Hydraulic control system, gear shifting method and gearbox assembly suitable for small-tonnage forklift

Abstract

The invention discloses a hydraulic control system suitable for a small-tonnage forklift, a gear shifting method and a gearbox assembly. The system comprises a forward clutch, a backward clutch, an inching valve, a two-way buffer and an electromagnetic reversing valve. The gear shifting oil way sequentially passes through the inching valve and the electromagnetic reversing valve and then enters the forward clutch and the backward clutch. A bidirectional buffer is connected in series to an oil path entering the forward clutch and the backward clutch; the bidirectional buffer comprises a cavity, an elastic piece, a first piston and a second piston, wherein the elastic piece, the first piston and the second piston are located in the cavity. The first piston and the second piston are fixedly connected with the two ends of the elastic piece correspondingly and divide the cavity into an advancing cavity and a retreating cavity. The elastic piece is matched with the first piston and the second piston, so that the first piston and the second piston can slide in the cavity, and power crossing in the gear switching process can be reduced, so that more gentle gear shifting is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic transmissions for forklifts, and in particular to a hydraulic control system, a shifting method and a transmission assembly suitable for small-tonnage forklifts. Background Art

[0002] The usage scenarios determine that forklifts need to perform frequent gear shifting and reversing operations during actual work. The smoothness and softness of gear shifting are very important for driving performance. The forklift achieves gear engagement or disengagement through the engagement and separation of the clutch master and slave friction plates to transmit gear torque and switch gears. The return of the gearbox clutch piston is achieved by the preload force of the clutch internal spring. At the moment of engaging the gear, the gear clutch has an impact due to the excessive main oil pressure, which quickly overcomes the clutch spring preload force and causes the master and slave friction plates to engage quickly. In addition, due to the characteristics of the electromagnetic switch valve used in the gearbox shifting and the gaps between gears, main reducers, bevel gears, etc., rapid oil filling will not only cause driving setbacks, but also cause additional impact and wear on the vehicle's transmission system, affecting the vehicle's performance, reliability and service life.

[0003] In the prior art, the invention patent with the patent publication number CN118517521A discloses a hydraulic control system and a hydraulic control method for a hybrid transmission. In the patent, a pressure-stabilizing accumulator is provided, and the pressure-stabilizing accumulator is connected to the clutch pressure control port. The pressure-stabilizing accumulator stabilizes the working pressure of the system through its internal elastic deformation and gas compressibility. The pressure-stabilizing accumulator acts like a buffer, reducing pressure fluctuations and shocks in the hydraulic system and improving the stability and reliability of the system. However, the pneumatic accumulator is a very mature solution, which is frequently used in various hydraulic systems to solve the problems of pressure fluctuations and shocks in the hydraulic system. Summary of the invention

[0004] The technical problem to be solved by the present invention is to solve the problem of gear shifting impact of a hydraulic transmission of a forklift.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A hydraulic control system suitable for a small-tonnage forklift, comprising: a forward clutch 1, a reverse clutch 2, a micro valve 3, a bidirectional buffer 4 and an electromagnetic reversing valve 5; the shift oil circuit passes through the micro valve 3 and the electromagnetic reversing valve 5 in sequence and then enters the forward clutch 1 and the reverse clutch 2 respectively; and the bidirectional buffer 4 is connected in series to the oil circuit entering the forward clutch 1 and the reverse clutch 2;

[0007] The bidirectional buffer 4 includes a cavity 41, and an elastic member 42, a first piston 43 and a second piston 44 located in the cavity 41;

[0008] The first piston 43 and the second piston 44 are respectively fixedly connected to the two ends of the elastic member 42 and divide the cavity 41 into a forward cavity 45 and a backward cavity 46 ; the elastic member 42 cooperates with the first piston 43 and the second piston 44 so that the first piston 43 and the second piston 44 can slide in the cavity 41 .

[0009] In one embodiment of the present invention, the hydraulic control system includes: an oil tank 61, a coarse oil filter 62 and an oil pump 63; the oil in the oil tank 61 is filtered by the coarse oil filter 62, and then pressurized by the oil pump 63 and divided into two paths at the outlet, one as a shift oil path and the other as a speed change oil path.

[0010] In one embodiment of the present invention, the hydraulic control system includes a main pressure regulating valve 71, a fine oil filter 72, and a torque converter 73; in the transmission oil circuit, the hydraulic oil passes through the main pressure regulating valve 71 and the fine oil filter 72 in sequence and enters the torque converter 73.

[0011] In one embodiment of the present invention, a safety valve 74 is provided on the transmission oil circuit between the fine oil filter 72 and the torque converter 73 .

[0012] In one embodiment of the present invention, the hydraulic control system includes a relief valve 75 ; the oil circuits of the inlet and outlet of the relief valve 75 are connected to the oil circuits of the inlet and outlet of the fine oil filter 72 .

[0013] In one embodiment of the present invention, the hydraulic control system includes a radiator 76 ; the high-temperature transmission oil passing through the torque converter 73 is returned to the bottom of the oil tank 61 after the heat is dissipated through the radiator 76 .

[0014] The present invention also discloses a shifting method using the above-mentioned hydraulic control system for a small-tonnage forklift, comprising:

[0015] During the gear switching process from forward gear to reverse gear, the electromagnetic reversing valve 5 works, the Y2 side channel of the electromagnetic reversing valve 5 loses power, the Y1 side channel is energized, the electromagnetic reversing valve 5 switches from the Y2 side channel to the Y1 side channel, and the transmission oil passing through the micro valve 3 and the electromagnetic reversing valve 5 is buffered by the two-way buffer 4 and enters the reverse clutch 2;

[0016] At this time, the forward clutch 1 is depressurized, the hydraulic oil in the forward cavity 45 continues to decrease, and at the same time, the hydraulic oil enters the reverse cavity 46. Under the action of the hydraulic oil in the forward cavity 45 and the reverse cavity 46, the first piston 43 and the second piston 44 reciprocate in the cavity 41, so that the hydraulic oil in the forward cavity 45 acts as a buffer for the oil pressure in the reverse cavity 46 and pushes the oil pressure in the reverse cavity 46, thereby achieving the oil pressure increase of the accelerated reverse gear and the pressure relief of the accelerated forward gear.

[0017] The same applies to the gear shifting process from reverse gear to forward gear.

[0018] In one embodiment of the present invention, the shifting method includes:

[0019] When the forward gear is selected from the neutral gear, the electromagnetic reversing valve 5 works, the Y2 side channel is electrically connected, and the transmission oil passes through the micro valve 3 and the electromagnetic reversing valve 5 and enters the forward clutch 1 through the forward cavity 45 and the first piston 43, and the forward clutch 1 is engaged to realize the forward gear;

[0020] The same applies when shifting from neutral to reverse gear.

[0021] In one embodiment of the present invention, the shifting method includes:

[0022] When the inching function is used, the driver steps on the inching pedal, which drives the valve stem of the inching valve 3 to move through the mechanical structure. After reaching a certain stroke, the oil in the main pressure pipeline and the clutch will bypass and leak into the oil pan, reducing or cutting off the clutch pressure to achieve the inching function.

[0023] When exiting the inching, the driver releases the inching pedal, and the mechanical structure drives the valve stem of the inching valve 3 to return to its original position, so that the main oil pressure and the oil pressure in the clutch can be quickly restored;

[0024] During the process of entering the inching function, the two-way buffer 4 assists in reducing the clutch pressure, and during the process of exiting the inching function, the two-way buffer 4 can also play a buffering role.

[0025] The present invention also provides a gearbox assembly, which uses the above-mentioned hydraulic control system suitable for a small-tonnage forklift.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The bidirectional buffer used in the present invention can buffer the gear oil pressure, increase the fault tolerance of the oil pressure fluctuation at the moment of gear shifting, reduce the rapid engagement of the clutch caused by the oil pressure fluctuation and the impact of rapid gear shifting, and can achieve gear switching more smoothly and reliably, avoiding the setback caused by impact. The NVH of the vehicle will be greatly improved, and the driving comfort and driving quality of the driver will also be improved simultaneously. Note: The NVH of the vehicle refers to noise, vibration and harshness.

[0028] The bidirectional buffer adopts an integrated bidirectional structure and uses the oil pressure of the opposite gear as an auxiliary. While buffering the gear oil pressure, during the forward gear stamping process, it uses the residual oil pressure in the reverse gear clutch to buffer the forward gear stamping process, and uses the forward gear oil pressure to push the bidirectional buffer to accelerate the reverse gear pressure relief, and vice versa.

[0029] The bidirectional buffer used in the present invention can buffer the oil pressure, realize smoother gear shifting, and reduce the impact on product function and reliability caused by impact wear of mechanical parts.

[0030] The hydraulic control system designed in the present invention eliminates the traditional front single-acting accumulator and connects an innovatively designed integrated bidirectional buffer in series between the forward clutch and the reverse clutch, thereby reducing the gear shift shock caused by power crossover due to insufficient pressure relief.

[0031] The bidirectional buffer proposed in the present invention does not have the air bag device of the traditional pneumatic accumulator, does not require an air valve or inflation, and does not simply connect two pneumatic accumulators in series. The bidirectional buffer innovatively proposes an integrated bidirectional structure, which saves the layout space of the engine compartment of a small-tonnage internal combustion forklift.

[0032] The hydraulic system designed in the present invention eliminates the gear shift shock, avoids the burning of the friction plate caused by human irregular operating habits, achieves a comfortable, stable and fast transmission effect, and makes the forklift have a more humane driving and operating performance.

[0033] The present invention realizes shift buffering in a purely mechanical manner, which is low in cost compared with an electronically controlled manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The figure is a schematic diagram of a hydraulic control system suitable for a small-tonnage forklift according to an embodiment of the present invention.

[0035] Figure 2 Schematic diagram of a bidirectional buffer according to an embodiment of the present invention.

[0036] Figure 3 It is a simplified forklift hydraulic control system of an embodiment of the present invention and a comparative schematic diagram.

[0037] Figure 4 It is a simulation schematic diagram of a forklift hydraulic control system according to an embodiment of the present invention.

[0038] Figure 5 Schematic diagram of simulation results of an embodiment of the present invention.

[0039] Figure 6 The figure is a schematic diagram of a gearbox assembly according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to facilitate those skilled in the art to understand the technical solution of the present invention, the technical solution of the present invention is further described in conjunction with the accompanying drawings of the specification.

[0041] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0042] See also Figure 1 As shown, the present invention provides a hydraulic control system suitable for a small-tonnage forklift, comprising a forward clutch 1, a reverse clutch 2, a micro valve 3, a bidirectional buffer 4 and an electromagnetic reversing valve 5. The shift oil circuit passes through the micro valve 3 and the electromagnetic reversing valve 5 in sequence and then enters the forward clutch 1 and the reverse clutch 2 respectively. In addition, the bidirectional buffer 4 is connected in series to the oil circuit entering the forward clutch 1 and the reverse clutch 2.

[0043] See also Figure 1 , 2 As shown, in one embodiment of the present invention, the bidirectional buffer 4 includes a cavity 41, and an elastic member 42, a first piston 43, and a second piston 44 located in the cavity 41. The first piston 43 and the second piston 44 are respectively fixed to the two ends of the elastic member 42, and divide the cavity 41 into a forward cavity 45 and a backward cavity 46. The elastic member 42 cooperates with the first piston 43 and the second piston 44, so that the first piston 43 and the second piston 44 can slide in the cavity 41.

[0044] In this embodiment, the elastic member 42 is, for example, a spring, and the elastic member 42 is not fixed to the cavity 41. In addition, the inner wall of the cavity 41 also serves as a guide for the first piston 43 and the second piston 44 to slide.

[0045] See also Figure 1 As shown, in one embodiment of the present invention, the hydraulic control system further includes an oil tank 61, a coarse oil filter 62 and an oil pump 63. The oil in the oil tank 61 is filtered by the coarse oil filter 62 and then pressurized by the oil pump 63 before being divided into two paths at the outlet, one as a shift oil path and the other as a speed change oil path.

[0046] In one embodiment of the present invention, the hydraulic control system includes a main pressure regulating valve 71, a fine oil filter 72, a torque converter 73, a safety valve 74, a relief valve 75 and a radiator 76. In the speed change oil circuit, the hydraulic oil passes through the main pressure regulating valve 71 and the fine oil filter 72 in sequence and enters the torque converter 73. The safety valve 74 is located on the speed change oil circuit between the fine oil filter 72 and the torque converter 73. The oil circuits of the inlet and outlet of the relief valve 75 are connected to the oil circuits of the inlet and outlet of the fine oil filter 72. The high-temperature transmission oil passing through the torque converter 73 returns to the bottom of the oil tank 61 after the heat is dissipated by the radiator 76.

[0047] See also Figure 1 ,2 As shown, the present invention also provides a shifting method for a hydraulic control system of a small tonnage forklift, comprising:

[0048] During the gear switching process from forward gear to reverse gear, the electromagnetic reversing valve 5 works, the Y2 side channel of the electromagnetic reversing valve 5 loses power, and the Y1 side channel is energized. The electromagnetic reversing valve 5 switches from being connected via the Y2 side channel to being connected via the Y1 side channel, and the transmission oil passes through the micro valve 3 and the electromagnetic reversing valve 5 and is buffered by the two-way buffer 4 into the reverse clutch 2.

[0049] At this time, the forward clutch 1 is depressurized, the hydraulic oil in the forward cavity 45 continues to decrease, and the hydraulic oil enters the reverse cavity 46 at the same time. The first piston 43 and the second piston 44 reciprocate in the cavity 41 under the action of the hydraulic oil in the forward cavity 45 and the reverse cavity 46, so that the hydraulic oil in the forward cavity 45 not only acts as a buffer for the oil pressure in the reverse cavity 46, but also promotes the oil pressure in the reverse cavity 46, thereby accelerating the reverse gear oil pressure increase and accelerating the forward gear pressure relief. The same is true for the gear shifting process from the reverse gear to the forward gear.

[0050] In this embodiment, during the gear switching process from the forward gear to the reverse gear, the forward gear clutch 6 releases pressure, and under the action of the bidirectional buffer 4, the forward clutch 1 can quickly release pressure during the process of the reverse clutch 2 buffering and pressure building, thereby achieving fast and effective gear switching and reducing power crossover. In this embodiment, power crossover means that the forward gear and the reverse gear work at the same time, that is, during the reverse gear pressure building process, there is still residual oil pressure in the forward gear, and vice versa.

[0051] In one embodiment of the present invention, the shifting method further includes: when shifting from neutral to forward gear, the electromagnetic reversing valve 5 works, the Y2 side channel is electrically connected, and the transmission oil passes through the micro valve 3 and the electromagnetic reversing valve 5 and enters the forward clutch 1 through the forward cavity 45 and the first piston 43 for buffering, and the forward clutch 1 engages to realize the forward gear, and the same applies to shifting from neutral to reverse gear.

[0052] In one embodiment of the present invention, when the inching function is used, the driver steps on the inching pedal, and the pedal drives the valve stem of the inching valve 3 to move through the mechanical structure. After reaching a certain stroke, the oil in the main pressure pipeline and the clutch will bypass and leak into the oil pan, reducing or cutting off the clutch pressure, and realizing the inching function. In the process of exiting the inching, the driver releases the inching pedal, and the mechanical structure drives the valve stem of the inching valve 3 to return to its original position, and the main oil pressure and the oil pressure in the clutch can be quickly restored. In the process of entering the inching function, the two-way buffer 4 can play a role in assisting in reducing the clutch pressure. In the process of exiting the inching function, the two-way buffer 4 can also play a buffering role, avoiding the gear impact caused by the rapid release of the inching pedal. In this embodiment, the clutch refers to the forward clutch 1 or the reverse clutch 2, and the inching valve 3 should be used in conjunction with the forward clutch 1 or the reverse clutch 2. The inching function refers to the gear oil pressure being appropriately reduced according to the pedal opening after stepping on the inching pedal, so as to reduce the amplitude of the transmitted power, and finally achieve the effect of vehicle inching. The appropriate reduction of the gear oil pressure can be understood as being consistent with the oil leakage principle of the normal gear.

[0053] In one embodiment of the present invention, two forklift hydraulic control systems are simulated using professional hydraulic simulation software. One set is the forklift hydraulic control system of the present invention, and the other set is based on the forklift hydraulic control system of the present invention, with the two-way buffer 4 removed. On the basis of keeping the others unchanged, a traditional accumulator 4A is added, and according to the conventional setting of the accumulator 4A, it is set in the oil circuit between the micro valve 3 and the electromagnetic reversing valve 5 as a comparison. In addition, since the gear shift shock is mainly related to the oil pressure change during the gear shift process, the hydraulic circuits such as the wet clutch and the torque converter inside the gearbox are not the main focus, so the hydraulic principle is simplified. In the simulation environment, a single piston rod cylinder with spring return is used instead of the wet clutch, and other hydraulic circuits including the torque converter are removed. For details, please refer to Figure 3 shown.

[0054] In one embodiment of the present invention, in the simulation environment, since the innovatively designed bidirectional buffer 4 is a non-standard hydraulic component, there is no standard component library in the simulation software that can be directly called. Therefore, the hydraulic component HCD module is used to build a bidirectional buffer component according to actual parameters. Figure 3 The simulation model built is as follows Figure 4 shown. Figure 4 In the figure, the left side is the forklift hydraulic control system where the accumulator 4A is located, and the right side is the forklift hydraulic control system where the bidirectional buffer 4 is located.

[0055] In one embodiment of the present invention, simulation is performed based on modeling, and the results are as follows: Figure 5As shown. Analyzing the simulation results, at the moment of shifting, at point ① in the figure, the instantaneous oil pressure fluctuation of the gear of the present invention (solid line in the curve graph) is greatly suppressed, the stamping time of the gear oil pressure is relatively slowed down by 40%, the slope of the oil pressure rising curve is reduced and smoother, and after holding the pressure (at point ② in the figure), the gear oil pressure of the new scheme is smoother. During the shifting process, the present invention buffers the gear oil pressure due to the bidirectional buffer 4, which slows down the fluctuation of the oil pressure at the moment of shifting, slows down the pressure rise curve, and allows the gear to be engaged smoothly and quickly. After holding the pressure, the fluctuation of the oil pressure is also filtered to ensure the stability of the gear oil pressure.

[0056] See also Figure 6 As shown, the present invention also provides a gearbox assembly, which uses the above-mentioned hydraulic control system suitable for a small-tonnage forklift.

[0057] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any reference numerals in the claims should not be regarded as limiting the claims involved.

[0058] The above-described embodiments merely represent implementation methods of the invention. The protection scope of the present invention is not limited to the above-described embodiments. For those skilled in the art, several modifications and improvements may be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A hydraulic control system suitable for small tonnage forklifts, characterized in that: include: A forward clutch (1), a reverse clutch (2), a micro-motion valve (3), a bidirectional buffer (4) and an electromagnetic reversing valve (5); the shift oil circuit passes through the micro-motion valve (3) and the electromagnetic reversing valve (5) in sequence and then enters the forward clutch (1) and the reverse clutch (2) respectively; and the bidirectional buffer (4) is connected in series to the oil circuit entering the forward clutch (1) and the reverse clutch (2); The bidirectional buffer (4) comprises a cavity (41), and an elastic member (42), a first piston (43) and a second piston (44) located in the cavity (41); The first piston (43) and the second piston (44) are respectively fixedly connected to the two ends of the elastic member (42), and divide the cavity (41) into a forward cavity (45) and a backward cavity (46); the elastic member (42) cooperates with the first piston (43) and the second piston (44), so that the first piston (43) and the second piston (44) can slide in the cavity (41).

2. The hydraulic control system for a small tonnage forklift according to claim 1, characterized in that: The hydraulic control system comprises: an oil tank (61), a coarse oil filter (62) and an oil pump (63); the oil in the oil tank (61) is filtered by the coarse oil filter (62), and then pressurized by the oil pump (63) before being divided into two paths at the outlet, one path being used as a gear shifting oil path and the other being used as a speed change oil path.

3. The hydraulic control system for a small tonnage forklift according to claim 2, characterized in that: The hydraulic control system comprises a main pressure regulating valve (71), a fine oil filter (72), and a torque converter (73); in a speed change oil circuit, hydraulic oil passes through the main pressure regulating valve (71) and the fine oil filter (72) in sequence and enters the torque converter (73).

4. The hydraulic control system for a small tonnage forklift according to claim 3, characterized in that: A safety valve (74) is provided on the speed change oil circuit between the fine oil filter (72) and the torque converter (73).

5. The hydraulic control system for a small tonnage forklift according to claim 3, characterized in that: The hydraulic control system comprises a relief valve (75); the oil circuits at the inlet and outlet of the relief valve (75) are connected to the oil circuits at the inlet and outlet of the fine oil filter (72).

6. The hydraulic control system for a small tonnage forklift according to claim 3, characterized in that: The hydraulic control system comprises a radiator (76); high-temperature transmission oil passing through the torque converter (73) is returned to the bottom of the oil tank (61) after heat is dissipated through the radiator (76).

7. A shifting method for a hydraulic control system of a small tonnage forklift according to any one of claims 1 to 6, characterized in that: include: During the gear switching process from the forward gear to the reverse gear, the electromagnetic reversing valve (5) works, the Y2 side channel of the electromagnetic reversing valve (5) loses power, the Y1 side channel is energized, the electromagnetic reversing valve (5) switches from the Y2 side channel to the Y1 side channel, and the transmission oil passing through the micro valve (3) and the electromagnetic reversing valve (5) is buffered by the bidirectional buffer (4) and enters the reverse clutch (2); At this time, the forward clutch (1) is depressurized, and the hydraulic oil in the forward cavity (45) continues to decrease. At the same time, the hydraulic oil enters the reverse cavity (46). Under the action of the hydraulic oil in the forward cavity (45) and the reverse cavity (46), the first piston (43) and the second piston (44) reciprocate in the cavity (41), so that the hydraulic oil in the forward cavity (45) not only serves as a buffer for the oil pressure in the reverse cavity (46), but also promotes the oil pressure in the reverse cavity (46), thereby achieving the oil pressure increase of the accelerated reverse gear and the pressure relief of the accelerated forward gear; The same applies to the gear shifting process from reverse gear to forward gear.

8. The shifting method of the hydraulic control system for a small tonnage forklift according to claim 7, characterized in that: Shifting methods include: When the forward gear is engaged from the neutral gear, the electromagnetic reversing valve (5) works, the Y2 side channel is electrically connected, and the transmission oil passes through the micro valve (3) and the electromagnetic reversing valve (5) and enters the forward clutch (1) through the forward cavity (45) and the first piston (43) for buffering, and the forward clutch (1) is engaged to achieve the forward gear; The same applies when shifting from neutral to reverse gear.

9. The shifting method of the hydraulic control system for a small tonnage forklift according to claim 7, characterized in that: Shifting methods include: When the inching function is used, the driver steps on the inching pedal, and the pedal drives the valve stem of the inching valve (3) to move through the mechanical structure. After reaching a certain stroke, the oil in the main pressure pipeline and the clutch will bypass and leak into the oil pan, reducing or cutting off the clutch pressure, thereby realizing the inching function; During the process of exiting the inching, the driver releases the inching pedal, and the mechanical structure drives the valve stem of the inching valve (3) to return to its original position, so that the main oil pressure and the oil pressure in the clutch can be quickly restored; In the process of entering the inching function, the bidirectional buffer (4) assists in reducing the clutch pressure, and in the process of exiting the inching function, the bidirectional buffer (4) can also play a buffering role.

10. A gearbox assembly, characterized in that: A hydraulic control system suitable for a small-tonnage forklift truck according to any one of claims 1 to 6.

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