Emergency oil supply switching valve, oil supply system and truck crane

Abstract

The present invention relates to an emergency oil supply switching valve. This valve is designed to address the problem that existing flow-type emergency oil supply switching valves cannot be used in conjunction with high-pressure variable main pumps. The valve, an oil supply system, and a truck crane are provided. Port P1 in the emergency oil supply switching valve is simultaneously connected to the hydraulically controlled left end of a reversing valve and the front end of a first damping orifice. The spring chamber at the right end of the reversing valve is interconnected with the rear end of the first damping orifice and port T. When the reversing valve is in the left position, port P1 is connected to port A via the left oil circuit of the reversing valve, and port P2 is connected to port T via the left oil circuit of the reversing valve and a flow detection valve. When the reversing valve is in the right position, port P2 is connected to port A via the right oil circuit of the reversing valve, and the oil circuits from ports P1 and P2 to the oil inlet of the flow detection valve are both blocked. The emergency oil supply switching valve of the present invention is a pressure-type valve that switches based on pressure without requiring flow. The rear axle of the truck crane is in a high-pressure, low-flow standby state when not steering, reducing overall machine energy consumption while ensuring safety.

Description

Technical Field

[0001] The present invention relates to a steering hydraulic system of a truck crane, and more particularly to an emergency oil supply switching valve, an oil supply system and a truck crane. Background Art

[0002] All-terrain cranes feature multi-axle steering, with independent steering currently employed for the front axles (axles 1 and 2) and rear axles (n axles, where n ≥ 2). Furthermore, to ensure driving safety, the front and rear axle hydraulic systems each require an emergency pump in addition to the main pump. The main and emergency pumps are connected to the steering circuit via an emergency oil supply switching valve. When the main pump is operating normally, it supplies oil to the steering circuit via the emergency oil supply switching valve. If the main pump fails and cannot supply oil, the emergency oil supply switching valve reverses direction, allowing the emergency pump to supply oil to the steering circuit, ensuring sufficient oil for steering.

[0003] The emergency oil supply switching valve currently used in the industry is a flow type emergency oil supply switching valve. Figure 1 As shown, it includes a main pump, an emergency pump, and an emergency oil supply switching valve. The emergency oil supply switching valve includes a reversing valve, a flow detection valve, a damping orifice, and a first one-way valve.

[0004] The main pump is a fixed displacement pump with a constant displacement. The output flow Q is only related to the engine speed. When the output flow Q of the main pump passes through the damping orifice and the first one-way valve, the pressures p1 and p2 at the front and rear ends of the damping orifice are as follows:

[0005] Q = C × A × sqrt(p1-p2)

[0006] Q——output flow of main pump;

[0007] C - flow coefficient, the ratio of the flow through the damping orifice to the flow through the reversing valve;

[0008] A——the flow area of the damping hole;

[0009] p1——pressure at the front end of damping hole;

[0010] p2——pressure at the rear end of the damping hole;

[0011] The pressure difference across the damping orifice can be calculated when the main pump outputs flow rate Q. Pressure p1 acts on the left end of the reversing valve, while pressure p2 and the reversing valve spring force F1 act together on the right end of the reversing valve. When the force on the left end is greater than the force on the right end, reversing valve 1 switches direction, allowing oil to be supplied by the main pump.

[0012] Therefore, in order to make the reversing valve reverse and work in the left position, the flow rate Q output by the main pump must be greater than a certain value, which is usually the output flow rate of the main pump when the engine is idling (usually greater than 18L / min).

[0013] When main pump 2 is operating normally, after reversing valve 51, the output flow of main pump 2 flows from port A to the steering circuit via the left oil path of reversing valve 51. The output flow of emergency pump 3 flows back to the fuel tank via the left oil path of reversing valve 51 and flow detection valve 56. Due to the damping effect of the main valve core of flow detection valve 56, the pressure generated at the pressure control end of flow detection valve 56 overcomes the spring force, causing flow detection valve 56 to reverse direction, disconnecting the trigger switch from the valve stem of the flow detection valve, and deactivating the alarm device.

[0014] If the main pump is damaged and cannot output the rated flow Q, the pressure difference at both ends of the damping hole 57 cannot overcome the elastic force of the spring cavity end of the reversing valve. The reversing valve operates in the right position under the action of the spring. The flow output by the emergency pump 3 passes through the right oil circuit of the reversing valve 51 from port A to the steering circuit, keeping the steering system running. At the same time, the flow of the emergency pump 3 through the flow detection valve is cut off, and there is no longer pressure at the hydraulic control end of the flow detection valve. The valve stem of the flow detection valve is reset under the action of the spring force, the trigger switch is closed, and the alarm device works.

[0015] Since the front axle's steering hydraulic system is equipped with a steering gear, with the P and T positions connected in the neutral position, the front axle's steering hydraulic system generally uses a fixed-displacement main pump and a flow-type emergency steering valve. However, since the rear axle's steering hydraulic system lacks a steering gear, a high-pressure variable-displacement main pump is typically used to reduce system heat. This type of pump only outputs a small flow rate (less than 3L / min) when in standby mode, making the flow-type emergency steering valve inoperable. Summary of the Invention

[0016] The technical problem to be solved by the present invention is that the flow-type emergency oil supply switching valve in the existing rear axle steering hydraulic system of a truck crane cannot be used in conjunction with a high-pressure variable main pump. An emergency oil supply switching valve, an oil supply system and a truck crane are provided, so that a constant-pressure variable main pump and an emergency oil supply switching valve can be used in the rear axle steering hydraulic system of the truck crane, thereby achieving energy saving while ensuring safety.

[0017] The technical solution for achieving the purpose of the present invention is as follows: an emergency oil supply switching valve is provided, having a P1 port, a P2 port, an A port and a T port, and includes a reversing valve, a flow detection valve, and a first damping hole; it is characterized in that the P1 port is simultaneously connected to the hydraulic control left end of the reversing valve and the front end of the first damping hole, and the right end spring chamber of the reversing valve is connected to the rear end of the first damping hole and the T port. When the reversing valve is in the left position, the P1 port is connected to the A port through the left position oil circuit of the reversing valve, and the P2 port is connected to the T port through the left position oil circuit of the reversing valve and the flow detection valve; when the reversing valve is in the right position, the P2 port is connected to the A port through the right position oil circuit of the reversing valve, and the oil circuits from the P1 port and the P2 port to the oil inlet end of the flow detection valve are both cut off.

[0018] In the present invention, when the pressure at port P1 is greater than a predetermined value, the reversing valve is in the left position, the oil from port P1 is output from port A, and the oil from port P2 is output through port T of the flow detection valve; when the oil pressure at port P1 drops (for example, the corresponding pump fails) and is lower than a predetermined value, the reversing valve is reversed, and the oil from port P2 is output from port A, replacing the oil from port P1, so that the oil from port A is switched from the oil from port P1 to the oil from port P2, and no oil flows into the oil inlet end of the flow detection valve, and the flow detection valve is also reversed accordingly. The valve stem reversing action of the flow detection valve can be used to trigger a signal device, limiting the oil source of the emergency oil supply switching valve to be switched. The emergency oil supply switching valve in the present invention does not rely on the flow rate flowing into port P1 when supplying oil at port P1, but is based on the pressure of port P1, so it is a pressure-type emergency oil supply switching valve.

[0019] The emergency oil supply switching valve in this invention is a pressure-type emergency oil supply switching valve. Its switching action is independent of the flow rate flowing into port P1, but rather the pressure at port P1. The switching action is determined when the pressure at port P1 falls below a predetermined value. This pressure-based switching, with no flow rate requirements, allows the valve to be used in hydraulic systems with low flow rates. The low-flow standby mode reduces energy consumption.

[0020] The emergency oil supply switching valve further includes a second damping orifice, the front end of which communicates with both the right spring chamber of the reversing valve and the rear end of the first damping orifice. The rear end of the second damping orifice communicates with port T. The second damping orifice increases the pressure at the spring chamber end of the reversing valve, thereby reducing the stiffness of the spring within the spring chamber.

[0021] The emergency oil supply switching valve also includes a filter, whose oil inlet is connected to port P1 and whose oil outlet is connected to both the front end of the first damping orifice and the left hydraulic control end of the reversing valve. The filter filters the oil to prevent impurities in the oil from entering the damping orifice and clogging it, thereby affecting its function.

[0022] The emergency oil supply switching valve further includes a one-way valve, through which the left and right oil circuits of the reversing valve are connected to port A. The one-way valve prevents the oil in port A from flowing in the opposite direction and causing hydraulic shock.

[0023] In the above-mentioned emergency oil supply switching valve, the flow detection valve is a two-position, two-way valve, whose hydraulic control end is connected to the oil inlet end, and the spring chamber end is connected to the oil outlet end. A damping oil circuit is provided on the main valve core, which connects the oil inlet end and the oil outlet end. When no oil flows through the flow detection valve, the pressure at the hydraulic control end and the spring chamber end of the flow detection valve are the same, and the valve stem moves toward the hydraulic control end under the action of the spring. When there is sufficient flow through the flow detection valve, a pressure difference is generated at both ends of the flow detection valve, overcoming the spring force to push the valve stem to reverse. Therefore, the movement of the valve stem of the flow detection valve corresponds to the flow rate passing through the flow detection valve, and it can therefore be used as an alarm triggering device, that is, when the oil at port P2 is switched to be output from port A, the corresponding device generates a corresponding warning message.

[0024] The technical solution for achieving the purpose of the present invention is as follows: an oil supply system is provided for supplying oil to a hydraulic system, including a hydraulic oil tank, a main pump and an emergency pump connected to the hydraulic oil tank, and is characterized in that it also includes the aforementioned emergency oil supply switching valve, the P1 port of the emergency oil supply switching valve is connected to the main pump, the P2 port is connected to the emergency pump, the T port is connected to the hydraulic oil tank, and the A port is the pressure oil output port for supplying oil to the oil receiving circuit of the hydraulic system.

[0025] The above oil supply system further includes an alarm device, and a trigger switch of the alarm device is linked to the valve stem of the flow detection valve.

[0026] In the above oil supply system, the main pump is a constant-pressure variable displacement pump. Its displacement can be adjusted according to demand. When high flow is not required, the hydraulic oil flow rate it outputs is low. This high-pressure, low-flow mode generates minimal energy consumption, making it suitable for hydraulic systems that require long periods of high-pressure, low-flow standby.

[0027] The present invention achieves its objectives by providing a mobile crane comprising a rear-axle steering hydraulic system, characterized in that the rear-axle steering hydraulic system includes the aforementioned oil supply system, and port A of the emergency oil supply switching valve is connected to the steering circuit of the rear-axle steering hydraulic system. Rear-axle steering on a mobile crane is typically only used at work sites or for fine-tuning the crane's operating position, and its usage time is relatively short. Therefore, the rear-axle steering hydraulic system is equipped with the oil supply system of the present invention, along with a constant-pressure variable displacement pump that operates at a low displacement during non-steering periods, reducing energy consumption. Furthermore, a pressure-type emergency oil supply switching valve ensures safety by switching oil supply to the emergency pump in the event of a main pump failure under low flow conditions.

[0028] Compared with the prior art, the present invention provides a pressure-type emergency oil supply switching valve, which can be used in the rear axle steering hydraulic system of a truck crane to achieve a high-pressure, low-flow standby state of the rear axle steering hydraulic system during non-steering operations, thereby reducing the energy consumption of the entire machine. At the same time, when the main pump fails and cannot supply oil, the oil supply can be switched to the emergency pump to ensure safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a schematic diagram of a rear axle steering hydraulic system including an existing flow-type emergency oil supply switching valve.

[0030] Figure 2 It is a schematic diagram of the principle of the pressure-type emergency oil supply switching valve in the present invention.

[0031] Figure 3 The invention relates to a rear axle steering hydraulic system of a truck crane.

[0032] Parts names and serial numbers in the figure:

[0033] Hydraulic oil tank 1, main pump 2, emergency pump 3, steering circuit 4, emergency oil supply switching valve 5, reversing valve 51, first damping orifice 52, second damping orifice 53, one-way valve 54, filter 55, flow detection valve 56, damping orifice 57, alarm device 6, trigger switch 61. DETAILED DESCRIPTION

[0034] The specific implementation scheme is described below with reference to the accompanying drawings.

[0035] like Figure 2 As shown, the emergency oil supply switching valve 5 in the present invention has a P1 port, a P2 port, an A port and a T port, and includes a reversing valve 51, a flow detection valve 56, a first damping hole 52, a second damping hole 53, a filter 55, a one-way valve 54, etc.

[0036] The oil inlet of the filter 54 is connected to port P1. The oil outlet of the filter 54 is connected to both the front end of the first damping orifice 52 and the hydraulically controlled left end of the reversing valve 51. The front end of the second damping orifice 53 is connected to both the right spring chamber of the reversing valve 51 and the rear end of the first damping orifice 52. The rear end of the second damping orifice 53 is connected to port T. The left and right oil circuits of the reversing valve 51 are both connected to port A through a one-way valve 54.

[0037] When the reversing valve 51 is in the left position, port P1 is connected to port A through the left oil circuit of the reversing valve 51 and the one-way valve 54, and port P2 is connected to port T through the left oil circuit of the reversing valve 51 and the flow detection valve 56; when the reversing valve 51 is in the right position, port P2 is connected to port A through the right oil circuit of the reversing valve 51 and the one-way valve 54, and the oil circuits from port P1 and port P2 to the oil inlet end of the flow detection valve 56 are both cut off.

[0038] The flow detection valve 56 is a two-position, two-way valve. Its hydraulic control end is connected to the oil inlet, and its spring chamber end is connected to the oil outlet. A damping oil circuit is provided on its main valve core, connecting the oil inlet and oil outlet. When oil passes through the flow detection valve 56, a pressure differential is generated between the oil inlet and oil outlet due to the damping oil circuit. This differential pressure also occurs between the hydraulic control end and the spring chamber. When this pressure differential exceeds the spring chamber's elastic force, the valve stem shifts in the direction of the spring chamber. When no oil flows through the flow detection valve, the pressure at the hydraulic control end and the spring chamber end of the flow detection valve is the same, and the valve stem moves toward the hydraulic control end under the action of the spring. Therefore, the movement of the flow detection valve stem corresponds to whether oil is flowing through the flow detection valve. This serves as an alarm triggering device, causing the corresponding device to generate a corresponding warning message when oil at port P2 is switched to be output from port A.

[0039] Figure 3 The figure shows the rear axle steering hydraulic system of the truck crane. Figure 3 As shown, the rear axle steering hydraulic system of the truck crane includes an oil supply system and a steering circuit 4. The oil supply system comprises a hydraulic oil tank 1, a main pump 2 and an emergency pump 3 connected to the hydraulic oil tank 1, the aforementioned emergency oil supply switching valve 5, and an alarm device 6. Port P1 of the emergency oil supply switching valve 5 is connected to the main pump 2, port P2 to the emergency pump 3, port T to the hydraulic oil tank 1, and port A is the pressure oil output port, connected to the steering circuit 4. Alarm device 6 is a fault warning light, the trigger switch 61 of which is linked to the valve stem of the flow detection valve 56. The main pump 2 is a constant-pressure variable pump, and its displacement can be adjusted according to demand. When high flow is not required, the hydraulic oil output flow is low. This high-pressure, low-flow mode generates minimal energy consumption, making it suitable for hydraulic systems that require long periods of high-pressure, low-flow standby, thus achieving energy savings.

[0040] In this embodiment, when the rear axle steering hydraulic system of a truck crane is in a standby state and the main pump is operating normally, the displacement of main pump 2 is adjusted to its minimum, placing the entire rear axle steering hydraulic system in a high-pressure, low-flow overflow state. In this embodiment, the first damping orifice 52 and the second damping orifice 53 form a damping network. The pressurized oil output by main pump 2 flows through the first damping orifice 52, acts on the spring chamber end (right end) of the reversing valve 51, and then returns to port T through the second damping orifice 53. Since the flow Q through the first damping orifice 52 is equal to the flow Q through the second damping orifice 53, the first damping orifice 52 and the second damping orifice 53 are set to the same size (for convenience of calculation, the apertures are taken to be the same value, and different apertures can be taken in actual implementation). According to the formula of the small-hole throttling principle, the pressure relationship between the front and rear ends of the first damping orifice 52 is calculated as follows: p1=2*p2, where p1 is the pressure at the front end of the first damping orifice 52, and p2 is the pressure at the rear end of the first damping orifice 52; the spring at the spring chamber end of the reversing valve 51 can be selected with a smaller specification of stiffness. As long as the hydraulic oil pressure p1 output by the main pump 2 overcomes the action of p2 and the spring at the spring chamber end of the reversing valve 51, the reversing valve 51 can be switched to the left position without the main pump 2 outputting a larger flow rate. When reversing valve 51 is in the left position, pressure oil from main pump 2 at port P1 is delivered to steering circuit 4 via the left oil path of reversing valve 51 and check valve 54 from port A, placing the steering hydraulic actuator in steering circuit 4 in a steering standby state or performing a steering action. During steering standby, main pump 2 can reduce its displacement to minimize flow, thereby reducing energy consumption during standby.

[0041] When main pump 2 is operating normally, reversing valve 51 switches to the left position. Port P2 connects to the oil inlet of flow detection valve 56 through the left-position oil circuit of reversing valve 51. Oil then flows through flow detection valve 56 to port T and returns to hydraulic oil tank 1. As oil passes through flow detection valve 56, a pressure differential is generated between the oil inlet and outlet of flow detection valve 56 due to the action of the damping oil circuit. This differential also creates a pressure differential between the hydraulic control end of the flow detection valve and the spring chamber. When this pressure differential exceeds the spring chamber's elastic force, the valve stem shifts in the direction of the spring chamber, causing trigger switch 61 to be disconnected, and the fault warning light goes off.

[0042] When the main pump 2 fails and cannot output the pressure oil required for steering, that is, when the pre-valve pressure p1 of the first damping orifice 52 cannot overcome the pressure p2 at the spring chamber end of the reversing valve and the elastic force of the spring, the reversing valve 51 switches to the right position, and port P2 is connected to port A through the right oil circuit of the reversing valve 51 and the one-way valve 54. That is, the oil output by the emergency pump 3 is supplied to the steering circuit 4 through the right oil circuit of the reversing valve 51, the one-way valve 54, and port A, ensuring the steering oil supply of the steering circuit 54. Since the reversing valve 51 is switched to the right position, the oil circuit leading to the flow detection valve 56 is cut off, and no oil flows through the flow detection valve 56. The pressure at the hydraulic end of the flow detection valve 56 is the same as that at the spring chamber end, and the valve stem moves toward the hydraulic end under the action of the spring. The valve stem of the flow detection valve 56 moves to drive the trigger switch 61 to close, and the circuit of the fault warning light is connected and illuminated, reminding the driver that the hydraulic oil used in the rear axle steering hydraulic system comes from the emergency pump, and the main pump needs to be inspected and repaired as necessary.

[0043] In the present invention, the second damping orifice 53 can be eliminated, while maintaining the stiffness of the spring in the spring chamber of the reversing valve 51. When the main pump 2 is operating normally, the reversing valve 51 operates in the left position, and its valve stem moves to the right. The valve stem compresses the spring in the spring chamber by a predetermined distance before contacting the valve body to prevent the spring from being crushed. If the main pump 2 fails and the force generated by the pressurized oil it outputs at the hydraulically controlled left end of the reversing valve 51 is insufficient to overcome the elastic force of the spring, the valve stem moves to the left under the action of the spring force and operates in the right position, switching the oil supply from the main pump 2 to the emergency pump 3.

[0044] The emergency oil supply switching valve in this invention is a pressure-type emergency oil supply switching valve. Its switching action is not determined by the flow rate flowing into port P1, but by the pressure at port P1. The switching action is activated when the pressure at port P1 falls below a predetermined value. This pressure-based switching mechanism eliminates flow rate requirements, making it suitable for use in crane rear axle steering hydraulic systems. Working in conjunction with a constant-pressure variable pump (main pump), it achieves both energy savings and safety.

Claims

1. An emergency oil supply switching valve, having ports P1, P2, A, and T, and including a reversing valve, a flow detection valve, and a first damping orifice; the reversing valve includes a hydraulically controlled left and right spring chambers; characterized in that: The P1 port is simultaneously connected to the hydraulic control left end of the reversing valve and the front end of the first damping hole, and the spring chamber at the right end of the reversing valve is connected to the rear end of the first damping hole and the T port. When the reversing valve is in the left position, the P1 port is connected to the A port via the left position oil circuit of the reversing valve, and the P2 port is connected to the T port via the left position oil circuit of the reversing valve and the flow detection valve; when the reversing valve is in the right position, the P2 port is connected to the A port via the right position oil circuit of the reversing valve, and the oil circuits from the P1 port and the P2 port to the oil inlet end of the flow detection valve are both cut off; the flow detection valve is a two-position, two-way valve, the hydraulic control end of the flow detection valve is connected to the oil inlet end of the flow detection valve, and the spring chamber end of the flow detection valve is connected to the oil outlet end of the flow detection valve; When the incoming oil pressure at port P1 is greater than a preset value, the reversing valve is in the left position, the incoming oil at port P1 is output from port A, and the incoming oil at port P2 is output from port T through the flow detection valve; when the incoming oil pressure at port P1 drops below a preset value, the reversing valve reverses, and the incoming oil at port P2 is output from port A, replacing the incoming oil at port P1.

2. The emergency oil supply switching valve according to claim 1, characterized in that: It also includes a second damping hole, the front end of which is communicated with the right end spring chamber of the reversing valve and the rear end of the first damping hole, and the rear end of the second damping hole is communicated with the T port.

3. The emergency oil supply switching valve according to claim 1 or 2, characterized in that: It also includes a filter, the oil inlet end of the filter is connected to the P1 port, and the oil outlet end is simultaneously connected to the front end of the first damping hole and the hydraulic control left end of the reversing valve.

4. The emergency oil supply switching valve according to claim 1 or 2, characterized in that: It also includes a one-way valve, and the left oil circuit and the right oil circuit of the reversing valve are both connected to the A port through the one-way valve.

5. An oil supply system for supplying oil to a hydraulic system, comprising a hydraulic oil tank, a main pump connected to the hydraulic oil tank, and an emergency pump, characterized in that: It also includes the emergency oil supply switching valve according to any one of claims 1 to 4, wherein the P1 port of the emergency oil supply switching valve is connected to the main pump, the P2 port is connected to the emergency pump, and the A port is used to connect to the oil receiving circuit.

6. The oil supply system according to claim 5, characterized in that: It also includes an alarm device, and a trigger switch of the alarm device is linked to the valve stem of the flow detection valve.

7. The oil supply system according to claim 5 or 6, characterized in that: The main pump is a constant pressure variable displacement pump.

8. A truck crane, including a rear axle steering hydraulic system, characterized in that The rear axle steering hydraulic system includes the oil supply system according to any one of claims 5 to 7, and the port A of the emergency oil supply switching valve is connected to the steering circuit of the rear axle steering hydraulic system.

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