JP3481675B2 - Hydraulic circuit of construction machinery - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a hydraulic circuit for a construction machine,
In particular, the present invention relates to a hydraulic circuit including a relatively large inertial actuator, and further to an improvement of a hydraulic circuit capable of achieving improved combined operability and energy efficiency in such a circuit.

[0002]

2. Description of the Related Art Generally, a hydraulic circuit of a construction machine is constructed as, for example, a load sensing circuit having an auxiliary valve in order to improve operability when simultaneously driving a plurality of actuators, that is, so-called combined operability. .

FIG. 3 shows a hydraulic circuit of this type. In addition, in the illustrated example, an actuator including three actuator systems is shown. However, in FIG. 3, the discharge pressure oil is supplied from the pump line 12 of the negative control variable displacement pump 10 to the actuators 32, 34, and
36 for each branch pump line 14, 1
6, 18 and closed center type directional control valves 20, 2
2 and 24 and actuator lines 26, 28 and 30 to supply and discharge the return oil, and the return oil to the respective directional control valves 20, 22 and 24 and respective branch tank lines 38, 40 and 42, and throttle. Auxiliary valves 44, 46,
It is configured to discharge in parallel to the tank 50 via 48. Each directional valve 20, 22, 24 has a signal line 52, 54, 56 for detecting the load pressure of its corresponding actuator 32, 34, 36 and a high pressure selection of the total maximum load pressure of these load pressures. Means 58, 60
And a signal line 62 for selecting via.
As a result, in each throttle auxiliary valve 44, 46, 48, the load pressure of each corresponding actuator 32, 34, 36 in the opening direction via the respective signal line 52, 54, 56 and each spring 44a, The pressures of 46a and 48a are applied, and in the closing direction, the maximum load pressure is applied via the signal line 62, and the maximum load pressure is applied via the signal line 62.
The flow rate control means 10a is also applied. Incidentally, reference numeral 64 in the drawing indicates a relief valve.

Therefore, according to such a structure, when the directional control valves 20, 22, 24 are operated, generally, the pump oil amount corresponding to the opening is supplied to the respective actuators 32, 34, 36. Therefore, it is possible to improve the operability of the hydraulic circuit, particularly the combined operability.

[0005]

However, the conventional hydraulic circuit described above has the following drawbacks, especially when the circuit includes a relatively large inertial actuator.

That is, in the conventional hydraulic circuit (FIG. 3), for example, the actuator 32 is for turning with large inertia, and the turning actuator 32 and the small inertia actuator 34 (for boom, for example) are driven simultaneously. It is assumed that the corresponding bidirectional switching valves 20 and 22 are simultaneously operated. Immediately after this operation, even if the pressure in the pump line 12 rises, the actuator 32 does not operate immediately because of its large inertia. Therefore, the boost load pressure of the large inertia actuator 32 corresponding to the raised pressure is a signal. Corresponding dual throttle auxiliary valve 4 via line 62
It is applied to one side of 4, 46, that is, in the closing direction. However, at this time, the turning auxiliary valve 44 has the boost load pressure (and the spring 4) of the large inertia actuator 32 through the signal line 52 on the other side, that is, in the opening direction.
Since the pressure of 4a) is applied, the fully opened position is maintained, but one boom auxiliary valve 46 is
That is, in the opening direction, the load pressure of the small inertia actuator 34 (and the pressure of the spring 46a) via the signal line 54.
Is being applied. In this case, the large inertia actuator 3
Since it is clear that the boost load pressure of 2 is extremely large compared to the load pressure of the small inertia actuator 34, the auxiliary valve is extremely throttled. Therefore, the boom actuator 34 is driven only at an extremely low speed while the turning actuator 32 is accelerated to a predetermined speed (usually about 2 seconds), and energy loss occurs.

Therefore, an object of the present invention is to provide a hydraulic circuit of a construction machine composed of large-inertia and small-inertia actuators, in which the latter is not excessively decelerated at the start of a combined operation of both. To do.

[0008]

In order to achieve the above object, a hydraulic circuit of a construction machine according to the present invention divides a discharge pressure oil of a pump line of a negative control variable displacement pump into respective actuators. Supply and discharge via pump line, directional valve, actuator line,
In a hydraulic circuit of a construction machine in which the return oil is discharged to the tanks in parallel via the respective directional switching valves and branch tank lines, the directional switching valves include one open passage type with bypass passage and one or a plurality of closed passages. The open center type directional control valve is composed of a center type, and a bypass line communicating from the pump line to the tank is connected to the bypass passage, and the flow control with pressure compensation is sequentially performed on the bypass line from the upstream side. A valve and pressure generating means are provided, and the closed center type directional control valve is provided with throttle auxiliary valves on the branch tank line on the downstream side thereof, and the load pressure of the corresponding actuator is detected from the detection port. Then
Furthermore, select the maximum load pressure from these load pressures,
To the flow control valve with pressure compensation, the pressure in the upstream bypass line of the control valve is applied in the opening direction, and the maximum load pressure and the spring pressure are applied in the closing direction. Is applied with the load pressure and spring pressure of the corresponding actuator in the opening direction, and the maximum load pressure is applied in the closing direction, and the negative control variable is applied via the upstream pressure of the pressure generating means. It is characterized in that it is configured to control the displacement pump.

In this case, if necessary, an auxiliary open center type directional control valve is arranged in series on the bypass line in addition to the open center type directional control valve, and a branch pump of the open center type directional control valve is provided. The lines can be configured to be connected in parallel.

Further, in general, the open center type directional control valve can correspond to a large inertia actuator, and the closed center type directional control valve can correspond to a small inertia actuator. Furthermore, most commonly, large inertia actuators consist of swing actuators and small inertia actuators consist of booms or arcs.
It can be constructed from the beam.

[0011]

In the present invention, the pressure applied to the throttle auxiliary valve for the small inertia actuator in the closing direction is changed from the high maximum load pressure (total maximum load pressure) including the load pressure of the conventional large inertia actuator to the large inertia. It is configured to change to a low load pressure (small inertia maximum load pressure) excluding the actuator load pressure, which allows each throttle auxiliary valve for the small inertia actuator to start when the combined operation of the large inertia and small inertia actuators is started. Is held open and the variable displacement pump is configured to increase its discharge flow rate. Therefore, according to the present invention, at the start of the combined operation, first the small inertia actuator is sequentially driven with its corresponding drive pressure, and then the large inertia actuator is slowly accelerated. That is, it is possible to prevent the excessive decrease in speed of the small inertia actuator and the accompanying energy loss that have occurred in the conventional hydraulic circuit of this type.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a hydraulic circuit for a construction machine according to the present invention will be described in detail below with reference to the accompanying drawings. For convenience of explanation, the same components as those of the conventional structure shown in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

Referring to FIG. 1, the hydraulic circuit according to the present invention is basically a negative control variable displacement pump 1.
The discharge pressure oil of the pump line 12 of 0 is supplied to the respective branch pump lines 14, 16, 48 and the directional control valves 70, 22, 24 for the respective actuators 32, 34, 36.
And actuator lines 26, 28 and 30, and the return oil is supplied to and discharged from the directional control valves 70, 22, 24 and branch tank lines 38, 4 respectively.
It is configured to discharge in parallel to the tank 50 via 0 and 42. Incidentally, here, the actuator is
In practice, one relatively high inertia, most commonly pivoting actuator 32 and one or more (two in the illustrated embodiment) relatively small inertia, eg, boom and arm. Actuators 34 and 36.

In the above structure, the direction switching valve 70 of the large inertial actuator 32 system further includes the bypass passage 70.
In addition to being formed as an open center type with a, the direction switching valves 22 and 24 of the small inertia actuators 34 and 36 systems are formed as closed center types. A bypass line 72 communicating from the pump line 12 to the tank 50 is connected to the bypass passage 70a of the open center type directional control valve 70, and pressure compensation is sequentially performed on the bypass line 72 from the upstream side. A flow control valve 74 and a pressure generating means 76 are provided. Further, the closed center type directional control valves 22 and 24 are provided with throttle auxiliary valves 46 and 4 on the downstream side branch tank lines 40 and 42, respectively.
8 is provided, and from the detection ports 22a and 24a,
The load pressures of the corresponding small inertial actuators 34 and 36 are led to the signal lines 54 and 56, and the small inertial maximum load pressure is selected from the load pressures of these signal lines 54 and 56 via the high pressure selecting means 80. It is configured to lead to the small inertia maximum signal line 82. Then, the pressure compensating flow control valve 74 is applied with the pressure of the upstream bypass line of the control valve 74 through the signal line 74a in the opening direction, and the small inertia maximum signal line 82 is closed in the closing direction.
The small inertial maximum load pressure and the pressure of the spring 74b are applied via. Further, the throttle auxiliary valves 46 and 48 are applied with the load pressure of the corresponding actuators 34 and 36 and the pressures of the springs 46a and 48a in the opening direction via the signal lines 54 and 56, respectively, and are closed. The small maximum inertial load pressure is applied to each direction via the small maximum inertial signal line 82. Further, the pressure on the upstream side of the pressure generating means 76 is supplied to the flow rate controlling means 10a via the signal line 78.
The discharge flow rate of the variable displacement pump 10 is negatively controlled by reducing the discharge flow rate of the pump as the control pressure decreases.

That is, the present invention can be summarized as follows. In the above-described conventional hydraulic circuit (FIG. 3), the direction switching valve of the large inertia actuator 32 system is changed from the closed center type 20 to the open center with the bypass passage 70a. Change to the mold 70, omit the throttle auxiliary valve 44,
By providing the pressure compensating flow control valve 74 and the pressure generating means 76 on the pressure oil bypass line 72 connected to the bypass passage 70a of the direction switching valve 70, the throttle auxiliary valve 46 of the small inertia actuators 34 and 36 systems, The load pressure in the closing direction for 48 is from the conventional total maximum load pressure (maximum load pressure including the load pressure of the large inertia actuator 32) to the small inertia maximum load pressure (large inertia actuator 3).
Change to the maximum load pressure (excluding load pressure 2),
The variable displacement pump 10 is configured to be controlled by the pressure on the upstream side of the pressure generating means 76.

Therefore, the hydraulic circuit of the present invention operates as follows.

First, each actuator 32, 3
4, 36 are not driven, that is, each directional control valve 7
When 0, 22, and 24 are all in the neutral position, the signal line 5 of the closed center type directional control valves 22 and 24 is
Since pressures 4 and 56 are connected to the branch tank lines 40 and 42, respectively, the pressure in the small inertia maximum signal line 82 is kept low. Therefore, the flow control valve with pressure compensation 74 is connected to the bypass line 72 via the signal line 74a.
The pressure of the signal line 78 is maintained at a high pressure by the pressure of 1., the high pressure is guided to the flow rate control mechanism 10a of the variable displacement pump 10, and the negative control for decreasing the pump discharge flow rate when the control pressure is high. Thus, the discharge flow rate of the variable displacement pump 10 is maintained at a minimum.

Next, in the above-mentioned state, the respective directional control valves 70, 22, 24 are simultaneously operated in order to simultaneously drive the respective actuators, that is, the large inertial turning actuator 32 and the small inertia boom and arm actuators 34, 36. Suppose you want to. In this case, as mentioned above,
Since the actuator 32 does not operate immediately because of its large inertia, immediately after the above operation, the pump line 12 generates an increased pressure due to the large inertia actuator 32. However, in the present invention, this increased pressure is not affected by the throttle assist valves 46 and 48 of the small inertia actuators 34 and 36 systems, unlike the case of the above-mentioned conventional art.

That is, in the present invention, the throttle assist valves 46 and 48 of the small inertia actuators 34 and 36 systems.
As described above, the closing direction load pressure is the same as the conventional total maximum load pressure (maximum load pressure including the load pressure of the large inertia actuator 32) from the small inertia maximum load pressure (excluding the load pressure of the large inertia actuator 32). Maximum load pressure). Therefore, this load pressure is the load pressure of each corresponding small inertia actuator 34, 36 and each spring 46.
Since it corresponds to the opening direction load pressure composed of the pressures a and 48a, the throttle auxiliary valves 46 and 48 are both held in the open state. At this time, it is apparent that the pressure compensation flow control valve 74 is maintained in the open state, but since the bypass passage 70a of the directional switching valve 70 is narrowed, it is upstream of the pressure generating means 76. side pressure, i.e. the pressure signal line 78 is reduced, therefore, the discharge flow rate of the variable displacement pump 10 through a flow control mechanism 10a is negative control to increase.

As described above, in the present invention, each throttle auxiliary valve of the small inertia actuator system is held in the open state when the combined operation of the large inertia and small inertia actuators is started. That is, unlike the conventional hydraulic circuit, the variable displacement pump is not negatively controlled by the action of the large inertial actuator, and the discharge flow rate of the variable displacement pump is negatively controlled to be increased. The actuators are sequentially driven with their corresponding drive pressures, after which the large inertial actuators are slowly accelerated. Therefore, according to the present invention, the excessive speed reduction of the small inertia actuator and the accompanying energy loss as in the conventional hydraulic circuit do not occur even at the time of starting the combined operation. Therefore, combined operability and energy efficiency in this type of hydraulic circuit can be significantly improved. In the description of the above-described embodiment, it is extremely easy to understand that the same operation is performed when the small inertia actuator is only one such as a boom or an arm.

FIG. 2 shows another embodiment of the hydraulic circuit according to the present invention. In this embodiment, in addition to the open center type directional control valve (main directional control valve) 70, an auxiliary open center type directional control valve 90 is arranged in series on the bypass line 72 in the previous embodiment, A branch line (auxiliary branch line) 92 of the branch pump line 14 of the main direction switching valve 70 is connected in parallel to this. Even with such a configuration, it is clear that the same operation as in the case of the previous embodiment is performed.
With this configuration, by connecting the auxiliary actuator line 94 to the auxiliary directional control valve 90, a plurality of large-inertia and small-inertia actuators can be efficiently combined and operated with good operability, if necessary. It will be possible. In addition, the auxiliary branch line 92 can be appropriately provided with throttling means.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and many design changes can be made without departing from the spirit of the present invention.

[0023]

As described above, in the hydraulic circuit of the construction machine according to the present invention, the pump line discharge pressure oil of the negative control variable displacement pump is supplied to each actuator including the large inertia actuator. In a hydraulic circuit that supplies and discharges in parallel via a directional switching valve and its throttle auxiliary valve, the directional switching valve is formed of a bypass center open center type for a large inertia actuator and a closed center type for a small inertia actuator. For an open center type directional control valve, the throttle auxiliary valve is omitted and a flow control valve with pressure compensation and a pressure generating means are provided on the bypass line from the pump line communicating with the bypass passage to provide a closed center valve. Type directional control valve, from its detection port to the corresponding small inertia actuator The load pressure is detected and the small inertia maximum load pressure is selected from these, and the upstream pressure of this control valve is applied to the flow control valve with pressure compensation in the opening direction, and the small inertial pressure is applied in the closing direction. The maximum load pressure and spring pressure are applied, and to each throttle auxiliary valve, the corresponding small inertia actuator load pressure and spring pressure are applied in the opening direction, and the small inertia maximum load pressure is applied in the closing direction. By applying and controlling the negative control variable displacement pump via the pressure on the upstream side of the pressure generating means, in the conventional hydraulic circuit of this kind, the closing direction of the throttle valve of the small inertia actuator system is reduced. Change the load pressure from the total maximum load pressure including the conventional large inertial actuator load pressure to a low pressure small inertial maximum load pressure excluding the large inertial actuator load pressure. At the same time, the variable displacement pump is configured so that it can be controlled by the pressure on the upstream side of the pressure generating means. In addition, the variable displacement pump is controlled so that its discharge flow rate is increased. Therefore, at the time of starting the composite operation, first, the small inertia actuator is sequentially driven by the corresponding driving pressure, and then the large inertia actuator is slowly accelerated.

That is, according to the present invention, it is possible to prevent the excessive decrease in speed of the small inertia actuator and the accompanying energy loss that occur in the conventional hydraulic circuit of this type at the start of the combined operation. The present invention also has the advantage of being relatively simple to construct.

[Brief description of drawings]

FIG. 1 is a hydraulic system diagram showing an embodiment of a hydraulic circuit of a construction machine according to the present invention.

FIG. 2 is a hydraulic system diagram showing a main part of another embodiment of the hydraulic circuit of the construction machine according to the present invention.

FIG. 3 is a hydraulic system diagram showing a hydraulic circuit of a conventional construction machine.

[Explanation of symbols]

10 Variable displacement pump 10a Flow rate control mechanism 12 pump lines 14, 16, 18 Branch pump line 22, 24 Closed center type directional control valve 26, 28, 30 actuator line 32 Large inertial (swivel) actuator 34 Small inertia (boom) actuator 36 Small inertia (arm) actuator 38, 40, 42 Branch tank line 46, 48 Throttle auxiliary valve 46a, 48a spring 50 tanks 54, 56 signal line 64 relief valve 70 (Main) Open center type directional control valve 70a bypass passage 72 Bypass line 74 Flow control valve with pressure compensation 74a signal line 74b spring 76 Pressure generating means 78 signal line 80 High pressure selection means 82 Small inertia maximum signal line 90 Auxiliary open center type directional control valve 92 Auxiliary branch line 94 Auxiliary actuator line

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F15B 11/00-11/22 E02F 9/22

Claims (4)

(57) [Claims] 1. A discharge pressure oil of a pump line of a negative control variable displacement pump is supplied to and discharged from each actuator via each branch pump line, a directional control valve, and an actuator line, and the return oil is supplied to each of the above. In a hydraulic circuit of a construction machine for discharging in parallel to a tank via a directional switching valve and a branch tank line, the directional switching valve is composed of an open center type with one bypass passage and one or a plurality of closed center types. In the open center type directional control valve, a bypass line communicating from the pump line to the tank is connected to the bypass passage, and a flow control valve with pressure compensation and a pressure generating means are sequentially provided on the bypass line from the upstream side. The closed-center type directional control valve is provided with the branch tank on the downstream side thereof. Each throttle auxiliary valve is provided on the line, the load pressure of the corresponding actuator is detected from the detection port, and the maximum load pressure is selected from these load pressures. The maximum load pressure and the spring pressure are applied in the closing direction while the pressure of the upstream bypass line of the control valve is applied in the opening direction, and the actuators corresponding to the opening direction are applied to the throttle auxiliary valves. Load pressure and spring pressure are applied, and the maximum load pressure is applied in the closing direction to control the negative control variable displacement pump via the upstream pressure of the pressure generating means. A characteristic hydraulic circuit for construction machinery. 2. An auxiliary open center type directional control valve is provided in series on the bypass line in addition to the open center type directional control valve, and a branch pump line of the open center type directional control valve is connected in parallel thereto. A hydraulic circuit for a construction machine according to claim 1. 3. The hydraulic circuit for a construction machine according to claim 1, wherein the open center type directional control valve corresponds to a large inertia actuator and the closed center type directional control valve corresponds to a small inertia actuator. 4. The large inertia actuator is a swing actuator, and the small inertia actuator is a boom or an actuator.
The hydraulic circuit for a construction machine according to claim 1 , which is a boom.