Transmission hydraulic control system for a working machine and working machine

Abstract

The utility model relates to a transmission hydraulic control system and engineering machinery for engineering machinery. Transmission hydraulic control system includes: for providing control hydraulic fluid's pump (002), with the pump (002) hydraulic connection's gear shift valve (005), this gear shift valve (005) is used for controlling the flow of hydraulic fluid to control gear position, be provided with brake gear cut solenoid valve (017) in the hydraulic line between gear shift valve (005) and pump (002), this brake gear cut solenoid valve (017) can switch between the on state and the off state, in the on state, brake gear cut solenoid valve (017) is connected in the hydraulic connection between gear shift valve (005) and pump (002), and in the off state, brake gear cut solenoid valve (017) is cut off in the hydraulic connection between gear shift valve (005) and pump (002).

Description

Technical Field

[0001] This utility model relates to the field of engineering machinery technology, specifically to a hydraulic control system for a transmission in engineering machinery, and engineering machinery, especially loaders. Background Technology

[0002] Currently, most mainstream construction machinery in China, especially loaders, uses an air-over-hydraulic braking system. This system is equipped with a pressurized air source, which can control the on / off of the transmission's shift hydraulic circuit by drawing out a pressurized gas line, thereby achieving the function of cutting off the transmission's oil supply and gear shifting during braking. This effectively improves the service life of the transmission system. However, with technological advancements, mid-to-high-end products are gradually adopting wet axles and fully hydraulic braking systems, which no longer have a pressurized air source. High-end products are usually equipped with electronically controlled transmissions, easily achieving the braking gear shifting function through gear shift solenoid valves. But for mid-range customers, mechanical shift transmissions are still preferred, making the implementation of braking gear shifting a challenge. Some manufacturers have attempted to use the hydraulic oil of a fully hydraulic braking system to control the transmission's shift hydraulic control lines, but this carries the risk of hydraulic oil and transmission lubricating oil mixing, leading to reduced system reliability and potential malfunctions.

[0003] Therefore, for construction machinery, especially loaders, with wet axles, fully hydraulic braking systems, and mechanical shift transmissions, there is an urgent need for a brake cut-off solution to avoid the risk of oil leakage and to ensure safe operation under special working conditions such as slopes. Utility Model Content

[0004] The technical problem this utility model aims to solve is that in mid-range construction machinery, especially loaders, which use wet axles and fully hydraulic braking systems, the braking disengagement function cannot be achieved due to the lack of a pressurized air source or electronically controlled transmission. Therefore, there is an urgent need to provide a safe, reliable, and cost-effective solution.

[0005] This utility model proposes a hydraulic control system for a transmission in engineering machinery, the hydraulic control system comprising:

[0006] Pumps used to provide hydraulic fluid for control purposes;

[0007] A shift valve that is hydraulically connected to the pump is used to control the flow of hydraulic fluid to control the gear position;

[0008] A brake cut-off solenoid valve is installed in the hydraulic line between the shift valve and the pump.

[0009] The brake cut-off solenoid valve can switch between an on state and an off state. In the on state, the brake cut-off solenoid valve connects the hydraulic connection between the shift valve and the pump, while in the off state, the brake cut-off solenoid valve disconnects the hydraulic connection between the shift valve and the pump.

[0010] According to a preferred embodiment, the brake stop solenoid valve is configured as a two-position three-way solenoid valve.

[0011] According to a preferred embodiment, the brake stop solenoid valve is in the on state when it is not energized, wherein the oil inlet and the working port are connected and the oil drain port is closed; the brake stop solenoid valve is in the off state when it is energized, wherein the oil inlet is closed and the working port and the oil drain port are connected.

[0012] According to a preferred embodiment, the pump outlet is connected to the oil inlet of the brake stop solenoid valve, the working port of the brake stop solenoid valve is connected to the inlet of the shift valve, and the drain port of the brake stop solenoid valve is connected to the low-pressure oil tank.

[0013] According to a preferred embodiment, the transmission hydraulic control system includes a signal line for transmitting control signals to the control terminal of the brake cut-off solenoid valve. In this signal line, a brake cut-off selection switch is connected in series upstream of the control terminal of the brake cut-off solenoid valve. The brake cut-off selection switch can switch between a disconnected position of the cut-off signal line and a connected position of the signal line.

[0014] According to a preferred embodiment, the shift valve is a multi-way directional control valve, which includes multiple outlets, each of which is connected to a different gear clutch.

[0015] According to a preferred embodiment, the transmission hydraulic control system further includes an accumulator disposed between the shift valve and the pump.

[0016] According to a preferred embodiment, the transmission hydraulic control system further includes at least one filter.

[0017] According to a preferred embodiment, the transmission is a mechanical shift type, and the engineering machinery includes a wet drive axle and a fully hydraulic braking system.

[0018] This utility model also relates to an engineering machinery, which has a wet drive axle, a fully hydraulic braking system and a mechanical transmission, wherein the mechanical transmission has a transmission hydraulic control system according to this utility model.

[0019] According to this utility model, by adding a brake cut-off solenoid valve, efficient and safe power interruption can be achieved. This transmission hydraulic control system is particularly suitable for loaders with mechanical shift transmissions selected by mid-range customers. It can automatically cut off the gear during braking without relying on a pressurized air source or an electronically controlled shift valve, thus avoiding wear on the transmission system. Attached Figure Description

[0020] To more clearly illustrate the technical solution of this utility model, the following description is provided in conjunction with the accompanying drawings.

[0021] Figure 1This is a schematic diagram of a prior art transmission hydraulic control system (pneumatic brake stop).

[0022] Figure 2 This is a schematic diagram of the hydraulic control system for the transmission of this utility model.

[0023] List of reference numerals

[0024] 001 Engine

[0025] 002 Pump

[0026] 003 Pressure control valve

[0027] 004 First Filter

[0028] 005 Shift Valve

[0029] 006 Accumulator

[0030] 007 Pneumatic control valve

[0031] 008 First Clutch

[0032] 009 Second Clutch

[0033] 010 Third Clutch

[0034] 011 Oil Pan

[0035] 012 Second Filter

[0036] 013 Torque Converter

[0037] 014 Pressure relief valve

[0038] 015 Radiator

[0039] 016 Gas Pipeline

[0040] 017 Brake stop solenoid valve

[0041] 018 Brake Gear Selection Switch

[0042] 019 Signal Line Detailed Implementation

[0043] The hydraulic control system for a transmission for construction machinery, and construction machinery, particularly loaders, according to the present invention will now be described with reference to the accompanying drawings and specific embodiments. However, exemplary embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to make the present invention comprehensive and complete, and to fully convey the concept of exemplary embodiments to those skilled in the art.

[0044] The following uses a loader as an example, combined with... Figure 1 This describes a prior art transmission hydraulic control system. This transmission hydraulic control system has a power cut-off function. The transmission hydraulic control system includes a pump 002 driven by an engine 001, which is connected to a hydraulic fluid reservoir (e.g., transmission oil pan 011) via a second filter 012. The pump 002 can be configured as a gear pump or a vane pump, and its function is to draw in low-pressure fluid (e.g., transmission lubricating oil) from the hydraulic fluid reservoir and convert it into high-pressure fluid with a certain pressure and flow rate, providing a power source for the entire hydraulic control system.

[0045] The outlet of pump 002 is connected to the main oil circuit of the hydraulic transmission system via a first filter 004. The hydraulic transmission system, used for hydraulic drive, includes components such as engine 001 and torque converter 013. A pressure control valve 003 is installed in this main oil circuit to regulate and stabilize the working pressure of the system's hydraulic control lines. The pressure control valve 003 can be designed, for example, to sense the oil pressure via an internal spring, spool valve (or ball valve) structure. When the hydraulic control line pressure exceeds a preset value, the valve core of the pressure control valve 003 moves, diverting some or all of the pressurized oil back to the low-pressure side (torque converter 013), thereby limiting the pressure of the system's hydraulic control lines within a set range. This protects system components (such as clutch plates and seals) from damage due to excessive pressure and also ensures stable oil pressure required for gear shifting. The main oil circuit also includes a pressure relief valve 014, which limits the pressure in the main oil circuit. A radiator 015 for cooling the transmission hydraulic oil is also installed in the main oil circuit.

[0046] The outlet of pump 002 is connected to a hydraulic control line via a first filter 004, and then to a shift valve 005 via the same hydraulic control line. The shift valve 005 is used to precisely control the flow of hydraulic oil to a specific clutch group to achieve gear shifting. The shift valve 005 is a multi-way directional control valve and includes multiple outlets, each connected to the inlet of a different gear clutch 008-010. The position of the valve spool of the shift valve 005 is typically controlled by the driver via the gear shift lever. The position of the valve spool of the shift valve 005 determines which clutch inlet the pressurized oil is directed to, thus achieving gear selection.

[0047] When shift valve 005 directs pressurized oil to the inlet of one of the clutches (such as the 1 / 3 clutch), the pressurized oil enters the working chamber of that clutch, engaging it and rigidly connecting the transmission input shaft (power source) to the corresponding transmission mechanism, thus transmitting power. Simultaneously, the oil circuits of other unselected clutches are connected to the drain port (oil pan 011) through shift valve 005, disengaging the clutches and causing the transmission mechanism to lose its power transmission capability.

[0048] The diagram illustrates three clutches: clutch 008 (R clutch), clutch 009 (1 / 3 clutch), and clutch 010 (2 / 4 clutch). These clutches are typically located inside the transmission housing and are associated with corresponding gear sets. For example, clutch 008 (R clutch) controls the engagement and disengagement of reverse gear. Clutch 009 (1 / 3 clutch) controls the engagement and disengagement of first and third gear. Clutch 010 (2 / 4 clutch) controls the engagement and disengagement of second and fourth gear.

[0049] An accumulator 006 is installed upstream of and adjacent to the shift valve 005. The accumulator 006 is connected to the inlet of the shift valve 005 via an oil circuit. The function of the accumulator 006 is to absorb oil pressure fluctuations during shifting, reduce shifting shock, and release stored energy when needed by the system (such as during rapid shifting or when the oil pump 002 is temporarily insufficient), providing instantaneous supplemental oil pressure to the clutch, achieving smoother and faster clutch engagement and disengagement, thereby improving shifting quality. The two filters 004 and 012 remove metal shavings, dust, colloids, and other impurities from the oil, maintaining oil cleanliness and preventing impurities from clogging small oil passages and damaging precision valves and seals, thus protecting system components and extending system lifespan.

[0050] A pneumatic brake valve 007 is connected between the accumulator 006 and the first filter 004. The pneumatic brake valve 007 controls the on / off state of the hydraulic control line. The air interface of this pneumatic brake valve 007 is connected to a pressurized air source (not shown) via a gas pipe 016. Pressurized air from the pressurized air source operates the pneumatic brake valve 007, thereby cutting off the hydraulic control line and thus cutting off power transmission during braking. The pressurized air source is typically located at the front end of the braking system or in a separate air tank; its function is to provide a stable supply of compressed air to the entire system as an energy transfer medium.

[0051] During operation, engine 001 drives pump 002 to generate pressurized oil; this pressurized oil is supplied to accumulator 006 and shift valve 005. Based on driver operation or control unit commands, shift valve 005 is positioned in the desired gear. Shift valve 005 directs pressurized oil to the target clutch and depressurizes other clutches. The target clutch piston engages under pressure, and power flow is connected. Under normal driving conditions, pneumatic brake valve 007 is in the open position, the hydraulic control line remains connected, and transmission pressurized oil flows smoothly into the clutches, enabling gear engagement and power transmission. When the driver depresses the brake pedal or wishes to brake based on other driver assistance commands, gas from the pressurized air source switches pneumatic brake valve 007 to the open position, thereby cutting off the hydraulic control line. The pressurized oil in the clutches is rapidly released, thus disengaging the transmission and cutting off power. While this design effectively improves the lifespan of the transmission system, its reliance on a pressurized air source limits its application in systems without a pneumatic air source (such as wet axle fully hydraulic braking systems).

[0052] The following combination Figure 2 This invention provides a detailed description of the specific implementation of the transmission hydraulic control system. The same reference numerals denote the same or functionally identical components.

[0053] The transmission hydraulic control system and Figure 1 Similarly, it includes a pump (not shown), a first filter (not shown), a second filter (not shown), an accumulator 006, a shift valve 005, and corresponding hydraulic lines.

[0054] Unlike existing technologies, a brake cut-off solenoid valve 017 is installed in the hydraulic line between the shift valve 005 and the pump 002. The hydraulic line leading from the outlet of the pump 002 connects to the shift valve 005 via the brake cut-off solenoid valve 017. The control terminal of the brake cut-off solenoid valve 017 is connected to its controller or directly to the brake signal generator via signal line 019. Based on the control signal received from the signal line 019 via its control terminal, the brake cut-off solenoid valve 017 can switch between an on and off state. In the on state, the brake cut-off solenoid valve 017 connects the hydraulic connection between the shift valve 005 and the pump; in the off state, the brake cut-off solenoid valve 017 disconnects the hydraulic connection between the shift valve 005 and the pump 002.

[0055] Preferably, the brake stop solenoid valve 017 is configured as a two-position three-way solenoid valve. In the OFF state (disconnected), the inlet P of the brake stop solenoid valve 017 is connected to the working port A, and the drain port T is closed. In the OFF state (energized), the inlet of the brake stop solenoid valve 017 is closed, and the working port is connected to the drain port. In this case, the outlet of pump 002 (via filter) is connected to the inlet P of brake stop solenoid valve 017, the working port A of brake stop solenoid valve 017 (via accumulator 006) is connected to the inlet of shift valve 005, and the drain port T of brake stop solenoid valve 017 is connected to a hydraulic fluid reservoir (e.g., oil pan).

[0056] The brake stop solenoid valve 017 can be a newly added solenoid valve in the hydraulic line. In this case, the brake stop solenoid valve 017 can be mounted to the transmission housing via a flange. However, the brake stop solenoid valve 017 can also be integrated into the shift valve 005 to reduce external connections and space occupation. The brake stop solenoid valve 017 has a short response time, therefore the system's full stop response time is also very short.

[0057] In signal line 019, a brake cut-off selector switch (also known as a ramp switch) 018 is connected in series upstream of the control terminal of the brake cut-off solenoid valve 017. This brake cut-off selector switch 018 can switch between the disconnected position of signal line 019 and the connected position of signal line 019. When the brake cut-off selector switch 018 is in the connected position, signal line 019 is connected and transmits a control signal to the brake cut-off solenoid valve 017. When the brake cut-off selector switch 018 is in the disconnected position, signal line 019 is disconnected and the brake cut-off solenoid valve 017 remains connected. This is particularly important for ramp operations: for example, when a loader is loading or unloading uphill or downhill, keeping the brake cut-off selector switch 018 in the disconnected position can prevent accidental brake failure and subsequent rollover accidents, thus improving operational safety.

[0058] The operating device for the brake gear selector switch 018 can be mounted on a panel that can be operated by the driver. For example, the operating device for the brake gear selector switch 018 can be designed as a knob and located on the dashboard of the loader cab. This knob can be labeled "ramp mode" on its surface.

[0059] The working principle of the transmission hydraulic control system of this utility model is described below.

[0060] Under normal driving conditions, the brake cut-off solenoid valve 017 is not energized and is in the energized state. Transmission pressurized oil flows from the outlet of oil pump 002, passes through the brake cut-off solenoid valve 017 and accumulator 006, and enters shift valve 005. At this time, shift valve 005 controls the clutch according to the gear position command. This enables normal engagement of forward, reverse, or gear shifting, allowing power to be transmitted to the drive wheels.

[0061] When the driver depresses the brake pedal or a braking command is received from the control unit, the brake light switch is activated, and a control signal is sent to signal line 019. If the brake cut-off selector switch 018 is in the ON position (i.e., the hill start function is not activated), the control signal is further transmitted to the control terminal of the brake cut-off solenoid valve 017, energizing the solenoid valve 017 to switch to the OFF state, thereby cutting off the transmission hydraulic control line. Simultaneously, the pressurized oil in the clutch is rapidly discharged to the oil tank through the drain port of the brake cut-off solenoid valve 017, causing the clutch to disengage, the transmission to cut off, and power to be completely interrupted, thus protecting the transmission system from braking shock.

[0062] When the brake cut-off selector switch 018 is in the ON position, the aforementioned brake cut-off function operates normally. When the brake cut-off selector switch 018 is in the OFF position, the signal line 019 is disconnected. Therefore, the brake cut-off solenoid valve 017 is always de-energized and remains ON, ensuring the transmission hydraulic control line remains connected and normal gear engagement and power transmission are maintained.

[0063] The advantages of the above solutions are:

[0064] It has a simple structure, low cost, and is easy to retrofit onto existing mechanical transmissions.

[0065] By using the brake cut-off solenoid valve 017 to directly control the oil circuit, the risk of hydraulic oil and transmission oil mixing is avoided, thus improving system reliability and lifespan.

[0066] The introduction of ramp switches enhances safety, especially when operating on sloping terrain, preventing accidental rollover.

[0067] The implementation of this utility model is not limited to the above description. Those skilled in the art can adjust the installation position of the brake stop solenoid valve (such as setting it independently or integrating it), the type of brake stop selection switch, or the details of the oil circuit according to actual needs, but all of these fall within the protection scope of this utility model.

Claims

1. A hydraulic control system for a transmission in engineering machinery, characterized in that: The transmission hydraulic control system includes: Pump (002) for providing hydraulic fluid for control purposes; A shift valve (005) hydraulically connected to the pump (002) is used to control the flow direction of hydraulic fluid to control the gear position; A brake cut-off solenoid valve (017) is installed in the hydraulic line between the shift valve (005) and the pump (002); The brake cut-off solenoid valve (017) can switch between an on state and an off state. In the on state, the brake cut-off solenoid valve (017) connects the hydraulic connection between the shift valve (005) and the pump (002), while in the off state, the brake cut-off solenoid valve (017) disconnects the hydraulic connection between the shift valve (005) and the pump (002).

2. The transmission hydraulic control system according to claim 1, characterized in that: The brake stop solenoid valve (017) is configured as a two-position three-way solenoid valve.

3. The transmission hydraulic control system according to claim 2, characterized in that: When the brake stop solenoid valve (017) is not energized, it is in the energized state, wherein the oil inlet and the working port are connected and the oil drain port is closed; when the brake stop solenoid valve (017) is energized, it is in the de-energized state, wherein the oil inlet is closed and the working port and the oil drain port are connected.

4. The transmission hydraulic control system according to claim 3, characterized in that: The outlet of the pump (002) is connected to the inlet (P) of the brake stop solenoid valve (017), the working port (A) of the brake stop solenoid valve (017) is connected to the inlet of the shift valve (005), and the drain port (T) of the brake stop solenoid valve (017) is connected to the low-pressure oil tank (011).

5. The transmission hydraulic control system according to claim 1, characterized in that: The transmission hydraulic control system includes a signal line (019) for transmitting control signals to the control terminal of the brake cut-off solenoid valve (017). In the signal line (019), a brake cut-off selection switch (018) is connected in series upstream of the control terminal of the brake cut-off solenoid valve (017). The brake cut-off selection switch (018) can switch between the disconnected position of the cut-off signal line (019) and the connected position of the connected signal line (019).

6. The transmission hydraulic control system according to claim 1, characterized in that: The shift valve (005) is a multi-way directional control valve, which includes multiple outlets, each of which is connected to a different gear clutch.

7. The transmission hydraulic control system according to claim 1, characterized in that: The transmission hydraulic control system also includes an accumulator (006) disposed between the shift valve (005) and the pump (002).

8. The transmission hydraulic control system according to claim 1, characterized in that: The transmission hydraulic control system also includes at least one filter.

9. The transmission hydraulic control system according to claim 1, characterized in that: The transmission is a mechanical shift type, and the engineering machinery includes a wet drive axle and a fully hydraulic braking system.

10. An engineering machinery, comprising a wet drive axle, a fully hydraulic braking system, and a mechanical transmission, characterized in that, The mechanical transmission has a transmission hydraulic control system according to any one of claims 1-9.

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