WO1982000270A1

WO1982000270A1 - Power unit with drive motor and a flywheel

Info

Publication number: WO1982000270A1
Application number: PCT/EP1981/000059
Authority: WO
Inventors: Getriebe Kg Voith
Original assignee: Elsner E
Priority date: 1980-07-10
Filing date: 1981-05-29
Publication date: 1982-02-04
Also published as: DE3026219A1; EP0043909A1; US4471668A; EP0056032B1; EP0056032A1; DE3174168D1; JPS57501072A

Abstract

A power unit for a vehicle, particularly for a public transport omnibus, comprises a continuously variable mechanism (G) and four clutches (31, 32, 33, 34). The clutch (31) connects a drive motor (M) to a flywheel (S). The clutch (32) connects the flywheel (S) to an intermediary mechanism (Z). The clutch (33) connects the drive motor (M) to the output shaft (30) and the clutch (34) connects the intermediary mechanism (Z) to the output shaft (30). In order to use a mechanism (G) as simple as possible, a differential is added thereto; such differential has three gear clusters (21, 22, 23) and is preferably conformed as a planetary axle. The continuously variable mechanism (G) is comprised of two units (G<u1>u and G<u2>u), preferably hydrostatic units. The inner toothed wheel (23) is connected to the drive motor (M), the solar wheel (21) is connected with the hydrostatic unit (G<u1>u) and the planetary support (22) is connected with the intermediary mechanism (Z) and at the same time with the other hydrostatic unit (G<u2>u).

Description

Drive unit with a drive machine and a flywheel

Technical field

The invention relates to a drive unit, in particular for vehicles, with a drive machine (M), a flywheel (S) and. a continuously variable transmission (G), which has a first transmission connection (11) and a second transmission connection (12), also with a drive shaft (30) and with an intermediate transmission member (Z), and with four clutches, which are arranged as follows: a) a clutch (31) between the engine (M) and the flywheel (S), b) a clutch (32) between the flywheel (S) and the intermediate gear member (Z), c) a clutch (33) between the engine (M) and the output shaft (30), d) a clutch (34) between the intermediate gear member (Z) and the output shaft (30). State of the art

Such a drive unit is known from DE-OS 27 10532 (= US-PS 4,126,200), to which Fig. 1 is referred below. The drive machine there is designated 10, the flywheel 17, the continuously variable transmission 15 and the output shaft 31. An intermediate gear member is formed there by the gears 35, 40 and 39. The variable transmission 15 is coupled on the one hand to the drive machine 10 and on the other hand to the intermediate transmission member 35, 40, 39. The above-mentioned four clutches are formed in Fig. 1 of DE-OS by the following gear parts: 37 and 42; 42 and 39; 33 and 44; 35 and 44. Among others, the following operating states are possible:

1) Only in a start-up operating area (the clutches 37/42 and 35/44 are engaged) is the sum of the power from the engine and the flywheel transmitted through the continuously variable transmission.

2) In a subsequent operating area (clutches 39/42 and 33/44 engaged), only the power output by the flywheel is guided via the continuously variable transmission; the power of the prime mover, on the other hand, is transferred directly to the output shaft, almost without loss.

According to page 29 paragraph 2 of the DE-OS, different types of continuously variable transmissions can be used. However, a power-sharing hydrostatic transmission is preferred, described in the magazine "Ölhydraulik und Pneumatik" 1971, pages 385 to 391. Such power-branching transmissions have the advantage over the other continuously variable transmissions that part of the performance is transmitted purely mechanically in order to improve the efficiency . This means that the hydraulic power share of the continuously variable transmission is, apart from the immediate starting condition, relatively low. However, because of the rotating housing, these power-dividing hydrostatic transmissions are relatively expensive. The large overall length is also often a problem. Another disadvantage is as follows: Due to the mechanical coupling of the two hydrostatic units via the common, rotating housing, it is not possible for each of the two units to operate at maximum speed or on its own. optimize minimum specific volume.

In the known drive unit, it is provided that the switchover between the starting operating range and the other subsequent operating range takes place when the hydrostatic transmission has reached a speed ratio above 1. As a result, the range in which the hydraulic power share of the power-dividing hydrostatic transmission is relatively low can be increased still further. At the same time, according to page 33 of DE-OS, the speed ratios of the essential drive parts can be adapted to the transmission ratio of the hydrostatic transmission at the switchover point by appropriate dimensioning of the gear wheels 33, 35, 37 to 40 such that a switchover from the start-up operating area to the subsequent operating area ( or vice versa) without relative speeds on the clutches. A disadvantage, however, is that this requires a relatively large number of gear drives (usually 3 or 4). In addition, it is not easily possible to change the course of the power distribution. As already mentioned, this course depends on the transmission ratio of the hydrostatic transmission at the changeover point. In order to make the best possible use of the hydrostatic transmission, the aforementioned transmission ratio is approximately equal to the maximum transmission ratio. A change in the course of the power distribution therefore usually requires a change in the maximum delivery volume in the hydrostatic transmission. At the same time, a change in the gear ratios of the gear transmissions is required. Task and solution according to the invention.

The invention has for its object to improve the drive unit specified at the outset so that the simplest possible continuously variable transmission can be used; at the same time, the course of the power distribution should be changeable with the least possible effort.

This object is achieved by the drive unit specified in claim 1. Two different designs are possible, the characteristics of which are given in claims 2 and 4.

The invention enables the following advantages to be combined:

a) The power split in the continuously variable transmission can be dispensed with; i.e. simple, infinitely variable transmission elements can be used, which can be attached individually in the case of hydrostatic units. Infinitely variable transmission elements of this type are available in the trade without difficulty, even for higher outputs.

b) The entire transmission can be made very compact, because apart from the differential gear only a few gears are usually required.

c) The course of the power distribution can be chosen so that the area with a small power share in the continuously variable transmission is relatively large.

d) Switching from the start-up operating range to the subsequent operating range (or back) can take place at the same speed in the clutches. In almost all embodiments of the invention, the continuously variable transmission can be broken down into two individual machines, both of which can be operated up to their maximum permissible speed. Their size can therefore be kept very small. The arrangement of the two units of the continuously variable transmission is largely arbitrary. They can be arranged side by side, for example, which results in a short overall length for the entire drive unit. Under certain circumstances, the units can be flanged to a gear housing from the outside. This makes them easy to replace in the event of a repair.

If it is desired to change the course of the power distribution, all that is required is a change in the ratio of the differential gear. It is a particular advantage of the invention that the continuously variable transmission does not need to be changed.

As with the known drive unit (DE-OS 27 10 532), various known transmission types can be used for the continuously variable transmission. Now, however, the additionally provided differential gear ensures that a power split takes place in all gear types and the efficiency is increased as a result.

By slightly modifying the gear arrangement, different characteristic curves can be achieved. It can be achieved by the embodiment according to claim 2 or 3 that the characteristic curve for the power portion of the continuously variable transmission in the start-up operating area drops like a hyperbola and increases linearly in the subsequent operating area. On the other hand, can be achieved by the embodiment according to claim 4 that the aforementioned characteristic curve decreases linearly in the start-up operating area and then increases hyperbolic. This version will generally be preferred because the range of low power in the continuously variable transmission is larger.

With the features specified in claim 5 it is achieved that in the differential gear, the gear member rotating at the highest speed is the sun gear, that is the gear member which most tolerates the highest speed.

An important further idea of the invention is given in claim 6. This measure ensures that neither of the two gear units is reversible in the continuously variable transmission, i.e. must be designed for both directions of rotation. This will e.g. the use of a mechanical continuously variable transmission possible without losing the advantages described above. Here you may have to accept that when switching between the start-up and the following operating range, the speed of the drive machine is changed from the transmission. This disadvantage could, if it appears necessary, be eliminated by arranging - as is known per se - a matching gear between the output shaft on the one hand and the intermediate gear member and / or the drive machine on the other hand.

Embodiments of the invention are described below with reference to the drawing. It shows:

Figure 1 shows a drive unit in a schematic representation. Fig. 2 shows a modification of the drive unit of Fig. 1; Fig. 3 shows a modification of the drive unit of Fig. 2; 4 shows a diagram with a characteristic curve of the drive unit according to FIG. 3; Fig. 5 shows another embodiment of the invention. In Figures 1, 2 and 3, the following parts are identified as follows:

Drive machine, designed as an internal combustion engine with a motor shaft 10;

Flywheel with a reduction bevel gear, which has a pinion 18 coupled to the flywheel and a ring gear 19;

Infinitely variable transmission, comprising two individually in the

Drive unit arranged hydrostatic units G ₁ and G ₂ , both of which can alternately work as a pump and as a motor, each have a shaft 11 or 12 as a transmission connection and are connected by means of hydraulic lines 13;

Differential gear with sun gear 21, planet carrier 22 and ring gear 23;

Intermediate gear member, which is designed as a rotatable drum and coupled to the planet carrier 22;

Drive shaft; Clutch between the motor shaft 10 and the ring gear 19, which belongs to the reduction gear of the flywheel S;

Clutch between the ring gear 19 (flywheel S) and the intermediate gear member Z;

Clutch between the motor shaft 10 and the drive shaft 30;

Clutch between intermediate gear member Z and output shaft 30. As is generally known, every clutch can be replaced by a unit comprising a planetary gear set and a brake to stop the ring gear if required.

In Fig. 1, the motor shaft 10 is connected to the hydrostatic unit G ₂ via a gear pair 40/41. In addition, the sun gear 21 of the differential gear D rests on the motor shaft 10; the ring gear 23, on the other hand, meshes on its outside with a gear 42 which rests on the shaft 11 of the hydrostatic unit G ₁ .

2, the motor shaft 10 is also connected to the hydrostatic unit G ₂ on the one hand via a gear pair 40/41, but on the other hand is now connected to the ring gear 23. The hydrostatic unit G ₁ is here connected to the sun gear via a gear pair 43/44 21 connected.

The latter also applies to FIG. 3. Here, however, the hydrostatic unit G _{2 is} connected to the planet carrier 22 and thus also to the intermediate gear member Z via a gear pair 45/46. The ring gear 23 is coupled to the motor shaft 10 again.

In Figure 1, the gear parts 19, 31, 32, 21, 22, 23, Z, 33 and 34 are shown in longitudinal section, in each case only the half located above the shaft 10 and 30, while the lower half of these gear parts (the better Because of overview) is omitted. A similar representation was also chosen in FIGS. 2, 3 and 5.

The effect of the three embodiments according to Figures 1, 2 and 3 is very similar. It is explained below with reference to FIGS. 3 and 4.

The so-called power distribution Nh / N _D is plotted in FIG

(which is the ratio of the hydraulic power N _h to the total by the differential D transmitted power N _D) over the total gear ratio i (that is the ratio n ₃₀ / n ₁₉ of the speeds of the output shaft 30 and the ring gear 19). In the start-up operating range, the clutches 31 and 34 are closed and the clutches 32 and 33 are open. As a result, engine and flywheel power are added at point 50 and fed to ring gear 23 of differential gear D. From here, the power is transmitted partly via the gear parts 22, 46, 45, 12, G ₂ , G ₁ , 43, 44, 21, 22 and 34 and partly from the planet carrier 22 via the clutch 34 directly to the output shaft 30. The power distribution N _h / N _D at the starting point is 1; here the ratio of the hydrostatic transmission is zero. The distribution of benefits then quickly falls linearly. With the value N _h / N _D = 0, the direction of rotation of one of the hydrostatic units is reversed; here the ratio in the hydrostatic transmission is 1. From here the power distribution continues to drop until the ratio i = 1. Here the speed is the same in the clutches 32 and 33. These can now be engaged without synchronization work, with the clutches 31 and 34 being released at the same time. As a result, the engine power is transmitted directly to the output shaft 20 via the clutch 33. The flywheel power passes through the clutch 32 into the intermediate gear member Z. From here it is partly via the gear parts 46, 45, 12, G, 43, 44, D and 33 and partly directly via the differential D and the clutch 33 to the output shaft 30 transfer. The power distribution N _h / N _{D of} the flywheel power increases, as can be seen in FIG. 4, hyperbolically.

At what value N _h / N _D the switching point is, can by

Ratio of the diameter of sun gear 21 and ring gear 23 can be determined. In the arrangements according to Fig. 1 and 2 result in the start-up operating area, deviating from Fig. 4, steeply falling hyber-shaped characteristics and above i = 1 linearly increasing characteristics. The switchover point - due to the different connections of the differential gear D with the other gear parts - is at negative values of N _h / N _D , which in the case of

Fig. 1 is larger and smaller than 1/2 in the case of Fig. 2.

In FIG. 4, the dimension arrow B denotes the range of low hydraulic power, which can be defined, for example, as the range in which the absolute amount of N _h / N _{D is} less than 1/3. As already mentioned, the larger the area B, the higher the average efficiency of the drive unit.

1 to 3, other operating states can also be brought about: If only the clutch 32 is closed, drive energy can be transmitted from the drive machine M via the gears D and G to the flywheel S (or vice versa). However, the flywheel S is preferably increased in speed when the vehicle brakes, that is to say from the output shaft 30 via the transmissions G and D. Here, the clutch clutches are actuated in the same manner as described above in connection with FIGS. 3 and 4. By closing alone The clutch 34 can flow power from the engine M alone via the gear D and G to the output shaft (uphill). Finally, by only closing the clutch 33, power can be transmitted from the drive machine M directly to the output shaft (overland travel).

The exemplary embodiment shown in FIG. 5 differs from the ones described above in that three clutches are replaced by switching units 31 ', 32', 34 '; these each include a planetary gear and a brake that can stop the ring gear. The flywheel S 'is fastened here on a hollow shaft which ver with the sun gears of the two switching units 31' and 32 ' is bound. The arrangement of the differential gear D and the linking of its gear members 21, 22, 23 is the same as that of FIG. 3, as is the arrangement of the hydrostatic units G ₁ and G ₂ . The function of the clutch 33 or the switching unit 34 'is also unchanged. Only their position has been changed compared to FIG. 3. The ratios of the planetary gears of the switching units 31 ', 32', 34 'can be selected so that neither of the two hydrostatic units has to be carried out reversibly (ie with reversible direction of rotation) and that switching can nevertheless take place at synchronous speeds.

5, a simple clutch 34 could be left instead of the switching unit 34 '. This would cause a change in engine speed when switching from transmission; however, this could usually be accepted without difficulty.

Preferred applications:

The drive unit according to the invention can be used above all in vehicles, preferably in buses for city traffic. Such vehicles very often have to be braked, and the braking energy can be stored in the flywheel and then used again.

Claims

Drive unit, in particular for vehicles, with a drive machine (M), a flywheel (S) and a continuously variable transmission (G) which has a first transmission connection (11) and a second transmission connection (12), furthermore with a drive shaft (30) and with an intermediate gear member (Z) and with four clutches, which are arranged as follows: a) a clutch (31) between the engine (M) and the flywheel (S), b) a clutch (32) between the flywheel ( 3) and the intermediate gear member (Z), c) a clutch (33) between the drive machine (M) and the output shaft (30), d) a clutch (34) between the intermediate gear member (Z) and the output shaft (30),

characterized in that the continuously variable transmission (G) is assigned a differential transmission (D) with at least three transmission members (21, 22, 23) which are arranged as follows: e) a transmission member (21 or 23) is connected to the drive machine ( M), f) a gear member (23 or 21) is connected to the first gear connection (11) of the continuously variable transmission (G) and g) a gear member (22) connected to the intermediate gear member (Z).

2. Drive unit according to claim 1, characterized in that the second transmission connection (12) of the continuously variable transmission (G) is connected to the drive machine (M) (Fig. 1 or 2).

3. Drive unit according to claim 2, wherein the differential gear (D) is designed as a planetary gear set with sun gear (21), planet carrier 22) and ring gear (23), characterized in that the sun gear (21) with the drive machine (M), the Planet carriers (22) with the intermediate gear member (Z) and the ring gear (23) with the first gear connection (11) of the continuously variable transmission (G) are connected (Fig. 1).

4. Drive unit according to claim 1, characterized in that the second transmission connection (12) of the continuously variable transmission (G) is connected to the intermediate gear member (Z) (Fig. 3).

5. Drive unit according to claim 2 or 4, wherein the differential gear (D) is designed as a planetary gear set with a sun gear (21), planet carrier (22) and ring gear (23), characterized in that the ring gear (23) with the drive machine (M ), the planet carrier (22) with the intermediate gear member (Z) and the sun gear (21) with one (11) of the two transmission connections of the continuously variable transmission (G) are connected (Fig. 2 or 3).

6. Drive unit according to one of claims 1 to 5, wherein between the flywheel (S) and the engine (M) on the one hand and between the flywheel (S) and the intermediate gear member (Z) on the other hand different ratios (planetary gear sets 31 '32') are provided , characterized in that the gear ratios are selected so that the first transmission connection (11) of the continuously variable transmission (G) has the same direction of rotation in all operating states.