Hydraulic travel system for marking vehicle and control method thereof

Abstract

A hydraulic travel system for a road marking vehicle and its control method include a closed hydraulic pump, a hydraulic motor, a first electromagnetic reversing valve, a hydraulic shuttle valve, a second electromagnetic reversing valve, and a low-pressure relief valve. The closed hydraulic pump's two oil outlets PA and PB are respectively connected to the hydraulic motor's two oil ports A and B. The first electromagnetic reversing valve's two oil ports P1 and P2 are respectively connected to the hydraulic motor's two oil ports A and B, forming a parallel circuit with the hydraulic motor. The hydraulic shuttle valve's two oil ports are respectively connected to the hydraulic motor's two oil ports A and B, and the hydraulic shuttle valve's control port C is connected to the second electromagnetic reversing valve. The oil outlet of the second electromagnetic reversing valve is connected to the oil inlet of the low-pressure relief valve. The present invention has a scientific principle and a compact structure. By improving existing conventional closed hydraulic travel systems, the safety, reliability, and work efficiency of road marking vehicles can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of engineering machinery, and in particular relates to a hydraulic travel system for a marking vehicle suitable for taking power from a transfer case and a control method thereof. Background Art

[0002] In the road marking (striping) industry, the nature of road marking vehicles requires them to maintain stable, low-speed operation during construction while also being able to switch to normal chassis operation during relocation, enabling them to adapt to long-distance relocations. Consequently, the integration of transfer cases and vehicle chassis is becoming increasingly common. During construction, the transfer case switches to hydraulic operation via a pneumatic cylinder. This allows the chassis' power to be transmitted to a hydraulic pump, which converts mechanical energy into hydraulic energy to drive a hydraulic motor. This hydraulic motor, in turn, drives the chassis' rear axle through the transfer case, enabling the vehicle to travel at low speeds. During relocation, the transfer case switches to mechanical travel mode, allowing the vehicle to operate as a normal chassis. This transmission arrangement maximizes the requirements of road marking vehicle construction and relocation. However, conventional closed-loop hydraulic travel systems can generate significant impact forces during emergency braking. This impact force can reverse the hydraulic pump, creating a pull on the engine, and can also cause a sudden increase in system pressure, posing a risk of pipe burst. At the same time, when a construction vehicle is on a longitudinal slope, gravity causes the reaction force from the chassis' rear axle to be transmitted to the hydraulic motor through the transfer case's internal gears. This prevents the transfer case's shift cylinder from pushing the shift fork to properly disengage and reengage the transfer case's output shaft from the hydraulic motor, posing a significant safety hazard. Therefore, resolving this issue can effectively reduce the risk of hydraulic system failure and improve the efficiency of the marking vehicle. Summary of the Invention

[0003] In order to address the deficiencies in the prior art, the present invention provides a hydraulic travel system for a marking vehicle and a control method thereof, which combines the advantages of a conventional closed travel hydraulic system and is improved based on actual working conditions. It is suitable for emergency braking of the marking vehicle during hydraulic travel and rapid switching of the transfer case's working mode under complex working conditions, effectively improving safety, reliability and work efficiency.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions: a hydraulic travel system for a marking vehicle, comprising a closed hydraulic pump, a hydraulic motor, a first solenoid reversing valve, a hydraulic shuttle valve, a second solenoid reversing valve and a low-pressure relief valve; the two oil outlets PA and PB of the closed hydraulic pump are respectively connected to the two oil ports A and B of the hydraulic motor; the two oil ports P1 and P2 of the first solenoid reversing valve are respectively connected to the two oil ports A and B of the hydraulic motor, and the first solenoid reversing valve and the hydraulic motor form a parallel circuit; the two oil ports of the hydraulic shuttle valve are respectively connected to the two oil ports A and B of the hydraulic motor, and the control port C of the hydraulic shuttle valve is connected to the second solenoid reversing valve; the oil outlet of the second solenoid reversing valve is connected to the oil inlet of the low-pressure relief valve.

[0005] It also includes a hydraulic oil radiator and a hydraulic oil tank. The closed hydraulic pump is driven by a transfer case to suck oil from the hydraulic oil tank. The oil unloading port of the closed hydraulic pump, the oil drain port of the hydraulic motor and the overflow port of the low-pressure overflow valve are all connected to the oil inlet of the hydraulic oil radiator; the oil outlet of the hydraulic oil radiator is connected to the oil inlet of the hydraulic oil tank.

[0006] The first solenoid reversing valve has a two-way check function. The electromagnet YV3 of the first solenoid reversing valve is associated with the brake signal of the marking vehicle chassis. When the chassis brake pedal is pressed, the electromagnet YV3 is also energized. When the brake pedal is released, the electromagnet YV3 loses power. The hydraulic motor and the transfer case output shaft of the marking vehicle are connected or separated by the switching cylinder. The electromagnet YV4 of the second solenoid reversing valve is associated with the switching cylinder control button. Regardless of whether the transfer case output shaft and the hydraulic motor are to be connected or separated, the electromagnet YV4 must be energized.

[0007] A method for controlling a hydraulic travel system for a marking vehicle includes the following three modes:

[0008] (1) When the hydraulic motor is coupled with the transfer case output shaft: first, pull up the handbrake of the marking vehicle chassis; then, couple the closed hydraulic pump with the transfer case, and the marking vehicle chassis drives the transfer case to drive the closed hydraulic pump to work; then, press the switch cylinder control button, and the switch cylinder action presses the meshing pair of gear end faces together, so that the transfer case output shaft is coupled with the hydraulic motor; at the same time, the electromagnet YV4 of the second electromagnetic reversing valve is energized, and the low-pressure relief valve works at this time; finally, the electromagnets YV1 and YV2 of the closed hydraulic pump are energized in sequence at intervals of 0.5 seconds (this time is adjustable), and the electrical signal should be as small as possible to drive the hydraulic motor forward and reverse at low speed and low torque. When the gears are engaged in place, the switch cylinder position switch sends a signal, indicating that the transfer case output shaft is coupled with the hydraulic motor in place, and the electromagnet YV4 of the second electromagnetic reversing valve and the electromagnets YV1 and YV2 of the closed hydraulic pump are all de-energized. At this point, the marking vehicle switches to the hydraulic travel mode;

[0009] (2) When the hydraulic motor is disengaged from the transfer case output shaft: pull up the car chassis handbrake, press the switch cylinder control button, the switch cylinder action will separate the meshing pair of gear end faces, the transfer case output shaft is disengaged from the hydraulic motor, and at the same time the electromagnet YV4 of the second electromagnetic reversing valve 5 is energized, and then the electromagnets YV1 and YV2 of the closed hydraulic pump are energized in sequence at intervals of 0.5 seconds (time is adjustable). The electrical signal should be as small as possible to drive the hydraulic motor to rotate forward and reverse at low speed and low torque. When the meshing gears are disengaged, the switch cylinder position switch sends a signal, indicating that the transfer case output shaft is disengaged from the hydraulic motor, and the electromagnet YV4 of the second electromagnetic reversing valve and the electromagnets YV1 and YV2 of the closed hydraulic pump are all de-energized. At this point, the marking vehicle switches to the mechanical travel mode;

[0010] (3) When the marking vehicle needs emergency braking during hydraulic travel, step on the brake pedal of the vehicle chassis, and the electromagnet YV3 of the first electromagnetic reversing valve will be energized to connect the two oil ports A and B of the hydraulic motor and lose power. The hydraulic motor is in a floating state and will not cause impact on the hydraulic system. The marking vehicle relies on the brake system of the chassis to achieve braking, which is more stable and reliable. On the other hand, during normal braking, the brake pedal can be reduced to achieve braking by reducing the displacement of the closed hydraulic pump. After the marking vehicle is stable, the current of the closed hydraulic pump electromagnet YV1 or YV2 is turned off.

[0011] By adopting the above technical solution, the present invention has the following technical effects:

[0012] In the present invention, a first electromagnetic reversing valve with a two-way check valve is connected in parallel to a conventional closed hydraulic travel system. The first reversing valve electromagnet is associated with the vehicle chassis brake signal. When the chassis brake pedal is pressed during emergency braking, the brake signal controls the reversing valve to be energized. At this time, the two oil ports of the hydraulic motor are connected and power is lost. The hydraulic motor is in a floating state, which does not cause any impact on the hydraulic system. The entire vehicle is braked by the chassis brake system, which is more stable and reliable. On the other hand, during normal braking, braking can be achieved by reducing the displacement of the closed hydraulic pump without pressing the brake pedal. When the transfer case is switched, the parking brake is applied and the switch cylinder control button is pressed. The cylinder pushes the shift fork, and the low-pressure relief valve is activated. The closed hydraulic pump is given as little current as possible to output a small flow rate, which drives the hydraulic motor to intermittently rotate forward and reverse. When the hydraulic motor is fully engaged with the gear of the transfer case output shaft, the switch cylinder position switch sends a signal, indicating that the hydraulic motor is engaged or disengaged from the output shaft. This system can quickly engage and disengage the hydraulic motor from the transfer case regardless of whether the vehicle is on flat ground or on a slope, greatly improving the efficiency and stability of the transfer case.

[0013] When the low-pressure relief valve is in effect, the pressure adjustment of the low-pressure relief valve can only make the hydraulic motor idle. According to experimental conditions, the set pressure of the low-pressure relief valve is about 5MPa. At this time, the pressure difference between the two oil ports A and B of the hydraulic motor is the set pressure of the low-pressure relief valve minus the oil replenishment pressure of the closed hydraulic pump, which avoids gear knocking when the hydraulic motor is engaged or disengaged from the transfer case output shaft.

[0014] In summary, the present invention has a scientific principle and a compact structure, and can improve the safety, reliability and working efficiency of the marking vehicle by improving the existing conventional closed hydraulic travel system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structural principle of the walking hydraulic system in the present invention. DETAILED DESCRIPTION

[0016] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0017] like Figure 1 As shown, a hydraulic travel system for a marking vehicle of the present invention includes a closed hydraulic pump 1, a hydraulic motor 2, a first electromagnetic reversing valve 3, a hydraulic shuttle valve 4, a second electromagnetic reversing valve 5 and a low-pressure relief valve 6; the two oil outlets PA and PB of the closed hydraulic pump 1 are respectively connected to the two oil ports A and B of the hydraulic motor 2; the two oil ports P1 and P2 of the first electromagnetic reversing valve 3 are respectively connected to the two oil ports A and B of the hydraulic motor 2, and the first electromagnetic reversing valve 3 and the hydraulic motor 2 form a parallel circuit; the two oil ports of the hydraulic shuttle valve 4 are respectively connected to the two oil ports A and B of the hydraulic motor 2, and the control port C of the hydraulic shuttle valve 4 is connected to the second electromagnetic reversing valve 5; the oil outlet of the second electromagnetic reversing valve 5 is connected to the oil inlet of the low-pressure relief valve 6.

[0018] The hydraulic travel system for the marking vehicle of the present invention also includes a hydraulic oil radiator 7 and a hydraulic oil tank 8. The closed hydraulic pump 1 is driven by a transfer case to suck oil from the hydraulic oil tank 8. The oil unloading port of the closed hydraulic pump 1, the oil drain port of the hydraulic motor 2 and the overflow port of the low-pressure overflow valve 6 are all connected to the oil inlet of the hydraulic oil radiator 7; the oil outlet of the hydraulic oil radiator 7 is connected to the oil inlet of the hydraulic oil tank 8.

[0019] The first solenoid reversing valve 3 has a two-way check function. The electromagnet YV3 of the first solenoid reversing valve 3 is associated with the brake signal of the chassis of the marking vehicle. When the chassis brake pedal is pressed, the electromagnet YV3 is also energized. When the brake pedal is released, the electromagnet YV3 loses power. The hydraulic motor 2 and the output shaft of the transfer case of the marking vehicle are connected or separated by the switching cylinder. The electromagnet YV4 of the second solenoid reversing valve 5 is associated with the switching cylinder control button. Regardless of whether the output shaft of the transfer case and the hydraulic motor 2 are to be connected or separated, the electromagnet YV4 must be energized.

[0020] A method for controlling a hydraulic travel system for a marking vehicle includes the following three modes:

[0021] (1) When the hydraulic motor 2 is coupled with the transfer case output shaft: first, pull up the handbrake of the marking vehicle chassis; then, couple the closed hydraulic pump 1 with the transfer case, and the marking vehicle chassis drives the transfer case to drive the closed hydraulic pump 1 to work; then, press the switch cylinder control button, and the switch cylinder action presses the meshing pair of gear end faces together, so that the transfer case output shaft is coupled with the hydraulic motor 2; at the same time, the electromagnet YV4 of the second electromagnetic reversing valve 5 is energized, and the low-pressure relief valve 6 works at this time; finally, the electromagnets YV1 and YV2 of the closed hydraulic pump 1 are energized in sequence at intervals of 0.5 seconds (this time is adjustable), and the electrical signal should be as small as possible, driving the hydraulic motor 2 to rotate forward and reverse at low speed and low torque. When the gears are engaged in place, the switch cylinder position switch sends a signal, indicating that the transfer case output shaft is coupled with the hydraulic motor 2 in place, and the electromagnet YV4 of the second electromagnetic reversing valve 5 and the electromagnets YV1 and YV2 of the closed hydraulic pump 1 are all de-energized. At this point, the marking vehicle switches to the hydraulic travel mode;

[0022] (2) When the hydraulic motor 2 is disengaged from the transfer case output shaft: pull up the car chassis handbrake, press the switch cylinder control button, the switch cylinder action will separate the meshing pair of gear end faces, the transfer case output shaft is disengaged from the hydraulic motor 2, and at the same time the electromagnet YV4 of the second electromagnetic reversing valve 55 is energized, and then the electromagnets YV1 and YV2 of the closed hydraulic pump 1 are energized in sequence at intervals of 0.5 seconds (time is adjustable). The electrical signal should be as small as possible to drive the hydraulic motor 2 forward and reverse at low speed and low torque. When the meshing gears are disengaged, the switch cylinder position switch sends a signal, indicating that the transfer case output shaft is disengaged from the hydraulic motor 2. The electromagnet YV4 of the second electromagnetic reversing valve 5 and the electromagnets YV1 and YV2 of the closed hydraulic pump 1 are all de-energized. At this point, the marking vehicle switches to the mechanical travel mode.

[0023] (3) When the marking vehicle needs emergency braking during hydraulic travel, the brake pedal of the vehicle chassis is stepped on. The electromagnet YV3 of the first electromagnetic reversing valve 3 is energized to connect the two oil ports A and B of the hydraulic motor 2 and lose power. The hydraulic motor 2 is in a floating state and will not cause impact on the hydraulic system. The marking vehicle is braked by the chassis brake system, which is more stable and reliable. On the other hand, during normal braking, the brake pedal does not need to be stepped on to achieve braking by reducing the displacement of the closed hydraulic pump 1. After the marking vehicle is stable, the current of the electromagnet YV1 or YV2 of the closed hydraulic pump 1 is turned off.

[0024] The closed hydraulic pump 1, hydraulic motor 2, first electromagnetic reversing valve 3, hydraulic shuttle valve 4, second electromagnetic reversing valve 5, low-pressure relief valve 6, hydraulic oil radiator 7, hydraulic oil tank 8, transfer case, switching cylinder and other components in the present invention are all existing technologies, and the specific structure and working principle are not repeated here. In addition, the automatic control and signal transmission in the present invention do not require new computer programs.

[0025] This embodiment does not impose any formal restrictions on the shape, material, structure, etc. of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are within the scope of protection of the technical solution of the present invention.

Claims

1. A method for controlling a hydraulic travel system for a marking vehicle, characterized in that: The hydraulic travel system for the marking vehicle includes a closed hydraulic pump, a hydraulic motor, a first solenoid reversing valve, a hydraulic shuttle valve, a second solenoid reversing valve, and a low-pressure relief valve; the two oil outlets PA and PB of the closed hydraulic pump are respectively connected to the two oil ports A and B of the hydraulic motor; the two oil ports P1 and P2 of the first solenoid reversing valve are respectively connected to the two oil ports A and B of the hydraulic motor, and the first solenoid reversing valve and the hydraulic motor form a parallel circuit; the two oil ports of the hydraulic shuttle valve are respectively connected to the two oil ports A and B of the hydraulic motor, and the control port C of the hydraulic shuttle valve is connected to the second solenoid reversing valve; the oil outlet of the second solenoid reversing valve is connected to the oil inlet of the low-pressure relief valve; The hydraulic travel system for the marking vehicle also includes a hydraulic oil radiator and a hydraulic oil tank. The closed hydraulic pump is driven by the transfer case to suck oil from the hydraulic oil tank. The oil unloading port of the closed hydraulic pump, the oil drain port of the hydraulic motor and the overflow port of the low-pressure overflow valve are all connected to the oil inlet of the hydraulic oil radiator; the oil outlet of the hydraulic oil radiator is connected to the oil inlet of the hydraulic oil tank. The first solenoid reversing valve has a two-way check function. The electromagnet YV3 of the first solenoid reversing valve is associated with the brake signal of the striping vehicle chassis. When the chassis brake pedal is pressed, the electromagnet YV3 is also energized. When the brake pedal is released, the electromagnet YV3 is de-energized. The hydraulic motor and the output shaft of the striping vehicle transfer case are connected or disconnected by the switching cylinder. The electromagnet YV4 of the second solenoid reversing valve is associated with the switching cylinder control button. Whether the output shaft of the transfer case and the hydraulic motor are connected or disconnected, the electromagnet YV4 is energized. The control method includes the following three modes: (1) When the hydraulic motor is coupled with the transfer case output shaft: first, pull up the handbrake of the marking vehicle chassis; then, couple the closed hydraulic pump with the transfer case, and the marking vehicle chassis drives the transfer case to drive the closed hydraulic pump to work; then, press the switch cylinder control button, and the switch cylinder action presses the meshing pair of gear end faces together, so that the transfer case output shaft is coupled with the hydraulic motor; at the same time, the electromagnet YV4 of the second electromagnetic reversing valve is energized, and the low-pressure relief valve works at this time; finally, the electromagnets YV1 and YV2 of the closed hydraulic pump are energized in sequence at intervals of 0.5 seconds, and the electrical signal should be as small as possible, driving the hydraulic motor to rotate forward and reverse at low speed and low torque. When the gears are engaged in place, the switch cylinder position switch sends a signal, indicating that the transfer case output shaft is coupled with the hydraulic motor in place, and the electromagnet YV4 of the second electromagnetic reversing valve and the electromagnets YV1 and YV2 of the closed hydraulic pump are all de-energized. At this point, the marking vehicle switches to the hydraulic travel mode; (2) When the hydraulic motor is disengaged from the transfer case output shaft: pull up the car chassis handbrake, press the switch cylinder control button, the switch cylinder action will separate the meshing pair of gear end faces, the transfer case output shaft is disengaged from the hydraulic motor, and at the same time the electromagnet YV4 of the second electromagnetic reversing valve is energized, and then the electromagnets YV1 and YV2 of the closed hydraulic pump are energized in sequence at intervals of 0.5 seconds. The electrical signal should be as small as possible to drive the hydraulic motor to rotate forward and reverse at low speed and low torque. When the meshing gears are disengaged, the switch cylinder position switch sends a signal, indicating that the transfer case output shaft is disengaged from the hydraulic motor, and the electromagnet YV4 of the second electromagnetic reversing valve and the electromagnets YV1 and YV2 of the closed hydraulic pump are all de-energized. At this point, the marking vehicle switches to the mechanical travel mode; (3) When the marking vehicle needs emergency braking during hydraulic travel, step on the brake pedal of the vehicle chassis, and the electromagnet YV3 of the first electromagnetic reversing valve will be energized to connect the two oil ports A and B of the hydraulic motor and lose power. The hydraulic motor is in a floating state and will not cause impact on the hydraulic system. The marking vehicle relies on the brake system of the chassis to achieve braking, which is more stable and reliable. On the other hand, during normal braking, the brake pedal can be reduced to achieve braking by reducing the displacement of the closed hydraulic pump. After the marking vehicle is stable, the current of the closed hydraulic pump electromagnet YV1 or YV2 is turned off.

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