JPH0447487Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a device for switching the traveling speed of traveling means such as left and right crawlers of a building vehicle.

(Prior art) Conventionally, the running speed of left and right crawlers driven by hydraulic motors has been switched according to the load pressure. Generally, the capacity is changed by providing each with an automatic switching valve that operates according to the load pressure.

When the automatic switching valve operates due to an increase in load pressure, one chamber of the displacement control cylinder provided to control the displacement of the variable displacement hydraulic motor becomes tank pressure and operates to maximize the displacement of the motor. If the load pressure is lower than the set pressure, the automatic switching valve will not operate and the load pressure will be introduced into one chamber of the control cylinder, and the displacement control cylinder will operate to minimize the displacement of the motor.

(Problem that the invention aims to solve) Since the load pressure of the operating circuit of the hydraulic motor that drives the left and right crawlers is not necessarily the same pressure,
There are cases where the automatic switching valve on the high load pressure side operates and the automatic switching valve on the low load pressure side does not operate, and in such a case, the left and right crawlers have different speeds, causing the inconvenience that the construction machine cannot move straight.

The present invention aims to solve this problem.

(Means for Solving the Problems) In the present invention, the left and right crawlers and other traveling means are connected to separate variable displacement hydraulic motors, and the displacements of the hydraulic motors are controlled by respective displacement control cylinders to speed up the traveling speed. In the system, one chamber of each capacity control cylinder is selectively connected to the tank and the operating circuit of the hydraulic motor to control the capacity of the hydraulic motor to a maximum or a minimum. A switching valve is provided respectively, and if the force due to the pressure of the operating circuit acting on the piston is smaller than the force of the set spring, the connection circuit connects the first electromagnetic switching valve and the operating circuit. interpose an automatic switching valve that connects the connecting circuit to the tank when the force due to the pressure of the operating circuit acting on the action of the piston is greater than the force of the set spring; A sensor is installed that detects the switching operation to connect the tank to the tank and sends an electrical signal.
The electromagnetic switching valves other than the first electromagnetic switching valve are connected to the sensor by an electric circuit so as to perform a switching operation that minimizes the capacity of the hydraulic motor connected to the electromagnetic switching valve.

(Function) Each traveling means starts driving when pressure fluid is supplied to each variable displacement hydraulic motor, and when the load pressure generated in the operating circuit of each hydraulic motor is high, the capacity of the motor is increased and the torque is increased. It is also desirable to drive the traveling means at a low speed, reduce the capacity of the motor when the pressure is low, and drive the traveling means at the torque and high speed.

In the present invention, if the automatic switching valve operates one electromagnetic switching valve provided in the connection circuit and connects the connection circuit to one chamber of the capacity control cylinder, the load pressure of the operating circuit of the hydraulic motor can be controlled. When the automatic switching valve connects the connection circuit to the tank at high speed, the control cylinder automatically connects the one chamber to the tank and operates the cylinder to maximize the capacity of the motor; The sensor sends an electrical signal to forcibly operate the other electromagnetic switching valves, which also controls the other motors to maximize their capacity. As a result, each of the left and right traveling means can operate at low speed at the same time by increasing the capacity of each motor at the same time.

(Embodiment) An embodiment of the present invention will be described with reference to the case of driving the illustrated crawlers. Reference numerals 1 and 2 are a pair of left and right crawlers, 3 and 4 are variable displacement hydraulic motors, and 5 and 6 are variable displacement hydraulic motors. One set drives one crawler. 7, 8, 9, and 10 are operating circuits for each hydraulic motor; 11, 12, 13, and 14 are capacity control cylinders that control the capacity of each hydraulic motor; and the chambers on the rod side of each control cylinder are connected to each operating circuit. The chamber on the head side is provided with electromagnetic switching valves 16, 17, 18, 19 for selectively connecting the chamber to the tank 15 or the operating circuits 7, 8, 9, 10. When each electromagnetic switching valve connects the chamber on each head side to the tank 15, each control cylinder controls the capacity of each hydraulic motor to the maximum, causing the hydraulic motor to operate at high torque and low speed, and When the chambers are connected to the operating circuits 7, 8, 9, and 10, each control cylinder controls the capacity of each hydraulic motor to the minimum, allowing the hydraulic motor to operate at low torque and high speed.

A hydraulic automatic switching valve 21 is interposed in a connection circuit 20 connected to the operating circuit 7 of one of the electromagnetic switching valves 16 of the plurality of electromagnetic switching valves, and the automatic switching valve 21
If the force due to the load pressure of the actuating circuit 7 acting on the piston 22 is smaller than the force of the setting spring, it will connect to the actuating circuit 7 as it is and the connecting circuit 20; When the force is greater than the force, the switch is automatically made to connect the tank 15 to the connection circuit 20. The piston 2
Since there is a difference in the pressure receiving areas on the left and right sides, the automatic switching valve 21 generates a thrust that presses the setting spring, and when the thrust exceeds the force of the setting spring, the automatic switching valve 21 performs an automatic switching operation.

When the automatic switching valve 21 performs a switching operation due to an increase in load pressure and one electromagnetic switching valve 16 is energized and in the switching position, a high load pressure is introduced into the chamber on the head side of the capacity control cylinder 11. , a sensor 2 consisting of a pressure switch operated by the pressure in the chamber.
3, which senses the switching of the automatic switching valve 21 and uses an electric signal to switch the other electromagnetic switching valves 17,
18 and 19 are excited to perform the switching operation.

By switching the other electromagnetic switching valves 17, 18, 19, the load pressure of each hydraulic motor is introduced into the chambers on the head side of the control cylinders 12, 13, 14, and the capacity of each hydraulic motor 8, 9, 10 is changed. Each cylinder 12, 13, 14 operates so as to minimize . This operation occurs almost at the same time when the hydraulic motor 7 is controlled to its minimum displacement by its cylinder 11, and the load pressure of the hydraulic motor 7 is applied to the other pressure motors 8, 9, 10.
Since they operate at the same time even if there is a slight difference in the load pressure, the left and right crawlers can be shifted to low speed at the same time.

The sensor 23 is provided at a location where pressure fluctuation occurs due to switching of the automatic switching valve 21, and in the illustrated example, the sensor 23 is provided in a connection circuit 20 connected to a chamber on the head side of the capacity control cylinder 11. However, in this example, when the electromagnetic switching valve 16 is energized and the head side and rod side chambers of the capacity control cylinder 11 are in communication state, the automatic switching valve 21 is connected to the connecting circuit 2.
0 to the tank 15, the pressure in the chamber on the head side of the capacity control cylinder 11 drops to the tank pressure, and this pressure drop causes the sensor 23 to send an electric signal to the other electromagnetic switching valves 17, 18. , 19, and the signal causes these electromagnetic switching valves 17, 18,
19 become excited all at once, and the head side chambers of the capacity control cylinders 12, 13, 14 communicate with the tank, and as a result, all the capacity control cylinders 11, 12,
13 and 14 are the hydraulic motors 3, 4, 5, and 6 all at once.
Control operation is performed to cause the motor to operate at high torque and low speed.

When one electromagnetic switching valve 16 is artificially demagnetized, an electric signal is sent from the sensor 23 to the other electromagnetic switching valve 1.
7, 18, and 19, and the hydraulic motors 3, 4, 5, and 6 simultaneously operate at high torque and low speed, as in the above case.

(Effect of the invention) According to the invention, one chamber of the displacement control cylinder of the variable displacement hydraulic motor that drives the traveling means is connected to the operating circuit via the electromagnetic switching valve,
An automatic switching valve that is operated by the load pressure of the operating circuit is installed in the connection circuit that connects one electromagnetic switching valve to the operating circuit, and a sensor detects switching of the automatic switching valve and also detects the switching of the other electromagnetic switching valve. Since the switching is instructed, the capacity of the hydraulic motors that drive the left and right traveling means can be changed at the same time to change the speed.The control device also includes multiple electromagnetic switching valves, one automatic switching valve, and a sensor. Since it can be constructed from a container, it has the advantage of being relatively inexpensive to manufacture.

[Brief explanation of the drawing]

The drawing is a diagram illustrating an embodiment of the present invention. 1, 2... Crawler, 3, 4, 5, 6... Variable displacement hydraulic motor, 7, 8, 9, 10... Operating circuit, 11, 12, 13, 14... Capacity control cylinder, 15... Tank, 16, 17, 18, 19...
...Solenoid switching valve, 20...Connection circuit, 21...Automatic switching valve, 23...Sensor.

Claims (1)

[Scope of utility model registration request] In a system in which the left and right crawlers and other traveling means are connected to separate variable displacement hydraulic motors, and the displacement of the hydraulic motors is controlled by a displacement control cylinder to control the traveling speed, each displacement control Each cylinder is provided with an electromagnetic switching valve that selectively connects one chamber between the tank and the operating circuit of the hydraulic motor to control the capacity of the hydraulic motor to a maximum or minimum. If the force due to the pressure of the actuating circuit acting on the piston is smaller than the force of the set spring, the connecting circuit is connected to the actuating circuit, but the actuating circuit acts on the piston. When the force due to the pressure of Traveling comprising a sensor that transmits a signal, and an electromagnetic switching valve other than the electromagnetic switching valve in 1 above connected to the sensor by an electric circuit so as to perform a switching operation that minimizes the capacity of a hydraulic motor connected to the electromagnetic switching valve. Speed switching device.