FR2801358A1 - Transmission system with branching power drives has independent locking mechanisms for first and second converter shafts - Google Patents

Abstract

The transmission system (10) consists, from front to rear, of an input shaft (12), first (16) and second (18) epicycloid gear trains, and an output shaft (20) coupled to an axle (24). The gear trains are connected rotationally to one another, to the input and output shafts and to the primary shaft (40) of a controlled hydrostatic converter (42) which can vary the ratio of the first train. They are also connected selectively to a second shaft (44) of the converter which can vary the ratio of the second train. The system incorporates independent locking mechanisms for the first and second converter shafts to prevent hydraulic losses in the converter.

Description

"Power bypass transmission comprising means for blocking its elements" The invention relates to a power bypass transmission, in particular for a motor vehicle.

The invention relates more particularly to a power bypass transmission, in particular for a motor vehicle, of the type which comprises, from upstream to downstream, an input shaft which is coupled to a vehicle engine, first and second epicyclic trains , and output shaft which is coupled to a bridge to drive at least one vehicle wheel, of the type in which first and second elements of the first and second planetary gears, in particular first and second planetary gears, planet carriers and crowns are linked in rotation to each other, to the input shaft, to the output shaft, to a first shaft of a controlled hydrostatic converter capable of varying the reason for the first planetary gear, and are selectively linked to a second hydrostatic converter shaft capable of varying the reason for the second planetary gear train by interconnection with one or the other of two of the second elements of the second planetary gear train.

The document FR-2.520.827 describes and represents an example of such a transmission.

This transmission comprises a first and a second planetary gear train, the planets of which are both linked in rotation to the input shaft of the transmission, and of which the planet carriers are both linked in rotation to the output shaft of the transmission. A first hydraulic member of a hydrostatic converter is linked to the crown of the first planetary gear train, and a second hydraulic member of said hydrostatic converter is capable of being selectively linked in rotation to a crown of the second planetary gear train or else to a pinion meshing with the transmission output shaft. In this document, the hydrostatic converter hydraulic members are, in known manner, axial piston pump motors, the flow rates of which can be regulated by adjusting the respective inclinations of plates on which the axial pistons of each of the hydraulic members are supported, to allow their operation at regulated speeds and torques.

In this way, the transmission is capable of determining two modes of operation, in particular a mode of operation called "with coupled output" for which the second hydraulic member of the hydrostatic converter is' in rotation with a pinion meshing with the output shaft of transmission, and a mode of operation called "two adaptation points" for which the second hydraulic member of the hydrostatic converter is linked in rotation to the crown of the second planetary gear.

The so-called "coupled output" operating mode makes it possible to obtain at least one operating point, called the "adaptation point", of the hydrostatic converter for which the first member is at zero speed to block the crown of the first epicyclic gear train, and for which the second hydraulic member has zero displacement, and the operating mode known as "with two adaptation points" makes it possible to obtain at least two operating points, called adaptation points, for which one of the hydraulic members is at zero speed to block the crown of the first planetary gear or else the crown of the second planetary gear and for which the other hydraulic member is at zero speed.

Thus, for each adaptation point, when a hydraulic member is at zero speed, the other member has zero displacement so as to interrupt the circulation of hydraulic fluid between two members.

For these two operating modes, blocking one of the other of the rings of the first planetary gear train or of the second planetary gear train makes it possible in particular to establish high gear ratios of the transmission.

The disadvantage of such a transmission that, even when one of the hydraulic members is at zero speed and the other at zero displacement, part of the mechanical energy which travels in the transmission is absorbed in pure loss by the variator hydrostatic, in particular in the form of fluid losses and internal friction in the hydraulic member which has zero displacement.

This loss of mechanical energy strongly penalizes the efficiency of such a transmission.

To remedy this drawback, the invention proposes transmission of the type described above eliminating this loss.

For this purpose, the invention provides a transmission of the type described above, characterized in that it comprises independent mechanical means for blocking the first second shafts of the hydrostatic converter to avoid losses of hydraulic energy in said hydrostatic converter.

According to other characteristics of the invention - the first sun gear and the second ring are linked to the input shaft, the first and second planet carriers are linked to the output shaft and are capable of being linked in rotation to the second shaft of the hydrostatic converter, the first ring is linked to the first shaft of the hydrostatic converter, and the second sun gear is capable of being linked rotation to the second shaft of the hydrostatic converter, - the independent mechanical blocking means include a first brake which acts on the first ring gear and a second brake which acts on the hydrostatic converter output shaft, - the first brake is a band brake in that the second brake is a disc brake, - the transmission comprises double clutch means which allow to selectively link in rotation the second sun gear to the second shaft of the hydrostatic converter or to link the output shaft to the second shaft of the hydrostatic converter, - the hydrostatic converter comprises first and second hydraulic members, are associated respectively with the first and second converter shafts, which are hydraulically connected to each other, each of which is capable of operating as a pump or good hydraulic motor with a controlled variable displacement, to transmit a movement of rotation, of torque and of speed of determined values, from one of the first and second hydraulic members to the other of the first and second hydraulic members according to torque and speed of regulated values, - the transmission comprises control means which are capable of establishing a mode of operation known as with coupled output, in which double clutching means link in rotation the output shaft to the second shaft of the hydrostatic converter, which allows the minus one operating point, known as an adaptation point, of the hydrostatic converter for which the first member is at zero speed to block the first ring, and for which the second hydraulic member is at zero displacement, and a mode of operation known as two adaptation points, in which the double clutching means link in rotation the second planetary to the second shaft of the hydrostatic converter, and which allows at least two operating points, called adaptation points, for which one of the hydraulic members is at zero speed to block the first ring or else the second planetary and for which the other hydraulic unit has zero displacement, - the control means activate the first brake, in the operating mode with coupled output or in the operating mode with two adaptation points, when the hydrostatic converter is at the adaptation point for which the first hydraulic member is at zero speed, and the control means activate the second brake, in the operating mode operation at two adaptation points, when the hydrostatic converter is at the adaptation point for which the second hydraulic member is at zero speed the first and second hydraulic members of the hydrostatic converter are motor pumps which each have a shaft to which it is integral a tilting plate in a controlled manner on which are supported axial pistons, resiliently biased against the plate, and which slide in a chamber following a stroke which is determined by the inclination of the plate, the variation of the piston stroke in their chambers determining the variable displacement of each motor-pump.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which - Figure 1 is a schematic view of a power bypass transmission according to the invention, the first brake of which is activated; and FIG. 2 is a view according to FIG. 1 of the power bypass transmission according to the invention, the second brake of which is activated.

In the description which follows, identical reference numerals designate identical parts having similar functions.

has shown in Figures 1 and 2 the assembly of a power derivation transmission 10 produced in accordance with the invention.

in known manner, the power diversion transmission 10 comprises an input shaft 12 which is coupled, for example by means of a clutch 13, to a vehicle engine 14, a first planetary gear train 16 and a second train 18 planetary, and an output shaft 20 which is coupled, in particular by means of a bridge descent shaft 22, to a bridge 24 to drive at least one wheel 26 vehicle.

The first epicyclic gear 16 and the second epicyclic gear 18 respectively comprise first elements including a first planetary 28, a first planet carrier 30, first ring 32, and second elements including second planetary 34, a second planet carrier 36, and second crown 38.

In a known manner, some of the first planetary first gear elements 16 and of the second planetary second gear elements 18 are permanently linked to each other, to the input shaft 12 of the transmission 10, to the output shaft of the transmission 10, and to a first hydrostatic converter shaft 42 to vary the reason for the first planetary gear 16, and some of the second elements of the second planetary gear train 18 are selectively linked to a second shaft 44 of the hydrostatic converter 42 for varying the reason for the second planetary gear 18 by interconnection with one or the other of two of the second elements of the second planetary gear 18.

In particular, in the preferred embodiment of the invention, and without limitation thereof, the first sun gear 28 and the second ring 38 are linked to each other and are linked to the shaft d input 12 of the transmission 10, the first 30 and second 36 planet carriers are linked to each other and are linked to the output shaft 20 of the transmission 10, and first ring 32 is linked to the first shaft 40 hydrostatic converter 42.

Furthermore, interconnection means 46 make it possible selectively to link the first 30 and second 34 planet carriers to the second hydrostatic converter shaft 44 or else to link the second planet gear 34 to the second shaft 44 of the hydrostatic converter 42.

The first ring 32 of the first planetary gear 16 meshes with an upstream pinion 48 arranged at the end of a primary intermediate shaft 50, the other end of which carries a downstream pinion 52 which meshes with a pinion 54 carried by the first shaft 40 of the converter 42 hydrostatic.

In a similar way, a idler gear 56, which meshes directly with the second sun gear 34 of the second planetary gear 18, and a pinion which meshes with an upstream gear 60 arranged at the end of a secondary intermediate shaft 62 whose other end carries a downstream pinion 64 which meshes with a pinion 66 carried by the output shaft 20, are capable of being selectively clutched by the clutch means 46 on the second shaft 44 of the hydrostatic converter 42 to selectively link in rotation the second shaft 44 of the hydrostatic converter to the second sun gear 34 or else to the output shaft 20.

To this end, the dog clutch means 46 consist in particular of a double dog clutch capable of clutching either the idler gear 56 or the pinion 58 in two extreme and opposite positions.

In known manner, the hydrostatic converter 42 is composed of a first hydraulic member 70 and a second hydraulic member 72, which are associated respectively with the first shaft 40 and with the second shaft 44 of the converter, which are hydraulically connected one to the other. the other, and each of which is capable of operating as a pump or else as a hydraulic motor with a controlled variable displacement, to transmit a movement of rotation, of torque and of speed of determined values, from the first 70 and second 72 hydraulic members to the other hydraulic members 70, 72 according to torque and speed regulated values. To this end, the first hydraulic member and the second hydraulic member 72 are both controlled by the control means (not shown).

In this configuration, the transmission control means 10 are capable of establishing two operating modes.

In these two operating modes, a fraction of the driving power is taken up by the first hydraulic member 70, which then operates as a hydraulic pump, on the first planetary gear 16 and is transformed into hydraulic power. This hydraulic power is transmitted to the second hydraulic member which restores it to the second planetary gear 72. The control means make it possible to control the torque speed values of the first 70 and second 72 hydraulic members by regulating the displacements of these.

In known manner each of the first hydraulic member 70 and second hydraulic member 72 are motor-pumps which each comprise an associated shaft 40 and 44 of which is secured a tilting plate in a controlled manner on which are supported axial pistons, resiliently recalled at 'against plate, and which slide in a chamber following a stroke which is determined by the inclination of the plate, the variation of the stroke of the pistons in their chambers determining the variable displacement of each motor-pump.

As the detail of the structure of such pump motors is well known in the state of the art, this will not be described in more detail.

In this configuration, the transmission control means 10 are first of all capable of establishing a mode of operation known as "with coupled output", in which the double clutch 68 rotatably links the shaft 44 of the hydrostatic converter 42 to the output shaft 20. This operating mode is used in particular for vehicle starting and for its operation at reduced speed.

At start-up, the output torque is supplied to the output shaft only by the second hydraulic member 72 supplied by the first hydraulic member 70 and operates at full displacement. Then the speed of rotation of the output shaft 20 gradually increases by increasing the displacement of the first hydraulic member 70 to a maximum speed of rotation. Simultaneously, the output torque, resulting from the addition of the torque supplied to the output shaft 20 of the second hydraulic member 72 and of the torque traveling in two planetary gears 16 and 18, gradually increases to a maximum value which is obtained when the first 70 and second 72 hydraulic members both operate at full displacement.

The speed of rotation speed of rotation of the shaft can then be further increased by reducing the cylinder capacity of the second hydraulic member 72.

The displacement of the second hydraulic member 72 decreasing, the transmission reaches an operating point for which the displacement of the second hydraulic member 72 is zero and for which the speed of the first hydraulic member 70 is zero This operating point, called adaptation , of the hydrostatic converter 42 for which the first member is at zero speed, makes it possible to block the first ring and the second hydraulic member 72, which is at zero displacement, therefore rotates empty and at zero torque.

Beyond this adaptation point, for high rotational speeds of the output shaft 20, the transmission control means 10 are capable of establishing a mode of operation called "two adaptation points", in which the double clutch 68 rotates the second shaft 44 of the hydrostatic converter 42 to the second sun gear 34.

operating mode with two adaptation points makes it possible to establish at least two operating points, called adaptation points, for which one of the hydraulic members 70 or 72 is' zero speed to block the first ring 32 or else the second sun gear 34 and for which the other hydraulic member 70 or 72 has zero displacement, and therefore rotates empty and at zero torque.

first adaptation point corresponds to blocking the first ring 32 by the first hydraulic member while the second hydraulic member 72, which is of zero displacement, therefore rotates empty and at zero torque.

This first adaptation point allows in particular the passage from the operating mode known as "with coupled output" operating mode known as "with two adaptation points", the double clutch 68 passing from the position in which it rotates the shaft 44 from the hydrostatic converter 42 to the output shaft 20 to that in which it rotates the second shaft 44 of the hydrostatic converter 42 to the second sun gear 34.

Starting from this first adaptation point, the increase in the speed of rotation of the output shaft 20 is obtained by reducing the displacement of the first hydraulic member 70 and by increasing that of the second hydraulic member 72. The second hydraulic member 72 then operates as a hydraulic pump to supply the first hydraulic member 70 which operates as a motor.

The transmission 10 then reaches a second adaptation point for which the second hydraulic member 72 is at full displacement and at zero speed to block the second sun gear 34 of the second planetary gear 18 while the first hydraulic member 70 is at zero displacement and therefore rotates empty at zero torque. The drawback of the transmission 10 is that, in each of the adaptation points mentioned above, blocking of one of the elements of the planetary gear trains 16 or by one of the hydraulic members 70 or 72 consumes part of the hydraulic energy which travels in hydrostatic converter 42, in particular in the form of fluid losses and friction.

These fluid losses and these frictions alter the overall efficiency of the transmission 10.

To remedy this drawback, the invention provides a transmission 10 of the type described above, which comprises independent mechanical means for blocking the first 40 shaft and second shaft 44 of the hydrostatic converter 42 to avoid losses of hydraulic energy in said converter 42 hydrostatic.

To this end, the transmission 10 comprises a first brake 74 acts on the first ring 32 and a second brake which acts on the output shaft 44 of the hydrostatic converter, and more particularly on the idler gear 56 is carried by the shaft 44 converter output 42.

The first brake 74, which is shown in Figure 1 and the second brake 76, which is shown in Figure 2, are both controlled by the control means. In particular, the control means activate the first brake 74, in the operating mode with coupled output or in the operating mode with two adaptation points, when the hydrostatic converter 42 is at the first adaptation point for which the first hydraulic member 70 is at zero speed, and the control means activate the second brake in the operating mode with two adaptation points, when the hydrostatic converter 42 is at the second adaptation point for which the second hydraulic member 72 is at zero speed. In this way, the shaft 40 of the first hydraulic member 70 and the shaft 44 of the second hydraulic member 72 can be blocked respectively by the first brake 74 and by the second brake 76, any hydraulic loss of energy is eliminated in the converter hydrostatic.

Any known means of embodiment can be used for producing the first brake 74 and second brake 76. However, in the preferred embodiment of the invention, the first brake 74 is preferably a band brake and the second brake 76 is of preferably a disc brake.

The invention therefore advantageously makes it possible to benefit from a power derivation transmission 10 of excellent efficiency.

Claims (7)

<U> CLAIMS </U> 1. Power derivation transmission (10), in particular for a motor vehicle, of the type which comprises, from upstream to downstream, an input shaft (12) which is coupled to an engine (14) of the vehicle, a first ( 16) a second (18) planetary gear, and an output shaft (20) which is coupled to a bridge (24) to drive at least one wheel (26) of the vehicle, of the type in which first and second elements are first and second planetary gears, in particular first and second planetary gears (28, 34), planet carriers (30, 36) crowns (32, 38) are linked in rotation to the others, to the input shaft (12), to the shaft output (20), a first shaft (40) of a hydrostatic converter (42) controlled capable of varying the reason of the first planetary gear (16), and are selectively linked to a second shaft (44) converter (42) hydrostatic likely to vary due to the second planetary gear train (18) by interconnection with either of two of the second elements of the second planetary gear train, characterized in that it comprises independent mechanical means for blocking the first (40) and second (44) shafts of the hydrostatic converter (42) to avoid losses of hydraulic energy in said converter (42) hydrostatic. 2. Transmission (10) according to the preceding claim, characterized in that the first sun gear (28) and the second ring gear (38) are linked to the input shaft (12), the first (30) and second (36 ) planet carriers are linked to the output shaft (20) and are capable of being linked in rotation to the second shaft (44) of the hydrostatic converter (42), the first ring (32) is linked to the first shaft (40 ) of the hydrostatic converter (42), and the second sun gear (34) is capable of being linked in rotation to the second shaft (44) of the hydrostatic converter (42). 3. Transmission (10) according to the preceding claim, characterized in that the independent mechanical locking means comprise a first brake (74) which acts on the first ring (32) and a second brake (76) which acts on the shaft (44) outlet of the hydrostatic converter (42). 4. Transmission (10) according to the preceding claim, characterized in that the first brake (74) is a band brake in that the second brake (76) is a disc brake. 5. Transmission (10) according to any one of claims 2 to 4, characterized in that it comprises means (68) of double clutch which allow to selectively link in rotation the second sun gear (34) to the second shaft (44) of the hydrostatic converter (42) or to link the output shaft (20) to the second shaft (44) of the hydrostatic converter (42). 6. Transmission (10) according to any one of the preceding claims, characterized in that the hydrostatic converter (42) comprises first (70) second (72) hydraulic members, which are associated respectively with the first (40) and second (44) converter shafts (42), which are hydraulically connected to each other, each of which is capable of operating as a pump or else as a hydraulic motor with a controlled variable displacement, for transmitting a movement of rotation, torque and speed of determined values, from one first (70) and second (72) hydraulic components to the other first (70) and second (72) hydraulic components according to torque and speed of regulated values. 7. Transmission (10) according to the preceding claim taken in combination with claim 5, characterized in that it comprises control means which are capable of establishing - an operating mode called coupled output, in which means (68) double interconnection link in rotation the output shaft (20) to the second shaft (44) of the hydrostatic converter (42), and which allows at least one point of operation, adaptation, of the hydrostatic converter (42) for which first member (70) is at zero speed to block first ring (32), and for which the second hydraulic member (72) has zero displacement, and - a mode of operation known as two adaptation points, in which the means ( 68) of double interconnection in rotation link the second sun gear (36) to the second shaft (44) of the hydrostatic converter (42) and which allows at least two operating points, called adaptation points, for which one of the hydrauliq ues (70, 72) is at zero speed to block the first ring (32) or the second planet (34) and for which the other hydraulic member (70, 72) with zero displacement. . Transmission (10) according to the preceding claim taken in combination with one of claims 3 characterized in that the control means activate the first brake (74), in the operating mode with coupled output or in the two-point operating mode adaptation, when the hydrostatic converter (42) is an adaptation point for which the first hydraulic member (70) is at zero speed, and in that the control means activate the second brake (76), in the mode of operation at two adaptation points, when the hydrostatic converter (42) is at the adaptation point for which the second hydraulic member (72) is at zero speed. 9. Transmission (10) according to any one of claims 6 to 8, characterized in that the first (70) second (72) hydraulic members of the hydrostatic converter (42) are motor-pumps which each comprise a shaft (40 , 44) which is integral with a tiltable plate in a controlled manner on which are supported axial pistons, resiliently biased against the plate, and which slide in a chamber following a stroke which is determined by the inclination of the plate, the variation of the piston stroke in their chambers determining the variable displacement of each motor-pump.