FR2679975A1 - Hydromechanical transmission for motor vehicles - Google Patents

Abstract

The transmission between a combustion engine M and an output shaft 9 includes two devices. The first device includes a hydrostatic speed varying device with a pump H1 and hydraulic motor H2, combined with an epicyclic gear train T1. The second device, combined with the first, includes two epicyclic gear trains T2 and T3 connected together. The power of the combustion engine M can be transmitted to the gear train T1 of the first device either by a hydraulic route or by both mechanical and hydraulic routes, which, in conjunction with the second device, makes it possible to obtain different transmission ratios which follow on from each other without jerks and extend continuously over a wide speed range with, by virtue of the mechanical route, the best possible efficiency. Application to heavy vehicles or to agricultural tractors having need of a wide range of speeds.

Description

 The present invention relates to a transmission for motor vehicles with a heat engine, particularly for heavy vehicles or agricultural use such as tractors, which require an extended speed range.

 The transmission of the invention is of the type comprising on the one hand a hydrostatic transmission comprising a hydraulic pump mte by the heat engine, and a hydraulic motor connected to the pump by two fluid conduits under pressure, one in the one-way direction. the other in the return direction, and on the other hand a mechanical transmission by gears, in particular epicyclic gears.

 A transmission of this type is known from the French patent filed under No. 83 01332 and published under No. 2,540,058. This patent raises and solves the problem of obtaining, for motor vehicles with caterpillars, a good ability to turn, even at high speed.

Turnability is achieved by two symmetrical hydromechanical transmissions ruled by a single heat engine. Each of these hydromechanical transmissions comprises a pump and a hydraulic motor interconnected by two fluid conduits under pressure, and comprises gears. Each hydraulic motor is connected to a tracked wheel by an epicyclic planetary reducer and a pair of link gears providing a single reduction ratio. The engine, mounted in a plane of symmetry of the transmission is provided with a motor shaft perpendicular to the shafts of each of the mechanical transmissions (the link gears and the planetary gear) and the shaft of the tracked wheels.

The motor shaft transmits its energy on the one hand to each of the hydraulic pumps, on the other hand to the shaft of the tracked wheels through bevel gear bevel gear.

 In the present invention, the problem is to obtain with a hydromechanical transmission of aforementioned type a wide range of output speeds for the wheels, tracked or not, and to benefit from both the continuity and the progressiveness of a hydraulic transmission, and a good performance (ratio of the driving power of the wheels to the power of the engine) provided by a mechanical transmission.

 The problem is also posed to obtain these favorable results by means of a limited number of mechanical members, so as economically as possible.

 These problems which differ from that of patent FR 2540 058 are solved by the present invention which relates to a mechanical transmission of the aforementioned type, as described in the first claim.

This transmission comprises a first device consisting of a hydrostatic variator with two directions of rotation combined with a first epicyclic gear train, and this first device is combined with a second device entirely. mechanical consisting of two epicyclic trains connected to each other and connected to the first device by two intermediate shafts.

 With this relatively simple arrangement, it is possible to obtain four modes of operation over an extended speed range, these four modes comprising a first fully hydrostatic mode in both directions of rotation, at low speed and a fourth entirely mechanical mode, at high speed and high power efficiency, the intermediate modes being hydromechanical.

 The motor shaft and the output shaft to the wheels are either parallel or in axial extension of one another.

 Other features and advantages will become apparent from the following description.

In the appended drawing, given solely by way of example,
FIG. 1 is a diagram of a hydromechanical transmission according to the invention,
FIG. 2 is a diagram similar to FIG. 1 of a transmission variant according to the invention,
FIG. 3 is a diagram illustrating the variations in displacement of the hydraulic pump of the first device during the different operating modes.

 According to the embodiment of FIG. 1, the transmission of the invention comprises two gear shifting devices connected by two coaxial intermediate shafts.

 The input power of the hydromechanical transmission is provided by a heat engine M. On its drive shaft 1 is locked a driving gear 2 which meshes with a gear 3 wedged on a shaft 4, on the other hand part with a gear 6 to transmit the power of the motor M to the first device by two ways at a time, one hydrostatic or hydraulic, the other mechanical.

 The first device is a continuous hydrostatic drive HI - H2 with two directions of rotation thus combined with a gear T1 epicyclic gears or planetary gear T1.

 The hydrostatic variator comprises a rotary pump H1, variable displacement, or pressure generator, for example of the cylinder type, and a hydraulic motor or receiver H2, constant displacement, for example of the same cylinder type as the pump H1. The pump H1 and the motor H2 are connected by two pressurized fluid conduits, a "forward" duct A of the pump H1 to the engine H2, and a "return" duct R of the motor H2 to the pump H1, and their circuit comprises the usual control organs in these known embodiments.

 The displacement of the pump H1 can be varied between a maximum positive value and a maximum negative value, passing through a zero value, by means of known and not shown mechanisms.

 The role of pump H1 can be reversed. Instead of being a generator of fluid pressure to the engine H2 being rotated by the shaft 4, it can be a fluid receiver under pressure and provide energy by working as a motor. Similarly, the role of the H2 engine can be reversed: it can become a pump.

 The hydraulic motor H2 hydraulically connected to the pump H1 comprises an output shaft 5 connected to the train T1.

 The train T1 comprises a pinion or sun gear 11 set in rotation on the output shaft 5, a planet carrier 12 cooperates with the pinion 11 and with the ring gear 13. The planet carrier 12 is immobilizable by means of a brake F1 carried by a housing not shown.

 The first device (H1 - H2 - T1) receives the power of the motor M by the hydraulic way leading to the pump H1 through the shaft 1, the gears 2 and 3 and the shaft 4, and by the mechanical way leading to the T1 train through the gears 2 and 6 and a clutch El interposed between 11 gear 6 and the planet carrier 12.

 In other words, the motor shaft 1 is connected both to the input of the hydrostatic converter (H1 - H2) by the shaft 4 to the pump H1 and to the output of the variator (H1 - H2) by the clutch El, and the train T1 to the shaft 5 and the engine H2. The first device is therefore hydromechanical.

 The first device is connected to the second device by two coaxial intermediate shafts: a central intermediate shaft 7 integral in rotation with the ring gear 13, and a tubular intermediate shaft 8, surrounding the previous one. The tubular intermediate shaft 8 can be connected to the heat engine M by a clutch E2 whose element is rotatably connected to the gear 6, by the gear 2 which meshes with the gear 6, and by the shaft 1. The tubular shaft 8, carried by the central shaft 7, carries a tubular shaft 10 which itself carries the gear 6.

 The second device, connected to the first, is purely mechanical and provides the power output to the vehicle wheels.

The second device comprises two planetary gear trains
T2 and T3 connected to each other and to intermediate shafts 7 and 8.

On the central intermediate shaft 7 are locked in rotation the planet gears 21 and 31 of the trains
T2 and T3. On the tubular intermediate shaft 8 is wedged in rotation the planet carrier 22 of the train T2. The train
T2 also comprises a crown with internal teeth 23 meshing with the satellites of the planet carrier 22. The crown 23 is integral in rotation with the planet carrier 32 of the train T3. The train T3 has an internally toothed crown 33 which meshes with the satellites of the planet carrier 32 and can be immobilized by a brake F2 carried by the housing.

The planet carrier 32 is rotatably connected to an output shaft 9 which transmits the power, therefore the movement to the unrepresented wheels of the vehicle. In this example, the motor shaft 1 and the output shaft 9 are parallel.

The clutches El, E2, F1, F2 are of the friction type, for example.

Given the above, the second device which is epicyclic, has four junctions - the first is the central intermediate shaft 7 and is
permanently connected to the crown 13 which is the
the first device, the second is the tubular intermediate shaft 8 and is
selectively connected by the clutch E2 with the
thermal engine M through the gears 6 and 2, the third is the ring 33 immobilisable by the
brake F2, - the fourth is the planet carrier 32 and is connected
permanently to the output shaft 9.

VARIANT OF FIGURE 2:
According to the embodiment of FIG. 2, the hydromechanical transmission shown is similar to that of FIG. 1, so that the same numerical references have been applied to the corresponding members.

But there are differences in links or junctions.

 10) The hydrostatic variator H1-H2 is arranged such that the drive shaft 1 which drives the pump H1 is in the axial extension of the output shaft 9.

 20) The hydrostatic variator is placed differently, but as in the previous example, there is a permanent mechanical connection between the shaft 5 of the hydraulic motor H2 and the pinion 11 of the train T1, through intermediate gearing gears 14, 15 and 16 the gear 14 is integral in rotation with the same tubular intermediate shaft 10 as the pinion 11; the gear 16 is rotated on the shaft 5; the gear 15 is a transmission intermediate between the gears 16 and 14.

30) The differences in connections between the first device (H1 - H2 - T1) and the second device (T2
T3) and inside the second device are the following
- The ring 13 of the train T1 is integral in rotation with the tubular intermediate shaft 8 which joins the second device carrying the pinions 21 and 31 of the trains T2 and T3. This link is permanent.

 - On the other hand, the connection of the central intermediate shaft 7 with the first device is selective, through the clutches E1 and E2. The clutch E2 allows to couple the shafts 1 (motor) and 7 (intermediate).

 - The planet carrier 32 is integral in rotation with the central intermediate shaft 7.

 - The planet carrier 22 of the train T2 is integral in rotation with the ring gear 33 of the train T3, itself rotatably connected to the output shaft 9.

It is on the ring 23 of the T2 train that the brake F2 is applied.

This variant has the advantage of showing another hydromechanical transmission arrangement between the engine
M and the wheels while enjoying the same principles of operation as that of Figure 1.

FUNCTIONNEMFNT (figure 3 and switching table)
It is common with two previous examples.

 The cooperation of the two devices (H1, H2, T1) and (T2, T3) provides four modes of operation illustrated by the diagram of Figure 3, in which the x-axis represents the speeds of the spindle. output 9 and the y-axis "y" represents the displacements of the pump H1. They are also illustrated by the table below of commutations and the boxes marked with an asterisk "*" indicate the active organs, that is to say, contributing to the transmission of movement, whereas the empty boxes indicate that the corresponding organs are at rest and do not transmit any couple.

TABLE OF CONKUTATIONS

<tb><SEP> El <SEP> E2 <SEP> F1 <SEP> F2 <SEP> H1 <SEP> H2 <SEP> T1 <SEP> l2 | T3 <SEP><SEP> T3 <SEP>
<tb><SEP> PLI <SEP>
<tb> * <SEP>
<tb> 1 <SEP> er <SEP> MODE <SEP> * <SEP> * <SEP> pump <SEP> engine <SEP> *
<tb> AV <SEP> and <SEP> AR
<tb> 2 <SEP> th <SEP> MODE <SEP> * <SEP> * <SEP> engine <SEP> pump <SEP> * <SEP>
<tb><SEP> AV <SEP> pump <SEP> engine <SEP> * <SEP> FIG.2
<tb><SEP> *
<tb> 3 <SEP> th <SEP> MODE <SEP> * <SEP> * <SEP> engine <SEP> pump <SEP> *
<tb><SEP> AV <SEP> pumping <SEP> engine
<tb><SEP> 1 * <SEP>
<tb> 4 <SEP> th <SEP> MODE <SEP> * <SEP> * <SEP> engine <SEP> pump <SEP> * <SEP> I
<tb><SEP> AV <SEP> pump <SEP> engine
<Tb>
In the various transmission modes which will be described, the intermediate shafts 7 and 8 play the following roles: the shaft 7 (in the case of FIG. 1) or the shaft 8 (the case of FIG. 2) transmits to the second device ( T2, T3) the variable speed from the first device (H1, H2, T1). The transmission takes place from the ring 13 of the train T1 to the gears 21 and 31 of the trains T2 and T3.

The shaft 8 (the case of FIG. 1) or the shaft 7 (the case of FIG. 2) transmits the driving speed of the drive shaft 1 to the second device. The transmission is carried out by the gears 2 and 6. and the clutch E2, to the planet carrier 22 (in the case of FIG. 1) or by the gear 2 alone and the clutch E2 to the planet carrier 32 (the case of FIG. 2).

In both examples (FIGS. 1 and 2), the clutch E1 is located on the mechanical input channel of the driving power of the motor M in the first device, through the shaft 1, the gear 2, the gear 6 (only in FIG. 1) and the planet carrier 12.

In both cases, (FIGS. 1 and 2) the brake F1 gives an appui to the planet carrier 12 of the train T1.

In both cases (FIGS. 1 and 2) the brake F2 gives support to the crown of a train of the second device which receives the movement of the crown 13 of the train T1 through an intermediate shaft 7 (FIG. 1) or FIG. Figure 2). For Figure 1, it is the crown 33 of the train T3. For Figure 2, it is the ring 23 of the T2 train.

1st MODE (I) AND NOWING AT 2nd NODE (II) F1 and F2 are tight. The power of the motor M passes entirely and solely through the hydrostatic path of the drive (H1, H2) through the shaft 1, the gears 2 and 3, the shaft 4 and the pump H1. The hydrostatic drive (H1, H2) operates and drives the shaft 5 in both directions of rotation (front and rear rear).

The energy of the shaft 5 is transmitted to the output shaft 9 through the trains T1 and T2.

The hydrostatic variator (H1, H2) itself operates in the following manner (FIG. 3): After starting the heat engine M, the displacement of the pump H1 increases from zero to its maximum negative value (-1) which start and accelerate the vehicle. It is then possible to loosen the brake F1 and quickly reverse the direction of the fluid flow. This has the effect of bringing the relative speed in the clutch El to a theoretically zero value, so to allow to tighten
El without shock or degradation of energy to get the 2nd mode. In the first mode (I), the energy is transmitted from the train T1 to the output shaft 9 by the train T3 (case of FIG. 1) or by the train T2 on which the brake F2 is applied (case of FIG. 2).

2nd MODE (H) AND COHMUTATION IN THE 3rd HORDE (HUI)
El and F2 are tight. The power of the motor M passes partly directly through the hydrostatic path of the drive (H1, H2) as in the first mode and partly by the mechanical way to the train T1 through the clutch El.

The displacement of the pump H1 changes from the maximum value (+ 1) to the maximum value (-1), by reversing the flow direction of the fluid under pressure in the ducts A and R.

The output speed increases gradually. During such an inversion of flow direction, the pump H1 becomes motor, and the hydraulic motor H2 becomes pump.

When the displacement of the pump H1 reaches its maximum negative value (-1), the relative speed in the clutch E2 is close to zero. This makes it possible to loosen the brake F2 and to tighten the clutch E2 without shock or energy degradation to obtain the third mode.

In the second mode, the energy from the first device via an intermediate shaft is transmitted to the output shaft 9 by the train T3 in the case of FIG. 1 and the train T2 in the case of FIG.

3rd MODE (HERE) AND SWITCHING TO THE 4th NODE (IV)
El and E2 are tight. The power of the motor M is divided, as in the 2nd mode, partly through the hydrostatic drive of the drive (H1, H2) and partly by the mechanical way to the train T1 through the clutch El.

When the pump H1 has reached its maximum positive displacement (+ 1), it is possible to loosen E1 and quickly reverse the direction of flow in the ducts A and R.

This has the effect of bringing the relative speed between the planet carrier 12 which is no longer rotated and the brake F1 to a theoretically zero value which allows to tighten without shock or degradation of energy to obtain the 4th mode . In the third mode, the energy from the first device (H1, H2, T1) by an intermediate shaft is transmitted to the output shaft 9 by the train T2 (FIG. 1) or by the train T3 (FIG. 2). .

During the displacement variation of the pump H1 from (- 1) to (+ 1), a gradual reduction in the speed of the ring 13 of T1 is obtained, which causes the increase in the output speed.

4th MODE (IV) F1 and E2 are tight. By manipulating the displacement of the pump H1 from the maximum negative value (-1) to the maximum positive value (+ 1), the speed of the ring 13 of the train T1 is continued until it is turned upside down. . This has the effect of causing a last increase in the output speed of the shaft 9 through the train T2 (Figure 1) or the train T3 (Figure 2).

OBSERVATIONS
During the 1st and 2nd modes, the output torque is always proportional to the pressure in the hydrostatic machines H1 and H2, so that it is easy to calculate the power transmitted by the transmission from measurements of speed and pressure.

During the 2nd, 3rd and 4th modes, the partial power which transits in the hydrostatic way (H1,
H2) is defined by the torque and speed of the gear 11 of the train T1. This power changes sign through zero when the speed of pinion 11 is zero (zero displacement). This causes the hydrostatic machines H1 and H2 to change roles at the same time, the engine H2 becoming pump, and the pump H1 in front of the engine.

 Note that this hydrostatic power takes a generally decreasing form when the output speed increases, so that the overall efficiency quickly becomes less and less affected by intrinsic losses to hydraulics (H1, H2).

As a variant of operation, it is possible to replace the fourth mode by a last fully mechanical overdrive by clamping the brake F1 and keeping the displacement of the pump H1 at zero. Engine
H2 no longer rotates and the pinion 11 of the train T1 is immobilized. The ring 13 is immobilized as well. The power of the motor M enters the second device by the clutch E2. The best yield is thus obtained.

EXAMPLE NUNERIOUE: In one embodiment, by assigning the coefficient 100 to the maximum output speed obtained on the shaft 9 at the end of the mode
IV, the following output speeds can be realized
1st mode (I): from 0 to 12
2nd mode (II): from 12 to 36
3rd mode (III): from 36 to 68
4th mode (IV): from 68 to 100
ADVANTAGES
The hydromechanical transmission of the invention combines the advantages of continuity and progressivity offered by hydraulics - that is, by the variator (H1
H2) - and high efficiency offered by the epicyclic mechanical transmission (trains T1 - T2 - T3). This combination of hydraulics and mechanics is advantageously obtained by the double input of the energy supplied by the heat engine M to the train T1 of the first device, through the hydraulic path (shaft 4, machines H1 - H2, shaft 5 ) and through the mechanical way (clutch El and planet carrier 12) as well as by the combination of the two devices (H1 - H2 - T1) and (T2
T3).

 The transmission still allows to choose a fully mechanical operation, with the best efficiency, as a variant of the 4th mode, maintaining zero the displacement of the pump H1.

 An important advantage is to be able to reduce the dimensions of the hydraulic machines H1 and H2 because their torque characteristics depend only on the first mode (power input in the train T1 by the only hydraulic way) which is very reduced, so that the torque asked is weak. Cece allows the hydraulic machines H1 and H2 to be used in the zone of their "corner" power: full displacement, maximum pressure and speed.

 Another advantage is that the output torque can be constantly appreciated by the simple measurement of the pressure in the working circuit A, R hydrostatic machines H1 and H2, this giving ease of servocontrol of the output speed to the power transmitted.

 Finally, one advantage is that the transmission of the invention makes it possible, with relatively few members (in addition to the H1 - H2 variator: three trains T1, T2, T3, two clutches E1, E2 and two brakes F1, F2), a continuous variation of power under a considerable "opening", that is to say a very wide range of output speeds.

Claims (10)

 1. - hydromechanical transmission for motor vehicles, between a motor shaft (1) mt by a heat engine (M), and an output shaft (9) driving the wheels, this transmission of the type comprising on the one hand a hydrostatic drive to hydraulic pump (H1) and hydraulic motor (H2) interconnected by conduits go (A) and return (R) of pressurized fluid, and secondly a mechanical transmission by epicyclic gears, being characterized in this flood  it comprises a first device driven by the heat engine (M), and comprising said hydrostatic variator (H1 - H2) combined with an epicyclic gear train (T1), and a second entirely mechanical device consisting of two planetary gear trains (T2, T3) interconnected, the second device being driven by the first device and driving the output shaft (9).  2. - hydromechanical transmission according to claim 1, characterized in that  the motor shaft (1) is connected to the first device (H1 - H2 - T1) both by a hydraulic path leading to the train (T1), through a pair of gears (2, 3), a shaft (4 ) driving the hydraulic pump (H1) and a shaft (5) moved by the hydraulic motor (H2), and a mechanical path leading to the train (T1) through a clutch (El).  3. - hydromechanical transmission according to claim 1, characterized in that  the first device (H1 - H2 - T1) is connected to the second device (T2 - T3) by two coaxial intermediate shafts, one central (7) and the other tubular (8) carried by the central shaft ( 7).  4. - hydromechanical transmission according to claims 1 and 3, characterized in that  the driving shaft (1) is parallel to the output shaft (9) and the intermediate shafts (7) and (8).  5. - hydromechanical transmission according to claims 1, 2 and 3, characterized in that stinks  the epicyclic gear train (T1) of the first device (H1 H2 - T1) comprises a pinion (11) set in rotation on the output shaft (5) of the hydraulic motor (H2), a planet carrier (12) immobilizable by means of a brake (F1) and connected to a clutch (El) connecting the motor shaft (1), and a ring (13) integral in rotation with one of the intermediate shafts (7, 8).  6. - hydromechanical transmission according to claims 3 and 5, characterized in that stinks  the ring (13) of the train (T1) of the first dipositif (H1 - H2 - T1) is connected to two gears or planetaries (21, 31) carried by one of the intermediate shafts (7, 8), the two sun gears ( 21, 31) belonging to the trains (T2) and (T3) of the second device (T2 - T3), and in that the planet carrier (12) of the train (T1) of the first device is connected to one of the doors -satellites (22, 32) of the trains (T2) or (T3) of the second device (T2 - T3) by the clutch (El) and by a clutch (E2) connected to another intermediate shaft (8, 7) one of said planet carriers (22, 32) of the trains (T2) or (T3) of the second device (T2 - T3).  7. - hydromechanical transmission according to claims 1 and 6, characterized in that stinks  the second device (T2, T3) comprises a ring (23, 33) of one of the trains (T2) to (T3) connected to the planet carrier (32, 22) of the other train (T3) or (T2 ) and secured in rotation to said planet carrier (32, 22), a brake (F2) capable of immobilizing one of the rings (33, 23) of one of the trains (T3) or (T2), and what one of said crowns (23, 33) of one of the trains (T2) or (T3) as well as one of the planet carriers (32, 22) of one of the trains (T3) or ( T2) are integral in rotation with the output shaft (9).  8. - hydromechanical transmission according to claims 6 and 7, characterized in that stinks  The second device (T2, T3), entirely mechanical, comprises four junctions: the first intermediate shaft (7) or (8), permanently connected to the ring (13) of the first device of which it is integral in rotation, the second, planet carrier (32) or (22) of one of the trains (T3) or (T2), permanently connected to the output shaft (9) of which it is integral in rotation, the third, ring (33) or (23) of one of the trains (T3) or (T2), capable of being immobilized in rotation by the brake (F2) and integral in rotation with the output shaft (9), and the fourth, door -satellites (22) or (32) of one of the trains (T2) or (T3) capable of being secured in rotation with the planet carrier (12) of the train (T1) of the first device by the clutches (E2 ) and (El).  9. - hydromechanical transmission according to claims 1 and 3, characterized in that stinks  The drive shaft (1), the central intermediate shaft (7) and the output shaft (9) are in axial extension.  10. - hydromechanical transmission according to claims 5 and 9, characterized in that stinks  The epicyclic gear train (T1) of the first device (H1 H2 - T1) comprises a pinion (11) set in rotation on an intermediate shaft (10) carrying another pinion (14) driven in rotation by the output shaft (5) of the hydraulic motor (H2> via a pair of gears (15, 16), one of which (16) is integral in rotation with the shaft (5), the intermediate shaft (10) being tubular and coaxial with the intermediate shafts (7, 8) and carried by them, and in that the central intermediate shaft (7) is connected directly to the drive shaft (1) via the clutch (E2).