JPH06330901A - Flow rate control device - Google Patents

Abstract

PURPOSE:To provide a flow rate control device which can easily acquire a rate-of-flow characteristic to suit actuators of various type through modifying of the uniform flow rate characteristic of conventional rate-of-flow control devices and is adaptive to the load sensing control capable of altering the actuator speed to different levels between at the time with low load and with high load. CONSTITUTION:A hydraulic circuit to perform load sensing control is equipped with a variable capacity type hydraulic pump 1 and a plurality of actuators 10, 11, and in this hydraulic circuit flow rate control devices 6, 9 are furnished which consist of variable throttle parts 4, 7 and pressure compensation parts 34, 35, wherein further introduction lines 30, 31 are furnished to introduce the max. load pressure of a maximum load pressure sensing circuit 16, and these lines are equipped with decompression valves 32, 33 which decompressingly correct the max. load pressure. Thereby the max. load pressure decompressively corrected is led to the pressure compensation parts 34, 35 so that thereto a control force in the direction of closing is given, and the throttle pre-pose differential pressure of the variable throttle parts 4, 7 is corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate control device adapted to a hydraulic circuit for controlling the drive of an actuator of a hydraulic machine to perform load sensing control, and more particularly to a construction machine such as a hydraulic excavator or a hydraulic crane. It is useful for

[0002]

2. Description of the Related Art In a hydraulic circuit that simultaneously drives appropriate ones of a plurality of actuators by the hydraulic pressure of a hydraulic pump, that is, in a hydraulic circuit that compositely drives actuators, all the compositely driven actuators are driven smoothly. In order to do so, it is necessary to constantly supply sufficient hydraulic pressure to drive the most loaded of these actuators. Therefore, in such a hydraulic circuit, control called load sensing control is performed. Load sensing control is, to put it simply, in a hydraulic circuit having such an actuator that is driven in combination, the maximum load pressure is detected from the load pressure of the actuator that is driven in combination, and the discharge pressure of the hydraulic pump is It refers to a control system that controls the discharge capacity of the hydraulic pump so that it is higher than the maximum load pressure by a predetermined value. By adopting such a control method, not only sufficient hydraulic pressure is supplied to each actuator, but also the hydraulic pump constantly supplies the hydraulic pressure to a necessary limit, and it is possible to suppress the power consumption low. Become.

However, in the hydraulic circuit for performing load sensing control, when hydraulic pressure is introduced from the main pipeline through the branch passage without providing the hydraulic fluid distribution means, the hydraulic fluid is guided to the actuator having a lower load. There is a tendency, and the appropriate allocation cannot be made. Therefore, in such a hydraulic circuit, a flow rate control device that is means for appropriately distributing pressure oil to each actuator is provided.

Below, these technical contents will be described in detail with reference to FIG. FIG. 6 is a hydraulic circuit diagram of a conventional example showing an example of a hydraulic circuit for performing load sensing control provided with a conventional general flow rate control device.

Reference numeral 1 is a variable displacement hydraulic pump, 2 is a displacement control device provided in the pump 1 and having a function of adjusting the discharge capacity and thus the discharge pressure of the pump 1, as will be described later.
Is a main conduit which is a conduit connected to the discharge port of the pump 1. Numerals 4 and 7 are variable throttle portions having a valve opening degree given by an operator who operates the hydraulic machine and having a function of flowing a flow rate proportional to the valve opening degree. Is a spring for presetting the oil passages of the pressure compensating units 5, 8 to be closed, and 6, 9 are the variable throttle unit 4 and the pressure compensating unit. 5, a variable flow restrictor 7 and a pressure compensator 8 respectively. In these flow rate control devices 6 and 9, the variable throttle unit 4 and the pressure compensating unit 5 and the variable throttle unit 7 and the pressure compensating unit 8 are separately shown in FIG. 6 for the sake of convenience. As a group of different types of functional parts, they form an inseparable valve unit. Actuators 10 and 11 are respectively controlled by the flow rate control devices 6 and 9, and in the case of a hydraulic excavator as an example, devices such as hydraulic cylinders that rotate an arm and a boom, and 12 and 13 are actuators 10 and 11 respectively. A load pipe branched from the main pipe 3 connecting the main pipe 3 with the main pipe 3, a check valve 14 and 15, and a higher load pressure among the load pressures of the actuators 10 and 11 of the load pipes 12 and 13, that is, It is a maximum load pressure detection path through which the maximum load pressure is guided, and guides the maximum load pressure to the tilt control device 2. The maximum load pressure detection path 16 is connected to the load pipelines 12 and 13 by the connection pipelines 14A and 15A, respectively, but since the maximum load pressure detection pathway 16 is connected via the check valves 14 and 15, respectively, the pressure oil is changed. Load pipeline 12,1
The reverse flow to 3 is blocked by each of these check valves 14 and 15, and the maximum load pressure detection path 1 is
When the higher load pressure of the actuators 10 and 11 is guided to 6, the lower load pressure cannot be guided as a natural result. As a result, during the combined drive of these actuators 10 and 11, the higher load pressure of these load pressures is always selected and guided to the maximum load pressure detection path 16. 17 is a pressure compensator 5
The maximum load pressure of the maximum load pressure detecting path 16 is guided to the pressure compensating section 5 by the signal line of the same compensating section 5 which connects between the maximum load pressure detecting path 16 and the maximum load pressure detecting path 16 via a part of the connecting pipeline 14A. For example, a control force in the closing direction is applied together with the spring 5A so as to close a variable orifice provided in the pressure compensator 5. Reference numeral 18 denotes a signal conduit of the pressure compensating unit 5 that guides the downstream pressure of the variable throttle unit 4, and guides the downstream pressure to the pressure compensating unit 5 to apply a control force in the opening direction to the pressure compensating unit 5. The pressure compensating section 5 adjusts the opening amount by the control force in the closing direction and the opening direction to control the differential pressure across the variable throttle section 4 before and after the throttle to a constant value. Reference numeral 19 is a signal conduit of the compensator 8 which connects the pressure compensator 8 and the maximum load pressure detection path 16 through a part of the connection conduit 15A and guides the maximum load pressure in the same manner as the signal conduit 17. A control force in the closing direction is applied to the compensator 8 together with the spring 8A. Reference numeral 20 is the variable throttle unit 7 as in the signal line 18.
In the signal line of the pressure compensating unit 8 that guides the downstream pressure of
A control force in the opening direction is applied to. Similar to the pressure compensating unit 5, the pressure compensating unit 8 has a structure in which the opening amount thereof is constantly adjusted by the control force in the closing direction and the opening direction so that the differential pressure across the variable throttle unit 7 is always constant. Has become.

Reference numeral 21 is a pressure control valve called an unload valve, which is used when the variable throttles 4 and 7 of the flow control devices 6 and 9 are not operated and the actuators 10 and 11 are not driven. When the pressure of 3 reaches a predetermined value, the discharge oil of the variable displacement hydraulic pump 1 is directly returned to the tank to put the pump 1 into an unloaded state to save power. Reference numeral 22 denotes a discharge pressure detection path that connects the tilt control device 2 and the main pipe 3, and guides the discharge pressure of the variable displacement hydraulic pump 1 to the tilt control device 2.

Based on the above hydraulic circuit, first,
The load sensing control will be described.

Now, when the variable displacement hydraulic pump 1 is operated and the variable throttle portions 4 and 7 are operated by the operator, hydraulic pressure is introduced to the actuators 10 and 11 through the main pipeline 3 and the load pipelines 12 and 13, respectively. Assuming that these are combinedly driven, the higher load pressure among the load pressures of the actuators 10 and 11, that is, the maximum load pressure is the load pipelines 12 and 1.
3 is led to the maximum load pressure detection path 16 through any one of the connecting conduits 14A and 15A provided with the check valves 14 and 15, and further to the tilting control device 2. On the other hand, the discharge pressure of the variable displacement hydraulic pump 1 is also guided from the main pipe 3 to the tilt control device 2 through the discharge pressure detection passage 22. Then, the displacement control device 2 has means for controlling the displacement of the variable displacement hydraulic pump 1 based on these pressure signals, so that the discharge pressure of the pump 1 has a predetermined value, that is, a so-called so-called maximum load pressure. The displacement of the pump 1 is controlled so as to decrease the discharge capacity of the pump 1 when the pressure is higher than the pressure to which the load sensing differential pressure is applied and increase it when the pressure is low. As a result, the variable displacement hydraulic pump 1 has its discharge capacity controlled so that its discharge pressure is higher than the maximum load pressure by a predetermined value, and so-called load sensing control is performed.

Next, the operation of the conventional flow rate control device will be described based on the hydraulic circuit of FIG. 6 for performing such load sensing control.

Now, assuming that the load sensing control is performed and the actuators 10 and 11 are driven in combination, the maximum load pressure of the maximum load detection path 16 is passed through the signal lines 17 and 19 to the pressure compensating portions 5 and 5, respectively. 8 is applied to each of the springs 8A and 8B to apply a control force in the closing direction together with the springs 5A and 8A
On the other hand, the downstream pressures of the variable throttle units 4 and 7 are
The control force in the opening direction is given by being guided to the pressure compensating units 5 and 8 through 20, respectively. Then, the variable diaphragm unit 4,
If the downstream pressure of 7 is higher than a predetermined value considering the maximum load pressure and the spring force, the control force in the opening direction overcomes the control force in the closing direction to open the variable orifices of the pressure compensating units 5 and 8, The actuators 10 and 11 are supplied with sufficient hydraulic pressure to drive them. In such a state, if the downstream pressure further increases, the pressure compensator 5,
The reference numeral 8 self-adjusts the opening amount so as to enlarge the variable orifice to reduce the downstream pressure, and conversely, when the downstream pressure is to be reduced, the variable orifice is reduced so that the downstream pressure is increased. Self-adjust the amount. Thus, the downstream pressure of the variable throttle portions 4 and 7 is slightly higher than the maximum load pressure without being affected by the load fluctuation of the actuators 10 and 11 due to the pressure adjusting function of the pressure compensating portions 5 and 8. The pressure will always be maintained. That is, the differential pressure across the variable throttles 4 and 7 is combined with the control of the discharge pressure of the variable displacement hydraulic pump 1 by the load sensing control, the opening of the variable throttles 4 and 7, and the actuator 1.
The pressure compensation is performed so that it is always constant without being affected by the load variations of 0 and 11. As a result, the inherent disadvantage of the variable throttle units 4 and 7 that the flow rate changes if the differential pressure across the throttle varies even when the opening is constant is overcome. The flow rate can be adjusted to a constant value according to the opening degree without being affected by pressure fluctuations.

Therefore, in order to explain this more accurately, when expressed by a mathematical expression, first, in the pressure compensating portions 5 and 8, the pressures on the downstream side of the variable throttle portions 4 and 7 formed on the upstream sides thereof, respectively. Pz _i is controlled so as to follow the equation (1).

Pz _i = Plmax + k / A (Z _i + Zo _i ) = Plmax + Co _i ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (1) The meanings of the symbols in the equation (1) are as follows.

Pz _i ; Downstream pressure of each variable throttle portion Plmax; Maximum load pressure A; Pressure receiving area of each pressure compensation portion regarding Pz _i , Plmax k; Spring constant Z _i ; Displacement of each pressure compensation portion Zo _i ; Each pressure Initial displacement of compensator Co _i ; constant And, in addition, Zo _i is, to put it simply, a preset force of a spring for presetting to close the oil passages of the pressure compensators 5 and 8, and Z _i Is a force required to open the control force in the closing direction of the pressure compensating portions 5 and 8 such as the spring force to open it to a predetermined opening.

On the other hand, the discharge pressure Ps of the variable displacement hydraulic pump 1 for supplying pressure oil to the upstream side of the variable throttle parts 4 and 7 is higher than the maximum load pressure Plmax as shown in the equation (2) by the load sensing control. The pressure is adjusted so as to be increased by a predetermined specified value, that is, the load sensing differential pressure ΔP _LS , and the pressure Ps, that is, Plmax + ΔP _LS , becomes the upstream pressure of the variable throttle portions 4 and 7.

Ps = Plmax + ΔP _LS (2) Then, the variable throttle parts 4 and 7 of the flow rate control devices 6 and 9, respectively.
Any In a state where the valve opening is given, these diaphragm differential pressure Ps-Pz _i, the (1), (2) from equation always load sensing differential pressure as shown in both (3) A constant value close to ΔP _LS will be maintained.

Ps−Pz _i = (Plmax + ΔP _LS ) − (Plmax
+ Co _i ) = ΔP _LS −Co _i ≈ΔP _LS (3) That is, the differential pressure across the variable throttle parts 4 and 7 is as shown by the broken line in FIG. Pressure compensation is performed so as to maintain a pressure substantially equal to the load sensing differential pressure ΔP _LS regardless of changes in the load pressure. As a result, the inflow flow rate Q _i of the variable throttle portions 4 and 7 can be set to a value proportional to the valve opening degree of each variable throttle portion as shown in the equation (4). , A constant value can be maintained without being affected by load fluctuations.

Q _i = N · A _i √ (Ps−Pz _i ) = N · A _i √ (ΔP _LS ) .... is there.

Q _i ; inflow flow rate of each variable throttle unit A _i ; each variable throttle valve opening degree N; constant A conventional hydraulic circuit used for load sensing control having a plurality of such actuators. As is clear from the above description, in the flow control device of No. 2, the differential pressure across the variable throttle unit is the same for all actuators and is always constant regardless of the magnitude of the load pressure.

[0019]

However, in such a conventional flow rate control device, if it is used as it is, only uniform flow rate characteristics can be obtained, and flow rate characteristics suitable for each actuator can be obtained. I can't. Therefore,
Conventionally, in order to obtain such flow rate characteristics, it has been unavoidable to prepare various flow rate control devices of different standards by designing the valve opening of the variable throttle portion differently for each actuator. It was For example, taking a hydraulic excavator as an example, the boom, arm, and bucket cylinders that are one of its actuators have different diameters, different operating speeds per unit flow rate, and different desired operating speed regions. In order for each of these cylinders to obtain an operating speed in an appropriate range, it is necessary to have a wide variety of valve unit products for flow rate control devices with variable throttles of different designs, which is what we call the so-called high-mix low-volume production. There was a problem in terms of production efficiency.

Further, in the conventional flow rate control device, the differential pressure across the variable throttle portion is constant regardless of the magnitude of the load, and the flow rate is always kept constant. Therefore, the actuator is operated under light load or heavy load. It is not possible to adjust the speed of the robot to an appropriate value.Therefore, depending on the type of work performed by each actuator, work efficiency is improved, or its operation is made comfortable for the operator. It was also difficult to measure the improvement of sex. For example, like a hydraulic excavator, in addition to simple excavation and loading of earth and sand, leveling the ground, leveling horizontal and slopes for leveling, excavating grooves accurately, scouring gravel uniformly For machines that perform a variety of work, such as slicing, and performing different types of construction work, such as replacing the bucket with another attachment, depending on the size of the load, that is, the type of work. It is necessary to increase the speed of the actuator to a high level in order to improve the operability, or to set the speed to a low level in order to improve the operability. It is difficult for the flow rate control device to meet such a request.

The present invention solves the problems of the prior art as described above and can easily obtain the flow rate characteristics suitable for various actuators by modifying the uniform flow rate characteristics in the conventional flow rate control device. In addition to improving production efficiency, it is possible to change the speed of the actuator to different levels under low load and high load to improve workability and operability, and a flow control device suitable for load sensing control. It is intended to provide.

[0022]

The above objects of the present invention are as follows:
It has a variable displacement hydraulic pump and multiple actuators that are driven by the hydraulic pressure of the pump. The maximum load pressure is detected from the load pressures of these actuators, and the discharge pressure of the variable displacement hydraulic pump is the maximum load. It is provided in the hydraulic circuit that performs load sensing control that controls the discharge capacity of the pump so that it is higher than the pressure by a predetermined value.The variable throttle section and the pressure based on the downstream pressure and the maximum load pressure of the variable throttle section respectively In a flow rate control device including a pressure compensating unit for controlling the opening amount by controlling force in the opening direction and the closing direction to control the opening amount and controlling the differential pressure across the throttling of the variable throttling unit, a pipe line for leading the maximum load pressure is provided. A pressure reducing valve for reducing the maximum load pressure is provided in the same line, and as a signal line for guiding the pressure for applying a control force in the closing direction to the pressure compensator,
At least a signal line for introducing a corrected maximum load pressure for guiding the maximum load pressure corrected by the pressure reducing valve to the pressure compensator is provided.
Can be achieved by a flow control device as described in.

[0023]

As described above, the flow rate control device of the present invention is provided in a hydraulic circuit for performing load sensing control having a variable displacement hydraulic pump and a plurality of actuators, and comprises a variable throttle part and a pressure compensating part. In particular,
At least a signal conduit for guiding the pressure for applying a closing direction control force to the pressure compensator is provided as a signal conduit for providing the maximum load pressure and a pressure reducing valve for reducing the maximum load pressure in the same conduit. Since the signal line for introducing the corrected maximum load pressure that guides the maximum load pressure corrected by the pressure reducing valve to the pressure compensation unit is provided, at least the corrected maximum load is provided in the pressure compensation unit. The maximum load pressure corrected by the pressure reducing valve is introduced through the signal line for pressure introduction,
As a result, the uniform flow rate characteristic of the conventional flow rate control device can be corrected with a predetermined tendency, and can also be corrected according to the magnitude of the load on the actuator.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A basic embodiment of the present invention will be described with reference to FIGS.

First, the first embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 is a hydraulic circuit diagram showing the first embodiment of the flow rate control device of the present invention, and the same reference numerals as those in FIG. The part marked with represents the same part as in the figure, so
These parts will not be described in detail in order to avoid redundant description.

As is apparent from FIG. 1, the hydraulic circuit of FIG. 1 has a variable displacement hydraulic pump 1, a tilting control device 2 having a function of adjusting the displacement of the pump 1, and the pump 1.
A plurality of actuators 10, 11 driven by
It has a maximum load pressure detection path 16 through which the maximum load pressure is guided among the load pressures of these actuators 10 and 11, and the maximum load pressure causes the maximum displacement pressure of the variable displacement hydraulic pump 1 through the tilt control device 2. The hydraulic pressure of FIG. 6 provided with a conventional flow rate control device is that load discharge control is performed by controlling the discharge capacity of the pump 1 so as to be higher than the load pressure by a predetermined value. It is no different from the circuit. Further, on the discharge side of the variable displacement hydraulic pump 1, control forces in the opening direction and the closing direction are respectively applied by the variable throttle portions 4, 7 and the pressures based on the downstream pressure and the maximum load pressure to adjust the opening amount. 6 in that a flow rate control device for controlling the actuators 10 and 11 is also provided, which is composed of a pressure compensator that controls the differential pressure across the variable throttles 4 and 7. There is.

Therefore, the structure of the flow rate control device which is an improvement point according to the present invention will be described based on the first embodiment. Reference numerals 30 and 31 respectively connect the maximum load pressure detection path 16 and the tank. Introducing pipelines connected through a part of the pipelines 14A and 15A, and 32 and 33 are pressure reducing valves provided in the introducing pipelines 30 and 31, respectively, and introduced through the introducing pipelines 30 and 31, respectively. The function of correcting the maximum load pressure value of the maximum load pressure detection path 16 is fulfilled. Reference numerals 34 and 35 are pressure compensators, 34A and 35A are springs having the same functions as the springs 5A and 8A in FIG. 6, and 36 and 37 are signal conduits for introducing the corrected maximum load pressure. Each of these signal conduits 36, 37 introduces the maximum load pressure introduced into each of the introduction conduits 30, 31 and corrected by each pressure reducing valve 32, 33 into each pressure compensator 34, 3 respectively.
5, the control force in the closing direction is applied to these. In the first embodiment of the present invention, these signal conduits 3 are used as the signal conduits that apply the control force in the closing direction to the pressure compensators 34 and 35.
6, 37, the signal line 17 in the conventional example of FIG.
19 is also provided, and a signal line for guiding the pressure compensation units 34 and 35 without correcting the maximum load pressure is added. Therefore, roughly speaking, in the first embodiment, the control force in the closing direction tends to be strengthened, and in response to this, the control force in the opening direction is applied to the pressure compensating portions 34 and 35. The pressure of the signal lines 18, 20, that is, the variable throttle portion 4,
The downstream pressure of 7 also tends to increase, and as a result, the differential pressure across the variable throttles 4 and 7 tends to decrease, and flow rate characteristics tending to suppress the inflow rate of the variable throttles.

Therefore, in order to accurately represent this flow rate characteristic, a mathematical expression will be explained. For example, the pressure reducing valves 32 and 33 provided as shown in FIG. Assuming that it is a pressure reducing valve that reduces the pressure at a predetermined ratio with respect to the pressure on the inlet side, first, each pressure reducing valve
The pressure Pc _i on the outlet side, which is decompressed by 2, 33, is derived as follows and is expressed by the equation (5).

A _i · Plmax = b _i · Pc _i + k ′ (y + y ₀ ) ∴Pc _i = a _i / b _i · Plmax−k ′ / b _i (y + y ₀ ) ≈α _i · Plmax ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (5) The meanings of the symbols other than the above-mentioned symbols in the equation (5) are as follows.

Pc _i ; pressure on the outlet side of each pressure reducing valve a _i ; pressure receiving area of each pressure reducing valve on the control signal pressure on the inlet side (Plmax) b _i ; each pressure reducing valve on the control signal pressure on the outlet side (Pc _i ) Pressure receiving area k ′; spring constant of a spring for presetting the pressure reducing valve y; displacement of each pressure reducing valve (a force similar to Z _i in the formula (1) due to the spring) y ₀ ; initial of each pressure reducing valve Displacement (also Zo in the previous equation (1)
A _i ); Pressure receiving area ratio of each pressure reducing valve with respect to control signal pressure (a
_i / b _i ) As is clear from the equation (5), if each pressure reducing valve 32, 33 is such a constant ratio pressure reducing valve, the maximum load pressure P
lmax is reduced at the pressure receiving area ratio α _i , and the reduced pressure is the pressure Pc _i on the outlet side of each pressure reducing valve 32, 33.
Then, the signal is introduced to the respective pressure compensators 34 and 35 through the signal conduits 36 and 37 for introducing the corrected maximum load pressure.

In the pressure compensators 34 and 35, the pressure Pc _i on the outlet side of each of the pressure reducing valves 32 and 33 is introduced as the pressure for applying the control force in the closing direction. Since the maximum load pressure Plmax is also introduced through the signal lines 17 and 19, respectively, the downstream pressure Pz _i of each variable throttle section 4 and 7 on the upstream side of the pressure compensating section 34 and 35 is controlled so as to follow the equation (6). .

Pz _i = Pc _i + Plmax + k ′ / A (Z _i + Zo _i ) = α _i · Plmax + Plmax + k ′ / A (Z _i + Zo _i ) ≈ (1 + α _i ) Plmax + Co _i ‥‥‥‥‥‥‥‥‥‥‥‥ (6) On the other hand, the discharge pressure Ps of the variable displacement pump 1 that supplies pressure oil to the upstream side of the variable throttle parts 4 and 7 is Plmax + ΔP as shown in the above equation (2) by load sensing control.
From being adjusted so as to _LS, in the state where any of the valve opening is variable throttle portion 4,7 of the flow control device 6 and 9 are given, these diaphragm differential pressure Ps-Pz _i ,
From the expressions (2) and (6), the control is performed as shown in the expression (7).

Ps−Pz _i = (Plmax + ΔP _LS ) −
_{[(1 + α i) Plmax +} Co i ] _{= ΔP LS -α i · Plmax-} Co i ≒ ΔP LS -α i · Plmax ‥‥‥‥‥ (7) The symbol alpha _i of the (7) wherein the above As described above, the pressure receiving area ratio (a _i / b _i ) is a positive constant.

[0034] To illustrate the diaphragm differential pressure Ps-Pz _i, any diaphragm differential pressure across the variable throttle portion 4,7 also, FIG. 5
As shown by the solid line in the first embodiment, the load pressure tends to decrease as the load pressure increases. As a result, the inflow flow rate Q _i of the variable throttle portions 4 and 7 is corrected so as to have a flow rate characteristic that is proportional to the opening degree of each variable throttle portion and has a priority when the load is light, as shown in the equation (8). it can.

Q _i = N · A _i √ (ΔP _LS −α _i · Plmax) (8) Further, the proportional constant α _i in the equation (8) is apparent from the above description. In addition, the pressure receiving areas a _i and b _{i of the} pressure reducing valve relating to the control signal pressures on the inlet side and the outlet side are
Since it is a constant determined by, the flow rate characteristic can be arbitrarily set and changed simply by appropriately adjusting the ratio of these pressure receiving areas a _i and b _i. As long as the actuator requires
Optimal flow rate characteristics can be easily obtained for each actuator.

As is clear from the equation (8), according to the first embodiment, the flow rate can be suppressed consistently, and the flow rate can be made larger at light load than at heavy load. The characteristics can be obtained.

Next, a second embodiment of the present invention will be described with reference to FIG. 2. FIG. 2 is a hydraulic circuit diagram showing a second embodiment of the flow rate control device of the present invention. Since the parts denoted by the same reference numerals represent the same or equivalent parts in these drawings, these parts will not be described in detail to avoid duplication of description.

As is apparent from FIG. 2, the hydraulic circuit of FIG. 2 is different from that of FIG. 1 in that the signal lines 17 and 19 as in the conventional example of FIG. The only difference is that it is not provided. Therefore, in FIG. 2, the load sensing control is performed, and on the discharge side of the variable displacement pump 1, the variable throttle unit 4,
7 and a pressure compensator for controlling the opening / closing differential pressure of the variable throttle parts 4, 7 by applying control forces in the opening direction and the closing direction by the pressures based on the downstream pressure and the maximum load pressure, respectively. 6 is similar to that of FIG. 1 in that a flow rate control device for controlling each of the actuators 10 and 11 is provided.

Therefore, comparing the flow control device of the second embodiment and the flow control device of the first embodiment with respect to the structure of the flow control device of the improvement of the present invention, the flow control of the second embodiment will be described. The apparatus is provided with introduction pipes 30 and 31 for guiding the maximum load pressure of the maximum load pressure detection passage 16, and pressure reducing valves 32 and 33 are provided to the introduction pipes 30 and 31, respectively. The flow rate of the first embodiment is that the corrected maximum load pressure is guided to the pressure compensating portions 34 and 35 by the signal conduits 36 and 37, respectively, and a control force in the closing direction is applied to these. There is basically no difference from the control device, and when using such a configuration, the first
In the embodiment, the signal line 1 that directly leads the maximum load pressure
7 and 19 are added, the second embodiment is different from the second embodiment in that such a thing is not added.

In the second embodiment, except for the forces of the springs 34A and 35A, only the corrected maximum load pressure, that is, the reduced maximum load pressure is used as the closing direction control force.
Since the control force in the closing direction tends to be weakened by being imparted to the valve Nos. 4 and 35, the downstream pressures of the variable throttle units 4 and 7 also tend to decrease in response to this, and as a result, the variable throttle units are reduced. The differential pressures across the throttles 4 and 7 tend to increase, and flow rate characteristics tending to increase the flow rate flowing into the variable throttle portion are obtained.

In order to accurately express the flow rate characteristic, a mathematical expression will be described. It is assumed that the pressure reducing valves 32 and 33 provided as shown in FIG. 2 are constant ratio pressure reducing valves as in the first embodiment. Then, first, the pressure Pc _i on the outlet side, which is decompressed by the pressure reducing valves 32 and 33, is as shown in the above equation (5), and therefore, in the pressure compensating units 34 and 35, the variable throttle units on the upstream side thereof are used. The downstream pressures Pz _{i of} 4 and 7 are controlled so as to follow the equation (9).

Pz _i = Pc _i + k / A (Z _i + Zo _i ) ≈α _i · Plmax + Co _i (9) On the other hand, a variable displacement type that supplies pressure oil to the upstream side of the variable throttle units 4 and 7. The discharge pressure Ps of the pump 1 is Plmax + ΔP as shown in the above equation (2) by the load sensing control.
From being adjusted so as to _LS, in the state where any opening in variable throttle portion 4,7 of the flow control device 6 and 9 are given, these diaphragm differential pressure Ps-Pz _i, From the expressions (2) and (9), the control is performed as shown in the expression (10).

Ps−Pz _i = (Plmax + ΔP _LS ) − (α _i · Pl
_{max + Co i) = ΔP LS} + (1-α i) Plmax-Co i ≒ ΔP LS + α 'i · Plmax ‥‥‥‥‥‥ (10) The symbol alpha of the equation (10)' _i is the equation (1-
α _i ) is simply replaced, and this α ' _i
Specifically, the pressure receiving area ratio α _i (a _i / b _i ) is
This is a coefficient by which the maximum load pressure Plmax is corrected to reduce the pressure, and is naturally a positive constant smaller than 1. Therefore, 0 <(1-α _i ) <1 and this (1-α _i ).
Α ′ _i, which is a replacement of, can be regarded as a positive constant smaller than 1.

[0044] To illustrate the diaphragm differential pressure Ps-Pz _i, any diaphragm differential pressure across the variable throttle portion 4,7 also, FIG. 5
There is a tendency for the pressure to increase as the load pressure increases as indicated by the alternate long and short dash line in the second embodiment. As a result, the variable diaphragm unit 4,
As shown in the equation (11), the inflow flow rate Qi of No. 7 is proportional to each variable throttle opening and can be modified to have a preferential flow rate characteristic under heavy load.

Q _i = N · A _i √ (ΔP _LS + α ′ _i · Plmax) (11) Then, the proportional constant α ′ _i in the equation (11) is (8)
Like α _i in the equation, it is a constant determined by the pressure receiving areas a _i and b _i of the pressure reducing valve relating to the control signal pressures on the inlet side and the outlet side. _Since it is possible to arbitrarily set and change the ratio of _i and b _i by appropriately adjusting the ratio, it is possible to easily obtain the optimum flow rate characteristic for each actuator as long as the actuator requires this type of flow rate characteristic. You can

As is apparent from the equation (11), according to the second embodiment, the flow rate can be consistently increased, and the flow rate can be increased at heavy load rather than at light load. The characteristics can be obtained.

Although the flow rate control devices used in the first and second embodiments described above are different from each other in the mode of operation, they are the same as those in which a pipe line for leading the maximum load pressure is provided. The line is equipped with a pressure reducing valve for reducing the maximum load pressure, and the maximum load pressure corrected by the pressure reducing valve is guided to the pressure compensator to give a control force in the closing direction. With this configuration as a base, it is possible to modify the uniform flow rate characteristics of the conventional flow rate control device with a predetermined tendency, and to always correct regardless of the load of the actuator. The flow rate of the conventional flow rate control device, which is kept constant, can be modified according to the magnitude of the load. As a result, it is possible to easily obtain the flow rate characteristics suitable for various actuators by simply changing the existing hydraulic circuit for load sensing control without changing the basic structure of the conventional flow rate control device. Therefore, it is not necessary to have a variety of valve unit products with variable throttles of different designs, as in the conventional flow control device, and it is possible to improve the production efficiency and to reduce the load between light load and heavy load. With this, the speed of the actuator can be changed to a different level, and the workability and operability can be improved.

The embodiment which is the basis of the present invention has been described above. Based on the configuration of the hydraulic circuit shown in FIGS. 1 and 2,
By using a variable pressure reducing valve as a pressure reducing valve that is provided in a pipe line that guides the highest load pressure and reduces and corrects the maximum load pressure, the tendency of the flow rate characteristics of the first embodiment and the second embodiment can be reduced to the basic characteristics. It is possible to obtain a flow rate control device that can be changed in multiple steps without changing the value. Further, the variable pressure reducing valve having a predetermined structure is controlled by the controller so that the flow rate characteristics of the first embodiment and the conventional example can be selectively obtained, or the second embodiment and the conventional example. It is also possible to selectively obtain the flow rate characteristic of.

Hereinafter, the more concrete embodiments of the present invention will be described as the third and fourth embodiments of the present invention, and will be described with reference to FIGS. 3 and 4. To do. 3 is a hydraulic circuit diagram showing a third embodiment of the flow rate control device of the present invention, and FIG. 4 is a hydraulic circuit diagram showing a fourth embodiment of the flow rate control device of the present invention. Among the reference numerals attached to these drawings, the portions attached with the same reference numerals as those in FIGS. 1, 2 and 6 represent the same or equivalent portions as those in these three drawings, and therefore these portions will be described in the description. Details are omitted to avoid duplication.

First, a third embodiment of the present invention will be described with reference to FIG. 3. Reference numerals 40 and 41 are electromagnetic variable pressure reducing valves provided in the introducing pipes 30 and 31, respectively.
The value of the maximum load pressure Plmax of the maximum load pressure detection path 16 introduced through 0, 31 can be variably reduced and corrected. Reference numeral 42 denotes a controller for controlling these electromagnetic variable pressure reducing valves 40 and 41.
0 and 41 are respectively operated by electric signals output from the controller 42, and are controlled so that the pressure on the outlet side thereof becomes a desired reduced pressure value. Further, these electromagnetic variable pressure reducing valves 40, 41 have a structure in which pressure oil on the outlet side (secondary side) is released to the tank as shown in the figure when an electric signal is not output from the controller 42. Since all the pressure oil in the signal line 36, 37 for introducing the corrected load pressure is released to the tank, the pressure for applying the control force in the closing direction is applied to the pressure compensator 34, 35 through the signal line 36, 37. Will not be guided to. In the flow rate control device of the present embodiment, the electromagnetic variable pressure reducing valves 40 and 41 having such a structure are used for the pressure reducing valves 32 and 33 provided in the introduction pipe lines 30 and 31, respectively, in the first embodiment. The electromagnetic variable pressure reducing valves 40 and 41 are each controlled by the controller 42.

Since the flow rate control device of the third embodiment has such a structure, when an electric signal is output from the controller 42 to any of the electromagnetic variable pressure reducing valves 40 and 41,
The maximum load pressure is guided to the pressure compensating sections 34 and 35 through the signal lines 17 and 19, and the maximum load pressure corrected by the pressure reducing valve is also guided to the pressure compensating section through any of the signal pipelines 36 and 37. Among the flow rate control devices 6 and 9, the flow rate control device related to the pressure compensating unit in which the corrected maximum load pressure is guided by the output of the electric signal has the same flow rate characteristic as in the first embodiment, Other flow control devices
It has the same flow rate characteristic as the conventional example. In addition, when an electric signal is output from the controller 42 to the electromagnetic variable pressure reducing valves 40 and 41, the pressure on the outlet side is appropriately controlled by the output value, the tendency of the flow rate characteristic of the first embodiment becomes a basic characteristic. Can be changed in multiple steps without changing. As is apparent from the present embodiment, the variable pressure reducing valves 32 and 33 in the first embodiment can be changed to a variable pressure reducing valve.
It is possible to obtain a flow rate control device that can be appropriately adjusted so that the flow rate characteristics of the embodiment of FIG. A variable pressure reducing valve having a structure in which pressure oil on the outlet side is released to the tank can be embodied in a flow rate control device capable of selectively obtaining the flow rate characteristic of the first embodiment or the flow rate characteristic of the conventional example. In the third embodiment, the signal lines 17 and 19 for guiding the maximum load pressure are opened and closed to close the outlet side (secondary side).
By providing an opening / closing means such as an electromagnetic switching valve for releasing the pressure oil of the above, to the tank, the electromagnetic variable pressure reducing valve from the controller 42 is operated while the opening / closing means such as the electromagnetic switching valve is closed. By outputting electric signals to 40 and 41,
In addition to the above flow rate characteristics, the flow rate characteristics of the second embodiment can be obtained.

Next, a fourth embodiment of the present invention will be described with reference to FIG. 4. The flow rate control device of the present embodiment is provided in each of the introduction pipe lines 30 and 31 in the second embodiment. The same electromagnetic variable pressure reducing valves 40, 41 as those in the third embodiment are used as the pressure reducing valves 32, 33, and these electromagnetic variable pressure reducing valves 40, 41 are controlled by the controller 42, respectively. Therefore, the flow rate control device of the present embodiment is different from that of the third embodiment in that the signal line 1 that guides the maximum load pressure to the pressure compensating portions 34 and 35 as it is.
The embodiment is different only in that 7, 19 are not added.

Since the flow rate control device of the fourth embodiment has such a structure, when an electric signal is outputted from the controller 42 to the electromagnetic variable pressure reducing valves 40, 41, the output value of the outlet side of the controller 42 is determined by the output value thereof. By properly controlling the pressure, the tendency of the flow rate characteristic of the second embodiment can be changed in multiple stages without changing the basic characteristic. Further, when controlling the pressure on the outlet side of the pressure reducing valves 40, 41 by the output value of the controller 42, if the pressure on the outlet side of any one of them is controlled to be the maximum, the pressure on the outlet side of the pressure reducing valve is controlled. Is equal to the maximum load pressure. As a result, the pressure equal to the maximum load pressure is introduced to the pressure compensating section through one of the signal lines 36 and 37, and the pressure equal to the maximum load pressure of the flow control devices 6 and 9 is introduced. The flow rate control device for the compensator has the same flow rate characteristic as the conventional example, and the other flow rate control devices have the same flow rate characteristic as the second embodiment. As is apparent from the present embodiment, only by changing the pressure reducing valves 32 and 33 in the second embodiment to variable pressure reducing valves, the flow rate characteristics of the second embodiment are appropriately adjusted so as to have a desired tendency. In addition, the present invention can be embodied in a flow rate control device capable of selectively obtaining the flow rate characteristic of the second embodiment or the flow rate characteristic of the conventional example. In the third and fourth embodiments, an electromagnetic type variable pressure reducing valve is used, but it is of course possible to use an electromagnetic pilot type one.

According to the third embodiment and the fourth embodiment, the flow rate characteristics of the first embodiment and the second embodiment can be appropriately adjusted so as to have desired tendencies. In addition, the flow characteristics of the conventional example and the flow characteristics of the first embodiment,
Since a desired one can be selectively obtained from the flow rate characteristics of the conventional example and the flow rate characteristic of the second embodiment, standard work can be performed by selecting the flow rate characteristic of the conventional example, and the actuators 10 and 11 can be used. In order to improve operability, for example, the flow rate characteristic of the first embodiment may be selected according to the content of the work to be performed, the type of attachment to be replaced with the main work machine, and the individual aspect of the work by these devices. , Selecting the flow rate characteristic of the second embodiment to improve workability, selecting the optimum flow rate characteristic according to the type of work and the phase of the work, and further, the tendency of the selected flow rate characteristic By appropriately adjusting so as to optimize the flow rate, it is possible to obtain a flow control device which is easier to use than the conventional one. Therefore, when the flow control device of the present invention is practically embodied, if such a configuration is adopted and an appropriate design is applied, it can be used for various work equipment in various ways and contributes to the improvement of its steering performance. Can be expected.

Further, in the third and fourth embodiments, since the variable pressure reducing valve is operated by the controller 42 in particular, the respective actuators 10, 11 are
The necessary data is stored in the data section of the controller 42 so that the optimum flow rate characteristics can be selected according to the type of work of various work equipment provided in the above and the phase of each work, and the actuators 10, 11 and work equipment are stored. Necessary detection signal for detecting the actual operation state of the actuator, for example, a detection signal for detecting the self-load pressure of each actuator 10, 11, and further a detection signal for detecting the operation displacement state of the actuator 10, 11. The output for properly operating each electromagnetic variable pressure reducing valve 40, 41 is determined by the arithmetic unit of the controller 42, and the electromagnetic variable pressure reducing valve of each of these is output as an electric signal from the output unit. Four
It is output to 0, 41. Therefore, in the third and fourth embodiments, if the software is prepared, it becomes possible to automatically select the flow rate characteristics according to the type of various working machines and the work phase. It is possible to provide a compatible general-purpose flow rate control device.

As described above, it is useful when embodying the constitution of the present invention which can selectively obtain at least two kinds of flow rate characteristics among the flow rate characteristics of the first embodiment, the second embodiment and the conventional example. Although the configuration of the simple flow rate control device has been described by exemplifying the third embodiment and the fourth embodiment, the conditions for selecting these flow rate characteristics are designed in accordance with the type of work equipment, work content, and the like. It can be arbitrarily selected. Further, the selection can be made not only automatically by using various control mechanisms, but also manually depending on the experience of the operator in some cases. In the third and fourth embodiments, the same basic flow rate characteristics are used for the flow rate control devices 34, 35 for controlling the actuators 10, 11, but separate flow rate characteristics are used. Of course, it is possible.

Therefore, the main points in the configuration of the flow rate control device described above are that the pressure reducing valve for reducing the maximum load pressure is a variable pressure reducing valve, and further, the variable pressure reducing valve is controlled by a controller. In this way, the tendency of the flow rate characteristics of the first and second embodiments can be changed in multiple steps without changing the basic characteristics. It is possible to selectively obtain at least two kinds of flow rate characteristics among the flow rate characteristics of the working example, the second working example, and the conventional example, and further contribute to improvement of workability and operability of various working equipment. be able to.

[0058]

As is apparent from the above description, the present invention is provided in a hydraulic circuit for carrying out load sensing control having a variable displacement hydraulic pump and a plurality of actuators, as described in the claims. In a flow rate control device including a variable throttle section and a pressure compensating section, in particular, a pipeline for guiding the maximum load pressure is provided and a pressure reducing valve for reducing the maximum load pressure is provided in the pipeline, and the pressure compensating section is closed. As a signal conduit for guiding the pressure for applying the control force of the above, at least a signal conduit for introducing the corrected maximum load pressure for guiding the maximum load pressure corrected by the pressure reducing valve to the pressure compensator is provided. Since it is equipped with the conventional control device, it is possible to modify the uniform flow rate characteristic of the conventional control device with a predetermined tendency, and to change the speed of the actuator at light load and heavy load. It is possible to change the level,
As a result, flow rate characteristics suitable for various actuators can be easily obtained by a simple modification of the hydraulic circuit, production efficiency can be improved, and workability and operability can be improved.

As described above, the present invention improves the conventional flow rate control device, which is supposed to be controlled by the maximum load pressure, with the idea that the maximum load pressure itself is corrected by the pressure reducing valve. The idea is gradual.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing a first embodiment of a flow rate control device of the present invention.

FIG. 2 is a hydraulic circuit diagram showing a second embodiment of the flow rate control device of the present invention.

FIG. 3 is a hydraulic circuit diagram showing a third embodiment of the flow rate control device of the invention.

FIG. 4 is a hydraulic circuit diagram showing a fourth embodiment of the flow rate control device of the invention.

FIG. 5 is a characteristic diagram relating to flow control devices of the present invention and a conventional example.

FIG. 6 is a hydraulic circuit diagram of a conventional example.

[Explanation of symbols] 1 Variable displacement hydraulic pump 2 Tilt control device 3 Main line 4,7 Variable throttle part 6,9 Flow rate control device 10,11 Actuator 12,13 Load line 14,15 Check valve 16 Maximum load pressure Detection line 17,19 Signal line 18,20 Signal line 22 Discharge pressure detection line 30,31 Inlet line 32,33 Pressure reducing valve 34,35 Pressure compensator 36,37 Signal line 40,41 Electromagnetic variable pressure reducing valve 42 Controller

Claims (3)

[Claims] 1. A variable displacement hydraulic pump comprising: a variable displacement hydraulic pump; and a plurality of actuators driven by the hydraulic pressure of the pump. The maximum load pressure among the load pressures of these actuators is detected to discharge the variable displacement hydraulic pump. Is provided in the hydraulic circuit that performs load sensing control that controls the discharge capacity of the pump so that the pressure becomes higher than the maximum load pressure by a predetermined value. The maximum load pressure is derived in the flow rate control device including a pressure compensating unit for controlling the opening / closing differential pressure of the variable throttle unit by applying control forces in the opening direction and the closing direction respectively by the pressure based on A pressure reducing valve for reducing the maximum load pressure is installed in the pipeline and the signal line for guiding the pressure to apply control force in the closing direction to the pressure compensator is used as a signal pipeline. A flow control device is characterized in that a signal pipe line for introducing a corrected maximum load pressure for guiding the maximum load pressure corrected by the pressure reducing valve to the pressure compensating section is provided. 2. The flow control device according to claim 1, wherein the pressure reducing valve is a constant ratio pressure reducing valve. 3. The flow control device according to claim 1, wherein the pressure reducing valve is a variable pressure reducing valve, and is operated by an electric signal output from a controller for controlling the variable pressure reducing valve.