Technology
··6 mins read

Silky-smooth gear changes

Clutch valves for power shift transmissions

Automated gear changes make driving a pleasantly simple experience for users of agricultural and construction machines. Juri Buss, Product Manager Off Highway Solutions at Thomas, explains how clutch transmission valves contribute to this and what the key factors are.

What do clutch transmission valves do and what is important to note?

Editorial team
Thomas magazine
Power shift transmissions are preferably fitted in agricultural and construction machines. When shifting under load, sensitive clutch modulation is crucial.
In this process, the gears are actuated electrically and shifted hydraulically. In hydraulic shifting, precise clutch operation guarantees that the gears are shifted gently and smoothly. The oil pressure is controlled using clutch transmission valves. This is why the precise pressure regulation achieved using such valves, among other things, makes such a big difference in the quality of the driving experience. But you also need to consider how much installation space is available for control blocks and valves. It’s more limited in small tractors, for instance, than in large dump trucks.
Juri Buss
Product Manager OHS

What clutch transmission valve solutions does Thomas have to offer?

Editorial team
Thomas magazine
I touched on the limited amount of installation space that’s available. In terms of design size, the directly controlled PPCD08 and PPCD09 valves from Thomas are the most compact clutch valves available on the market. At 30 l/min, the flow capacity achieved by the PPCD09 is highest by comparison. Even under load or when the oil is still cold, the user is offered the fastest possible clutch operation without noticeable delays in shifting. This soft and fast shifting is only enabled thanks to the valves‘ precise torque transfer and low flow resistance. They establish very precise and stable pressure regulation. The valve control pressure is insensitive to supply fluctuations, which makes the valves easy to integrate into different customer systems. The PPCD08 and PPCD09 valves have generally proved very robust in operation. They are designed to be resistant to dirt and are insensitive to temperature fluctuations and vibrations. High durability under extreme conditions is very important, especially for construction vehicles or in the agricultural sector.
Juri Buss
Product Manager OHS

What do you focus on in product development in cooperation with your customers?

Editorial team
Thomas magazine
When customers provide us with insights into their systems so that we can develop well-coordinated solutions, I consider it to be a major indication of trust. Openness in dealing with one another is essential. In a joint project, each party should be on the same page about the current status, challenges, and solution options. Our internal simulation, testing, and sample construction enables us to supply our customers quickly with the analyses or samples they need and to actively drive projects forward. Our Thomas modular construction principle also enables existing products to be adapted inexpensively to the customer’s specific needs without time-consuming development work. Ultimately, quality is the most important aspect for customers. As an automotive industry supplier with decades of experience, Thomas meets the high quality standards of the automotive sector. These are the benchmark at Thomas, including when it comes to the manufacture of products in the off-highway sector.
Juri Buss
Product Manager OHS

Product properties

Optimized spool guidance for best hysteresis

CFD optimized geometry for maximal flow capability

Reduced magnetic sticking during clutch disengaging

Filter screen for large particles

Hardened spool/sleeve for best performance in contaminated Oil

Flat flow-map for flow independent control pressure

Reduced leakage to minimize effect of silting

Optimized spool guidance for best hysteresis
CFD optimized geometry for maximal flow capability
Filter screen for large particles
Hardened spool/sleeve for best performance in contaminated Oil
Flat flow-map for flow independent control pressure
Reduced magnetic sticking during clutch disengaging
Reduced leakage to minimize effect of silting
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Thomas Modular
System

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