Steering hydraulic system of loading machine, control method and loading machine

Abstract

The invention belongs to the technical field of hydraulic control, and particularly relates to a loader steering hydraulic system, a control method and a loader. Comprising a steering gear, a steering cylinder, a steering pump connected with an oil tank, a flow amplifying valve, a pilot oil source valve, a stop valve and a proportional electromagnetic valve, an oil outlet of the steering pump is connected with a port P of the flow amplifying valve and a port P of the pilot oil source valve; a port L and a port R of the steering gear are respectively connected with a port a and a port b of the flow amplification valve, and a port L and a port R of the proportional electromagnetic valve are respectively connected with a port a and a port b of the flow amplification valve. According to the invention, the steering cylinder can still be controlled when the steering gear is blocked, so that the purpose of ensuring the steering reliability and safety of the loader is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic control, and in particular relates to a loader steering hydraulic system, a control method and a loader. Background Art

[0002] As a traditional engineering machinery, loaders are widely used in the construction, forestry and other industries. In the prior art, most loader steering hydraulic systems use steering gears for steering, and the steering gears often have malfunctions such as jamming during operation, which affects the reliability and safety of the loader steering. Summary of the invention

[0003] The object of the present invention is to provide a loader steering hydraulic system, control method and loader, which can control the steering cylinder when the steering gear is stuck by setting a pilot oil source valve, a cut-off valve and a proportional solenoid valve, so as to ensure the steering reliability and safety of the loader.

[0004] The present invention adopts the following technical solution to solve the problem: In a first aspect, the present invention provides a steering hydraulic system for a loader, comprising a steering gear, a steering cylinder, and a steering pump connected to an oil tank, characterized in that it also comprises a flow amplification valve, a pilot oil source valve, a cut-off valve, and a proportional solenoid valve; the oil outlet of the steering pump is connected to both the P port of the flow amplification valve and the P port of the pilot oil source valve; the P port of the cut-off valve is connected to the U port of the pilot oil source valve, the A port and the B port of the cut-off valve are respectively connected to the P port of the proportional solenoid valve and the P port of the steering gear, the L port and the R port of the steering gear are respectively connected to the a port and the b port of the flow amplification valve, the T port of the steering gear is connected to the oil tank, the L port and the R port of the proportional solenoid valve are respectively connected to the a port and the b port of the flow amplification valve, and the T port of the flow amplification valve is connected to the oil tank; When the a port of the flow amplifying valve is acted upon by hydraulic oil, the A port of the flow amplifying valve outputs hydraulic oil to the steering cylinder to achieve left steering; when the b port of the flow amplifying valve is acted upon by hydraulic oil, the B port of the flow amplifying valve outputs hydraulic oil to the steering cylinder to achieve right steering; the cut-off valve includes a left position and a right position, and when the cut-off valve is in the right position, the P port of the cut-off valve is connected to its B port; when the cut-off valve is in the left position, the P port of the cut-off valve is connected to both its A port and its B port.

[0005] Optionally, the switching of the cut-off valve is controlled by a solenoid valve.

[0006] Optionally, the proportional solenoid valve includes a left position, a middle position and a right position; the position change of the proportional solenoid valve is controlled by the solenoid valve; when the proportional solenoid valve is in the left position, the P port and the L port of the proportional solenoid valve are connected, and the R port and the T port of the proportional solenoid valve are connected; when the proportional solenoid valve is in the middle position, the P port of the proportional solenoid valve is cut off; when the proportional solenoid valve is in the right position, the P port and the R port of the proportional solenoid valve are connected, and the L port and the T port of the proportional solenoid valve are connected.

[0007] Optionally, the flow amplification valve includes a diverter valve core and a flow amplification valve core; the diverter valve core includes a first oil port, a second oil port and a third oil port, and the flow amplification valve core includes a first oil inlet port, a first oil return port, a first working oil port and a second working oil port; The first oil port of the diverter valve core is connected to the steering pump, the second oil port is connected to the first oil inlet port of the flow amplification valve core, and the third oil port is used to connect to other external systems; the diverter valve core includes a left position, a middle position and a right position; The flow amplification valve core has a first oil return port connected to the oil tank, a first working oil port connected to port A of the flow amplification valve through a first oil circuit, and a second working oil port connected to port B of the flow amplification valve through a second oil circuit; When the diverter valve core is in the left position, the first oil port and the second oil port of the diverter valve core are connected. The diverter valve core is in the middle position, and the first oil port of the diverter valve core is connected to the second oil port and the third oil port; a damper is provided on the oil path between the first oil port and the third oil port; When the diverter valve core is in the right position, the first oil port of the diverter valve core is connected to the second oil port and the third oil port; a damper is provided on the oil path between the first oil port and the second oil port.

[0008] Optionally, it also includes: A shuttle valve, wherein two oil inlets are respectively connected to the first oil circuit and the second oil circuit; an oil outlet of the shuttle valve is connected to the oil return circuit between the first oil return port and the oil tank through a third oil circuit; A relief valve, arranged on the third oil circuit; The left end of the diverter valve core is connected to the third oil circuit and is located upstream of the overflow valve. The left end of the diverter valve core is also provided with a return spring. The right end of the diverter valve core is connected between the second oil port of the diverter valve core and the first oil inlet of the flow amplification valve core.

[0009] Optionally, the flow amplification valve core includes a left position, a middle position and a right position, the left end of the flow amplification valve core is connected to the port a of the flow amplification valve, and the right end of the flow amplification valve core is connected to the port b of the flow amplification valve; When the flow amplification valve core is in the left position, the first oil inlet and the first oil return port of the flow amplification valve core are connected to the first working oil port and the second working oil port respectively; When the flow amplification valve core is in the middle position, the first oil inlet and the first oil return port of the flow amplification valve core are cut off; When the flow amplification valve core is in the right position, the first oil inlet and the first oil return port of the flow amplification valve core are communicated with the second working oil port and the first working oil port respectively.

[0010] Optionally, it also includes: A buffer valve, including a left relief valve, a right relief valve, a left check valve, a right check valve and a control valve; A fourth oil circuit and a fifth oil circuit are connected in parallel between the first oil circuit and the second oil circuit; the left overflow valve and the right overflow valve are arranged on the fourth oil circuit in opposite flow directions, and the left check valve and the right check valve are arranged on the fifth oil circuit in opposite flow directions; the oil inlet of the control valve is connected between the left overflow valve and the right overflow valve, and the oil outlet of the control valve is connected between the left check valve and the right check valve; the left end of the control valve is connected to the connecting oil circuit between the left overflow valve and the left check valve, and the right end of the control valve is connected to the connecting oil circuit between the right overflow valve and the right check valve.

[0011] In a second aspect, the present invention provides a control method for a loader steering hydraulic system, which is based on the loader steering hydraulic system and comprises: In response to a right turn control signal: If the output pressure of the R port of the steering gear is greater than a preset threshold, the P port of the cut-off valve is controlled to be connected only to the B port, and the P port of the proportional solenoid valve is cut off; the hydraulic oil output from the R port of the steering gear acts on the b port of the flow amplification valve, so that the B port of the flow amplification valve outputs the hydraulic oil to the steering cylinder to achieve right steering; If the output pressure of the R port of the steering gear is less than a preset threshold, the P port of the cut-off valve is controlled to be connected to the A port and the B port, and the P port and the R port of the proportional solenoid valve are connected; the R port of the proportional solenoid valve outputs hydraulic oil to act on the b port of the flow amplification valve, so that the B port of the flow amplification valve outputs hydraulic oil to the steering cylinder to achieve right steering; In response to the left turn control signal, If the output pressure of the L port of the steering gear is greater than a preset threshold, the P port of the cut-off valve is controlled to be connected only to the B port, and the P port of the proportional solenoid valve is cut off; the hydraulic oil output from the L port of the steering gear acts on the a port of the flow amplification valve, so that the A port of the flow amplification valve outputs hydraulic oil to the steering cylinder to achieve left steering; If the output pressure of the L port of the steering gear is less than a preset threshold, the P port of the cut-off valve is controlled to be connected to the A port and the B port, and the P port and the L port of the proportional solenoid valve are connected; the L port of the proportional solenoid valve outputs hydraulic oil to act on the a port of the flow amplification valve, so that the A port of the flow amplification valve outputs hydraulic oil to the steering cylinder to achieve right steering.

[0012] Optionally, a pressure sensor 1 is provided at the L port of the steering gear, and a pressure sensor 2 is provided at the R port of the steering gear.

[0013] In a third aspect, the present invention provides a loader, comprising the loader steering hydraulic system.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. Compared with the conventional loader steering hydraulic system, the steering hydraulic system and control method proposed in the present invention, when the steering gear is stuck and fails, the pilot oil source valve can still control the flow amplification valve through the proportional solenoid valve by switching the cut-off valve, so that the hydraulic oil acts on the steering cylinder and realizes steering, thereby improving the reliability and safety of the loader steering hydraulic system.

[0015] 2. The auxiliary valve arranged inside the flow amplification valve of the present invention can relieve pressure to the low-pressure side when the steering load causes high pressure at the oil outlet of the flow amplification valve, so as to effectively reduce the steering impact when the loader suddenly changes direction and improve the steering stability of the loader. At the same time, the shuttle valve cooperates with the overflow valve to change direction through the diverter valve core when high pressure appears at the oil outlet of the flow amplification valve, so as to reduce the oil pressure by returning the oil, and divert the hydraulic oil output by the hydraulic pump to other systems through the third oil port of the diverter valve core to protect the oil circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the structure of the hydraulic system in Example 1.

[0017] Numbers in the figure: 1. Steering pump; 2. Steering gear; 3. Flow amplification valve; 31. Relief valve; 31. Diverter valve core; 33. Flow amplification valve core; 34. Shuttle valve; 35. Buffer valve; 351. Left relief valve; 352. Right relief valve; 353. Control valve; 354. Left check valve; 355. Right check valve; 356. Left damping; 357. Right damping; 4. Cut-off valve; 5. Proportional solenoid valve; 6. Steering cylinder; 7. Electric control handle. 8. Pilot oil source valve; 81. Pressure reducing valve core; 82. Filter element; 91. Pressure sensor 1; 92. Pressure sensor 2; 10. Controller. DETAILED DESCRIPTION

[0018] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0019] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention. Example

[0020] from Figure 1 The present embodiment provides a steering hydraulic system for a loader, comprising a steering gear 2, a steering cylinder 6, and a steering pump 1 connected to an oil tank, which also comprises a flow amplification valve 3, a pilot oil source valve 8, a cut-off valve 4, and a proportional solenoid valve 5. The oil outlet of the steering pump 1 is connected to both the P port of the flow amplification valve 3 and the P port of the pilot oil source valve 8; the P port of the cut-off valve 4 is connected to the U port of the pilot oil source valve 8, the A port and the B port of the cut-off valve 4 are respectively connected to the P port of the proportional solenoid valve 5 and the P port of the steering gear 2, the L port and the R port of the steering gear 2 are respectively connected to the a port and the b port of the flow amplification valve 3, the T port of the steering gear 2 is connected to the oil tank, and the L port and the R port of the proportional solenoid valve 5 are respectively connected to the a port and the b port of the flow amplification valve 3.

[0021] When the port a of the flow amplifying valve 3 is acted upon by hydraulic oil, the port A of the flow amplifying valve 3 outputs hydraulic oil to the steering cylinder 6 to achieve left steering; when the port b of the flow amplifying valve 3 is acted upon by hydraulic oil, the port B of the flow amplifying valve 3 outputs hydraulic oil to the steering cylinder 6 to achieve right steering; it is common knowledge in the art that hydraulic oil drives the steering cylinder 6 to steer, which will not be elaborated here.

[0022] The cut-off valve 4 includes a left position and a right position. When the cut-off valve 4 is in the right position, the P port of the cut-off valve 4 is connected to its B port; when turning left, in response to the L port pressure value of the steering gear 2 being 0, or when turning right, in response to the R port pressure value of the steering gear 2 being 0, the cut-off valve 4 switches to the left position, and the P port of the cut-off valve 4 is connected to both its A port and its B port.

[0023] The working principle is explained in combination. For example, when the whole machine turns right, the steering wheel is turned right to send a right turn signal, and the steering pump 1 sucks hydraulic oil from the oil tank, and the hydraulic oil enters the oil inlet P of the pilot oil source valve 8. In a specific embodiment, the pilot oil source valve 8 is provided with a pressure reducing valve core 81 and a filter element 82. The hydraulic oil is reduced in pressure by the pressure reducing valve core 81 of the pilot oil source valve 8 and filtered by the filter element 82. The hydraulic oil enters the oil inlet P of the cut-off valve 4 through the oil outlet U of the pilot oil source valve 8 and passes through the B port of the cut-off valve 4 through the steering column belt under the steering wheel. The moving steering gear 2 valve core (not shown in the figure) enters the P port of the steering gear 2, and the hydraulic oil passes through the inside of the steering gear 2 and enters the oil outlet R port of the steering gear 2 and is output to the b port of the flow amplification valve 3, so that the B port of the flow amplification valve 3 outputs the hydraulic oil to the steering cylinder 6 to achieve right steering. In a specific embodiment, after the hydraulic oil enters the b port of the flow amplification valve 3, it passes through the internal channel of the valve core and passes through the damping or throttling hole to reach the steering oil port a port at the other end of the valve core, and then flows back to the hydraulic oil tank through the T port of the steering gear 2.

[0024] However, when the steering gear 2 fails due to the spool of the steering gear 2, the output pressure of the R port of the steering gear 2 outlet is lower than the preset threshold value when the steering wheel is turned. In a specific embodiment, the pressure sensor 91 is used to detect the pressure of the R port of the steering gear 2 outlet. Usually, when the steering gear 2 fails due to the spool of the steering gear 2, there is no pressure signal from the pressure sensor 91. At this time, the controller 10 will send out an alarm signal and control the P port of the cut-off valve 4 to be connected with the B port and the A port. The hydraulic oil flowing out of the oil outlet U port of the pilot oil source valve 8 flows into the oil inlet P of the proportional solenoid valve 5 through the oil outlet A port of the cut-off valve 4. The R port of the proportional solenoid valve 5 outputs hydraulic oil and acts on the b port of the flow amplification valve 3, so that the B port of the flow amplification valve 3 outputs hydraulic oil to the steering cylinder 6 to achieve right steering, so that reliable and stable steering can be performed even when the steering gear 2 fails due to the spool of the steering gear 2.

[0025] In a specific embodiment, the cut-off valve 4 includes a left position and a right position, and the position change of the cut-off valve 4 is controlled by a solenoid valve; when the cut-off valve 4 is in the left position, the P port of the cut-off valve 4 is connected to both its A port and its B port, and when the cut-off valve 4 is in the right position, the P port of the cut-off valve 4 is connected to its B port. The proportional solenoid valve 5 includes a left position, a middle position and a right position; the position change of the proportional solenoid valve 5 is controlled by a solenoid valve; when the proportional solenoid valve 5 is in the left position, the P port and the L port of the proportional solenoid valve 5 are connected, and the R port and the T port of the proportional solenoid valve 5 are connected; when the proportional solenoid valve 5 is in the middle position, the P port of the proportional solenoid valve 5 is cut off; when the proportional solenoid valve 5 is in the right position, the P port and the R port of the proportional solenoid valve 5 are connected, and the L port and the T port of the proportional solenoid valve 5 are connected.

[0026] In actual working process, the controller 10 receives the pressure signals of the L port and the R port of the steering gear 2, and the controller 10 controls the working position of the cut-off valve 4 and the proportional solenoid valve 5 through the solenoid valve according to the pressure signals. The working principle is the same as above, and will not be elaborated here. Of course, in addition to the solenoid valve control, other hydraulic controls with the same functions can also be used, as long as the hydraulic oil flow direction is the same.

[0027] The above description is based on right turn. If it is a left turn, the L port of the steering gear 2 or the L port of the proportional solenoid valve 5 outputs hydraulic oil and finally acts on the a port of the flow amplification valve 3, so that the A port of the flow amplification valve 3 outputs hydraulic oil to the steering cylinder 6 to achieve left turn. After the hydraulic oil enters the a port of the flow amplification valve 3, it passes through the internal channel of the valve core to reach the steering oil port b port at the other end of the valve core, and then flows back to the hydraulic oil tank through the T port of the steering gear 2. The working principle is the same as the right turn, which will not be repeated here.

[0028] Further, the flow amplification valve 3 is explained. The above text records that the port a and port b of the flow amplification valve 3 are used as control oil ports. The flow amplification valve 3 includes a diverter valve core 32 and a flow amplification valve core 33; the diverter valve core 32 includes a first oil port, a second oil port and a third oil port, and the flow amplification valve core 33 includes a first oil inlet, a first oil return port, a first working oil port and a second working oil port; the flow amplification valve core 33, the first oil return port is connected to the oil tank, the first working oil port is connected to the A port of the flow amplification valve 3 through the first oil circuit, and the second working oil port is connected to the B port of the flow amplification valve 3 through the second oil circuit.

[0029] The first oil port of the diverter valve core 32 is connected to the steering pump 1, the second oil port is connected to the first oil inlet of the flow amplification valve core 33, and the third oil port is used to connect to other external systems; a return spring is provided at the left end of the diverter valve core 32, when the diverter valve core 32 is in the left position, the first oil port and the second oil port of the diverter valve core 32 are connected, when the diverter valve core is in the middle position, the first oil port of the diverter valve core is connected to the second oil port and the third oil port; a damper is provided on the oil circuit between the first oil port and the third oil port; when the diverter valve core is in the right position, the first oil port of the diverter valve core is connected to the second oil port and the third oil port; a damper is provided on the oil circuit between the first oil port and the second oil port. In this embodiment, the flow entering the steering system can be controlled by the position of the valve core. When the diverter valve core is in the middle position, when the flow required for steering is met, the excess hydraulic oil is merged to other systems through the PF, and when the diverter valve core is in the right position, all the hydraulic oil passing through the diverter valve core is sent to other systems through the PF.

[0030] In actual work, when the engine drives the steering pump 1 to rotate, the steering pump 1 starts to work and draws oil from the oil tank. When the steering wheel and the electric control handle 7, which are the steering control elements, have no steering action, the first oil inlet of the flow amplification valve core 33 is cut off, and the hydraulic oil output by the steering pump 1 acts on the right end of the diverter valve core 32, pushing the diverter valve core 32 to change direction, so that the hydraulic oil merges into other systems through the third oil port in the diverter valve core 32.

[0031] Further, the flow amplification valve core 33 includes a left position, a middle position and a right position, the left end of the flow amplification valve core 33 is connected to the port a of the flow amplification valve 3, and the right end of the flow amplification valve core 33 is connected to the port b of the flow amplification valve 3; When the flow amplification valve core 33 is in the left position, the first oil inlet and the first oil return port of the flow amplification valve core 33 are connected to the first working oil port and the second working oil port respectively; When the flow amplification valve core 33 is in the middle position, the first oil inlet and the first oil return port of the flow amplification valve core 33 are cut off; When the flow amplification valve core 33 is in the right position, the first oil inlet and the first oil return port of the flow amplification valve core 33 are communicated with the second working oil port and the first working oil port respectively.

[0032] The flow amplification valve core 33 in this embodiment is switched by hydraulic control: when there is no steering control signal, the flow amplification valve core 33 maintains a neutral position; when a left turn is required, the hydraulic oil acts on the left end of the flow amplification valve core 33 through the a port of the flow amplification valve 3, driving the flow amplification valve core 33 to the left position, and the hydraulic oil passes through the first oil inlet and the first working oil port, so that the A port of the flow amplification valve 3 outputs the hydraulic oil to the steering cylinder 6 to achieve left steering; when a right turn is required, the hydraulic oil acts on the right end of the flow amplification valve core 33 through the b port of the flow amplification valve 3, driving the flow amplification valve core 33 to the right position, and the hydraulic oil passes through the first oil inlet and the second working oil port, so that the B port of the flow amplification valve 3 outputs the hydraulic oil to the steering cylinder 6 to achieve right steering.

[0033] In addition, in order to protect the oil circuit, the flow amplification valve 3 also includes a shuttle valve 34 and a relief valve 31. The two oil inlets of the shuttle valve 34 are respectively connected to the first oil circuit and the second oil circuit; the oil outlet of the shuttle valve 34 is connected to the oil return circuit between the first oil return port and the oil tank through the third oil circuit; the relief valve 31 is arranged on the third oil circuit; the left end of the diverter valve core 32 is connected to the third oil circuit and is located upstream of the relief valve 31, and the right end of the diverter valve core 32 is connected between the second oil port of the diverter valve core 32 and the first oil inlet of the flow amplification valve core 33.

[0034] Specifically, when the pressure oil flows into the A port or the B port of the flow amplification valve 3, the hydraulic oil of the first oil circuit or the second oil circuit is output to the oil inlet of the relief valve 31 through the outlet of the shuttle valve 34. If the pressure of the first oil circuit or the second oil circuit rises and exceeds the set pressure of the relief valve 31, the relief valve 31 will open, and the oil outlet of the relief valve 31 will be directly connected to the T port of the flow amplification valve 3 for oil return. At this time, the pressure acting on the left end of the diverter valve core 32 disappears, and the hydraulic oil flows out to other systems through the third oil port of the diverter valve core 32 and the PF port of the flow amplification valve 3, thereby protecting the oil circuit through the oil return channel. After the steering load is eliminated, the pressure of the first oil circuit or the second oil circuit decreases, the relief valve 31 is closed, and the diverter valve core 32 returns to the normal position.

[0035] Furthermore, in order to perform buffering operations, the hydraulic system in this embodiment further includes a buffer valve 35, and the buffer valve 35 includes a left overflow valve 351, a right overflow valve 352, a left check valve 354, a right check valve 355 and a control valve 353; The fourth oil circuit and the fifth oil circuit are connected in parallel between the first oil circuit and the second oil circuit mentioned above; the left overflow valve 351 and the right overflow valve 352 are arranged on the fourth oil circuit in opposite flow directions. As is common knowledge in the art, the oil inlet ends of the left overflow valve 351 and the right overflow valve 352 are connected to the second oil circuit and the first oil circuit respectively; the left check valve 354 and the right check valve 355 are arranged on the fifth oil circuit in opposite flow directions; the control valve 353 The oil inlet is connected between the left overflow valve 351 and the right overflow valve 352, and the oil outlet of the control valve 353 is connected between the left check valve 354 and the right check valve 355; the left end of the control valve 353 is connected to the connecting oil circuit between the left overflow valve 351 and the left check valve 354 through the left damper 356, and the right end of the control valve 353 is connected to the connecting oil circuit between the right overflow valve 352 and the right check valve 355 through the right damper 357.

[0036] To explain in conjunction with the specific working principle, affected by the load of the steering resistance, port A (corresponding to the left-turn condition) or port B (corresponding to the right-turn condition) of the flow amplification valve 3 will have an instantaneous high pressure.

[0037] Take the right turn condition as an example. The same is true for the left turn condition. If there is an instantaneous high pressure at port B, the overflow pressure of the two-way buffer valve 35 is set to be low. At this time, the left overflow valve 351 is opened, and the oil enters port A through the control valve 353 and the right check valve 355 and turns to the low-pressure side, thereby reducing the pressure shock during startup. At this time, the right side of the control valve 353 is affected by the oil pressure at port B, pushing the valve core to move to the left, closing the control valve 353, and preventing the oil pressure at port B from continuously unloading to the low-pressure side. This process lasts for a short time in actual operation, but can achieve a better buffering effect. Example

[0038] Based on the same inventive concept as in Example 1, this embodiment provides a control method for a steering hydraulic system of a loader, which includes: In response to a right turn control signal: If the output pressure of the R port of the steering gear 2 is greater than the preset threshold, the P port of the cut-off valve 4 is controlled to be connected only to the B port, and the P port of the proportional solenoid valve 5 is cut off; the hydraulic oil output from the R port of the steering gear 2 acts on the b port of the flow amplification valve 3, so that the B port of the flow amplification valve 3 outputs the hydraulic oil to the steering cylinder 6 to achieve right steering; If the output pressure of the R port of the steering gear 2 is less than the preset threshold, the P port of the cut-off valve 4 is controlled to be connected to the A port and the B port, and the P port and the R port of the proportional solenoid valve 5 are connected; the R port of the proportional solenoid valve 5 outputs hydraulic oil to act on the b port of the flow amplification valve 3, so that the B port of the flow amplification valve 3 outputs hydraulic oil to the steering cylinder 6 to achieve right steering; In response to a left turn control signal: If the output pressure of the L port of the steering gear 2 is greater than a preset threshold, the P port of the cut-off valve 4 is controlled to be connected only to the B port, and the P port of the proportional solenoid valve 5 is cut off; the hydraulic oil output from the L port of the steering gear 2 acts on the a port of the flow amplification valve 3, so that the A port of the flow amplification valve 3 outputs the hydraulic oil to the steering cylinder 6 to achieve left steering; If the output pressure of the L port of the steering gear 2 is less than a preset threshold, the P port of the cut-off valve 4 is controlled to be connected to the A port and the B port, and the P port and the L port of the proportional solenoid valve 5 are connected; the L port of the proportional solenoid valve 5 outputs hydraulic oil to act on the a port of the flow amplifying valve 3, so that the A port of the flow amplifying valve 3 outputs hydraulic oil to the steering cylinder 6 to achieve right steering.

[0039] In a specific embodiment, a pressure sensor 1 91 is provided at the L port of the steering gear 2 , and a pressure sensor 2 92 is provided at the R port of the steering gear 2 . Example

[0040] Based on the same inventive concept as in Example 1, this embodiment provides a loader, which includes a loader steering hydraulic system as described in Example 1.

[0041] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A steering hydraulic system for a loader, comprising a steering gear (2), a steering cylinder (6), and a steering pump (1) connected to an oil tank, characterized in that: It also includes a flow amplification valve (3), a pilot oil source valve (8), a cut-off valve (4), and a proportional solenoid valve (5); the oil outlet of the steering pump (1) is connected to the P port of the flow amplification valve (3) and the P port of the pilot oil source valve (8); the P port of the cut-off valve (4) is connected to the U port of the pilot oil source valve (8); the A port and the B port of the cut-off valve (4) are respectively connected to the P port of the proportional solenoid valve (5) and the P port of the steering gear (2); the L port and the R port of the steering gear (2) are respectively connected to the a port and the b port of the flow amplification valve (3); the T port of the steering gear (2) is connected to the oil tank; the L port and the R port of the proportional solenoid valve (5) are respectively connected to the a port and the b port of the flow amplification valve (3); and the T port of the flow amplification valve (3) is connected to the oil tank; When the port a of the flow amplifying valve (3) is acted upon by hydraulic oil, the port A of the flow amplifying valve (3) outputs hydraulic oil to the steering cylinder (6) to achieve left steering; when the port b of the flow amplifying valve (3) is acted upon by hydraulic oil, the port B of the flow amplifying valve (3) outputs hydraulic oil to the steering cylinder (6) to achieve right steering; the cut-off valve (4) comprises a left position and a right position, and when the cut-off valve (4) is in the right position, the port P of the cut-off valve (4) is connected to its port B; when the cut-off valve (4) is in the left position, the port P of the cut-off valve (4) is connected to both its port A and its port B.

2. A loader steering hydraulic system according to claim 1, characterized in that: The switching of the cut-off valve (4) is controlled by a solenoid valve.

3. A loader steering hydraulic system according to claim 2, characterized in that: The proportional solenoid valve (5) comprises a left position, a middle position and a right position; the position change of the proportional solenoid valve (5) is controlled by the solenoid valve; when the proportional solenoid valve (5) is in the left position, the P port and the L port of the proportional solenoid valve (5) are connected, and the R port and the T port of the proportional solenoid valve (5) are connected; when the proportional solenoid valve (5) is in the middle position, the P port of the proportional solenoid valve (5) is cut off; when the proportional solenoid valve (5) is in the right position, the P port and the R port of the proportional solenoid valve (5) are connected, and the L port and the T port of the proportional solenoid valve (5) are connected.

4. A loader steering hydraulic system according to claim 1, characterized in that: The flow amplification valve (3) comprises a flow diverter valve core (32) and a flow amplification valve core (33); the flow diverter valve core (32) comprises a first oil port, a second oil port and a third oil port, and the flow amplification valve core (33) comprises a first oil inlet port, a first oil return port, a first working oil port and a second working oil port; The diverter valve core (32) has a first oil port connected to the steering pump (1), a second oil port connected to the first oil inlet of the flow amplifying valve core (33), and a third oil port for connecting to other external systems; the diverter valve core (32) includes a left position, a middle position, and a right position; The flow amplifying valve core (33) has a first oil return port connected to the oil tank, a first working oil port connected to port A of the flow amplifying valve (3) through a first oil circuit, and a second working oil port connected to port B of the flow amplifying valve (3) through a second oil circuit; When the diverter valve core (32) is in the left position, the first oil port and the second oil port of the diverter valve core (32) are connected. When the diverter valve core (32) is in a neutral position, the first oil port of the diverter valve core (32) is connected to both the second oil port and the third oil port; a damper is provided on the oil path between the first oil port and the third oil port; When the diverter valve core (32) is in the right position, the first oil port of the diverter valve core (32) is connected to both the second oil port and the third oil port; and a damper is provided on the oil path between the first oil port and the second oil port.

5. A loader steering hydraulic system according to claim 4, characterized in that: Also includes: A shuttle valve (34), wherein two oil inlets are respectively connected to the first oil circuit and the second oil circuit; an oil outlet of the shuttle valve (34) is connected to the oil return circuit between the first oil return port and the oil tank via a third oil circuit; A relief valve (31) is provided on the third oil circuit; The left end of the diverter valve core (32) is connected to the third oil circuit and is located upstream of the overflow valve (31). A return spring is also provided at the left end of the diverter valve core (32). The right end of the diverter valve core (32) is connected between the second oil port of the diverter valve core (32) and the first oil inlet of the flow amplification valve core (33).

6. A loader steering hydraulic system according to claim 4, characterized in that: The flow amplifying valve core (33) comprises a left position, a middle position and a right position, the left end of the flow amplifying valve core (33) is connected to the port a of the flow amplifying valve (3), and the right end of the flow amplifying valve core (33) is connected to the port b of the flow amplifying valve (3); When the flow amplification valve core (33) is in the left position, the first oil inlet and the first oil return port of the flow amplification valve core (33) are respectively connected to the first working oil port and the second working oil port; When the flow amplifying valve core (33) is in the middle position, the first oil inlet and the first oil return port of the flow amplifying valve core (33) are cut off; When the flow amplification valve core (33) is in the right position, the first oil inlet and the first oil return port of the flow amplification valve core (33) are respectively connected to the second working oil port and the first working oil port.

7. A loader steering hydraulic system according to claim 4, characterized in that: Also includes: The buffer valve (35) comprises a left overflow valve (351), a right overflow valve (352), a left check valve (354), a right check valve (355) and a control valve (353); A fourth oil circuit and a fifth oil circuit connected in parallel are connected between the first oil circuit and the second oil circuit; the left overflow valve (351) and the right overflow valve (352) are arranged on the fourth oil circuit in opposite flow directions, and the left check valve (354) and the right check valve (355) are arranged on the fifth oil circuit in opposite flow directions; the oil inlet of the control valve (353) is connected between the left overflow valve (351) and the right overflow valve (352), and the oil outlet of the control valve (353) is connected between the left check valve (354) and the right check valve (355); the left end of the control valve (353) is connected to the connecting oil circuit between the left overflow valve (351) and the left check valve (354), and the right end of the control valve (353) is connected to the connecting oil circuit between the right overflow valve (352) and the right check valve (355).

8. A control method for a steering hydraulic system of a loader, characterized in that: A loader steering hydraulic system according to any one of claims 1 to 7 is implemented, comprising: In response to a right turn control signal: If the output pressure of the R port of the steering gear (2) is greater than a preset threshold, the P port of the cut-off valve (4) is controlled to be connected only to the B port, and the P port of the proportional solenoid valve (5) is cut off; the hydraulic oil output from the R port of the steering gear (2) acts on the b port of the flow amplification valve (3), so that the B port of the flow amplification valve (3) outputs the hydraulic oil to be connected to the steering cylinder (6) to achieve right steering; If the output pressure of the R port of the steering gear (2) is less than a preset threshold, the P port of the cut-off valve (4) is controlled to be connected to the A port and the B port, and the P port and the R port of the proportional solenoid valve (5) are connected; the hydraulic oil output from the R port of the proportional solenoid valve (5) acts on the b port of the flow amplification valve (3), so that the B port of the flow amplification valve (3) outputs the hydraulic oil to the steering cylinder (6) to achieve right steering; In response to the left turn control signal, If the output pressure of the L port of the steering gear (2) is greater than a preset threshold, the P port of the cut-off valve (4) is controlled to be connected only to the B port, and the P port of the proportional solenoid valve (5) is cut off; the hydraulic oil output from the L port of the steering gear (2) acts on the a port of the flow amplification valve (3), so that the A port of the flow amplification valve (3) outputs the hydraulic oil to the steering cylinder (6) to achieve left steering; If the output pressure of the L port of the steering gear (2) is less than a preset threshold value, the P port of the cut-off valve (4) is controlled to be connected to the A port and the B port, and the P port and the L port of the proportional solenoid valve (5) are connected; the hydraulic oil output from the L port of the proportional solenoid valve (5) acts on the a port of the flow amplification valve (3), so that the hydraulic oil output from the A port of the flow amplification valve (3) is connected to the steering cylinder (6) to achieve right steering.

9. The control method of a loader steering hydraulic system according to claim 8, characterized in that: A pressure sensor 1 (91) is provided at the L port of the steering gear (2), and a pressure sensor 2 (92) is provided at the R port of the steering gear (2).

10. A loader, characterized in that: A loader steering hydraulic system comprising any one of claims 1-7.

Images