DE19529762A1 - Hydraulic control valve for hydrostatically driven work vehicle e.g. remotely controlled grass-cutting machine - has number of directional flow spool valves in block to control pair of drive motors coupled to wheels - Google Patents

Abstract

A hydraulically powered machine, such as a remotely controlled grass cutter, has hydraulic motors mounted as drives to the wheels. Fluid is supplied to the motors via a valve block that directs flow from a pump [P]. The block has outputs [ML-,ML-,ML+,MR+] to the motors and a return port [T] coupled to the tank. Within the block are spool valves controlled to direct the fluid for the various modes of operation, eg forward,reverse, left,right, brake, stop.

Description

The fluid motors of hydrostatically driven machines, in particular from remote controlled grass mowers u. Ä. via a so-called bypass control being controlled.

Here, the fluid flow supplied to the fluid motors becomes that of the fluid pump branched fluid flow coming, the rest is returned to the system tank. If the fluid flow supplied to the fluid motors via a valve unit is large, that is The speed of rotation of the fluid motors is large, and so is the driving speed the work machine big.

The work machine has a hydraulic motor on each side. By different Filling the hydraulic motors results in a steering movement of the implement. A valve unit with the bypass control mentioned above can do the following Driving positions can be set continuously: slow or fast straight forward or Reverse travel, slow or fast left or right cornering.

The inventive idea lies primarily in the combination of the previously mentioned Control options with three additional switch positions that are necessary for operation of an implement such as a grass mower are indispensable.

Figure 5 shows the hydraulic circuit diagram.

These are:

When the fluid pump is at a standstill, the device should be easy to roll, for this purpose the inlets and outlets of the fluid motors must be connected to each other ( Figure 2).

When the fluid pump is running and the control is in neutral position, the device must be braked so that it can e.g. B. standing on a slope does not automatically pick up speed ( Fig. 3). The initiation of a forward or reverse drive cancels the braking effect if a working pressure set by the spring element between the fluid pump and the hydraulic motors is exceeded ( Figure 4). If the working pressure drops while driving, if e.g. For example, the downhill force accelerates the device also in the direction of travel, the (brake) valve spool closes (Figure 1 / Pos. 13), the forward and return runs of the fluid motors (figure 5), until again a working pressure between the pump and motor is built.

The speed of the device is checked in this way and also corresponds during a downhill descent of the set amount of fluid.

The underlying the invention, the valve block diagram of Figure 1 shows how the required control functions can be executed. Figure 2 shows the valve position in the fluid pump status - the device can be rolled. For this purpose, the (brake) valve slide ( Fig. 1 / Item 13 ) is in switch position 0, the inflows and outflows of the fluid motors are interconnected.

Figure 3 shows the valve position when the fluid pump is running, the device is braked. For this purpose, the (brake) valve spool ( Fig. 1 / Item 13 ) is in switch position 1, the inflows and outflows of the fluid motors are separated from each other.

Figure 4 shows the valve control for unchecked forward travel with a left curve. For this purpose, the (brake) valve spool ( Fig. 1 / Item 13 ) is in switch position 2, whereby the inlets of the fluid motors are connected to the fluid pump and the outlets of the fluid motors are connected to the tank. The (directional) valve spool ( Fig. 1 / Pos. 2 ) is in position L, the (travel) valve spool ( Fig. 1 / Pos. 3 ) is in position V.

The (brake) valve spool ( Fig. 1 / Item 13 ) is designed so that it is adjusted via the fluid pressure acting on its right end. The measuring element is a spring element ( Fig. 1 / Item 17 ).

At fluid pressure 0 the (brake) valve spool ( Fig. 1 / Pos. 13 ) is in position 0 ( Fig. 2), at low fluid pressure in position 1 ( Fig. 3) and at high fluid pressure in position 2 ( Fig. 4).

Claims (2)

1. Control valve for the control of a hydrostatically driven machine such. B. a grass mower with remote control, characterized in that it consists of a valve block with three built-in valve spools, of which the first ( Fig. 1 / Pos. 2 ) controls left and right cornering, the second ( Fig. 1 / Pos. 13 ) the function Rolls with the fluid pump stopped, brakes with low fluid pressure and brake release with high fluid pressure controls and the third ( Fig. 1 / Item 3 ) controls forward travel, standstill and reverse travel. 2. Control valve according to claim 1, characterized in that the second valve slide ( Fig. 1 / Pos. 13 ) assumes its switching position as a function of the fluid pressure, with a spring element acting as a measuring element.