Hydraulic integrated valve block, hydraulic braking system and electric forklift hydraulic braking method

Abstract

The invention provides an integrated valve block, a hydraulic braking system and an electric forklift hydraulic braking method.The hydraulic integrated valve block comprises a valve body, and an oil inlet P0, an oil return port and a detection oil port M connected with a pressure sensor are formed in the valve body; an OPS electromagnetic valve is connected between the oil inlet P0 and the pilot oil port P1, an unloading valve is connected between the oil inlet P0 and the energy storage oil port P2, a logic valve is connected between the oil inlet P0 and the cooling oil port D, and the unloading valve is connected with the logic valve through an oil way. The oil inlet end of the brake oil port P3 is connected with the energy storage oil port P2 through a two-position three-way electromagnetic valve. Control oil ways of a service brake, a parking brake, a drive axle, an OPS function and the like are integrated into the integrated valve block and are connected and controlled through oil ports respectively. The hydraulic system is easy to install, compact in structure and convenient to install and maintain, and cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of forklifts, and in particular to a hydraulic integrated valve block, a hydraulic braking system and a hydraulic braking method for an electric forklift. Background Art

[0002] The service brake and parking brake of heavy forklifts are mostly realized by hydraulic system. In order to ensure the reliability of braking, the whole hydraulic system includes two hydraulic circuits: service brake and parking brake. At the same time, the service brake installed on the drive axle generates heat due to the friction of the friction plate for a long time during braking, and needs to be flushed and cooled with hydraulic oil. In addition, because the hydraulic system of electric forklifts is usually driven by the motor to drive the hydraulic pump to supply oil to meet the lifting and tilting operation requirements of the forklift. If the power is cut off, the hydraulic pump will stop working, but the operation of the working device descending by its own weight is not restricted. This may cause the forklift to continue to work without human operation, causing safety accidents. Therefore, in order to improve safety, the new safety regulations of the vehicle require that the working device of the whole vehicle has an OPS protection function to ensure that the operator can only operate in the correct driving position, thereby reducing safety accidents caused by misoperation.

[0003] However, the braking system of the existing electric forklift involves control oil circuits such as the service brake, parking brake, drive axle cooling, and OPS function, so many hydraulic components are required, resulting in poor assembly and maintenance performance and high costs. Summary of the invention

[0004] In order to solve the above problems, the present invention provides an integrated valve block, a hydraulic braking system and an electric forklift hydraulic braking method which integrate hydraulic OPS function, parking brake, service brake, pilot oil source, drive axle cooling and other functions.

[0005] The specific technical solution adopted by the present invention is as follows:

[0006] The first invention object of the present invention is to provide a hydraulic integrated valve block, comprising a valve body, on which an oil inlet P0, an oil return port 1 T1 and an oil return port 2 T2 are provided; the valve body is also provided with a cooling oil port D connected to a drive axle, a pilot oil port P1 connected to a pilot handle, an energy storage oil port P2 connected to an accumulator 1, a brake oil port P3 connected to a parking brake, and a detection oil port M connected to a pressure sensor;

[0007] The oil inlet P0 is respectively connected to the pilot oil port P1, the energy storage oil port P2, the brake oil port P3, the cooling oil port D, and the detection oil port M. An OPS solenoid valve is connected between the oil inlet P0 and the pilot oil port P1, a unloading valve is connected between the oil inlet P0 and the energy storage oil port P2, a logic valve is connected between the oil inlet P0 and the cooling oil port D, and the unloading valve and the logic valve are connected through an oil circuit; the oil inlet end of the brake oil port P3 is connected to the energy storage oil port P2 through a two-position three-way solenoid valve.

[0008] In a further solution, the oil inlet P0 is connected to the energy storage oil port P2 through the throttle valve 1 and the one-way valve 2 in sequence, and the oil outlet end of the one-way valve 2 is connected to the OPS solenoid valve through the pressure reducing valve.

[0009] In a further solution, the oil outlet end of the OPS solenoid valve is connected to the pilot oil port P1 through a one-way valve 4, and the oil return end is connected to the oil return port 1 T1.

[0010] In a further solution, a throttle valve 2 and a check valve 3 are connected in sequence between the two-position three-way solenoid valve and the energy storage oil port P2; the oil return port of the two-position three-way solenoid valve is connected to the oil return port 2 T2 through the check valve 1;

[0011] The oil outlet end of the oil inlet P0 is connected to a relief valve, and the oil outlet end of the relief valve is connected to the second oil return port T2.

[0012] The second invention object of the present invention is to provide a hydraulic braking system for an electric forklift, including the above-mentioned hydraulic integrated valve block, the oil outlet end of the energy storage oil port P2 is also connected to a foot brake valve and a power cut-off switch, the foot brake valve is connected to the service brake, and the power cut-off switch is connected to the gearbox signal.

[0013] In a further solution, the oil outlet end of the brake oil port P3 is also connected to a low-pressure alarm switch for detecting the oil pressure of the hydraulic oil entering the parking brake through the brake oil port P3.

[0014] In a further solution, the oil outlet end of the pilot oil port P1 is also connected to an accumulator 2 for supplying hydraulic oil to the forklift mast.

[0015] In a further solution, the oil inlet P0 is connected to the oil tank through a hydraulic pump, and the hydraulic pump is electrically connected to a pump motor for driving; the oil return port 1 T1 and the oil return port 2 T2 are both connected to the oil tank.

[0016] The third invention object of the present invention is to provide a hydraulic braking method for an electric forklift, comprising the above-mentioned hydraulic braking system, comprising the following steps:

[0017] S1. After starting, the hydraulic pump guides the hydraulic oil into the hydraulic integrated valve block; at the same time, the oil pressure V0 of the accumulator 1 is detected. When the oil pressure V0 is lower than the lower limit value V1 of the filling of the accumulator 1, the hydraulic pump always fills the accumulator 1;

[0018] S2. When the oil pressure V0 reaches the upper limit value V2 of the filling of the accumulator 1, the unloading valve opens, and the hydraulic oil pushes the valve core of the logic valve through the unloading valve to connect to the oil circuit of the cooling oil port D. The hydraulic pump guides the hydraulic oil into the drive axle through the logic valve to cool it;

[0019] S3, when the oil pressure V0 is between V1 and V2, the unloading valve and the logic valve are closed, and the hydraulic oil discharged by the hydraulic pump continues to charge the accumulator;

[0020] S4, step on the brake pedal, the foot brake valve opens, and the hydraulic oil in the accumulator 1 is introduced into the service brake through the foot brake valve to release the service brake;

[0021] S5. Pull up the parking brake switch, the two-position three-way solenoid valve is energized and works in the right position, and the hydraulic oil in the accumulator 1 enters the parking brake through the two-position three-way solenoid valve to release the parking brake;

[0022] S6. When the parking brake switch is pressed, the two-position three-way solenoid valve loses power and works in the left position. The hydraulic oil in the accumulator 1 enters the drive axle through the two-position three-way solenoid valve to cool it.

[0023] S7, operate the pilot handle, the hydraulic oil exported by the hydraulic pump is introduced into the pilot handle through the OPS solenoid valve for pilot action,

[0024] In a further solution, in step S4, the oil pressure E1 of the accumulator 1 and the foot brake valve is detected. When the oil pressure E1 is lower than the pressure value E0 required by the service brake, the power cut-off switch is actuated to cut off the power output of the gearbox.

[0025] In a further solution, in steps S5 and S6, the low-pressure alarm switch detects the pressure value F1 of the hydraulic oil entering the parking brake. When the pressure value F1 is lower than the pressure F0 required for releasing the parking brake, the low-pressure alarm switch alarms.

[0026] In a further solution, in step S7, the switch of the OPS solenoid valve is installed under the seat of the cab. When the driver is in the normal working position, the switch of the OPS solenoid valve is turned on and energized, and the hydraulic oil derived from the hydraulic pump enters the pilot handle through the OPS solenoid valve for pilot action; when the driver is not in the normal working position, the OPS solenoid valve loses power, and the hydraulic oil flows back to the oil tank through the oil return port T1, the oil supply path of the pilot handle is cut off, and the forklift does not move when the pilot handle is operated.

[0027] The hydraulic integrated valve block of the present invention integrates the control oil circuits of the service brake, parking brake, drive axle, OPS function, etc. into the integrated valve block, and connects and controls them through oil ports respectively, making the hydraulic system easy to install, compact in structure, easy to install and maintain, and reducing costs.

[0028] The present invention detects the pressure value of the accumulator 1 by means of a pressure sensor. When the pressure value is lower than the lower limit value of the filling of the accumulator 1, the pump motor keeps working even if the electric forklift does not perform hydraulic action, driving the hydraulic pump to always fill the accumulator 1 with liquid. When the pressure value exceeds the upper limit value of the filling of the accumulator 1, the pump motor stops working, thereby achieving an energy-saving effect.

[0029] The present invention connects a low-pressure alarm switch to the oil outlet end of the brake oil port P3 of the hydraulic integrated valve block for detecting the pressure value of the hydraulic oil entering the parking brake. When the pressure value is lower than the pressure required for releasing the parking brake, the alarm light of the low-pressure alarm switch lights up, indicating that the pressure of the hydraulic oil is low and the vehicle needs to be stopped for maintenance.

[0030] The present invention installs a plurality of one-way valves on the internal oil circuit of the hydraulic integrated valve block, so as to control the flow direction of the hydraulic oil and prevent the hydraulic oil entering the parking brake or the foot brake valve from leaking, so as to ensure that the parking brake or the driving brake is always in a released state during the driving of the whole vehicle; at the same time, a throttle valve is added, so as to adjust the flow of the hydraulic oil to reduce the impact of the hydraulic oil on the accumulator or the two-position three-way solenoid valve; the present invention controls the direction of the hydraulic oil through the two-position three-way solenoid valve, which is used to release the parking brake or to cool the drive axle. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0032] Figure 1 It is a schematic diagram of the hydraulic integrated valve block of the present invention;

[0033] Figure 2 is a schematic diagram of a hydraulic brake system of the present invention;

[0034] In the figure: 1- oil tank, 2- hydraulic pump, 3- hydraulic integrated valve block, 31- overflow valve, 32- logic valve, 33- two-position three-way solenoid valve, 34- unloading valve, 35- pressure reducing valve, 36- OPS solenoid valve, 37- one-way valve 1, 38- one-way valve 2, 39- one-way valve 3, 310- one-way valve 4, 311- throttle valve 1, 312- throttle valve 2;

[0035] 4-parking brake, 5-low pressure alarm switch, 6-accumulator one, 7-power cut-off switch, 8-accumulator two, 9-pressure sensor, 10-drive axle, 11-foot brake valve, 12-pilot handle. DETAILED DESCRIPTION

[0036] The present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0037] In this application, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix", "fixed", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0038] Embodiment 1:

[0039] like Figure 1 As shown, a hydraulic integrated valve block includes a valve body, on which an oil inlet P0, an oil return port 1 T1 and an oil return port 2 T2 are provided; the valve body is also provided with a cooling oil port D connected to a drive axle 10, a pilot oil port P1 connected to a pilot handle 12, an energy storage oil port P2 connected to an accumulator 1 6, a brake oil port P3 connected to a parking brake 4, and a detection oil port M connected to a pressure sensor 9;

[0040] The oil inlet P0 is respectively connected to the pilot oil port P1, the energy storage oil port P2, the brake oil port P3, the cooling oil port D, and the detection oil port M. An OPS solenoid valve 36 is connected between the oil inlet P0 and the pilot oil port P1, a unloading valve 34 is connected between the oil inlet P0 and the energy storage oil port P2, a logic valve 32 is connected between the oil inlet P0 and the cooling oil port D, and the unloading valve 34 and the logic valve 32 are connected through an oil circuit; the oil inlet end of the brake oil port P3 is connected to the energy storage oil port P2 through a two-position three-way solenoid valve 33.

[0041] That is, the hydraulic integrated valve block of the present invention integrates the control oil circuits of the service brake, parking brake, drive axle, OPS function, etc., and connects and controls them through oil ports respectively, making the system installation simple, the structure compact, easy to install and maintain, and reducing costs.

[0042] In a further solution, the oil inlet P0 is connected to the energy storage oil port P2 through the throttle valve 1 311 and the one-way valve 2 38 in sequence, and the oil outlet end of the one-way valve 2 38 is connected to the OPS solenoid valve 36 through the pressure reducing valve 35.

[0043] In a further solution, the oil outlet end of the OPS solenoid valve 36 is connected to the pilot oil port P1 through a one-way valve 310, and the oil return end is connected to the oil return port T1.

[0044] In order to ensure the normal pressure in the brake system, the pressure sensor 9 is used to detect the pressure value of the accumulator 6 in the brake system. When it is lower than the lower limit pressure value of the filling of the accumulator 6, even if the forklift does not perform hydraulic action, the pump motor should always be in working state, driving the hydraulic pump 2 to work to fill the accumulator 6 and ensure its oil pressure is normal. The hydraulic oil from the oil inlet P0 of the hydraulic integrated valve block 3 enters the accumulator 6 through the throttle valve 1 311 and the check valve 2 38 for filling. The throttle valve 1 311 is mainly used to adjust the flow of hydraulic oil to reduce the impact of hydraulic oil on the accumulator 6, and the check valve 2 38 and the check valve 4 310 are used to control the flow direction of the hydraulic oil.

[0045] In a further solution, a throttle valve 2 312 and a check valve 3 39 are connected in sequence between the two-position three-way solenoid valve 33 and the energy storage oil port P2; the oil return port of the two-position three-way solenoid valve 33 is connected to the oil return port 2 T2 through a check valve 1 37. The function of the throttle valve 2 312 is the same as that of the throttle valve 1 311, which is also to adjust the flow of hydraulic oil. The main function of the check valve 3 39 is to prevent the hydraulic oil entering the parking brake 4 from leaking, so as to ensure that the parking brake 4 is always in the released state during the driving process of the whole vehicle; similarly, the function of the check valve 4 310 is also to keep the pressure of the accumulator 2 8 from leaking.

[0046] The oil outlet of the oil inlet P0 is connected to a relief valve 31, and the oil outlet of the relief valve 31 is connected to the second oil return port T2. When the hydraulic pump continues to work, the excess hydraulic oil can return to the oil tank from the relief valve 31.

[0047] Embodiment 2:

[0048] A hydraulic brake system for an electric forklift Figure 2 As shown, it includes the hydraulic integrated valve block 3 in embodiment 1, and the oil outlet end of the energy storage oil port P2 is also connected to the foot brake valve 11 and the power cut-off switch 7, the foot brake valve 11 is connected to the service brake, and the power cut-off switch 7 is connected to the gearbox signal. When the brake pedal is stepped on, the foot brake valve 11 opens, and the hydraulic oil in the accumulator 1 6 is introduced into the service brake through the foot brake valve 11 to release the service brake; and the pressure sensor electrically connected to the power cut-off switch 7 detects the oil pressure of the accumulator 1 6 and the foot brake valve 11. When the oil pressure is lower than the pressure value required by the service brake, the circuit of the power cut-off switch 7 is connected, and a signal is sent to the gearbox, so that the gearbox cuts off its power output line switch.

[0049] The oil outlet end of the brake oil port P3 is also connected to a low-pressure alarm switch 5 for detecting the oil pressure of the hydraulic oil entering the parking brake 4 through the brake oil port P3.

[0050] The pressure threshold of the low-pressure alarm switch 5 is set according to the hydraulic oil pressure required to release the parking brake 4. When the oil pressure detected by the low-pressure alarm switch 5 is lower than the pressure threshold, the low-pressure alarm switch 5 starts the alarm, that is, the alarm light comes on, indicating that the pressure of the hydraulic oil is low and the vehicle needs to be stopped for maintenance.

[0051] In this embodiment, the oil outlet of the pilot oil port P1 is also connected to an accumulator 2 8 for supplying hydraulic oil to the forklift mast. That is, when the vehicle is turned off or fails, the accumulator 2 8 can provide a certain amount of hydraulic oil to the mast to ensure that the fork can return to a safe position.

[0052] In this embodiment, the oil inlet P0 of the hydraulic integrated valve block 3 is connected to the oil tank 1 through the hydraulic pump 2, and the hydraulic pump 2 is electrically connected to the pump motor for driving; the oil return port 1 T1 and the oil return port 2 T2 are both connected to the oil tank 1 for oil return.

[0053] Embodiment 3:

[0054] This embodiment provides a hydraulic braking method for an electric forklift, which includes the hydraulic braking system described in Embodiment 2, and the braking steps are as follows:

[0055] S1. After starting, the hydraulic pump 2 introduces the hydraulic oil into the hydraulic integrated valve block 3; at the same time, the pressure sensor 9 is used to instantly detect the oil pressure V0 of the accumulator 6, and the lower limit value V1 and the upper limit value V2 of the filling of the accumulator 6 are set in advance; V1 and V2 can be set according to the capacity of the accumulator.

[0056] When the oil pressure V0 is lower than the lower limit value V1 of the filling of accumulator 6, even if the electric forklift does not perform hydraulic action, the pump motor keeps working, driving the hydraulic pump 2 to always fill the accumulator 6; that is, the hydraulic oil from the oil inlet P0 of the integrated valve block 3 enters the accumulator 6 through the throttle valve 1 311 and the one-way valve 2 38 to fill the accumulator 6.

[0057] S2. When the oil pressure V0 reaches the upper limit value V2 of the filling of the accumulator 6, the unloading valve 34 is controlled to open, and the hydraulic oil pushes the valve core of the logic valve 32 through the unloading valve 34 to connect the oil ports K11 and K12, so that the hydraulic oil flows from the oil inlet P0 of the integrated valve block 3 through the oil ports K11 and K12 of the logic valve 32, and then from the cooling oil port D into the drive axle 10 for cooling;

[0058] S3, when the oil pressure V0 is between V1 and V2, the unloading valve 34 is closed, the oil ports K11 and K12 of the logic valve 32 are disconnected, and the hydraulic oil derived from the hydraulic pump 2 continues to charge the accumulator 6;

[0059] S4, step on the brake pedal, the foot brake valve 11 opens, and the hydraulic oil in the accumulator 6 is introduced into the service brake through the foot brake valve 11 to release the service brake;

[0060] The pressure sensor electrically connected to the power cut-off switch 7 detects the oil pressure E1 of the accumulator 6 and the foot brake valve 11. When the oil pressure E1 is lower than the pressure value E0 required by the service brake, the circuit of the power cut-off switch 7 is connected and a signal is sent to the gearbox, and the gearbox cuts off its power output line switch.

[0061] S5, pull up the parking brake switch, the two-position three-way solenoid valve 33 is energized and works in the right position, and the hydraulic oil in the accumulator 1 6 enters the parking brake 4 through the one-way valve 3 39, the two-position three-way solenoid valve 33, and the brake oil port P3 to release the parking brake;

[0062] A low-pressure alarm switch 5 is also connected to the oil outlet end of the brake oil port P3. The low-pressure alarm switch 5 detects the pressure value F1 of the hydraulic oil entering the parking brake 4. When the pressure value F1 is lower than the pressure F0 required for releasing the parking brake 4, the low-pressure alarm switch 5 alarms, that is, the alarm light comes on, indicating that the pressure of the hydraulic oil is low and the vehicle needs to be stopped for maintenance.

[0063] S6. When the parking brake switch is pressed, the two-position three-way solenoid valve 33 loses power and works in the left position. The hydraulic oil in the accumulator 6 enters the drive axle 10 through the one-way valve 39, the two-position three-way solenoid valve 33, and the cooling oil port D to cool it; when the hydraulic oil pressure is too high, the one-way valve 37 will be opened and return to the oil tank. Here, the one-way valve 37 can be set as a pressure limiting valve. When a certain pressure is reached, the oil circuit can be opened.

[0064] When the low-pressure alarm switch 5 detects that the pressure value F1 of the hydraulic oil entering the parking brake 4 is lower than the pressure F0 required for releasing the parking brake 4, the low-pressure alarm switch 5 lights up to alarm, and the parking brake of the electric forklift is locked.

[0065] S7, operate the pilot handle 12, first detect the position of the driver, wherein the switch of the OPS solenoid valve 36 is installed under the seat of the cab, when the driver is in the normal working position, the switch of the OPS solenoid valve 36 is turned on and energized, and the hydraulic oil derived from the hydraulic pump 2 is sequentially introduced into the pilot handle 12 through the oil inlet P0, the throttle valve 1 311, the check valve 2 38, the pressure reducing valve 35, and the OPS solenoid valve 36 for pilot action;

[0066] When the driver is not in the normal working position, the OPS solenoid valve 36 loses power, and the hydraulic oil flows back to the oil tank 1 from the oil return port 1 T1 through the oil inlet P0, throttle valve 1 311, check valve 2 38, pressure reducing valve 35, and OPS solenoid valve 36 in sequence. That is, the oil supply line of the pilot handle 12 is cut off, and the forklift does not move when the pilot handle 12 is operated.

[0067] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application are within the scope of protection of the pending claims of the present application.

Claims

1. A hydraulic integrated valve block, comprising a valve body, characterized in that: The valve body is provided with an oil inlet P0, an oil return port 1 T1 and an oil return port 2 T2; the valve body is also provided with a cooling oil port D connected to a drive axle (10), a pilot oil port P1 connected to a pilot handle (12), an energy storage oil port P2 connected to an accumulator 1 (6), a brake oil port P3 connected to a parking brake (4), and a detection oil port M connected to a pressure sensor (9); The oil inlet P0 is respectively connected to the pilot oil port P1, the energy storage oil port P2, the brake oil port P3, the cooling oil port D, and the detection oil port M; an OPS solenoid valve (36) is connected between the oil inlet P0 and the pilot oil port P1; a relief valve (34) is connected between the oil inlet P0 and the energy storage oil port P2; a logic valve (32) is connected between the oil inlet P0 and the cooling oil port D; and the relief valve (34) and the logic valve (32) are connected via an oil circuit; the oil inlet end of the brake oil port P3 is connected to the energy storage oil port P2 via a two-position three-way solenoid valve (33).

2. The hydraulic integrated valve block according to claim 1, characterized in that: The oil inlet P0 is connected to the energy storage oil port P2 in turn through the oil outlet end of the second check valve (38), and the oil outlet end of the second check valve (38) is connected to the OPS solenoid valve (36) through the pressure reducing valve (35).

3. The hydraulic integrated valve block according to claim 2, characterized in that: The oil outlet end of the OPS solenoid valve (36) is connected to the pilot oil port P1 through a one-way valve four (310), and the oil return end is connected to the oil return port one T1.

4. The hydraulic integrated valve block according to claim 1, characterized in that: A throttle valve 2 (312) and a check valve 3 (39) are connected in sequence between the two-position three-way solenoid valve (33) and the energy storage oil port P2; the oil return port of the two-position three-way solenoid valve (33) is connected to the oil return port 2 T2 via a check valve 1 (37); The oil outlet end of the oil inlet P0 is connected to a relief valve (31), and the oil outlet end of the relief valve (31) is connected to the second oil return port T2.

5. A hydraulic brake system for an electric forklift, comprising the hydraulic integrated valve block (3) according to any one of claims 1 to 4, characterized in that: The oil outlet end of the energy storage oil port P2 is also connected to a foot brake valve (11) and a power cut-off switch (7); the foot brake valve (11) is connected to the service brake, and the power cut-off switch (7) is connected to a transmission signal.

6. The hydraulic brake system of an electric forklift according to claim 5, characterized in that: The oil outlet end of the brake oil port P3 is also connected to a low-pressure alarm switch (5) for detecting the oil pressure of the hydraulic oil entering the parking brake (4) through the brake oil port P3.

7. The hydraulic brake system of an electric forklift according to claim 5, characterized in that: The oil outlet end of the pilot oil port P1 is also connected to an accumulator 2 (8) for supplying hydraulic oil to the forklift mast.

8. The hydraulic brake system of an electric forklift according to claim 5, characterized in that: The oil inlet P0 is connected to the oil tank (1) via a hydraulic pump (2), and the hydraulic pump (2) is electrically connected to a pump motor for driving; the oil return port 1 T1 and the oil return port 2 T2 are both connected to the oil tank (1).

9. A hydraulic braking method for an electric forklift, comprising the hydraulic braking system according to any one of claims 5 to 8, characterized in that: The following steps are involved: S1. After starting, the hydraulic pump (2) introduces hydraulic oil into the hydraulic integrated valve block (3); at the same time, the oil pressure V0 of the accumulator 1 (6) is detected. When the oil pressure V0 is lower than the lower limit value V1 of the filling of the accumulator 1 (6), the hydraulic pump (2) always fills the accumulator 1 (6); S2, when the oil pressure V0 reaches the upper limit value V2 of the filling of the accumulator 1 (6), the unloading valve (34) opens, the hydraulic oil pushes the valve core of the logic valve (32) through the unloading valve (34) and connects to the oil circuit of the cooling oil port D, and the hydraulic pump (2) guides the hydraulic oil through the logic valve (32) into the drive axle (10) to cool it; S3, when the oil pressure V0 is between V1 and V2, the unloading valve (34) and the logic valve (32) are closed, and the hydraulic oil discharged from the hydraulic pump (2) continues to fill the accumulator 1 (6); S4, the brake pedal is depressed, the foot brake valve (11) opens, and the hydraulic oil in the accumulator 1 (6) is introduced into the service brake through the foot brake valve (11) to release the service brake; S5, pull up the parking brake switch, the two-position three-way solenoid valve (33) is energized and works in the right position, and the hydraulic oil in the accumulator 1 (6) enters the parking brake (4) through the two-position three-way solenoid valve (33) to release the parking brake; S6, when the parking brake switch is pressed, the two-position three-way solenoid valve (33) loses power and works in the left position, and the hydraulic oil in the accumulator 1 (6) enters the drive axle (10) through the two-position three-way solenoid valve (33) to cool it; S7, operate the pilot handle (12), the hydraulic oil discharged from the hydraulic pump is introduced into the pilot handle (12) through the OPS solenoid valve (36) for pilot action.

10. The braking method according to claim 9, characterized in that: In step S4, the power cut-off switch (7) detects the oil pressure E1 of the accumulator 1 (6) and the foot brake valve (11) through the pressure sensor. When the oil pressure E1 is lower than the pressure value E0 required by the service brake, the power cut-off switch (7) is activated to cut off the power output of the gearbox.

11. The braking method according to claim 9, characterized in that: In steps S5 and S6, the low pressure alarm switch (5) detects the pressure value F1 of the hydraulic oil entering the parking brake (4). When the pressure value F1 is lower than the pressure F0 required for releasing the parking brake (4), the low pressure alarm switch (5) alarms.

12. The braking method according to claim 9, characterized in that: In step S7, the switch of the OPS solenoid valve (36) is installed under the seat of the cab. When the driver is in the normal working position, the switch of the OPS solenoid valve (36) is turned on and energized, and the hydraulic oil discharged from the hydraulic pump (2) enters the pilot handle (12) through the OPS solenoid valve (36) for pilot action; when the driver is not in the normal working position, the OPS solenoid valve (36) loses power, and the hydraulic oil flows back to the oil tank (1) through the oil return port T1, and the oil supply path of the pilot handle (12) is cut off. When the pilot handle (12) is operated, the forklift does not move.

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