Hydraulic steering brake system, electro-hydraulic steering brake system and bulldozer

Abstract

The invention discloses a hydraulic steering brake system, an electro-hydraulic control steering brake system and a bulldozer. The hydraulic steering brake system comprises an oil tank, an oil pump, a parking brake valve, a service brake valve, a steering brake valve, a steering clutch and a brake clutch. The oil pump supplies oil to each control valve, and a port A1 and a port A2 of the service brake valve can respectively control a pilot port of the steering brake valve; the parking brake valve controls a main oil source of the steering brake valve, an oil way of the steering brake valve is cut off during parking, and the brake clutch is normally closed to realize reliable locking; in the running process, the steering clutch is controlled to be combined and the brake clutch is pressed tightly in a linkage mode by adjusting the conduction area of the port P and the port A1 of the service brake valve and the conduction area of the port P and the port A2, and flexible steering and composite braking are achieved. Particularly, under the high-torque working condition, the problem that traditional spring braking is insufficient is effectively solved, operation safety and flexibility are remarkably improved, fuel economy is remarkably improved, and the service life of the whole machine is remarkably prolonged.

Description

Technical Field

[0001] This application relates to the field of engineering machinery technology, and in particular to a hydraulic steering and braking system, an electro-hydraulic steering and braking system, and a bulldozer. Background Technology

[0002] Hydraulic bulldozers are widely used in earthmoving, mining, and infrastructure construction due to their reliable structure, ease of operation, and strong adaptability. Among them, hydraulic steering systems are widely used in small and medium horsepower hydraulic bulldozers because of their simple structure, low manufacturing cost, and relatively relaxed requirements on hydraulic oil cleanliness.

[0003] Currently, hydraulic bulldozers with normally closed braking systems generally employ a service braking method: without cutting off power output from the engine to the transmission system, the operator depresses the foot brake pedal, releasing the control oil pressure of the brake clutch through the hydraulic control circuit. At this time, the return spring inside the brake clutch pushes the friction plates and steel plates together, thereby generating braking torque and achieving deceleration or stopping of the entire machine. This braking mechanism can effectively achieve braking function and meet basic operational requirements under low output torque conditions such as low engine speed or high gear transmission.

[0004] However, under high-torque conditions with high engine speeds and the transmission in low gears (such as 1st or 2nd gear), the above braking method has significant drawbacks: due to the continuous output of large torque from the power system, relying solely on spring force to press the brake clutch is insufficient to overcome the driving torque transmitted by the transmission system, resulting in insufficient braking force and inability to effectively decelerate or stop. This not only poses serious safety hazards but also forces the brake clutch to operate in a slipping state for extended periods, leading to a series of negative effects, including but not limited to: accelerated abnormal wear of the brake band, increased transmission system oil temperature, accelerated oxidation and deterioration of hydraulic oil, and increased oil contamination. Furthermore, the slipping power consumption generated during ineffective braking also causes unnecessary energy waste, reducing the overall fuel economy of the engine. Summary of the Invention

[0005] The purpose of this application is to provide a hydraulic steering and braking system, an electro-hydraulic steering and braking system, and a bulldozer, which not only improves the operational flexibility, safety, and economy of the bulldozer, but also effectively solves the shortcomings of the traditional hydraulic bulldozer braking method under high output torque conditions, and significantly improves the overall working efficiency and service life of the machine.

[0006] The embodiments of this application can be implemented as follows: In a first aspect, the present invention provides a hydraulic steering and braking system, including an oil tank, an oil pump, a parking brake valve, a service brake valve, a steering brake valve, a steering clutch, and a braking clutch; The inlet of the oil pump is connected to the oil tank, and the P port of the parking brake valve and the P port of the service brake valve are both connected to the outlet of the oil pump. Both port A1 and port A2 of the service brake valve are connected to the pilot port of the steering brake valve. The parking brake valve's port A is connected to the steering brake valve's port P, the steering brake valve's port A1 is connected to the steering clutch's inlet, and the steering brake valve's port A2 is connected to the steering clutch's inlet. The T-port of the service brake valve, the T-port of the steering brake valve, the outlet of the steering clutch, and the outlet of the brake clutch are all connected to the oil tank. In the case that the P port and A port of the parking brake valve are blocked, the P port of the steering brake valve is blocked from the A1 port and connected to the A2 port. When the parking brake valve's P port and A port are connected, the conduction area between the service brake valve's P port and A1 port and A2 port respectively is positively correlated with the conduction area between the steering brake valve's P port and A1 port, and negatively correlated with the conduction area between the steering brake valve's P port and A2 port.

[0007] In an optional embodiment, the service brake valve includes a left two-position three-way solenoid valve and a right two-position three-way solenoid valve; The P port of both the left two-position three-way solenoid valve and the right two-position three-way solenoid valve are connected to the oil pump. The T-port of the left two-position three-way solenoid valve and the T-port of the right two-position three-way solenoid valve are both connected to the oil tank. The A port of the left two-position three-way solenoid valve and the A port of the right two-position three-way solenoid valve are both connected to the pilot port of the steering brake valve.

[0008] In an optional embodiment, the parking brake valve includes a two-position three-way hydraulic control valve and an electro-hydraulic control valve; The P port and pilot port of the two-position three-way hydraulic control valve and the P port of the electro-hydraulic control valve are all connected to the outlet of the oil pump. The A port of the two-position three-way hydraulic control valve is connected to the P port of the steering brake valve. The T port of the two-position three-way hydraulic control valve and the T port of the electro-hydraulic control valve are both connected to the oil tank. When the electro-hydraulic control valve is open, the P port and A port of the two-position three-way hydraulic control valve are blocked; when the electro-hydraulic control valve is closed, the P port and A port of the two-position three-way hydraulic control valve are connected.

[0009] In an optional embodiment, the parking brake valve further includes a parking relief valve, the P port of which is connected to the outlet of the oil pump. The P port of the two-position three-way hydraulic control valve, the P port of the electro-hydraulic control valve, and the pilot port of the two-position three-way hydraulic control valve are all connected to the T port of the parking relief valve.

[0010] In an optional embodiment, the steering brake valve includes a steering valve and a brake valve, wherein the pilot port of the steering valve and the pilot port of the brake valve are both connected to the A1 port and A2 port of the service brake valve. The P port of the steering valve and the P port of the brake valve are both connected to the A port of the parking brake valve. The T-port of the steering valve and the T-port of the brake valve are both connected to the oil tank. The A port of the steering valve is connected to the inlet of the steering clutch, and the A port of the brake valve is connected to the inlet of the brake clutch. The conduction area between the P port and A port of the steering valve is positively correlated with the oil inlet pressure of the steering valve pilot port; the conduction area between the P port and A port of the brake valve is negatively correlated with the oil inlet pressure of the brake valve pilot port.

[0011] In an optional embodiment, the steering valve includes a left steering valve and a right steering valve, the brake valve includes a left brake valve and a right brake valve, the steering clutch includes a left steering clutch and a right steering clutch, and the brake clutch includes a left brake clutch and a right brake clutch. The A port of the left steering valve is connected to the left steering clutch, the A port of the right steering valve is connected to the right steering clutch, the A port of the left brake valve is connected to the left brake clutch, and the A port of the right brake valve is connected to the right brake clutch.

[0012] In an optional embodiment, the hydraulic steering and braking system further includes a coarse filter, a fine filter, an overflow valve, and an accumulator; The coarse filter, the oil pump, the fine filter, and the accumulator are connected in series, and the P port of the service brake valve is connected to the accumulator. The P port of the overflow valve is connected to the outlet of the oil pump, and the T port of the overflow valve is connected to the oil tank.

[0013] In a second aspect, the present invention provides an electro-hydraulic steering and braking system, including a controller, a parking brake controller, a service brake pedal, a steering brake controller, and a hydraulic steering and braking system as described in any of the foregoing embodiments; The parking brake controller, the service brake pedal, and the steering brake controller are all electrically connected to the controller. Both the parking brake valve and the service brake valve are electrically connected to the controller. The steering brake control unit is electrically connected to the service brake valve. When the parking brake controller is in the locked state, the controller controls the P port and A port of the parking brake valve to be blocked; when the parking brake controller is in the unlocked state, the controller controls the P port and A port of the parking brake valve to be open. When the parking brake controller is in the unlocked state, the steering brake controller can control the conduction area between the P port and A1 port or between the P port and A2 port of the service brake valve through the controller. The service brake pedal can synchronously control the conduction area between the P port of the service brake valve and the A1 port and A2 port respectively through the controller.

[0014] In an optional embodiment, the steering brake controller includes a handle with a left-turn button and a right-turn button. The left-turn button controls the connection between the P port and the A1 port of the service brake valve, and the right-turn button controls the connection between the P port and the A2 port of the service brake valve.

[0015] Thirdly, the present invention provides a bulldozer including the electro-hydraulic steering and braking system described in the foregoing embodiments.

[0016] Compared with the prior art, the beneficial effects of the embodiments of this application include, for example: 1. Parking Lock Function: When the P and A ports of the parking brake valve are blocked, this system ensures that both the steering clutch and the brake clutch remain normally closed, allowing the brake clutch to generate maximum braking force while the steering clutch does not transmit power, thus locking the bulldozer in place. This design guarantees the safety and stability of construction machinery or vehicles when parked.

[0017] 2. Starting and driving control: When the P port and A port of the parking brake valve are connected, the hydraulic oil flows to the steering brake valve. If there is no electrical signal input to the service brake valve, the P port of the steering brake valve is blocked from the A1 port and connected to the A2 port. The brake clutch is supplied with hydraulic oil at maximum pressure to release the brake. The steering clutch is not supplied with oil to maintain maximum engagement force, and the power is transmitted completely, allowing the bulldozer to engage gear and start driving quickly.

[0018] 3. Flexible service brake adjustment: By pressing the service brake pedal, the oil flow of the service brake valve can be controlled. The braking force and power transmission of the traveling mechanism (tracks or wheels) can be flexibly adjusted as needed, thereby achieving precise deceleration or stopping, improving safety and avoiding the brake clutch from working in a slipping state for a long time.

[0019] 4. Efficient Steering Operation: When turning is required while driving, the driver can operate the steering brake control unit to select whether the P port of the service brake valve is connected to the A1 port or the A2 port, thereby adjusting the power difference between the left and right sides of the travel mechanism and achieving turning operations of different radii. In particular, by maximizing the control of the oil flow between the P port and A1 or between the P port and A2 port of the service brake valve, the steering clutch on one side can be fully disengaged and the braking force of the brake clutch can be maximized, thus achieving the smallest turning radius.

[0020] 5. By electrically connecting the steering brake controller and the service brake pedal to the service brake valve, and then connecting the service brake valve to the pilot port of the steering brake valve, a highly efficient hydraulic control architecture with electro-hydraulic logic for functional coordination is constructed. The driver's operating intention (steering command and braking command) is first converted into an electrical signal, which is then processed by the controller to drive the service brake valve to output the corresponding pilot control pressure or flow. This pilot signal further regulates the steering brake valve, thereby dynamically adjusting the flow area distribution between P→A1 (steering clutch side) and P→A2 (brake clutch side). This avoids the power bottleneck of all-electric drive in heavy engineering machinery and overcomes the lack of intelligent coordination capability of pure hydraulic control.

[0021] In summary, this hydraulic steering and braking system not only improves the operational flexibility, safety, and economy of bulldozers, but also effectively solves the shortcomings of traditional hydraulic bulldozer braking methods under high output torque conditions, significantly improving the overall working efficiency and service life of the machine. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the electro-hydraulic steering and braking system according to an embodiment of this application.

[0024] Icons: 1-Fuel tank; 2-Coarse filter; 3-Fuel pump; 4-Fine filter; 5-Relief valve; 6-Accumulator; 7-Steering brake controller; 8-Controller; 9-Service brake valve; 9L-Left 2-position 3-way solenoid valve; 9R-Right 2-position 3-way solenoid valve; 10-Steering brake valve; 10A-Left steering valve; 10B-Left brake valve; 10C-Right brake valve; 10D-Right steering valve; 11-Left steering clutch; 12-Left brake clutch; 13-Right brake clutch; 14-Right steering clutch; 15-Parking brake valve; 15A-Parking relief valve; 15B-Electro-hydraulic control valve; 15C-2-position 3-way hydraulic control valve; 16-Parking brake controller; 17-Service brake pedal. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0028] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0029] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0030] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0031] The following is in conjunction with the appendix Figure 1 This application provides a detailed description of some embodiments. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0032] This application discloses an electro-hydraulic steering and braking system, including a controller 8, a parking brake controller 16, a service brake pedal 17, a steering brake controller 7, and a hydraulic steering and braking system.

[0033] The parking brake controller 16, the service brake pedal 17 and the steering brake controller 7 are all electrically connected to the controller 8. Both the parking brake valve 15 and the service brake valve 9 are electrically connected to the controller 8. The steering brake control valve 7 can be a control handle or button (mechanical button or virtual button) in the cab of a bulldozer, tractor or other construction machinery vehicle, mainly used to control the steering of the equipment.

[0034] For example, the steering brake control device 7 includes a handle with a left-turn button and a right-turn button. The left-turn button can control the P port of the service brake valve 9 to be connected to the A1 port, and the right-turn button can control the P port of the service brake valve 9 to be connected to the A2 port, thereby realizing the steering operation of the entire construction machinery or vehicle.

[0035] The service brake pedal 17 is used to realize the service braking of construction machinery or vehicles. The service brake is the main braking system used to decelerate or stop construction machinery or vehicles during operation.

[0036] The parking brake controller 16 can be a parking brake lever or a button (mechanical button or virtual button) used to realize the parking brake of the vehicle. The parking brake is a braking system used to prevent the vehicle from rolling when it is parked for a long time. It is usually a mechanical locking type and is independent of the service brake (foot brake). It is an important safety guarantee.

[0037] The hydraulic steering and braking system includes an oil tank 1, an oil pump 3, a parking brake valve 15, a service brake valve 9, a steering brake valve 10, a steering clutch, and a braking clutch; The inlet of the oil pump 3 is connected to the oil tank 1, and the P port of the parking brake valve 15 and the P port of the service brake valve 9 are both connected to the outlet of the oil pump 3. Both port A1 and port A2 of the service brake valve 9 are connected to the pilot port of the steering brake valve 10. The parking brake valve 15 has port A connected to port P of the steering brake valve 10, the steering brake valve 10 has port A1 connected to the inlet of the steering clutch, and the steering brake valve 10 has port A2 connected to the inlet of the brake clutch. The T-port of the service brake valve 9, the T-port of the steering brake valve 10, the outlet of the steering clutch, and the outlet of the brake clutch are all connected to the oil tank 1. Wherein, when the P port and A port of the parking brake valve 15 are blocked, the P port of the steering brake valve 10 is blocked from the A1 port and connected to the A2 port. When the P port and A port of the parking brake valve 15 are open, the conduction area between the service brake valve 9 port and the A1 port and the A2 port respectively is positively correlated with the conduction area between the steering brake valve 10 port and the A1 port, and negatively correlated with the conduction area between the steering brake valve 10 port and the A2 port.

[0038] When the parking brake controller 16 is in the locked state, the controller 8 controls the P port and A port of the parking brake valve 15 to be blocked. When the parking brake controller 16 is in the unlocked state, the controller 8 controls the P port and A port of the parking brake valve 15 to be open. When the parking brake controller 16 is in the unlocked state, the steering brake controller 7 can control the conduction area between the P port and A1 port or between the P port and A2 port of the service brake valve 9 through the controller 8, and the service brake pedal 17 can synchronously control the conduction area between the service brake valve 9 port and the A1 port and A2 port respectively through the controller 8.

[0039] In this way, when the P port and A port of the parking brake valve 15 are blocked, hydraulic oil will not flow to the steering brake valve 10. At this time, both the steering clutch and the brake clutch are not supplied with oil and remain normally closed. The brake clutch brakes to the maximum extent so that the bulldozer remains parked and locked.

[0040] After the P port and A port of the parking brake valve 15 are connected, the hydraulic oil will flow to the steering brake valve 10. When there is no control electrical signal input to the service brake valve 9, the P port of the service brake valve 9 is blocked from both the A1 port and the A2 port. Correspondingly, the P port of the steering brake valve 10 is blocked from the A1 port and connected to the A2 port. At this time, the brake clutch is supplied with hydraulic oil at maximum pressure, the steering clutch remains engaged, and the power transmission from the engine to the traveling mechanism is maintained. When the brake clutch is released, the bulldozer can be put into gear and start driving. During the operation of construction machinery or vehicles, if the vehicle needs to slow down or stop by braking, the driver can control the oil flow of the service brake valve 9 by pressing the service brake pedal 17. This simultaneously controls the conduction area between the P port of the service brake valve 9 and the A1 and A2 ports respectively. The greater the depth of pressing the service brake pedal 17, the greater the conduction area between the P port and the A port of the service brake valve 9, and the greater the oil pressure supplied to the pilot port of the steering brake valve 10. This increases the conduction area between the A1 port and the P port and the A2 port of the steering brake valve 10, resulting in a smaller oil flow to the brake clutch and a greater braking force on the traveling mechanism (tracks or wheels), thus achieving deceleration or stopping. Furthermore, when the service brake pedal 17 is pressed, the increased oil flow to the steering clutch reduces the corresponding engagement force, thereby actively weakening the driving force transmitted from the engine to the traveling mechanism. Compared to the traditional method that relies solely on springs to press the friction pair, this application realizes a composite braking mechanism of "power cut-off + mechanical braking", which significantly enhances the overall machine torque, ensures reliable deceleration or stopping under high output torque conditions, reduces safety hazards, and avoids the brake clutch working in a slipping state for a long time.

[0041] If turning is required during driving, the driver can operate the steering brake control 7 to connect the P port of the service brake valve 9 to the A1 port (left turn) or the A2 port (right turn). This reduces the braking force of the steering clutch and increases the braking force of the brake clutch, creating a difference in power between the left and right sides of the travel mechanism, thus achieving a large-radius turn. As the driver continues to control the conduction area between the P port and A1 port of the service brake valve 9 (or between the P port and A2 port) through the steering brake control 7 to the maximum oil flow, the steering clutch for left or right turn is released, and the braking force of the brake clutch is at its maximum, thus achieving a small-radius turn. Upon completion of the turn, releasing the steering brake control 7 engages the steering clutch to output power, and the brake clutch disengages, resuming straight-line driving.

[0042] Furthermore, since the service brake valve 9 is connected to the pilot port of the steering brake valve 10, forming a pilot-controlled hydraulic system, the pilot control uses a small flow rate and low pressure control oil to drive the main valve core. The driver only needs to apply a small operating force (such as lightly pressing the pedal or lightly pulling the lever) to achieve precise control of the high-pressure main oil circuit. This significantly reduces operator fatigue and improves driving comfort. At the same time, the steering and service brakes share a single main control valve (i.e., the service brake valve 9), and the steering brake valve 10 is controlled by two independent pilot signals (from the bicycle brake pedal 17 and the steering brake controller 7). This design avoids setting separate main valves for steering and braking, reduces the number of hydraulic components, simplifies the pipeline layout, and improves system reliability. Meanwhile, the oil circuit to the steering brake valve 10 is only opened by the pilot signal when needed, avoiding energy loss caused by continuous high-pressure overflow. The energy-saving effect is particularly significant under conditions of frequent start-stop or fine-tuning of steering.

[0043] Based on the above, the hydraulic steering and braking system of this embodiment has the following main effects: 1. Parking Lock Function: When the P and A ports of the parking brake valve 15 are blocked, this system ensures that both the steering clutch and the brake clutch remain normally closed, allowing the brake clutch to generate maximum braking force while the steering clutch does not transmit power, thus locking the bulldozer in place. This design guarantees the safety and stability of construction machinery or vehicles when parked.

[0044] 2. Starting and driving control: When the P port and A port of the parking brake valve 15 are connected, the hydraulic oil flows to the steering brake valve 10. At this time, if there is no electrical signal input to the service brake valve 9, the P port of the steering brake valve 10 is blocked from the A1 port and connected to the A2 port. The brake clutch is supplied with hydraulic oil at the maximum pressure to release the brake. The steering clutch is not supplied with oil to maintain the maximum engagement force, and the power is transmitted completely, so that the bulldozer can be engaged and started driving quickly.

[0045] 3. Flexible service brake adjustment: By pressing the service brake pedal 17, the oil flow of the service brake valve 9 can be controlled. The braking force and power transmission of the traveling mechanism (track or wheel) can be flexibly adjusted as needed, thereby achieving precise deceleration or stopping, improving safety and avoiding the brake clutch from working in a slipping state for a long time.

[0046] 4. Efficient Steering Operation: When turning is required during driving, the driver can operate the steering brake control unit 7 to select whether the P port of the service brake valve 9 is connected to the A1 port or the A2 port, thereby adjusting the power difference between the left and right sides of the travel mechanism to achieve turning operations of different radii. In particular, by maximizing the control of the oil flow between the P port and A1 or between the P port and A2 port of the service brake valve 9, the steering clutch on one side can be fully disengaged and the braking force of the brake clutch can be maximized, thus achieving the smallest turning radius.

[0047] 5. The steering brake controller 7 and the service brake pedal 17 are electrically connected to the service brake valve 9, and the service brake valve 9 is then connected to the pilot port of the steering brake valve 10. This constructs a high-efficiency hydraulic control architecture that achieves functional coordination through electro-hydraulic logic. The driver's operating intention (steering command and braking command) is first converted into an electrical signal. After being processed by the controller 8, the service brake valve 9 is driven to output the corresponding pilot control pressure or flow. This pilot signal further regulates the steering brake valve 10, thereby dynamically adjusting the flow area distribution between P→A1 (steering clutch side) and P→A2 (brake clutch side). This avoids the power bottleneck of all-electric drive in heavy engineering machinery and overcomes the deficiency of pure hydraulic control in lacking intelligent coordination capabilities.

[0048] In summary, this hydraulic steering and braking system not only improves the operational flexibility, safety, and economy of bulldozers, but also effectively solves the shortcomings of traditional hydraulic bulldozer braking methods under high output torque conditions, significantly improving the overall working efficiency and service life of the machine.

[0049] In detail, the steering brake valve 10 includes a steering valve and a brake valve, and the pilot port of the steering valve and the pilot port of the brake valve are both connected to port A of the service brake valve 9. The P port of the steering valve and the P port of the brake valve are both connected to the A port of the parking brake valve 15. The T-port of the steering valve and the T-port of the brake valve are both connected to the oil tank 1; The A port of the steering valve (i.e., the A1 port of the entire steering brake valve 10) is connected to the inlet of the steering clutch, and the A port of the brake valve (i.e., the A2 port of the entire steering brake valve 10) is connected to the inlet of the brake clutch. The conduction area between the P port and A port of the steering valve is positively correlated with the oil inlet pressure of the steering valve pilot port; the conduction area between the P port and A port of the brake valve is negatively correlated with the oil inlet pressure of the steering valve pilot port.

[0050] Thus, since both the pilot port of the steering valve and the pilot port of the brake valve are connected to the same pilot oil circuit (i.e., port A of the service brake valve 9) for common oil supply, this means that when the driver operates the steering brake control unit 7 or depresses the brake pedal (controlling the service brake valve 9), the oil inlet pressure of the pilot port will change. That is, the pilot pressure is a unified control variable for steering and braking actions. By using a single pilot pressure signal to simultaneously regulate steering release and braking application, the operating logic is simplified.

[0051] As the conduction area between the P port and A port of the steering valve increases with the increase of pilot pressure, the oil pressure of the steering clutch increases accordingly, and the braking force decreases (clutch releases), thus achieving steering. On the other hand, the conduction area between the P port and A port of the brake valve decreases with the increase of pilot pressure, so the oil pressure of the brake clutch decreases and the spring presses the friction plate, thereby increasing the braking force. This reverse design of one increasing and the other decreasing constitutes the hydraulic interlock mechanism of braking and steering, which ensures a smooth transition between braking and steering actions, avoids abrupt switching, and improves handling comfort and safety.

[0052] It is understandable that for tracked construction machinery or vehicles, steering is usually achieved by controlling the different speeds of the left and right walking mechanisms (tracks). For example, braking and decelerating the left track achieves a left turn, and braking and decelerating the right track achieves a right turn. Therefore, in this embodiment, for tracked construction machinery or vehicles, the steering valve includes a left steering valve 10A and a right steering valve 10D, the braking valve includes a left braking valve 10B and a right braking valve 10C, the steering clutch includes a left steering clutch 11 and a right steering clutch 14, and the braking clutch includes a left braking clutch 12 and a right braking clutch 13. The A port of the left steering valve 10A is connected to the left steering clutch 11, the A port of the right steering valve 10D is connected to the right steering clutch 14, the A port of the left brake valve 10B is connected to the left brake clutch 12, and the A port of the right brake valve 10C is connected to the right brake clutch 13.

[0053] In this way, since the left and right steering clutches 14 and the left and right braking clutches 13 are controlled by their respective independent hydraulic valves, the system can apply different driving / braking states to the two sides of the traveling mechanism. When one side of the steering clutch is released (oil is supplied) while the other side remains engaged (or the braking clutch is pressed), a speed difference is generated between the two tracks, thereby achieving smooth and controllable differential steering and avoiding slippage or steering lag of the whole machine.

[0054] When a turn is required, the driver can use the steering brake controller 7 to individually operate the conduction area of ​​the service brake valve 9 at port P→A1 or P→A2 to precisely adjust the pilot pressure on the corresponding side, thereby continuously controlling the opening of the steering valve and brake valve on that side. This enables a full range of adjustment from large-radius gradual turns (wide turns) to small-radius sharp turns (narrow turns), significantly enhancing the equipment's maneuverability and operational accuracy in narrow spaces, trench edges, or complex terrain.

[0055] The left and right brake clutches 13 are independently controlled by the left and right brake valves 10C, respectively. During the braking process, the braking force on both sides can be applied synchronously, avoiding deviation, fishtailing or skidding caused by lag or insufficiency of braking force on one side. Especially on slopes or wet and slippery surfaces, it effectively improves the braking stability and driving safety of the whole vehicle.

[0056] The service brake valve 9 includes a left two-position three-way solenoid valve 9L and a right two-position three-way solenoid valve 9R; The P port of the left two-position three-way solenoid valve 9L and the P port of the right two-position three-way solenoid valve 9R are both connected to the oil pump 3. The T port of the left two-position three-way solenoid valve 9L and the T port of the right two-position three-way solenoid valve 9R are both connected to the oil tank 1. The A port of the left two-position three-way solenoid valve 9L (i.e., the A1 port of the entire service brake valve 9) and the A port of the right two-position three-way solenoid valve 9R (i.e., the A2 port of the entire service brake valve 9) are both connected to the pilot port of the steering brake valve 10.

[0057] In this way, since the guide area between the P and A ports of the two-position three-way solenoid valve is positively correlated with the input proportional current signal, the electrical signal generated when the driver depresses the driving brake pedal 17 (e.g., via the pedal position sensor) can linearly and synchronously adjust the opening of the left two-position three-way solenoid valve 9L and the right two-position three-way solenoid valve 9R, thereby continuously and precisely controlling the control oil pressure output to the steering valve pilot port and the brake valve pilot port. This allows the braking force to be steplessly adjusted according to the operating intention, avoiding the shock or response lag caused by traditional on / off braking.

[0058] The pilot pressure generated by the service brake enters the steering brake valve 10 via a one-way valve, which on the one hand reduces the oil supply to the brake clutch (increasing braking force), and on the other hand increases the oil supply to the steering clutch (reducing the power transmission efficiency on the steering side). This mechanism, driven by the same pilot pressure to link braking and power transmission in opposite directions, can improve handling safety under complex operating conditions.

[0059] Furthermore, since each two-position three-way solenoid valve conducts the P→A passage when energized and switches to the A→T pressure relief passage when de-energized, when the driver only operates the left brake, the left two-position three-way solenoid valve 9L is energized and outputs pilot pressure, while the right two-position three-way solenoid valve 9R is de-energized and maintains pressure relief, so that the steering brake valve 10 only builds pressure in the left pilot chamber, thereby releasing the left brake clutch separately and realizing single-sided braking and steering, and vice versa for right turn.

[0060] When both sides are braked simultaneously (i.e., when the driving brake pedal 17 is pressed), the left and right solenoid valves are energized at the same time, supplying pressure to the pilot ports of the steering brake valve 10 on both sides simultaneously, and releasing the left and right brake clutches 13 simultaneously to achieve braking of the whole machine; when there is no braking command, both valves are in the A→T connected state to ensure that the pilot chamber pressure is released quickly, and the brake clutch is reliably pressed under the action of the return spring to ensure parking safety.

[0061] In summary, the dual solenoid valve structure naturally supports differential braking logic, enabling flexible switching between single-sided or double-sided braking without the need for a mechanical linkage mechanism, thus improving steering agility and operational efficiency. Moreover, the solenoid valve operates rapidly (millisecond level), and its design of releasing pressure upon power failure ensures that the brake clutch automatically locks in the event of a power outage or malfunction. Compared to proportional valves or mechanical spool valves, the two-position three-way solenoid valve has a simple structure, strong anti-pollution capability, and long service life, making it suitable for the harsh working conditions of bulldozers. In this embodiment, the parking brake valve 15 includes a two-position three-way hydraulic control valve 15C and an electro-hydraulic control valve 15B; The P port and pilot port of the two-position three-way hydraulic control valve 15C and the P port of the electro-hydraulic control valve 15B are all connected to the outlet of the oil pump 3. The A port of the two-position three-way hydraulic control valve 15C is connected to the P port of the steering brake valve 10. The T port of the two-position three-way hydraulic control valve 15C and the T port of the electro-hydraulic control valve 15B are both connected to the oil tank 1. When the electro-hydraulic control valve 15B is open, the P port and A port of the two-position three-way hydraulic control valve 15C are blocked; when the electro-hydraulic control valve 15B is closed, the P port and A port of the two-position three-way hydraulic control valve 15C are connected.

[0062] Thus, when the machine needs to be parked, the driver operates the parking brake controller 16, which in turn energizes the electro-hydraulic control valve 15B to open. This releases the pressure in the pilot chamber of the two-position three-way hydraulic control valve 15C to the oil tank 1, causing its valve core to switch to the P-T connected and P-A blocked position under the action of the spring. At this time, the hydraulic supply to the main oil circuit (P port) of the steering brake valve 10 is completely cut off, and both the left / right steering clutch 14 and the brake clutch are pressed by the return spring due to the loss of pressure, entering the fully locked braking state. This design not only relies on spring force but also ensures parking reliability through active oil cut-off, avoiding accidental movement caused by system leakage or residual pressure.

[0063] When normal driving or operation is required, the electro-hydraulic control valve 15B is de-energized and closed, and the pressure of the oil pump 3 acts simultaneously on the P port and pilot port of the two-position three-way hydraulic control valve 15C, so that its valve core is kept in the P-A conducting position, and continuously provides stable working oil pressure to the steering brake valve 10.

[0064] Optionally, the parking brake valve 15 also includes a parking relief valve 15A, the P port of which is connected to the outlet of the oil pump 3. The P port of the two-position three-way hydraulic control valve 15C, the P port of the electro-hydraulic control valve 15B, and the pilot port of the two-position three-way hydraulic control valve 15C are all connected to the T port of the parking relief valve 15A.

[0065] In this way, the parking relief valve 15A pre-regulates the high-pressure oil from the oil pump 3 and outputs it to its T port, which serves as the working oil port (P port) of the two-position three-way hydraulic control valve 15C, the pilot control port, and the oil inlet of the electro-hydraulic control valve 15B. This means that no matter how the main system pressure fluctuates (such as due to sudden load changes or pump flow variations), the pressure supplied to the parking brake logic circuit is always limited to below the set value of the parking relief valve 15A, thereby ensuring that the operating pressure of the two-position three-way hydraulic control valve 15C is stable and that the electro-hydraulic control valve 15B operates within a safe pressure range, thus ensuring that the pilot control response is linear and reliable.

[0066] In this embodiment, the hydraulic steering and braking system also includes a coarse filter 2, a fine filter 4, an overflow valve 5, and an accumulator 6; The coarse filter 2, oil pump 3, fine filter 4 and accumulator 6 are connected in series, and the P port of the service brake valve 9 is connected to the accumulator 6. The P port of the overflow valve 5 is connected to the outlet of the oil pump 3, and the T port of the overflow valve 5 is connected to the oil tank 1.

[0067] Thus, the hydraulic oil enters the oil pump 3 after being initially removed by the coarse filter 2 to remove large particulate contaminants, and then undergoes further filtration by the fine filter 4 to ensure that the oil entering the accumulator 6 and subsequent control valves (steering, parking, and service brake valves 9) has a high degree of cleanliness. Since these valves are mostly precision pilot components (such as electro-hydraulic valves and hydraulic control valves), they are extremely sensitive to contamination. The two-stage filtration significantly reduces the risk of jamming, wear, or malfunction, and improves the long-term reliability of the system.

[0068] The P port of the service brake valve 9 draws oil from the accumulator 6, rather than directly from the outlet of the oil pump 3. The accumulator 6 absorbs pressure fluctuations caused by output pulsations and sudden load changes of the oil pump 3, providing a more stable pilot pressure for the service brake valve 9 and improving the linearity and consistency of braking and steering operations. When the driver quickly operates the steering handle or urgently presses the brake pedal, the accumulator 6 can immediately release the stored high-pressure oil to compensate for the response lag of the oil pump 3 and ensure millisecond-level control response. In addition, even if the engine is briefly turned off or the pump stops working, the accumulator 6 can still support several critical operations (such as emergency parking), improving safety.

[0069] The relief valve 5 is directly connected to the outlet of the oil pump 3, forming the first-level overload protection of the system. When the accumulator 6 is full, the control valve is closed, or the pipeline is blocked, causing the system pressure to rise abnormally, the relief valve 5 will automatically open to release the excess flow back to the oil tank 1, preventing damage to the pump, pipeline or valve body due to overpressure, and ensuring that the system operates within the safe pressure range.

[0070] This embodiment also discloses a bulldozer that includes the electro-hydraulic steering and braking system described in the above embodiment.

[0071] The working principle of the electro-hydraulic steering and braking system in this embodiment is explained by way of example below: 1. Parking brake When the driver operates the parking brake control 16 (such as pressing the parking button or pulling the parking handle) to enter the locked state, the controller 8 outputs a signal to block the P port and A port of the parking brake valve 15, cutting off the hydraulic supply to the main oil circuit of the steering brake valve 10. At this time, both the steering clutch and the brake clutch lose pressure and remain normally closed under the action of the return spring—the steering clutch cuts off power transmission, and the brake clutch applies maximum braking force, achieving reliable parking and locking of the entire machine to prevent the vehicle from rolling.

[0072] 2. Steering control: With the parking brake released, the driver presses the left or right turn button on the steering brake control unit 7: During light operation, the left or right turn button has a small travel, and the corresponding side (left or right) service brake valve 9 outputs a small pilot pressure, which makes the steering clutch part on that side energized (partially engaged) and the brake clutch part depressurized (partially braked), resulting in a small speed difference between the two tracks, thus achieving a large-radius smooth turn. When operating with large movements, the left or right turn button reaches its maximum travel, the pilot pressure increases to the maximum, the corresponding side steering clutch is completely depressurized and disengaged (power cut off), and at the same time the braking clutch is fully engaged (power braking), the track on that side stops rotating, and the other side drives normally, thus achieving small-radius or even stationary turning.

[0073] 3. Service brakes: When the vehicle is in motion, the driver depresses the service brake pedal 17. The controller 8 adjusts the opening of the service brake valve 9 according to the pedal travel, and inputs control oil with corresponding pressure into the pilot port of the steering brake valve 10. Increased pilot pressure leads to reduced oil supply to the brake clutch and increased clamping, generating braking force. At the same time, the increased oil supply to the steering clutch makes engagement more reliable, maintaining power transmission stability and assisting in steering ease. The deeper you press the pedal, the greater the braking force, achieving linear and controllable deceleration or stopping.

[0074] In summary, the hydraulic steering and braking system, the electro-hydraulic steering and braking system, and the bulldozer used in this embodiment have at least the following advantages: 1. Significantly improved braking reliability: It adopts a composite braking mechanism of "power cut-off + active mechanical braking", which can still provide sufficient braking force under high output torque conditions such as high engine speed and low gear. It effectively solves the problems of brake failure and slippage caused by traditional methods that rely solely on spring compression, and greatly improves driving safety.

[0075] 2. Parking lock is safer and more reliable: When parked, the main oil circuit is cut off by electronic control, so that the steering and braking clutches are completely locked under the action of the spring, realizing dual mechanical braking to prevent slippage or accidental movement, which is in line with the safety principle of "braking upon loss of pressure" for construction machinery.

[0076] 3. Flexible and precise steering operation: It supports independent control on the left and right sides. By adjusting the travel of the steering controller, it can achieve stepless adjustment from large radius slow turn to small radius turn on the spot, meeting the high mobility operation requirements in narrow spaces and complex terrains.

[0077] 4. Easy to operate and user-friendly: Adopting a pilot-operated electro-hydraulic control structure, the driver only needs a small amount of operating force (lightly pull the handle or lightly press the pedal) to accurately control the high-pressure main oil circuit, which greatly reduces operator fatigue and improves operating comfort.

[0078] 5. High system integration and simplified structure: Steering and service braking share a single main control valve (service brake valve 9), which is controlled by superimposed pilot signals, reducing the number of hydraulic components and pipeline complexity, and improving system compactness and reliability.

[0079] 6. Strong ability to adapt to harsh working conditions: Compared to pure electronic proportional control systems, the combination of electronic control and pilot hydraulic control has lower requirements for hydraulic oil cleanliness, stronger anti-pollution capabilities, and is more suitable for field operation environments with high dust and vibration, such as mines and earthmoving, with lower maintenance costs.

[0080] 7. Energy-saving and efficient: The main oil circuit is opened only when needed by a pilot signal to avoid continuous high-pressure overflow; the accumulator 6 and the overflow valve 5 work together to optimize energy utilization, reduce system temperature rise and fuel consumption, and improve the overall economy of the machine.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A hydraulic steering and braking system, characterized in that, Includes fuel tank (1), fuel pump (3), parking brake valve (15), service brake valve (9), steering brake valve (10), steering clutch and brake clutch; The inlet of the oil pump (3) is connected to the oil tank (1), and the P port of the parking brake valve (15) and the P port of the service brake valve (9) are both connected to the outlet of the oil pump (3). The A1 port and A2 port of the service brake valve (9) are both connected to the pilot port of the steering brake valve (10); The A port of the parking brake valve (15) is connected to the P port of the steering brake valve (10), the A1 port of the steering brake valve (10) is connected to the inlet of the steering clutch, and the A2 port of the steering brake valve (10) is connected to the inlet of the brake clutch. The T-port of the service brake valve (9), the T-port of the steering brake valve (10), the outlet of the steering clutch, and the outlet of the brake clutch are all connected to the oil tank (1). In the case that the P port and A port of the parking brake valve (15) are blocked, the P port of the steering brake valve (10) is blocked from the A1 port and connected to the A2 port. When the P port and A port of the parking brake valve (15) are connected, the conduction area between the P port of the service brake valve (9) and the A1 port and the A2 port respectively is positively correlated with the conduction area between the P port and the A1 port of the steering brake valve (10) and negatively correlated with the conduction area between the P port and the A2 port of the steering brake valve (10).

2. The hydraulic steering and braking system according to claim 1, characterized in that, The service brake valve (9) includes a left two-position three-way solenoid valve (9L) and a right two-position three-way solenoid valve (9R). The P port of the left two-position three-way solenoid valve (9L) and the P port of the right two-position three-way solenoid valve (9R) are both connected to the oil pump (3). The T port of the left two-position three-way solenoid valve (9L) and the T port of the right two-position three-way solenoid valve (9R) are both connected to the oil tank (1). The A port of the left two-position three-way solenoid valve (9L) and the A port of the right two-position three-way solenoid valve (9R) are both connected to the pilot port of the steering brake valve (10).

3. The hydraulic steering and braking system according to claim 1, characterized in that, The parking brake valve (15) includes a two-position three-way hydraulic control valve (15C) and an electro-hydraulic control valve (15B). The P port and pilot port of the two-position three-way hydraulic control valve (15C) and the P port of the electro-hydraulic control valve (15B) are all connected to the outlet of the oil pump (3). The A port of the two-position three-way hydraulic control valve (15C) is connected to the P port of the steering brake valve (10). The T port of the two-position three-way hydraulic control valve (15C) and the T port of the electro-hydraulic control valve (15B) are both connected to the oil tank (1). When the electro-hydraulic control valve (15B) is open, the P port and A port of the two-position three-way hydraulic control valve (15C) are blocked; when the electro-hydraulic control valve (15B) is closed, the P port and A port of the two-position three-way hydraulic control valve (15C) are connected.

4. The hydraulic steering and braking system according to claim 3, characterized in that, The parking brake valve (15) also includes a parking relief valve (15A), the P port of which is connected to the outlet of the oil pump (3). The P port of the two-position three-way hydraulic control valve (15C), the P port of the electro-hydraulic control valve (15B), and the pilot port of the two-position three-way hydraulic control valve (15C) are all connected to the T port of the parking relief valve (15A).

5. The hydraulic steering and braking system according to claim 1, characterized in that, The steering brake valve (10) includes a steering valve and a brake valve. The pilot port of the steering valve and the pilot port of the brake valve are both connected to the A1 port and A2 port of the service brake valve (9). The P port of the steering valve and the P port of the brake valve are both connected to the A port of the parking brake valve (15). The T-port of the steering valve and the T-port of the brake valve are both connected to the oil tank (1); The A port of the steering valve is connected to the inlet of the steering clutch, and the A port of the brake valve is connected to the inlet of the brake clutch. The conduction area between the P port and A port of the steering valve is positively correlated with the oil inlet pressure of the steering valve pilot port; the conduction area between the P port and A port of the brake valve is negatively correlated with the oil inlet pressure of the brake valve pilot port.

6. The hydraulic steering and braking system according to claim 5, characterized in that, The steering valve includes a left steering valve (10A) and a right steering valve (10D), the brake valve includes a left brake valve (10B) and a right brake valve (10C), the steering clutch includes a left steering clutch (11) and a right steering clutch (14), and the brake clutch includes a left brake clutch (12) and a right brake clutch (13). The A port of the left steering valve (10A) is connected to the left steering clutch (11), the A port of the right steering valve (10D) is connected to the right steering clutch (14), the A port of the left brake valve (10B) is connected to the left brake clutch (12), and the A port of the right brake valve (10C) is connected to the right brake clutch (13).

7. The hydraulic steering and braking system according to claim 1, characterized in that, The hydraulic steering and braking system also includes a coarse filter (2), a fine filter (4), an overflow valve (5), and an accumulator (6). The coarse filter (2), the oil pump (3), the fine filter (4) and the accumulator (6) are connected in series, and the P port of the service brake valve (9) is connected to the accumulator (6). The P port of the overflow valve (5) is connected to the outlet of the oil pump (3), and the T port of the overflow valve (5) is connected to the oil tank (1).

8. An electro-hydraulic steering and braking system, characterized in that, Includes a controller (8), a parking brake control unit (16), a service brake pedal (17), a steering brake control unit (7), and the hydraulic steering brake system according to any one of claims 1-7; The parking brake controller (16), the service brake pedal (17) and the steering brake controller (7) are all electrically connected to the controller (8). The parking brake valve (15) and the service brake valve (9) are both electrically connected to the controller (8); The steering brake control unit (7) is electrically connected to the service brake valve (9); When the parking brake controller (16) is in the locked state, the controller (8) controls the P port and A port of the parking brake valve (15) to be blocked. When the parking brake controller (16) is in the unlocked state, the controller (8) controls the P port and A port of the parking brake valve (15) to be open. When the parking brake controller (16) is in the unlocked state, the steering brake controller (7) can control the conduction area between the P port and A1 port or between the P port and A2 port of the service brake valve (9) through the controller (8), and the service brake pedal (17) can synchronously control the conduction area between the P port of the service brake valve (9) and the A1 port and A2 port respectively through the controller (8).

9. The electro-hydraulic steering and braking system according to claim 8, characterized in that, The steering brake control device (7) includes a handle with a left turn button and a right turn button. The left turn button can control the P port of the service brake valve (9) to be connected to the A1 port, and the right turn button can control the P port of the service brake valve (9) to be connected to the A2 port.

10. A bulldozer, characterized in that, Includes the electro-hydraulic steering and braking system as described in claim 9.

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