JPH0257170B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to civil engineering applications such as hydraulic excavators and hydraulic cranes in which a plurality of hydraulic pumps driven by a plurality of prime movers and one or more actuators are connected in a hydraulic closed circuit.・Related to hydraulic circuits of construction machinery.

In large hydraulic excavators, two engines drive two swing pumps, and these two swing pumps supply hydraulic pressure to one or more swing motors. If the hydraulic circuit formed by the motor is an open circuit, energy during swing braking cannot be recovered.
For this reason, it is already known to make the hydraulic circuit a closed circuit to recover energy during swing braking. Figure 1 shows the structure of a typical hydraulic excavator. 1 is an upper rotating body, 2 is a lower traveling body, 3 is a rotating wheel, 4 is a boom, 5 is an arm, 6 is a bucket, 7 is a boom cylinder, 8 is an arm cylinder,
9 is a bucket cylinder. Figure 2 shows the turning wheel 3.
The hydraulic circuit of a conventional hydraulic shovel is shown in which the hydraulic circuit of the swing motor 10 that drives the swing motor 10 is a closed circuit. The two engines 11a, 11b rotationally drive main pumps 13a, 13b, 14a, 14b, pilot pumps 15a, 15b, and double-swivel swing pumps 16a, 16b via pump drive devices 12a, 12b consisting of gears and the like. Main pump 13
a, 13b are connected to the switching valve group 19a by an open circuit via check valves 17a, 17b, and the main pumps 14a, 14b are connected to the switching valve group 19a via check valves 17a, 17b.
b via an open circuit to the switching valve group 19b. The switching valve groups 19a and 19b are each a plurality of directional switching valves 19a ₁ to 19a ₃ and 19b ₁ to 19b ₂ connected in series, each having a common inlet for pressure oil and an outlet to a tank _. The arm cylinder 8 is attached to the directional selector valve _19a2 , the left travel motor 20a is attached to the directional selector valve _19a3 , the boom cylinder 7 is attached to the directional selector valve _19b1 , and the bucket cylinder 9 is attached to the directional selector valve _19b2. right travel motor 2
0b are connected to each other. Each direction switching valve 19
a ₁ to 19a ₃ and 19b ₁ to 19b ₃ are used to switch the direction of the pressure oil and control the flow rate according to the pilot pressure signal, but these pilot pressure signal circuits are omitted in Fig. 2. . The rotating pumps 16a and 16b are equipped with a variable discharge capacity mechanism 2 such as a swash plate.
1a, 21b and regulators 22a, 22b for controlling them. regulator 22a,
22b is supplied with servo pressure from the pilot pumps 15a and 15b, and the pilot valve 23
A pilot pressure signal is given from The pilot valve 23 has an operating lever 24.

In FIG. 2, since the hydraulic circuit of the swing motor 10 is a closed circuit, oil returns from the swing motor 10 to the swing pumps 16a, 16b during swing braking, and the swing pumps 16a, 16b are driven as motors. It helps the engines 11a, 11b to rotate, thereby recovering energy. However, when one engine 11a is stopped and only the other engine 11b is operated, or when one engine 11a is stopped due to overload, the rotation pump 16b is closed because of the closed circuit.
The pressurized oil is supplied to the rotating pump 16a, which is stopped, and the rotating pump 16a performs a motor action to rotate the engine 11a. This may cause damage to the engine 11a, and the engine 11a may start unexpectedly, which is dangerous.

An object of the present invention is to provide a hydraulic circuit for civil engineering and construction machinery that solves the above-mentioned problems and can prevent a prime mover that is not in a normal rotation state from being rotated by the motor action of a hydraulic pump connected to it. That's true.

In order to achieve this object, the present invention provides at least one of the servo pressure circuit and the pilot pressure signal circuit of each regulator with an on-off valve that closes the pressure in the circuit to zero, thereby ensuring that each prime mover is operating normally. The present invention is characterized in that it includes a detection control means that closes an on-off valve provided on the side of the prime mover to be detected by detecting that it is not in a rotating state.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 3 shows an embodiment of the invention. Components similar to those in FIG. 2 are designated by the same reference numerals. Pilot valve 23
In the middle of the pilot pressure signal circuits 25a, 25b connected to the regulators 22a, 22b, there is provided an on-off valve 26 which makes the pressure in the circuit zero by closing.
a and 26b are provided, respectively.

Each engine 11a, 11b has a generator 2.
7a and 27b are directly connected, and the output is from the on-off valve 26.
By energizing the solenoids a and 26b, the on-off valve 26
a and 26b are opened. Also, generator 2
7a and 27b charge a battery 29 via diodes 28a and 28b. Diode 28a, 2
8b is a switch 26a, 26b where the output of the generator 27a, 27b is provided on the other engine side.
This prevents the solenoid from being energized. Each regulator 22a, 22b is connected to a servo pressure circuit 30 from a pilot pump 15a, 15b.
Servo pressure is supplied by a and 30b. In this embodiment, the generators 27a and 27b correspond to the detection control means of the present invention.

While the engines 11a and 11b are operating normally, the generators 27a and 27b are operated by the on-off valve 2.
Since the output current is sufficient to excite the solenoids 6a and 26b, the on-off valves 26a and 26b
becomes open. Therefore, pilot valve 2
When a pilot pressure signal is output from the pump 3, the regulators 22a, 22b displace the variable displacement mechanisms 21a, 21b in accordance with the magnitude of the pilot pressure signal, thereby changing the displacement of the rotary pumps 16a, 16b.

For example, when one engine 11a is no longer in a normal rotation state and enters a stopped or reversed state, the output current of the generator 27a becomes zero or less than a predetermined value close to zero, so the solenoid of the on-off valve 26a is energized. The opening/closing valve 26a is closed. This allows the regulator 22
A is now disconnected from the pilot valve 23, and the pilot pressure signal applied to both ends thereof becomes zero. Therefore, the regulator 22a is held at a neutral position indicating zero discharge capacity, and the swing pump 16a does not operate as a motor even if it receives pressure oil from the swing pump 16b.

FIG. 4 shows another embodiment of the invention. In this embodiment, engine oil pressure switches 31a, 31b and a battery 29 are used in place of the generators 27a, 27b. These correspond to the detection control means of the present invention.

When the two engines 11a and 11b are in normal rotation, the engine oil pressure switches 31a and 31b are both turned on due to the increase in engine oil pressure, and the on-off valve 26 is turned on from the battery 29.
The solenoids a and 26b are energized, and the on-off valve 26
Both a and 26b are in an open state. Therefore, the two swing pumps 16a, 16b discharge pressure oil in response to the pilot pressure signal.

For example, when one engine 11a is no longer in a normal rotation state, the engine oil pressure decreases and the engine oil pressure switch 31a is turned off.
The on-off valve 26a is in a closed state. By this,
The regulator 22a is held in a neutral position indicating zero displacement, thereby preventing the motor action of the swing pump 16a.

FIG. 5 shows another embodiment of the invention. In this embodiment, engine oil pressure is used as the detection control means, and engine oil pressure outlets 32a and 32b provided in engines 11a and 11b are connected to operating pressure input ports of on-off valves 33a and 33b.

When the two engines 11a and 11b are in a normal rotation state, the engine oil pressure increases, so this pressure is applied to the on-off valves 33a and 33b as operating pressure, so that the on-off valves 33a and 3
3b is in the open state, and the two rotating pumps 16
a and 16b discharge pressure oil in response to a pilot pressure signal.

For example, when one engine 11a is no longer in a normal rotation state, the engine oil pressure drops to a value lower than the operating setting pressure of the on-off valve 33a, so the on-off valve 33a returns to the closed state. Therefore, the regulator 22a is held in a neutral position indicating zero displacement, thereby preventing the motor action of the swing pump 16a.

The present invention is not limited to the pilot pressure signal cut method shown in FIGS.
Including those using servo pressure cut method. That is, the on-off valve 26 is installed in the middle of the servo pressure circuits 30a and 30b.
a, 26b, 33a, 33b are respectively provided, and when it is detected that the engines 11a, 11b are not in a normal rotation state, the on/off valves 26a, 26b, 33
a, 33b are closed, and the regulators 22a, 33b are closed.
The present invention also includes a method that makes the servo pressure applied to 22b zero.

The present invention is not limited to application to closed circuits of swing pumps, but can be applied to any hydraulic circuit in which a plurality of hydraulic pumps driven by individual prime movers and one or more actuators form a closed circuit. Can be applied. Furthermore, the present invention is not limited to two prime movers, but can also be applied to three or more prime movers. Furthermore, both the pilot pressure signal cut method and the servo pressure cut method can be used simultaneously.

As explained above, according to the present invention, at least one of the servo pressure circuit and the pilot pressure signal circuit of each regulator of a plurality of hydraulic pumps is provided with an on-off valve that closes the pressure of the circuit to zero. Since the opening/closing valve is closed by the detection control means by detecting that the prime mover is not in a normal rotation condition, it is possible to prevent the motor action of the hydraulic pump connected to the prime mover that is not in a normal rotation condition. . Therefore, it is possible to prevent rotational force from acting on the prime mover that is not in a normal rotation state, and the danger caused by this can be eliminated.

[Brief explanation of the drawing]

Figure 1 is a side view of a typical hydraulic excavator, Figure 2
The figure is a hydraulic circuit diagram of a hydraulic excavator equipped with a conventional closed circuit, FIG. 3 is a circuit diagram of an embodiment of the present invention, and FIG.
The figure is a circuit diagram of another embodiment of the present invention, and FIG. 5 is another hydraulic circuit diagram of the present invention. 10...Swivel motor, 11a, 11b...Engine, 15a, 15b...Pilot pump, 1
6a, 16b...Swivel pump, 21a, 21b...
...Variable discharge capacity mechanism, 22a, 22b...Regulator, 23...Pilot valve, 25a, 25b
...Pilot pressure signal circuit, 26a, 26b...
Opening/closing valve, 27a, 27b...generator, 29
...Battery, 30a, 30b...Servo pressure circuit, 31a, 31b...Engine oil pressure switch, 32a, 32b...Engine oil pressure outlet, 33a, 33b...Opening/closing valve.

Claims (1)

[Claims] 1 A plurality of hydraulic pumps driven by individual prime movers and connected in parallel to an actuator, an actuator connected to the hydraulic pumps in a closed circuit, servo pressure by a servo pressure circuit, and servo pressure by a pilot pressure signal circuit. In a hydraulic circuit for a civil engineering/construction machine equipped with a plurality of regulators each receiving a pilot pressure signal and controlling the variable discharge displacement mechanism of each hydraulic pump, a servo pressure circuit of each regulator and a pilot pressure signal circuit are provided. At least one of them is provided with an on-off valve that closes the pressure in the circuit to zero, and by detecting that each prime mover is not in a normal rotation state, the on-off valve provided on the side of the prime mover to be detected is A hydraulic circuit for civil engineering and construction machinery, characterized by comprising a detection control means for closing a valve.