Parking brake system and operating method thereof, and agricultural machine

Abstract

The present invention relates to the field of hydraulic braking. Disclosed are a parking brake system and an agricultural machine. The parking brake system comprises a parking brake, a first reversing valve, a second reversing valve, and an energy accumulator, wherein a working port of the first reversing valve is connected to a rod cavity of a brake cylinder of the parking brake, an oil inlet of the first reversing valve is connected to an oil intake circuit, an oil return port of the first reversing valve is connected to an oil return circuit, and in a power-off state, the working port of the first reversing valve is in communication with the oil return port; an oil outlet of the second reversing valve is connected to the oil return circuit, and in the power-off state, an oil inlet of the second reversing valve is in communication with the oil outlet thereof; and the energy accumulator is connected to the oil inlet of the second reversing valve. The parking brake system of the present invention can prevent tires from locking up when an agricultural machine is accidentally powered off during travelling, and also enables the agricultural machine to slowly and smoothly decelerate until the agricultural machine stops and parks.

Description

Parking brake system, working method thereof and agricultural machine

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Chinese Patent Application No. 202411243518.8, filed September 5, 2024, the contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application belongs to the field of hydraulic braking, and in particular, relates to a parking brake system, a working method thereof and an agricultural machine. BACKGROUND

[0004] The parking brake system of the existing agricultural machine (such as a silage machine) usually comprises a parking brake and a reversing valve, and the parking brake cylinder of the parking brake is controlled by the reversing valve to switch the parking brake between the braking state and the unbraking state. The specific working mode is as follows: when the reversing valve is switched to the first valve position by power supply, the spring in the rodless cavity of the brake cylinder is compressed to make the piston rod retract, and the parking brake is switched to the unbraking state; when the reversing valve is switched to the second valve position by power loss, the spring in the rodless cavity of the brake cylinder is reset to make the piston rod extend, and the parking brake is switched to the braking state. This working mode has a large safety hazard. When the agricultural machine is running and power loss occurs accidentally, the reversing valve will be switched to the second valve position by power loss immediately, which makes the parking brake switched to the braking state immediately, and the tire is locked, and at this time, a safety accident such as rollover is likely to occur. SUMMARY

[0005] In view of the above-mentioned deficiencies or defects in the prior art, the present application provides a parking brake system and an agricultural machine, which aims to solve the technical problem of the existing parking brake system of the agricultural machine having a large safety hazard and a low safety factor.

[0006] To achieve the above-mentioned purpose, the present application provides a parking brake system, which comprises:

[0007] a parking brake;

[0008] an oil return circuit comprising a damping member;

[0009] a first reversing valve, a working oil port of the first reversing valve being connected with a rod cavity of a brake cylinder of the parking brake, an oil return port of the first reversing valve being connected with an oil inlet end of the oil return circuit, the working oil port and the oil return port of the first reversing valve being in communication in a power loss state, the working oil port of the first reversing valve being in communication with the oil inlet port in a power supply state;

[0010] a second reversing valve, an oil inlet of the second reversing valve being connected with the accumulator, an oil outlet of the second reversing valve being connected with the oil return oil path and the connection position being located between an oil inlet end of the oil return oil path and the damping member, the oil inlet and the oil outlet of the second reversing valve being communicated in the power-off state, and the oil inlet and the oil outlet of the second reversing valve being disconnected in the power-on state;

[0011] an oil inlet oil path, respectively connected with the oil inlet of the first reversing valve and the accumulator.

[0012] Optionally, the oil inlet oil path comprises:

[0013] a hydraulic pump;

[0014] a one-way valve, an oil inlet of the one-way valve being connected with an output end of the hydraulic pump;

[0015] a first oil path, one end of the first oil path being connected with an oil outlet of the one-way valve, and the other end of the first oil path being connected with the oil inlet of the first reversing valve, and the first oil path being further connected with the accumulator.

[0016] Optionally, the oil inlet oil path further comprises an overflow valve, and the overflow valve is arranged in parallel with the hydraulic pump.

[0017] Optionally, the damping member is a throttle valve.

[0018] Optionally, the first reversing valve is a proportional valve, and the parking brake system further comprises a controller, the controller being communicatively connected with the first reversing valve and being configured to gradually increase an opening degree of a flow path between a working oil port and a return port of the first reversing valve after receiving an emergency stop signal.

[0019] Optionally, the parking brake system further comprises a vehicle speed detector, the controller being communicatively connected with the vehicle speed detector and being configured to gradually increase the opening degree of the flow path between the working oil port and the return port of the first reversing valve according to vehicle speed information detected by the vehicle speed detector after receiving the emergency stop signal.

[0020] Optionally, the vehicle speed detector is a tire rotation speed sensor.

[0021] The application further provides an agricultural machine comprising the above parking brake system.

[0022] The application further provides a working method of the above parking brake system, comprising the following processes:

[0023] determining that the agricultural machine is switched to a driving gear position, switching the first reversing valve and the second reversing valve to a power-on state, and switching the second reversing valve to a power-off state synchronously when the first reversing valve is switched from the power-on state to a power-off state.

[0024] Optionally, the working method further comprises:

[0025] determining that the agricultural machine is in an emergency stop or the hydraulic pump loses power, gradually increasing the opening degree of the flow path between the working oil port and the return oil port of the first reversing valve.

[0026] With the above technical solution, the parking brake system of the present application can be applied to agricultural machines. When the parking brake system loses power due to unexpected power loss during the running of the agricultural machine, the first reversing valve and the second reversing valve are both in a power loss state at the same time. The working oil port of the first reversing valve is in communication with the return oil port to make the rod cavity of the brake cylinder of the parking brake in communication with the return oil circuit. At the same time, the oil inlet and the oil outlet of the second reversing valve are in communication to make the accumulator in communication with the return oil circuit. At this time, under the hydraulic damping action of the damping member, the rod cavity of the brake cylinder can be prevented from being instantaneously depressurized through the return oil circuit, and at the same time, the accumulator can provide hydraulic energy to the brake cylinder through the return oil circuit and the first reversing valve within a period of time, preventing the hydraulic oil in the rod cavity of the brake cylinder from flowing back, and avoiding the situation that the parking brake immediately brakes the tires to cause a safety accident when the power is lost unexpectedly. Moreover, as the hydraulic energy provided by the accumulator gradually decreases, the hydraulic oil in the rod cavity of the brake cylinder will gradually and slowly flow back through the return oil circuit, and the parking brake will relatively smoothly and slowly perform parking braking, so that the agricultural machine can be parked smoothly. That is, when the power is lost unexpectedly during the running of the agricultural machine, the parking brake system can prevent the tires of the agricultural machine from being locked, and at the same time, can make the agricultural machine slow down relatively smoothly until it is parked, thereby effectively further improving the safety factor under the condition of unexpected power loss. BRIEF DESCRIPTION OF DRAWINGS

[0027] FIG. 1 is a structural schematic diagram of a parking brake system according to a specific embodiment of the present application.

[0028] Reference sign explanation 1 brake cylinder 2 first reversing valve 3 second reversing valve 4 accumulator 5 hydraulic pump 6 one-way valve 7 first oil circuit 8 overflow valve 9 second oil circuit 10 damping member 11 third oil circuit DETAILED DESCRIPTION

[0029] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0030] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0031] In the present application, the orientation words such as 'upper', 'lower', 'top', 'bottom' are generally used for the directions shown in the drawings or the positional relationship between the components in the vertical, perpendicular or gravity direction unless otherwise stated.

[0032] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0033] The present application first provides a parking brake system.

[0034] In an embodiment, referring to Fig. 1, the parking brake system comprises:

[0035] a parking brake;

[0036] an oil return circuit comprising a damping member 10;

[0038] a first directional control valve 2, a working oil port of the first directional control valve 2 being connected with a rod cavity of a brake cylinder 1 of the parking brake, an oil return port of the first directional control valve 2 being connected with an oil inlet end of the oil return circuit, the working oil port and the oil return port of the first directional control valve 2 being communicated in a power-off state, the working oil port of the first directional control valve 2 being communicated with the oil inlet port in a power-on state;

[0039] a second directional control valve 3 and an accumulator 4, an oil inlet port of the second directional control valve 3 being connected with the accumulator 4, an oil outlet port of the second directional control valve 3 being connected with the oil return circuit and the connection position being located between the oil inlet end of the oil return circuit and the damping member 10, the oil inlet port and the oil outlet port of the second directional control valve 3 being communicated in a power-off state, the oil inlet port and the oil outlet port of the second directional control valve 3 being disconnected in a power-on state;

[0040] an oil inlet circuit, being connected with the oil inlet port of the first directional control valve 2 and the accumulator 4 respectively.

[0041] The parking brake system of the present embodiment can be applied to agricultural machinery. When the agricultural machinery is switched to a driving gear, the first directional control valve 2 is in a power-on state, the working oil port of the first directional control valve 2 is communicated with the oil inlet port so that the rod cavity of the brake cylinder 1 of the parking brake is communicated with the oil inlet circuit. In this way, the oil inlet circuit can continuously provide hydraulic energy to the brake cylinder 1 through the first directional control valve 2, so that the parking brake is kept in a brake release state.

[0042] When the agricultural machine is powered off accidentally during driving, the first reversing valve 2 and the second reversing valve 3 are both in the powered-off state at the same time, the working oil port of the first reversing valve 2 is in communication with the return oil port to make the rod cavity of the parking brake cylinder 1 in communication with the return oil circuit, at the same time, the oil inlet and the oil outlet of the second reversing valve 3 are in communication to make the accumulator 4 in communication with the return oil circuit, at this time, the hydraulic damping effect of the damping member 10 can avoid the rod cavity of the parking brake cylinder 1 from being instantaneously depressurized through the return oil circuit, at the same time, the accumulator 4 can provide hydraulic energy to the parking brake cylinder 1 through the return oil circuit and the first reversing valve 2 within a period of time, so that the rod cavity of the parking brake cylinder 1 can be kept at high pressure, the hydraulic oil in the rod cavity of the parking brake cylinder 1 can be prevented from flowing back, and the situation that the tire is locked immediately to cause a safety accident when the parking brake is suddenly powered off can be avoided. Moreover, as the hydraulic energy provided by the accumulator 4 gradually decreases, the hydraulic oil in the rod cavity of the parking brake cylinder 1 will gradually and slowly flow back through the return oil circuit, the parking brake will be parked relatively smoothly and slowly, and the agricultural machine can be parked smoothly, that is, when the agricultural machine is powered off accidentally, the parking brake system can avoid the tire of the agricultural machine from being locked, and at the same time, the agricultural machine can be slowed down relatively slowly and smoothly until it is parked, so that the safety factor under the condition of accidental power-off can be effectively further improved.

[0042] In order to ensure that the second reversing valve 3 can be powered off synchronously with the first reversing valve 2, the second reversing valve 3 can be arranged in the same control circuit as the first reversing valve 2, or a controller respectively in communication connection with the second reversing valve 3 and the first reversing valve 2 can be arranged, and when it is determined that the first reversing valve 2 is powered off, the second reversing valve 3 can be timely controlled to be powered off synchronously by the controller.

[0043] Specifically, the first reversing valve 2 can be a two-position three-way reversing valve, and the valve core has a first valve position and a second valve position, in the powered-off state, the valve core of the first reversing valve 2 is driven to the first valve position by the elastic force of the spring, the working oil port of the first reversing valve 2 is in communication with the return oil port, in the powered-on state, the valve core of the first reversing valve 2 is switched to the second valve position by overcoming the elastic force of the spring under the action of the electromagnet, and the working oil port of the first reversing valve 2 is in communication with the oil inlet.

[0044] Specifically, the return oil circuit can further include a second oil circuit 9 and a third oil circuit 11, one end of the second oil circuit 9 is connected with the return oil port of the first reversing valve 2, the other end is connected with one port of the damping member 10, one end of the third oil circuit 11 is connected with the other port of the damping member 10, and the oil outlet of the second reversing valve 3 is connected with the second oil circuit 9.

[0045] Specifically, the first reversing valve 2 and the second reversing valve 3 can be electromagnetic reversing valves or electric reversing valves and the like which can be controlled by electric control.

[0046] In the embodiment, the oil inlet oil circuit is connected with the oil inlet of the first reversing valve 2 and the accumulator 4, and the working oil port of the first reversing valve 2 in the powered state is communicated with the oil inlet. In this way, when the agricultural machine is switched to the driving gear, the first reversing valve 2 is in the powered state, the working oil port of the first reversing valve 2 is communicated with the oil inlet to make the rod cavity of the brake cylinder 1 of the parking brake communicated with the oil inlet oil circuit, and the accumulator 4 can complete energy storage at the same time.

[0047] In actual application, the input end of the oil inlet oil circuit and the output end of the oil return oil circuit can be connected with the hydraulic oil tank to realize oil supply and oil return.

[0048] In the embodiment, the oil inlet and the oil outlet of the second reversing valve 3 in the powered state are disconnected. In this way, part of the hydraulic oil of the oil inlet oil circuit can be prevented from entering the oil return oil circuit through the second reversing valve 3 when the agricultural machine is switched to the driving gear.

[0049] Specifically, the second reversing valve 3 can be a two-position two-way reversing valve, and the spool has a first valve position and a second valve position. In the unpowered state, the spool of the second reversing valve 3 is driven by the elastic force of the spring to be in the first valve position, and the oil inlet and the oil outlet of the second reversing valve 3 are communicated. In the powered state, the spool of the second reversing valve 3 is switched to the second valve position by overcoming the elastic force of the spring under the action of the electromagnet, and the oil inlet and the oil outlet of the second reversing valve 3 are disconnected.

[0050] In an embodiment, the oil inlet oil circuit comprises:

[0051] a hydraulic pump 5;

[0052] a one-way valve 6, the oil inlet of the one-way valve 6 being connected with the output end of the hydraulic pump 5;

[0053] a first oil circuit 7, one end of the first oil circuit 7 being connected with the oil outlet of the one-way valve 6, the other end of the first oil circuit 7 being connected with the oil inlet of the first reversing valve 2, and the first oil circuit 7 being further connected with the accumulator 4;

[0054] In actual application, the input end of the hydraulic pump 5 can be connected with the hydraulic oil tank.

[0055] In the embodiment, when the hydraulic pump 5 is unexpectedly stopped, due to the action of the one-way valve 6, the accumulator 4 can be prevented from being depressurized, and the hydraulic oil in the brake cylinder 1 can also be prevented from being instantaneously returned and depressurized, so that the brake cylinder 1 is pressurized in a short time, and the situation that the tire is immediately braked to be locked when the hydraulic pump 5 is stopped is avoided.

[0056] In an embodiment, the oil inlet oil circuit further comprises an overflow valve 8, and the overflow valve 8 is arranged in parallel with the hydraulic pump 5. In this way, the input hydraulic pressure of the hydraulic pump 5 can be prevented from being too high through the overflow valve 8.

[0057] Specifically, the overflow valve 8 can be a manual adjustment structure or an electric adjustment structure.

[0058] In an embodiment, the damping member 10 is a throttle valve. In this way, the effect of hydraulic damping is achieved by the throttling effect of the throttle valve.

[0059] Of course, in other embodiments, the damping member 10 can also be a speed regulating valve or a damping valve.

[0060] In an embodiment, the first directional valve 2 is a proportional valve, and the parking brake system further comprises a controller, which is in communication connection with the first directional valve 2 and is configured to gradually increase the flow passage opening degree between the working oil port and the return oil port of the first directional valve 2 after receiving an emergency stop signal.

[0061] It can be understood that the agricultural machine is generally provided with an emergency stop switch, and the engine of the agricultural machine can be quickly stopped through the emergency stop switch in an emergency, at which time the hydraulic pump 5 will also be stopped. In this embodiment, the first directional valve 2 is set as a proportional valve, and the controller is configured to gradually increase the flow passage opening degree between the working oil port and the return oil port of the first directional valve 2 after receiving an emergency stop signal generated by pressing the emergency stop switch. In this way, based on the characteristics of the proportional valve, after the hydraulic pump 5 is stopped, the first directional valve 2 can be gradually and slowly increased in the flow passage opening degree between the working oil port and the return oil port under the control of the controller, thereby controlling the return oil speed of the brake cylinder 1, so that the brake cylinder 1 can be slowly depressurized, avoiding the situation that the brake cylinder 1 is instantaneously depressurized to cause the parking brake to immediately brake and make the tire locked, so that the agricultural machine can be smoothly and slowly parked in the case of emergency stop.

[0062] Of course, in other embodiments, the second directional valve 3 can also be a servo valve.

[0063] In an embodiment, the parking brake system further comprises a vehicle speed detector, and the controller is in communication connection with the vehicle speed detector and is configured to gradually increase the flow passage opening degree between the working oil port and the return oil port of the first directional valve 2 according to the vehicle speed information detected by the vehicle speed detector after receiving an emergency stop signal. In this way, the flow passage opening degree between the working oil port and the return oil port of the first directional valve 2 can be adjusted according to the actual vehicle speed, so that the braking degree of the parking brake can be matched with the vehicle speed, and the reliability of the parking brake of the agricultural machine in the case of emergency stop can be further improved.

[0064] In an embodiment, the vehicle speed detector is a tire rotation speed sensor.

[0065] In this embodiment, the vehicle speed detector determines the driving speed of the agricultural machine by detecting the rotation speed of the tire of the agricultural machine.

[0066] Of course, in other embodiments, the vehicle speed detector can also be a GPS speedometer.

[0067] The application further provides an agricultural machine comprising the parking brake system as described above. The specific structure of the parking brake system is referred to the above-mentioned embodiments. Since the agricultural machine adopts all the technical solutions of the above-mentioned embodiments, it has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0068] In addition, the agricultural machine can be, for example, a silage machine, a tractor, etc.

[0069] The application further provides a working method of the parking brake system.

[0070] In an embodiment, the working method comprises the following process:

[0071] After determining that the agricultural machine switches to the traveling gear, the first reversing valve 2 and the second reversing valve 3 are switched to the energized state. When the first reversing valve 2 is switched from the energized state to the de-energized state, the second reversing valve 3 is synchronously switched to the de-energized state.

[0072] It can be understood that, after determining that the agricultural machine switches to the traveling gear, the first reversing valve 2 is switched to the energized state, and the working oil port of the first reversing valve 2 is communicated with the oil inlet port, so that the rod cavity of the brake cylinder 1 of the parking brake is communicated with the oil inlet oil path. In this way, the oil inlet oil path can continuously provide hydraulic energy to the brake cylinder 1 through the first reversing valve 2, so that the parking brake is kept in the brake release state, and the agricultural machine can normally travel.

[0073] When the agricultural machine is accidentally de-energized or the first reversing valve 2 is switched from the energized state to the de-energized state due to other reasons during traveling, the second reversing valve 3 is synchronously switched to the de-energized state. In this way, the accumulator 4 is communicated with the oil return oil path, and the rod cavity of the brake cylinder 1 can be prevented from being instantaneously depressurized through the oil return oil path under the hydraulic damping action of the damping member 10. At the same time, the accumulator 4 can provide hydraulic energy to the brake cylinder 1 through the oil return oil path and the first reversing valve 2 within a period of time, so that the rod cavity of the brake cylinder 1 is kept at high pressure, the hydraulic oil in the rod cavity of the brake cylinder 1 is prevented from flowing back, and the situation that the tire is immediately braked to cause a safety accident when the parking brake is braked due to accidental de-energization is avoided.

[0074] In an embodiment, the working method further comprises:

[0075] After determining that the agricultural machine is suddenly stopped or the hydraulic pump 5 loses power, the flow path opening degree between the working oil port and the oil return port of the first reversing valve 2 is gradually increased.

[0076] In the embodiment, in order to continuously control the flow path opening degree between the working oil port and the return oil port of the first reversing valve 2, the first reversing valve 2 is provided as a proportional valve, and after the hydraulic pump 5 is stopped, the first reversing valve 2 is gradually and slowly increased in the flow path opening degree between the working oil port and the return oil port based on the characteristics of the proportional valve, so as to control the return oil speed of the brake cylinder 1, and the brake cylinder 1 can be slowly depressurized, so as to avoid the situation that the parking brake is immediately braked to cause the tire to be locked when the brake cylinder 1 is instantaneously depressurized, and the agricultural machine can be smoothly and slowly parked in the case of emergency stop.

[0077] In the description of the present application, it should be understood that the terms "first", "second" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0078] In the present application, unless otherwise specifically defined and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected or communicate with each other; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise specifically limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0079] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples without contradiction.

[0080] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A parking brake system characterized by, The parking brake system comprises: a parking brake; an oil return oil path comprising a damping element (10); a first directional valve (2), a working oil port of the first directional valve (2) being connected with a rod cavity of a brake cylinder (1) of the parking brake, an oil return port of the first directional valve (2) being connected with an oil inlet end of the oil return oil path, the working oil port and the oil return port of the first directional valve (2) being communicated in a power-off state, the working oil port and an oil inlet port of the first directional valve (2) being communicated in a power-on state; a second directional valve (3) and an accumulator (4), an oil inlet port of the second directional valve (3) being connected with the accumulator (4), an oil outlet port of the second directional valve (3) being connected with the oil return oil path, and the connection position being located between the oil inlet end of the oil return oil path and the damping element (10), the oil inlet port and the oil outlet port of the second directional valve (3) being communicated in the power-off state, and the oil inlet port and the oil outlet port of the second directional valve (3) being disconnected in the power-on state; an oil inlet oil path, the oil inlet oil path being connected with the oil inlet port of the first directional valve (2) and the accumulator (4) respectively.

2. The parking brake system of claim 1, wherein, The oil inlet oil path comprises: a hydraulic pump (5); a check valve (6), an oil inlet port of the check valve (6) being connected with an output end of the hydraulic pump (5); a first oil path (7), one end of the first oil path (7) being connected with an oil outlet port of the check valve (6), the other end of the first oil path (7) being connected with the oil inlet port of the first directional valve (2), and the first oil path (7) being further connected with the accumulator (4).

3. The parking brake system of claim 2, wherein, The oil inlet oil path further comprises a relief valve (8), the relief valve (8) being arranged in parallel with the hydraulic pump (5).

4. The parking brake system of claim 1, wherein, The damping element (10) is a throttle valve.

5. The parking brake system according to claim 1 or 2, characterized in that The first directional valve (2) is a proportional valve, and the parking brake system further comprises a controller, the controller being communicatively connected with the first directional valve (2) and being configured to gradually increase an opening degree of a flow path between the working oil port and the oil return port of the first directional valve (2) after receiving an emergency stop signal.

6. The parking brake system of claim 5, wherein, The parking brake system further comprises a vehicle speed detector, the controller being communicatively connected with the vehicle speed detector and being configured to gradually increase the opening degree of the flow path between the working oil port and the oil return port of the first directional valve (2) according to vehicle speed information detected by the vehicle speed detector after receiving the emergency stop signal.

7. The parking brake system of claim 6, wherein, The vehicle speed detector is a tire rotation speed sensor.

8. An agricultural machine characterized by, The agricultural machine comprises the parking brake system according to any one of claims 1 to 7.

9. The method of operating a parking brake system of any one of claims 1 to 7, wherein, The working method comprises the following process: after determining that the agricultural machine is switched to a driving gear, switching the first directional valve (2) and the second directional valve (3) to a power-on state, and switching the first directional valve (2) from the power-on state to a power-off state, synchronously switching the second directional valve (3) to the power-off state.

10. The method of working according to claim 9, characterized in that, The working method further comprises: after determining that the agricultural machine is in an emergency stop state or the hydraulic pump (5) loses power, gradually increasing the opening degree of the flow path between the working oil port and the oil return port of the first directional valve (2).

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