|Tractor News > 1998|
How to Rebuild and Restore Farm Tractor Engines
Valtra launches HiTech tractor modelsValtra - October 20, 1998
The clutch pedalīs retirement Meeting customerīs requirements is the keystone of Valtraīs philosophy. Embedded in the power transmissions of powerful, productive tractors are many different philosophies from the purely mechanical transmission to stepless CVT controls. Valtraīs approach is, by using the latest technology, to combine the reliability of a mechanical transmission with powershift speed and shuttle control - HiTech.
Valtraīs new HiTech power transmission is based on the widely acknowledged properties, reliability coupled with ratios giving excellent basic working speeds, of our 12-speed synchromesh transmission. Valtra also recognises it is essential to be able to regulate speed and direction, even under load, without the use of a clutch pedal and has concentrated on developing these properties using latest technology.
The new, HiTech, transmission is fitted with sensors which provide various function details including load and hydraulic oil temperatures to the on-board computer. The driver uses simple controls to send commands to the computer which, in turn, immediately carries out the orders while automatically making adjustments to suit operating circumstances. The computer capacity corresponds to the fastest portable micro-computers handling 64,000 lines per second so there is more than sufficient capacity available.
A hundred checks during the shift Normally powershift settings in epicyclic transmissions are predetermined assuming optimum oil temperatures and with a solenoid valve effecting the change. However, depending on climate and use lubricant temperatures will vary considerably, particularly in exceptionally cold weather. A transmission with insufficient temperature compensation will malfunction if the oil is exceptionally cold and/or viscous resulting in uneven and uncomfortable ratio changes.
The new Valtra HiTech system is completely computer controlled with the pressure of the Delta Powershift multi-disc clutch regulated proportionally up to 100 times during each gear shift which itself, only lasts for 0.2 to 0.4 seconds, depending on conditions. The result is excellent, performance with smooth, quick changes in direction.
As an added aid to productivity Delta Powershift may also be pre-programmed for shuttle operations such as when loading or manoeuvering on a headland, with the operator able to pre-select a different powershift operating speed in reverse to that used forward. This is selected with a simple push-button located in the shuttle control console.
The Delta Powershift controls remain as before, in the top of the gear levers.
The end of the clutch pedal? Gear selection with HiTech is achieved with the assistance of New Generation HiShift push-buttons on the gear levers rather than the clutch pedal. The clutch button is pushed as the gear lever is shifted to a new position. An electronic signal is sent to the computer which, in turn, activates the clutch via the proportional valve. The result is a smooth shift throughout the gear range. HiTech transmissions now incorporate two clutches, one for forward and one reverse. This design disburses heat much more evenly than the traditional single clutch, particularly during shuttle operations. Locating the clutches in the HiTech section of the transmission rather than on the engine reduces gearshift effort.
The HiTech system also ensures that incorrect operation of the transmission is prevented. For example, if reverse is selected by mistake at road speeds the tractor will slow down and only engage once a safe speed has been reached.
The clutch pedal remains in itīs traditional position for safety purposes, emergencies and for starting the engine.
A new generation parking brake As part of Valtraīs philosophy of meeting individual customers needs the HiTech shuttle controller may be positioned on either the left or right of the steering wheel. The joystick handle has four positions; forward - reverse - neutral - park. Simultaneously pulling the collar of the stick while depressing the joystick in the neutral position engages the parking brake. A finger light operation which can help to avoid risky situations.
Should the driver forget to engage the parking brake it will automatically engage when the engine is switched off.
"Semi-Automatic operation" It is the nature of tractor operations that in a particular task only a limited range of speed variation is required. With HiTech the driver can choose from three operating modes; manual control, field or transport. In manual control the driver selects both gears and Delta Powershift speed. In field or transport settings the Delta Powershift speed will be automatically selected to give maximum output (field setting) or economy (transport setting. Features enhanced by the high torque reserves of the latest Valmet engines.
Located on the right front pillar a clear digital display screen provides information on HiTech operations. These include chosen direction, the powershift mode in use and driving speed. When stationary the information includes external temperature. When Delta Powershift is in automatic mode the display will, under extreme conditions, advise the drive to change the mechanical base speed up or down to give greater output or a more economical speed.
The display also provides a coded diagnoses for irregular functions.
Smooth PTO engagement The engagement of the PTO is now regulated by the proportional valve to ensure smooth engagement regardless of implement load. This feature greatly prolongs the life of universal joints and moving parts of the implement.
A filter on the return side of the hydraulic system ensures no contamination can enter the system when implements are connected through the quick-couplers.
A green engine philosophy Three years ago Valtra introduced the Permatorque range of engines with almost 40% torque increase. A most notable feature of these engine is their torque at low revolutions, around 1,000rpm, about 40% higher than at maximum output.
The New HiTech models are equipped with the latest E versions of the Valmet diesel engine range. These engines meet all current EU emission standards and those which come into force in the year 2000. Flagship of the Valmet engine range is the new 7.4L Valmet DSBIE powering the 160/200 hp Valtra Valmet 8950 Sigma Power.
Valtraīs ongoing development of itīs engine range underlines their commitment to fuel economy and efficiency coupled to a responsible approach to environmental matters. Both to their customerīs advantage. The Valmet engine is one of the most highly valued in the field of agricultural machinery and is used in top tractor models from Agco-Allis, Massey Ferguson, Steyr, Case and Landini along with other leading self propelled machinery.
Aires - An air suspension for front axles The Valmet tractor has been highly rated in many independent tests. The driver can rightly feel that he is a person of importance, king in his own domain.
While other tractor manufacturers have developed front suspensions based on hydraulic accumulators, Valtra engineers have taken a different approach and decided the long term future lies in air suspension. This technology, well known and proven in heavy trucks, works well, even in the extreme conditions of the Nordic winter and is far superior when the front axle loading is constantly changing.
With the introduction of Aires air suspension, comfort and therefore work efficiency is increased considerably. Developed for the 6-cylinder Mega series the front axle is fitted to a sub-frame pivoting on bearings at one end and air suspension with shock absorbers at the other.
All Aries models have a compressor as part of their standard equipment which may also be used to power trailer brakes, adjusting tyre pressures and cleaning the tractor.
Exceptionally user friendly Thirty years ago Valtra were the first tractor manufacturer to introduce an ergonomically designed and integrated cab. Today the Valtra Ergocab with itīs new dashboard design and interior colour scheme remains a leader in driver comfort. The even floor allows the seat to swivel a few degrees to make monitoring rear mounted equipment a more comfortable task or through 180° for TwinTrac reverse drive operations. A feature which increases tractor productivity considerably.
Introduction of the HiTech transmission has made the tractor easier to manage. The combined forward/reverse and parking brake control is located directly below the steering wheel and can be fitted on either side according to customer requirements. A feature that underlines Valtraīs commitment to customer choice and service.
Entry to the cab is up three steps for increased safety with the lower step folding up if required for forestry operations and when working with tall crops or heavy windrows of grass or straw.
Forestry cab Valmet tractors with their Ergo Cab have proved exceptionally versatile and many have been fitted with forestry cranes and processors. Valtra engineers have now installed roof windows, one at the rear and one each side, made of polycarbonate to meet operatorīs requests for greater areas of vision. A sun roof of the same material may also be fitted. A heating console is located between the roof windows and the standard side windows to ensure efficient defrosting and demisting. A strong tubular frame surrounds the cab roof to protect the windows.
The forest cab is an option on the new four cylinder 6850, Valtra Forest models and the six cylinder Mega models 8050 to 8950.