Marginal Column

The tractor – An all-purpose tool that can boost yields

July 2012

 
 
 

The tractor is agriculture’s Swiss Army Knife. In addition to functioning as a prime mover, tractors also serve as a mobile energy source and control center for a wide variety of attached implements – like plows, hay tedders, and mowers. The tractor’s potential for supporting the farmer, conserving resources, and boosting productivity are just as diverse. Because at the end of the day, what counts is what’s in the farmer’s barn.

Electrohydraulics and electronics

Modern electrohydraulics and electronic controls offer numerous options for adding new functions to make tractor operation simpler and more convenient, and thus to raise productivity. Rexroth delivers the entire range, from individual control units at auto industry quality to complete electrohydraulic packages, from standard software to custom-programmed, user-specific solutions.

Modern drives

Clutching and shifting sometimes make driving a tractor more than exhausting. That is why automatic transmissions and continuously variable transmissions (CVT) are being installed ever more frequently. They ease the burden, improve results, reduce consumption, and raise productivity. In addition to hydraulic concepts for CVTs, Bosch Rexroth also offers tractor manufacturers support in the control and automation of power-shift and power-shuttle transmissions and differentials.

Thrifty working hydraulics

The need to save energy rises as fuel prices climb. In the hydraulics used to do the actual work, load sensing systems in combination with adjustable-displacement pumps are a key to improved energy efficiency. If the job calls for less than full hydraulic capacity, then the load sensing system can drastically reduce the amount of energy which has previously been lost in the form of waste heat. In the upper performance classes, load sensing technology using A10 pumps by Rexroth has already become standard equipment. The model A1VO axial-piston, variable-displacement pumps make it possible for smaller tractors to profit from this technology, too.


Electrohydraulic hitch control EHR

Illustration | Bosch Rexroth AG

The EHR makes it possible to raise and lower the hitch with great precision.

 

Up through the middle of the 20th century, implements were usually raised and lowered with a hand-powered lifting device. Due to increasing performance demands and the size of the units, a hydraulically powered lift soon came to be standard (the first having been invented by Irishman Harry Ferguson). This powered lift was already capable of adjusting the tractive force and setting the position not separately, but together. Today’s type EHR hitches are more flexible in technical terms and are standard equipment in medium-sized and large tractors. Rexroth supplies the components for the entire system, including regulator valves, control units, the operating panel, and sensors. The electrohydraulic hitch control makes it far easier for the driver to handle any of the implements used. Exact force and position regulation enables accurate lifting and lowering of the hitch and that makes for precision when working the soil. In the single-action EHR, it is primarily the implement’s weight that determines how quickly it penetrates the soil.

Double works better – EHR-dw

The double-acting version of the EHR can also apply force actively and under close control – at user-adjustable pressures of between 0 and 50 bar. This is advantageous in dry, hard soils. With the help of the pressure applied by the EHR, the implement can penetrate the soil far more quickly and in that way achieves the desired working depth while optimizing handling under the surface – even where the soils are hard and irregular in structure. What’s more, the EHR-dw makes lowering the hitch and detaching implements more convenient and much faster. In addition to simplifying the farmer’s work, the system also makes for perfect soil handling and contributes to improving yields.


Simple setting – AHC automatic hitch control

Illustration | Bosch Rexroth AG

The AHC dynamically coordinates position and tractive force.

 

When using the AHC software module, the farmer need only set the required working depth and can then concentrate entirely on driving. The driver selects the perfect travel speed while the AHC controls –automatically and dynamically – the relationship between tool position and tractive force. This makes sure that the work is done perfectly and that maximum productivity is achieved. The EHR automatically adapts to varying soil conditions, but individual adjustments can still be made in the manual mode.


Following contours perfectly – PRC pressure relief control

Illustration | Bosch Rexroth AG

With PRC, the front hitch follows ground height exactly.

 

The PRC hydraulic pressure relief control lets the front hitch follow the ground’s contour exactly, protecting both the soil and the equipment. It reduces wear and fuel consumption and optimizes results. The adjustment is made, either manually or automatically, from the operator’s cab. With PRC, implements can be attached faster and more easily, since the relief springs usually present are not needed.