JPH01156300A - Free swing circuit for upper revolving superstructure - Google Patents

Abstract

PURPOSE: To improve workability by arranging a free swing time preset pressure variable valve, and changing a constant acceleration feeling and a swing degree of an upper slowing body in a hydraulic excavator. CONSTITUTION: At ordinary slewing time, since a free swing switch 18 is turned off, a solenoid proportional relief valve 7a is not excited, so that maximum preset pressure becomes constant by a spring 6. Here, when a slewing operation lever 19 is turned rightward, an electric current I2 from a potentiomemter 21 flows to a pilot directional control valve 13 to be put in an opening position A, a meter in valve 10 is opened through an orifice 12, a slewing motor 1 is rotated by oil from a pump 15, and a meter out valve 4b is opened through an orifice 5b to return oil to a tank 16. While, when the free swing switch 18 is turned on, an electric current I1 according to a position of the slewing operation lever 19 flows to the solenoid proportional relief valve 7a to change free swing time preset pressure to thus eliminate a sense of incompatibility of an acceleration feeling at free swing time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a free swing circuit of an upper revolving structure such as a hydraulic excavator or crane. Free swing refers to, as shown in FIG. 6, when the upper rotating body 34 is stopped from the swinging state with a swing brake in a suspended load state, the suspended load 33 swings in a pendulum shape at the stopped position and becomes unstable. Therefore, the operator sets the swing operation lever to the neutral position as necessary, and then uses inertia to swing the upper swing structure without using the brake and stops at a predetermined stop position to stabilize the suspended load. In this way, when the swing operating lever is in the neutral position, the swing stop at a predetermined position due to inertia without using the brake is called lever free swing. Regarding free swing circuits.

(Prior Art) A conventional free swing hydraulic circuit includes a main swing circuit communication circuit as shown in Fig. 5. This communication circuit operates when the swing operation lever is in the neutral position, and controls the free swing speed. was given by a diaphragm in the communication circuit.

To explain in detail based on the free swing circuit, (1) Main swing circuit... This consists of a main circuit and a pilot circuit, and the main circuit includes a pump 15, a relief valve 31a, and a switching valve 32.
, swing motor 1, motor circuits 2a, 2b and tank 16
On the other hand, the pilot circuit includes the pump 15c, the relief valve 3b, the pilot switching valve 30 and the switching valve 32 which are directly operated by the swing operation lever 19, and the pilot circuits 29a and 29b.
9b. By operating the swing operation lever 19, the swing motor 1 rotates, and the upper revolving body swings.

(2) Communication circuit...This is the switching valve 23.27 and the circuit 25a, 25b, 2 which connects these with the main swing hydraulic circuit.
8a and 28b, and the switching valve 23 is connected to the swing motor circuit 2.
It has a B position that communicates a and 2b and an A position that blocks it,
Generally operated by a solenoid valve.

On the other hand, the switching valve 27 connects the communication circuits 25a and 25b provided at the B position of the switching valve 23 with the D position and disconnects the communication circuits 25a and 25b.
This switching is performed by pilot circuit 29a or 2
It operates depending on the presence or absence of pilot oil pressure 31b from 9b. A throttle 26 is provided at the D position of the main switching valve 27.

(3) Operation: Selection between normal swing and free swing is made by the switching valve 23. The actual free swing is the switching valve 2
3, the switching valve 27 is moved to the D position by setting the swing operation lever 19 to neutral. The free swing speed is limited by an aperture 26.

(Problems to be Solved by the Invention) The above-mentioned conventional free swing circuit is affected by the swing speed and swing oil pressure before entering the free swing, and therefore has the problem of causing a difference in the adjustment sensitivity of the free swing. there were.

This was compensated for by the skill of the operator.

Moreover, depending on the work, the free swing speed itself may need to be changed, and in order to change the orifice 26, the switching valve 2
There was a problem that 7 had to be replaced.

The present invention attempts to solve the above-mentioned conventional problems by changing the free swing oil pressure in conjunction with the swing operation lever.

(Means and actions for solving the problem) The relief valve of the swing hydraulic circuit is an electromagnetic proportional relief valve, and the position signal of the swing operation lever is sent to the electromagnetic proportional relief valve via the controller, and its current value is This is a free-swing circuit that changes the set oil pressure by, and this is explained with reference to FIG. During free swing, this changes like the pressure line P due to the current change (1) from the potentiometer linked to the swing operation lever.

Therefore, the necessary pressure can be applied as shown in P2 by fixing the swing operation lever.

(Example) An example of the present invention will be described in detail below with reference to Fig. 2.3.4.

This embodiment is an example of application to a poppet type hydraulic circuit, and describes a free swing circuit and its operation for a right turn.

(1) Turning to the right...During normal turning, the free swing switch 18 is turned OFF, so the electromagnetic proportional relief valve 7a
Current ■1 does not flow in . Therefore, regardless of the displacement of the swing operation lever 19, the maximum set pressure P given by the spring 6,
is constant.

When the turning operation lever is turned to the right, the electric current I2 from the potentiometer 21 linked to this is applied to the pilot switching valve 13.
The flow changes the closed position B to the open position A, and the resulting pressure 11 using the differential pressure of the throttle 12 is applied to the meter-in valve 1.
0 is opened, the circuit 2a is filled with oil from the pump 15, and the swing motor l is rotated. The return oil that has applied the rotational force tries to fill the primary circuits 2b and 9b, but since the pilot switching valve 13 is in the A position, the circuit oil 9b is returned to the return circuit 14.
The resulting pressure 3b using the differential pressure across the throttle 5b opens the meter-out valve 4b, and returns the main flow of the return oil from the main valve 4b to the return circuit 14 and then to the tank 16.

If the swirling pressure exceeds the set pressure, this pressure 8 pushes the spring 6, opens the relief valve 7a, and discharges the pressure oil 9a to the return circuit. As a result, a pressure difference is generated in the throttle 5a,
Due to this pressure difference, the pressure 3a opens the meter-out valve 4a, and the main flow of relief oil is returned from the rice pipe 4a to the return circuit 14 and then to the tank 16.

(2) Free swing...free swing switch 1
8 is turned ON, a current 11 corresponding to the position of the swing operation lever is generated in the potentiometer 20a, and flows to the electromagnetic proportional relief valve 7a. This changes the cent pressure.

(3) Effect FIG. 3 is a schematic circuit diagram of the electric circuit shown in FIG. 2. In this embodiment, a variable resistor 22 is further connected in series with a potentiometer 20a and an electromagnetic proportional relief valve 7a. The effect obtained from the above is shown in FIG. In this example, the current value decreases as the opening degree of the swing operation lever increases, and when the rotation operation lever opening degree is maximum, the current value becomes zero, and the maximum set pressure Pl given by the spring of the relief valve (340kg/cm2). Conversely, when the opening degree is minimum, that is, neutral, the current is maximum and the set pressure is small. The change is as the pressure P.

On the other hand, the variable resistor 22 changes the slope of the pressure line P to P3.
It is something like this.

As a result, even at the same swing operation lever position, the pressure is P4.
I got something changed like this.

(4) As a result, the swing center pressure changes according to the movement of the swing lever, so regardless of the swing speed before entering the free swing,
A constant sense of acceleration and deceleration was obtained.

Moreover, instead of free swinging with the swing control lever in the neutral position as in the conventional case, the free swing is made at a desired position, and the degree of free swing can be easily changed.

(Effects of the Invention) The present invention solves the conventional problems of work hindrance due to an unnatural feeling of acceleration/deceleration during free swing and uneconomical effects caused by changing the switching valve itself.

Furthermore, the control means is electrical, which is the easiest to handle.

[Brief explanation of the drawing]

FIG. 1 is a diagram of the effect of control current change and hydraulic circuit set pressure in a free swing circuit according to the present invention, FIG. 2 is a diagram of an embodiment of a free swing circuit according to the present invention, and FIG. 3 is a free swing circuit according to the present invention. Fig. 4 is a schematic diagram of an embodiment of the electric circuit inside, Fig. 4 is an operational diagram of an embodiment of the free swing circuit of the present invention, Fig. 5 is a free swing circuit diagram of the prior art, and Fig. 6 is an example of the use of free swing. Show the diagram. 1... Swing motor 4a, 4b... Meter-out valve 5a, 5b, 12.26... Throttle 4a, 4b... Meter-out valve 7a, 7b... Electromagnetic proportional relief valve 10... Meter-in valve 13...Solenoid pilot switching valve 15.15c...Hydraulic pump 18...Free swing switch 19...Swivel operation lever 20a, 20b, 21-Potentiometer 22...Variable resistor 11 , I2...Current P...Set oil pressure change Pl...Maximum set oil pressure P2, Pi...Set oil pressure used during free swing and its change P3...Set oil pressure gradient change Applicant Komatsu Co., Ltd. Factory agent (patent attorney) Oka 1) Kazuki

Claims (1)

[Claims] The free swing circuit of the upper revolving structure is equipped with a variable set pressure valve during free swing to provide a constant sense of acceleration and deceleration.
A free swing circuit for an upper rotating body, characterized in that the degree of swing can be changed.