Shift control system and work machine

Abstract

The utility model relates to a variable speed control system for an operation machine and the operation machine comprising the variable speed control system. The variable speed control system comprises a mechanical control high-low speed switching device and an electric control gear shifting device (100) comprising an electric control variable speed valve (103). The electric control speed change valve (103) comprises a valve body (5), a reversing valve (3) and an electromagnetic valve (4), wherein the reversing valve (3) and the electromagnetic valve (4) are installed on the valve body (5) so as to control connection and disconnection of the gear clutch (1). According to the variable speed control system, a mechanically-controlled high-low speed switching device is reserved, and an electric control gear shifting device comprising an electric control variable speed valve is adopted as a gear shifting control part which only needs to be controlled frequently. Therefore, on one hand, the fatigue driving problem caused by frequent control of the mechanical speed change valve is solved, and on the other hand, the cost increase is inhibited.

Description

Technical Field

[0001] The utility model relates to the technical field of engineering machinery, in particular to a speed control system for an operating machinery and an operating machinery comprising the speed control system. Background Art

[0002] The transmission of working machines such as loaders, excavators, graders, bulldozers, cranes, etc. usually has a large number of gears and performs gear shifting operations with the aid of a speed control system. A known speed control system has two speed control parts, wherein the first speed control part can realize the switching of the working machine between multiple gears including a reverse gear and two or more forward gears (for example, two forward gears with different speed ratios), and the second speed control part can realize additional high-low speed switching functions.

[0003] The first speed control part of the speed control system controls the corresponding gear clutch to shift gears by operating the mechanical shift handle to pull the valve stem of the mechanical speed change valve via a flexible shaft, and the second speed control part controls the high and low speed shift synchronizer to switch high and low speeds by operating another high and low speed switching handle to pull the high and low speed shift fork via another flexible shaft. Frequent manipulation of the mechanical handle can easily cause operator fatigue. There are also high-end electronically controlled full-power shift transmissions in the prior art, but the use of such transmissions increases the layout space and manufacturing cost of the entire machine. Utility Model Content

[0004] The purpose of the present invention is to solve at least one of the above problems and / or other problems existing in the prior art.

[0005] To achieve the above-mentioned purpose, according to one aspect of the utility model, a speed control system for a working machine is provided. The speed control system comprises: a mechanically controlled high-low speed switching device; and an electronically controlled shifting device comprising an electronically controlled speed change valve, wherein the electronically controlled speed change valve comprises a valve body and a reversing valve and a solenoid valve mounted on the valve body to control the engagement and disengagement of a gear clutch.

[0006] According to one embodiment of the utility model, the reversing valve includes a first reversing valve and a second reversing valve installed on a first side of the valve body, and the solenoid valve includes a first solenoid valve, a second solenoid valve and a third solenoid valve installed on a second side of the valve body, wherein the first side and the second side are opposite to each other.

[0007] According to one embodiment of the utility model, the first reversing valve is constructed as a two-position three-way valve, and the first solenoid valve controls the first reversing valve to switch between a first position and a second position. When the first reversing valve is in the first position, the first gear clutch in the gear clutch is disengaged, and when the first reversing valve is in the second position, the first gear clutch is engaged.

[0008] According to one embodiment of the utility model, the second reversing valve is constructed as a three-position four-way valve, and the second solenoid valve and the third solenoid valve control the second reversing valve to switch between a first position, a second position and a third position. When the second reversing valve is in the first position, the second gear clutch and the third gear clutch in the gear clutch are both disengaged, when the second reversing valve is in the second position, the second gear clutch is engaged, and when the second reversing valve is in the third position, the third gear clutch is engaged.

[0009] According to an embodiment of the present invention, one of the second gear clutch and the third gear clutch is a reverse clutch.

[0010] According to one embodiment of the utility model, each of the first solenoid valve, the second solenoid valve and the third solenoid valve is a pilot solenoid valve having an oil inlet, a working oil port and an oil return port, the oil inlet being connected to the hydraulic oil supply port of the valve body, the working oil port being connected to the control chamber of the corresponding reversing valve, the oil return port being connected to the oil return passage, when the pilot solenoid valve is in a power-off state, the working oil port is connected to the oil return port, and when the pilot solenoid valve is in a power-on state, the working oil port is connected to the oil inlet.

[0011] According to an embodiment of the present utility model, the electronically controlled speed change valve further includes a shift buffer valve disposed on the first side surface of the valve body.

[0012] According to an embodiment of the present utility model, the electronically controlled shift device further comprises a shift operator and a shift controller, wherein the shift controller is configured to control the power on and power off of the solenoid valve according to an electrical signal output by the shift operator.

[0013] According to one embodiment of the utility model, the high-speed and low-speed switching device includes a mechanical shift handle, a high-speed and low-speed shift fork, and a flexible shaft or a cable connecting the mechanical shift handle and the high-speed and low-speed shift fork.

[0014] According to another aspect of the present invention, a working machine is provided. The working machine includes the speed change control system as described above.

[0015] The speed control system of the utility model retains the high-low speed switching device of mechanical manipulation, and only the shift control part that needs to be frequently manipulated adopts the electronically controlled shift device including the electronically controlled speed change valve. Therefore, on the one hand, the problem of fatigue driving caused by frequent manipulation of the mechanical speed change valve is solved, and on the other hand, the increase in cost is suppressed. Moreover, the electronically controlled speed change valve in the utility model can be mutually installed with the existing mechanical speed change valve, without changing the structure of the transmission and the arrangement of the transmission on the working machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The features and advantages of the present invention will be clearly understood through the detailed description provided below with reference to the accompanying drawings. It should be understood that the following drawings are merely schematic and not necessarily drawn to scale, and thus cannot be regarded as limiting the present invention, wherein:

[0017] Figure 1 A schematic diagram of an electronically controlled shifting device of a speed control system according to an exemplary embodiment of the present utility model is shown.

[0018] Figure 2 The schematic diagram of the electronically controlled speed change valve in the electronically controlled shifting device is shown.

[0019] Figure 3 A three-dimensional view of the electronically controlled speed-changing valve is shown.

[0020] Figure 4 An exploded view of the electronically controlled speed-changing valve is shown.

[0021] Figure 5 A three-dimensional view showing a valve body of the electronically controlled speed-changing valve.

[0022] Figure 6 A bottom view of the valve body is shown.

[0023] Figure 7 A bottom view of the electronically controlled speed-changing valve is shown.

[0024] Description of reference numerals:

[0025] 100. Electronically controlled shift device; 101. Shift operator; 102. Shift controller; 103. Electronically controlled speed change valve; 1. Shift clutch; 11. First gear clutch; 12. Second gear clutch; 13. Third gear clutch; 2. Pressurized fluid source; 3. Reversing valve; 31. First reversing valve; 32. Second reversing valve; 4. Solenoid valve; 41. First solenoid valve; 42. Second solenoid valve; 43. Third solenoid valve; 5. Valve body; 51. Hydraulic oil supply port; 52. Lubricating oil supply port; 53. Pressure measuring port; 54. High-pressure oil circuit; 55. Lubricating oil circuit; 56. First gear oil circuit; 57. Second gear oil circuit; 58. Third gear oil circuit; 6. Shift buffer valve; 7. Protective cover; 8. Oil sealing plate; 9: Mounting bolts. DETAILED DESCRIPTION

[0026] Embodiments of the present invention are described below with reference to the accompanying drawings. In the following description, many specific details are set forth so that those skilled in the art can more fully understand and implement the present invention. However, it is obvious to those skilled in the art that the implementation of the present invention may not have some of these specific details. In addition, it should be understood that the present invention is not limited to the specific embodiments described. On the contrary, any combination of the features and elements described below may be considered to implement the present invention, regardless of whether they relate to different embodiments. Therefore, the following aspects, features, embodiments and advantages are for illustrative purposes only and should not be regarded as elements or limitations of the claims unless clearly stated in the claims.

[0027] In the following, terms such as "first", "second", etc. are used to describe the elements of the present application. These terms are only used to distinguish the various elements, and are not used to limit the nature, order or number of these elements. The terms "including" and "having" are used to express an open-ended inclusive meaning, and mean that there may be additional elements / components in addition to the listed elements / components.

[0028] The following describes a speed control system according to an exemplary embodiment of the utility model in conjunction with the accompanying drawings. The speed control system of this embodiment can be used to control the shifting of a 428 fixed-axis transmission widely used in working machinery such as a 30 loader. The speed control system includes an electronically controlled shifting device 100 and a mechanically controlled high-low speed switching device. The mechanically controlled high-low speed switching device may include a mechanical shift handle, a high-low speed fork, and a flexible shaft or cable connecting the mechanical shift handle and the high-low speed fork. Such a high-low speed switching device is well known to those skilled in the art, and its description and illustration are omitted here.

[0029] Figure 1 Schematic diagram of the electronically controlled shifting device 100 is shown. Figure 1 As shown in FIG. 1 , the electronically controlled shifting device 100 includes a shifting operator 101, a shifting controller 102, and an electronically controlled speed change valve 103 which are electrically connected in sequence. The shifting operator 101 may be as follows: Figure 1 The mechanical shift handle shown may also be other buttons, joysticks, etc. that can convert the operator's shift operation into an electrical signal output. The electrical signal output by the shift operator 101 is transmitted to the shift controller 102. The shift controller 102 controls the electronically controlled speed change valve 103 to shift gears according to the received electrical signal. Figure 1 Also shown is a transmission that is controlled to shift gears by the speed control system of this embodiment, in which the electronically controlled speed change valve 103 is installed on the top of the transmission case.

[0030] Figure 21 shows a schematic diagram of the electronically controlled speed-changing valve 103 in this embodiment. Figures 3 to 7 The structure of the electronically controlled speed change valve 103 is shown. The electronically controlled speed change valve 103 replaces the traditional mechanical speed change valve to control the engagement and separation of the gear clutch 1 to achieve gear conversion.

[0031] The electronically controlled speed-changing valve 103 in this embodiment is configured to control three gear clutches 1, namely, a first gear clutch 11, a second gear clutch 12, and a third gear clutch 13. The first gear clutch 11 may be a clutch for a forward gear with a first speed ratio. The second gear clutch 12 may be a clutch for a forward gear with a second speed ratio. The third gear clutch 13 may be a reverse gear clutch.

[0032] For example, when the high-low speed switching device is in the normal low-speed gear position, the first forward gear F1 can be realized when the first gear clutch 11 is engaged, the second forward gear F2 can be realized when the second gear clutch 12 is engaged, and the first reverse gear R1 can be realized when the third gear clutch 13 is engaged. On the other hand, when the high-low speed switching device is switched to the high-speed gear position, the third forward gear F3 can be realized when the first gear clutch 11 is engaged, the fourth forward gear F4 can be realized when the second gear clutch 12 is engaged, and the second reverse gear R2 can be realized when the third gear clutch 13 is engaged.

[0033] like Figures 2 to 4 As shown, the electric control speed change valve 103 in this embodiment includes two reversing valves 3 and three solenoid valves 4, which are installed on the valve body 5. More specifically, the two reversing valves 3 include a first side surface ( Figure 3 and Figure 4 The first reversing valve 31 and the second reversing valve 32 are installed on the right side of the valve body 5, and the three solenoid valves 4 include a first reversing valve 31 and a second reversing valve 32 installed on the second side of the valve body 5 ( Figure 3 and Figure 4 The first solenoid valve 41, the second solenoid valve 42 and the third solenoid valve 43 (on the left side in FIG. 1).

[0034] Each reversing valve 3 is hydraulically connected between a pressurized fluid source 2 and a corresponding gear clutch 1. The pressurized fluid source 2 may include a pump for pressurizing a fluid, in particular hydraulic oil, which may be driven by an engine or an electric motor. Under normal conditions, each reversing valve 3 is in a position where the hydraulic connection between the corresponding gear clutch 1 and the pressurized fluid source 2 is disconnected, so that the gear clutch 1 is disengaged. When it is necessary to shift to a certain gear, the corresponding gear clutch 1 can be engaged by energizing the corresponding solenoid valve 4 to switch the position of the corresponding reversing valve 3.

[0035] Specifically, Figure 2As shown, the first reversing valve 31 is constructed as a two-position three-way valve, which has three oil ports, namely, an oil inlet port, an oil return port, and a working oil port, and can move between a first position and a second position. By means of the oil circuit formed in the valve body 5 and the external connecting pipeline, the oil inlet port of the first reversing valve 31 is connected to the pressurized fluid source 2, the oil return port is connected to the oil storage tank, and the working oil port is connected to the pressure chamber of the first gear clutch 11. The first reversing valve 31 is at its first axial end ( Figure 2 The right end of the first axial end has a control cavity, and the second axial end opposite to the first axial end ( Figure 2 A spring is provided at the left end of the housing.

[0036] When the first reversing valve 31 is in the first position, its working oil port is connected to the oil return port. Figure 2 As shown in the left state box in FIG, the hydraulic oil in the pressure chamber of the first gear clutch 11 flows back to the oil storage tank through the interconnected working oil port and the return oil port, and the first gear clutch 11 is disengaged.

[0037] When the first reversing valve 31 is in the second position, its working oil port is connected with the oil inlet port. Figure 2 As shown in the right state box in FIG, the hydraulic oil from the pressurized fluid source 2 flows to the pressure chamber of the first gear clutch 11 through the oil inlet port and the working oil port that are interconnected, thereby actuating the first gear clutch 11 to engage it.

[0038] The switching of the first reversing valve 31 between the first position and the second position is controlled by the first solenoid valve 41. In this embodiment, the first solenoid valve 41 is configured as a pilot solenoid valve having an oil inlet, an oil return port, and a working oil port. By means of the oil circuit formed in the valve body 5 and the external connecting pipeline, the oil inlet of the first solenoid valve 41 is connected to the pressurized fluid source 2, the oil return port is connected to the oil storage tank, and the working oil port is connected to the control chamber of the first reversing valve 31.

[0039] When the first solenoid valve 41 is in a normal power-off state, its working oil port is connected to the oil return port. Figure 2 As shown in the left state box in FIG, the hydraulic oil in the control chamber of the first reversing valve 31 flows back to the oil storage tank via the interconnected working oil port and the return oil port, so that the first reversing valve 31 is maintained in the first position under the action of the spring.

[0040] When the first solenoid valve 41 is in the energized state, its working oil port is connected to the oil inlet port. Figure 2 As shown in the right state box in , the hydraulic oil from the pressurized fluid source 2 flows to the control chamber of the first reversing valve 31 through the interconnected oil inlet and working oil port to overcome the force of the spring and switch the first reversing valve 31 to the second position.

[0041] The second reversing valve 32 is constructed as a three-position four-way valve, which has four oil ports, namely, an oil inlet, an oil return port, a first working oil port, and a second working oil port, and can be switched between a first position, a second position, and a third position. By means of the oil circuit formed in the valve body 5 and the external connecting pipeline, the oil inlet of the second reversing valve 32 is connected to the pressurized fluid source 2, the oil return port is connected to the oil storage tank, the first working oil port is connected to the pressure chamber of the second gear clutch 12, and the second working oil port is connected to the pressure chamber of the third gear clutch 13. The second reversing valve 32 is also connected at its first axial end ( Figure 2 The right end of the first axial end has a first control chamber, and the second axial end opposite to the first axial end ( Figure 2 The left end in the middle) has a second control chamber. In addition, the second reversing valve 32 is also provided with a first spring at its second axial end, and a second spring at its first axial end.

[0042] When the second reversing valve 32 is in the first position, the first working oil port and the second working oil port are both connected to the oil return port. Figure 2 As shown in the middle state box in , the hydraulic oil in the pressure chamber of the second gear clutch 12 and the third gear clutch 13 flows back to the oil storage tank through the first or second working oil port and the return oil port that are interconnected, and the second gear clutch 12 and the third gear clutch 13 are both separated.

[0043] When the second reversing valve 32 is in the second position, its first working oil port is connected to the oil inlet, and its second working oil port is connected to the oil return port. Figure 2 As shown in the right state box in , the hydraulic oil from the pressurized fluid source 2 flows to the pressure chamber of the second gear clutch 12 via the oil inlet port and the first working oil port that are connected to each other, thereby actuating the second gear clutch 12 to engage it, while the third gear clutch 13 remains in a disengaged state.

[0044] When the second reversing valve 32 is in the third position, its first working oil port is connected to the oil return port, and its second working oil port is connected to the oil inlet port. Figure 2 As shown in the left state box in FIG, the hydraulic oil from the pressurized fluid source 2 flows to the pressure chamber of the third gear clutch 13 via the oil inlet port and the second working oil port that are connected to each other, thereby actuating the third gear clutch 13 to engage it, while the second gear clutch 12 remains in a disengaged state.

[0045] The switching of the second reversing valve 32 between the first position, the second position and the third position is controlled by the second solenoid valve 42 and the third solenoid valve 43. Similar to the first solenoid valve 41, the second solenoid valve 42 and the third solenoid valve 43 are both constructed as pilot solenoid valves having an oil inlet, an oil return port and a working oil port. By means of the oil circuit formed in the valve body 5 and the external connecting pipeline, the oil inlets of the second solenoid valve 42 and the third solenoid valve 43 are both connected to the pressurized fluid source 2, the oil return ports of the second solenoid valve 42 and the third solenoid valve 43 are both connected to the oil storage tank, and the working oil ports of the second solenoid valve 42 and the third solenoid valve 43 are respectively connected to the first control chamber and the second control chamber of the first reversing valve 31.

[0046] When the second solenoid valve 42 and the third solenoid valve 43 are both in the normal power-off state, their working oil ports are connected to the oil return port, so that the first control chamber and the second control chamber of the second reversing valve 32 return to the oil storage tank via the interconnected working oil port and the oil return port, so that the second reversing valve 32 is maintained in the first position under the mutual balance of the first spring and the second spring.

[0047] When the second solenoid valve 42 is in the energized state and the third solenoid valve 43 is in the de-energized state, the working oil port of the second solenoid valve 42 is connected to the oil inlet port, so that the hydraulic oil from the pressurized fluid source 2 flows to the first control chamber of the second reversing valve 32 via the interconnected oil inlet port and working oil port of the second solenoid valve 42, so as to overcome the action of the first spring and switch the second reversing valve 32 to the second position.

[0048] When the third solenoid valve 43 is in the energized state and the second solenoid valve 42 is in the de-energized state, the working oil port of the third solenoid valve 43 is connected to the oil inlet port, so that the hydraulic oil from the pressurized fluid source 2 flows to the second control chamber of the second reversing valve 32 via the interconnected oil inlet port and working oil port of the third solenoid valve 43, so as to overcome the action force of the second spring and switch the second reversing valve 32 to the third position.

[0049] like Figure 2 As shown, the electronically controlled speed change valve 103 in this embodiment further includes a shift buffer valve 6 disposed between the oil inlet of the first reversing valve 31 and the second reversing valve 32 and the pressurized fluid source 2. Figure 3 and Figure 4 As shown, the shift buffer valve 6 can be installed side by side with the first reversing valve 31 and the second reversing valve 32 on the first side of the valve body 5. The structure and function of the shift buffer valve 6 are well known to those skilled in the art, and a detailed description thereof is omitted here.

[0050] Figure 3 and Figure 4Also shown is a protective cover 7 mounted on the second side of the valve body 5 for protecting the three solenoid valves 4, and an oil sealing plate 8 arranged at the bottom of the valve body 5 for mounting on the transmission case. A sealing gasket is arranged between the protective cover 7 and the second side of the valve body 5 and between the oil sealing plate 8 and the bottom of the valve body 5. A plurality of through holes for fastening bolts 9 to pass through are formed corresponding to each other on the valve body 5, the oil sealing plate 8 and the sealing gasket therebetween. The fastening bolts 9 can be tightened to the transmission case through these through holes, thereby mounting the electronically controlled speed change valve 103 on the transmission case.

[0051] The first side surface of the valve body 5 is formed with accommodating chambers for respectively accommodating the first reversing valve 31, the second reversing valve 32 and the shift buffer valve 6. The second side surface of the valve body 5 is formed with accommodating chambers for respectively accommodating the first solenoid valve 41, the second solenoid valve 42 and the third solenoid valve 43.

[0052] like Figures 3 to 5 As shown, a hydraulic oil supply port 51, a lubricating oil supply port 52 and three pressure measuring ports 53 are formed on the upper surface of the valve body 5. The hydraulic oil supply port 51 can be connected to the above-mentioned pressurized fluid source 2 through a hydraulic oil supply pipe. The lubricating oil supply port 52 can be connected to a lubricating oil supply source, such as an oil pan, through a lubricating oil supply pipe. Figure 3 and Figure 4 Only the joints of the hydraulic oil supply pipe and the lubricating oil supply pipe are shown. The three pressure measuring ports 53 are respectively connected to the working oil port of the first reversing valve 31 and the two working oil ports of the second reversing valve 32. The pressure measuring ports 53 are usually closed by plugs. When maintenance and overhaul are required, the plugs can be removed and oil pressure sensors can be installed to measure the pressure at the corresponding working oil ports.

[0053] A plurality of oil circuits are formed inside the valve body 5, including a hydraulic oil circuit and a lubricating oil circuit. Figure 6 The oil circuit portion formed at the bottom of the valve body 5 is shown, including: a high-pressure oil circuit 54, which is connected to the hydraulic oil supply port 51, the oil inlet ports of each reversing valve 3, the oil inlet ports of each solenoid valve 4 and the oil inlet port of the shift buffer valve 6; a lubricating oil circuit 55, which is connected to the lubricating oil supply port 52 and the lubrication parts of each gear clutch 1; a first gear oil circuit 56, which is connected to the working oil port of the first reversing valve 31 and the working chamber of the first gear clutch 11; a second gear oil circuit 57, which is connected to the first working oil port of the second reversing valve 32 and the working chamber of the second gear clutch 12; a third gear oil circuit 58, which is connected to the second working oil port of the second reversing valve 32 and the working chamber of the third gear clutch 13.

[0054] like Figure 4 As shown, a plurality of through holes are formed on the oil sealing plate 8 and the sealing gasket between the oil sealing plate 8 and the bottom of the valve body 5 in a one-to-one correspondence. Figure 7, these through holes can be roughly divided into three categories. The first type of through holes is used for the fastening bolts 9 mentioned above to pass through. The second type of through holes is used to install other bolts to press the valve body 5 and the oil sealing plate 8 and the sealing gasket between the two to prevent leakage of hydraulic oil or lubricating oil. The third type of through holes remain open and are used to connect to the working chamber or lubrication part of each gear clutch 1, or as an oil return hole to connect to the oil return passage on the transmission case.

[0055] The utility model also provides an operating machine comprising the speed change control system.

[0056] Industrial Applicability

[0057] The speed control system according to the utility model can be applied to a variety of working machines, such as loaders, excavators, graders, bulldozers or cranes.

[0058] At present, the speed control systems of these working machines usually use a combination of a mechanical speed change valve controlled by a mechanical shift handle and a high-low speed switching device controlled by a high-low speed shift handle. When working on the site, the high-low speed switching device is placed in the low-speed gear position, and the operator can operate the mechanical shift handle to pull the valve stem of the mechanical speed change valve through the shift soft shaft to achieve the conversion between low-speed gears (for example, forward first gear F1, forward second gear F2, reverse first gear R1). When it is necessary to move the work site, the high-low speed switching device can be switched to the high-speed gear position by operating the high-low speed shift handle, and then the mechanical shift handle can be operated to achieve the conversion between different high-speed gears (for example, forward third gear F3, forward fourth gear F4, reverse second gear R2).

[0059] Considering that the switching frequency between low-speed gears in field operations is much higher than the switching frequency between high-speed and low-speed gears and the switching frequency between high-speed gears in the case of transferring work sites or long-distance transportation, the utility model proposes to replace only the mechanical shift valve with an electronically controlled speed change valve, while retaining the mechanically controlled high-speed and low-speed switching device. This not only solves the problem of fatigue driving caused by frequent manipulation of the mechanical speed change valve, but also suppresses the increase in cost compared to the use of an electronically controlled full-power shift transmission.

[0060] In addition, the electronically controlled speed-changing valve in the present invention can be installed interchangeably with the existing mechanical speed-changing valve, without changing the structure of the transmission and the arrangement of the transmission on the working machine.

[0061] For those skilled in the art, various modifications and variations may be made to the embodiments disclosed above without departing from the scope or spirit of the utility model. Other embodiments of the utility model will be apparent to those skilled in the art from the practice of the utility model disclosed in this specification. This specification and the examples disclosed therein should be considered to be illustrative only, and the true scope of the utility model is specified by the appended claims and their equivalents.

Claims

1. A speed control system, characterized in that: include: Mechanically operated high and low speed switching device; and An electrically controlled shifting device (100) includes an electrically controlled shifting valve (103), wherein the electrically controlled shifting valve (103) includes a valve body (5) and a reversing valve (3) and a solenoid valve (4) mounted on the valve body (5) to control the engagement and disengagement of a gear clutch (1).

2. The speed control system according to claim 1, characterized in that: The reversing valve (3) comprises a first reversing valve (31) and a second reversing valve (32) installed on a first side surface of the valve body (5). The solenoid valve (4) comprises a first solenoid valve (41), a second solenoid valve (42) and a third solenoid valve (43) installed on the second side surface of the valve body (5). The first side surface and the second side surface are opposite to each other.

3. The speed control system according to claim 2, characterized in that: The first reversing valve (31) is configured as a two-position three-way valve. The first solenoid valve (41) controls the first reversing valve (31) to switch between a first position and a second position. When the first reversing valve (31) is in the first position, the first gear clutch (11) in the gear clutch (1) is disengaged. When the first reversing valve (31) is in the second position, the first gear clutch (11) is engaged.

4. The speed control system according to claim 2, characterized in that: The second reversing valve (32) is configured as a three-position four-way valve. The second solenoid valve (42) and the third solenoid valve (43) control the second reversing valve (32) to switch between a first position, a second position and a third position. When the second reversing valve (32) is in the first position, the second gear clutch (12) and the third gear clutch (13) in the gear clutch (1) are both disengaged. When the second reversing valve (32) is in the second position, the second gear clutch (12) is engaged. When the second reversing valve (32) is in the third position, the third gear clutch (13) is engaged.

5. The speed control system according to claim 4, characterized in that: One of the second gear clutch (12) and the third gear clutch (13) is a reverse clutch.

6. The speed control system according to claim 2, characterized in that: Each of the first solenoid valve (41), the second solenoid valve (42) and the third solenoid valve (43) is a pilot solenoid valve having an oil inlet, a working oil port and an oil return port, wherein the oil inlet is connected to the hydraulic oil supply port (51) of the valve body (5), the working oil port is connected to the control chamber of the corresponding reversing valve, and the oil return port is connected to the oil return passage. When the pilot solenoid valve is in a power-off state, the working oil port is connected to the oil return port, and when the pilot solenoid valve is in a power-on state, the working oil port is connected to the oil inlet.

7. The speed change control system according to any one of claims 2 to 6, characterized in that: The electronically controlled speed change valve (103) further comprises a shift buffer valve (6) arranged on the first side surface of the valve body (5).

8. The speed change control system according to any one of claims 1 to 6, characterized in that: The electronically controlled shift device (100) further comprises a shift operator (101) and a shift controller (102), wherein the shift controller (102) is configured to control the power on and power off of the solenoid valve (4) according to an electrical signal output by the shift operator (101).

9. The speed change control system according to any one of claims 1 to 6, characterized in that: The high-speed and low-speed switching device comprises a mechanical shift handle, a high-speed and low-speed shift fork, and a flexible shaft or a cable connecting the mechanical shift handle and the high-speed and low-speed shift fork.

10. A working machine, characterized in that: The invention comprises a speed change control system according to any one of claims 1 to 9.

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