29 November 2017, 15:52
Whether in ag, construction, material handling, mining, marine or industrial, OEMs strive to increase productivity and quality, reduce design and ownership costs, as well as increase the value of their machinery. To address the OEMs’ needs and help them advance regarding technology and differentiation, Poclain has designed the new range of High-Performance transmissions.
The MHP motor design is the result of many years of design and validation. It sets a new standard in the cam-lobe motor principle in terms of performance, reliability and fuel consumption.
The MHP series is available in five sizes: the MHP11, MHP13, MHP17, MHP20 and MHP27; their displacements range from 0.9 liters (55 cu.in) to 3.5 liters (214 cu.in) per rev.
They boast unprecedented speed and power levels, two key requirements that increase machine performance. The MHP motors are qualified to operate up to 500 bar (7250 psi).
Poclain Hydraulics engineers were able to maintain the features of the cam-lobe technology, which has been the foundation of Poclain’s reputation for the last thirty years.
The new modular range is made of three sub-assemblies:
The torque module: it converts the power from hydraulic to mechanical
The valving: it integrates the displacement selector and the boosted hydrostatic brake
The bearing support: it bears the external loads and incorporates the range of parking and dynamic brakes
The torque module integrates all the design and manufacturing expertise Poclain Hydraulics has accumulated since the first generation of motors in 1958.
New design software enabled engineering to develop and characterise the module parts precisely. The validation tests confirmed the simulations, which forecasted over 50% increase of performance levels regarding speed and transmissible power. Meanwhile, the MHP motors maintain high-efficiency levels in each displacement.
The key feature associated with the Poclain Hydraulics technology is to provide near stable efficiency regardless of displacement. The MHP does just that, exceeding 90% overall efficiency over a broad operating range, in reduced as well as full displacement and at a maximum speed of 250 revolutions per minute.
In its simplest version with a fixed displacement motor, the valving cover provides large inlets and outlets on a single flat surface.
Thus the pressure drops in the connectors and hoses are limited, and additional blocks are easily mounted directly onto the motor.
In the MHP series, the nominal ratio between full and smallest reduced displacement for a given motor size is either 3 or 4 depending on the models.
The cam-lobes are individually connected to the high-pressure circuit of the pump to enable multiple displacement shifts. With a motor consisting of eight lobes, each one is connected to the high-pressure circuit to obtain the maximum displacement. Only two lobes remain connected to render a quarter of the displacement. The other six lobes are fed by the low-pressure circuit of the pump.
The MHP 20 and 27 integrate eight lobes, which are grouped by two or three lobes.
The sizes 11, 13 and 17 integrate six lobes grouped two by two.
The more sophisticated valving versions feature the same flat connecting surface and provide several displacement ratios to meet the application requirements.
The valving unit is available in a number of different configurations allowing for a wide range of displacement ratios:
Symmetrical twin displacement with a nominal ratio of 2.67 (3/8) for sizes 20 and 27 and 3 (2/6) in sizes 11, 13 and 17.
Three displacements with two configurations for the MHP 20 and 27: 8/5/3 or 8/5/2 active cams. For sizes 11, 13 and 17, the ratios are 6/4/2.
Four displacements with an 8/6/4/2 configuration, only available in sizes 20 and 27.
The valving unit can also integrate optional functions such as an integrated exchange valve, speed monitoring, and boosted braking.
Boosted braking is available with the two and four displacement versions. It allows for reinforced hydrostatic braking capabilities of the vehicle by using all of lobes of the cam while braking, even when the motor is operating in the smallest displacement.
The bearing support
It is designed to withstand the high external load and efforts that are associated with increasing machine speed and tire load capacity.
The bearing support can integrate a disc brake between the two rows of conical bearings. The wet brake discs are contained in a sealed housing and operate as a parking brake (negative) and/or dynamic brake (positive).
The braking capacities in terms of torque and power have been upgraded. The dynamic brakes are flushed and activated by a dual control that secures the braking system efficiently and economically.
The dynamic and parking brakes share the same interfaces and enable mounting on a four wheel drive machine using the same attachments on the chassis and the wheel rim.
The MHP’s parking and dynamic brake replace the Dyna+ solution, with higher braking torques and lower weight (from 10 to 20 kilograms less depending on the motor size).
They are completely interchangeable with Dyna+ for the rim and chassis mount as well as for the control pressure.
Poclain Hydraulics puts a high emphasis on testing its new motors and runs a fleet of vehicles to validate the performance levels and the functionalities of its products. The MHP was no exception and was tested on a self-propelled sprayer chassis with the following configuration:
At the front: MHP11, twin displacement, boosted brake and S17 dynamic braking with dual control
At the rear: MHP20, three displacements with an 8/5/2 ratio and a P27 parking brake
PW96 tandem pump
VB220 braking power unit
The vehicle weighs 12 metric tons and can reach 60 km (37 miles) per hour in travel mode and go up grades above 30%.
It uses all the operator assistance functions, such as smooth and automatic speed shift, EcoDrive and electronic traction control.
Several customers, as well as our sales team, have witnessed the sprayer operate on our Verberie test track.
Our latest tests focused on measuring the performance of the brakes when hot, in compliance with the new EU2015/68 regulation. The goal of the test is to measure the drop in braking efficiency when they are used intensively. The brakes are monitored in a « type 0 » test setting (very severe deceleration from max. speed to 0 speeed) at the beginning and at the end of the test, then with a series of twenty « type 1 » brake actuations (at intermediate speeds).
The tests were successful and confirmed the braking capabilities of the wet disc technology used in the MHP motor design.
Source: Poclain Hydraulics, Ltd.