CN100472103C - Hydraulic circuits for torque damper assemblies for electrically variable transmissions - Google Patents

Abstract

The invention relates to a torsional shock absorber for electric variable speed transmission. The torsional damper is provided with a hydraulically actuated lock-up clutch for selectively coupling the engine directly to the transmission input shaft. An electric motor with electrically variable transmission can be effectively used to counteract engine pressure pulses when the spring of the torque damper is locked. During higher speeds, the centrifugal load placed on the oil in the torsion damper increases, causing improper engagement of the lock-up clutch. The present invention hydraulically balances the hydraulic actuator (or piston) that drives the lockup clutch to properly adjust the lockup clutch engagement.

Description

Hydraulic circuits for torque damper assemblies for electrically variable transmissions

This application claims priority to US Provisional Application 60/555,141, filed March 22, 2004, which is hereby incorporated by reference in its entirety.

technical field

The present invention relates to an electrically variable transmission having a torque damper assembly with a hydraulically balanced locking clutch assembly.

Background technique

Automobile engines produce undesired torque or vibrations that are transmitted through the vehicle transmission. To isolate such torques, torque dampers are used in automotive transmissions. These dampers are located between the engine crankshaft and the transmission input shaft or turbine shaft in order to substantially counteract the undesired torque produced by the engine. The shock absorbers are constructed with springs capable of carrying the maximum engine torque plus some allowable limits.

Behind a hybrid car, a premise is that the alternative power source can propel the vehicle, thereby reducing dependence on the engine providing power, thereby increasing fuel economy. Because hybrid vehicles can draw power from sources other than the engine, hybrid engines generally run at low speeds more often and can be switched off when the vehicle is being driven by the electric motor. For example, an electrically variable transmission relies alternately on an electric motor housed in the transmission to power the vehicle driveline. The engine in a hybrid vehicle must therefore be started and stopped more frequently than in a non-hybrid system. The engine produces pressure pulses during starts and stops which can produce undesired vibrations such as in hybrid vehicles with electrically variable transmissions. Greater functionality is therefore desired in the shock absorber assembly to help the electrically variable transmission smooth out these pressure pulses.

Finally, because the torque damper assembly is fixed to the engine crankshaft, the torque damper rotates at a high annular speed. When hydraulic fluid is used to control a torque damper, the fluid is subjected to centrifugal loads due to these ring velocities.

Contents of the invention

The present invention provides a means of hydraulically balancing the actuator (or piston) driving a lock-up clutch for a torque damper assembly of an electrically variable transmission (or EVT). The present invention includes two separate hydraulic circuits for delivering hydraulic fluid to opposite sides of the piston when it is necessary to balance the piston. The need for this balance depends on the centrifugal load placed on the hydraulic fluid caused by the ring velocity of the shock absorber assembly.

In one embodiment of the invention, each circuit runs in parallel with two pumps (one driven by the motor and the other driven by the engine) to help provide hydraulic fluid to targeted areas of the torque damper assembly.

More specifically, the present invention provides an electrically variable transmission having a rotatable torque damper assembly and at least one electric motor. The torque damper assembly includes a torsion spring operable to cancel or reduce pressure pulses and torque. A clutch pack is also provided with a hydraulically operated piston for selectively locking the torsion spring; however, at least one electric motor counteracts pressure pulses when the torsion spring is locked. Also included is hydraulic fluid available on opposite sides of the piston to hydraulically balance the piston sufficiently to prevent the clutch pack from at least partially locking the torsion spring in response to centrifugal force caused by rotational movement of the shock absorber.

Also provided is a method of operating a rotatable hydraulically actuated damper of an electrically variable transmission in start, stop and drive modes. The method includes: hydraulically locking the torque damper by hydraulic fluid during start and stop modes; and hydraulically counteracting a locking piston of the torque damper to prevent hydraulic locking of the torque damper during drive mode.

Description of drawings

The above features and advantages are readily apparent from the following detailed description of preferred embodiments for carrying out the invention, the accompanying drawings including:

Figure 1 is a schematic side view of an electrically variable transmission, with portions broken away to illustrate selected transmission elements and auxiliary pumps mounted to the transmission;

Figure 2 is an exploded sectional view of the torque damper assembly taken along one side of the centerline of the front portion of the electrically variable transmission having two schematically illustrated hydraulic circuits;

3 is a graph showing piston loading pressure as a function of shock absorber assembly speed (line A) and shock absorber container volume (line B) required to balance the piston;

Figure 4a is a cross-sectional view of the perforated thrust washer of Figure 2 isolating the transmission; and

Figure 4b is a front view of the perforated thrust washer of Figure 2 isolating the transmission.

Detailed ways

Referring to the drawings, FIGS. 1 and 2 , like numerals denote like or corresponding components throughout the drawings, a side view of an electrically variable transmission 10 is shown in FIG. 1 . Basically, the invention applies to an electrically variable transmission 10 having at least one electric motor A or B and a rotatable torque damper assembly 26 , as shown in FIG. 2 . The torque damper assembly 26 includes a torsion spring 32 operable to cancel or reduce pressure pulses and torque. A clutch pack (or lockup clutch 33 ) is also provided having a hydraulically operated piston 50 for selectively locking the torsion spring 32; thereby allowing one or both electric motors (A or B) to counteract engine pressure pulses. Also included is hydraulic fluid that may be applied to the piston chamber 58 and shock absorber reservoir 34 on opposite sides of the piston 50 to adequately hydraulically balance the piston 50 so as to prevent locking of the clutch 33 due to torque from the damper. The torsion spring 32 is locked by the centrifugal force of the rotation of the vibrator 26 .

More specifically, FIG. 1 shows selected components of an electrically variable transmission 10 comprising an input housing 12 and a main housing 14 with dual electric motors (A and B), driven through a series of planetary gearsets (not shown). shown), the selected components are directly supported by bearings on the main shaft 19 of the transmission 10. The motors (A, B) rotate the output shaft 20 through selectively engaged clutches (not shown). The oil pan 16 is disposed on the base of the main housing 14 and is configured to provide a quantity of oil for the transmission 10 and its components. The main housing 14 covers the innermost components of the transmission such as the electric motors (A, B), the planetary gear arrangement, the main shaft 19 and two clutches (all exemplarily given and not shown). Finally, the input housing 12 is bolted directly to the rear surface of the engine block of the engine 24 (shown in FIG. 2 ) and encloses the transmission components, which are mechanically connected to the engine 24 . That is, the input housing 12 covers the torque damper assembly 26 (shown in FIG. 2 ). The input housing 12 also supports an auxiliary pump 27 (shown in FIG. 1 ) mounted to the base of the input housing 12 and nested adjacent to the oil pan 16 .

The torque damper assembly 26 shown in FIG. 2 is generally used to isolate the transmission 10 from undesired torque generated by the engine 24 during operation, and also selectively assists the transmission electric motor (A or B) Eliminate engine pressure pulses. The torque damper assembly 26 includes an engine side cover 28 connected to an engine crankshaft 29 . The engine side cover 28 is welded to the transmission side covers 30 and 31 and accommodates the shock absorber spring 32 . Said two covers ( 28 and 30 ) define a container 34 which closes the locking clutch 33 and the piston 50 . The torque damper assembly 26 also houses a damper flange 38 having a hub portion 40 that mates with the input shaft 18 at complementary splines 42 . The engine side cover 28 of the torque damper 26 is attached to the engine wave plate 44 . The wave plate 44 is used to transmit torque generated by the engine 24 to the transmission and also to absorb any thrust loads generated by the shock absorber assembly 26 . The torque damper assembly 26 includes a series of damper springs 32 extending annularly or circumferentially between the engine side cover 28 and the transmission side cover 30 . The damper spring 32 absorbs and dampens undesired torque generated by the engine 24 during normal or drive mode operation (eg above 600 rpm). The torque damper assembly 26 has a maximum torque equal to that of the engine plus some allowable margin. The torque damper assembly 26 may be constructed similar in part to that disclosed in commonly owned US Patent 5,009,301, which is hereby incorporated by reference in its entirety.

The electrically variable transmission 10 is provided with two electric motors A and B, as shown in FIG. 1 . Electric motor A builds torque during start and stop, effectively counteracting engine pressure pulses caused when the engine is running below 600 rpm (either start and/or stop conditions). The damper spring 32 of the torque damper assembly 26 is locked by applying clutch plates 36 and 37 (of the lockup clutch 33 ) when the engine 24 is operating within a predetermined speed range. In the preferred embodiment, the torque damper assembly 26 is effectively locked when the engine is running at speeds less than or equal to 600 rpm. This mode of operation is desirable because either electric motor A or electric motor B can be used to actively counteract engine pressure pulses generated during starting and stopping in an electrically variable transmission. The lock-up clutch 33 inside the torque damper assembly 26 includes two action discs 37 connected to the damper flange 38, two friction discs 36 connected to the transmission side cover 30, backing plate 46 and connection To the snap ring 48 on the arm 61 of the shock absorber flange 38 . The lock-up clutch 33 is close to a hydraulic piston 50 which moves against the action disc 37 forcing the action disc 37 into engagement with the friction disc 36 . The piston 50 moves in response to the oil supplied from the oil passage 57 into the oil chamber 58 . This load acts on the backing plate 46 and the snap ring 48 and is accommodated by the shock absorber flange 38 . The damper hub 40 of the torque damper assembly 26 near the piston 50 and connected to the damper flange 38 has a transversely drilled passage 56 defining a radially extending opening 52 which allows oil to flow from the oil Road 57 via. The oil extends through a transversely drilled opening 55 in the input shaft 18 , through opening 53 , into a channel 56 on the front side of the piston 50 . The piston 50 is limited in engagement with the lock-up clutch 33 and is held in the disengaged position by a return spring 54 . As oil is supplied through the passage 56 of the shock absorber hub 40 , the pressure in the piston chamber 58 builds up a load sufficient to overcome the spring force and stroke the piston 50 , thereby engaging the lock-up clutch 33 . The container 34 also houses hydraulic circuit 59 through opening 51, into the inside diameter of tube 35 fitted into input shaft 18, through grooved thrust washer 41 (or spacer), into cavity or space 43. , and to the oil inside the container 34 . The oil contained in the container 34 is thus on the right side of the piston 50 as shown in FIG. 2 in order to counteract the oil supplied into the cavity 58 on the other side of the piston 50 .

The hydraulic circuits 57 and 59, shown in Figure 2, supply oil to the piston cavity 58 and the shock absorber reservoir 34 respectively; control the lockup clutch 33 and control its engagement and disengagement under predetermined conditions. This first circuit 57 delivers hydraulic fluid into a piston cavity 58 . This second circuit 59 is regulated under low pressure and finally sends oil into the container 34 on the other side of the piston 50 . The piston 50 inside the torque damper assembly 26 responds to a sufficient high pressure caused by oil supplied through the first circuit 57 by being stroked and engaging the lock-up clutch 33 , effectively locking the damper spring 32 . When the lockup clutch 33 is engaged, the torque damper spring 32 is released or locked so that the engine 24 is directly connected to the input shaft 18 of the transmission 10 . This condition is only preferred for engine start and stop (ie start and/or stop mode where the engine speed is within a predetermined speed range: 0-600 rpm).

The transmission 10 is capable of operating in electric mode with the engine 24 completely switched off. When the engine is stopped, the main pump 62, which draws power from the engine, is inactive. The main pump 62 and auxiliary pump 27 are inoperative at this time because the shock absorber container 34 is not sealed, allowing internal oil to leak from the shock absorber container 34 to about half full. As the engine restarts, the centrifugal load caused by the rotation of the input shaft 18 and the torque damper assembly 26 forces the remaining oil to the outer periphery of the torque damper assembly 26 . Similarly, oil remaining in the shock absorber hub 40 is forced into the piston cavity 58 (ie, the outer periphery of the piston cavity). Since the oil in the shock absorber flange 38 is collected in the piston cavity 58 , the oil in the piston cavity 58 presses heavily on the piston 50 . At high speeds, the centrifugal load on the oil (or hydraulic fluid) in the piston cavity 58 can overcome the force of the return spring 54 and stroke the piston 50 . In order for the piston 50 to stroke, the pressure differential between the piston cavity 58 and the shock absorber reservoir 34 must be greater than or equal to 4 psi to overcome the return spring, or greater than or equal to 60 psi to achieve full capacity on the clutch 33 . Line A of FIG. 3 shows the pressure differential of oil in the piston cavity 58 as a function of the speed of the torque damper assembly 26 increases. The x-axis represents the velocity of the torque damper assembly 26 and the y-axis represents the loading pressure on the piston 50 . Since the torque damper assembly speed is close to 4000 rpm, the hydraulic fluid in the piston cavity 58 results in a loading pressure of approximately 60 psi, which is sufficient for a full torque capability design on the clutch 33 . Improper engagement of the lock-up clutch 33 and effective locking of the torque damper assembly 26 can cause additional wear on transmission components, leading to premature failure or reduced service life. However, as shown by the intersection of lines A and B in Figure 3, when filling the shock absorber reservoir 34 using the pumps (27 and 62) provided, the piston 50 can be hydraulically balanced before reaching a loading pressure of 60 psi . While the pump can provide oil into the shock absorber reservoir 34, the auxiliary pump 27 is responsible for delivering oil into the reservoir 34 or the other side of the piston 50 when the transmission is operating in electric mode (or the engine is stopped).

A technical advantage of the present invention is that the hydraulic circuits 57 and 59 and the pumps 27 and 62 are configured to balance the hydraulic piston 59 as shown in FIG. 2 in readiness for engine operation. In order to balance the piston 50 at least 0.36 liters of oil must be in the shock absorber reservoir 34 as indicated by line B of FIG. 3 . When the auxiliary pump 27 is active, it draws oil from the sump and delivers oil in parallel to the control module 64 and the preferred regulator 70 (shown in FIG. 2 ). The priority regulator 70 regulates the pressure at which the auxiliary pump 27 operates (60 psi in the preferred embodiment) and directs excess oil to the heat exchanger 68 which passes the oil through the lubricating oil The regulator 72 returns to the transmission 10 and enters the hydraulic circuit 59 . The control module 64 will provide oil to the hydraulic circuit 57 to compress oil to 110 psi in the piston cavity 58 under certain predetermined conditions (or in the preferred embodiment in the start and/or stop mode of operation). When the engine starts and spins, the main pump 62 draws oil from the sump and delivers oil in parallel to the control module 64 and main regulator valve 66 . From the main regulator valve 66 the oil flows through the priority regulator 70 , into the heat exchanger 68 into the lube oil regulator 72 and into the hydraulic circuit 59 .

In the preferred embodiment, the lube oil regulator 72 ensures that the pressure of the oil in the shock absorber reservoir 34 does not exceed 30 psi. The control module 64 maintains an oil pressure of 2 psi in the hydraulic circuit 57 . Therefore, the piston 50 cannot be stroked to use the clutch 33 with oil at 2 psi in the piston cavity 58 , oil at 30 psi in the shock absorber reservoir 34 and the return spring 54 using a reverse load. The piston 50 is thus hydraulically balanced or prevented from engaging the lock-up clutch 33 . But when desired (or in start and/or stop mode of operation), the auxiliary pump 27 can implement the clutch 33 by supplying high pressure oil into the piston cavity 58, thereby overcoming the 30 psi in the shock absorber reservoir 34 and the return spring 54 the reverse force.

The two circuits (57 and 59) are isolated by a set of rotating sealing rings 74 and steel tubes 35 mounted on the input shaft 18 of the transmission. A grooved thrust washer 41 , as shown in FIGS. 4 a and 4 b , facilitates the passage of oil from the inner diameter of the tube 35 into the shock absorber reservoir 34 . The thrust washer 41 has grooves 76 on the outer rim to allow oil to easily pass through the washer 41 and into the shock absorber reservoir 34 .

While the preferred embodiment for carrying out the invention has been described in detail, those skilled in the art will understand that various designs may be made within the scope of what is claimed.

Claims (18)

1. An electrically variable transmission having a rotatable torque damper assembly and at least one electric motor, the torque damper assembly comprising: Torsion springs operable to eliminate or reduce pressure pulses and torque; a clutch assembly having a hydraulically operable piston for selectively locking the torsion spring; at least one electric motor operable to counteract pressure pulses upon locking the torsion spring; and hydraulic fluid that can be applied to opposing sides of the piston to hydraulically balance the piston sufficiently to prevent the clutch pack from locking the torsion spring at least in part in response to the rotational speed of the shock absorber, thereby enabling This torque is neutralized by the torsion spring. 2. The transmission of claim 1, further comprising: an auxiliary pump operable to pump said hydraulic fluid to an opposite side of said piston; wherein said auxiliary pump is driven by an electric motor. 3. The transmission of claim 1, further comprising: A main pump operable to pump the hydraulic fluid to one side of the piston. 4. The transmission of claim 1 , wherein said torsion spring and said clutch pack are enclosed by a transmission side cover and an engine side cover; said transmission side cover and said engine side cover defining said A side of the piston configured to receive the hydraulic fluid. 5. The transmission of claim 1, further comprising: an input shaft configured to receive said hydraulic fluid; and a thrust washer fitted to one end of the input shaft; the thrust washer has a groove enabling the thrust washer to easily guide the hydraulic fluid from the input shaft to one side of the piston . 6. The transmission of claim 5, further comprising: a tube mounted in the inner diameter of the input shaft; the tube operable to separate the hydraulic fluid in the input shaft. 7. The transmission of claim 1, further comprising: a shock absorber flange and a shock absorber hub to which the clutch assembly and the piston are secured, the clutch flange and the clutch hub at least partially defining a shock absorber operable to receive the piston on the other side of the piston passage of hydraulic fluid. 8. A vehicle having an engine producing pressure pulses and torque; and an electrically variable transmission having at least one electric motor having a hydraulically actuated torque damper assembly comprising: engine side covers secured to the engine; a shock absorber flange secured to said engine side cover and shock absorber hub; wherein the damper hub is fixed to the input shaft in the electrically variable transmission; the damper flange has a damper spring such that the torque damper assembly is able to absorb such engine torque and pressure pulses ; a transmission side cover secured to the engine side cover and configured to enclose at least said shock absorber flange; said transmission side cover and said engine side cover also define a receptacle enclosing said shock absorber flange and said shock absorber spring; said shock absorber flange and said transmission side cover selectively enclose a powered clutch disc for locking said shock absorber spring; and At least one electric motor in an electrically variable transmission for selectively canceling engine pressure pulses. 9. The vehicle of claim 8, further comprising: a piston operable to effect selective engagement of said clutch plate whereby said shock absorber spring is locked; Hydraulic circuits, including: a main pump driven by the engine and operable to pump hydraulic fluid to opposing sides of the piston; and An auxiliary pump driven by an electric motor and operable to pump the hydraulic fluid to opposing sides of the piston. 10. The vehicle of claim 9, wherein the shock absorber flange at least partially defines a piston cavity adjacent to one side of the piston and configured to receive the hydraulic fluid; and The damper flange defines in part a passage operable to direct the hydraulic fluid into the piston cavity. 11. The vehicle of claim 10, further comprising: an input shaft defining a radially extending opening operable to direct the hydraulic fluid from an inner diameter of the input shaft to an outer diameter of the input shaft; and into the channel. 12. The vehicle of claim 11, further comprising: a thrust washer fitted to one end of the input shaft; the thrust washer has grooves enabling the thrust washer to easily guide the hydraulic fluid from the input shaft to the other side of the piston . 13. The vehicle of claim 12, further comprising: a tube mounted in the inner diameter of the input shaft; the tube operable to separate hydraulic fluid contained in the input shaft. 14. The vehicle of claim 13, wherein the main pump is configured to pump the hydraulic fluid into a control module and a main regulator; the control module is configured to direct hydraulic fluid onto one side of the piston; the primary regulator is configured to direct hydraulic fluid to a priority regulator; the priority regulator directs the hydraulic fluid to a heat exchanger operable to direct the hydraulic fluid to a lube oil regulator; and The lube regulator is operable to direct the hydraulic fluid onto the other side of the piston. 15. The vehicle of claim 14, wherein the lube oil regulator is configured to direct the hydraulic fluid into the tube, through the thrust washer and to the other side of the piston; and The control module is configured to direct the hydraulic fluid between the input shaft and the tube, through the radially extending opening, onto the passage, and onto a side of the piston. 16. A method of operating a rotatable hydraulically actuated torque damper of an electrically variable transmission according to claim 1 at start-up comprising: hydraulically locking the torque damper in response to hydraulic fluid during start and stop modes; and The hydraulic fluid is hydraulically counterbalanced, preventing hydraulic locking of the torque damper during drive mode. 17. The method of claim 16, further comprising: The hydraulic fluid is pumped from a motor driven auxiliary pump to hydraulically lock the torque damper. 18. The method of claim 17, further comprising: The hydraulic fluid is pumped from the main and/or auxiliary pump hydraulically counteracting the torque damper.

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