U.S. patent application number 12/863478 was filed with the patent office on 2011-01-27 for hydraulic motor device for assisting the mechanical transmission of a vehicle.
Invention is credited to Jean Heren, Gilles Lemaire.
Application Number | 20110017059 12/863478 |
Document ID | / |
Family ID | 39790199 |
Filed Date | 2011-01-27 |
United States Patent
Application |
20110017059 |
Kind Code |
A1 |
Heren; Jean ; et
al. |
January 27, 2011 |
HYDRAULIC MOTOR DEVICE FOR ASSISTING THE MECHANICAL TRANSMISSION OF
A VEHICLE
Abstract
A hydraulic motor device including a hydraulic motor having a
cylinder block and a cam that are mounted to move in rotation
relative to each other. The motor has a fluid distributor for the
cylinders, a portion of which distributor is constrained in
rotation with the cam, and a stationary distribution coupling
connecting the distributor to a fluid feed and to a fluid
discharge. The motor has a through passage disposed along the axis
of rotation for the purpose of receiving a transmission shaft
segment. The motor can be declutched by radially uncoupling the
pistons from the cam, the cylinder block remaining stationary
relative to the reference frame of the vehicle, and the cam being
constrained in rotation with a transmission shaft segment that is
disposed in the through passage. The device may be used in addition
to or as a replacement for a mechanical transmission.
Inventors: |
Heren; Jean; (Margny Les
Compiegne, FR) ; Lemaire; Gilles; (Margny Les
Compiegne, FR) |
Correspondence
Address: |
LADAS & PARRY LLP
224 SOUTH MICHIGAN AVENUE, SUITE 1600
CHICAGO
IL
60604
US
|
Family ID: |
39790199 |
Appl. No.: |
12/863478 |
Filed: |
January 20, 2009 |
PCT Filed: |
January 20, 2009 |
PCT NO: |
PCT/FR2009/050077 |
371 Date: |
October 7, 2010 |
Current U.S.
Class: |
91/491 |
Current CPC
Class: |
B60K 7/0015 20130101;
F03C 1/0403 20130101; F03C 1/0425 20130101; B60K 2007/0092
20130101; B60K 17/10 20130101 |
Class at
Publication: |
91/491 |
International
Class: |
F01B 1/06 20060101
F01B001/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 29, 2008 |
FR |
0850533 |
Claims
1-16. (canceled)
17. A hydraulic motor device, in particular for assisting the
mechanical transmission of a vehicle, which hydraulic motor device
includes a hydraulic motor that comprises a cylinder block having
cylinders slidably receiving radial pistons, and a reaction cam for
the pistons, the cylinder block and the cam being mounted to move
in rotation relative to each other about an axis of rotation, the
motor further comprising a fluid distributor for the cylinders, a
portion of which distributor is constrained in rotation with the
cam, and a distribution coupling mounted to be stationary relative
to a reference frame of the vehicle and for connecting the
distributor to a fluid feed and to a fluid discharge, the motor
having a through passage disposed along the axis of rotation for
the purpose of receiving a transmission shaft segment, wherein the
motor can take up a declutched configuration in which the pistons
are radially uncoupled from the cam, the cylinder block is
stationary relative to the reference frame of the vehicle, while
the cam is rotary, and the cam is constrained in rotation with a
transmission shaft segment that is disposed in said through
passage.
18. A device according to claim 17, further including a drive part
secured to the cam and that is suitable for co-operating with said
transmission shaft segment to drive said shaft segment in
rotation.
19. A device according to claim 18, wherein the drive part and the
transmission shaft segment are formed integrally as a single
part.
20. A device according to claim 17, wherein, on its periphery, the
hydraulic motor has a connection portion adapted to transmit
torque.
21. A device according to claim 17, wherein the distribution
coupling has a sleeve portion whose inside periphery forms a
portion of the through passage.
22. A device according to claim 21, wherein the distributor is
disposed around said sleeve portion.
23. A device according to claim 21, wherein the sleeve portion
extends in an internal passage in the cylinder block.
24. A device according to claim 21, wherein the sleeve portion
co-operates with at least one rotary support bearing for supporting
the shaft segment in rotation relative to the motor.
25. A device according to claim 17, wherein the distributor is
disposed on the other side of the cylinder block from the fluid
feed and fluid discharge.
26. A device according to claim 25, wherein the distributor is
connected to the fluid feed and to the fluid discharge via ducts
passing through the cylinder block between the cylinders.
27. A device according to claim 17, wherein the distributor is
disposed on the same side of the cylinder block as the fluid feed
and fluid discharge.
28. A device according to claim 17, wherein the cylinders extend
radially relative to the axis of rotation, and the cam surface of
the reaction cam is disposed around the cylinder block and faces
towards the axis of rotation.
29. A device according to claim 17, wherein the distributor for the
cylinders is constrained in rotation with the cam.
30. A vehicle drive system, comprising a mechanical transmission
operated by at least one main engine or motor, and a device
according to claim 17, the transmission shaft segment being a
portion of the mechanical transmission.
31. A vehicle drive system according to claim 30, in which system
the transmission shaft segment is a portion of a main transmission
shaft connected to the main engine or motor.
32. A vehicle drive system according to claim 30, in which the
transmission shaft segment is a portion of a secondary transmission
shaft that is connected to a main transmission shaft of the
mechanical transmission.
Description
[0001] The present invention relates to a hydraulic motor device,
in particular for assisting the mechanical transmission of a
vehicle, which hydraulic motor device includes a hydraulic motor
that comprises a cylinder block having cylinders slidably receiving
radial pistons, and a reaction cam for the pistons, the cylinder
block and the cam being mounted to move in rotation relative to
each other about an axis of rotation, the motor further comprising
a fluid distributor for the cylinders, a portion of which
distributor is constrained in rotation with the cam, and a
distribution coupling mounted to be stationary relative to a
reference frame of the vehicle and for connecting the distributor
to a fluid feed and to a fluid discharge, the motor having a
through passage disposed along the axis of rotation for the purpose
of receiving a transmission shaft segment.
[0002] Such devices can be used to drive certain vehicles, such as,
for example, combine harvesters or other farm or worksite
vehicles.
[0003] Such a vehicle, in addition to requiring a high speed
serving for driving the vehicle on the road ("road mode"), also
need a high-torque low speed for driving the vehicle at low speed
with a view to doing a specific piece of work ("work mode"). In
work mode, the drive applied to the vehicle can require very fine
control of speed or of path, moving the vehicle at low speed,
absence of wheel spin, and, above all, very high torque.
[0004] In order to make it possible to use these two modes, such
vehicles are generally equipped with a hybrid, mechanical and
hydraulic transmission. Such a transmission is made up of a
mechanical main transmission suitable for transmitting the drive
torque from a main engine or motor via mechanical links, and of a
hydraulic auxiliary transmission including a hydraulic motor device
such as the device presented in the introduction.
[0005] In the hydraulic auxiliary transmission, a fraction of the
power delivered by the main engine or motor (generally an internal
combustion engine) is converted by means of the hydraulic motor
device into a fluid pressure and is transferred to a hydraulic
motor. The hydraulic motor in turn relays drive torque to the main
mechanical transmission, in particular for low rotation speeds,
replacing the torque delivered by the main engine.
[0006] Advantageously, such a drive system makes it possible for
the vehicle to have the desired two different modes of use.
[0007] In road mode, drive is applied to the vehicle in
conventional manner via the mechanical transmission that transmits
the torque from the main engine to the wheels. The hydraulic motor
device is then inactive and the hydraulic motor is declutched from
the mechanical transmission.
[0008] Conversely, in work mode, drive via the main engine only is
inappropriate because it would require the speed of rotation of the
outlet shaft of said engine to be geared down excessively, and
would not generate the required torque.
[0009] In such a situation, the hydraulic motor device is used. Its
radial-piston hydraulic motor offers the required capabilities for
applying drive to the vehicle in work mode, and for doing the work
in question under good conditions, because it is particularly
suitable for delivering high torque at a low speed of rotation. The
rotary drive torque is then delivered by the hydraulic motor,
replacing the torque transmitted in road mode to the mechanical
main transmission by the main engine.
[0010] Patent FR 2 739 418 presents such an assistance hydraulic
motor. In the device presented by that patent, the motor has a
stationary casing that has its inside face arranged to form a cam,
and houses a cylinder block mounted to rotate relative to the
casing. The cylinder block is secured to a positive clutch so as to
enable the hydraulic motor to be clutched or declutched so as to
drive, or not drive, a mechanical transmission shaft that passes
through the motor.
[0011] In such a device, it is necessary for the mechanical
transmission shaft to be at a standstill or to be rotating very
slowly for the clutching or declutching by the positive clutch to
take place, and that is not very practical. In addition, it
complicates the structure of the motor and increases its
dimensions, by making it necessary for the positive clutch element
that is driven by the cylinder block to be mounted to move axially
along the axis of the mechanical transmission shaft in order to
engage with or disengage from the teeth of the positive clutch.
[0012] In addition, when the hydraulic motor is in engagement (via
the positive clutch) with the mechanical transmission, the maximum
speed of rotation is limited, and, with the motor as described, it
is not possible to uncouple the hydraulic motor by retracting the
pistons. For that reason, in practice, as drive means for driving
the rotary portions of the mechanical transmission directly in
rotation, it is necessary to use either the internal combustion
engine, or the hydraulic motor, but not both at the same time.
[0013] Another solution consists in using a hydraulic motor device
that has a rotary cylinder block engaged with a transmission shaft
segment, and whose pistons can be held in positions in which they
are uncoupled from the cam by being retracted into their cylinders,
so as to maintain the motor in the declutched configuration.
However, since the cylinder block is in engagement with the
transmission shaft segment, it rotates with said shaft even when
the pistons are uncoupled, thereby subjecting said pistons to
centrifugal forces that tend to make them come out of the
cylinders. For the declutched configuration, it is thus necessary
to balance said forces by fluid pressures that hold the pistons in
the positions in which they are retracted in the cylinders. As a
result, the means necessary for operation in the declutched
configuration are relatively complex.
[0014] Thus, with that solution also, as drive means for driving
the rotary portions of the mechanical transmission directly in
rotation, it is necessary to use either the internal combustion
engine, or the hydraulic motor, but not both at the same time.
[0015] A first object of the present invention is to design a
device of the type presented in the introduction, and in which the
hydraulic motor can be declutched from the mechanical transmission,
or can deliver additional torque thereto, or can operate as a
replacement therefore, while also remaining relatively simple, and
in particular without having a positive clutch.
[0016] This object is achieved by the fact that the motor can take
up a declutched configuration in which the pistons are radially
uncoupled from the cam, the cylinder block is stationary relative
to the reference frame of the vehicle, while the cam is free to
rotate, and the cam is constrained in rotation with a transmission
shaft segment that is disposed in said through passage.
[0017] In the cylinder block, when the pistons are in the
"retracted" position, i.e. when the cam is in the uncoupled
position, the motor is in declutched mode. In this mode, since the
cylinder block is stationary, the pistons are not subjected to any
centrifugal force, and this results in the pistons being in a
stable uncoupled position. This result cannot be obtained with the
above-mentioned motor having a rotary cylinder block disposed
inside a stationary cam.
[0018] The fact that the transmission shaft segment and the cam are
constrained in rotation is generally used to transmit drive torque
from the cam to the transmission shaft segment. However, the cam or
optionally an intermediate part connected to the cam may itself be
part of the mechanical transmission, and thus receive the drive
torque transmitted by the transmission shaft segment, so as to
transmit it to drive members for moving the vehicle, for example.
In which case, the drive torque generated by the hydraulic motor
may be transmitted directly by the cam to said drive members,
without going via the transmission shaft segment.
[0019] Finally, in the hydraulic motor, the cylinder block is
stationary relative to the reference frame of the vehicle, i.e. the
cylinder block does not rotate. As a result, no centrifugal force
is applied to the pistons of the cylinder block. It is thus easy to
keep the motor in the declutched configuration.
[0020] In addition, by means of the invention, it is possible to
clutch or declutch the hydraulic motor, even if the transmission
shaft segment is rotating at a significant speed.
[0021] It should be noted, in particular, that, compared with a
purely mechanical transmission that is designed mainly for road
mode, the hydraulic motor device of the invention considerably
simplifies the gearbox and the transmission, by avoiding any need
to provide additional reducing gear stages for the working speeds
that are very slow.
[0022] Conversely, mechanical transmissions that are designed
mainly for the work mode do not offer good efficiency in road mode.
The invention makes it possible to avoid this problem, by providing
a very good transmission for the work mode, and a transmission that
is optimized for road mode. More precisely, with the invention, the
hydrodynamic drag of the hydraulic motor is very low, and thus does
not adversely affect the efficiency of the transmission when said
transmission is in road mode.
[0023] In an embodiment, the device further includes a drive part
secured to the cam and that is suitable for co-operating with said
transmission shaft segment to drive said shaft segment in
rotation.
[0024] For example, the drive part may be provided with internal
fluting on one end, which fluting is suitable for co-operating with
complementary fluting on the transmission shaft segment to secure
the part to the transmission shaft segment.
[0025] Since the drive part transfers the drive torque from the cam
to the transmission shaft segment, the cam thus remains of small
dimensions, thereby enabling it to be replaced at lower cost, and
reducing its manufacturing cost, since the manufacturing
constraints for machining the cam are particularly stringent.
[0026] In an embodiment, the drive part and the transmission shaft
segment are formed integrally as a single part. Thus, the
transmission is simplified by means of it having a small number of
parts, and the risk of malfunctioning at the junction between the
drive part and the transmission shaft segment is eliminated.
[0027] In an embodiment, on its periphery, the hydraulic motor has
a connection portion adapted to transmit torque, e.g. a flange.
Thus, instead of the torque being transmitted substantially in the
vicinity of the axis of the transmission shaft segment, the torque
is transmitted via a connection portion that is of larger diameter.
Thus the mechanical stresses received by said connection portion
are small. The connection portion can be situated on any part of
the motor that is constrained to move with the cam, such as the
drive part, the cam itself, or any other portion of the casing of
the motor that is constrained to move with the cam. Transmitting
the torque via such a connection portion rather than via one end of
the transmission shaft segment also advantageously makes it
possible to increase the compactness of the transmission by
reducing its overall axial size.
[0028] In an embodiment, the distribution coupling has a sleeve
portion whose inside periphery forms a portion of the through
passage. Depending on the embodiment, this portion may be elongate
to a greater or to a lesser extent. It can also extend over a
distance sufficient to pass through the distributor and through the
cylinder block. The distribution coupling can then serve in
particular, at least in part by means of its bearings, to fasten
and/or to position the motor on the shaft segment. In which case,
the dual function of the coupling, namely the function of conveying
the feed and discharge fluids for the motor together with the
function of holding the motor, contributes to the compactness of
the hydraulic motor device.
[0029] A second object of the present invention is to design a
vehicle drive system including a mechanical transmission operated
by at least one main engine or motor, and that has a road mode in
which the drive torque is delivered mainly by the main engine, and
a work mode in which the drive torque is delivered by one or more
hydraulic motor devices, in addition to or as a replacement for the
main engine, the drive system remaining relatively simple.
[0030] This object is achieved by the fact that the vehicle drive
system includes a device as defined above, with its transmission
shaft being a portion of the mechanical transmission.
[0031] The invention can be well understood and its advantages
appear more clearly on reading the following detailed description
of embodiments shown by way of non-limiting example. The
description refers to the accompanying drawings, in which:
[0032] FIGS. 1A and 2 are axial section views of assistance
hydraulic motor devices of the invention, in first and second
embodiments of the invention;
[0033] FIG. 1B is a fragmentary axial section view of a variant of
the hydraulic motor device of FIG. 1A;
[0034] FIG. 3 is a radial section view of the motor through the
cylinder block in the second embodiment, on the plane of FIG. 2;
and
[0035] FIGS. 4 and 5 are diagrammatic views from above of vehicle
drive systems of the invention, in two different embodiments.
[0036] A first embodiment of a hydraulic motor device of the
invention is described below with reference to FIG. 1A.
[0037] The hydraulic motor device 500 of FIG. 1A comprises:
[0038] a mechanical transmission shaft 200 carrying coupling plates
at its ends, namely an inlet coupling plate 202 at one end, and an
outlet plate 204 at the other end, with a view to connecting it to
the other segments of the mechanical transmission of the vehicle;
and
[0039] a hydraulic motor 100 having a through passage 102 through
which the shaft 200 passes.
[0040] The hydraulic motor 100 comprises:
[0041] a cylinder block 10 in which radial pistons 12 are slidably
received;
[0042] a casing assembly in three portions 20, 30, 40 that are
fastened together by screws 22, in which casing assembly the first
portion 20 is a reaction cam mounted to rotate about the axis of
the shaft 200, and caused to move in rotation by the action of the
pistons 12 on its undulating inside cam surface 24; the second
portion 30 is a drive part that transfers the torque received by
the cam 20 to the shaft 200 via fluting 32; the third portion 40 is
a distribution casing;
[0043] a distribution coupling 50 mounted in stationary manner on
the chassis of the vehicle (not shown) via a flange portion 52, and
also having a sleeve portion 54 extending around the transmission
shaft 200;
[0044] a distributor 60 mounted to move in rotation about a
circularly symmetrical surface 56 of said sleeve portion 54,
synchronized in rotation with the distribution casing 40 by means
of spring screws 42, and therefore constrained in rotation with the
cam 20.
[0045] In the cylinder block, the cylinders extend radially
relative to the axis of rotation A and the cam surface 24 of the
reaction cam 20 is disposed around the cylinder block 10, and faces
towards the axis of rotation (A).
[0046] The distribution coupling 50 is connected via fluid feed and
fluid discharge orifices 58 to fluid feed and fluid discharge ducts
(not shown) of the vehicle.
[0047] The distributor 60 has distribution ducts 62 that are
connected respectively to the feed and to the discharge via the
ducts 55 in the distribution coupling 50, and via two grooves 51
arranged between the distribution coupling 50 and the distributor
60. The cylinder ducts 13 communicate with the distribution ducts
62 as the distributor moves in rotation so as to connect the
cylinders alternately to the feed and to the discharge.
[0048] The hydraulic motor 100 is held on the transmission shaft
200 by rotary bearings 103 and 104 that are disposed in the sleeve
portion 54 of the distribution coupling 50 around the shaft 200. To
this end, the sleeve portion co-operates with at least one rotary
support bearing for supporting the shaft segment in rotation
relative to the motor. It thus holds the shaft segment 200 in
position where it passes through the hydraulic motor. The ball
bearings 103 and 104 are spaced apart from each other and are
placed substantially on either side of the hydraulic motor, so as
to limit the radial forces to which they can be subjected. Thus, in
the embodiment shown, one of the bearings is situated in the
vicinity of the fluid feed and of the fluid discharge (orifices
58), and the other bearing is situated at the same level (along the
axis) as the cylinder block 10, inside the sleeve portion 54 that
extends in an internal passage 14 of the cylinder block 10.
[0049] Fluid is prevented from leaking between the distribution
coupling 50 and the transmission shaft 200 by an annular lip seal
57 disposed around the shaft 200, at the same end as the inlet
coupling plate 202. In this first embodiment (FIG. 1), the
distributor 60 is disposed about the sleeve portion 54. It is
situated on the same side of the cylinder block as the fluid feed
and discharge (orifices 58).
[0050] The distribution casing 40 is fastened to the cam 20 by the
screws 22, and is guided in rotation about the sleeve portion 54 by
a rotary support bearing 44.
[0051] Holding pieces 207 are screwed onto the ends of the shaft
200 for the purpose of holding the coupling plates 202, 204 axially
by means of washers 208.
[0052] In the embodiment of FIG. 1A, the drive torque delivered at
the outlet under the combined actions of the main engine and/or of
the hydraulic motor is transmitted by the outlet coupling plate 204
(on the left of FIG. 1A), the transmission shaft segment 200
receiving the torque coming from the main engine via the inlet
coupling plate 202.
[0053] In another embodiment, the drive torque can be delivered at
the outlet via the motor itself, at a connection portion situated
on the periphery of the motor (relative to its axis of rotation)
and adapted to transmit torque. This connection portion may be part
of any piece of the casing assembly, e.g. of the drive part 30, of
the reaction cam 20, or indeed of the distribution casing 40.
[0054] Operation of the hydraulic motor device is as follows:
[0055] When the hydraulic motor is in drive mode, said motor
receives and removes the hydraulic fluid under pressure via the
feed and discharge orifices 58. The fluid goes via the internal
ducts 55 in the distribution coupling 50, is exchanged with the
distributor 60 via the grooves 51, passes through the distributor
60 via the ducts 62, and is finally exchanged with the cylinders
via the cylinder ducts 13.
[0056] Due to the distributor 60 rotating relative to the cylinder
block 10, the cylinders are periodically partially filled and
emptied, and the fluid pressure varies periodically in the
cylinders. As a result, the pistons 12 of the motor are pressed
against the cam surface 24 in such a manner as to develop drive
torque, transmitted to the casing assembly. Since the casing
assembly is constrained to rotate with the shaft 200, said shaft is
driven in rotation by the hydraulic motor.
[0057] In reaction to the drive torque, the cylinder block 12
receives opposing torque of direction opposite to the direction of
the drive torque. The cylinder block is provided with fluting 16 in
its internal passage 14, which fluting meshes with corresponding
fluting 53 of the distribution coupling. The opposing torque is
thus transmitted to the distribution coupling that in turn
transmits those forces to the remainder of the vehicle via its
flange portion 52.
[0058] In order to cause the hydraulic motor to go from the drive
mode to the declutched mode, it suffices merely to interrupt
feeding the hydraulic motor with pressurized fluid. Under such
conditions, there is no longer any force urging the pistons
radially to engage them against the cam. The pistons therefore
remain in the position in which they are uncoupled from the cam,
and the hydraulic motor is thus at rest, the casing being free to
rotate in freewheeling manner about the cylinder block and about
the distribution coupling.
[0059] Conversely, in order to cause the hydraulic motor to go from
the declutched mode to the drive mode, it is necessary to go via an
acceleration phase during which the movement in rotation of the
casing assembly is accelerated, and which makes it possible to
synchronize the speeds and the relative positions of the casing
assembly of the shaft 200.
[0060] A variant of the hydraulic motor device shown in FIG. 1A is
described below with reference to FIG. 1B.
[0061] In the hydraulic motor device of FIG. 1B, the transmission
shaft segment and the drive part (that are referenced 200 and 30 in
FIG. 1A) are in the form of a single part 20030. Thus, the fluting
for connecting together the two parts is eliminated, as are the
manufacturing constraints and any problems of slack that might
arise in such a connection by fluting.
[0062] A second embodiment of a hydraulic motor device of the
invention is presented below with reference to FIGS. 2 and 3.
[0063] The hydraulic motor device 500B of FIGS. 2 and 3 has a
mechanical transmission shaft 200B and a hydraulic motor 100B.
[0064] The hydraulic motor 100B has a cylinder block 10B, a casing
assembly in three portions 20B, 30B, 40B, a distribution coupling
50B, and a distributor 60B.
[0065] Unless otherwise indicated, the various components of the
hydraulic motor 100B have relative positions and functions similar
to those of the corresponding portions of the hydraulic motor 100
of the first embodiment of the invention.
[0066] The main structural difference is due to the hydraulic fluid
distribution system being modified. The distribution coupling 150B
is no longer a single part 50 as it is in the motor 100, but rather
it is made up of three main parts 50B, 70B, 80B.
[0067] Thus, instead of having fluid exchange between the fluid
admission and fluid return orifices 58 and the distributor via a
single part 50 (the distribution coupling 50 of the motor 100), in
the motor 100B this fluid exchange takes place via the three parts
50B, 70B, 80B of the distribution coupling 150B.
[0068] The parts 70B and 80B are disposed on either side of the
cylinder block 10B. They are provided with respective internal
channels 75B and 85B, via which the hydraulic fluid flows.
[0069] The cylinder block 10B and the parts 70B and 80B are
fastened together by screws 152B that are disposed axially in
passages 17B, 77B, 87B provided in these parts.
[0070] Like the part 80B, the distributor is disposed on the side
of the cylinder block opposite from its side facing the fluid feed
and to the fluid discharge.
[0071] The advantage of this configuration is that the port plate
12 is situated opposite from the fluid feed and the fluid discharge
of the motor. Thus, the fluid pressure exerted on the port plate
tends advantageously to push the cylinder block towards the fluid
feed and the fluid discharge of the motor, i.e. towards the chassis
of the vehicle. The motor 100B thus tends to remain compact and to
limit its leaks.
[0072] The section view of FIG. 3 shows a section through the
hydraulic motor 100B at the cylinder block 10B. The cylinder block
has ten cylinders 18B. The following are arranged between the
cylinders:
[0073] eight passages 17B for the screws 152B; and
[0074] two passages 15B respectively for hydraulic fluid feed and
for hydraulic fluid discharge.
[0075] Thus, the distributor is connected to the fluid feed and to
the fluid discharge via ducts passing through the cylinder block
between the cylinders. Since the cylinder block is stationary, the
empty space between the cylinders is advantageously used to cause
hydraulic fluid to pass through the ducts, thereby avoiding
increasing the diameter of the cylinder block.
[0076] Two drive systems (1001, 1002) for a vehicle (not shown),
each of which systems includes a hydraulic motor device 500 of the
invention, are presented below with reference to FIGS. 4 and 5.
[0077] These systems drive wheels 630 by transmitting the power
delivered by an internal combustion main engine 400. Each of these
systems comprises a mechanical main transmission 800 and a
hydraulic auxiliary transmission. Naturally, the vehicle can have
other wheels and other additional transmission members.
[0078] The mechanical main transmission 800 comprises a mechanical
gearbox 810, a main transmission shaft 820, and an axle 830.
[0079] Said mechanical main transmission 800 transmits the drive
torque output from the motor 400 to the wheels 630 in the following
manner:
[0080] The motor 400 is coupled to the gearbox 810, to which it
communicates drive torque. The gearbox 810 delivers said drive
torque on its outlet shaft 812. This shaft 812 is connected to a
first end 825 of a main transmission shaft 820 that it drives in
rotation. The main transmission shaft 820 is connected at its other
end 826 to an axle 830. The axle 830 comprises a power divider 832
and two half-shafts 834.
[0081] The power divider 832 that includes a differential, receives
the drive torque from the main transmission shaft 820 and transmits
it to the two half-shafts 834. Said half-shafts are coupled to the
wheels 630 to which they communicate the drive torque.
[0082] In addition to the mechanical main transmission, the drive
systems 1001 and 1002 also include a hydraulic auxiliary
transmission.
[0083] This hydraulic auxiliary transmission comprises:
[0084] at least one assistance hydraulic motor device 500;
[0085] a hydraulic pump;
[0086] a secondary transmission shaft for transmitting mechanical
power to the hydraulic pump for the purpose of driving said pump;
and
[0087] a hydraulic circuit connecting the hydraulic pump to the
feed and to the discharge of the hydraulic motor device(s) 500 for
the purpose of feeding said device(s) with hydraulic fluid under
pressure.
[0088] In the hydraulic auxiliary power transmission, the hydraulic
motor device(s) (500) drive(s) directly rotary elements of the
mechanical transmission, namely a segment 821 of the main
transmission shaft 820 in the drive system 1001 (FIG. 4), or
transmission half-shafts 834 in the drive system 1002 (FIG. 5).
[0089] FIG. 4 shows a drive system 1001 including a hydraulic motor
device 500 of the invention. This drive system 1001 includes a
hydraulic auxiliary transmission 900 that is presented below.
[0090] As indicated above, the gearbox 810 has an outlet shaft 812
serving for the mechanical main transmission 800. In addition, a
secondary outlet shaft 910 is also connected to said gearbox 810
and is thus driven in rotation. The secondary shaft 910 is
connected to a hydraulic pump 920 that it, in turn, drives. The
pump 920 is connected to the hydraulic motor device 500 via a
hydraulic circuit comprising a feed circuit 922 and a discharge
circuit 924 for the hydraulic motor device 500. By means of these
circuits, the pump 920 feeds the hydraulic motor 500 with fluid
under pressure.
[0091] Thus, a fraction of the drive power transmitted by the
engine 400 to the gearbox 810 is diverted to the hydraulic pump 920
via the shaft 910. The pump 920 converts the rotary mechanical
energy into fluid energy in the form of a fluid pressure. The fluid
under pressure drives the hydraulic motor device 500 in rotation,
the hydraulic motor device then in turn converting this drive power
back into mechanical power by driving in rotation a shaft segment
821 on which it is placed.
[0092] This segment 821 is a central segment of a string of three
segments 821 connected together in succession via flanges 840 and
constituting the main shaft 820 of the mechanical main
transmission.
[0093] Advantageously, the extra mechanical power delivered by the
hydraulic motor device 500 can either replace or supplement the
power transmitted directly by the motor 400 to the outlet shaft 812
of the gearbox 810. This extra power delivered by the hydraulic
transmission can be used, in particular, when the shaft 820 is
rotating at low rotation speeds at which the performance delivered
by the engine 400 in association with the gearbox 810 is not
sufficient.
[0094] Operation of the hydraulic transmission 900 is controlled by
an electronic control unit (ECU) 460. Said unit is connected to the
hydraulic motor device 500, to the pump 920, and to the ADC data
bus of the vehicle via data interchange links 437, and makes it
possible to monitor and control operation of the hydraulic
transmission 900.
[0095] The vehicle drive system 1002 shown in FIG. 5 also includes
a hydraulic auxiliary transmission analogous to the auxiliary
transmission of FIG. 4. Since the general operating principle of a
hydraulic auxiliary transmission, in which a fraction of the
mechanical power is directed towards a pump for actuating an
assistance hydraulic motor, is known (and is also indicated with
reference to FIG. 4), in FIG. 5 only the hydraulic motor devices
500 of the hydraulic auxiliary transmission are shown.
[0096] In the drive system 1002 of FIG. 5, the main transmission
shaft 820 has a single segment only.
[0097] In this drive system, the extra drive supplied by the
hydraulic transmission is delivered to the half-shafts 834 rather
than to the main transmission shaft 820. Each of the half-shafts
has a hydraulic motor device as described above.
[0098] Thus, in this drive system, the transmission shaft segments
incorporated into the hydraulic motor devices 500 are secondary
transmission shafts 834, connected to a main transmission shaft 820
of the mechanical transmission 800.
[0099] Advantageously, the drive system 1002 makes it possible to
exert anti-spin action to prevent wheel spin that can occur when an
axle 830 including a differential is used on slippery ground. To
this end, the drive system makes it possible to monitor or to
control the speeds of rotation of the motors of the two hydraulic
motor devices 500 by control means that are in particular hydraulic
control means, thereby making it possible to guarantee that drive
torque is exerted on at least one of the two wheels, even if the
other one is spinning.
* * * * *