JP3205910B2 - Operation control device of multiple actuators by single variable displacement pump - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an operation control device for a plurality of actuators using a single variable displacement pump, in particular, a plurality of actuators provided in an industrial machine such as a construction machine and a cargo handling machine. And an operation control device for a plurality of actuators using a single variable displacement pump which can be driven by a single variable displacement pump.

(Prior Art) Conventionally, a plurality of actuators provided in an industrial machine such as a construction machine and a cargo handling machine can be driven by a single variable displacement pump. For example, see JP-A-1-17
There is one shown in Japanese Patent No. 6,803.

In this apparatus, a plurality of (for example, two) actuators are connected in parallel to a discharge circuit of a single variable displacement pump via a flow control valve with a compensator valve, respectively, and the plurality of actuators selected by a shuttle valve are connected. In a pump control device that controls the discharge amount of the variable displacement pump by comparing the maximum load pressure of the variable displacement pump with the discharge pressure of the variable displacement pump, pressing in one direction by a control spring pressure and the selected maximum load pressure is performed. When a control cylinder having a piston which receives the action and is acted on by the discharge pressure of the variable displacement pump in the opposite direction is provided, and when the force in the opposite direction is more dominant than the pressing force in the one direction. The piston rod of the control cylinder is
The control cylinder is connected to a compensator valve so as to deflect the compensator spring.

In this case, the compensator spring pressure of the compensator valve provided around the flow control valve is determined in advance by the differential pressure between the selected maximum load pressure of the plurality of actuators and the discharge pressure of the variable displacement pump. By providing a control cylinder that weakens the spring force of the spring when the set value becomes equal to or less than the set value, the total flow passing through each flow control valve that controls the operation of the plurality of actuators is reduced, and the high load is reduced. It can be subsequently activated without stopping the movement of the compression-side actuator.

(Problems to be Solved by the Invention) However, in this case, the compensator spring of the compensator valve provided in the flow control valve is
When a differential pressure between the selected maximum load pressure of the plurality of actuators and the discharge pressure of the pump becomes equal to or less than a set value, by providing a control cylinder that weakens the spring force of the spring, Since the total flow rate of each flow control valve that controls the operation is reduced, the operation can be continued without stopping the movement of the high load pressure actuator. On the other hand, while operating multiple actuators,
When the simultaneous operation with the low-pressure actuator is performed from the operation of only the high-pressure actuator, the operating speed of the low-pressure actuator becomes extremely low.When the operation of the high-pressure actuator is stopped and the operation is shifted to the operation of only the low-pressure actuator, There has been a problem that the oil flow to the actuator side rapidly increases, and the speed of the low-pressure side actuator changes suddenly, which may cause an accident for an operator or the like working around the low-pressure actuator.

The present invention has been made in view of such problems in the conventional example. In an operation control device of a plurality of actuators provided in parallel with a discharge circuit of a single variable displacement pump, a signal of the selected maximum load pressure is provided. By providing a second relief valve having a set pressure lower than the relief pressure of the actuator via a second switching valve in a second signal circuit branched from the circuit, a single variable displacement capable of solving the above-described problem is provided. An object of the present invention is to provide an operation control device for a plurality of actuators using a pump.

(Means for Solving the Problems) According to the present invention, in order to solve the above-mentioned problems of the conventional example, a plurality of actuators are connected in parallel to a discharge circuit of a single variable displacement pump via a direction switching valve with a compensator valve. And controlling the operation of the plurality of actuators by adjusting the discharge capacity of the variable displacement pump based on a comparison between the maximum load pressure of each of the actuators selected by the shuttle valve and the discharge pressure of the variable displacement pump. In the control device, a second signal circuit is branched from the selected signal circuit having the highest load pressure, and the second signal circuit is connected to the second signal circuit via a second switching valve at a set pressure lower than the relief pressure of the actuator. This is an operation control device for a plurality of actuators using a single variable displacement pump provided with two relief valves.

(Operation) Since the present invention has the above-described configuration, a plurality of actuators connected in parallel to the discharge circuit of the single variable displacement pump can be operated by switching the direction switching valve of the pressure oil supply / discharge circuit to each of them. In addition to being able to operate simultaneously or separately, a second relief circuit provided via a second switching valve to a second signal circuit branched from a signal circuit for controlling the discharge amount of the single variable displacement pump, The signal pressure of the signal circuit is reduced, the discharge amount is controlled by comparing the signal pressure with the discharge pressure of the variable displacement pump, and a sudden change in the low-pressure side actuator speed is prevented.

(Embodiment) Hereinafter, an embodiment of an operation control device for a plurality of actuators using a single variable displacement pump according to the present invention will be described with reference to FIGS.

FIG. 1 is an explanatory diagram of a control circuit according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram of the characteristic curve. 1 and 2, reference numerals 1 to 6 denote bucket cylinders, boom cylinders, left traveling motors, right traveling motors, turning motors, and arm cylinders as a plurality of actuators driven by a single variable displacement pump 51.

Reference numeral 10 denotes a direction switching valve block, and reference numerals 11 to 17 denote bucket cylinders 1, boom cylinders 2, left traveling motors 3, right traveling motors 4, turning motors 5, provided in the direction switching valve blocks 10.
Direction switching valve for switching the direction of supply and discharge of pressure oil to the arm cylinder 6 and the like.
(However, the actuator 7 is not shown)
21A, 21B, 22A, 22B, 26A, 26B are relief valves provided in drive circuits 11A to 16A for supplying and discharging pressure oil to the bucket cylinder 1, the boom cylinder 2, the arm cylinder 6, and the like. 31 to 37 are a bucket cylinder 1, a boom cylinder 2, a left running motor 3, a right running motor 4, a swing motor 5, an arm cylinder 6, and a discharge circuit of a variable displacement pump 51 to be described later.
A compensator valve provided in the connection circuit (pressure oil supply circuit) with 61, 31A to 37A are adjusting cylinders for adjusting the compensator spring pressure of compensator valves 31 to 37, 42
Reference numeral 47 denotes a shuttle valve for selecting the maximum load pressure generated in the bucket cylinder 1, the boom cylinder 2, the left traveling motor 3, the right traveling motor 4, the swing motor 5, the arm cylinder 6, and the like, and 52 denotes the tilting of the variable displacement pump 51. A plate, 53 is a tilt cylinder, 54 is an arm interlocked with a cylinder rod of the tilt cylinder 53, 57 is a flow control valve, and 58 and 55 form a horsepower control valve. 59 is a remote control valve, 62 is a discharge circuit,
63 is a main relief valve provided in the discharge circuit 61, 65 is a signal circuit,
67 is an unload valve, and T is a tank.

70 is a second switching device for switching the signal pressure (upper limit value) of the signal circuit 65, 71 is a second signal circuit branched from near the flow control valve 57 of the signal circuit 65, and 72 is a second signal circuit provided in the second signal circuit 71. The switching valve 73 is a second relief valve provided in series with the second switching valve 72, and the relief pressure of the second relief valve is set lower than the relief pressure of the relief valves 21A to 26B.

The second switching valve 72 and the second relief valve 73 may be provided in a reverse relationship to the embodiment shown in FIG. Also,
The relief pressure of the main relief valve 63 is
Set higher than A or 26B.

(Operation of the First Embodiment) First, the pressure oil supplied from the discharge circuit 61 of the variable displacement pump 51 is supplied to the bucket cylinder 1, the boom cylinder 2, and the left side via the compensator valves 31 to 37 and the direction switching valves 11 to 17. Traveling motor 3, right traveling motor 4, turning motor 5,
It is supplied to an actuator such as the arm cylinder 6 and discharged from the discharge circuit 62 to the tank T to drive the actuators 1 to 6 in required directions.

At that time, the load pressure of each actuator 1 to 6 etc.
By connecting the signal circuits 65 based on the respective load pressures via the shuttle valves 42 to 47, those maximum load pressures are selected, and the maximum load pressure and the discharge pressure of the variable displacement pump 51 are selected. The tilt angle of the tilting plate 52 of the variable displacement pump 51 is controlled by a flow control valve 57 operated by a differential pressure to supply and discharge pressure oil to and from the tilting cylinder 53 (upper tilting cylinder 53 in FIG. 1). Thus, the discharge amount of the variable displacement pump 51 is adjusted.

In addition, the variable displacement pump is controlled by the horsepower control valves 55 and 58.
While controlling the horsepower of 51 to prevent the occurrence of overload on the engine, the single variable displacement pump 51 secures the discharge amount of pressure oil necessary for simultaneous driving of a plurality of actuators 1 to 6, etc. These operations themselves are substantially the same as those of the conventional device of this type.

However, in the first embodiment, the multiple actuators 1
The highest value of load pressure, such as 6 to 6
The flow control valve 57 is operated by comparing the maximum load signal of the signal circuit 65 selected by the above with the discharge pressure of the variable displacement pump 51.
The tilt angle of the tilt plate 52 (therefore, its discharge amount)
And the second signal branched from the signal circuit 65.
The second switching valve 72 of the signal circuit 71 is switched, for example, before the operation of a high-pressure actuator such as the fork grab cylinder 1 or the like,
By setting the relief pressure of the second relief valve 73 of the second signal circuit to a desired value in advance, the variable displacement pump 51
Control of some of the high-pressure actuators (for example, the fork grab cylinder 1) to prevent inadvertent sudden shifting (rapid rotation) of other low-pressure actuators (for example, the swing motor 5). . Hereinafter, this operation will be described for each operation state.

(Open position of second switching valve 72) Set pressure of relief valves 21A to 26A and 21B to 26B> Set pressure of second relief valve 73 + set differential pressure of unload valve 67 (1) Fork grab is gripping an object At this time, the fork grab cylinder 1 is in a relief state. Discharge pressure of the pump 51 at this time, tries to rise up to the set differential pressure of the relief pressure PR ₁ + flow control valve 57 of the relief valve 21B, a relief pressure PR ₁ of the relief valve 21B> the relief of the second relief valve 73 Pressure + the set pressure difference of the unload valve 67, the discharge pressure from the variable displacement pump 51 becomes the relief pressure of the sum of the set pressure difference of the second relief valve 73 + the unload valve 67, and the tank pressure from the unload valve 67. It is discharged to T.
Since the set differential pressure of the unload valve 67 is larger than the set differential pressure of the flow control valve 57, the flow control valve 57 holds the discharge amount of the pump 51 at a minimum value (left position).

Therefore, the power loss is smaller than the conventional example. At this time,
The oil flow to the bucket (fork grab) cylinder 1 is substantially zero, but the pressure is guaranteed.

(1 ') If the second switching circuit 71 is not provided, the discharge pressure of the variable displacement pump 51 is equal to the relief pressure PR ₁ of the relief valve 21B + the differential pressure of the flow control valve 57, The flow rate becomes the spool set flow rate, and the horsepower control valve 5
Within the flow rate range set by 5, 58, the relief valve 2
Relief at the relief pressure PR ₁ set by 1B.

(2) When the turning motor 5 is turned in the state of (1), the operating pressure of the turning motor 5 is equal to the set pressure PR ₁ set by the relief valve 21B of the bucket cylinder ₁ , and the unload valve Since the differential pressure of 67 + the pressure of the second relief valve 73 作 動 the operating pressure, the unload valve 67 is closed and the variable displacement pump is
The discharge pressure oil 51 flows through the direction switching valve 15 to the turning motor 5 side.

At this time, the set flow rate of the compensator valve 35 on the side of the swing motor 5 causes the set flow rate to flow to the swing motor 5 (low-pressure actuator). Since the differential pressure is set to be constant by the action of the flow control valve 57, the variable flow pump is set within the flow range set by the horsepower control valves 55 and 58 until the flow required by the swing motor 5 side. Increase the discharge amount of 51.

Therefore, the amount of pressure oil supplied to the swing motor 5 is
The set flow rate of the turning motor 5 is satisfied.

(2 ′) If the second switching valve 72 of the second switching circuit 71 of the first embodiment is not provided, the discharge pressure of the pump 51 will be the relief pressure PR ₁ + set by the relief valve 21B of the bucket cylinder 1. The differential pressure of the flow control valve 57 is reached and the horsepower control valve 5
Within the flow rate range set by 5 and 58, the discharge flow rate of the pump 51 is the sum of the set flow rates of the bucket (fork grab) cylinder 1 and the swing motor 5.

 These relationships are summarized as follows.

In the conventional example, in a power shovel or the like, the sum of the set flow rates of the ports of the direction switching valve is generally larger than the maximum value of the discharge flow rate of the variable displacement pump 51.

In summary, according to the first embodiment, the following effects can be expected.

(Comparison between the first embodiment and the conventional example) (A) A state in which an object is held by a fork grab P ₁ (Example) Set pressure of the second relief valve 73 + set differential pressure of the unload valve 67 P ₂ ( set differential pressure in the conventional example) set relief pressure PR ₁ of the relief valve 21B pressure + flow control valve 57, and if, P ₁ <discharge amount Q ₂ P ₂ of P ₂ Q ₁ pump 51 when the P ₁ At this time, the discharge amount of the pump 51 Q ₁ > Q ₂ , but in this state, P ₁ > P ₃ = (set pressure of the second relief valve 73 + differential pressure of the flow control valve 57) Therefore, the flow control valve 57 is Ikikiri the left position of FIG. 1, a variable displacement pump 51 holds the minimum discharge rate Q _3.

Q ₃設定 Set flow rate QF of bucket (fork grab) cylinder circuit This Q ₃ is relieved by the unload valve 67.

In the conventional example, Q ₂ is relieved by the relief valve PR _1. Q ₃ <Q ₂ (B) In the state (A), the circuit of the swing motor 5 is opened, and the compensator valve 35 of the swing motor 5 circuit is opened. and since the flow pressure oil through the directional control valve 15, the discharge pressure of the variable displacement pump 51 is reduced until P _3, closing the unload valve 67, the flow rate required to maintain the working pressure P ₃ Is discharged by the variable displacement pump 51.

Further, in this state, no pressure oil flows to the bucket (fork grab) cylinder 1 side, and only the pressure is maintained.

When Q ₆ of the control diagram of the discharge amount of the second view of the pump 51 when the _{P 3, Q 6> Qs ≒} Q 4 bucket (fork grab) cylinder circuit flow rate (actual flow rate) Q ₄ ≒ 0 Set flow rate of the swing motor 5 circuit ≒ Qs Swivel motor 5 circuit flow rate (actual flow rate) = Q ₄ At this time, the discharge amount of the pump 51 is と な り Qs, and the set flow rate of the swing motor 5 circuit can be sufficiently secured.

The set flow rate Qs of the drive circuit 15A of the swing motor 5 is:
It is smaller than the limit value of the discharge amount by the horsepower control valves 58 and 55.

(Conventional example) Q _5: Open driving circuit of the turning circuit flow (flow actually flows) swing motor 5, since the flow of hydraulic fluid through the compensator valve (turning), the flow rate of the pump 51 holds the P ₂ attempting, want flow is increased, the horsepower control valve 58,55, pump 51 flow rate Q ₂ can only discharge.

QF: Assuming the set flow rate of the bucket (fork gralab) cylinder, Q ₂ ≪Qs + QF Since there is an anti-saturation mechanism, Q ₂ = Qs ×% + QF ×%. In the above equation,% is the set flow rate reduction rate during the anti-saturation operation.

Thus, Qs»Qs ×% = Q _5, and the turning circuit flow (flow rate actually flowing) becomes much less than the set flow rate.

The above is a comparison between the embodiment of the present invention and the conventional example.
Also in the present invention, when the second switching valve 72 is set to the closed position, the bucket (fork grab) cylinder 1
Is set to a high pressure by the relief valves 21A and 21B.

Although the second switching valve 72 is configured as an electromagnetic valve in this embodiment, the second switching valve may be configured as a type that switches with hydraulic pressure or pneumatic pressure.

(Second Embodiment) Next, a second embodiment of an operation control device for a plurality of actuators using a single variable displacement pump according to the present invention, in particular, a second switching device thereof will be described with reference to FIG. . In addition,
Parts common to those in the first embodiment shown in FIGS. 1 and 2 have the same names and the same reference numerals.

In FIG. 3, reference numeral 80 denotes a second switching device similar to the second switching device 70 in the first embodiment.
Is a second signal circuit branched from the vicinity of the flow control valve 57 (near the immediately preceding position) of the signal circuit 65, as in the first embodiment.
71, a second electromagnetic switching valve 82 and a second relief valve 73 are provided.
, The directional control valve 11 of the bucket (fork grab) cylinder 1 is automatically operated, and the directional control valve 15 of the swing motor 5 or the arm cylinder 6 or Detects that 16 operations have been performed and switches.

The remaining structure and operation are substantially the same as those of the first embodiment including the second switching device 70.

(Effects of the Invention) Since the present invention has the above-described configuration, it has the same effects and effects as those of a conventional multi-actuator operation control device using the same type of single variable displacement pump, and also has the following effects. can get.

(1) In a multiple-actuator operation control device in which a plurality of actuators can be driven simultaneously or separately by a single variable-displacement pump, a signal of the selected maximum load pressure of the plurality of actuators instructing the operation of the variable-displacement pump The circuit is provided with a second relief valve or a pressure reducing valve that can be operated at a set pressure lower than the relief pressure of the signal circuit. Therefore, by operating the second relief valve or the pressure reducing valve in a timely manner, one of a plurality of actuators operating in parallel can be operated. Even when the operation of the unit is stopped, it is possible to perform a stable operation without fear of causing a sudden change in the speed of another actuator.

(2) When the second relief valve provided in the signal circuit is an electromagnetic proportional relief valve, the relief pressure of the electromagnetic proportional relief valve is adjusted as needed, so that a part (high-pressure actuator) of a plurality of actuators operating in parallel Even when the operation is stopped, there is no possibility that the speed of the remaining (low pressure) actuator is suddenly changed.

(3) Since the signal circuit is provided with a pressure reducing valve for appropriately reducing the relief pressure of the signal circuit by a hydraulic signal or an electric signal, by performing a pressure reducing operation for appropriately reducing the pressure of the pressure reducing valve by a hydraulic signal or an electric signal, When a part of the actuators is stopped during the simultaneous movement of the plurality of actuators, there is no possibility that the low-pressure actuator may suddenly shift.

(4) The second signal circuit branched from the signal circuit for commanding the operation of the variable displacement pump is provided with the second relief valve having a low relief pressure via the second switching valve. The discharge amount of the variable displacement pump can be adjusted by the relief pressure of the second relief valve, and even when the operation of some of the plurality of actuators that operate in parallel is stopped,
There is no danger of causing sudden changes in other actuator speeds.

(5) By closing the second switching valve 72 provided in the second switching device branched from the signal circuit, it becomes possible to increase the discharge pressure of the variable displacement pump to the setting of the main relief valve 63. When the left and right traveling motors 3 and 4 are driven, a required high output is obtained.

(6) If the second switching valve of the second signal circuit has an automatic operation structure such as an electromagnetic type or a hydraulic type in response to the operation of an actuator such as a swing motor, the switching operation of the second switching valve of the second switching device. There is no fear of forgetting.

(7) A simple structure change in which a second switching circuit and a second relief valve are simply provided in a second signal circuit branched from a signal circuit of an operation control device for a plurality of actuators using an existing variable displacement pump, the present invention has a simple structure. An operation control device for a plurality of actuators using one variable displacement pump can be implemented.

[Brief description of the drawings]

The drawings show an embodiment of an operation control device for a plurality of actuators using a single variable displacement pump according to the present invention. FIG. 1 is an explanatory diagram of a control circuit of the first embodiment, and FIG. FIG. 3 is an explanatory diagram of a second signal circuit according to the second embodiment of the present invention. (Explanation of reference numerals) 1 ... Fork (bucket) cylinder 5 ... Swing motor 11-17 ... Direction switching valve 21A-26A ... Relief valve 21B-26B ... Relief valve 31-36 ... Compensator valve 42-48 … Shuttle valve 51… variable displacement pump 55, 58… horsepower (pressure) control valve 57… flow control valve 61… discharge circuit 62… discharge circuit 65… signal circuit 71… second signal circuit 72 , 82 Second switching device 73 Second relief valve 82 Second electromagnetic switching valve

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F15B 11/00-11/22 E02F 9/20-9/22

Claims (2)

(57) [Claims] A plurality of actuators are connected in parallel to a discharge circuit of a single variable displacement pump through a directional control valve with a compensator valve, and the maximum load pressure of each of the actuators selected by a shuttle valve and the variable A control device that controls the operation of the plurality of actuators by adjusting the discharge displacement of the variable displacement pump by comparing the displacement with the discharge pressure of the displacement pump. A plurality of actuators operated by a single variable displacement pump, wherein a branch is provided, and a second relief valve having a lower set pressure than the relief pressure of the actuator is provided in the second signal circuit via a second switching valve. Control device. 2. The single relief valve according to claim 1, wherein said second relief valve provided in said second signal circuit is configured as an electromagnetic proportional relief valve so that its relief pressure can be adjusted. Operation control device for multiple actuators using a variable displacement pump.