KR20070057833A - Continuously variable transmission provided with a set of hydraulic pumps - Google Patents

Abstract

Continuously variable transmission (1) for transmitting a driving force of an engine (E) to a load (L) to be driven, provided with a set of hydraulic pumps (PM, PE) for realising a pressurised supply of hydraulic medium, at least for the actuation of the transmission (1) within a range of transmission ratios and of at least one auxiliary hydraulic user (U1, U2) of the transmission (1), such as a coupling means (C), which set of hydraulic pumps (PM, PE) comprises a mechanically driven pump (PM), which is driveable by the said engine (E) and is capable of supplying hydraulic medium from a reservoir (10) for hydraulic medium to a main hydraulic line (11) of the transmission (1), and an electrically driven pump (PE), which is driveable by an electric motor independently from the said engine (E) and is arranged in series with the mechanically driven pump (PM), capable of drawing hydraulic medium from the main hydraulic line (11).

Description

Continuous gearbox with hydraulic pump set {CONTINUOUSLY VARIABLE TRANSMISSION PROVIDED WITH A SET OF HYDRAULIC PUMPS}

The present invention relates to a continuously variable transmission as defined in the preamble of claim 1.

Such continuously variable transmissions are mostly known and are described, for example, in European patent publication EP-A-0 764 799 in the name of the applicant. Known continuously variable transmissions, which may be one of several known forms, provide a transmission ratio that can be controlled to any value within the range of the transmission ratio covered by the transmission through proper operation of the transmission. This operation of the transmission generally requires a relatively large flow of hydraulic medium at relatively high pressure levels. Although these high pressure levels can be implemented and controlled inherently without particular difficulties in known transmissions, significant modifications to the layout and / or components of the hydraulic system of the transmission are not intended for dynamic operation of the transmission, i.e. It is a particularly large flow of hydraulic medium required for the change. This variant is more urgent where the hydraulic pump of the transmission is mechanical, ie directly driven by the engine.

Thus, in the above-mentioned European patent publication, this variant is provided by providing a transmission having not only a mechanical drive pump but also an electric drive pump driven, for example, via an electric motor powered by a battery of a vehicle to which the transmission is applied. It is proposed to reduce, wherein the electric drive pump can be operated on demand. In this publication, the electric drive pump is arranged and operated in parallel with the mechanical drive pump, whereby the mechanical drive pump is sufficient for steady state operation of the entire transmission, ie maintains a constant gear ratio and is pressurized to at least one auxiliary user. While providing a sufficient supply of medium, it provides a basic flow of pressurized hydraulic medium, whereby the electric drive pump provides an auxiliary flow of pressurized inlet medium which is additionally required for actuation of the transmission during the dynamic operation of the transmission. .

Although this known configuration performs fairly well, some disadvantages also hinder the widespread application of this configuration as a generally applicable principle. The main disadvantage is that the configuration shows relatively low efficiency gains for the more conventional transmissions comprising one or more mechanical drive pumps, while the extra cost and effort for the integration of the electric drive pumps is quite significant. In addition, in this particular application for the available type of electric drive pump, this pump appears to significantly and undesirably increase the generated noise level during transmission operation.

It is therefore an object of the present invention to provide an improvement of the known continuously variable transmission in which the above disadvantages are at least reduced within the limitations of the preferably efficient combination of mechanical drive pumps and electric drive pumps.

According to the invention, the object of the invention is realized when the characteristics of the features of claim 1 are applied to a continuously variable transmission known from the preamble of the claims.

In such a transmission, the electric drive pump is integrated in series with the mechanical drive pump rather than in an integrator. This surprisingly and in spite of the increasing requirements, even if the electric drive pumps are not generally operated continuously, i.e. not only during the dynamic operation of the transmission, but also during the substantially static operation of the transmission, the preferred hydraulic configuration is for a number of reasons Is achieved. In the first position, the electric drive pump is supplied, ie aspirated, by the hydraulic medium which has already been pressurized to the desired level by the mechanical drive pump. Among other things, this preferably has the effect that the pressure difference, ie the pressure difference between the inside and outside of the pump, is reduced for the two pumps. In addition, only a portion of the total flow of hydraulic medium produced during operation of the transmission is pressurized by the electric drive pump to the highest pressure level in the system, ie to the pressure level required for operation of the transmission. This flow portion is also continuously and precisely adjusted as practically necessary by proper activation of the electric drive pump. The remainder of the total flow of hydraulic medium is pressurized by the mechanical drive pump to only relatively low pressure levels required by the auxiliary user (s). In this way, an increase in pumping efficiency and a reduction in noise level can be realized.

In the most critically loaded electric drive pumps, in many cases this effect of noise reduction is significant, although the occurrence of cavitation, ie the formation of bubble droplets and subsequent bursts at the pump inlet side, is not completely eliminated. Will be supported through reduced features. In addition, the shape of the mechanical drive pump can be fully optimized for pumping large flows of hydraulic medium, and finally one pressure control valve will be omitted for the most well known layout of the hydraulic system.

As an example of the advantages, the pressure level typically required for actuation of the transmission may be up to 60 bar or sometimes even 80 bar, while the pressure level typically required by commonly applied auxiliary users is approximately 10 Note that it can even be a bar. The auxiliary hydraulic user may comprise clutch or coupling means of the transmission for selectively connecting the engine to the load, lubrication means for lubrication of rotating transmission parts and so-called solenoid valves for controlled activation of other valves of the transmission. It is also noted.

The invention will be explained in more detail by the figures.

1 is a schematic diagram of a prior art and improved continuously variable transmission.

2 is a view showing a basic hydraulic configuration of the original transmission according to the present invention.

3 to 5 show different embodiments in the first principle completion of a basic hydraulic configuration according to the invention.

Figures 6 to 8 show different embodiments in the second principle completion of the basic arrangement according to the invention.

In some cases, like reference numerals in the drawings refer to corresponding technical functions or elements. The dashed line represents the pressure control line for control, ie deflection of the various hydraulic valves, while the thick line indicates the hydraulic line, ie the passageway for the hydraulic medium.

1 shows the operation and coupling means, the lubrication means of the mechanical system TM and the mechanical system TM for realizing and changing the physical transmission ratio between the input shaft 2 and the output shaft 3 of the transmission 1. And / or a continuously variable transmission (1) comprising a hydraulic system (TH) for the operation of the transmission (1) comprising the control of any auxiliary hydraulic users (U1, U2) of the transmission (1), such as a solenoid valve in some cases. ). The transmission 1 is integrated to change the speed and torque transmission ratio between the engine E and the load L, for example, within a continuous range of possible transmission ratios between the engine E and the load L in a vehicle. Can be.

In this particular illustration, the mechanical system TM of the known transmission 1 comprises an endless elastic belt 4 which is wrapped around two pulleys 5 and 6, so that each pulley 1 Is connected to the input shaft 2 or to the output or second shaft 3. The belt 4 is connected to the pressure chamber 7 or 8 of the piston and cylinder assembly associated with each pulley 5, 6, that is to say the first pressure chamber associated with the pulley 5 connected to the input shaft 2. 7) or frictionally with the pulley discs of the respective pulleys 5, 6 by means of clamping forces generated by the hydraulic pressure applied to the so-called second pressure chamber 8 associated with the pulley 6 connected to the input shaft 3; Is engaged.

The hydraulic system TH of the known transmission 1 comprises a mechanical drive main pump PM and an electric drive auxiliary pump PE, which, in particular, can be adapted to the demand and to the variable range, in particular the transmission 1. Mechanical system TM can be activated during dynamic operation. On the other hand, the mechanical drive pump PM is driven directly and continuously by the engine, so that the flow of the medium supplied through it depends on the speed of the engine. The two pumps PM, PE can be arranged in parallel and supply the flow of pressurized hydraulic medium to the first or main hydraulic line 11, whereby the medium is a reservoir for the hydraulic medium of the transmission 1. 10). The one-way valve 17 is provided between this main line 11 and the electric drive pump PE to prevent medium loss due to leakage through this pump PE when not in operation.

The hydraulic pressure P _LINE in the main line 11 is controlled by the line pressure control valve 12 to the level required in the second pressure chamber 8, the pressure level being referred to as the second pressure P _SEC . Lose. Thereby, the line pressure control valve 12 has generally known valve deflection means 12a, 12b, 12c, i.e. a pressure feedback line 12a, a mechanical spring 12b, and a control pressure line 12c, To allow for controlled flow of the hydraulic medium from the main line 11 to the auxiliary hydraulic line 15, i.e. the remainder of the flow supplied by the mechanical drive pump PM and possibly also by the electric drive pump PE. Used to discharge. In addition, an additional hydraulic line 13 diverges from the main line 11 via a flow control valve 14 which is used to set the additional line 13 to the required level in the first pressure chamber 7. Such pressure level is referred to as the first pressure P _PRI . Thus, the flow control valve 14 has generally known valve deflection means 14a and 14b, namely a pressure control line 14a and a mechanical spring 14b, the main line 11 and the additional line 13. to between the first pressure (P _PRI) further in order to increase or main line 13 and the reservoir 10 between lowering the first pressure (P _PRI) it is used for the controlled flow of the hydraulic medium. In such a system, the line pressure (P _LINE ) or the second pressure (P _SEC ) and the first pressure (P _PRI ) are generally controlled pressure levels in the pressure control lines (12a and 14a) by means of an additional valve actuated to the solenoid. By determining this, it is actively controlled to the required level.

The known hydraulic system TH comprises at least in some cases lubrication means for selectively connecting the engine E to the load L, ie for lubricating the rotating transmission component, for example the drive belt 4. At the so-called auxiliary pressure P _AUX required for the actuation of the auxiliary hydraulic users U1, U2 of the transmission 1, such as clutches or coupling means generally integrated in the other valves, for example the transmission 1. The above-mentioned of the transmission 1 and the second or auxiliary pressure control valve 16 used to set the pressure level in the auxiliary hydraulic line 15, for example to enable idling of the engine E. It further comprises the aforementioned solenoid operated valve for the controlled activation of the valves 12, 14, 16. In general, however, these solenoid valves are supplied via hydraulic medium from the (higher) pressure portion of the hydraulic system TH.

The auxiliary pressure P _AUX may have a constant value such that the valve biasing means of the auxiliary pressure control valve 16 includes only the pressure feedback line 16a and the mechanical spring 16b. Any excess flow received from line 11 by auxiliary hydraulic line 15 is discharged by auxiliary pressure control valve 16, and in this example is supplied directly to reservoir 10.

In particular, a considerable flow of hydraulic medium is required for the operation of the transmission 1 during the dynamic state in which the volumes of the above-mentioned pressure chambers 7 and 8 cause a change in the transmission ratio, which flow is pumped (PM, PE). Is supplied by An undesirable feature of the known hydraulic system TH is that the total flow of hydraulic medium supplied by the pump results in the highest system pressure, ie the line pressure P _LINE , which is the pressure of the hydraulic system TH. In this particular configuration corresponds to the second pressure P _SEC . Still, a substantial portion of the flow supplied by the mechanical drive pump PM is subsidiary, which is typically operated at a pressure level much lower than that required for actuation of the transmission 1, ie at an auxiliary pressure P _AUX . It is intended for the actuation of the users U1, U2. Thus, when the latter half of the flow is depressurized from the line pressure P _LINE to the auxiliary pressure P _AUX , considerable mechanical pumping force is still wasted.

2 schematically shows the basic structure of a new hydraulic system TH according to the invention, which system can preferably be used in combination with a mechanical continuously variable transmission system TM of a type known in principle. Furthermore, as further shown in connection with FIGS. 3 to 10, the arrangement according to the invention can in principle be used irrespective of the specific arrangement of the actuating circuit component 20 of the hydraulic system TH.

FIG. 2 shows that the electric drive pump PE is provided in series and in particular downstream of the mechanical drive pump PE, whereby the hydraulic medium is sucked from the main line 11 and the operation of the transmission 1 is thus avoided. To the hydraulic actuating circuit 20. In addition, as with the electric drive pump PE, the auxiliary hydraulic users U1 and U2 of the transmission 1 are connected to the main line 11 from which the hydraulic medium stops the operation of the auxiliary hydraulic users U1 and U2. To be aspirated. In the basic construction of this new hydraulic system TH, the hydraulic actuation circuit 20 can be regarded as the user U3 as an additional auxiliary user.

By providing an electric drive pump PE between the main line 11 and the hydraulic actuation circuit 20, the pressure level in the main line 11 is controlled by the auxiliary pressure regulating valve 16 with a relatively low auxiliary pressure P _AUX . In the configuration, the auxiliary pressure regulating valve is set at a constant level determined by the respective valve deflection means 16a, 16b. The activation of the electric drive pump PE is preferably controlled according to the actual line pressure level required for proper activation of the measured line pressure P _LINE and the mechanical system part TM of the transmission, for example. Preferably, the difference between them is minimized, but at least the actual line pressure P _LINE can be set to a level equal to or higher than the required pressure level. The basic configuration of the hydraulic system TH of the transmission according to the invention is in harmony with the advantages described above.

3 to 5 show different embodiments of the first main embodiment of the basic hydraulic structure according to the invention based on the known arrangement of the hydraulic system TH shown in FIG. 1, because in this embodiment the line pressure ( P _LINE ) acts as the secondary pressure P _SEC , since the primary pressure P _PRI is subsequently derived from the secondary pressure P _SEC . For this reason, in the embodiment of FIGS. 3 to 5, the hydraulic actuating circuit 20 flows with the first hydraulic line 21 provided with the hydraulic medium at the line pressure P _LINE level by the electric drive pump PE. A second hydraulic line 22 branching from the first line 21 via the regulating valve 23, which is similar in structure and function to the known flow regulating valve 14 described above. It may be used to set the pressure in the second line 22 to the first pressure (P _PRI ) level.

Usually, it is another requirement of this layout of the hydraulic system TH that the line pressure P _LINE can be raised and / or lowered on demand within a more preferably wider range of possible values, which is a hydraulic system. In the known layout of TH, it is realized using the line pressure regulating valve 12. However, in the embodiment of FIG. 3, a similar hydraulic layout is selected, where the line pressure P _LINE can be raised by the regulated actuation of the electric drive pump PE and on the line pressure regulating valve 24. Valve 24 may be similar in structure and function to the known line pressure regulating valve 12 described above. In this example, the line pressure regulating valve 24 allows a controlled flow of the hydraulic medium back from the first line 21 into the main line 11, whereby the line pressure P _{LINE is} connected to the accessory pressure P _AUX. Can be lowered down to the level of).

, As shown in the figure by a broken line 18, by a direct connection to the reservoir 10, a line pressure control valve 24, the line pressure even lower minimum level for the (P _LINE) it would of course be possible. Another important advantage of this latter layout of the hydraulic system TH compared to the known layout shown in FIG. 1 is that the first and second pressures P _PRI , P _SEC are at an accessory pressure P _AUX level. It can be controlled to the following levels. This allows the efficiency of the transmission 1 to be further improved within special operating conditions, for example when no engine power is delivered or very little engine power is delivered.

Alternatively, as shown in the embodiment of FIG. 4, a line pressure regulating valve 24 may be unnecessary, thus actively drawing a reversible type pump, ie hydraulic medium from the main line 11. And provide it to the hydraulic actuation circuit 20 and-at least passively but preferably active and controllable-to allow the hydraulic medium to flow back from the hydraulic actuation circuit 20 into the main line 11. By applying an electrically driven reversible pump PE _REV , the line pressure P _LINE is lowered by said controlled activation of the electric drive pump PE itself.

Finally, in a third embodiment of the first principle completeness of the basic hydraulic configuration according to the invention shown in FIG. 5, at least when the electric drive pump PE is stopped, it is also relatively small and from the hydraulic actuation circuit 20. By incorporating a well-defined leak 25 of, the line pressure P _LINE can be reduced while allowing the hydraulic medium to flow into the reservoir 10, for example by so-called flow restriction means 25. It is shown that it can. This layout, of course, constitutes a relatively inexpensive means 25 compared to the reversible pump means PE _REV and the line pressure control valve means 24.

6-8 illustrate different embodiments of the second principle assembly of the basic hydraulic configuration according to the invention, wherein the assembly of the invention is essentially a hydraulic circuit known from EP-A-0 210 663. Based on the layout of (TH). In this assembly the line pressure P _LINE is realized as a separate pressure level in the hydraulic actuation circuit 20 and the first pressure P _PRI and the second pressure P _SEC are subsequently derived from the pressure level. do. To this end, the hydraulic actuation circuit 20 comprises a first hydraulic line 21 with hydraulic medium at the line pressure P _LINE level generated and controlled by the proper activation of the electric drive pump PE. Thus, in this principle collector tube, the pressure control valve can be omitted in the case of a pressure control valve when compared with the known layout.

The hydraulic actuation circuit 20 according to the present invention may be similar in structure and operation to the known flow control valve 14 described above, and the second line 22 at a predetermined first pressure P _PRI . The first line through respective flow control valves 23 and 27 used respectively to set the pressure level within the third line 26 at a pressure level within the predetermined second pressure P _SEC level. And a second hydraulic line 22 and a third hydraulic line 26 branched from 21.

FIG. 7 shows a variant of the FIG. 6 layout of the hydraulic system TH, in which the electric drive pump PE has a predetermined line pressure P _LINE and a predetermined flow in the hydraulic actuation circuit 20. If not produced, the auxiliary pressure level P _AUX may be temporarily raised to a higher level. The advantage of this variant is that the electric drive pump PE may be of less flow and / or pressure capacity and therefore cheaper and more efficient, so that at least the critical pressure level P _AUX at a critical operating condition is a mechanical drive pump. (PM) is at least temporarily raised, thereby helping the electric drive pump (PE).

According to the present invention, this property allows the control pressure P _SOL as well as the pressure feedback line 16a and the mechanical spring 16b to be able to actively control the auxiliary pressure P _AUX to a predetermined level. It can be realized by providing a control pressure line 16c to the valve biasing means of the auxiliary pressure regulating valve 16 which allows it to act on 16. Alternatively or additionally, this property is such that the pressure level in the hydraulic actuation circuit 20 and the control pressure associated with the pressure level respectively affect the auxiliary pressure regulating valve 16 but in opposite ways. It can also be implemented by manually controlling the auxiliary pressure P _AUX by allowing it to. This latter characteristic is illustrated by the pressure feedback line 16d and the control pressure line 16c shown in FIG. 7, by the secondary pressure P _SEC in the hydraulic actuation circuit 20 by the pressure feedback line. ) Acts on the secondary pressure regulating valve 16, in which case the secondary pressure P _SEC present in the pressure control line 27c of the secondary pressure flow regulating valve 27 by said control pressure line. the associated _{control-pressure-control} pressure that corresponds to the (P _{SOL SEC)} to (P _SOL) also act on the auxiliary pressure control valve (16). In this arrangement to add a second pressure regulating valve 16 and is temporarily deflected in the secondary pressure control pressure related to the (P _{SEC) -} a change in (P _{SOL SEC),} and the secondary pressure (P _SEC) in its The lag that normally occurs between corresponding changes. Of course, these additional valve deflection means 16c, 16d of the auxiliary pressure regulating valve 16 should be arranged such that the auxiliary pressure P _AUX is increased accordingly if an increase in the secondary pressure P _SEC is required. do.

It is noted that this main solution can of course be applied to any particular embodiment of the basic hydraulic arrangement according to the invention.

FIG. 8 shows an alternative variant to the arrangement of FIG. 6 to realize proper passive control of the auxiliary pressure P _AUX . In this arrangement, in addition to the pressure feedback line 16a and the mechanical spring 16b, the auxiliary pressure, illustrated by the line pressure P _LINE and the pressure feedback lines 16e and 16f and the switch valve 16g shown in FIG. Valve of the auxiliary pressure regulating valve 16 in accordance with the difference between the highest value of the primary and secondary pressures P _PRI , P _{SEC in} the hydraulic actuation circuit 20 to affect the pressure regulating valve 16. The deflection means is controlled manually.

Claims (8)

A continuously variable transmission 1 for transmitting a driving force of the engine E to a driven load L, the continuously variable transmission 1 actuating and coupling means of the transmission 1 at least within the range of the transmission ratio. And a set of hydraulic pumps (PM, PE) for realizing a pressurized supply of hydraulic medium for actuation of at least one auxiliary hydraulic user (U1, U2) of the transmission (1), such as C). The set of pumps PM, PE comprises a mechanical drive pump PM which can be driven by the engine E and an electric drive pump PE which can be driven by an electric motor independently of the engine E, In the continuously variable transmission 1 whereby a mechanical drive pump can supply hydraulic medium from the reservoir 10 for the hydraulic medium to the main hydraulic line 11 of the transmission 1. The electric drive pump PE is arranged in series with the mechanical drive pump PM, i.e. it can suck hydraulic medium from the main hydraulic line 11 and hydraulic actuation of the transmission 1 for the operation of the transmission 1. Continuous transmission, characterized in that the hydraulic medium can be supplied to the circuit (20). 2. The continuously variable transmission according to claim 1, wherein the auxiliary hydraulic user (U1, U2) is supplied with hydraulic medium from the main hydraulic line (11) for actuation of the auxiliary hydraulic user (U1, U2). The continuously variable transmission according to claim 1 or 2, wherein the auxiliary pressure control valve (16) is provided for controlling the pressure in the main hydraulic line (11) to a predetermined auxiliary pressure (P _AUX ). The continuously variable transmission according to any one of claims 1 to 3, wherein the auxiliary pressure (P _AUX ) is set according to the control pressure (P _SOL ) applied to the auxiliary pressure control valve (16). The auxiliary pressure P _AUX is set according to the hydraulic pressure P _LINE ; P _SEC ; P _PRI in the hydraulic actuation circuit 20 applied to the auxiliary pressure control valve 16. Stepless transmission, characterized in that. The amount of medium supplied to the hydraulic actuation circuit 20 by the electric drive pump PE affects the electric power supplied to the electric motor of the pump PE. Continuously controlled according to the hydraulic pressure (P _LINE ; P _SEC ; P _PRI ) in the hydraulic actuation circuit 20, in particular according to the main highest hydraulic level therein. 7. The hydraulic actuation circuit 20 comprises at least two pressure chambers 7, 8 respectively associated with respective pulleys 5, 6 of the transmission 1. Thereby, the drive belt 4 around the pulleys 5, 6 and the means PE, 21-27 and the means for independently controlling the respective hydraulic pressures P _SEC ; P _{PRI in} these at least two pressure chambers 7, 8. Continuously variable transmission, characterized in that the winding. 8. The continuously variable transmission according to claim 1, wherein the electric drive pump (PE) is reversible. 9.

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