CN212838654U

CN212838654U - Hydraulic drive system

Info

Publication number: CN212838654U
Application number: CN202020819855.8U
Authority: CN
Inventors: 汪立平; 高雪涛; 韩日升; 刘红光; 杨泽贺
Original assignee: Jiangsu Hengli Hydraulic Technology Co Ltd
Current assignee: Jiangsu Hengli Hydraulic Technology Co Ltd
Priority date: 2020-05-15
Filing date: 2020-05-15
Publication date: 2021-03-30
Anticipated expiration: 2030-05-15

Abstract

The utility model relates to a hydraulic pressure field, concretely relates to hydraulic drive system. A hydraulic drive system comprising: a hydraulic pump that pumps out working oil; an actuator that is operated by a supply of working oil from the hydraulic pump; control valves provided for the actuators, each of the control valves operating supply of the hydraulic oil from the hydraulic pump to the corresponding actuator to control operation of the corresponding actuator; the working oil pumped out by the hydraulic pump can directly return oil through the unloading oil way, and the unloading oil way is provided with an unloading valve; and the controller controls the displacement of the hydraulic pump, the opening and closing of the unloading valve and the reversing of the control valve. The technical problems that pressure loss is easily caused by the fact that a load sensitive control system is adopted by a main control valve in the prior art, and the structure of an open center control system is complex are solved.

Description

Hydraulic drive system

Technical Field

The utility model relates to a hydraulic pressure field, concretely relates to hydraulic drive system.

Background

Current main control valves for small excavations are generally configured in two systems: a load-sensitive control system (single pump) and an open-center control system (multi-pump system). In order to obtain good operation performance of the load sensitive control system, a fixed differential pressure reducing valve is added on an oil inlet pipeline, the fixed differential pressure reducing valve and a valve core throttling opening form a flow valve, so that the flow passing through the valve core throttling opening is only proportional to the opening area and is not related to the load, and partial pressure loss is sacrificed to obtain good operability. And in order to meet the problem of walking synchronization, the open center control system respectively controls the left and right walking motors by using two pumps, and the structure is complex.

In the prior art, the load sensitive control system needs to be provided with an LS oil way and acquire the oil pressure on the LS oil way, and the displacement adjusting structure adjusts the displacement of the hydraulic pump according to the oil pressure on the LS oil way so as to maintain the constant pressure difference between the pump outlet of the hydraulic pump and the LS oil way, namely the load sensitive control system in the prior art is not controlled quickly enough and is easy to cause pressure loss.

SUMMERY OF THE UTILITY MODEL

In order to solve the main control valve among the prior art and adopt the sensitive control system of load to cause loss of pressure easily, open the technical problem that central control system structure is complicated, the utility model provides a hydraulic drive system has solved above-mentioned technical problem. The technical scheme of the utility model as follows:

a hydraulic drive system comprising: a hydraulic pump that pumps out working oil; an actuator that is operated by a supply of working oil from the hydraulic pump; control valves provided for the actuators, each of the control valves operating supply of the hydraulic oil from the hydraulic pump to the corresponding actuator to control operation of the corresponding actuator; the unloading oil way is used for directly unloading the working oil pumped out by the hydraulic pump through the unloading oil way, and an unloading valve is arranged on the unloading oil way; and the controller controls the displacement of the hydraulic pump, the opening and closing of the unloading valve and the reversing of the control valve.

The utility model discloses a hydraulic drive system adopts the controller to carry out the electric control to the switching of the discharge capacity of hydraulic pump, off-load valve and the switching-over of control valve, and the controller can be according to the discharge capacity of the operating condition control hydraulic pump of control valve, and the reaction is rapid. When no actuating mechanism exists, each control valve is in a middle position, the controller can reduce the displacement of the hydraulic pump to the minimum, and open the unloading valve to unload the hydraulic oil pumped out by the hydraulic pump from the unloading valve at a minimum output flow rate in a low pressure manner, so that the pressure loss is greatly reduced; when the actuating mechanism acts, the unloading valve is closed, the speed of the actuating mechanism is controlled by adjusting the discharge capacity of the hydraulic pump and the control valve, and bypass throttling and overflow flow loss are avoided.

According to an embodiment of the present invention, the actuator includes an actuator i and an actuator ii, the control valve includes a control valve i and a control valve ii corresponding to the actuator i and the actuator ii, respectively, and the controller controls the control valve i and the control valve ii to be reversed.

According to the utility model discloses an embodiment, be provided with compensating valve I between control valve I and the actuator I, control valve II with be provided with compensating valve II between the actuator II.

According to the utility model discloses an embodiment, control valve I is the same with the structure of control valve II, control valve I is three-position seven-way valve, control valve I has two oil return openings T, pressure hydraulic fluid port p and four work hydraulic fluid ports a, b, c, d, and two oil return openings T and oil tank T intercommunication, pressure hydraulic fluid port p with the pump export intercommunication of hydraulic pump, work hydraulic fluid port a, d all communicate with actuator I, work hydraulic fluid port b, c with compensation valve I communicates.

According to an embodiment of the utility model, when the control valve I is positioned at the middle position, the working oil ports a and d are respectively communicated with the two oil return ports t; when the control valve I is located at two working positions, the pressure oil port p is communicated with the working oil port b, the working oil port c is respectively communicated with one of the working oil port a and the working oil port d, the other working oil port is communicated with the oil return port t, pressure oil flows out through the working oil port b, part of the pressure oil is used for pushing the valve core of the compensation valve I to slide so as to be communicated with an oil circuit inside the compensation valve I, and part of the pressure oil flows to the working oil port c through the compensation valve I and then respectively enters the actuator I through the working oil port a or the working oil port d.

According to the utility model discloses an embodiment, pressure hydraulic fluid port p with be provided with the governing valve on the oil duct of work hydraulic fluid port b intercommunication.

According to an embodiment of the utility model, the structure of the compensation valve I is the same as that of the compensation valve II, the compensation valve I is a three-position three-way valve, the compensation valve I is provided with an oil inlet and oil outlets I and II, and the oil outlets I and II are respectively communicated with an upper cavity of the working oil port c and the compensation valve I; and part of the pressure oil flowing out of the working oil port b flows to a lower cavity of the compensation valve I to drive the compensation valve I to be in a working position, and part of the pressure oil flows to the oil inlet.

According to an embodiment of the utility model, when the compensation valve I is in a first working position, the oil inlet is communicated with the oil outlet I, and an adjusting valve is arranged on an oil way of the oil inlet communicated with the oil outlet I; when the compensating valve I is located at a second working position, the oil inlet is communicated with the oil outlets I and II, and an adjusting valve is arranged on an oil way through which the oil inlet is communicated with the oil outlet II.

According to the utility model discloses an embodiment still includes the constant current oil circuit, the constant current oil circuit communicates with oil tank T, be provided with the constant current valve on the constant current oil circuit, the epicoele of two compensating valves all with the constant current oil circuit intercommunication.

According to an embodiment of the invention, the actuator further comprises an actuator iii, the hydraulic pump supplies oil to the actuator iii under control of a control valve iii, and the controller controls the control valve iii to reverse.

Based on foretell technical scheme, the utility model discloses the technological effect that can realize does:

1. the utility model discloses a hydraulic drive system adopts the controller to carry out the electric control to the switching of the discharge capacity of hydraulic pump, off-load valve and the switching-over of control valve, and the controller can be according to the discharge capacity of the operating condition control hydraulic pump of control valve, and the reaction is rapid. When no actuating mechanism exists, each control valve is in a middle position, the controller can reduce the displacement of the hydraulic pump to the minimum, and open the unloading valve to unload the hydraulic oil pumped out by the hydraulic pump from the unloading valve at a minimum output flow rate in a low pressure manner, so that the pressure loss is greatly reduced; when the actuating mechanism acts, the unloading valve is closed, the speed of the actuating mechanism is controlled by adjusting the discharge capacity of the hydraulic pump and the control valve, and bypass throttling and overflow flow loss are avoided;

2. the utility model discloses a hydraulic drive system can accomplish compound action through the actuator that sets up compound action, and through the setting to control valve and compensating valve, can realize that the flow size that gets into actuator I and actuator II can not receive the influence of load: specifically, by specifically setting the structures and the communication relations of the two control valves and the two compensation valves, when the composite action is realized, the pressure difference between two sides of the regulating valve between the pressure oil port p and the working oil port b in the two control valves is basically equal, so that the flow entering the actuator I and the actuator II is only related to the opening area of the regulating valve and the outlet pressure of the hydraulic pump. When the opening areas of the regulating valves in the two control valves are the same, the flow entering the actuator I and the flow entering the actuator II are the same, and the flow is related to the output flow of the hydraulic pump, so that the composite action synchronous control of the single-pump driving multi-execution mechanism can be realized;

3. the utility model discloses a hydraulic drive system still can include actuator III, realizes the three actuating mechanism combined action of single pump drive, and has the actuator I and the II synchronous motion of actuator of compensating valve, introduces the III commutations of control valve, because of the III commutations of control valve after, has only changed hydraulic pump output pressure, consequently gets into actuating mechanism actuator I and II flows of actuator still the same, and it is relevant only with the III loads of actuator that its size is relevant.

Drawings

Fig. 1 is a schematic view of a hydraulic drive system of the present invention;

FIG. 2 is an enlarged view of portion A of FIG. 1;

FIG. 3 is a schematic diagram of the synchronous control of the composite operation of two actuators;

FIG. 4 is a schematic diagram of the compound action of three actuators;

in the figure: 1-a hydraulic pump; 2-an actuator; 21-an actuator I; 22-actuator II; 23-an actuator iii; 3-a control valve; 31-control valve I; 32-control valve II; 33-control valve III; 4-a compensation valve; 41-compensation valve I; 42-compensation valve II; 5-unloading oil way; 51-an unloading valve; 6-a controller; 7-constant flow oil circuit; 71-a constant flow valve; 8-safety oil way; 81-safety valve; 9-adjusting valve; 10-pilot oil way.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

Unless specifically stated otherwise, the relative arrangement of the components and steps, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present invention. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the orientation words such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" etc. are usually based on the orientation or positional relationship shown in the drawings, and are only for convenience of description and simplification of description, and in the case of not making a contrary explanation, these orientation words do not indicate and imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore, should not be interpreted as limiting the scope of the present invention; the terms "inner and outer" refer to the inner and outer relative to the profile of the respective component itself.

Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may be otherwise variously oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

It should be noted that the terms "first", "second", and the like are used to define the components, and are only used for convenience of distinguishing the corresponding components, and if not stated otherwise, the terms have no special meaning, and therefore, the scope of the present invention should not be construed as being limited.

As shown in fig. 1 to 4, the present embodiment provides a hydraulic drive system including a hydraulic pump 1 and an actuator 2, the hydraulic pump 1 communicating with a tank T to pump working oil, and the actuator 2 being operated by the working oil supplied from the hydraulic pump 1. A control valve 3 is further provided between the hydraulic pump 1 and the actuator 2, and the control valve 3 is provided for the actuator 2 to control the supply of the hydraulic oil from the hydraulic pump 1 to the actuator 2 to control the operation of the corresponding actuator 2.

Specifically, the number of the hydraulic pumps 1 is 1, the actuator 2 comprises an actuator I21 and an actuator II 22 which execute compound actions, the control valve 3 comprises a control valve I31 and a control valve II 32 which respectively control oil feeding of the actuator I21 and the actuator II 22, and the actuator I21 and the actuator II 22 synchronously work under the control of the corresponding control valves. In order to realize synchronous operation of the actuator I21 and the actuator II 22, a compensation valve I41 is arranged between the actuator I21 and the control valve I31, and a compensation valve II 42 is arranged between the actuator II 22 and the control valve II 32, so that flow entering the actuator I21 and the actuator II 22 is independent of load.

The actuator I21 and the actuator II 22 have the same structure and can be hydraulic motors; the control valve I31 and the control valve II 32 are identical in structure, the compensation valve I41 and the compensation valve II 42 are identical in structure, and the communication relations between the two actuators and the corresponding control valves and compensation valves are also identical. Taking the group of the actuator I21, the control valve I31 and the compensation valve I41 as an example, the control valve I31 is a three-position seven-way valve which is provided with a pressure oil port p, two oil return ports T and four working oil ports a, b, c and d, wherein the two oil return ports T are communicated with the oil tank T, the pressure oil port p is communicated with the pump outlet of the hydraulic pump 1, the working oil ports a and d are both communicated with the actuator I21, and the working oil ports b and c are communicated with the compensation valve I41. When the control valve I31 is positioned in the middle position, the working oil ports a and d are communicated with the two oil return ports t, and the pressure oil port p and the working oil ports b and c are in a closed state; when the control valve i 31 is in the first working position (i.e., the lower position in fig. 2), the working oil port a is communicated with the oil return port t, the pressure oil port p is communicated with the working oil port b, and the working oil port c is communicated with the working oil port d; when the control valve i 31 is in the second working position (i.e., the upper position in fig. 2), the pressure port p is communicated with the working port b, the working port c is communicated with the working port a, and the working port d is communicated with the oil return port t. Preferably, when the control valve i 31 is in two working positions, the regulating valve 9 is arranged on the oil path of the pressure port p communicated with the working port b, and the flow passing through the control valve i 31 can be regulated by regulating the opening area of the regulating valve 9. The regulating valve 9 is an optional but not limited to a variable throttle.

The compensation valve I41 is a three-position three-way valve, the compensation valve I41 is provided with an oil inlet 411 and two oil outlets, the two oil outlets are respectively an oil outlet I412 and an oil outlet II 413, the oil inlet 411 of the compensation valve I41 is communicated with a working oil port b of the control valve I31, pressure oil flowing out of the working oil port b is divided into two branches, one branch of pressure oil flows to the oil inlet 411, the other branch of pressure oil flows to a lower cavity of the compensation valve I41 and is used for pushing a valve core of the compensation valve I41 to slide so that the compensation valve I41 is in a working state; the oil outlet I412 is communicated with a working oil port c of the control valve I31, and the oil outlet II 413 is communicated with the upper cavity of the compensation valve I41. When the compensation valve I41 is in an open position (namely, an upper position in FIG. 2), the oil inlet 411 is not communicated with the two oil outlets; when the compensating valve I41 is located at a first working position (namely the middle position in the figure 2), the oil inlet 411 is communicated with the oil outlet I412, and the oil outlet II 413 is disconnected; when the compensation valve i 41 is in the second working position (i.e., the lower position in fig. 2), the oil inlet 411 is in communication with both oil outlets. Preferably, in the first working position, an adjusting valve 9 is arranged on an oil path for communicating the oil inlet 411 with the oil outlet I412; in the second working position, an adjusting valve 9 is arranged on an oil path for communicating the oil inlet 411 with the oil outlet II 413. When the control valve i 31 is located at the first working position, the pressure oil pumped by the hydraulic pump 1 flows to the working oil port b through the control valve i 31, and then flows to the lower cavity of the compensation valve i 41 through the branch oil path, part of the pressure oil flows to the oil inlet 411 of the compensation valve i 41, the pressure of the lower cavity of the compensation valve i 41 is greater than that of the upper cavity, the valve element of the compensation valve i 41 slides upward, the compensation valve i 41 is located at the second working position, part of the working oil of the oil inlet 411 of the compensation valve i 41 flows to the oil outlet i 412, and then flows into the actuator i 21 through the working oil port c and the working oil port d in sequence. The regulating valve 9 in the compensating valve i 41 is also optional but not limited to a variable throttle.

In addition to the actuator i 21 and the actuator ii 22 described above, the actuator of the actuator may further include an actuator iii 23, and the hydraulic pump 1 supplies oil to the actuator iii 23 under the control of the control valve iii 33. Specifically, the control valve iii 33 is a three-position four-way valve, and when the control valve iii 33 is located at the neutral position, the hydraulic pump 1 stops supplying oil to the control valve iii 33; when the control valve iii 33 is in the two operating positions, the hydraulic pump 1 supplies oil to one chamber of the actuator iii 23 and returns oil to the other chamber. The actuator iii 23 is optional but not limited to a hydraulic cylinder. Even if the actuator III 23 is introduced, when the actuator III 23 works, only the output pressure of the hydraulic pump 1 is changed, the flow rate of the hydraulic pump into the actuator I21 and the actuator II 22 is not influenced, and the actuator I21 and the actuator II 22 can still realize synchronous control, namely, the flow rate of the hydraulic pump into the actuator I21 and the actuator II 22 is the same, and the flow rate is related to the load of the actuator III 23.

Preferably, the hydraulic drive system of this embodiment further includes a constant-flow oil path 7, the constant-flow oil path 7 is communicated with the oil tank T, a constant-flow valve 71 is disposed on the constant-flow oil path 7, the constant-flow valve 71 controls a flow rate on the constant-flow oil path 7 to be a small stable flow rate, the upper chambers of the compensation valve i 41 and the compensation valve ii 42 are both communicated with the constant-flow oil path 7, and oil pressures of the upper chambers of the compensation valve i 41 and the compensation valve ii 42 are equal.

In order to reduce pressure loss and realize low-pressure unloading, the hydraulic drive system of the embodiment further comprises an unloading oil path 5, the unloading oil path 5 is communicated with an outlet of the hydraulic pump 1 and the oil tank T, an unloading valve 51 is arranged on the unloading oil path 5, when the system does not have an actuator to work, the unloading valve 51 can be controlled to be opened, and pressure oil pumped by the hydraulic pump 1 directly returns to the oil tank T through the unloading valve 51, so that low-pressure unloading is realized.

In order to ensure the safety of the system, the hydraulic drive system of the embodiment further includes a safety oil path 8, the safety oil path 8 is communicated with the pump outlet of the hydraulic pump 1 and the oil tank T, and a safety valve 81 is arranged on the safety oil path 8 to prevent the oil pressure of the whole system from being too high.

In order to control the hydraulic drive system, the hydraulic drive system of the present embodiment further includes a controller 6, and the controller 6 is configured to control the displacement of the hydraulic pump 1, the opening and closing of the unloading valve 51, and the reversing of the control valve 3. Specifically, the hydraulic pump 1 may be a plunger pump, and the controller 6 may output a cp signal to adjust an inclination of a swash plate in the plunger pump to adjust a displacement of the hydraulic pump 1; the controller 6 can also control the opening and closing of the unloading valve 51 and the reversing of each control valve 3 by controlling the pilot oil entering the unloading valve 51 and the control valves 3, in the embodiment, the controller 6 can output a cu signal to control the opening and closing of the on-off valve I, when the on-off valve I is communicated, the pilot oil on the pilot oil path 10 can enter the pilot cavity of the unloading valve 51 through the on-off valve I, and the spool of the unloading valve 51 moves under the action of the pilot oil to open the unloading valve 51, so that the unloading of the hydraulic pump 1 can be realized; the controller 6 can output signals ca1 and cb1 to respectively control the opening and closing of the opening and closing valve II and the opening and closing valve III, and when the opening and closing valve II is opened, the pilot oil on the pilot oil path 10 can enter the lower cavity of the control valve III 33 through the opening and closing valve II; when the opening and closing valve III is opened, the pilot oil on the pilot oil path 10 can enter the upper cavity of the control valve III 33 through the opening and closing valve III, and the reversing of the control valve III 33 can be realized through the pressure of the pilot oil in the upper cavity and the lower cavity of the control valve III 33. Similarly, the controller 6 can output signals ca2 and cb2 to respectively control the opening and closing of the two opening and closing valves, and further control the reversing of the control valve I31; the controller 6 can output signals ca3 and cb3 to control the opening and closing of the two opening and closing valves respectively, and further control the reversing of the control valve II 32. When each control valve 3 is in the neutral position, that is, each actuator is not operated, the controller 6 may output a cp signal to reduce the hydraulic pump 1 to the minimum displacement, and output a cu signal to open the unloading valve 51, so that the hydraulic pump 1 is subjected to low-pressure unloading from the unloading valve 51 at the minimum output flow rate.

Based on the above structure, the working principle of the hydraulic drive system of this embodiment is:

when the actuator is not operated, namely, each control valve 3 is in a neutral position (ca1, ca2, ca3, cb1, cb2 and cb3 have no control signals), the controller 6 outputs a cp signal to reduce the hydraulic pump 1 to the minimum displacement, and outputs a cu signal to open the unloading valve 51, so that the hydraulic pump 1 is unloaded from the unloading valve 51 at the minimum output flow by low pressure;

as shown in fig. 3, when synchronous control of the actuator i 21 and the actuator ii 22 needs to be achieved, signals ca2 and ca3 output by the controller 6 drive the control valve i 31 and the control valve ii 32 to change directions, the control valve i 31 is in the first working position (i.e., the lower position in fig. 3), the control valve ii 32 is also in the first working position (i.e., the lower position in fig. 3), for the control valve i 31, the pressure oil in the pressure oil port p flows to the working oil port b through the control valve i 31, the pressure oil flowing to the working oil port b is divided into two branches, one branch enters the lower cavity of the compensation valve i 41 to drive the compensation valve i 41 to change directions, the compensation valve i 41 is in the second working position (i.e., the lower position in fig. 3), the pressure oil in the oil port i 412 enters the actuator i 21 through the working oil ports c and d, and the pressure oil in the oil port ii 413 enters the upper cavity of the compensation valve i 41. As for the control valve ii 32, the movement state is as shown in fig. 3, since the upper chamber of the compensation valve i 41 and the upper chamber of the compensation valve ii 42 are both communicated with the constant-flow oil path 7, the oil pressures of the upper chamber of the compensation valve i 41 and the upper chamber of the compensation valve ii 42 are equal, and therefore, the compensation valve ii 42 is in the first working position (i.e., the middle position in fig. 3).

In the above state, the oil pressure P1 at the pressure port of the control valve i 31 is equal to the oil pressure P2 at the pressure port of the control valve ii 32, and the oil pressure P3 in the upper chamber of the compensation valve i 41 is equal to the oil pressure P4 in the upper chamber of the compensation valve ii 42, that is, P1 is P2, and P3 is P4; for the control valve i 31, since the pressure loss from the oil inlet 411 of the compensation valve i 41 to the oil outlet ii 413 is much smaller than the pressure loss generated by the regulating valve 9 in the control valve i 31, neglecting, it can be considered that the oil pressure P5 at the oil inlet 411 of the compensation valve i 41 is approximately equal to the oil pressure at the oil outlet ii 413 of the compensation valve i 41, and the oil outlet ii 413 of the compensation valve i 41 is communicated with the upper cavity of the compensation valve ii 42, that is, P5 is P4 is P3, that is, the pressure difference generated by the variable throttling flow passage in the control valve i 31, which communicates the pressure port P and the working port b, is P1-P5; for the control valve ii 32, since the compensating valve ii 42 is in a neutral balanced state, the oil pressure P4 of the upper chamber of the compensating valve ii 42 is equal to the oil pressure P6 of the lower chamber thereof, that is, P4 is equal to P6, and the differential pressure generated by the variable throttling flow passage in the control valve ii 32, which communicates the pressure port P and the working port b, is P2-P6, as can be seen from the foregoing relationship: P1-P5-P2-P6, i.e. when the two control valves are operated synchronously, the pressure difference generated by the two control valves is basically equal, and the flow rates entering the actuator i 21 and the actuator ii 22 are only related to the opening areas of the regulating valves in the control valve i 31 and the control valve ii 32 and the pump outlet pressure of the hydraulic pump. And the inlet pressure of the regulating valves is the same, so when the opening areas of the regulating valves are the same, the flow rates entering the actuator I21 and the actuator II 22 are the same, and the flow rate is related to the flow rate output by the hydraulic pump.

As shown in fig. 4, when the compound action of the three actuators is to be realized, the controller 6 outputs ca1, ca2 and ca3 signals to drive the control valve iii 33, the control valve i 31 and the control valve ii 32 to reverse directions, the control valve iii 33, the control valve i 31 and the control valve ii 32 are all in the lower position, and the cp signal controls the pump displacement of the hydraulic pump 1. Compared with the operating mode in fig. 3, after the control valve iii 33 is reversed, only the output pressure of the hydraulic pump 1 is changed, so that the flow rates into the actuator i 21 and the actuator ii 22 are still the same, but the magnitude is related to the load of the actuator iii 23, i.e. the addition of the actuator iii 23 does not affect the synchronous control of the actuator i 21 and the actuator ii 22.

The embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art.

Claims

1. A hydraulic drive system, comprising:

a hydraulic pump (1), wherein the hydraulic pump (1) pumps working oil;

an actuator (2), the actuator (2) being operated by a supply of working oil from the hydraulic pump (1);

control valves (3) provided for the actuators (2) and configured to control the operation of the corresponding actuators (2) by operating the supply of hydraulic oil from the hydraulic pump (1) to the corresponding actuators (2);

the unloading oil way (5), the working oil pumped by the hydraulic pump (1) can be directly unloaded through the unloading oil way (5), and an unloading valve (51) is arranged on the unloading oil way (5);

and the controller (6) is used for controlling the displacement of the hydraulic pump (1), the opening and closing of the unloading valve (51) and the reversing of the control valve (3) by the controller (6).

2. A hydraulic drive system as claimed in claim 1, wherein said actuator (2) comprises an actuator i (21) and an actuator ii (22), said control valve (3) comprises a control valve i (31) and a control valve ii (32) corresponding to the actuator i (21) and the actuator ii (22), respectively, and said controller (6) controls the direction change of said control valves i (31) and ii (32).

3. A hydraulic drive system as claimed in claim 2, characterized in that a compensation valve i (41) is arranged between the control valve i (31) and the actuator i (21), and a compensation valve ii (42) is arranged between the control valve ii (32) and the actuator ii (22).

4. The hydraulic drive system as claimed in claim 3, wherein the control valve I (31) and the control valve II (32) are identical in structure, the control valve I (31) is a three-position seven-way valve, the control valve I (31) has two oil return ports T, a pressure oil port p and four working oil ports a, b, c and d, the two oil return ports T are communicated with an oil tank T, the pressure oil port p is communicated with an outlet of the hydraulic pump (1), the working oil ports a and d are both communicated with the actuator I (21), and the working oil ports b and c are communicated with the compensation valve I (41).

5. The hydraulic drive system as recited in claim 4, wherein when the control valve I (31) is located at the middle position, the working oil ports a and d are respectively communicated with the two oil return ports t; when the control valve I (31) is located at two working positions, the pressure oil port p is communicated with the working oil port b, the working oil port c is respectively communicated with one of the working oil port a and the working oil port d, the other working oil port is communicated with the oil return port t, pressure oil flows out through the working oil port b, part of the pressure oil is used for pushing the valve core of the compensation valve I (41) to slide so as to communicate with an oil circuit inside the compensation valve I (41), and part of the pressure oil flows to the working oil port c through the compensation valve I (41) and then respectively enters the actuator I (21) through the working oil port a or the working oil port d.

6. The hydraulic drive system as recited in claim 5, wherein the oil passage of the pressure port p communicating with the working port b is provided with a regulating valve (9).

7. The hydraulic driving system as claimed in claim 5 or 6, wherein the structure of the compensation valve I (41) and the structure of the compensation valve II (42) are the same, the compensation valve I (41) is a three-position three-way valve, the compensation valve I (41) has an oil inlet (411), an oil outlet I (412) and an oil outlet II (413), and the oil outlet I (412) and the oil outlet II (413) are respectively communicated with the working oil port c and the upper cavity of the compensation valve I (41); and part of the pressure oil flowing out of the working oil port b flows to a lower cavity of the compensation valve I (41) to drive the compensation valve I (41) to be in a working position, and part of the pressure oil flows to the oil inlet (411).

8. The hydraulic drive system as recited in claim 7, characterized in that when the compensation valve I (41) is in the first working position, the oil inlet (411) is communicated with the oil outlet I (412), and an adjusting valve (9) is arranged on an oil path of the oil inlet (411) communicated with the oil outlet I (412); when the compensation valve I (41) is located at a second working position, the oil inlet (411) is communicated with the oil outlet I (412) and the oil outlet II (413), and an adjusting valve (9) is arranged on an oil way through which the oil inlet (411) is communicated with the oil outlet II (413).

9. The hydraulic drive system as claimed in any one of claims 3-6 and 8, further comprising a constant-flow oil path (7), wherein the constant-flow oil path (7) is communicated with an oil tank T, a constant-flow valve (71) is arranged on the constant-flow oil path (7), and upper chambers of both the two compensation valves are communicated with the constant-flow oil path (7).

10. A hydraulic drive system according to any one of claims 3-6, 8, characterized in that the actuator (2) further comprises an actuator III (23), the hydraulic pump (1) supplying oil to the actuator III (23) under the control of a control valve III (33), the controller (6) controlling the reversal of the control valve III (33).