JPS6343260Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a traveling drive device for construction machines such as hydraulic excavators, and other machines having a traveling function.

Figures 1 and 2 show a conventional travel drive system for a hydraulic excavator, in which 1 is the upper revolving body of the hydraulic excavator, 2 is a cab provided on the upper revolving body 1, and 3 is a driver's seat inside the cab 2. A switching lever 4 for operating the oil pressure switching mechanism c of the transmission mechanism a is provided on the lower traveling body of the hydraulic excavator, and the left and right independent two-speed motors 5 and 6 disposed on the lower traveling body 4 are The speed is changed by the transmission mechanism a via the hydraulic switching mechanism c operated by the switching lever 3, and the speed can be changed between a low traveling speed with a large tractive force and a normal high traveling speed, and the speed of the traveling drive device is changed. As shown in FIG. 2, the specific structure includes hydraulic pumps 11 and 12 that supply hydraulic pressure to the two-speed traveling motors 5 and 6 and other hydraulic actuators;
control valve 13 for distributing hydraulic pressure of 12;
14. Directional switching valves 15 and 1 that distribute the driving hydraulic pressure of the two-speed traveling motors 5 and 6 to the hydraulic cylinders 17 and 18
6, that is, hydraulic switching mechanism c, hydraulic cylinders 17, 18
That is, it is constituted by a transmission mechanism a for two-speed traveling motors 5 and 6, an operating mechanism d for a hydraulic switching mechanism c consisting of a pilot pump 19 and a switching valve 20 operated by a switching lever 3.

Therefore, in the traveling drive system described above, the traveling 2 is transmitted to the transmission mechanism a via the hydraulic switching mechanism c.
The two-speed traveling motors 5, 6 are held at high and low speed positions by the transmission mechanism a by the drive oil pressure of the speed motors 5, 6, and switching between high and low speeds is controlled by the pilot pump 19 and the hydraulic pressure from the pilot pump 19. The speed switching device is constituted by an operating mechanism d consisting of a switching valve 20 operated by a switching lever 3 in contact with and disconnecting from the hydraulic pressure switching mechanism c.

However, in the conventional traveling drive device described above, the pilot pump 19, the switching lever 3, the switching valve 20
Therefore, the speed switching device is complicated, and the driver has to operate the switching lever 3 to change the speed, making the operation troublesome.

The present invention relates to a device for solving the above-mentioned difficulties in a traveling drive device for construction machinery, etc., and the traveling drive device for construction machinery, etc. is equipped with independent left and right traveling motors whose speeds are changed by a transmission mechanism. It is characterized by being equipped with an automatic speed switching device consisting of a drive oil pressure detection mechanism that detects and outputs the drive oil pressure of the motor, and an oil pressure switching mechanism of the transmission mechanism that is automatically operated by the drive oil pressure detection mechanism. Its purpose is to detect the drive oil pressure of the travel motor by focusing on the fact that the drive oil pressure of the travel motor is high when traveling at low speed while being towed, and is low during normal high speed travel. The object of the present invention is to provide a travel drive device for construction machinery, etc., which can automatically switch a travel motor between high and low speeds.

The present invention has the above-mentioned configuration, and when the drive oil pressure of the travel motor increases due to an increase in load during towing, etc. (when it exceeds the set pressure), the drive oil pressure detection mechanism detects and outputs the drive oil pressure. , the hydraulic switching mechanism is automatically operated, the transmission mechanism is switched, and the drive motor is shifted to a low speed. Also, when the drive oil pressure of the drive motor becomes low (lower than the set pressure), the drive motor automatically changes to a high speed. Since the speed is changed, the driver is freed from the hassle of changing speeds, and
Excessive load on the traveling drive device is immediately eliminated and smooth running performance is achieved.

Further, in the present invention, automatic speed switching is possible using a drive oil pressure detection mechanism consisting of a pressure control valve that detects and outputs the drive oil pressure of the travel motor, and the structure is extremely simple and practical.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows an embodiment of the traveling drive device of the present invention, in which 5 and 6 are independent left and right traveling motors (two speeds shown), and 11 and 12 are traveling motors 5 and 6 and other hydraulic actuators (not shown). 13 and 14 are control valves that distribute the hydraulic pressure of the hydraulic pumps 11 and 12, and 15 and 16 are control valves that distribute the hydraulic pressure of the travel motors 5 and 6 to hydraulic cylinders 17 and 18. A supply direction switching valve, that is, a hydraulic switching mechanism c, a hydraulic cylinder 17,
18 is a transmission mechanism a for the traveling motors 5 and 6;
In this embodiment, the hydraulic pressure switching mechanism c includes a pressure control valve 21 that detects and outputs the drive oil pressure of the travel motors 5 and 6, and circuits C and C that supply the same drive oil pressure as pilot pressure for the directional control valves 15 and 16. , c is equipped with a drive oil pressure detection mechanism b that automatically operates the hydraulic pressure detecting mechanism b. In the figure, A is a drive hydraulic circuit to the pressure control valve 21, B is a pilot pressure circuit, and D is a return circuit.

The illustrated embodiment of the travel drive device has the above-described structure, so the hydraulic pumps 11, 12
The hydraulic pressure is cut off by the control valves 13 and 14 and is not supplied to the travel motors 5 and 6.
When drive oil pressure is not applied to the left and right travel systems, the predetermined oil pressure is not applied to the pilot circuit of the pressure control valve 21, so the pressure control valve 21 is in the state shown in FIG. Since the pilot pressure is not applied to the directional control valves 15 and 16 from the circuits C and C, the directional control valves 15 and 16 are also in the position shown in the figure, and the hydraulic pressure for switching between high and low speeds of the travel motors 5 and 6 is As shown in the figure, the cylinders 17 and 18 communicate with the drive hydraulic circuits of the travel motors 5 and 6 to maintain the travel motors 5 and 6 at high speed.

From this state, if one or both of the control valves 13 and 14 is operated to send hydraulic pressure from one or both of the hydraulic pumps 11 and 12 to one or both of the travel motors 5 and 6, one or both of the travel motors 5 and 6 is driven, and is also transmitted to one or both of the hydraulic cylinders 17, 18 via the directional control valves 15, 16, and the travel motors 5, 6 are maintained at high speed. At this time, the travel motor 5 or 6
The higher drive oil pressure is applied to the pressure control valve 21 from circuit A.
It is transmitted to The drive oil pressure of the travel motors 5 and 6 applied to this pressure control valve 21 becomes pilot pressure from the pilot circuit, and that pilot pressure is the set pressure of the pressure control valve 21 (in the case shown, it is set by a spring).
When the pressure control valve 21 is in the state shown in the figure, the driving oil pressure is lower than the direction control valves 15 and 1.
6, and the traveling motors 5 and 6 remain at high speed.

However, during towing, etc., the load increases and the driving oil pressure of one or both of the left and right independent travel motors 5, 6 increases, and the increased driving oil pressure becomes the pilot pressure of the pressure control valve 21 and controls the set pressure. When the pressure control valve 21 is switched to the right, the increased drive oil pressure is transmitted to the circuits C and C, and the directional control valves 15 and 16 are switched upward, causing the travel to the hydraulic cylinders 17 and 18. The supply of drive oil pressure to the motors 5, 6 is reversed, the hydraulic cylinders 17, 18 are operated, and the travel motors 5, 6 are maintained at low speed. Further, when both of the driving oil pressures of the left and right traveling motors 5 and 6 become lower than the set pressure of the pressure control valve 21, the traveling motors 5 and 6 are automatically maintained at the high speed as described above.

Therefore, according to the illustrated embodiment, when the drive oil pressure of the travel motors 5 and 6 increases (when it exceeds the set pressure) due to an increase in load during towing, etc., the pressure control valve 21, that is, the drive oil pressure detection mechanism b detects and outputs the drive hydraulic pressure, automatically operates the directional control valves 15 and 16, that is, the hydraulic pressure switching mechanism c, and switches the hydraulic cylinder 1.
7, 18, that is, the transmission mechanisms a, a are switched to shift the traveling motors 5, 6 to low speed, and the traveling motors 5, 6 are changed to low speeds.
When the drive oil pressure of the drive motor 6 becomes low, the drive motors 5 and 6 automatically increase the speed, which eliminates the need for the driver to change the speed and relieves the driver of the trouble. Since the system detects and operates, the gears can be changed quickly, and excessive load on the travel drive device is quickly eliminated, resulting in smooth travel.

Furthermore, compared to conventional mechanisms, complicated mechanisms such as pilot pumps and switching levers are not required, and the system has the practicality of being able to automatically switch speeds with an extremely simple structure.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a hydraulic excavator, FIG. 2 is a mechanical explanatory diagram of a conventional travel drive device for a hydraulic excavator, and FIG. 3 is an explanatory diagram of an embodiment of the travel drive device of the present invention. 5, 6: Travel motor (2nd speed), 11, 12: Hydraulic pump, 13, 14: Control valve, 1
5, 16: Directional switching valve, 17, 18: Hydraulic cylinder, 21: Pressure control valve, a: Transmission mechanism 17, 1
8, b: Drive oil pressure detection mechanism 21, c: Switching mechanism 1
5,16.

Claims (1)

[Scope of utility model registration request] In a travel drive device for construction machinery, etc., which is equipped with independent right and left travel motors whose speeds are changed by a transmission mechanism, there is provided a drive oil pressure detection mechanism that detects and outputs the drive oil pressure of the travel motor, and a drive oil pressure detection mechanism that detects and outputs the drive oil pressure of the travel motor. 1. A traveling drive device for construction machinery, etc., comprising an automatic speed switching device comprising a hydraulic switching mechanism of the transmission mechanism that is automatically operated by the transmission mechanism.