FR2877415A1 - Automatic transmission for motor vehicle, has valve body that distributes oil to double clutch and heat exchanger, and sealing unit that isolates valve body from lower cavity during inactive condition of transmission - Google Patents

Abstract

The transmission has a lower oil reception cavity (50) and passages (61-68) with a pump (30) supplying the passages from the cavity. A valve body (20) is supplied by the passages and distributes the oil to a double clutch (10) and a heat exchanger (40). A sealing unit has check valves (71, 72), a valve (73) and lateral orifices (81, 82) and isolates hydraulically the body from the cavity during an inactive condition of the transmission.

Description

Automatic gearbox with oil level under control.

  The invention relates to automatic transmissions of motor vehicles.

  The compactness of current engine sets is a necessity that also applies to automatic transmissions.

  There is therefore a search for optimizing the bulk volumes of the gearboxes, and the appearance of constraints resulting in performance and also in reliability.

  Thus, the compactness of the current automatic gearboxes has reduced the level of oil available in the box, which nevertheless must be present in sufficient volume for the lubrication and actuation of the various organs of the box.

  To this first constraint is added a second difficulty, which is to preserve the operation of the clutches present in the box, especially during a cold start (-30, for example). Indeed, the clutches are typically located in the direct vicinity of a bottom cavity of the box, and are therefore likely to bathe at least partially in the oil rendered viscous by low temperatures. The clutch is then braked in its rotation in a way that can go so far as to make starting impossible.

  Among the automatic gearboxes proposed so far, this difficulty has sometimes been avoided, but with limited success. For example, the principle of robotic systems installed for actuation functions in certain automatic gearboxes is known. These robotic systems are sealed in themselves, containing a very small amount of oil because poorly lubricated.

  Such systems solve the problem of excess oil in the box, using a particular technology, robotization. However, this technology has a significant cost and sometimes inadequate operation.

  It has also been proposed (EF '589 507) to equip an automatic gearbox with an oil level measuring system. This certainly avoids excessive accidental oil, for example due to poor filling of the box, but does not solve the problem of excessive oil permanent or clean design of the box.

  The object of the invention is to provide an automatic gearbox of a motor vehicle with a sufficient amount of oil but whose oil level at rest and in particular cold does not hinder the setting in motion of certain organs as the clutch bodies.

  This object is achieved, according to the invention, by means of an automatic gearbox of a motor vehicle, comprising a lower oil receiving cavity, a hydraulic circuit provided with a pump supplying this circuit from the lower receiving cavity of the motor vehicle. oil, and a hydraulic distributor powered by said hydraulic circuit, which hydraulic distributor distributes the oil to different bodies of the gearbox. The gearbox is provided with sealing means which are able to hydraulically isolate the hydraulic distributor from the lower oil receiving cavity of the gearbox when the transmission is idle.

  Thus, hydraulically part of the gearbox is separated hydraulically which may empty into the lower cavity of the box at rest.

  The lower cavity of the box and the organs driven at startup, including the clutch, are thus protected from the appearance of excess oil.

  In a particular aspect, the box comprises a heat exchanger and at least one oil line connecting the hydraulic distributor to the heat exchanger and the sealing means are placed so as to isolate two parts of the gearbox of which the one comprises the lower cavity and the other includes both the hydraulic distributor and the heat exchanger.

  The insulated portion which includes the lower cavity advantageously also includes the clutch module.

  Advantageously, the sealing means comprise means for closing off at least one oil line.

  The sealing means is advantageously a valve provided with a return means LS towards its closed position.

  The actuating means of the valve are for example in opposition to an oil pressure present in the pipe so that these actuating means cause a valve to close position in the absence of pressure in the pipe.

  When a pipe has a high point, the fluidic isolation means comprise an orifice in this pipe at this high point, so as to defuse any siphon constituted by the pipe.

  The fluidic isolation means comprise, for example, an activatable / deactivatable shutter means of said orifice of the pipe.

  When the box has a plurality of pipes each having a high point, the closure means of the orifice of each of these pipes are advantageously constituted by the same shutter valve of multi-channel type.

  The activable / deactivatable means of closing the orifice is advantageously a means equipped with a return spring towards an open position of the orifice.

  Other features, objects and advantages of the invention will appear on reading the detailed description which follows of a non-limiting embodiment of the invention. The description is made with reference to the single appended figure, which is a sectional view of an automatic gearbox according to the invention.

  This box comprises in particular a clutch 10 of the double type and multidiscs provided with its control system. This control system comprises three main elements of the gearbox, namely a hydraulic distributor 20, a referenced pump 30 supply and pressurization of the hydraulic distributor 20, and a heat exchanger 40 placed in hydraulic connection between the distributor 20 and the double clutch 10. These various elements are placed above a cavity 50 constituting the bottom of the automatic transmission.

  The clutch 10 is said to be wet because it is impregnated with the oil such that it also supplies the other elements of the gearbox.

  The hydraulic distributor 20, supplied by the pump 30, in turn supplies the other gearbox components, and in particular the heat exchanger 40.

  More specifically, the hydraulic distributor 20 here distributes the oil supply to different members. It feeds, on the one hand, unrepresented clutch actuating members, lubrication members of the various gearbox elements, and finally the heat exchanger 40. The double clutch 10, the hydraulic distributor 20, the pump 30 and the exchanger 40, are interconnected by pipes which will be listed below under the references 61, 62,

  ., 68 ... DTD: The oil delivered under pressure by the pump 30 has a pressure regulated by the pump to a predefined value and called line pressure.

  It turns out that at rest the hydraulic distributor 20 and the exchanger 40 are two volumes of oil that are likely to drain by gravitation or siphoning in the lower cavity 50 of the gearbox.

  This draining proves to be the source of an increase in the level of oil at the bottom of the box, and in particular an exceeding of the tolerable oil level for the clutch torque 10.

  For this purpose, the present device comprises arrangements removing the phenomenon thus noted.

  For this, we adopt here means that hydraulically isolate these different elements.

  These means isolate two sets from each other. The first set includes in particular the cavity 50 of the bottom of the box. The second set includes in particular the hydraulic distributor 20 and the exchanger 40.

  The first set corresponds to a lower portion of the gearbox, the second set corresponds to an upper portion of the gearbox. In other words, it is a matter of making a separation between two sets, one of which is capable of being emptied by gravitation into the other.

  The clutch 10 is then considered as belonging to the lower portion of the gearbox, that is to say to the assembly including the cavity 50 when the hydraulic separation means are in use.

  Three pipes 66, 67 and 68 leave the hydraulic distributor 20 to finally connect the clutch 10.

  Only two pipes 67 and 68 of these three pipes 66, 67 and 68 connect the clutch 10 directly.

  The remaining pipe 66 first connects the heat exchanger 40, where the oil thus transported undergoes cooling, then extends again to the clutch 10.

  Line 66 merges with an end portion 67b of direct line 67 at the clutch inlet.

  The lines 66, 67 and 68 are lubrication lines. More specifically, the lines 66 and 67 lubricate the clutch 10 on two respective lanes, while the line 68 is a lube line of a bearing portion of the clutch.

  These pipes are extracted from the distributor 20 by a branch line greater than the latter, but then describe a path which is mainly lower than this starting branch. The pipes 66, 67 and 68 therefore have a path that is predominantly downward.

  A first arrangement prevents the hydraulic distributor 20 and the exchanger 40 from being emptied through the clutch 10 via these three lines 66, 67 and 68.

  Two valves 71 and 72 equip the pipes 67 and 68 for this purpose.

  The valve 71 is placed on the pipe 67 and the valve 72 is placed on the pipe 68.

  The valve 71 is here in place on the end portion 67b of the pipe 67. By this arrangement, the valve 71 blocks the flow of oil flowing through the pipe 67 and the flow of oil flowing through the pipe 66. It is thus taking advantage of the fact that the pipes 66 and 67 meet upstream of the portion 67b to block the flow of these two pipes using the single valve 71.

  Each of the valves 71 and 72 is a one-way type valve with two possible positions.

  One or the other of the two possible positions of each valve is adopted as a function of the pressure present on the pipe considered, as compared to the force of a return spring equipping the valve.

  The force of the return spring indeed places the valve in blocking position of the flow. This position appears when the spring is free to extend, ie when it is not opposed by any oil pressure. Thus, when the line drops, especially when the vehicle is stopped and the pump 20 stops, the valve spring relaxes and the valve then blocks any oil down the line considered 67b or 68.

  When the line pressure is on the contrary present in the portion of pipe considered, the force of the return spring of the valve is insufficient to maintain it in the blocking position of the flow. The valve is then opened under the effect of the oil pressure and it appropriately allows the circulation of oil.

  In other words, when the oil pressure drops, especially during the stopping of the vehicle, each valve 71 and 72 closes its respective pipe portion and prohibits any emptying of the different volumes, namely the hydraulic distributor 20 and the exchanger 40 located upstream of these valves 71 and 72.

  The other pipes in the presence are in particular the pipes 61, 62, 63 which connect the pump 30 to the hydraulic distributor 20. The appended figure also has two actuating pipes 64 and 65 which connect the hydraulic distributor 20 to the clutch torque 10.

  The three ducts 61, 62, 63 extend parallel to each other and each form a direct connection between the pump and the hydraulic distributor 20.

  The ducts 61, 62 and 63 supply the hydraulic distributor 20 with oil drawn by the pump 30 into the cavity 50 of the can bottom.

  1l0 The two parallel pipes 64 and 65 connect the hydraulic distributor 20 to the clutch 10.

  The oil pressure that these two pipes 64 and 65 transmit to the clutch 10 is used by the latter as mechanical energy for the actuation of its various unrepresented moving parts.

  Each of the pipes 64 and 65 is mechanically associated with a different moving part of the clutch 10, these moving parts being capable of independent actuations.

  The lines 64 and 65 are called even pipe and odd conduct with reference to these respective even and odd moving parts which constitute the double clutch box.

  The pipes 61, 62 and 63, and the pipes 64 and 65 have a common appearance. Each of these pipes has a path passing through a high point.

  Indeed each of these pipes has a U-shaped returned, the U-shape being cited for purely illustrative purposes. The base of this U-shape thus forms a substantially high part of the path described by the pipe.

  In other words, each of these conduits 61, 62, 63, 64 and 65 passes through a high point in its current part.

  Therefore each of these pipes is likely to empty the hydraulic distributor 20 in the bottom cavity 50 by siphon effect.

  This siphon effect proves indeed to take place despite the presence of the pump 30 at the outlet of the pipes 61, 62 and 63 and despite the presence of the clutch 10 at the outlet of the pipes 64 and 65.

  The three ducts 61, 62 and 63 are here each equipped with a lateral orifice 81, 82, 83 at their high point as a means of defusing this siphon effect.

  A common valve 73 equips the three pipes, in the form of a slide which slides between on the one hand a closed position on: the three pipes (three channels), and on the other hand an open position on the three pipes ( three ways).

  The closed position of the drawer closes the lateral orifice 81, 82, 83 of each of the ducts 61, 62 and 63. The open position of the drawer uncovers the orifices 81, 82, 83 of each of the ducts 61, 62 and 63.

  When vented, the lines 61, 62 and 63 are defused from any siphon effect. The valve 73 is equipped with a return spring acting in the direction of an opening of the valve, that is to say a venting of the pipes.

  The spring, not shown in the figure, is in opposition to the line pressure.

  Therefore, the spring opens the valve 73 only in the absence of line pressure, that is to say when stopping the vehicle. By this opening of the valve at a standstill, the siphon effect can not take place in the pipes 61, 62 and 63, preventing the emptying of the hydraulic distributor 20.

  The lines 64 and 65 connecting the hydraulic distributor 20 to the clutch 10 are also each provided with an orifice 84, 85 for venting at their respective high points.

  However, this venting is permanent in the case of these pipes.

  The venting orifice 84, 85 of each of the pipes 64 and 65, however, has a sufficiently limited opening section to prevent excessive loss of pressure in operation. This permanent venting aims at a function additional to that of the defusing of the siphon considered.

  Indeed, it seeks to cause an immediate loss of pressure of an end portion of each pipe 64, 65 which is downstream of the high point when the oil flow stops in the pipe. Such a stop can take place under the control of the hydraulic distributor 20 or at the stop of the vehicle. By this immediate loss of pressure, the clutch is actuated with a better precision. Indeed, the oil used for actuation finds its zero pressure at each end of actuation accurately and without any delay.

  This permanent venting also has the advantage of stabilizing the pressure regulation in the clutch chambers and allows for faster emptying.

Claims (10)

  1-Automatic gearbox of a motor vehicle, comprising a lower cavity (50) for receiving oil, a hydraulic circuit (61,.   , 68) provided with a pump (30) supplying this circuit from the lower oil receiving cavity (50), and a hydraulic distributor (20) fed by said hydraulic circuit (61, ..., 68), which hydraulic distributor (20) distributes the oil to various transmission members (10, 40), the gearbox being characterized in that it is provided with sealing means (71, 72, 73, 81, 82) which are adapted to hydraulically isolate the hydraulic distributor (20) from the lower oil receiving cavity (50) during a resting of the gearbox ... CLMF:  2-gearbox according to claim 1, characterized in that it comprises a heat exchanger (40) and at least one oil line (66) connecting the hydraulic distributor (20) to the heat exchanger (40), characterized in that the sealing means are arranged to isolate two parts of the gearbox, one of which comprises the lower cavity (50) and the other comprises both the hydraulic distributor (20) and the heat exchanger (40).   3-gearbox according to claim 2, characterized in that it comprises a clutch module (10) and in that the insulated portion comprising the lower cavity (50) also comprises the clutch module (10).   4-gearbox according to claim 1, characterized in that the sealing means comprise a closure means (71, 72) of at least one oil pipe.   5-gearbox according to claim 4, characterized in that the closure means (71, 72) is a valve provided with a means of return to its shutter position.   6-gearbox according to claim 5, characterized in that the actuating means of the valve (71, 72) are in opposition to the line pressure of the circuit so that these actuating means cause a position to be adopted. valve shut-off in the absence of line pressure.   7-Gearbox according to any one of the preceding claims, characterized in that it comprises at least one pipe (64, 65) having a high point and in that fluidic isolation means (61, 62, 63 , 64, 65) comprise an orifice (81, 82, 83, 84, 85) in this pipe at this high point, so as to defuse any siphon constituted by the pipe.   8-gearbox according to the preceding claim, 0 characterized in that the fluidic isolation means comprise an activatable / deactivatable type closure means (73) of said orifice (81, 82, 83) of the pipe (61, 62, 63).   9-gearbox according to claim 8, characterized in that it has a plurality of ducts (61, 62, 63) each having a high point, the closing means (73) of the orifice (81, 82 , 83) of each of these pipes (61, 62, 63) being constituted by the same valve (73) shutter type multipath.   10-Box of claim 9, activatable / deactivable equipped with a spring (81, 82, 83).   Speeds according to claim 8 or characterized in that the closure means (73) of the orifice (81, 82, 83) is biased towards a position of opening of the orifice