A proportional hydraulic control system for a hydraulic transmission gearbox of a fork lift truck

Abstract

The present application belongs to the technical field of control of hydraulic transmission gearbox, and particularly relates to a proportional hydraulic control system of a hydraulic transmission gearbox for a forklift. The proportional hydraulic control system comprises an oil supply pump, a main pressure regulating valve, a relief valve, a hydraulic torque converter, a cooler, a gear shifting electromagnetic valve, a micro-motion valve, a gear control directional valve, a forward gear proportional valve, a reverse gear proportional valve, a forward I-gear clutch, a forward II-gear clutch, a reverse I-gear clutch and a reverse II-gear clutch. The gear shifting electromagnetic valve adjusts the working position of the gear control directional valve, and the opening degree of the forward gear proportional valve and the reverse gear proportional valve is adjusted, so that the proportional hydraulic control system realizes the adjustment of the neutral gear, the forward 1-gear, the forward 2-gear, the reverse 1-gear and the reverse 2-gear of the vehicle. Meanwhile, the working position of the micro-motion valve is adjusted through the micro-motion pedal, so that the micro-motion operation of the vehicle is realized. Therefore, the present application can realize the smooth control of the combination and reversing of the four clutches by using only two proportional valves and one electromagnetic valve.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic transmission gearbox control technology, and particularly relates to a proportional hydraulic control system for a forklift hydraulic transmission gearbox. Background Technology

[0002] Currently, most hydraulic transmission gearboxes used in 5-10 ton internal combustion forklifts in the domestic forklift industry are configured with 2 forward gears and 2 reverse gears. They employ a hydraulic control system that uses a combination of electromagnetic directional valves and buffer valves to control the shifting process. In this type of control system, the clutch engagement process of the gearbox is fixed, resulting in a large impact during gear shifting.

[0003] Patent 2014205263865 proposes a proportional hydraulic control system for a forklift hydraulic transmission. By using proportional valves and solenoid valves, it can achieve smooth and shock-free gear shifting operations, but it is suitable for small-tonnage forklifts that can shift forward one gear and reverse one gear.

[0004] Patent 202111628101X proposes a hydraulic transmission system controlled by electro-hydraulic proportional valves, using two electro-hydraulic proportional valves to control the engagement of the forward and reverse clutches respectively, achieving smooth shifting and micro-motion functions. However, a hydraulic control system suitable for multi-gear hydraulic transmission gearboxes of 5-10 tons is still lacking. Summary of the Invention

[0005] To address the problems in the background art, the present invention provides a proportional hydraulic control system for a hydraulic transmission gearbox for forklifts, which can be applied to 5-10 ton forklifts and meet the control requirements of 2 forward gears and 2 reverse gears.

[0006] The specific technical solution of the present invention is as follows:

[0007] A proportional hydraulic control system for a forklift hydraulic transmission includes an oil supply pump 2, a main pressure regulating valve 3, an overflow valve 4, a hydraulic torque converter 6, a cooler 5, a shift solenoid valve 7, a micro valve 8, a gear position control directional valve 11, a forward gear proportional valve 9, a reverse gear proportional valve 10, a forward I gear clutch 12, a forward II gear clutch 13, a reverse I gear clutch 14, and a reverse II gear clutch 15.

[0008] The oil inlet of the oil supply pump 2 is equipped with a filter 1, and the oil outlet of the oil supply pump 2 is connected to oil outlet pipelines I, II, III and IV respectively. The oil outlet pipeline II is equipped with a throttling orifice plate, making the oil outlet pipeline II a damping pipeline.

[0009] The oil outlet pipeline III is sequentially equipped with a main pressure regulating valve 3, an overflow valve 4, a hydraulic torque converter 6, and a cooler 5;

[0010] The oil outlet pipeline IV is sequentially equipped with a shift solenoid valve 7 and a gear position control directional valve 11. The oil inlet of the shift solenoid valve 7 is connected to the oil outlet of the oil supply pump 2, and the oil outlet of the shift solenoid valve 7 is connected to the pilot control port of the gear position control directional valve 11.

[0011] The shift solenoid valve 7 controls the gear position and the working position of the directional valve 11.

[0012] When the gear position control directional valve 11 is in the right position, the oil outlets of the forward I gear clutch 12 and the forward gear proportional valve 9 are connected through the gear position control directional valve 11, and the oil outlets of the reverse I gear clutch 14 and the reverse gear proportional valve 10 are connected through the gear position control directional valve 11.

[0013] The forward second gear clutch 13 and the reverse second gear clutch 15 are respectively connected to the oil return port through the gear control directional valve 11;

[0014] When the gear position control directional valve 11 is in the left position, the oil outlets of the forward second gear clutch 13 and the forward gear proportional valve 9 are connected through the gear position control directional valve 11, and the oil outlets of the reverse second gear clutch 15 and the reverse gear proportional valve 10 are connected through the gear position control directional valve 11.

[0015] The forward first gear clutch 12 and the reverse first gear clutch 14 are respectively connected to the oil return port through the gear control directional valve 11;

[0016] The oil inlets of the forward gear proportional valve 9 and the reverse gear proportional valve 10 are respectively connected to the oil outlet pipe of the micro valve 8.

[0017] Oil outlet line I and oil outlet line II are respectively connected to the first oil inlet and the second oil inlet of micro valve 8.

[0018] The micro-motion pedal controls the working position of the micro-motion valve 8 via a micro-motion cable.

[0019] When the micro valve 8 is in the left position, the first oil inlet and the second oil inlet of the micro valve 8 are connected to the oil outlet, respectively.

[0020] When the micro valve 8 is in the neutral position, the first oil inlet of the micro valve 8 is cut off, the second oil inlet and the oil outlet are connected, and the oil outlet and the oil return are connected.

[0021] When the micro valve 8 is in the right position, both the first and second oil inlets of the micro valve 8 are closed, while the oil outlet and return port are open.

[0022] When the system is working, the switching solenoid valve 7 is energized or de-energized to adjust the working position of the gear control directional valve 11, and the current of the forward gear proportional valve 9 and the reverse gear proportional valve 10 is adjusted to regulate the oil outlet pressure of the forward gear proportional valve 9 and the reverse gear proportional valve 10. This enables the above-mentioned proportional hydraulic control system to control the vehicle in neutral, forward 1st gear, forward 2nd gear, reverse 1st gear, and reverse 2nd gear. At the same time, the working position of the micro valve 8 is adjusted by the micro pedal to achieve micro-motion control of the vehicle.

[0023] Furthermore, when the vehicle is in neutral, the shift solenoid valve 7, forward gear proportional valve 9 and reverse gear proportional valve 10 are de-energized, the gear position control directional valve 11 is in the right position, the micro valve 8 is in the left position, and no pressurized oil enters the forward I gear clutch 12, forward II gear clutch 13, reverse I gear clutch 14 and reverse II gear clutch 15.

[0024] When the vehicle is in first gear, the shift solenoid valve 7 is de-energized, the forward gear proportional valve 9 is energized, the reverse gear proportional valve 10 is de-energized, the gear position control directional valve 11 is in the right position, the micro valve 8 is in the left position, and the pressurized oil enters the forward gear proportional valve 9 through the oil outlet line I and oil outlet line II via the micro valve 8, and finally enters the forward first gear clutch 12 through the gear position control directional valve 11, i.e., the forward first gear clutch 12 is engaged.

[0025] When the vehicle is in forward 2nd gear, the shift solenoid valve 7 is energized, the forward gear proportional valve 9 is energized, the reverse gear proportional valve 10 is de-energized, the gear control directional valve 11 is in the left position, the micro valve 8 is in the left position, the pressurized oil enters the forward gear proportional valve 9 through the oil outlet line I and oil outlet line II via the micro valve 8, and finally enters the forward 2nd gear clutch 13 through the gear control directional valve 11, that is, the forward 2nd gear clutch 13 is engaged.

[0026] When the vehicle is in reverse 1st gear, the shift solenoid valve 7 is de-energized, the forward gear proportional valve 9 is de-energized, and the reverse gear proportional valve 10 is energized. The gear control directional valve 11 is in the right position, and the micro valve 8 is in the left position. The pressurized oil enters the reverse gear proportional valve 10 through the oil outlet line I and oil outlet line II via the micro valve 8, and finally enters the reverse 1st gear clutch 14 through the gear control directional valve 11, i.e., the reverse 1st gear clutch 14 is engaged.

[0027] When the vehicle is in reverse 2nd gear, the shift solenoid valve 7 is energized, the forward gear proportional valve 9 is de-energized, and the reverse gear proportional valve 10 is energized. The gear control directional valve 11 is in the left position, the micro valve 8 is in the left position, and the pressurized oil enters the reverse gear proportional valve 10 through the oil outlet line I and oil outlet line II via the micro valve 8. Finally, it enters the reverse 2nd gear clutch 15 through the gear control directional valve 11, i.e., the reverse 2nd gear clutch 15 is engaged.

[0028] When the vehicle is in forward 1st gear, forward 2nd gear, reverse 1st gear, or reverse 2nd gear, the micro-motion valve 8 is in the neutral position, and the vehicle is in a micro-motion state.

[0029] When the vehicle is in forward 1st gear, forward 2nd gear, reverse 1st gear, or reverse 2nd gear, and the micro-adjustment valve 8 is in the right position, the vehicle is in disengaged gear.

[0030] Furthermore, the shift solenoid valve 7 is a two-position three-way solenoid valve. When the shift solenoid valve 7 is de-energized, the pilot control port and the return port of the gear position control directional valve 11 are connected, and the valve core of the gear position control directional valve 11 is in the right position under the action of the spring.

[0031] When the shift solenoid valve 7 is energized, the pilot control port of the gear position control directional valve 11 is connected to the oil outlet of the oil supply pump 2. The pump outlet pressure oil enters the pilot control port of the gear position control directional valve 11 through the shift solenoid valve 7. The pump outlet pressure oil pushes the valve core of the gear position control directional valve 11 to move to the right against the spring force, and the gear position control directional valve 11 is in the left position.

[0032] Furthermore, the micro valve 8 includes a first oil inlet, a second oil inlet, an oil outlet, and a return oil outlet. The first oil inlet and the second oil inlet are respectively connected to the oil outlet pipeline I and the oil outlet pipeline II, and the oil outlet is respectively connected to the oil inlet pipelines of the forward gear proportional valve 9 and the reverse gear proportional valve 10.

[0033] The valve core of the micro valve 8 is connected to the micro pedal via a cable.

[0034] When the micro pedal is pressed, the cable moves the valve core. When the micro valve 8 is in the micro state, i.e., the intermediate working position, the connection between the first oil inlet and the oil outlet is cut off, and at the same time the connection between the second oil inlet and the oil return is established. As the valve core moves, the opening of the second oil inlet and the oil return gradually increases, so that the pressure at the oil outlet gradually decreases, the corresponding clutch engagement pressure decreases, and the clutch is in the micro state.

[0035] Furthermore, the forward gear proportional valve 9 and the reverse gear proportional valve 10 are electro-proportional pressure reducing valves, and the outlet pressure of the electro-proportional pressure reducing valves can be controlled by controlling the current.

[0036] Furthermore, the orifice diameter of the orifice plate 16 is 1.0~1.6mm.

[0037] Beneficial technical effects of the present invention:

[0038] (1) A proportional hydraulic control system for a forklift hydraulic transmission gearbox of the present invention includes an oil supply pump, a main pressure regulating valve, an overflow valve, a hydraulic torque converter, a cooler, a shift solenoid valve, a micro valve, a gear control directional valve, a forward gear proportional valve, a reverse gear proportional valve, a forward I gear clutch, a forward II gear clutch, a reverse I gear clutch, and a reverse II gear clutch; when the system is working, the on / off state of the shift solenoid valve is controlled to adjust the working position of the gear control directional valve, and the current of the forward gear proportional valve and the reverse gear proportional valve is adjusted to adjust the opening of the forward gear proportional valve and the reverse gear proportional valve, so that the above-mentioned proportional hydraulic control system can realize the vehicle's neutral, forward I gear, forward II gear, reverse I gear, and reverse II gear adjustment; at the same time, the working position of the micro valve is adjusted by the micro pedal to realize the vehicle's micro operation;

[0039] Therefore, by setting up a shift solenoid valve and a gear control directional valve, this invention can achieve smooth control of the engagement and reversal of four clutch gears using only the application of forward gear proportional valves and reverse gear proportional valves, while conventional solutions require four proportional valves for control. This solution is also more cost-effective.

[0040] (2) The present invention retains the lower cost mechanical micro-motion structure, namely the micro-motion valve. The micro-motion valve is equipped with a dual oil inlet circuit. The oil outlet line II and the oil outlet line I are respectively connected to the oil inlet of the micro-motion valve. When micro-motion is not performed, the two oil lines supply oil to the clutch control circuit at the same time, thereby improving the response speed of clutch engagement. When micro-motion is performed, the oil line I without damping throttling is cut off first. The unloading circuit of the micro-motion valve passes through the throttling orifice of the throttling orifice plate on the oil line II, thereby reducing the unloading flow during micro-motion. At the same time, it ensures that the working pressure of the shift solenoid valve will not drop too much, thus avoiding unexpected downshifting when shifting forward 2 gears or backward 2 gears. Attached Figure Description

[0041] Figure 1 This is a system diagram of a proportional hydraulic control system for a hydraulic transmission gearbox for forklifts according to the present invention.

[0042] Figure 2 This is a diagram showing the forward first gear operation of a proportional hydraulic control system for a forklift hydraulic transmission gearbox according to the present invention.

[0043] Figure 3 This is a diagram showing the forward 2nd gear usage state of a proportional hydraulic control system for a forklift hydraulic transmission gearbox according to the present invention.

[0044] Figure 4 This is a micro-motion state diagram of the forward 2nd gear of a proportional hydraulic control system for a hydraulic transmission gearbox for forklifts according to the present invention.

[0045] Figure 5 This is a schematic diagram of the micro valve of the present invention.

[0046] The components include: filter 1, oil supply pump 2, main pressure regulating valve 3, overflow valve 4, hydraulic torque converter 6, cooler 5, shift solenoid valve 7, micro valve 8, forward gear proportional valve 9, reverse gear proportional valve 10, gear position control directional valve 11, forward gear I clutch 12, forward gear II clutch 13, reverse gear I clutch 14, and reverse gear II clutch 15. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Example

[0048] See Figure 1 A proportional hydraulic control system for a forklift hydraulic transmission gearbox includes an oil supply pump 2, a main pressure regulating valve 3, an overflow valve 4, a hydraulic torque converter 6, a cooler 5, a shift solenoid valve 7, a micro valve 8, a gear position control directional valve 11, a forward gear proportional valve 9, a reverse gear proportional valve 10, a forward I gear clutch 12, a forward II gear clutch 13, a reverse I gear clutch 14, and a reverse II gear clutch 15.

[0049] The oil inlet of the oil supply pump 2 is equipped with a filter 1, and the oil outlet of the oil supply pump 2 is connected to oil outlet pipelines I, II, III and IV respectively. The oil outlet pipeline II is equipped with a throttling orifice plate, making the oil outlet pipeline II a damping pipeline.

[0050] The oil outlet pipeline III is sequentially equipped with a main pressure regulating valve 3, an overflow valve 4, a hydraulic torque converter 6, and a cooler 5;

[0051] The oil outlet pipeline IV is sequentially equipped with a shift solenoid valve 7 and a gear control directional valve 11. The oil inlet of the shift solenoid valve 7 is connected to the oil outlet pipeline of the oil supply pump 2, and the oil outlet of the shift solenoid valve 7 is connected to the pilot control port of the gear control directional valve 11.

[0052] The shift solenoid valve 7 controls the gear position and the working position of the directional valve 11.

[0053] When the gear position control directional valve 11 is in the right position, the oil outlets of the forward I gear clutch 12 and the forward gear proportional valve 9 are connected through the gear position control directional valve 11, and the oil outlets of the reverse I gear clutch 14 and the reverse gear proportional valve 10 are connected through the gear position control directional valve 11.

[0054] The forward second gear clutch 13 and the reverse second gear clutch 15 are respectively connected to the oil return port;

[0055] When the gear position control directional valve 11 is in the left position, the oil outlets of the forward second gear clutch 13 and the forward gear proportional valve 9 are connected through the gear position control directional valve 11, and the oil outlets of the reverse second gear clutch 15 and the reverse gear proportional valve 10 are connected through the gear position control directional valve 11.

[0056] The forward first gear clutch 12 and the reverse first gear clutch 14 are respectively connected to the oil return port pipe;

[0057] The oil inlets of the forward gear proportional valve 9 and the reverse gear proportional valve 10 are respectively connected to the oil outlet pipe of the micro valve 8.

[0058] Oil outlet line I and oil outlet line II are respectively connected to the first oil inlet and the second oil inlet of micro valve 8.

[0059] The micro-motion pedal controls the working position of the micro-motion valve 8.

[0060] When the micro valve 8 is in the left position, the first oil inlet and the second oil inlet of the micro valve 8 are connected to the oil outlet, respectively.

[0061] When the micro valve 8 is in the neutral position, the first oil inlet of the micro valve 8 is cut off, the second oil inlet and the oil outlet are connected, and the oil outlet and the oil return are connected.

[0062] When the micro valve 8 is in the right position, both the first and second oil inlets of the micro valve 8 are closed, while the oil outlet and return port are open.

[0063] When the system is working, the switching solenoid valve 7 is energized or de-energized to adjust the working position of the gear control directional valve 11, and the current of the forward gear proportional valve 9 and the reverse gear proportional valve 10 is adjusted to regulate the oil outlet pressure of the forward gear proportional valve 9 and the reverse gear proportional valve 10. This enables the above-mentioned proportional hydraulic control system to control the vehicle in neutral, forward 1st gear, forward 2nd gear, reverse 1st gear, and reverse 2nd gear. At the same time, the working position of the micro valve 8 is adjusted by the micro pedal to achieve micro-motion control of the vehicle.

[0064] When the vehicle is in neutral, the shift solenoid valve 7, forward gear proportional valve 9 and reverse gear proportional valve 10 are de-energized, the gear position control directional valve 11 is in the right position, the micro valve 8 is in the left position, and no pressurized oil enters the forward I gear clutch 12, forward II gear clutch 13, reverse I gear clutch 14 and reverse II gear clutch 15.

[0065] When the vehicle is in first gear, the shift solenoid valve 7 is de-energized, the forward gear proportional valve 9 is energized, the reverse gear proportional valve 10 is de-energized, the gear position control directional valve 11 is in the right position, the micro valve 8 is in the left position, and the pressurized oil enters the forward gear proportional valve 9 through the oil outlet line I and oil outlet line II via the micro valve 8, and finally enters the forward first gear clutch 12 through the gear position control directional valve 11, i.e., the forward first gear clutch 12 is engaged.

[0066] When the vehicle is in forward 2nd gear, the shift solenoid valve 7 is energized, the forward gear proportional valve 9 is energized, the reverse gear proportional valve 10 is de-energized, the gear control directional valve 11 is in the left position, the micro valve 8 is in the left position, the pressurized oil enters the forward gear proportional valve 9 through the oil outlet line I and oil outlet line II via the micro valve 8, and finally enters the forward 2nd gear clutch 13 through the gear control directional valve 11, that is, the forward 2nd gear clutch 13 is engaged.

[0067] When the vehicle is in reverse 1st gear, the shift solenoid valve 7 is de-energized, the forward gear proportional valve 9 is de-energized, and the reverse gear proportional valve 10 is energized. The gear control directional valve 11 is in the right position, and the micro valve 8 is in the left position. The pressurized oil enters the reverse gear proportional valve 10 through the oil outlet line I and oil outlet line II via the micro valve 8, and finally enters the reverse 1st gear clutch 14 through the gear control directional valve 11, i.e., the reverse 1st gear clutch 14 is engaged.

[0068] When the vehicle is in reverse 2nd gear, the shift solenoid valve 7 is energized, the forward gear proportional valve 9 is de-energized, and the reverse gear proportional valve 10 is energized. The gear control directional valve 11 is in the left position, the micro valve 8 is in the left position, and the pressurized oil enters the reverse gear proportional valve 10 through the oil outlet line I and oil outlet line II via the micro valve 8. Finally, it enters the reverse 2nd gear clutch 15 through the gear control directional valve 11, i.e., the reverse 2nd gear clutch 15 is engaged.

[0069] When the vehicle is in forward 1st gear, forward 2nd gear, reverse 1st gear, or reverse 2nd gear, the micro-motion valve 8 is in the neutral position, and the vehicle is in a micro-motion state.

[0070] The shift solenoid valve 7 is a two-position three-way solenoid valve. When the shift solenoid valve 7 is de-energized, the pilot control port and the return port of the gear position control directional valve 11 are connected, and the valve core of the gear position control directional valve 11 is in the right position under the action of the spring.

[0071] When the shift solenoid valve 7 is energized, the pilot control port of the gear position control directional valve 11 is connected to the oil outlet of the oil supply pump 2. The pump outlet pressure oil enters the pilot control port of the gear position control directional valve 11 through the shift solenoid valve 7. The pump outlet pressure oil pushes the valve core of the gear position control directional valve 11 to move to the right against the spring force, and the gear position control directional valve 11 is in the left position.

[0072] The micro valve 8 includes a first oil inlet, a second oil inlet, an oil outlet, and a return oil outlet. The first oil inlet and the second oil inlet are respectively connected to the oil outlet pipeline I and the oil outlet pipeline II, and the oil outlet is respectively connected to the oil inlet pipelines of the forward gear proportional valve 9 and the reverse gear proportional valve 10.

[0073] The valve core of the micro valve 8 is connected to the micro pedal via a cable.

[0074] When the micro pedal is pressed, the cable moves the valve core. When the micro valve 8 is in the micro state, i.e., the intermediate working position, the connection between the first oil inlet and the oil outlet is cut off, and at the same time the connection between the second oil inlet and the oil return is established. As the valve core moves, the opening of the second oil inlet and the oil return gradually increases, so that the pressure at the oil outlet gradually decreases, the corresponding clutch engagement pressure decreases, and the clutch is in the micro state.

[0075] The forward gear proportional valve 9 and the reverse gear proportional valve 10 are electro-proportional pressure reducing valves. By controlling the current, the outlet pressure of the electro-proportional pressure reducing valve is controlled.

[0076] The orifice diameter of the orifice plate 16 is 1.0~1.6mm.

[0077] Specifically, forward gear 12 is represented as F1, forward gear 2 clutch 13 as F2, reverse gear 14 as R1, and reverse gear 2 clutch 15 as R2.

[0078] See Figure 1 In neutral, the transmission TCU does not send electrical signals to the shift solenoid valve 7, forward gear proportional valve 9, and reverse gear proportional valve 10. The shift solenoid valve 7, forward gear proportional valve 9, and reverse gear proportional valve 10 are all in an initial state without power. At this time, the gear position control directional valve 11 is in the right position. At this time, F2 and R2 are connected to the oil return port through the gear position control directional valve 11, while the oil outlets of the forward gear proportional valve 9 and the reverse gear proportional valve 10 are connected to the oil return port respectively. Therefore, F1 and R1 are connected to the oil return port through the forward gear proportional valve 9 and the reverse gear proportional valve 10. No pressurized oil enters all clutches, F2, R2, F1, and R1 are in a disengaged state, and the vehicle is in neutral.

[0079] See Figure 2 As shown, when in first gear, the transmission TCU controls the shift solenoid valve 7 to be de-energized, the forward gear proportional valve 9 to be energized, and the reverse gear proportional valve 10 to be de-energized. The pump pressure oil from the oil supply pump 2 is connected to the micro valve 8 via the oil outlet line I and the micro valve 8 via the oil outlet line II. Then, it enters the forward clutch F1 via the forward gear proportional valve 9 and the gear position control directional valve 11, controlling F1 to engage. F2 and R2 are both connected to the return oil port through the gear position control directional valve 11 and are in a depressurized and disengaged state. R1 is connected to the return oil port through the reverse gear proportional valve 10 and is in a depressurized and disengaged state. The vehicle is driving in first gear.

[0080] like Figure 3As shown, when the vehicle shifts from forward 1st gear to forward 2nd gear, the current of the forward gear proportional valve 9 controlled by the transmission TCU decreases rapidly, the oil outlet pressure of the forward gear proportional valve 9 decreases rapidly, and at the same time, the shift solenoid valve 7 is energized. The pump pressure oil of the oil supply pump 2 enters the control chamber of the gear position control directional valve 11 through the shift solenoid valve 7, pushing the valve core to move, and the gear position control directional valve 11 is in the left position.

[0081] When the control current of the forward gear proportional valve 9 decreases to a low value, the forward gear proportional valve 9 is controlled to increase the current according to the preset engagement curve. At this time, the pressurized oil goes through the oil outlet line I and the oil outlet line II to the micro valve 8, and then through the forward gear proportional valve 9 and the gear position control directional valve 11 to enter F2, controlling F2 to engage. F1 and R1 are both connected to the oil return port through the gear position control directional valve 11 and are in a depressurized and disengaged state. R2 is connected to the oil return port through the reverse gear proportional valve 10 and is in a depressurized and disengaged state. The vehicle moves from forward 1st gear to forward 2nd gear.

[0082] When the vehicle shifts from 2nd gear to 1st gear, the current of the forward gear proportional valve 9 controlled by the transmission TCU decreases rapidly, the outlet pressure of the pressure reducing valve of the forward gear proportional valve 9 decreases rapidly, and at the same time, the shift solenoid valve 7 is de-energized. The pressure oil in the control chamber of the gear position control directional valve 11 is connected to the return port through the shift solenoid valve 7. The valve core moves to the left under the action of the spring, and the gear position control directional valve 11 is in the right position.

[0083] When the control current of the forward gear proportional valve 9 decreases to a low value, the forward gear proportional valve 9 is controlled to increase the current according to the preset engagement curve. At this time, the pressurized oil goes through the oil outlet line I and the oil outlet line II to the micro valve 8, and then through the forward gear proportional valve 9 and the gear position control directional valve 11 to enter F1, controlling F1 to engage. F2 and R2 are both connected to the oil return port through the gear position control directional valve 11 and are in a depressurized and disengaged state. R1 is connected to the oil return port through the reverse gear proportional valve 10 and is in a depressurized and disengaged state. The vehicle is driven from forward 2nd gear to forward 1st gear.

[0084] When the vehicle returns from first gear to neutral, the current of the forward gear proportional valve 9 controlled by the transmission TCU decreases rapidly to 0, and the outlet pressure of the pressure reducing valve of the forward gear proportional valve 9 decreases rapidly until the current of the forward gear proportional valve 9 is 0. At this point, the oil outlet and return port of the forward gear proportional valve 9 are connected, F1 is disengaged, and the vehicle is in neutral.

[0085] When the vehicle shifts from 2nd gear to neutral, the current of the forward gear proportional valve 9 controlled by the transmission TCU rapidly decreases to 0, and the outlet pressure of the pressure reducing valve of the forward gear proportional valve 9 rapidly decreases until the current of the forward gear proportional valve 9 is 0. At this point, the oil outlet and return port of the forward gear proportional valve 9 are connected, F2 is disengaged, and the vehicle is in neutral. When the transmission TCU detects that the current of the proportional valve is 0, it controls the shift solenoid valve 7 to be de-energized, and the gear position control directional valve 11 switches from the left position to the right position under the action of the spring.

[0086] The gear control process for reverse gear is the same as that for forward gear, so it will not be described in detail.

[0087] like Figure 4 As shown, when the vehicle is in forward 2nd gear and the micro-adjustment valve 8 is in the neutral position, the vehicle is in a forward 2nd gear micro-adjustment state. When the vehicle is in forward 1st gear, reverse 1st gear, or reverse 2nd gear and the micro-adjustment valve 8 is in the neutral position, the vehicle is in the corresponding micro-adjustment state.

[0088] See Figure 5 When performing micro-motion operation, the micro-motion pedal is pressed, and the valve core of the micro-motion valve 8 is moved by the cable mechanism of the micro-motion pedal. The valve core of the micro-motion valve 8 moves to the right as shown in the figure. The first oil inlet P1 gradually closes, that is, the oil outlet I is closed. At the same time, the second oil inlet P2 and the return oil outlet T1 gradually open, that is, the oil outlet II is connected to the return oil outlet of the micro-motion valve 8. At this time, the pump pressure oil from the pump port of the oil supply pump 2 enters the micro-motion valve 8 through the throttling orifice of the throttling orifice plate 16 and flows to the return oil outlet. As the valve core of the micro-motion valve 8 moves, the opening of the second oil inlet P2 and the return oil outlet T1 becomes larger and larger. The pressure at the oil outlet A of the micro-motion valve 8 gradually decreases, and the pressure drop in the clutch gradually decreases until the valve core moves to the right position, that is, the second oil inlet P2 also closes, the oil outlet A and the return oil outlet T1 are connected, the pressure drops to almost zero, the clutch is completely disengaged, and the gear is disengaged.

[0089] At this time, the orifice diameter of the orifice plate 16 is 1.0~1.6mm. Due to the effect of the throttling orifice on the orifice plate 16, the transmission pump port still maintains a certain pressure. Without the throttling orifice, the pump port pressure would also become very low, which would lead to the following problems: First, insufficient flow of oil supply and cooling oil in the torque converter 6, resulting in low system operating efficiency and severe heat generation;

[0090] Secondly, if the shift solenoid valve 7 is energized at this time, and the vehicle is in forward 2nd gear or reverse 2nd gear, the pump port pressure will decrease. If the pressure is lower than the spring force of the gear position control valve 11, the gear position control valve 11 will return to the 1st gear state under the action of the spring. During the micro-movement process, the pressure change will cause the gear to switch back and forth between the 1st and 2nd gear states, which will cause noise in the transmission and poor vehicle handling.

[0091] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A proportional hydraulic control system for a forklift hydraulic transmission gearbox, characterized in that: Includes oil supply pump (2), main pressure regulating valve (3), overflow valve (4), hydraulic torque converter (6), cooler (5), shift solenoid valve (7), micro valve (8), gear control directional valve (11), forward gear proportional valve (9), reverse gear proportional valve (10), forward gear I clutch (12), forward gear II clutch (13), reverse gear I clutch (14), and reverse gear II clutch (15); The oil inlet of the oil supply pump (2) is equipped with a filter (1), and the oil outlet of the oil supply pump (2) is connected to oil outlet pipelines I, II, III and IV respectively. The oil outlet pipeline II is equipped with a throttling orifice plate, so that the oil outlet pipeline II is a damping pipeline. The oil outlet pipeline III is sequentially equipped with a main pressure regulating valve (3), an overflow valve (4), a hydraulic torque converter (6), and a cooler (5); The oil outlet pipeline IV is provided with a shift solenoid valve (7) and a gear control directional valve (11) in sequence. The oil inlet of the shift solenoid valve (7) is connected to the oil outlet of the oil supply pump (2), and the oil outlet of the shift solenoid valve (7) is connected to the pilot control port of the gear control directional valve (11). The shift solenoid valve (7) controls the working position of the gear control directional valve (11). When the gear control directional valve (11) is in the right position, the oil outlet of the forward I gear clutch (12) and the forward gear proportional valve (9) are connected through the gear control directional valve (11), and the oil outlet of the reverse I gear clutch (14) and the reverse gear proportional valve (10) are connected through the gear control directional valve (11). The forward second gear clutch (13) and the reverse second gear clutch (15) are connected to the oil return port respectively through the gear control directional valve (11); When the gear control directional valve (11) is in the left position, the oil outlets of the forward II gear clutch (13) and the forward gear proportional valve (9) are connected through the gear control directional valve (11), and the oil outlets of the reverse II gear clutch (15) and the reverse gear proportional valve (10) are connected through the gear control directional valve (11). The forward first gear clutch (12) and the reverse first gear clutch (14) are connected to the oil return port through the gear control directional valve (11); The oil inlets of the forward gear proportional valve (9) and the reverse gear proportional valve (10) are respectively connected to the oil outlet pipe of the micro valve (8); Oil outlet line I and oil outlet line II are respectively connected to the first oil inlet and the second oil inlet of the micro valve (8). The micro-motion pedal controls the working position of the micro-motion valve (8) via the micro-motion cable. When the micro valve (8) is in the left position, the first oil inlet and the second oil inlet of the micro valve (8) are connected to the oil outlet, respectively. When the micro valve (8) is in the neutral position, the first oil inlet of the micro valve (8) is cut off, the second oil inlet and the oil outlet are connected, and the oil outlet and the oil return are connected. When the micro valve (8) is in the right position, the first oil inlet and the second oil inlet of the micro valve (8) are both closed, and the oil outlet and the oil return are connected. When the system is working, the switching solenoid valve (7) is energized or de-energized to adjust the working position of the gear control directional valve (11), and the current of the forward gear proportional valve (9) and the reverse gear proportional valve (10) is adjusted to adjust the oil outlet pressure of the forward gear proportional valve (9) and the reverse gear proportional valve (10), so that the above-mentioned proportional hydraulic control system can control the vehicle in neutral, forward 1st gear, forward 2nd gear, reverse 1st gear, and reverse 2nd gear; at the same time, the working position of the micro valve (8) is adjusted by the micro pedal to realize the micro control of the vehicle.

2. The proportional hydraulic control system for a forklift hydraulic transmission gearbox according to claim 1, characterized in that: When the vehicle is in neutral, the shift solenoid valve (7), forward gear proportional valve (9) and reverse gear proportional valve (10) are de-energized, the gear control directional valve (11) is in the right position, the micro valve (8) is in the left position, and no pressure oil enters the forward I gear clutch (12), forward II gear clutch (13), reverse I gear clutch (14) and reverse II gear clutch (15); When the vehicle is in forward first gear, the shift solenoid valve (7) is de-energized, the forward gear proportional valve (9) is energized, the reverse gear proportional valve (10) is de-energized, the gear position control directional valve (11) is in the right position, the micro valve (8) is in the left position, the pressure oil enters the forward gear proportional valve (9) through the micro valve (8) via the oil outlet line I and the oil outlet line II, and finally enters the forward first gear clutch (12) through the gear position control directional valve (11), that is, the forward first gear clutch (12) is engaged; When the vehicle is in forward 2nd gear, the shift solenoid valve (7) is energized, the forward gear proportional valve (9) is energized, and the reverse gear proportional valve (10) is de-energized. The gear position control directional valve (11) is in the left position, the micro valve (8) is in the left position, and the pressure oil enters the forward gear proportional valve (9) through the micro valve (8) via the oil outlet line I and the oil outlet line II, and finally enters the forward 2nd gear clutch (13) through the gear position control directional valve (11), that is, the forward 2nd gear clutch (13) is engaged. When the vehicle is in reverse gear 1, the shift solenoid valve (7) is de-energized, the forward gear proportional valve (9) is de-energized, and the reverse gear proportional valve (10) is energized. The gear position control directional valve (11) is in the right position, the micro valve (8) is in the left position, and the pressure oil enters the reverse gear proportional valve (10) through the oil outlet line I and oil outlet line II via the micro valve (8), and finally enters the reverse gear 1 clutch (14) through the gear position control directional valve (11), that is, the reverse gear 1 clutch (14) is engaged. When the vehicle is in reverse gear 2, the shift solenoid valve (7) is energized, the forward gear proportional valve (9) is de-energized, and the reverse gear proportional valve (10) is energized. The gear position control directional valve (11) is in the left position, the micro valve (8) is in the left position, and the pressure oil enters the reverse gear proportional valve (10) through the oil outlet line I and oil outlet line II via the micro valve (8), and finally enters the reverse gear 2 clutch (15) through the gear position control directional valve (11), that is, the reverse gear 2 clutch (15) is engaged. When the vehicle is in forward 1st gear, forward 2nd gear, reverse 1st gear or reverse 2nd gear, and the micro-motion valve (8) is in the neutral position, the vehicle is in micro-motion state; When the vehicle is in forward 1st gear, forward 2nd gear, reverse 1st gear or reverse 2nd gear, and the micro-adjustment valve (8) is in the right position, the vehicle is in disengaged state.

3. The proportional hydraulic control system for a forklift hydraulic transmission gearbox according to claim 1, characterized in that: The shift solenoid valve (7) is a two-position three-way solenoid valve. When the shift solenoid valve (7) is de-energized, the pilot control port and the return port of the gear position control directional valve (11) are connected. The valve core of the gear position control directional valve (11) is in the right position under the action of the spring. The gear position control directional valve (11) is in the right position. When the shift solenoid valve (7) is energized, the pilot control port of the gear position control directional valve (11) is connected to the oil outlet of the oil supply pump (2). The pump port pressure oil enters the pilot control port of the gear position control directional valve (11) through the shift solenoid valve (7). The pump port pressure oil pushes the valve core of the gear position control directional valve (11) to move to the right against the spring force, and the gear position control directional valve (11) is in the left position.

4. The proportional hydraulic control system for a forklift hydraulic transmission gearbox according to claim 1, characterized in that: The micro valve (8) includes a first oil inlet, a second oil inlet, an oil outlet and a return oil outlet. The first oil inlet and the second oil inlet are respectively connected to the oil outlet pipeline I and the oil outlet pipeline II. The oil outlet is respectively connected to the oil inlet pipeline of the forward gear proportional valve (9) and the reverse gear proportional valve (10). The valve core of the micro valve (8) is connected to the micro pedal via a cable. When the micro pedal is pressed, the cable drives the valve core to move. When the micro valve (8) is in the micro state, i.e. the intermediate working position, the connection between the first oil inlet and the oil outlet is cut off, and the connection between the second oil inlet and the oil return is established at the same time. As the valve core moves, the opening of the second oil inlet and the oil return gradually increases, so that the pressure at the oil outlet gradually decreases, the corresponding clutch engagement pressure decreases, and the clutch is in the micro state.

5. The proportional hydraulic control system for a forklift hydraulic transmission gearbox according to claim 1, characterized in that: The forward gear proportional valve (9) and the reverse gear proportional valve (10) are electro-proportional pressure reducing valves. By controlling the current, the outlet pressure of the electro-proportional pressure reducing valve is controlled.

6. The proportional hydraulic control system for a forklift hydraulic transmission gearbox according to claim 1, characterized in that: The orifice diameter of the orifice plate (16) is 1.0~1.6mm.

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