GB1593750A

GB1593750A - Power coupling transmission

Info

Publication number: GB1593750A
Application number: GB5061577A
Authority: GB
Original assignee: Thyssen Industrie AG
Current assignee: ThyssenKrupp Technologies AG
Priority date: 1976-12-04
Filing date: 1977-12-05
Publication date: 1981-07-22
Also published as: IT1091941B; JPS5395462A; FR2373000A1; DE2655011B1; DE2655011C2

Description

(54) POWER COUPLING TRANSMISSION (71) We, THYSSEN INDUSTRIE AG, a German Company of Am Thyssenhaus 1, 4300 Essen, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a power coupling transmission for the stepless variation of the ratio between a prime mover and a working machine. It has particular application to the use of such a transmission as a vehicle transmission, that is to say a working machine having a constant power characteristic, but it is applicable also to working machines having other characteristics.

Coupling transmissions are known which consist of a three-shaft epicyclic gear unit and a hydrostatic transmission device that serves as an adjustable transmission means (although other transmission devices having similar properties can be used alternatively as the adjustable transmission means). By the term "three shaft epicyclic gear unit" is meant a transmission gear that comprises input and output shafts that can be designated non-free shafts as they are respectively connected to the power input and the working machine, and an intermediate third shaft that can be designated a free shaft, toothed gears fixed to the three shafts transmitting the drive from the input shaft through the gearing of the free shaft to the output shaft.

The free third shaft is connected td one of two displacement units of the hydrostatic transmission device. The other displacement unit of the hydrostatic transmission device is connected to the driven shaft when power is split on the output side, and to the driving shaft when power is split on the input side.

In these coupling transmissions there is a hydrostatic power flow and a mechanical power flow. In arrangements where the hydrostatic power flow is smaller than the power which is to be transmitted by the driving and driven parts of the coupling transmission, higher efficiency is achieved for the coupling transmission in comparison with the hydrostatic transmission device, and smaller maximum displacement volumes are also achieved for the hydrostatic transmission device associated with the coupling transmission.

When the power is split on the input side, undesirable idle power circulates in the coupling transmission at low drive revolutions or low speeds of travel, and the same occurs at high drive revolutions or high speeds of travel when the power is split on the output side.

By changing over from output side to input side power splitting and vice versa, as described for example in German Offenlegungsschriften Nos. 21 41 098 and 25 41 975 power in circuit can be avoided. Efficiency is improved. A small total of maximum displacement volumes to be installed is obtained. The overall size of the coupling transmission is also generally reduced as a consequence.

Efficiency and the total of maximum displacement volumes or overall size become increasingly favourable as the stepless variation range decreases. It therefore becomes conceivable for the necessary variation range to be divided into two or more individual stepless variation ranges and for two-fold or threefold utilisation of the hydrostatic transmission to be achieved.

According to United States Patent Specification No. 3 869 939 two stepless variation ranges are provided by installing two serially connected three-shaft epicyclic gear units. At low speeds of travel output side branching occurs, and at higher speeds, that is to say starting from a transmission ratio of 1:1, driving side branching occurs. In the adjustment range for high speeds of travel a stepup ratio is obtained. In each of the adjustment rangesthat is to say at relatively high speeds of travel in the range obtained with power splitting on the output side and at relatively low speeds of travel in the range obtained with power splitting on the driving side and thus all in all at medium speeds of travel, there is undesirable power in circuit.

The second stepless variation range is obtained by the circuitous expedient of step-up ratios and in many cases must be disadvanta geous.

German Offenlegungsschrift No. 15 30 590 shows the adjustment range of the coupling transmission divided into three individual stepless ranges. For this purpose an additional three-shaft epicyclic gear unit is disposed downstream of the actual coupling transmission with output side power splitting. This epicyclic gear unit disposed on the output side can receive three different ratios by corresponding changeover operations. However, considerable idle power circulates in the epicyclic gear unit on the output side. For the example given in German Offenlegungsschrift No. 15 30 590 the power in circuit amounts in third gear, for example, that is to say with their illustrated clutch K, engaged, to ten times the driving power. A transmission of this kind therefore cannot be utilised.

The present invention is based on the problem of dividing the entire adjustment range of the coupling transmission into two or more individual adjustment ranges by serially connecting two or more three-shaft epicyclic gear units, and thus achieving twofold or threefold utilisation of the hydrostatic transmission, while however a transmission range with step-up ratios, and in addition power in circuit in the three-shaft epicyclic gear units serving as pure transmission stages or countershafts should be avoided.

In accordance with the present invention, there is provided a steplessly adjustable power coupling transmission having at least two threc-shaft epicyclic gear units which are disposed between driving and driven shafts and connected by a common intermediate shaft, and each of which has two non-free shafts and a free third shaft (as hereinbefore defined), the coupling transmission further comprising a two-shaft adjustable transmission means for producing a range of adjustment of the transmission ratio, while for the purpose of providing a plurality of adjustment ranges a plurality of clutches are provided. the transmission being operable so that in each adjustment range ofthe coupling transmission the adjustment range of the adjustable transmission means is passed through and the individual rations of the gear units are so adjustable that the actuation of the clutches is effected without interruption of torque when the clutch halves are in synchronism, and wherein each free shaft of each of said epicyclic gear units has two clutches by means of which said free shaft of each epicylic gear unit can be alternatively coupled to one of two non-free gear unit shafts. and in each said adjustment range one or more of the free shafts is coupled to one of the non-frec gear unit shafts. and another of the free shafts is coupled by way of the adjustable transmission means to another non-free shaft.

Preferably said adjustable transmission means comprises hydraulic displacement units acting as a hydrostatic transmission device, comprising coupled pump/motor displacement units, although other adjustable transmission means may be used.

The invention will be described in more detail by way of example with reference to the accompanying schematic drawings which relate to vehicle drive transmissions according to the invention, and in which: Fig. 1 illustrates a steplessly variable coupling transmission according to the invention, incorporating two serially disposed three-shaft epicyclic gear units, Figs. 2 to 5 indicate different operating states of the coupling transmission of Fig. 1, Fig. 6 illustrates another coupling transmission according to the invention, incorporating three three-shaft epicyclic gear units, Figs. 7 to 11 indicate different operating states of the coupling transmission of Fig. 6, Fig. 12 illustrates a further coupling transmission according to the invention, incorporating two three-shaft epicyclic gear units, and Figs. 13 to 19 indicate different operating states of the coupling transmission of Fig. 12.

In Figure 1 can be seen two three-shaft epicyclic gear units of the kind already known from the prior art. In the illustrated form, drive input shaft I and intermediate shaft 11 form the two non-free or loaded shafts of the first unit. and the shaft 3 forms its free shaft. For the second unit, the intermediate shaft 11 and the driven output shaft 2 form the two non-free shafts and the shaft 15 is the third, free shaft. Considering the first unit in more detail, it will be seen that the drive shaft 1 has a first sun wheel 1' fixed to it and a second sun wheel 3' fixed to the free shaft 3 is connected to the first sun wheel through planet wheel pairs 11' on a carrier I la fixed to the intermediate shaft and further planet wheels 11", also mounted on the carrier I la, the gear wheels of each par I l' being fixed to rotate together with one wheel of the pair meshing with the drive shaft sun wheel 1' and the other meshing with a further planet wheel I I" that also meshes with the free shaft sun wheel 3'. The illustrated further planet wheel I I" is shown offset from the meshing gears 3' and 11' for clarity: these further planet wheels simply have the result of reversing the direction of rotation of the free shaft.

The second three-shaft gear unit in Figure I is of similar construction to the first unit.

The intermediate shaft is common to both, being the driven shaft of the first unit and drive shaft of the second unit.

The free shaft 3 of the epicyclic gear unit on the drive side can be connected either by way of the gears 4, 5, clutch 6, displacement units 7, 8 of a hydrostatic transmission device, and gears 9, 10 to the intermediate shaft Il, or by way of the gears 4, 5 clutch 12, gears 13, 14 to the drive shaft 1. The freeshaft 15 of the epicyclic gear unit on the output side is connected either by way of gear 16, intermediate gear 17, gear 18, clutch 19, gear 20, and gear 21 to the driven shaft 2, or else by way of the gears 16, 17, 18, clutch 22, displacement units 7, 8 and gears 9, 10 to the intermediate shaft 11.

In the adjustment range for low speeds of travel the epicyclic gear unit on the drive side, i.e. the unit comprising the shafts, 111 and 3, acts in conjunction with the hydrostatic transmission device as a steplessly variable transmission, and the epicyclic gear unit on the output side i.e. the unit comprising the shafts 11, 2 and 15, acts as output stage with fixed ratio. In the stepless adjustment range for high speeds of travel, the reverse situation exists. The epicyclic gear unit on the drive side becomes the countershaft with a transmission ratio of I or close to 1. The change-over is made at the boundary between the two adjustment ranges.

The control of the coupling transmission can be seen in Figs. 2 to 5. In the representations of the displacement units 7, 8, a vertical arrow represents displacement volume zero, an arrow turned in the clockwise direction from the vertical represents positive displacement volume, and an arrow turned in the counterclockwise direction represents negative displacement volume. The different figures indicate different operating states of the transmission and in each case the clutches engaged are noted.

Figure 2 shows the states of the displacement units 7, 8 and the clutches engaged in starting. At the state shown in Fig. 3, full power can be transmitted, while on reaching the state shown in Fig. 4 the adjustment range for low speeds of travel is at an end.

The changeover to the adjustment range for high speeds of travel is made in the position shown in Fig. 4, and in the state shown in Fig. 5 the end of the adjustment range forhigh speeds of travel has been reached.

Associated with the coupling transmission shown in Fig. 6 are three serially disposed three-shaft epicyclic gear units connected together: three stepless adjustment ranges are obtained in this manner. The individual epicyclic gear units are analogous to those illustrated in Fig. I and further detailed description of them is therefore unnecessary here.

The three-shaft epicyclic gear unit situated on the input side and the following intermediate three-shaft epicyclic gear unit operate analogously to the gear units in the first example and corresponding parts are indicated by the same reference numbers. The third three-speed epicyclic gear unit, situated on the output side, for the purpose of constraint, is coupled by its free shaft 23 through gear 24, intermediate gear 25, gear 26, clutch 27, gear 28, and gear 29 to the driven shaft 2, and acts as countershaft. This third unit can be used for transmission ratio adjustment for the adjustment range at high speeds of travel. For this purpose the clutch 30 is engaged, so that the intermediate threeshaft epicyclic gear unit provided for middle speeds of travel now acts as clutch. On engagement of the clutch 31 and disengagement of the clutch 27, the hydrostatic transmission device is coupled to the three-shaft epicyclic gear unit on the output side.

Figs. 7 to 11 show different operating states of the coupling transmission and the successive figures indicate the progression from the starting state to the operating state at maximum speed of travel. As in Figs. 2 to 5, the adjustment states of the displacement units 7, 8 are indicated, as well as the various clutches engaged in each case. From the starting state in Fig. 7, the middle region of the range for low travel speeds is reached in Fig. 8 and at the end of that range the state is shown in Fig. 9. The middle region of the range for high travel speeds is indicated in Fig. 10 and the end of that range is reached in the state shown in Fig. 11. The displacement volume of the displacement unit 8 undergoes threefold utilisation in this embodiment of the coupling transmission.

Reference has already been made to German Offenlegungsschriften Nos. 21 41 098 and 25 41 975, and the present invention can be applied to the transmissions described there as in the manner that will be described below.

By the use of countershafts the displacement unit 8 can in known manner be switched over from one non-free shaft of a three-shaft epicyclic gear unit to the other non-free shaft without torque and at synchronous speeds of rotation when its displacement volume zero is reached. In this way the circulation of idle power is avoided even in the epicyclic gear units connected to the hydrostatic transmission device. Efficiency is improved and the total maximum displacement volumes to be installed are further reduced.

Furthermore, reversing can be effected in known manner only with the hydrostatic transmission device, for which purpose its displacement unit acting as pump is connected by way of countershafts to the driving shaft of the coupling transmission and its displacement unit acting as motor is connected to the driven shaft of the coupling transmission. In this way the circulation of idle power during reversing is avoided.

Moreover, when maximum ratio is reached, that is to say maximum speed of travel, the high pressure and low pressure sides of the hydrostatic transmission device can be short-circuited, in which case for the purpose of constraint the free shaft of the three-shaft epicyclic gear unit on the output side is then simultaneously coupled by way of countershafts or directly to a non-free shaft of the epicyclic gear unit in question.

Since the hydrostatic transmission device then idles. The efficiency of the coupling transmission is improved under these operating conditions.

Fig. 12 shows an example of a coupling transmission according to the invention with the features described above. Parts corresponding to those already described with reference to the embodiments of Figs. I and 6 are indicated by the same reference numbers. As in those first two examples, the operation of this third embodiment is illustrated in a series of symbolic representations, Fig. 13 showing the state for maximum reverse speed, Fig. 14 showing the stopped state between reverse and forward travel, and Figs. 15 to 19 showing progressive forward travel states up to maximum travel speed (Fig. 19). The necessary changeover operations can be seen from Figs. 13 to 19.

On starting up, that is to say with a high ratio of the coupling transmission, the threeshaft epicyclic gear unit on the output side acts as countershaft stage through the coupling of its free shaft 15 by way of gear 16, intermediate gear 17, gear 18, clutch 19, gear 20 and gear 21 to the driven shaft 2. In the adjustment range for low speeds of travel (Fig. 14) the three-shaft epicyclic gear unit on the input side provides the ratio adjustment of the coupling transmission. For this purpose the free shaft 3 is coupled by way of the gears 4, 5 clutch 6, displacement units 7, 8, clutch 32, and gears 9, 10 to the common shaft II of the two epicyclic gear units in order to achieve constraint. The displacement unit 8 is coupled to the driving shaft 1 by means of the clutch 33 and gears 34, 14 when its displacement volume zero is reached (Fig. 16). When the displacement unit 8 has passed once through its displacement volume range. the shafts I and 3 are turning in the same direction and at the same speed. After actuation of the clutch 35 the three-shaft epicyclic gear unit on the drive side now acts as a coupling. In this operating state the clutches 22. 35. 36 are engaged and the clutches 6, 19 and 33 disengaged (Fig.

17). In this way in this three-shaft epicylic gear unit on the output side the hydrostatic transmission device is located between the free shaft 15 by way of the gears 16. 17, 18 and the driven shaft 2 by way of the gears 21, 37. The adjustment range for high speeds of travel now exists. At displacement volume zero of the displacement unit 8 it is connected to the driving shaft I by means of the gears 34, 14 and clutch 33 after disconnection from the driven shaft 2 (Fig. 18). With unity transmission ratio of the coupling transmission the clutch 30 can be actuated with synchronous speeds of rotation, and by means of control valve 38 the high pressure and low pressure sides of the hydrostatic transmission device can be short-circuited.

The three-shaft epicyclic gear unit on the output side now runs also as a coupling.

For reversal purposes the clutches 31, 32 and 19 are engaged (Fig. 13). Power is then transmitted through the hydrostatic transmission device, the three-shaft epicyclic gear unit on the output side acting as countershaft. From here the stationary state is reached in Fig. 14 whereupon forward drive transmission can be obtained, as already described up to a transmission ratio of 1:1. In the adjustments shown in Figs. 15 to 19 the full power of the engine, that is to say of the prime mover, can be transmitted.

It will be noted that in each of the embodiments described above, by the use of clutches that displacement unit in the hydrostatic transmission that is associated with the free shaft epicyclic gear unit is switched over without torque and with synchronous rotational speeds to the free shaft of another three-shaft epicyclic gear unit when an adjustment range limit is reached, while the free shaft thus liberated is coupled by means of clutches directly, or with the aid of countershaft gears, to one of the non-free shafts of the epicyclic gear unit in question.

WHAT WE CLAIM IS: 1. A steplessly adjustable power coupling transmission having at least two three-shaft epicyclic gear units which are disposed between driving and driven shafts and connected by a common intermediate shaft, and each of which has two non-free shafts and a free third shaft (as hereinbefore defined), the coupling transmission further comprising a two-shaft adjustable transmission means for producing a range of adjustment of the transmission ratio, while for the purpose of providing a plurality of adjustment ranges a plurality of clutches are provided, the transmission being operable so that in each adjustment range of the coupling transmission the adjustment range of the adjustable transmission means is passed through and the individual ratios of the gear units are so adjustable that the actuation of the clutches is effected without interruption of torque when the clutch halves are in synchronism, and wherein each free shaft of each of said epicyclic gear units has two clutches by means of which said free shaft of each epicyclic gear unit can be alternatively coupled to one of two non-free gear unit shafts, and in each said adjustment range one or more of the free shafts is coupled to one of the non-free gear unit shafts, and another of

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Claims

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sides of the hydrostatic transmission device can be short-circuited, in which case for the purpose of constraint the free shaft of the three-shaft epicyclic gear unit on the output side is then simultaneously coupled by way of countershafts or directly to a non-free shaft of the epicyclic gear unit in question.

Since the hydrostatic transmission device then idles. The efficiency of the coupling transmission is improved under these operating conditions.

Fig. 12 shows an example of a coupling transmission according to the invention with the features described above. Parts corresponding to those already described with reference to the embodiments of Figs. I and 6 are indicated by the same reference numbers. As in those first two examples, the operation of this third embodiment is illustrated in a series of symbolic representations, Fig. 13 showing the state for maximum reverse speed, Fig. 14 showing the stopped state between reverse and forward travel, and Figs. 15 to 19 showing progressive forward travel states up to maximum travel speed (Fig. 19). The necessary changeover operations can be seen from Figs. 13 to 19.

On starting up, that is to say with a high ratio of the coupling transmission, the threeshaft epicyclic gear unit on the output side acts as countershaft stage through the coupling of its free shaft 15 by way of gear 16, intermediate gear 17, gear 18, clutch 19, gear 20 and gear 21 to the driven shaft 2. In the adjustment range for low speeds of travel (Fig. 14) the three-shaft epicyclic gear unit on the input side provides the ratio adjustment of the coupling transmission. For this purpose the free shaft 3 is coupled by way of the gears 4, 5 clutch 6, displacement units 7, 8, clutch 32, and gears 9, 10 to the common shaft II of the two epicyclic gear units in order to achieve constraint. The displacement unit 8 is coupled to the driving shaft 1 by means of the clutch 33 and gears 34, 14 when its displacement volume zero is reached (Fig. 16). When the displacement unit 8 has passed once through its displacement volume range. the shafts I and 3 are turning in the same direction and at the same speed. After actuation of the clutch 35 the three-shaft epicyclic gear unit on the drive side now acts as a coupling. In this operating state the clutches 22. 35. 36 are engaged and the clutches 6, 19 and 33 disengaged (Fig.

17). In this way in this three-shaft epicylic gear unit on the output side the hydrostatic transmission device is located between the free shaft 15 by way of the gears 16. 17, 18 and the driven shaft 2 by way of the gears 21, 37. The adjustment range for high speeds of travel now exists. At displacement volume zero of the displacement unit 8 it is connected to the driving shaft I by means of the gears 34, 14 and clutch 33 after disconnection from the driven shaft 2 (Fig. 18). With unity transmission ratio of the coupling transmission the clutch 30 can be actuated with synchronous speeds of rotation, and by means of control valve 38 the high pressure and low pressure sides of the hydrostatic transmission device can be short-circuited.

The three-shaft epicyclic gear unit on the output side now runs also as a coupling.

For reversal purposes the clutches 31, 32 and 19 are engaged (Fig. 13). Power is then transmitted through the hydrostatic transmission device, the three-shaft epicyclic gear unit on the output side acting as countershaft. From here the stationary state is reached in Fig. 14 whereupon forward drive transmission can be obtained, as already described up to a transmission ratio of 1:1. In the adjustments shown in Figs. 15 to 19 the full power of the engine, that is to say of the prime mover, can be transmitted.

It will be noted that in each of the embodiments described above, by the use of clutches that displacement unit in the hydrostatic transmission that is associated with the free shaft epicyclic gear unit is switched over without torque and with synchronous rotational speeds to the free shaft of another three-shaft epicyclic gear unit when an adjustment range limit is reached, while the free shaft thus liberated is coupled by means of clutches directly, or with the aid of countershaft gears, to one of the non-free shafts of the epicyclic gear unit in question.

WHAT WE CLAIM IS: 1. A steplessly adjustable power coupling transmission having at least two three-shaft epicyclic gear units which are disposed between driving and driven shafts and connected by a common intermediate shaft, and each of which has two non-free shafts and a free third shaft (as hereinbefore defined), the coupling transmission further comprising a two-shaft adjustable transmission means for producing a range of adjustment of the transmission ratio, while for the purpose of providing a plurality of adjustment ranges a plurality of clutches are provided, the transmission being operable so that in each adjustment range of the coupling transmission the adjustment range of the adjustable transmission means is passed through and the individual ratios of the gear units are so adjustable that the actuation of the clutches is effected without interruption of torque when the clutch halves are in synchronism, and wherein each free shaft of each of said epicyclic gear units has two clutches by means of which said free shaft of each epicyclic gear unit can be alternatively coupled to one of two non-free gear unit shafts, and in each said adjustment range one or more of the free shafts is coupled to one of the non-free gear unit shafts, and another of

the free shafts is coupled by way of the adjustable transmission means to another non-free shaft.
2. A coupling transmission according to claim 1 wherein said adjustable transmission means comprises hydraulic displacement units acting as a hydrostatic transmission device.
3. A coupling transmission according to claim 2, wherein at least one of the hydraulic displacement units is adjustable to a zero displacement volume, said unit when connected to a non-free shaft of a three-shaft epicyclic gear unit thereupon being able to be switched over in known manner to another non-free shaft of one of the threeshaft epicyclic gear units, utilising countershafts and by way of additional clutches.
4. A coupling transmission according to claim 2 or claim 3, wherein a reverse drive is arranged to be effected with the aid of the hydrostatic transmission device, for which purpose it has one displacement unit arranged to act as a pump and be connected by way of countershafts to the drive shaft, and another displacement unit arranged to act as a motor and be connected to the intermediate shaft or driven shaft.
5. A coupling transmission according to any one of claims 2 to 4, wherein the high pressure and low pressure sides of the hydrostatic transmission device can be shortcircuited, while for the purpose of constraint the free shaft is in each case coupled through countershafts or directly to one of the nonfree shafts of the epicyclic transmissions in each particular case.
6. A steplessly adjustable power coupling transmission constructed and arranged for use and operation substantially as described herein with reference to any of the embodiments illustrated in the accompanying drawings.