JPH023535A - Running hydraulic circuit for construction machine - Google Patents

Abstract

PURPOSE:To perform simple and smooth transfer of a construction machine from low running to high running by a method wherein, in a construction machine which drives a hydraulic motor for running by switching a hydraulic switching valve, the volume of the hydraulic motor is switched to high and low in linkage with the hydraulic switching valve. CONSTITUTION:During high speed running, with a switch 13 turned ON, a high speed running command is transmitted, and control levers 1 and 1' of hydraulic switching valves 2 and 2' for running are inclined for control. In which case, with the increase in the control stroke of the control levers 1 and 1', their respective cams 16 and 16' are brought into contact with limit switches 10 and 10' to actuate their internal electric circuits. Thus, a switching valve 12 is switched from a position (c) to a position (d), pressure oil delivered from a pilot pump 11 flows in a line 15 and is exerted on switching valves 8 and 8'. As a result, the volumes of running motors 4 and 4' are reduced, and since the running motors are run at a high speed by means of pressure oil delivered from hydraulic pumps 3 and 3', the machine body of a construction machine is run at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to a travel hydraulic circuit in a hydraulically driven construction machine.

Conventional technologySelf-propelled construction machines are required to move within a work site and between work sites in a complex manner. High speed driving is often required.

In order to cope with this, hydraulic drive type construction machinery uses a drive actuator that can be switched between low speed and high speed sections by an external signal, and a signal for low speed and high speed switching is installed in the operator's cab. A transmitter will be installed and operated by the driver as necessary.

For example, one example of the conventional technology, which is an electric/hydraulic circuit for traveling in a crawler type hydraulic excavator, is shown in the system diagram of FIG. In this figure, hydraulic switching valve 18.1
When the 8" is operated in the forward and reverse directions individually or simultaneously, the pressure oil discharged from the hydraulic pump and the 3.3" passes through the switching valve and is transferred to the travel motor 4.
, 4', and the traveling motors 4, 4' rotate at the same time, or one of them rotates forward and backward, allowing the machine to move forward and backward, change direction, etc.

On the other hand, the traveling motors 4 and 4' are provided with a control cylinder 5 that operates a variable volume lever 6 that increases or decreases the volume per revolution. The control cylinder 5 is normally set to maximize the volume per rotation of the travel motor 4 via the volume variable lever 6 by the biasing force of a built-in spring, but when a pressure signal acts on the oil chamber, It extends and rotates the variable volume lever 6 to set the volume of the travel motor 4 to the minimum. That is, the hydraulic motor 4 is
When a constant pressure oil is supplied, the control cylinder 5 rotates at a higher speed than when signal pressure is applied to the oil chamber.

Reference numeral 8 designates a switching valve, which is normally in the A position due to the biasing force of a spring, and is switched to the opening position when a signal is applied from the pipe line 14 to the receiving part, or when the oil chamber of the control cylinder 5 is communicated with the tank 9. A conduit 22 for supplying pressure oil to the travel motor 4
.

Furthermore, the pressure oil discharged from the pilot pump 11 is guided to the pipe line 14 through pipes 19 and 15, and an electromagnetic switching valve is installed in the middle of the pipe line to open and close the internal oil line using a switch 13 located near the driver's seat. 12 is provided.

In a machine equipped with such an electric/hydraulic circuit, when traveling at low speed, the switch 13 is opened and the switching valve 12 is closed.
When is in the 8 position as shown in the figure, the pipe 19 is cut off in the Since the oil chamber of the control cylinder 5 communicates with the tank 9, the capacity for one rotation of the travel motor 4 is maximum, and when the travel hydraulic pressure switching valve 18 is operated in this state, the travel motor 4 exerts powerful rotational force at low speeds.

Next time you want to drive at high speed, close the switch 13 and then operate the travel hydraulic switching valve 18. At this time, the electromagnetic switching valve 12 will not switch from the C position to the 2nd position. , the discharge pressure oil of the pilot pump 11 is connected to the pipe line 19.
, the two-position passage of the switching valve 12 passes through lines 15 and 14 and acts as a signal on the receiving part of the switching valve 8, switching it to the opening position, so that the pressure oil in either line 22 or 23 is is the shuttle valve 24. M via the mouth position passage of the switching valve 8 and the pipe line 7
Since the oil flows into the oil chamber of the control cylinder 5 and activates the variable volume lever 6, the volume per rotation of the travel motor 4 is minimized, and the travel motor 4 can rotate at high speed even with the same amount of inflow oil. do. The above circuit and operation are based on the traveling motor 4'
The same applies to the side, so after opening or closing the switch 13, open or close the travel hydraulic pressure selector valve 18.18'
By operating the machine, it is possible to move the machine forward or backward at low or high speeds according to the driver's will.

The problem that Hatsu 11 is trying to solve When moving a machine, there are not only flat areas, but also slopes and muddy areas, so when climbing up a hill or getting out of a muddy area, it can run at low speeds to exert powerful running power.

In addition, it is desirable to switch to high-speed driving with a good ft ratio when on flat ground or when exiting the vehicle, but with the conventional circuit described above, it is necessary to operate a switch every time this is necessary. When the traveling road surface and driving conditions change frequently, the operation becomes complicated and may adversely affect the original operation of the work equipment and the operation of moving the machine. Furthermore, if the switch is operated to the high speed side beforehand when traveling on flat land or when disembarking, and then the travel hydraulic pressure switching valve is operated, the aircraft will suddenly start traveling at high speed, which may be dangerous or lead to a reduction in ride comfort.

In view of the above points, in this invention, when the switch for selecting high speed/low speed travel is operated to the low speed side, the aircraft always continues to travel at low speed as in the past, but when the switch is operated to the high speed side. When the travel hydraulic switching valve is operated, the aircraft will travel at low speed at the beginning of the switching stroke, and when operated near the end of the switching stroke,
By automatically reducing the volume per revolution of the travel motor and switching to high-speed travel, it is intended to provide a travel circuit that always starts at a low speed at the start of travel.

Means for Solving the Problems The present invention takes the following measures to solve the above problems. That is, in the signal circuit between the receiving part of the capacity switching means that switches the volume per revolution of the travel motor to a small volume in response to an external signal, and the signal transmitting means near the driver's seat, there is a travel hydraulic pressure switch. A signal circuit opening/closing means is provided which connects the front and rear signal circuits only near the end of the forward and reverse operation stroke of the hydraulic switching valve in conjunction with the switching operation of the valve.

Operation When the signal transmitting means near the driver's seat is operated and the travel hydraulic pressure switching valve is switched between the forward and reverse directions, the signal circuit opening/closing means does not connect the front and rear signal circuits at the beginning of the operation stroke, so the capacity is switched. No signal acts on the receiver of the means,
Therefore, the volume per revolution of the travel motor remains large, and the travel motor starts to rotate powerfully at low speed, but the operation stroke of the hydraulic switching valve is increased and the operation is continued until near the end of the stroke. Then, the signal circuit opening/closing means connects the front and rear signal circuits, and the signal from the signal transmitting means acts on the receiving part of the capacity switching means to switch the volume per rotation of the travel motor to a small capacity, so that the travel hydraulic pressure is switched. Just by operating a valve, the aircraft automatically shifts from low speed to high speed.

Note that when the signal transmitting means does not emit a signal, no signal acts on the receiving section of the capacity switching means regardless of the operating stroke amount of the travel hydraulic switching valve, so the volume per rotation of the travel motor is Similar to the prior art, the large volume is maintained at all times.

Example The circuit of this invention will be explained based on the drawings.

Figure 1 shows that the left and right crawlers are driven by traveling motors 4 and 4, respectively.
An example of an electric/hydraulic system diagram when the circuit of the present invention is applied to a hydraulic excavator of the type driven by .

In the figure, reference numerals 2 and 2' refer to hydraulic switching valves for traveling, through which pressure oil discharged from hydraulic pumps 3 and 3' are guided through pipes 20 and 20', respectively, and these valves are operated by rotating operating levers 1 and 1'. By switching between forward, reverse, and neutral, pressure oil is supplied to the pipes 22 or 23 and 22' or 23', or is not allowed to flow through the tank 9.
, 4' are rotated forward/reverse or stopped to perform traveling operation.

The travel motors 4, 4' are equipped with a volume variable lever 6.6' that increases or decreases the volume per revolution.
．． 6' is connected so as to be interlocked with the operation of the control cylinder 5.5', and when no signal pressure oil is acting on the oil chamber a of the control cylinder 5.5', the variable volume lever 6.6' is operated by the urging force of a built-in spring. The volume per revolution of the travel motor 4.4' is set to the maximum via the cylinder 6', but when a pressure signal acts on the oil chamber α, the control cylinder 5.5' resists the biasing force of the spring. By rotating the variable volume lever 6.6', the travel motor 4,
The volume per revolution of 4' can be set to a predetermined minimum value.

Reference numeral 8.8' is a switching valve, which is normally located at the A position and allows the pipes 7 and 7' leading to the oil chamber α to communicate with the tank 9, but when a signal from the pipe 14 acts on the receiving section, the switching valve becomes 0. the line 22 taken out via the shuttle valve 24, 24'.
, 23 and 22', 23'' are guided to the pipes 7 and 7', and these control cylinders 5 and 5', variable volume levers 6 and 6', and switching valves 8 and 8 ' constitutes capacity switching means for the traveling motors 4 and 4'.

12 is a switching valve, which is normally in position C,
The pipe line 15 leading to the tank 9 is connected to the tank 9, and the discharge pressure oil pipe line 19 of the pilot pump 11 is cut off. However, when a signal acts on the receiving part, it switches to two positions, and the machine part that connects the pipe lines 15 and 19. have. Further, t and i' are operation levers for switching the hydraulic switching valves 2.2' for traveling, and cams 16.16 are integrated with the respective operation levers 1 and 1''.
When the cam 16.16' is operated near the end of the operating stroke of the cam 16.16', the protrusion of the cam 16.16' comes into contact with the actuator of the limit switch 10.10'. It is designed to close the internal electric circuit of the switching valve 12, the cam 16.16' on the operating lever 1,1'', and the limit switch 10.10'.
13 constitutes a signal circuit opening/closing means for signals acting on the receiving section of the capacity switching means, and in this embodiment, by opening/closing the power supply circuit to the signal circuit opening/closing means, high speed, It functions as a signal transmitting means for issuing low speed commands. Further, the switch 13 and the limit switches lO and 10' are arranged in series, and the limit switches 10 and 10' are arranged in parallel on the signal circuit 17, so that even if the switch 13 is in a closed state, the limit switch lO
Alternatively, the power supply is not connected to the signal circuit 17 unless both or one of the terminals 10' is in a closed circuit state.

The operation of the present invention having the above configuration will be explained.

When the aircraft is to run at a low speed, the travel hydraulic pressure switching valve 2. Operate the operating levers 1 and 1' of τ. At this time, no signal pressure is generated in the conduit 15 from the signal circuit opening/closing means regardless of the operating amount of the operating lever 1.1', and therefore, the switching valve 8.8' of the capacity switching means
both remain in the A position, and the travel motors 4, 4
The volume per revolution of ' is set to the maximum, and the hydraulic pump 3
The discharged pressurized oil of ゜3' causes each of the traveling motors 4 and 4' to rotate strongly at low speed, so that the 11 bodies continue to travel at low speed.

Next, when driving at a high speed, the switch 13 is closed and the operating levers 1 and 1' are operated to tilt gradually under the high speed running command condition, but the operation stroke of the operating lever 1.1' is small. That is, immediately after starting running, the protrusion of the cam 16.16' is the limit switch 10.10''.
without contacting any of the limit switch 10.10'
Since the internal electric circuit remains open, no signal acts on the receiving section of the switching valve 12, and therefore no signal is generated in the conduit 15 from the signal circuit opening/closing means. , 4' rotate at a low speed, but the operating stroke of the operating levers 1, 1' is further increased to tilt them,
When near the end, the protrusion of the cam 16.16' acts on the actuator of the limit switch 10.10' and closes its internal electrical circuit, so that the switching valve 12 is switched from the C position to the 2nd position. , the discharge pressure oil of the pilot pump 11 flows as a signal into the pipe line 15 from the signal circuit opening/closing means,
Since it acts on the receiving part of the switching valve 8.8' which is the receiving part of the capacity switching means, the capacity switching means automatically sets the volume per revolution of the traveling motors 4, 4' to the minimum value, - The motors 4, 4' are rotated at high speed by the pressure oil discharged from the hydraulic pumps 3, 3', and the aircraft travels at high speed. In this way, even if a command for high-speed travel is selected with the switch, the vehicle starts smoothly at low speed at the beginning of travel, and gradually tilts the operating lever of the travel hydraulic switching valve to near the end of its stroke. Automatically shifts to high-speed driving. Also, during high-speed driving commands, due to changes in the driving road and other conditions, -
When it is necessary to drive at low speeds, there is no need for any special operation; simply tilt the operating levers 1 and 1' back to the original neutral direction and the signal from the signal circuit opening/closing means will automatically disappear. The travel motors 4, 4' will rotate at low speed.

In the above embodiment, a limit switch 10°lO' was provided, which corresponds to each of the cams 16.16' that rotate together with the operating lever 1.1' for the hydraulic pressure switching valves 2 and 2'. In addition, it is of course possible to operate one limit switch through a single detection device that mechanically detects the amount of operation of the operation lever 1.1''. The relationship between the amount and the operating point of the limit switch can be easily changed as necessary by changing the shape of the cam or the like.

Figures 2 and 3 show the main parts of the electric/hydraulic system IA showing the second and third embodiments of the present invention. This is an embodiment in which the present invention is applied to a circuit that employs a control method.

That is, like the first embodiment, the signal transmitting means in the second embodiment is based on the opening and closing of the switch 13 provided in the power supply circuit, but the signal transmitting means in the second embodiment is based on the opening and closing of the switch 13 provided in the power supply circuit. A pressure switch 21 is provided in the pressure switch 21, and the receiving part of the pressure switch 21 connects a pilot pipe leading to a pilot oil chamber of a remote-controlled traveling hydraulic pressure switching valve 25.25'' via shuttle valves 26, 27.28. When the pressure switch 21 is connected and the pilot pressure acting on the receiving section exceeds a predetermined pressure, the internal electric circuit of the pressure switch 21 is closed.

The third embodiment in Fig. 3 shows an example in which only a hydraulic signal is used, unlike the first and second embodiments, which use both an electric signal and a hydraulic signal as a signal medium. In this case, the on-off valve 30 that opens and closes the pipe line 19 from the pilot pump 11 as the signal transmitting means is replaced with the electromagnetic switching valve 12 as the signal circuit opening/closing means, and a switching valve that is operated by a pilot pressure higher than a predetermined pressure is used. 29 is used to guide pilot pressure oil for operating the hydraulic switching valves 25, 25' obtained by the shuttle valves 26, 27, 28 to the receiving part of the switching valve 29.

These, 2nd. The third embodiment is also similar to the first embodiment in its operation.
This is exactly the same as the embodiment, and in the above embodiment, a crawler type construction machine that runs with left and right running motors was explained, but the present invention is not limited to application only to this rare running type. Needless to say, the present invention can be applied to the travel hydraulic circuit of wheeled construction machinery.

Effects of the Invention If a hydraulic drive type construction machine is equipped with the travel hydraulic circuit of the present invention in a machine that selects high and low speed stages by switching between large and small volumes per revolution of the hydraulic motor for travel, it will be possible to achieve high-speed travel. Even when the command is selected, the vehicle starts traveling at a low speed gear, and when the travel control lever is operated near the end of its operating stroke, the travel motor automatically switches to high-speed operation, so there are no other special troubles. The vehicle can start smoothly and shift to high-speed driving without any operation. In addition, even when driving at high speed and changing conditions require low-speed driving, simply returning the driving control lever to the neutral direction will automatically switch the driving motor to low-speed operation. The M shift operation is easy, and even when operating work equipment or other operations, it does not interfere with the driving operation, and the ride comfort during one start and stop is improved, and the N shift is less tiring and safer. Helps improve efficiency.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the traveling hydraulic circuit of the present invention.
Hydraulic system diagram, Fig. 2 is a diagram of the main electrical/hydraulic system in the second embodiment of the present invention, Fig. 3 is a diagram of the main hydraulic system in the third embodiment of the invention, and Fig. 4 is a driving diagram of the conventional technology. FIG. 2 is an electrical/hydraulic system diagram showing an example of a hydraulic circuit. 1.1” ・・・・・・・・・ 5.5′ ・・・・・・・・・ 8.8′ ・・・・・・・・・ 10.10′ ・・・・・・・ l 2 ・ ・・・・・・・・・・・・ l 3 ・・
・・・・・・・・・・・・ 2 l ・・・・・・・・・・・・ 29 ・・・・・・・・・・・・ 30 ・・・・・・・・・・・・Operation lever control cylinder switching valve limit switch switching valve switch pressure switch switching valve on-off valve Fig. 2

Claims (1)

[Claims] In a travel hydraulic circuit of a construction machine that travels by switching a hydraulic switching valve to drive a hydraulic motor for a travel device, a receiving unit of a capacity switching means that switches the volume per revolution of the travel motor between large and small based on an external signal. The signal can be arbitrarily transmitted or stopped via a signal circuit opening/closing means that is linked to the switching operation of the hydraulic switching valve and can connect the front and rear signal circuits only near the end of the forward and reverse operation stroke. A travel hydraulic circuit for construction machinery connected to a signal transmitting means capable of