in proportion to the increasing solenoid current. For currents above the threshold, the brake pressure decreases at the same rate, regardless of the supply pressure. That is, for currents above the threshold, the slope of the line is independent of the supply pressure. Therefore, the useful range of solenoid current is directly affected by the inlet pressure, where different supply pressures will require different solenoid currents to achieve zero brake pressure. This valve does not have the challenges of pressure oscillations discussed above, but the valve requires a consistent supply pressure to achieve consistent brake pressure, and also requires achieving zero brake pressure at a given solenoid current.

[0019] To address the above challenges, the present disclosure provides a dual spool valve with a solenoid. In one example, an adjustable pressure reducing valve (PRV) is combined with a reverse modulating electro-hydraulic brake valve (EBV) in a single valve body. The adjustable PRV and EBV can be arranged side by side in the valve body, such as a dual spool valve. In another example, the PRV can be in the form of a cartridge valve installed into an EBV block. For example, such a valve can be configured for an electro-hydraulic reverse modulating braking system. One advantage of the combined valve is that the performance benefits of EBV-A can be achieved, but the steady-state brake pressure at zero current is not significantly affected by changes in supply pressure.

[0020] For example, due to the relatively high threshold current required to begin pressure reduction (e.g., 0.5A vs. 0.1A), the combination valve provides more accurate pressure modulation with less hysteresis across its entire pressure range compared to the EBV-R valve. Also, the combination valve benefits from lower overall friction within the valve. In addition, the dither amplitude of the valve is proportional to the total solenoid current, which can be very helpful in producing smooth and predictable pressure modulation.

[0021] Combination valves constructed in accordance with the present disclosure advantageously enable the EBV portion of the valve to be a straight-through valve until reverse modulation is desired. For example, when no current is applied to the solenoid, the output pressure (B) of the combination valve is not significantly subject to changes in supply pressure because the spool is open between the output of the PRV and the brake port, in contrast to an EBV-A valve that produces a brake pressure output equal to the supply pressure.

[0022] Combination valves constructed in accordance with the present disclosure advantageously enable the valve to produce consistent brake pressures due to spool position and component configuration by reducing the overall friction acting thereon. For example, when the spool in the EBV portion of the combination valve is open between the output port of the PRV and the brake port, the output pressure (B) of the combination valve should be stable and predictable, in contrast to an EBV-R spool that is in a modulating position and subject to pressure oscillations.

[0023] The PRV portion of the combination valve advantageously enables adjustability of steady-state brake pressure. That is, the combination valve can be adjusted for a wide range of applications. This functionality in a single valve body eliminates the need for additional components, thereby simplifying the brake system and installation. In addition, the combination valve allows each valve to be adjusted individually, which can be very beneficial in applications with multiple valves operating at the same supply pressure. Including a PRV can also eliminate one or more potential leak points in the hydraulic line. Example Embodiments

[0024] Figure 3A and Figure 3BA perspective view and a top view, respectively, of a combination valve 100 having an electrohydraulic brake valve 110 (or "EBV" 110) and an integrated adjustable pressure reducing valve 140 in a single housing 112 in accordance with an embodiment of the present disclosure are shown. The valve 100 includes a housing 112 defining a tank (T) 114 port, a supply pressure inlet port (P) 116, and a brake pressure output port (B) 118. It should be understood that the various port plugs 113 are intended to be permanent and not to be removed. A proportional solenoid 130 is operably connected to the housing 112 and is arranged to engage a valve bias or return spring 104 (not visible; in FIG. 1 ). Figure 4 130). In some embodiments, the solenoid 130 includes a manual override (not shown). The solenoid 130 includes a solenoid coil and a solenoid conduit held together by a coil nut 132. The solenoid 130 can be operated with a supply voltage of 12 VDC or 24 VDC, such as by replacing the solenoid coil with a coil of different resistance. An electrical connector 150 is also provided for connecting power to the solenoid 130.

[0025] Figure 4 The combined valve 100 according to an embodiment of the present disclosure is schematically shown. FIG. 3A to FIG. 3B As described, the valve 100 combines an electrohydraulic valve (EBV) 110 and a pressure reducing valve (PRV) 140 in a single housing. Therefore, the combined valve 100 can be referred to as a single valve. In this example, the EBV 110 is configured as a three-port three-position proportional spool valve, in which the valve core 111 can be continuously moved between a first position 1, a second position 2, and a third position 3. For clarity of description, ports 101, 102, 103 are shown in FIG. Figure 4 Only the first position 1 is marked in the figure. The EBV 110 has a return spring 104 and an internal pilot pressure 105, which are arranged to act oppositely to each other on the reaction area. The internal pilot pressure 105 is the pressure difference between the pressure from the PRV (at port 101) and the pressure at the brake pressure outlet port B118. The solenoid 130 is arranged to act opposite to the return spring 104, thereby providing a second force or modulating force to counteract the spring force. The spool 111 can be continuously moved between three positions 1, 2, 3 based on the balance of forces acting on the spool 111 by the return spring 104, the internal pilot pressure 105, the pilot pressure 106 from the PRV 140 acting directly on the spool 111, and the proportional solenoid 130. When no current is supplied to the proportional solenoid 130, the spool 111 is in position 1, as shown in FIG. Figure 4 When current is applied to the solenoid 130, the solenoid 130 reduces the pressure to the brake port 118 as long as the current is above the threshold, so that increasing the current above the threshold proportionally reduces the output pressure, as shown in FIG. Figure 2In some embodiments, the threshold current is 0.4 A to 0.6 A, or about 0.5 A. Other values ​​of the threshold current may be used, depending on the return spring 104, the operating voltage, and other factors and as deemed appropriate for a particular application.

[0026] In some embodiments, the EBV 110 has a connecting passage 106 between the first port 101 and one end of the EBV spool 111. The force of the hydraulic pilot pressure from port 101 on the spool 111 is shown by 107. The EBV has a feedback pin (not shown) within the spool that creates the reaction area described above, thereby facilitating the opposing pilot pressure. As will be appreciated, the diameter of the feedback pin affects the rate of pressure reduction as the current to the proportional solenoid 130 increases.

[0027] The adjustable pressure reducing valve 140 is arranged between a pressure input port (P) 116 on the housing 112 and the first port 101 of the EBV 110. The pressure from the supply pressure port 116 is received at an inlet port 143 of the PRV 140. The pressure reducing valve PRV 140 has a PRV regulator 142 configured as a variable spring, for example, wherein the PRV regulator 142 is operable to regulate (e.g., reduce) the hydraulic pressure delivered from an output port 144 of the PRV 140 to the EBV 110. Thus, the PRV 140 functions as a regulator to deliver a desired supply pressure to the EBV 110.

[0028] In some embodiments, the PRV 140 has a sensing line 146 configured to sense pressure at the PRV output port 144 or other location downstream thereof. The PRV 140 is typically opened by the pressure at the PRV output port 144 until a set delivery pressure. If the delivery pressure at the PRV output port 144 is greater than the set value, the PRV 140 reduces the pressure to the set level. Excess pressure can be discharged to the tank (T) 114 via the PRV tank port 145.

[0029] In the first position 1, such as Figure 4 As shown, for example, the EBV 110 is open between the first port 101 and the third port 103, where the spool 111 directs the supply pressure set by the PRV 140 to the brake port (B) 118. Therefore, the brake pressure at the brake port (B) 118 is the same as the reduced supply pressure at the PRV outlet port 144. In the second position 2, the valve is closed, or also referred to as the modulation position. In the third position 3, the third port 103 is open to the second port 102, where the brake pressure is discharged to the tank (T) 114.

[0030] Figure 5A brake system 200 incorporating the combination valve 100 according to an embodiment of the present disclosure is schematically illustrated. The brake system 200 includes a brake rotor 210 engaged by a caliper 212 in response to pressure at the brake pressure outlet port 118 .

[0031] In use, PRV 140 can provide consistent pressure to the spool 111 of the EBV so that the pressure can be repeatedly modulated to zero under consistent solenoid current. For example, the hydraulic system may have a supply pressure of 3000 PSI, and the desired input pressure of the EBV 110 is 1500 PSI. The PRV reduces the pressure to a set value for delivery to the EBV 110. As long as the system supply pressure is above 1500 PSI, the EBV 110 can modulate the pressure to zero under the same solenoid current. In a system with a single hydraulic supply pressure for multiple components, for example, the combination valve 100 can be set to provide consistent performance. Unlike the combination of a separate EBV and PRV, the combination valve 100 simplifies the pipe connections, reduces costs, and potentially eliminates the need for a pressure reducing valve for each component in the hydraulic system. For a hydraulic brake system, the combination valve 100 achieves the correct delivery pressure to the brake by setting the PRV for a given application.

[0032] The combination valve 100 can be configured for use in a conventional hydraulically applied, spring released (HASR) brake system, a spring applied hydraulically released (SAHR) brake system, or other hydraulic systems that require a maximum set pressure with zero current and have a pressure modulation inversely proportional to current (after a current threshold is reached). Many variations and embodiments will be apparent in light of this disclosure. Additional Example Embodiments

[0033] The following examples relate to further embodiments from which numerous arrangements and configurations will be apparent.

[0034] Example 1 is a single body valve, which includes a body having an output port, a pressure supply port and a tank port. An electrohydraulic spool valve in the body has a return spring, a pressure feedback pin and a proportional solenoid, wherein the proportional solenoid is arranged opposite to the return spring and the pressure feedback pin. The pressure reducing valve is located between the pressure supply port and the spool valve.

[0035] Example 2 includes the unitary valve of Example 1, wherein the pressure reducing valve is externally adjustable.

[0036] Example 3 includes the unit valve of any of Examples 1 or 2, wherein the proportional solenoid is electronically controlled.

[0037] Example 4 includes the monolithic valve of any of Examples 1-3, wherein the electrohydraulic spool valve is capable of moving within a continuous range to meter hydraulic communication between a first port, a second port, and a third port, wherein the first port is in communication with an output port of a pressure reducing valve, the second port is an output port of the monolithic valve, and the third port is in communication with the tank port.

[0038] Example 5 includes the unitary valve of Example 4, wherein the first position of the electrohydraulic spool valve is an open position in which the first port opens to an output port of the body.

[0039] Example 6 includes the single body valve of any of Examples 1-6, wherein, when no current is applied to the proportional solenoid, the electrohydraulic spool valve allows the outlet pressure from the pressure reducing valve to be present at the output port of the body, and when the current applied to the proportional solenoid is greater than a threshold current, the pressure at the output port decreases proportionally and inversely to the current applied to the proportional solenoid.

[0040] Example 7 includes the single body valve of Example 6, wherein the threshold current is from 0.4A to 0.6A.

[0041] Example 8 includes the unit valve of any of Examples 1-7, wherein when the current applied to the proportional solenoid is above the threshold current, the rate of pressure reduction at the output port is determined at least in part by a diameter of a pressure feedback pin.

[0042] Example 9 is an electrohydraulic brake valve comprising a body having a brake port, a pressure supply port and a tank port. The valve core is slidably retained in the body to meter the hydraulic communication between the first port, the second port and the third port. The return spring provides a spring force on the valve core in a first direction, and the pressure feedback pin is arranged to provide a return force on the valve core opposite to the spring force. The proportional solenoid is constructed and arranged to provide a modulation force opposite to the spring force when fully energized. The pressure reducing valve is located between the pressure supply port and the first port. The valve core can move in a continuous range of positions between a first position where the first port opens to the third port, a modulation position and a third position where the second port opens to the third port in response to a balance of the spring force, the return force and the modulation force.

[0043] Example 10 includes the electro-hydraulic brake valve of Example 9, wherein the pressure reducing valve is externally adjustable.

[0044] Example 11 includes the electrohydraulic brake valve of any of Examples 9 or 10 configured as a reverse modulating electrohydraulic brake valve, wherein the proportional solenoid is configured to increase the modulation force in proportion to increasing the current above a predefined current threshold.

[0045] Example 12 includes the electrohydraulic brake valve of Example 11, wherein the current threshold is at least 0.4A.

[0046] Example 13 includes the electrohydraulic brake valve of any of Examples 9-12, wherein the modulating force is zero when no current is applied to the proportional solenoid.

[0047] Example 14 includes the electro-hydraulic brake valve of any of Examples 9-13, wherein the proportional solenoid is electronically controlled.

[0048] Example 15 is a brake system comprising the electro-hydraulic brake valve of any one of Examples 9-14 or the monolithic valve of any one of Examples 1-8.

[0049] Example 16 includes the brake system of Example 15 configured as a spring applied hydraulic release brake system.

[0050] Example 17 includes the brake system of Example 15 configured as a hydraulically applied spring released brake system.

[0051] Example 18 is a motor vehicle comprising the braking system of any one of Examples 15-17.

[0052] Example 19 includes the motor vehicle of Example 18, wherein the motor vehicle is configured as an off-highway vehicle.

[0053] The foregoing description of example embodiments has been presented for purposes of illustration and description. This is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. In light of this disclosure, many modifications and variations are possible. It is intended that the scope of the disclosure is not limited by this detailed description, but rather by the appended claims. Future applications claiming priority to the present application may claim the disclosed subject matter in different ways, and may generally include any set of one or more limitations as variously disclosed or otherwise shown herein.

Claims

1. A single valve, comprising: a body having an output port, a pressure supply port, and a tank port; an electrohydraulic spool valve in the body, the spool valve having a return spring, a pressure feedback pin, and a proportional solenoid, wherein the proportional solenoid is arranged opposite the return spring and the pressure feedback pin; and A pressure reducing valve is provided between the pressure supply port and the spool valve.

2. The single body valve according to claim 1, wherein: The pressure reducing valve is externally adjustable.

3. The single body valve according to claim 1, wherein: The proportional solenoid is electronically controlled.

4. The single body valve according to claim 1, wherein: The electrohydraulic spool valve is movable within a continuous range to meter hydraulic communication between the first port, the second port, and the third port, Wherein, the first port is communicated with the output port of the pressure reducing valve, the second port is the output port of the monomer valve, and the third port is communicated with the tank port.

5. The single body valve according to claim 4, wherein: The first position of the electrohydraulic spool valve is an open position in which the first port opens to an output port of the body.

6. The single body valve according to claim 1, wherein: The electrohydraulic spool valve allows outlet pressure from the pressure reducing valve to be present at the output port of the body when no current is applied to the proportional solenoid, and When the current applied to the proportional solenoid is greater than a threshold current, the pressure at the output port decreases in proportion and inversely to the current applied to the proportional solenoid.

7. The single body valve according to claim 6, wherein: The threshold current is 0.4A to 0.6A.

8. The single body valve according to claim 1, wherein: The rate of pressure reduction at the output port when the current applied to the proportional solenoid is above a threshold current is determined at least in part by a diameter of the pressure feedback pin.

9. An electrohydraulic brake valve, comprising: a body having a brake port, a pressure supply port, and a tank port; a spool slidably retained in the body to meter hydraulic communication between the first port, the second port, and the third port; a return spring providing a spring force on the valve core in a first direction; a pressure feedback pin arranged to provide a restoring force on the valve core that is opposite to the spring force; a proportional solenoid constructed and arranged to provide a modulating force opposing the spring force when fully energized; as well as a pressure reducing valve located between the pressure supply port and the first port; The valve core is capable of moving along a continuous range of positions between a first position where the first port opens to the third port, a modulation position, and a third position where the second port opens to the third port in response to a balance among the spring force, the restoring force and the modulation force.

10. The electrohydraulic brake valve according to claim 9, wherein: The pressure reducing valve is externally adjustable.

11. The electrohydraulic brake valve according to claim 10, which is configured as a reverse-modulating electrohydraulic brake valve, wherein: The proportional solenoid is configured to increase the modulation force in proportion to increasing the current above a predetermined current threshold.

12. The electrohydraulic brake valve according to claim 11, wherein: The current threshold is at least 0.4A.

13. The electro-hydraulic brake valve according to claim 12, wherein: When no current is applied to the proportional solenoid, the modulating force is zero.

14. The electro-hydraulic brake valve according to claim 13, wherein: The proportional solenoid is electronically controlled.

15. A brake system comprising a reverse-modulated electro-hydraulic brake valve according to claim 11.

16. The brake system of claim 15, configured as a spring applied hydraulically released brake system.

17. The brake system of claim 15, configured as a hydraulically applied spring released brake system.

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