POWER TRANSMISSION SYSTEM

Abstract: A power transmission system in a vehicle, where mechanical power transmission is utilized within one range of speed and hydrostatic power transmission within another range of speed and in which vehicle there is a joint engine (1) as a driving power source for both power transmissions. In the hydrostatic power transmission system of a vehicle or a working machine there are at least two hydraulic pumps and at least two hydraulic motors in order to produce two or more ranges of slowest speed and the highest range of speed of the vehicle is effected by coupling the engine to the driving wheels of the vehicle by means of mechanical power transmission.

Description: POWER TRANSMISSION SYSTEM The invention relates to a system for transmission of power from the engine to the wheels in a vehicle or a working machine. Generally known in working machines are hydraulic hub motors, which function directly as a collar bearing and fastening flange of the wheels and also rotate the wheels. By said means it is easy to arrange the drive both for the turning and fixed wheels. Hydraulic power transmission is usually utilized in slow-speed working machines, where hydraulic function is needed for many other purposes. The speed of rotation of the hydraulic motor is adjusted by altering the speed of fluid. The hydraulic motor is not adaptable to a great speed range of wheel rotation without lessening the efficiency. A hydraulic motor shall have a great torsion at small speeds, especially in working machine operation and, as the vehicle should also be transported at greater speeds on roads by the same motor construction, the efficiency does not remain good anymore and is not as good as a mechanical power transmission. In the above case, the solutions in the German publications 1113639 and 1153268 are referred to. Further, in the Swiss patent 494140 also a hydrostatic power transmission is used even at the greatest speed and always with engaged four wheel drive. By means of the system according to this invention a decisive improvment is achieved compared to the above described dis¬ advantages. The invention is characterized in what is presented in the enclosed patent claims. It can be considered the greatest advantage of this invention that by means of methods of coupling the hydraulic pump and the hydraulic motors allow the slow speed and several wheels can be made driving with a rather great torsional moment and by changing the coupling so that there will be a greater speed of fluid for each hydraulic motor, the speed of the driving wheels can be increased and the greatest speed is reached while trans¬ mitting the power mechanically to the driving wheels and by¬ passing the hydraulic system. The mechanical power transmission is simply done with a toothed coupling, whereat the clutch behind the motor can be omitted. Damage in the power transmis¬ sion on coupling can be prevented by a such a construction of the toothed coupling that wrong-timed coupling can be prevent¬ ed. The hydraulic motors placed in the wheels during power transmission, which in this inventional construction are radial piston motors, switch to free rotation, whereat they brake only by means of their bearing friction, while radial piston motors, which are generally used as driving engines, brake much more in their idle state and cause remarkable drop of efficiency. By a power transmission system according to this invention the advantages of a mechanic system can be utilized in full within the greatest range of speed, because both the hydrostatic and mechanic power transmission systems are arranged in one vehicle. In the following the invention is described in detail with reference to the enclosed drawing, where Pig. 1 is a schematic diagram of a power transmission system of a vehicle. Fig. 2 is a schematic diagram of a power transmission system of a vehicle with caterpillar bands. Fig. 3 is a coupling of a mechanical power transmission. Fig. 4 is a method of blocking a coupling. Figure 1 shows a four-wheel working machine, all ^wheels 25 of which can be made driving. Each of the turning wheels of the working machine has its own radial piston type hub motor 7 and 8, the piston of which switches to ffree rotation when no power is transmitted over them. By means of a gear 10 and a differ¬ ential 11 the hydraulic motor 6 is coupled to rotate the wheels at one end of the working machine. Over clutch 5 the gear 10 is connected to the a shaft directed to the differential 11 and therefore both the gear box and the hydraulic motor 6 can be disengaged from the power trans¬ mission. Engine 1 rotates both the hydraulic pump 4 and the mechanic power transmission 3,11 over the through shaft of the pump. By means of valves Ϊ2 and 12' it is possible to arrange different kinds of coupling between hydraulic pump 4 and the hydraulic motors 6, 7 and 8. By means of the system a coupling A of valves 12 and 12' can be made, where all wheels are driving. Pump 4 delivery goes to the hub motors of wheels 7 and 8 and to the engine 6 and further to the wheels over gear 10 and differential 11. With this coupling slow motion is produced for the working machine and a great torsional moment for the wheels. The mechanical coupling is then in off-position. On closing valve 12 the pump delivery goes, controlled by valve 12', to engine 6, the speed of rotation of which increases then considerably. Accordingly, a higher speed range is achieved with the working machine merely by utilizing the wheels which are driving over the differential. The mechanical coupling is thereby also in off-position. The hub motors are in free rotating state, whereby the corresponding wheels are rotating only on their bearings and an efficiency advantage of 5 - 10 % is reached in comparison to both high-speed hub motors and hub motors with planetary gears. When engine 1 is coupled with toothed coupling 3 right over the differential 11 to the driving wheels and the hydraulic pump 4 disengaged as well as the mechanic coupling, the highest range of speed is produced, which is used by road transport. By means of hydraulic motors the speed of a working machine must be brought to a state, where the coupling can take place with coupling 3. For a successful coupling, the speed must be of such a rate that the engine 1 speed of rotation must not be dropped below the range, by means of which the motor may and is recommended to be used. Figure 2 shows a working machine with caterpillar bands 9. The figure illustrates an exemplified coupling, wherein the engine 1 utilizes hydraulic pump 4, the delivery of which goes to the hub motors 7 and 8. Adjusting a different speed of fluid to motors 7 and 8 by choking or even by rotating the hub motors 7 and 8 in different directions, the working machine can be steered by adjusting the rotation of the hub motors separately. The pressure fluid lines " in figure 2 are only shown diagram- atically. An individual adjustment of motors 7 and 8 reguires separate pressure fluid lines. Also in this example the drive can be transmitted to the caterpillar bands even over the differential by means of the hydraulic motor or mechanical power transmission. The existence of a differential is most essential especially on using caterpillar bands, because the drive transmitted over the differential does not disturb the steering by means of hub motors 7 and 8. Figure 3 shows a mechanical coupling of figures 1 and 2, by means of which the power transmission is coupled between shafts 20 and 23. On shaft 20 there is a grooved bushing 19, which produces the coupling by sliding to the left over the teeth of blocking ring 14 onto the teeth 13 of the other shaft 23. On shaft 20 surface there is also straight grooving or indentation 22, which transmits the torsion to bushing 19. Bushing 19 is fitted with simal identation 15. Bushing 19 is slided by a slight force by pushing shafts 24 and roll 18. The motion is returned by a back-spring. The thrust motion can be hydraulic. Upon coupling, shaft 20 rotated faster than shaft 23, because with the hydraulic power sytem the vehicle is accelerated at high rotation speed so that the speed would be increased with a further gear, which is the mechanic coupling. Coupling is started by sliding bushing 19 to the left and reducing the engine rotations. While the bushing is sliding, the coupling blocking ring 14 is also slided to the left by spring 21 or alsy by means of bushing 19. Shafts 20,23 rotate at different speeds and, when the blocking ring with its friction ring presses against the end of shaft 23, the difference of speed of these shafts makes the blocking ring 14 move with respect to bushing 19. The blocking ring 14 moves appr. half a tooth width, as shown in figure 4, to a different position with respect to bushing 19 and tooth 15. Since the difference of speed still remains between the shafts, the tooth of the blocking ring 14 and the tooth 15 of bushing 19 lean with their bevelled surfaces against each other so that the sliding apparatus 18,24 of the bushing cannot press the bushing 19 as far as the coupling. Blocking ring 14 has its tooth 17 in the bushing 19 groove with a rather loose fitting, due to which they can sustain their mutual position of half-tooth-width. As according to figure 4 the engine speed of rotation has dropped jalmost exactly to the speed of shaft 23 or below it, i.e. the teeth 14 and 15. are in the arrow direction as well as the teeth 13 of shaft 23, and the engine speed of rotation is dropping unde_r the speed of shaft 23, the teeth 14 of the blocking ring, pulled by friction ring 16, is slided off front of tooth 15 and tooth 15 can proceed into the gaps of teeth 13 while rotating almost at the same speed as the shaft. Then, when the coupling has switched on, it is possible, for instance, to raise the engine speed of rotation automatically or indicate that coupling has taken place. The blocking ring 14 is not a synchronous ring that synchronizes speeds egually but it prevents coupling when the shafts do not rotate at almost the same speed. Great rotating masses are connected to each shaft and thus wrong-timed coupling may lead to damages. While engaging the mechanic power transmission, the hydraulic pumps are disengaged or switch to free rotation, if they are not needed for some other use. In power transmission effected by the hydraulic system several steps of speed are produced by connecting pumps parallell with one motor or, correspondingly, by dividing the delivery of one pump to several motors. Of course, with more than one pump and one motor, various versions of coupling and steps of speed are possible. Naturally, many variations of mechanical couplings can be adapted as a coupling 3 and, in any case, it is not the intention to restrict the invention to concern the presented embodiments only but many other modifications are possible within the inventional idea determined in the patent claims.

Claims: PATENT CLAIMS A power transmission system in a vehicle or a working machine, where there are two drive shafts and in which mechanical power transmission is used within one speed range and hydrostatic power transmission within another speed range by means of a hydrulic pump and hydraulic motors and in which vehicle the driving power source of both power transmissions is a mutual engine (1), characterized in that the power transmission system is comprised of: - hub motors (7), (8) for the hydraulic driving shaft, one each for both driving wheels of the said shaft, which are driving only within the low-speed range of the vehicle, - mechanical power transmission (10,11) for both wheels in the other driving shaft where power is transmitted both from the vehicle engine (1) and mechanically from a hydraulic motor (6) accomodated in the power transmission system and - a coupling to reach the highest vehicle speed range, where engine (1) is connected by mechanical power transmission (3,11) only to the driving wheels of the last mentioned shaft. 2. A system according to patent claim 1 characterized in that in the coupling of the slower speed range there are more driving wheels engaged than in the higher speed range coupling. 3. A system according to patent claim 1 or 2 characterized in that within the higher speed range of the hydrostatic power transmission the total delivery of several pumps is directed to one hydraulic motor. 4. A system according to any of above patent claims 1 - 3 characterized in that the coupling (3), engaging the higher speed range, is a toothed coupling. 5. A system according to patent claim 4 characterized in that the mechancial coupling (3) is provided with a system to prevent coupling, the effect of which is disengaged as soon as the shafts (20), (23), " which are to be coupled, are rotating substantially at the same speed. 6. A system according to any of the patent claims 1 - 5 characterized in that the mutual rotation speed of at least one pair of wheels, covered by the caterpillar bands of the vehicle or working machine, can be adjusted to be different allowing steering of a vehicle furnished with bands. 7. A system according to any of the patent claims 1 - 6 characterized in that there is power transmission over a differential (11), at least for one pair of wheels, in the vehicle or working machine. 8. A system according to any of the patent claims 1 - 7 characterized in that the speed range of the mechanical power transmission is at least partly covered by the hydrostatic power transmission.

Inventors: RAUNISTO YRJOE, RAUNISTO, YRJOE
Applicants: RAUNISTO AIRI, RAUNISTO, AIRI
Application year: 1992
Main classification: B60K17
IPC codes: B60K17