JPH04356283A - Differential epicyclic steering device - Google Patents

Abstract

PURPOSE:To reduce the turning radius of a vehicle using a differential epicyclic steeking device which controls the number of revolution of right and left shafts by means of a hydraulic motor by increasing the difference in the number of revolution between the right and left output shafts of the differential epicyclic steering device. CONSTITUTION:A hydraulic motor 2 is variable capacity type and a controller 5 which in response to signals of a steering lever 6 sends signals to a variable displacement pump 1, the variable capacity motor 2 and a governor controller 12 for controlling engine speed is provided and the discharge of the pump 1 is first increased in accordance with the angle of inclination of the steering lever 6 so as to increase the number of revolution of the motor 2 thereby causing a difference in the number of revolution between output hafts Next the engine speed is lowered to reduce the turning radius of a vehicle and the capacity of the variable capacity motor 2 is reduced so as to increase the engine speed thereby increasing the difference in the number of evolution between the output shafts and enabling pivotal turn.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential planetary steering system for a vehicle, and more particularly to a differential planetary steering system for a tracked construction vehicle such as a bulldozer.

0002

[Prior art] A differential planetary steering device has a clutch and
Since the turning operation is much smoother than that of a brake-type steering device, it has been often used in tracked vehicles. FIG. 3 is a configuration diagram of a conventional differential planetary steering device. Reference numeral 1 denotes a hydraulic variable displacement pump driven by an engine 10, which is connected to a fixed displacement motor 20. The variable displacement pump 1 has a displacement control servo valve 3, and a potentiometer 7 mounted on a steering lever 6 and the displacement control servo valve 3 are connected via a control device 31. 40 is a first planetary device, 50 is a second planetary device, and 60 is a third planetary device. The respective sun gears 41, 51, and 61 are connected. A carrier 43 on which the planet gear 42 of the first planetary device 40 is pivotally attached is connected to a ring gear 54 and an output shaft 45 of the second planetary device 50. The ring gear 44 of the first planetary device 40 is connected to the output shaft of the fixed displacement motor 20. A carrier 53 on which the planetary gear 52 of the second planetary device 50 is pivoted is connected to a transmission device 30 driven by the engine 10. Planetary gear 62 of third planetary device 60
The carrier 63 on which the output shaft 65 is mounted is connected to the output shaft 65, and the ring gear 64 is fixed. Left and right output shaft 4
Brakes 46 and 66 are attached to brakes 5 and 65, respectively. The output shafts 45, 65 are connected to crawler belts via left and right drive wheels (not shown).

[0003] When the carrier 53 is driven by the engine 10 via the transmission device 30, the vehicle runs. When the steering lever 6 is placed in the neutral position, the control device 31 sends a signal from the potentiometer 7 to the displacement control servo valve 3, and the displacement control servo valve 3 controls the variable displacement pump 1 to set the discharge amount to 0. . As a result, the ring gear 44 is fixed and the vehicle moves straight. When the steering lever 6 is tilted, the potentiometer 7 senses the angle and sends a signal to the control device 31.
sends a control signal according to the angle to the displacement control servo valve 3, which controls the variable displacement pump 1 to send oil to the fixed displacement motor 20 and rotate the ring gear 44. This creates a difference in rotational speed between the left and right drive shafts 45 and 65, causing the vehicle to turn. Now, set the vehicle speed to V
, where the gauge width of the left and right tracks is B, and the speed difference between the left and right tracks is ΔV, the turning radius of the vehicle is R = (V/ΔV)×B,
The turning radius R becomes smaller as the speed difference ΔV between the left and right tracks increases. That is, as the rotational speed of the ring gear 44 increases, the speed difference ΔV increases and the turning radius of the vehicle decreases. The discharge amount of the variable displacement pump 1 changes in proportion to the inclination angle c of the steering lever 7 from the neutral position. Therefore, when the inclination angle c of the steering lever 7 is increased, the discharge amount of the variable displacement pump 1 increases, the rotation speed of the fixed displacement motor 20 becomes faster, and the rotation speed of the ring gear 44 becomes faster.
The speed difference ΔV between the left and right tracks increases, and the turning radius R of the vehicle increases.
becomes smaller. Switching the turning direction from left to right is performed by tilting the steering lever 7 from the neutral position to the opposite side, reversing the discharge direction of the variable displacement pump 1, and rotating the fixed displacement sweater in the opposite direction.

0004

[Problem to be solved by the invention] According to the above configuration,
By increasing the discharge amount of the variable displacement pump, the rotation speed of the fixed displacement motor is increased, thereby reducing the turning radius of the vehicle. However, the capacity of variable displacement pumps has limits from both vehicle configuration and economical points of view, and fixed displacement motors have an upper limit on the allowable rotation speed, so there is a limit to the turning radius of the vehicle. , cannot make a pivot turn. Therefore, when towing the scraper, it is difficult to remove soil in narrow spaces or load in corners, and it is difficult to load onto a trailer or move on narrow mountain roads, which limits the scope of work. There was a problem that

The present invention has been made in view of the above problems, and an object of the present invention is to provide a differential planetary steering device with a small turning radius.

[0006]

[Means for solving the problem] In order to achieve the above objectives,
In the first invention of the differential planetary steering device according to the present invention, the differential planetary steering device includes a differential planetary device having left and right output shafts, and a hydraulic motor that controls the rotation speed of the left and right output shafts. The steering device is characterized in that the hydraulic motor is a variable displacement motor, and in the second aspect of the invention, control is provided for receiving a signal from a steering lever and transmitting a signal to an engine rotation speed control device and a hydraulic motor displacement control device. It is characterized by being equipped with a device.

[0007]

[Operation] According to the above configuration, the hydraulic motor of the differential planetary steering device is of a variable displacement type, and the control device receives a signal from the steering lever and transmits a signal for controlling the engine speed and the hydraulic motor displacement. Therefore, the signal from the steering lever lowers the engine speed during turning to reduce the turning radius of the vehicle, and further increases the hydraulic motor speed by reducing the capacity of the hydraulic motor, increasing the speed of the left and right tracks. By increasing the difference and bringing the speed of one track closer to 0, it is possible to make a pivot turn.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a differential planetary steering device according to the present invention, in which 1 is a variable displacement pump and 2 is a variable displacement motor. 3 is a displacement control servo valve of the variable displacement pump 1, and 4 is a displacement control servo valve which is a hydraulic motor displacement control device. The variable displacement pump 1 and variable displacement motor 2 are connected. Reference numeral 5 denotes a control device, which is connected to a potentiometer 7 mounted on a steering lever 6. The inclination angle a of the steering lever 6 is in the range for slow turning, and the inclination angle b is in the range for sharp turning. The control device 5 includes capacity control servo valves 3 and 4.
It is also connected. 10 is an engine, 11 is an engine governor control actuator that controls the rotation of the engine, and 12 is a governor controller that is an engine rotation speed control device, which is connected to the engine governor control actuator 11 and the control device 5. are doing. The variable displacement pump 1 is connected to the engine 10, and the variable displacement motor 2 is connected to the ring gear 4 of the first planetary device 40 described above.
4, but since this part is the same as the conventional one, illustrations and explanations will be omitted.

Next, the operation will be explained with reference to FIG. The vertical axis of FIG. 2 is the vehicle speed, the center is the average vehicle speed Vm, the left side is the left crawler speed Vl, and the right side is the right crawler speed Vr. When the steering lever 6 is placed in the neutral position, the control device 5 is activated by a signal from the potentiometer 7.
sends a signal to the displacement control servo valve 3 to set the discharge amount of the variable displacement pump 1 to 0, and as shown in FIG. 2(a), the speed difference between the left and right tracks is set to 0 and the vehicle moves straight. When the steering lever 6 is tilted within the range of tilt angle a, the potentiometer 7 senses the angle and sends a signal to the control device 5, and the control device 5 outputs a control signal according to the angle in a variable manner as in the conventional device. Volume control servo valve 3 of volume pump 1
to operate the variable displacement pump 1 and drive the variable displacement motor 2 to change the speed of the left and right tracks as shown by the solid line in Fig. 2(b), giving a speed difference ΔV = Vr - Vl to move the vehicle. Swirl. The above operation is the same as the conventional one.

When the steering lever 6 is further tilted to enter the range of inclination angle b, the control device 5 receives a signal from the potentiometer 7, sends a signal to the governor controller 12, controls the engine governor control actuator 11, and starts the engine. The rotational speed is lowered and the vehicle speed is reduced from the dotted line to the solid line as shown in FIG. 2(c). The above-mentioned turning radius formula R
As is clear from =(V/ΔV)×B, even if ΔV is constant, if the vehicle speed V decreases, the turning radius R decreases, so
At this stage, the turning radius becomes even smaller. When the steering lever 6 is further tilted, the control device 5 sends a signal according to the tilt angle to the displacement control servo valve 4 to reduce the displacement of the variable displacement motor 2. As is well known, by reducing the capacity of a hydraulic motor, the allowable rotation speed can be increased. Therefore, by reducing the capacity of the variable displacement motor 2 in accordance with the inclination angle of the steering lever 6, the rotation speed increases, and the speed difference ΔV between the left and right tracks further increases as shown by the solid line in FIG. 2(d). If the speed is low, eventually the crawler track on one side will almost come to a standstill and the vehicle will make a pivot turn. Even at high vehicle speeds, the turning radius is significantly reduced compared to conventional systems.

[0011]

[Effects of the Invention] As described in detail above, the present invention uses a variable displacement type hydraulic motor for a differential planetary steering device, and controls the engine rotation speed and the hydraulic motor displacement according to the tilt of the steering lever. Therefore, the turning radius of the vehicle can be significantly reduced, turning on a pivot point is possible at low speeds, and work and movement in narrow spaces are facilitated, providing a differential planetary steering device that is not subject to limitations on the working range.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a differential planetary steering device of the present invention.

FIG. 2 is a graph for explaining the turning operation of the present invention.

FIG. 3 is a configuration diagram of a conventional operating planetary steering device.

[Explanation of symbols]

1 Variable displacement pump 2 Variable displacement motor 3, 4 Displacement control servo valve 5 Control device 6 Steering lever 7 Potentiometer 10 Engine 11 Engine governor actuator 12 Governor controller

Claims (2)

[Claims] 1. A differential planetary steering device comprising a differential planetary device having left and right output shafts, and a hydraulic motor that controls the rotation speed of the left and right output shafts, wherein the hydraulic motor is a variable displacement motor. A differential planetary steering device characterized by: 2. The differential planetary steering device according to claim 1, further comprising a control device that receives a signal from the steering lever and sends a signal to an engine speed control device and a hydraulic motor displacement control device.