CN115898975A

CN115898975A - Hydraulic system with adjustable speed and acting force, control method thereof and engineering machinery

Info

Publication number: CN115898975A
Application number: CN202211355792.5A
Authority: CN
Inventors: 吴仲吉; 赵海涛; 段沛; 李林志; 彭亮
Original assignee: Zoomlion Heavy Industry Science and Technology Co Ltd
Current assignee: Zoomlion Heavy Industry Science and Technology Co Ltd
Priority date: 2022-11-01
Filing date: 2022-11-01
Publication date: 2023-04-04

Abstract

The invention provides a hydraulic system with adjustable speed and acting force, which comprises an oil tank, a hydraulic pump, a motor, a hydraulic reversing valve, a first reversing valve, a second reversing valve, a first throttling valve, a second throttling valve, a first hydraulic cylinder and a second hydraulic cylinder, wherein the hydraulic pump is connected with the motor through a hydraulic pump; piston rods of the first hydraulic cylinder and the second hydraulic cylinder are connected in parallel and move synchronously in the same direction, and the inner diameter of the first hydraulic cylinder is smaller than that of the second hydraulic cylinder. The hydraulic pump is connected to the first hydraulic cylinder and the second hydraulic cylinder through a main oil way; an oil inlet of the hydraulic reversing valve is communicated with the main oil way, two working oil ports are respectively communicated with a first oil cavity and a second oil cavity of the first hydraulic cylinder, oil inlets of the first reversing valve and the second reversing valve are communicated with the main oil way, and oil outlets of the first reversing valve and the second reversing valve are respectively communicated with two hydraulic control ends of the hydraulic reversing valve; oil inlets of the first throttling valve and the second throttling valve are communicated with the main oil way, an oil outlet of the first throttling valve is communicated to a second oil cavity of the second hydraulic cylinder, and an oil outlet of the second throttling valve is communicated to a first oil cavity of the second hydraulic cylinder.

Description

Hydraulic system with adjustable speed and acting force, control method thereof and engineering machinery

Technical Field

The invention relates to the technical field of hydraulic pressure, in particular to a hydraulic system with adjustable speed and acting force, a control method thereof and engineering machinery.

Background

As a transmission technology, the hydraulic system can generate large acting force, can perform stepless speed regulation in a wide range, has good operation performance, and is widely applied to various fields. Pressure and flow are two factors that the hydraulic system regulates, and correspondingly, the system output force and speed, and generally, the control of pressure and flow is mainly regulated by a pressure valve and a flow valve or a variable pump. However, in some special occasions, for example, under the condition of limited installation space or determined power source hydraulic pressure, some commonly used speed and pressure regulating systems may have the disadvantages of overlarge volume, low efficiency, inflexibility and the like.

Fig. 1 is a schematic diagram of a hydraulic system of a molding machine according to the prior art, which includes: the device comprises a filter 1, a fixed displacement pump 2, electromagnetic

directional valves

3, 6, 7 and 8, an overflow valve 4, a pressure reducing valve 5, double-hydraulic-control one-

way valves

9, 10 and 11, one-

way throttle valves

12, 13 and 14,

pressure relays

15 and 20,

energy accumulators

16 and 19, a driving cylinder 17, a driven cylinder 18 and a forming cylinder 21. In the state shown in the figure, the electromagnets of all the electromagnetic valves are in a power-off state, and the hydraulic oil of the fixed displacement pump 2 is unloaded through the two-position four-way electromagnetic directional valve 3. When the hydraulic system works, firstly, the electromagnet 7YA of the two-position four-way electromagnetic directional valve 3 is electrified, and at the moment, the whole hydraulic system works under the set working pressure. When the operation button is pressed, the electromagnets 1YA and 3YA of the three-position four-way electromagnetic directional valves 6 and 7 are simultaneously electrified, the three-position four-way electromagnetic directional valves 6 and 7 are switched to be in the left position, hydraulic oil enters the driving cylinder 17 and the driven cylinder 18 through the pressure reducing valve 5, the two cylinders synchronously and quickly run to the designated positions, and the speed of the two cylinders is adjusted by the one-

way throttle valves

12 and 13. When the two cylinders of the driving cylinder 17 and the driven cylinder 18 move to the set positions, the electromagnet 5YA of the three-position four-way electromagnetic directional valve 8 is electrified, hydraulic oil enters the rodless cavity of the forming cylinder 21, the hydraulic oil in the rod cavity returns to the oil tank, and the forming cylinder 21, the driving cylinder 17 and the driven cylinder 18 overcome the heavy load and move slowly together.

When the hydraulic system needs to move at a light load and a high speed, the hydraulic system is realized by controlling a main driven cylinder system and a driven cylinder system. When the hydraulic system is required to output acting force to overcome heavy load, the forming cylinder system and the main driven cylinder system are controlled simultaneously to realize the purpose.

The above prior art also has the following disadvantages:

1. the same hydraulic elements are adopted in the main and auxiliary cylinder systems, so that the structure is complex, the space occupation is large, the space utilization rate is low, and the cost is high.

2. The master cylinder and the slave cylinder are controlled by the same system to achieve a synchronization effect, but under the condition that the load difference of the two cylinders is large and uncertain, the synchronization capacity is weak and the flexibility is poor.

3. And the inlet end throttling speed regulation is adopted, so that the stability is poor, and the working condition of a negative load cannot be met.

4. The adoption of the electromagnetic directional valve influences the directional stability of the actuating mechanism and is not suitable for the working condition that the system needs large flow.

Disclosure of Invention

The invention aims to provide a hydraulic system with adjustable speed and acting force, a control method thereof and engineering machinery.

The invention provides a hydraulic system with adjustable speed and acting force, which comprises an oil tank, a hydraulic pump connected with the oil tank, a motor for driving the hydraulic pump, a hydraulic reversing valve, a first reversing valve, a second reversing valve, a first throttling valve, a second throttling valve, a first hydraulic cylinder and a second hydraulic cylinder, wherein the hydraulic pump is connected with the oil tank; piston rods of the first hydraulic cylinder and the second hydraulic cylinder are arranged in parallel and move synchronously towards the same direction, and the inner diameter of the first hydraulic cylinder is smaller than that of the second hydraulic cylinder; the hydraulic pump is connected to the first hydraulic cylinder and the second hydraulic cylinder through a main oil passage; an oil inlet of the hydraulic reversing valve is communicated with the main oil way, two working oil ports of the hydraulic reversing valve are respectively communicated with a first oil cavity and a second oil cavity of the first hydraulic cylinder, oil inlets of the first reversing valve and the second reversing valve are communicated with the main oil way, and oil outlets of the first reversing valve and the second reversing valve are respectively communicated to two hydraulic control ends of the hydraulic reversing valve; oil inlets of the first throttle valve and the second throttle valve are communicated with the main oil way, an oil outlet of the first throttle valve is communicated to a second oil cavity of the second hydraulic cylinder through a first oil dividing way, and an oil outlet of the second throttle valve is communicated to a first oil cavity of the second hydraulic cylinder through a second oil dividing way.

Further, the first directional valve comprises a first directional valve component, a second directional valve component and a first electromagnetic directional valve, a working oil port B of the second directional valve component and an oil inlet P of the first electromagnetic directional valve are communicated with the main oil way, a working oil port a and a working oil port B of the first electromagnetic directional valve are respectively communicated with a control oil port X of the first directional valve component and a control oil port X of the second directional valve component, the working oil port a of the first directional valve component and the working oil port a of the second directional valve component are communicated with one of hydraulic control ends of the hydraulic directional valve, and an oil return port T of the first electromagnetic directional valve and the working oil port B of the first directional valve component are communicated with an oil return tank; the second reversing valve comprises a third directional valve component, a fourth directional valve component and a second electromagnetic reversing valve, a working oil port B of the third directional valve component and an oil inlet P of the second electromagnetic reversing valve are communicated with the main oil way, a working oil port A and a working oil port B of the second electromagnetic reversing valve are respectively communicated with a control oil port X of the third directional valve component and a control oil port X of the fourth directional valve component, the working oil port A of the third directional valve component and the working oil port A of the fourth directional valve component are communicated to the other hydraulic control end of the hydraulic reversing valve, and an oil return port T of the second electromagnetic reversing valve and the working oil port B of the fourth directional valve component are communicated with an oil return tank.

Further, the first throttle valve includes a first throttle valve assembly, a fifth directional valve assembly and a third electromagnetic directional valve, a working oil port B of the fifth directional valve assembly and an oil inlet P of the third electromagnetic directional valve are communicated with the main oil path, a working oil port a and a working oil port B of the third electromagnetic directional valve are respectively communicated with a control oil port X of the first throttle valve assembly and a control oil port X of the fifth directional valve assembly, the working oil port a of the first throttle valve assembly and the working oil port a of the fifth directional valve assembly are communicated with the second oil chamber of the second hydraulic cylinder through the first branch oil path, and an oil return port T of the third electromagnetic directional valve and the working oil port B of the first throttle valve assembly are communicated with an oil return tank; the second throttle valve comprises a fifth directional valve component, a second throttle valve component and a fourth electromagnetic directional valve, a working oil port B of the fifth directional valve component and an oil inlet P of the fourth electromagnetic directional valve are communicated with the main oil way, a working oil port A and a working oil port B of the fourth electromagnetic directional valve are respectively communicated with a control oil port X of the fifth directional valve component and a control oil port X of the second throttle valve component, the working oil port A of the fifth directional valve component and the working oil port A of the second throttle valve component are communicated to a first oil cavity of the second hydraulic cylinder through the second branch oil way, and an oil return port T of the fourth electromagnetic directional valve and the working oil port B of the second throttle valve component are communicated with an oil return box.

Further, the hydraulic lock also comprises a third reversing valve and a hydraulic lock; the hydraulic lock is provided with a first oil inlet, a second oil inlet, a first oil outlet and a second oil outlet, wherein the first oil inlet and the first oil outlet are located on the first oil dividing path, the second oil inlet and the second oil outlet are located on the second oil dividing path, the first oil inlet of the hydraulic lock is communicated with the oil outlet of the first throttle valve, the first oil outlet of the hydraulic lock is communicated with the second oil chamber of the second hydraulic cylinder, the second oil inlet of the hydraulic lock is communicated with the oil outlet of the second throttle valve, and the second oil outlet of the hydraulic lock is communicated with the first oil chamber of the second hydraulic cylinder.

Further, the third directional valve comprises a seventh directional valve assembly, an eighth directional valve assembly and a fifth electromagnetic directional valve, a working oil port a of the eighth directional valve assembly and an oil inlet P of the fifth electromagnetic directional valve are communicated with the main oil way, a working oil port a and a working oil port B of the fifth electromagnetic directional valve are respectively communicated with a control oil port X of the seventh directional valve assembly and a control oil port X of the eighth directional valve assembly, the working oil port a of the seventh directional valve assembly and the working oil port B of the eighth directional valve assembly are communicated to the hydraulic lock, and an oil return port T of the fifth electromagnetic directional valve and the working oil port B of the seventh directional valve assembly are communicated with an oil return tank; the hydraulic lock comprises a first pressure valve component, a second pressure valve component, a first shuttle valve and a second shuttle valve, a first oil inlet of the hydraulic lock is a working oil port A of the first pressure valve component, a first oil outlet of the hydraulic lock is a working oil port B of the first pressure valve component, a second oil inlet of the hydraulic lock is a working oil port A of the second pressure valve component, a second oil outlet of the hydraulic lock is a working oil port B of the second pressure valve component, the first shuttle valve is connected to a control oil port of the first pressure valve component, the second shuttle valve is connected to a control oil port of the second pressure valve component, and control ends of the first shuttle valve and the second shuttle valve are communicated with the third reversing valve.

Further, still be equipped with first overflow valve and first manometer on the first oil distribution way, still be equipped with second overflow valve and second manometer on the second oil distribution way.

Furthermore, an unloading valve is also arranged on the main oil path, and comprises a pressure valve assembly, a sixth electromagnetic directional valve and a third overflow valve; the main oil way is also provided with a third pressure gauge, a plug-in type one-way valve, a pressure sensor and a fine filter; the hydraulic pump is a fixed displacement pump.

Further, the first hydraulic cylinder and the second hydraulic cylinder share the same cylinder head and cylinder bottom.

The invention also provides a control method of the hydraulic system with adjustable speed and acting force, which is characterized in that the control method is used for controlling the hydraulic system with adjustable speed and acting force, and comprises the following steps: when a piston rod of the hydraulic cylinder needs to extend out, controlling the oil inlet of a second oil cavity of the first hydraulic cylinder or controlling the oil inlet of a second oil cavity of the second hydraulic cylinder when the speed and acting force adjustable hydraulic system is in light load; when the speed and acting force adjustable hydraulic system is in a heavy load, controlling the second oil cavity of the first hydraulic cylinder to be fed with oil or controlling the second oil cavity of the second hydraulic cylinder to be fed with oil, or controlling the second oil cavity of the first hydraulic cylinder and the second oil cavity of the second hydraulic cylinder to be fed with oil at the same time; when a piston rod of the hydraulic cylinder needs to retract, controlling the first oil cavity of the first hydraulic cylinder to feed oil or controlling the first oil cavity of the second hydraulic cylinder to feed oil when the hydraulic system with adjustable speed and acting force is in light load; when the speed and acting force adjustable hydraulic system is in a heavy load state, controlling the first oil cavity of the first hydraulic cylinder to be fed with oil or controlling the first oil cavity of the second hydraulic cylinder to be fed with oil, or controlling the first oil cavity of the first hydraulic cylinder and the first oil cavity of the second hydraulic cylinder to be fed with oil simultaneously.

The invention also provides engineering machinery which is characterized by comprising the hydraulic system with adjustable speed and acting force.

The hydraulic system with adjustable speed and acting force, the control method thereof and the engineering machinery provided by the invention have the following beneficial effects:

1. the hydraulic system with adjustable speed and acting force adopts a large-diameter hydraulic cylinder (a second hydraulic cylinder) and a small-diameter hydraulic cylinder (a first hydraulic cylinder) which are connected in parallel to form an integral double-rod hydraulic cylinder, the speed and the acting force of the system are adjusted in a stepping mode through the on-off combination of all oil holes of the metering pump under the condition that the metering pump is used, the effects of heavy load, low speed and light load and high speed are achieved, the synchronization effect is good, and the metering pump can be suitable for occasions with severe environments.

2. The hydraulic system with a simpler design controls the hydraulic double cylinders, and has the advantages of low cost, convenient and flexible control and easy realization.

3. And the cartridge valve system is adopted, so that the system is convenient to debug and update, the structure is compact, and the space utilization rate is high. The control current is small, which is beneficial to the program control of the system. Less leakage, capability of meeting pressure maintaining occasions with higher requirements, strong pollution resistance and reliable performance.

4. The parallel double hydraulic cylinders (the first hydraulic cylinder and the second hydraulic cylinder) are respectively controlled by independent loops, so that the control is convenient and flexible; furthermore, the system is provided with an unloading loop, so that the reactive loss and the heating of an oil source during waiting are reduced; furthermore, outlet throttling speed regulation and a hydraulic reversing valve are adopted, so that the stability of the system is improved, and the system is suitable for the working condition of negative load.

The above description is only an overview of the technical solutions of the present invention, and may be implemented according to the content of the description in order to make the technical means of the present invention more clearly understood, and in order to make the above speed and force adjustable hydraulic system, the control method thereof, and other objects, features, and advantages of the engineering machine of the present invention more obvious and understandable, the following description will specifically refer to the preferred embodiments, and will be made in conjunction with the accompanying drawings.

Drawings

Fig. 1 is a schematic diagram of a hydraulic system of a conventional molding machine.

FIG. 2 is a schematic diagram of a hydraulic system with adjustable speed and force according to a preferred embodiment of the present invention.

FIG. 3 is a schematic diagram of a speed and force adjustable hydraulic system according to a preferred embodiment of the present invention.

Detailed Description

To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined object, the following detailed description will be given of specific embodiments, structures, features and effects of a speed and force adjustable hydraulic system and a control method thereof and an engineering machine according to the present invention, with reference to the accompanying drawings and preferred embodiments:

the foregoing and other technical contents, features and effects of the present invention will be apparent from the following detailed description of the preferred embodiments, which is to be read in connection with the accompanying drawings. While the present invention has been described in connection with the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Fig. 2 is a schematic diagram of a speed and force adjustable hydraulic system according to a preferred embodiment of the present invention, as shown in fig. 2, the speed and force adjustable hydraulic system includes a tank 101, a hydraulic pump 102 connected to the tank 101, and a motor 103 for driving the hydraulic pump 102, and the hydraulic system further includes a hydraulically operated directional valve 123, a first directional valve 203, a second directional valve 204, a first throttle 205, a second throttle 206, a first hydraulic cylinder 128, and a second hydraulic cylinder 129. The piston rods of the first hydraulic cylinder 128 and the second hydraulic cylinder 129 are arranged in parallel and move synchronously in the same direction, and the inner diameter of the first hydraulic cylinder 128 is smaller than that of the second hydraulic cylinder 129.

The hydraulic pump 102 is connected to the first hydraulic cylinder 128 and the second hydraulic cylinder 129 through a main oil passage 300.

Specifically, an oil inlet P of the hydraulic reversing valve 123 is communicated with the main oil path 300, two working oil ports a and B of the hydraulic reversing valve 123 are respectively communicated with a first oil cavity and a second oil cavity of the first hydraulic cylinder 128, oil inlets of the first reversing valve 203 and the second reversing valve 204 are communicated with the main oil path 300, and oil outlets of the first reversing valve 203 and the second reversing valve 204 are respectively communicated with two hydraulic control ends of the hydraulic reversing valve 123.

Oil inlets of the first throttle valve 205 and the second throttle valve 206 are communicated with a main oil path 300, an oil outlet of the first throttle valve 205 is communicated to a second oil chamber of the second hydraulic cylinder 129 through a first oil dividing path 310, an oil outlet of the second throttle valve 206 is communicated to a first oil chamber of the second hydraulic cylinder 129 through a second oil dividing path 320, and oil passing amounts of the first throttle valve 205 and the second throttle valve 206 are adjustable.

The hydraulic system with adjustable speed and acting force is provided with the large-diameter hydraulic cylinder (the second hydraulic cylinder 129) and the small-diameter hydraulic cylinder (the first hydraulic cylinder 128) which are connected in parallel to form the integrated double-rod hydraulic cylinder, and the large-diameter hydraulic cylinder and the small-diameter hydraulic cylinder are respectively controlled by adopting independent loops, so that the hydraulic system is convenient and flexible to control, the effects of heavy load, low speed, light load and high speed can be realized by controlling the on-off combination of the two loops, and the synchronization effect is good.

In this embodiment, the first direction valve 203 and the second direction valve 204 are both cartridge type two-position three-way valves. The first direction valve 203 is used for controlling the on-off of the control oil path of one hydraulic end of the hydraulic direction valve 123, and the second direction valve 204 is used for controlling the on-off of the control oil path of the other hydraulic end of the hydraulic direction valve 123.

Specifically, the first direction valve 203 includes a first direction valve assembly 111, a second direction valve assembly 112, and a first electromagnetic direction valve 211, and the first electromagnetic direction valve 211 is a pilot valve. The working oil port B of the second directional valve assembly 112 and the oil inlet P of the first electromagnetic directional valve 211 are communicated with the main oil path 300, the working oil port a and the working oil port B of the first electromagnetic directional valve 211 are respectively communicated with the control oil port X of the first directional valve assembly 111 and the control oil port X of the second directional valve assembly 112, the working oil port a of the first directional valve assembly 111 and the working oil port a of the second directional valve assembly 112 are communicated to one of the hydraulic control ends of the hydraulic directional valve 123, and the oil return port T of the first electromagnetic directional valve 211 and the working oil port B of the first directional valve assembly 111 are communicated with the oil return tank. When the control electromagnet 2Y of the first electromagnetic directional valve 211 is energized, the first directional valve 203 is turned on.

The second reversing valve 204 comprises a third directional valve assembly 113, a fourth directional valve assembly 114 and a second electromagnetic reversing valve 212, a working oil port B of the third directional valve assembly 113 and an oil inlet P of the second electromagnetic reversing valve 212 are communicated with the main oil path 300, a working oil port a and a working oil port B of the second electromagnetic reversing valve 212 are respectively communicated with a control oil port X of the third directional valve assembly 113 and a control oil port X of the fourth directional valve assembly 114, the working oil port a of the third directional valve assembly 113 and the working oil port a of the fourth directional valve assembly 114 are communicated with the other hydraulic control end of the hydraulic reversing valve 123, and an oil return port T of the second electromagnetic reversing valve 212 and the working oil port B of the fourth directional valve assembly 114 are communicated with an oil return tank. When the control solenoid 3Y of the second electromagnetic directional valve 212 is energized, the second directional valve 204 is turned on.

In this embodiment, the first throttle valve 205 and the second throttle valve 206 are both plug-in two-position three-way valves. The first throttle valve 205 controls the opening/closing of the first branch oil passage 310 and the amount of oil flow, and the second throttle valve 206 controls the opening/closing of the second branch oil passage 320 and the amount of oil flow.

Specifically, the first throttle valve 205 includes a first throttle valve assembly 115, a fifth directional valve assembly 116 and a third electromagnetic directional valve 213, a working oil port B of the fifth directional valve assembly 116 and an oil inlet P of the third electromagnetic directional valve 213 communicate with the main oil path 300, a working oil port a and a working oil port B of the third electromagnetic directional valve 213 communicate with a control oil port X of the first throttle valve assembly 115 and a control oil port X of the fifth directional valve assembly 116, respectively, the working oil port a of the first throttle valve assembly 115 and the working oil port a of the fifth directional valve assembly 116 communicate with the second oil chamber of the second hydraulic cylinder 129 through a first oil distribution path 310, and an oil return port T of the third electromagnetic directional valve assembly 213 and the working oil port B of the first throttle valve assembly 115 communicate with an oil return tank. When the control electromagnet 4Y of the third electromagnetic directional valve 213 is energized, the first throttle valve 205 is turned on, and the oil flow rate of the first throttle valve 205 can be controlled by controlling the control handle of the first throttle valve assembly 115.

The second throttle 206 includes a fifth directional valve assembly 117, a second throttle valve assembly 118 and a fourth electromagnetic directional valve 214, a working oil port B of the fifth directional valve assembly 117 and an oil inlet P of the fourth electromagnetic directional valve 214 communicate with the main oil passage 300, a working oil port a and a working oil port B of the fourth electromagnetic directional valve 214 respectively communicate with a control oil port X of the fifth directional valve assembly 117 and a control oil port X of the second throttle valve assembly 118, the working oil port a of the fifth directional valve assembly 117 and the working oil port a of the second throttle valve assembly 118 communicate with the first oil chamber of the second hydraulic cylinder 129 through a second branch oil passage 320, and an oil return port T of the fourth electromagnetic directional valve 214 and the working oil port B of the second throttle valve assembly 118 communicate with an oil return tank. When the control electromagnet 5Y of the fourth electromagnetic directional valve 214 is energized, the second throttle valve 206 is turned on, and the oil flow rate of the second throttle valve 206 can be controlled by controlling the control handle of the second throttle valve assembly 118.

The adjustable speed and force hydraulic system further comprises a third directional control valve 207 and a hydraulic lock 208. The third reversing valve 207 is arranged on the control oil path and used for controlling the unlocking and locking of the hydraulic lock 208 and further controlling whether the hydraulic lock 208 is conducted reversely. When the two hydraulic cylinders are in heavy load and low speed, the hydraulic lock 208 automatically locks the loop of the second hydraulic cylinder 129 when the second hydraulic cylinder is in overspeed or reverse movement trend under the action of external force, and enters a pressure maintaining state.

Specifically, the hydraulic lock 208 has a first oil inlet, a second oil inlet, a first oil outlet and a second oil outlet, wherein the first oil inlet and the first oil outlet are located on the first oil dividing path 310, the second oil inlet and the second oil outlet are located on the second oil dividing path 320, the first oil inlet of the hydraulic lock 208 is communicated with the oil outlet of the first throttle valve 205, the first oil outlet of the hydraulic lock 208 is communicated with the second oil chamber of the second hydraulic cylinder 129, the second oil inlet of the hydraulic lock 208 is communicated with the oil outlet of the second throttle valve 206, and the second oil outlet of the hydraulic lock 208 is communicated with the first oil chamber of the second hydraulic cylinder 129.

The third directional valve 207 is a cartridge type two-position three-way valve. Specifically, the third directional valve 207 includes a seventh directional valve assembly 119, an eighth directional valve assembly 120, and a fifth electromagnetic directional valve 215, a working oil port a of the eighth directional valve assembly 120 and an oil inlet P of the fifth electromagnetic directional valve 215 communicate with the main oil passage 300, a working oil port a and a working oil port B of the fifth electromagnetic directional valve 215 communicate with a control oil port X of the seventh directional valve assembly 119 and a control oil port X of the eighth directional valve assembly 120, respectively, the working oil port a of the seventh directional valve assembly 119 and the working oil port B of the eighth directional valve assembly 120 communicate with the hydraulic lock 208, and an oil return port T of the fifth electromagnetic directional valve assembly 215 and the working oil port B of the seventh directional valve assembly 119 communicate with the oil return tank.

The hydraulic lock 208 is a plug-in type bidirectional hydraulic lock. The hydraulic lock 208 comprises a first pressure valve assembly 121, a second pressure valve assembly 122, a first shuttle valve 216 and a second shuttle valve 217, a first oil inlet of the hydraulic lock 208 is a working oil port a of the first pressure valve assembly 121, a first oil outlet of the hydraulic lock 208 is a working oil port B of the first pressure valve assembly 121, a second oil inlet of the hydraulic lock 208 is a working oil port a of the second pressure valve assembly 122, a second oil outlet of the hydraulic lock 208 is a working oil port B of the second pressure valve assembly 122, the first shuttle valve 216 is connected to a control oil port of the first pressure valve assembly 121, the second shuttle valve 217 is connected to a control oil port of the second pressure valve assembly 122, and control ends of the first shuttle valve 216 and the second shuttle valve 217 are both communicated with the third reversing valve 207.

In this embodiment, the first branch oil passage 310 is further provided with a first relief valve 124 and a first pressure gauge 126, and the second branch oil passage 320 is further provided with a second relief valve 125 and a second pressure gauge 127.

In this embodiment, the main oil path 300 is further provided with an unloading valve 202, and the unloading valve 202 is a cartridge type pressure control valve and includes a pressure valve assembly 105, a sixth electromagnetic directional valve 106, and a third relief valve 107. The working oil port a of the pressure valve assembly 105 is communicated with the main oil path 300, the sixth electromagnetic directional valve 106 is a pilot valve of the pressure valve assembly 105 and is a two-position two-way electromagnetic valve, one oil port of the sixth electromagnetic directional valve 106 is communicated with the control oil port of the pressure valve assembly 105, the oil inlet of the third overflow valve 107 is connected to the oil path between the sixth electromagnetic directional valve 106 and the pressure valve assembly 105, and the other oil port of the sixth electromagnetic directional valve 106 and the oil outlet of the third overflow valve 107 are communicated with the oil return tank.

Further, the main oil path 300 is provided with a third pressure gauge 104, a cartridge check valve 108, a pressure sensor 109 and a fine filter 110.

In this embodiment, the hydraulic pump 102 is a fixed displacement pump, which is more easily adapted to realize the stepped adjustment function of the speed and the acting force of the hydraulic system, and is suitable for the severe environment, and a variable displacement pump with a complex structure and a high cost is not required, so that the failure rate of the hydraulic pump can be reduced, and the service life of the system can be prolonged. Of course, other embodiments may employ variable displacement pumps.

In this embodiment, the first hydraulic cylinder 128 and the second hydraulic cylinder 129 share the same cylinder head and cylinder bottom. The large-diameter hydraulic cylinder (the second hydraulic cylinder 129) and the small-diameter hydraulic cylinder (the first hydraulic cylinder 128) are connected in parallel to form the integrated double-rod hydraulic cylinder, so that the effects of heavy load, low speed, light load and high speed are realized through the on-off combination of oil holes of the double-rod hydraulic cylinder under the condition of using the fixed displacement pump, a large-area oil cylinder and a variable displacement pump are not required, and the installation space is reduced.

In this embodiment, the first oil chamber of first hydraulic cylinder 128 and the first oil chamber of second hydraulic cylinder 129 are rod-type chambers, and the second oil chamber of first hydraulic cylinder 128 and the second oil chamber of second hydraulic cylinder 129 are rodless chambers, but the invention is not limited thereto. When the first reversing valve 203 is switched on, the hydraulic reversing valve 123 works at the left position, oil is fed into a rod cavity of the first hydraulic cylinder 128 and returned into a rodless cavity of the first hydraulic cylinder 128, and a piston rod of the first hydraulic cylinder 128 retracts; when the second reversing valve 204 is switched on, the hydraulic reversing valve 123 works at the right position, oil is fed into the rodless cavity of the first hydraulic cylinder 128 and returned into the rod cavity of the first hydraulic cylinder 128, the piston rod of the first hydraulic cylinder 128 extends out, and the piston rod of the second hydraulic cylinder 129 moves along with the piston rod. When the first throttle valve 205 is turned on, the rod cavity of the second hydraulic cylinder 129 is fed with oil, the rodless cavity of the second hydraulic cylinder 129 is fed with oil, and the piston rod of the second hydraulic cylinder 129 is retracted; when the second throttle 206 is opened, the rodless chamber of the second hydraulic cylinder 129 is filled with oil, the rod chamber of the second hydraulic cylinder 129 is filled with oil, the piston rod of the second hydraulic cylinder 129 is extended, and the piston rod of the first hydraulic cylinder 128 moves.

Further, the first hydraulic cylinder 128 and the second hydraulic cylinder 129 may adopt a form of a fixed cylinder tube and a movable piston rod, or a form of a fixed piston rod and a movable cylinder tube, and the first hydraulic cylinder 128 and the second hydraulic cylinder 129 also adopt a form of parallel connection of two double-rod hydraulic cylinders.

The invention also relates to a control method of the hydraulic system with adjustable speed and acting force, which is used for controlling the hydraulic system with adjustable speed and acting force, and the control method comprises the following steps:

when the piston rod of the hydraulic cylinder needs to extend, and the speed and acting force of the hydraulic system are adjustable under light load, the oil feeding of the second oil cavity (rodless cavity) of the first hydraulic cylinder 128 is controlled, or the oil feeding of the second oil cavity (rodless cavity) of the second hydraulic cylinder 129 is controlled; during heavy loads of the hydraulic system with adjustable speed and force, controlling the second oil chamber (rodless chamber) of first hydraulic cylinder 128 to be filled with oil or controlling the second oil chamber (rodless chamber) of second hydraulic cylinder 129 to be filled with oil, or controlling the second oil chamber (rodless chamber) of first hydraulic cylinder 128 and the second oil chamber (rodless chamber) of second hydraulic cylinder 129 to be filled with oil simultaneously;

when the piston rod of the hydraulic cylinder needs to retract, and the speed and acting force adjustable hydraulic system is in light load, controlling the first oil cavity (rod cavity) of the first hydraulic cylinder 128 to be fed with oil or controlling the first oil cavity (rod cavity) of the second hydraulic cylinder 129 to be fed with oil; during heavy loads in a hydraulic system with adjustable speed and force, first chamber (stick chamber) of first hydraulic cylinder 128 is controlled to be filled or first chamber (stick chamber) of second hydraulic cylinder 129 is controlled to be filled, or first chamber (stick chamber) of first hydraulic cylinder 128 and first chamber (stick chamber) of second hydraulic cylinder 129 are controlled to be filled simultaneously.

Specifically, as shown in fig. 3, when the hydraulic cylinders are required to move to the left, that is, the piston rods of the two hydraulic cylinders are in an extended state, the electromagnet 6Y is energized, and the hydraulic oil passes through the third directional control valve 207 to make the hydraulic lock 208 conduct reversely. Two speeds of operation may be selected at light load, i.e., second oil chamber (rodless chamber) of second cylinder 129 or second oil chamber (rodless chamber) of first cylinder 128. Taking the oil inlet of the second oil cavity (rodless cavity) of the first hydraulic cylinder 128 as an example, the electromagnet 3Y is powered on, hydraulic oil drives the hydraulic reversing valve 123 to work at the right position through the second reversing valve 204, so that pressure oil enters the second oil cavity (rodless cavity) of the first hydraulic cylinder 128 to drive the first hydraulic cylinder 128 to move to a specified position quickly, at the moment, the second hydraulic cylinder 129 moves along with the first hydraulic cylinder 128, the second oil cavity (rodless cavity) of the second hydraulic cylinder 129 is in a negative pressure state, and oil is absorbed from the oil tank and supplemented through the hydraulic lock 208.

When the hydraulic cylinder is required to output acting force during heavy load, the hydraulic cylinder can output three acting forces, namely, oil is fed into the second oil chamber (rodless chamber) of the second hydraulic cylinder 129, oil is fed into the second oil chamber (rodless chamber) of the first hydraulic cylinder 128, or oil is fed into the second oil chambers (rodless chambers) of the two hydraulic cylinders simultaneously. Because the second oil chamber (rodless chamber) of the second hydraulic cylinder 129 has a large enough acting area, the external load can be driven only by supplying oil to the second oil chamber (rodless chamber) of the second hydraulic cylinder 129, at this time, in the working state of the hydraulic pump 102, the electromagnet 3Y is de-energized, the electromagnet 4Y is energized, the pressure oil enters the second oil chamber (rodless chamber) of the second hydraulic cylinder 129 through the first throttle valve 205 and the first pressure valve assembly 121, the oil in the first oil chamber (rod chamber) of the second hydraulic cylinder 129 returns to the oil tank through the second pressure valve assembly 122 and the second throttle valve assembly 118, the hydraulic control reversing valve 123 is in the middle position, so that the two oil chambers of the first hydraulic cylinder 128 are communicated with the oil tank, the first hydraulic cylinder 128 is in a follow-up state, the hydraulic oil drives the piston of the second hydraulic cylinder 129 to move, and the piston rods of the two hydraulic cylinders extend together, so as to overcome the heavy load by the output acting force of the hydraulic cylinders.

In the starting or pressure maintaining stage, the electromagnet 1Y is powered on, all other electromagnets are in a power-off state, the sixth electromagnetic directional valve 106 works at the right position, the control oil port X of the pressure valve assembly 105 is communicated with the oil tank through the sixth electromagnetic directional valve 106, oil output by the hydraulic pump 102 flows back to the oil tank through the pressure valve assembly 105 and the sixth electromagnetic directional valve 106, and the hydraulic pump 102 is started in an idle load mode or the unloading of the hydraulic pump 102 is realized.

The invention also relates to engineering machinery comprising the hydraulic system with adjustable speed and acting force. The construction machine is, for example, a press machine, a tractor, a molding machine, or the like. Other configurations of the work machine are known to those skilled in the art and will not be described herein.

1. the hydraulic system with adjustable speed and acting force adopts a large-diameter hydraulic cylinder (a second hydraulic cylinder) and a small-diameter hydraulic cylinder (a first hydraulic cylinder) which are connected in parallel to form an integral double-rod hydraulic cylinder, and the speed and acting force of the system are adjusted in a stepping mode through the on-off combination of all oil holes under the condition that a constant delivery pump is used, so that the effects of heavy load, low speed and light load and high speed are achieved, the synchronization effect is good, and the hydraulic system can be suitable for the severe environment.

4. The parallel double hydraulic cylinders (the first hydraulic cylinder and the second hydraulic cylinder) are respectively controlled by independent loops, so that the control is convenient and flexible; furthermore, the system is provided with an unloading loop, so that the reactive loss and the heating of an oil source during waiting are reduced; and moreover, outlet throttling speed regulation and a hydraulic reversing valve are adopted, so that the stability of the system is improved, and the system is suitable for the working condition of negative load.

The hydraulic system with adjustable speed and acting force, the control method thereof and the engineering machinery provided by the invention are described in detail, specific examples are applied in the description to explain the principle and the implementation mode of the invention, and the description of the embodiments is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed, and in summary, the content of the present specification should not be construed as a limitation to the present invention.

Claims

1. A hydraulic system with adjustable speed and acting force comprises an oil tank (101), a hydraulic pump (102) connected with the oil tank (101), and a motor (103) for driving the hydraulic pump (102), and is characterized by further comprising a hydraulic reversing valve (123), a first reversing valve (203), a second reversing valve (204), a first throttle valve (205), a second throttle valve (206), a first hydraulic cylinder (128) and a second hydraulic cylinder (129); piston rods of the first hydraulic cylinder (128) and the second hydraulic cylinder (129) are arranged in parallel and move synchronously towards the same direction, and the inner diameter of the first hydraulic cylinder (128) is smaller than that of the second hydraulic cylinder (129);

the hydraulic pump (102) is connected to the first hydraulic cylinder (128) and the second hydraulic cylinder (129) through a main oil passage (300); an oil inlet of the hydraulic reversing valve (123) is communicated with the main oil path (300), two working oil ports of the hydraulic reversing valve (123) are respectively communicated with a first oil chamber and a second oil chamber of the first hydraulic cylinder (128), oil inlets of the first reversing valve (203) and the second reversing valve (204) are communicated with the main oil path (300), and oil outlets of the first reversing valve (203) and the second reversing valve (204) are respectively communicated to two hydraulic control ends of the hydraulic reversing valve (123);

oil inlets of the first throttle valve (205) and the second throttle valve (206) are communicated with the main oil passage (300), an oil outlet of the first throttle valve (205) is communicated to a second oil chamber of the second hydraulic cylinder (129) through a first oil dividing passage (310), and an oil outlet of the second throttle valve (206) is communicated to a first oil chamber of the second hydraulic cylinder (129) through a second oil dividing passage (320).

2. The hydraulic system with adjustable speed and acting force according to claim 1, wherein the first directional valve (203) comprises a first directional valve assembly (111), a second directional valve assembly (112) and a first electromagnetic directional valve (211), a working oil port B of the second directional valve assembly (112) and an oil inlet P of the first electromagnetic directional valve (211) are communicated with the main oil path (300), a working oil port A and a working oil port B of the first electromagnetic directional valve (211) are respectively communicated with a control oil port X of the first directional valve assembly (111) and a control oil port X of the second directional valve assembly (112), the working oil port A of the first directional valve assembly (111) and the working oil port A of the second directional valve assembly (112) are communicated with one of hydraulic control ends of the hydraulic directional valve (123), and an oil return port T of the first electromagnetic directional valve (211) and the working oil port B of the first directional valve assembly (111) are communicated with an oil return tank; the second reversing valve (204) comprises a third directional valve component (113), a fourth directional valve component (114) and a second electromagnetic reversing valve (212), a working oil port B of the third directional valve component (113) and an oil inlet P of the second electromagnetic reversing valve (212) are communicated with the main oil circuit (300), a working oil port A and a working oil port B of the second electromagnetic reversing valve (212) are respectively communicated with a control oil port X of the third directional valve component (113) and a control oil port X of the fourth directional valve component (114), the working oil port A of the third directional valve component (113) and the working oil port A of the fourth directional valve component (114) are communicated with the other hydraulic control end of the hydraulic reversing valve (123), and an oil return port T of the second electromagnetic reversing valve (212) and the working oil port B of the fourth directional valve component (114) are communicated with an oil return tank.

3. The hydraulic system with adjustable speed and acting force according to claim 1, wherein the first throttle valve (205) comprises a first throttle valve assembly (115), a fifth directional valve assembly (116) and a third electromagnetic directional valve (213), a working oil port B of the fifth directional valve assembly (116) and an oil inlet P of the third electromagnetic directional valve (213) are communicated with the main oil path (300), a working oil port a and a working oil port B of the third electromagnetic directional valve (213) are respectively communicated with a control oil port X of the first throttle valve assembly (115) and a control oil port X of the fifth directional valve assembly (116), the working oil port a of the first throttle valve assembly (115) and the working oil port a of the fifth directional valve assembly (116) are communicated with a second oil chamber of the second hydraulic cylinder (129) through the first oil distribution path (310), and a return oil port T of the third electromagnetic directional valve (213) and the working oil port B of the first throttle valve assembly (115) are communicated with a return oil chamber; the second throttle valve (206) comprises a fifth directional valve assembly (117), a second throttle valve assembly (118) and a fourth electromagnetic directional valve (214), a working oil port B of the fifth directional valve assembly (117) and an oil inlet P of the fourth electromagnetic directional valve (214) are communicated with the main oil path (300), a working oil port a and a working oil port B of the fourth electromagnetic directional valve (214) are respectively communicated with a control oil port X of the fifth directional valve assembly (117) and a control oil port X of the second throttle valve assembly (118), the working oil port a of the fifth directional valve assembly (117) and the working oil port a of the second throttle valve assembly (118) are communicated with a first oil chamber of the second hydraulic cylinder (129) through the second branch oil path (320), and an oil return port T of the fourth electromagnetic directional valve (214) and the working oil port B of the second throttle valve assembly (118) are communicated with an oil return tank.

4. The adjustable speed and force hydraulic system of claim 1, further comprising a third directional control valve (207) and a hydraulic lock (208); the hydraulic lock (208) is provided with a first oil inlet, a second oil inlet, a first oil outlet and a second oil outlet, wherein the first oil inlet and the first oil outlet are located on the first oil dividing path (310), the second oil inlet and the second oil outlet are located on the second oil dividing path (320), the first oil inlet of the hydraulic lock (208) is communicated with the oil outlet of the first throttle valve (205), the first oil outlet of the hydraulic lock (208) is communicated with the second oil chamber of the second hydraulic cylinder (129), the second oil inlet of the hydraulic lock (208) is communicated with the oil outlet of the second throttle valve (206), and the second oil outlet of the hydraulic lock (208) is communicated with the first oil chamber of the second hydraulic cylinder (129).

5. The hydraulic system with adjustable speed and acting force according to claim 4, wherein the third directional valve (207) comprises a seventh directional valve assembly (119), an eighth directional valve assembly (120) and a fifth electromagnetic directional valve (215), a working oil port A of the eighth directional valve assembly (120) and an oil inlet P of the fifth electromagnetic directional valve (215) are communicated with the main oil passage (300), a working oil port A and a working oil port B of the fifth electromagnetic directional valve (215) are respectively communicated with a control oil port X of the seventh directional valve assembly (119) and a control oil port X of the eighth directional valve assembly (120), the working oil port A of the seventh directional valve assembly (119) and a working oil port B of the eighth directional valve assembly (120) are communicated with the hydraulic lock (208), and an oil return port T of the fifth electromagnetic directional valve (215) and the working oil port B of the seventh directional valve assembly (119) are communicated with an oil return tank; the hydraulic lock (208) comprises a first pressure valve assembly (121), a second pressure valve assembly (122), a first shuttle valve (216) and a second shuttle valve (217), a first oil inlet of the hydraulic lock (208) is a working oil port A of the first pressure valve assembly (121), a first oil outlet of the hydraulic lock (208) is a working oil port B of the first pressure valve assembly (121), a second oil inlet of the hydraulic lock (208) is a working oil port A of the second pressure valve assembly (122), a second oil outlet of the hydraulic lock (208) is a working oil port B of the second pressure valve assembly (122), the first shuttle valve (216) is connected to a control oil port of the first pressure valve assembly (121), the second shuttle valve (217) is connected to a control oil port of the second pressure valve assembly (122), and control ends of the first shuttle valve (216) and the second shuttle valve (217) are communicated with the third reversing valve (207).

6. The hydraulic system with adjustable speed and acting force according to claim 1, characterized in that the first oil distribution passage (310) is further provided with a first overflow valve (124) and a first pressure gauge (126), and the second oil distribution passage (320) is further provided with a second overflow valve (125) and a second pressure gauge (127).

7. The hydraulic system with adjustable speed and acting force according to claim 1, characterized in that an unloading valve (202) is further arranged on the main oil path (300), and the unloading valve (202) comprises a pressure valve assembly (105), a sixth electromagnetic directional valve (106) and a third overflow valve (107); the main oil way (300) is also provided with a third pressure gauge (104), a plug-in type one-way valve (108), a pressure sensor (109) and a fine filter (110); the hydraulic pump (102) is a fixed displacement pump.

8. Hydraulic system adjustable in speed and effort according to claim 1, characterized in that the first hydraulic cylinder (128) shares the same cylinder head and cylinder bottom as the second hydraulic cylinder (129).

9. A method for controlling a hydraulic system with adjustable speed and force, characterized in that the method is used for controlling a hydraulic system with adjustable speed and force according to any one of claims 1 to 8, and the method comprises:

when a piston rod of the hydraulic cylinder needs to extend, controlling the oil inlet of a second oil cavity of the first hydraulic cylinder (128) or controlling the oil inlet of a second oil cavity of the second hydraulic cylinder (129) when the speed and acting force adjustable hydraulic system is in light load; when the speed and acting force adjustable hydraulic system is heavily loaded, controlling the second oil cavity of the first hydraulic cylinder (128) to be filled with oil or controlling the second oil cavity of the second hydraulic cylinder (129) to be filled with oil, or controlling the second oil cavity of the first hydraulic cylinder (128) and the second oil cavity of the second hydraulic cylinder (129) to be filled with oil simultaneously;

when a piston rod of the hydraulic cylinder needs to retract, controlling the first oil cavity of the first hydraulic cylinder (128) to be filled with oil or controlling the first oil cavity of the second hydraulic cylinder (129) to be filled with oil when the speed and acting force adjustable hydraulic system is in light load; when the speed and acting force adjustable hydraulic system is in a heavy load state, controlling the first oil cavity of the first hydraulic cylinder (128) to be fed with oil or controlling the first oil cavity of the second hydraulic cylinder (129) to be fed with oil, or controlling the first oil cavity of the first hydraulic cylinder (128) and the first oil cavity of the second hydraulic cylinder (129) to be simultaneously fed with oil.

10. A working machine comprising a speed and force adjustable hydraulic system according to any one of claims 1-8.