DESC:HYDROSTATIC DRIVE SYSTEM FOR VIBRATORY ROLLER
Field of the invention:
The present invention relates to a construction vehicle, more particularly relates to a hydrostatic drive system of a construction vehicle, preferably a vibratory roller.
Background of the invention:
Vibratory roller also known as vibratory compactor is a construction equipment vehicle designed for soil compaction. The vehicle increases the load bearing capacity of cohesive and granular soils. Primary requirement for the vehicle are highest unit volume compaction with lowest fuel consumption and lesser operating expenses spent by end users.
In typical vibratory rollers, hydrostatic drive system is used for vehicle propulsion. This system comprises of one higher size variable displacement hydraulic pump (e.g. 100 cc per revolution (cc/rev) pump) and two hydraulic motors connected in parallel. Between the two motors, one is a dual displacement motor at rear axle drive and the other is a single displacement motor at front drum drive to achieve two different vehicle speeds such as Travel and Work modes. In figure 1 a conventional hydrostatic drive system is shown. In the drive system a pump (1) is used to deliver the flow to drive a second motor (3) and a first motor (2). The pump (1) is a closed loop variable displacement pump, the first motor (2) is a dual displacement type rear axle motor and the second motor (3) is a single displacement type front drum motor. The front drum motor (3) is directly coupled with drum to drive the drum. Rear axle motor (2) is coupled with axle to drive the tire. The rear axle motor (2) is dual displacement type but front drum motor (3) is single displacement type. For travel application, rear axle motor (2) is used at minimum displacement setting by actuating the electrical actuator valve (4) and front drum motor (3) is used at maximum displacement only. So, a higher flow is required to achieve the maximum travel speed, accordingly for higher flow, higher pump size is required.
Thus the conventional hydraulic drive systems used in vibratory roller consists of higher size pump for propulsion system which is higher in cost. Also, they support only two speeds for propulsion out of which, work mode requires operator’s intervention in reducing the vehicle speed, during climbing up the gradient, for the given engine power.
Accordingly, there exists a need to provide a hydraulic drive system that overcomes the above mentioned drawbacks of the prior arts.
Object of the invention:
An object of the present invention is to provide a hydraulic drive system for vibratory roller having hydraulic pump with reduced size and reduced quantity of hydraulic oil.
Another object of the present invention is a hydraulic drive system for vibratory roller to provide additional speed mode and eliminate operator’s effort in vibratory rollers, during climbing up the gradient.
Summary of the invention:
Accordingly, the present invention provides a hydrostatic drive system for a construction vehicle, preferably a vibratory roller to provide maximum speed for travel application with lesser flow requirements of driving fluid. The hydrostatic drive system comprises of a variable displacement pump for delivering driving fluid in closed loop, a first and second motor receiving driving fluid from the variable displacement pump and operatively coupled to a rear axle and a front drum of the construction vehicle. In a specific embodiment, the first and second motors are dual displacement motors activated by electrical actuator valves for setting displacements thereof to any one selected from a maximum displacement and minimum displacement, to provide additional vehicle speed modes. The system provides three modes of speeds such as a travel mode, a work mode and a gradient mode depending upon the combination of displacement modes of two motors. The Gradient mode is selected through a switch by an operator. The vehicle at this mode is capable of climbing the higher gradient of greater than 40% without operator’s intervention in reducing the vehicle travel speed, with the given engine power, as the pump size is reduced to 60 cc/rev pump
Brief description of the drawings:
The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein
Figure 1 shows a schematic of conventional hydrostatic drive system for propulsion in accordance with the prior art, and
Figure 2 shows a schematic of hydrostatic drive system for vibratory roller in accordance with the present invention, and
Figure 3 shows a schematic of vibratory roller in accordance with the present invention.
Detailed description of the embodiments:
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
The present invention provides a hydraulic drive system to propel a vibratory roller vehicle that provides a hydraulic pump with reduced size and additional speeds. The invention facilitates optimum sizing of the hydraulic pump in a hydrostatic drive system of vibratory rollers and other construction equipment which have requirement of additional vehicle speeds of operation. These are achieved by adapting a dual displacement motor at front drum drive apart from the dual displacement motor at rear axle drive. Additional vehicle speeds are generated by setting different combinations of displacements of two motors using an electrical actuator valve. Apart from regular Travel and Work modes of the vehicle, a new feature of lowest speed is introduced as a Gradient mode, which is selected through a switch by the operator. At this mode, vehicle can climb the higher gradient of >40% for the given engine power, as the pump size is reduced.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description. Table 1 below enlists all the reference numerals along with respective component names:
Table 1
Ref No Component
11 Variable displacement Pump
12 First motor (rear axle motor)
13 Second motor (front drum motor)
14 First control valve
15 Second control valve
50 Hydrostatic drive system
60 Drum
70 Rear wheels
100 Vibratory roller
Referring to the figure from 2 and 3, a hydrostatic drive system (50) (herein after referred to as “the system (50)”), for a vibratory roller (100) is shown in accordance with the present invention. The system (50) comprises a pump (11), a first motor (12), a second motor (13), a first valve (14) and a second valve (15).
The pump (11) is a closed loop variable displacement pump that delivers a flow to drive the first motor (12) and the second motor (13). In an embodiment, the variable displacement pump (11) is a smaller size pump, preferably 60 cc/rev pump
The first motor (12) and the second motor (13) are dual displacement motors. The first motor (12) is a rear axle motor coupled with axle of rear wheels (70) of the vibratory roller (100) to drive the wheels. The second motor (13) is a front drum motor that is directly coupled with a drum (60) to drive thereof. The first motor (12) and the second motor (13) can be set at any one mode of displacement selected from a maximum displacement mode and a minimum displacement mode. Displacement mode of the first motor (12) is selected using the first valve (14) and displacement of the second motor (13) is selected using the second valve (15). In the embodiment, the first and the second valves (14, 15) are electrical actuator valves.
The system (50) generates four different modes of speeds by setting different combination of displacement modes of the first and second motors (12, 13). Out of four speeds, vehicle is generally operated in three modes such as a travel mode, a work mode and a gradient mode.
The travel mode is achieved by setting the first motor (12) at minimum displacement mode and the second motor (13) at minimum displacement mode so as to achieve a maximum speed. This facilitates a maximum speed for travel application and makes a lesser flow requirement, hence a smaller pump size.
The work mode is achieved by setting the first motor (12) at minimum displacement mode and the second motor (13) at maximum displacement mode.
The Gradient mode is achieved by setting the first motor (12) and the second motor (13) at maximum displacement mode. The vehicle at this mode is capable of climbing the higher gradient of greater than 40% and operator’s intervention is not required in reducing the vehicle travel speed, with the given engine power, as the pump size is reduced.
The fourth mode is achieved by setting the first motor (12) at maximum displacement mode and the second motor (13) at minimum displacement mode.
Advantages of the invention:
1. The hydraulic drive system (50) differs from the conventional systems by adapting a dual displacement motor at front drum drive to achieve the maximum vehicle speed, thus resulting in 40% reduction of hydraulic pump displacement size.
2. The reduction in hydraulic pump displacement size helps in significant cost savings of the pump which in turn reduces overall system cost.
3. Vehicle can climb the higher gradient of greater than 40% for the given engine power, by using the smaller pump size & operating in the gradient mode.
4. Operator’s effort in continuously reducing the vehicle travel speed to climb up the gradient is eliminated, as the gradient mode helps the vehicle to climb the gradient at a given constant vehicle speed without operator intervention
5. The reduced pump size helps in reducing hydraulic oil quantity in the system, thereby reducing carbon foot print.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the scope of the claims of the present invention.
,CLAIMS:CLAIMS
We Claim:
1. A hydrostatic drive system (50) for a vibratory roller (100) to provide maximum speed for travel application with lesser flow requirements of driving fluid, the hydrostatic drive system (50) comprising:
a variable displacement pump (11) delivering driving fluid in closed loop;
a first motor (12) receiving driving fluid from the variable displacement pump (11) and operatively coupled to rear wheels (70) of the vibratory roller (100);
a second motor (13) receiving driving fluid from the variable displacement pump (11) and operatively coupled to a drum (60) of the vibratory roller (100);
characterized in that, the first motor (12) and the second motor (13) are a dual displacement motors respectively activated using a first control valve (14) and a second control valve (15) for setting a displacement mode of each motor to any one selected from: a minimum displacement mode and a maximum displacement mode, to achieve any one speed mode selected from a travel mode, a work mode and a gradient mode.
2. The hydrostatic drive system (50) as claimed in claim 1, wherein the variable displacement pump (11) is a smaller size pump, preferably 60 cc/rev pump.
3. The hydrostatic drive system (50) as claimed in claim 1, wherein the first control valve (14) and the second control valve (15) are electrical actuator valves.
4. The hydrostatic drive system (50) as claimed in claim 1, wherein the travel mode is achieved by setting the first motor (12) at minimum displacement mode and the second motor (13) at minimum displacement mode.
5. The hydrostatic drive system (50) as claimed in claim 1, wherein the work mode is achieved by setting the first motor (12) at minimum displacement mode and the second motor (13) at maximum displacement mode.
6. The hydrostatic drive system (50) as claimed in claim 1, wherein the gradient mode is achieved by setting the first motor (12) and the second motor (13) at maximum displacement mode.
Dated this 4th day of September, 2018

Prafulla Wange
(Agent for Applicant)
IN/PA-2058