TORQUE CONVERTER VALVE

A torque converter is disclosed. The torque converter includes a cover, a turbine shroud disposed within the cover defining a charging chamber, and a torus chamber. The torque converter may also include at least one check valve disposed within the turbine shroud. The check valve may be configured to permit flow from the torus chamber to the charging chamber in response to a pressure difference between the torus chamber and the charging chamber. Permitting fluid flow from the torus chamber to the charging chamber may facilitate controlling the rate of lock-up-clutch slip.

TECHNICAL FIELD

This disclosure relates to torque converter used in the automotive industry.

BACKGROUND

Vehicles with an automatic transmission may utilize a torque converter that includes a bypass clutch that manages torque transfer between the impeller and the turbine of the torque converter. The torque converter is capable of engaging and disengaging the bypass clutch to transfer torque and to stop the transfer of torque across the torque converter. It is preferable to control the amount and speed of engagement and disengagement of the bypass clutch within the torque converter.

SUMMARY

According to one embodiment of this disclosure, a torque converter is disclosed. The torque converter includes a cover, a turbine shroud disposed within the cover defining a charging chamber, and a torus chamber. The torque converter also includes a check valve disposed within the turbine shroud and is configured to permit flow from the torus chamber to the charging chamber in response to a pressure difference between the torus chamber and the charging chamber exceeding a threshold to facilitate controlling a rate of lock-up-clutch slip.

According to another embodiment of this disclosure, a torque converter is disclosed. The torque converter includes a cover that circumscribes an outer periphery of the torque converter, a turbine shroud defining a charging chamber and a torus chamber, an integrated turbine and an impeller disposed within the turbine shroud. A lock-up clutch is disposed between the turbine and the impeller and a pressure adjusting valve is disposed within the turbine shroud and the pressure adjusting valve facilitating a flow of fluid from the torus chamber to the charging chamber in response to a torus chamber pressure exceeding a threshold to facilitate controlling a rate of lock-up-clutch slip.

DETAILED DESCRIPTION

Vehicles with an automatic transmission may utilize a torque converter that includes a clutch that manages torque transfer between the impeller and the turbine of the torque converter. The torque converter has a bypass clutch that facilitates torque transfer between the impeller and the turbine of the torque converter. The clutch may provide three modes of bypass clutch operation, and torque multiplication may occur depending on the amount of slip between the impeller and the turbine sides. In an unlocked mode or an open mode, a maximum amount of fluid is carried by the torque converter housing, separating the impeller from the turbine. In a locked mode, a minimum fluid pressure is carried in the torque converter so the pressure does not separate the impeller from the turbine and they become mechanically locked together. In a slip mode, a limited amount of slip is employed between the impeller and the turbine, whereby the fluid may provide the target ratio for torque multiplication, in addition to noise-vibration and harshness (NVH) damping.

Referring toFIG. 1, a cross-sectional view of an example torque converter22is illustrated. The torque converter22transmits rotational power from the engine (not shown) to the transmission (not shown). The torque converter is connected to an engine (not shown) by bolting the stud106through a flywheel (not shown) as well as being piloted into the crank shaft (not shown) of an engine (now shown). The torque converter is connected with a spline engagement of the damper hub140to the input shaft (not shown) of a transmission (not shown). The stud106and pilot104are welded to the cover102. The cover102is preferably welded to the impeller122. A lock-up clutch, sometimes referred to as a clutch118includes friction material integrated within a portion of the turbine120. The torque converter22includes two distinct sides; a charging chamber108and a torus chamber110. The charging chamber is the portion of the torque converter22that extends above the pilot104, to the stud106, to the lock-up clutch118. The torus chamber is defined by the turbine shroud and the impeller shroud. The torus chamber and the charging chamber may be referred to as “torus side” or “charging side,” respectively.

During operation, the cover102and impeller122rotate as the engine is running and the torque converter begins to fill with oil that is supplied from transmission. The impeller includes a number of blades that, in response to the torque generated by the engine, fluid is dispersed from the impeller122to a number of blades of the turbine120. A reactor116includes a one-way clutch (OWC)114that is located between an inlet of the impeller122and an outlet of the turbine120. The reactor116includes blades that re-direct transmission fluid received from an outlet of the turbine120and the inlet of the impeller122. The re-direction of transmission fluid by the reactor116between the turbine and the impeller results in torque multiplication, providing a resultant torque from the impeller to the turbine. The resultant torque is transferred from the turbine through the damper hub140, into the input shaft of the transmission (not shown). The clutch118may be referred to as a lock-up clutch for the purposes of this disclosure.

The clutch118is locked by increasing hydraulic pressure within the charging chamber108and a decrease in pressure within the torus chamber110. In the locked state, a minimum amount of fluid flows through the clutch118. The engine torque is directly transferred from exterior portion of the torque converter through turbine120via clutch118without torque multiplication obtained from reactor116, damper hub140via multiple connections in the middle and finally into the input shaft of transmission (not shown). The clutch may go from its locked state into the slip mode by increasing the hydraulic pressure between the turbine and impeller so that the clutch118is separated. The amount of time required to go from the unlocked state to the locked state is known as the slip speed.

To increase fuel economy, it is advantageous to reduce the slip speed and the time required to go from the slipped mode to the locked mode. However, because the turbine and the impeller are rotating at two different speeds, locking them quickly at two different speeds may cause a driveline disturbance such as noise or vibration harshness (NVH). To allow for a gradual slip, it is advantageous to allow fluid flow from the torus chamber110to the charging chamber108. As mentioned above, in the unlocked state, the fluid within the torus chamber is pressurized as compared to the fluid within the charging chamber. To facilitate a gradual reduction in pressure between the charging chamber108and the torus chamber110a pressure adjusting valve130is disposed within the turbine shroud128.

Referring toFIG. 2, a detailed view of the pressure adjusting valve130is illustrated. The turbine shroud128defines a channel that facilitates fluid flow from the torus chamber110and the charging chamber110. The channel includes two portions, a torus chamber portion129aand a charging chamber portion129b. The charging chamber portion129bhas a wider cross-sectional area than the torus chamber portion129a. A block134and a spherical check ball136are disposed within the channel. A spring132connects the block134and supports the spherical check ball136. Because the spherical check ball136is larger than the torus chamber channel129a, no fluid is permitted to flow from the torus side110to the charging chamber108. The interior surface of the channel is more or less conically-tapered to guide the spherical check ball136into the seat and form a positive seal when stopping reverse flow.

As the fluid passes through the unlocked/open clutch118at an outermost portion of the torus chamber110, the check ball136wedges into the torus channel129aand blocks the flow of fluid from the torus chamber110to the charging chamber108. The check ball136wedges into the torus chamber129abecause the spring132has sufficient strength to and the fluid pressure within the charging chamber108surpasses the fluid pressure within the torus chamber110.

When transitioning from the unlocked to locked mode, the clutch118is closed in response to increased pressure within the charging chamber108. As the clutch feature118is closed, the fluid within the torus chamber110is compressed and the pressure within the torus chamber110increases. Once the pressure within the torus chamber110surpasses the strength of the spring132combined with the pressure within the charging chamber108the ball136moves towards the charging chamber108. When the ball136moves by compressing the spring132, a controlled amount of fluid flow is permitted between the torus chamber110, through the torus channel129a, to the charging chamber channel129band eventually to the charging chamber108. As the fluid passes through this channel, the pressure within the torus chamber110is gradually reduced so that the fluid passing through the clutch118at outermost portion of the torus chamber110flows at a decreased rate compared to when no fluid was permitted to flow through the valve130.

The reduced flow through the clutch feature118decreases the pressure within the torus chamber110so that the clutch118is smoothly engaged without a loss in resistance. The gradual decrease in pressure provides to control the slip of the clutch118. As the process is reversed, the pressure within the charging chamber108increases to a point where the spring132has sufficient force to move the check ball136to the torus channel129a. The check ball136blocks the channel and does not permit fluid to flow from the torus chamber110to the charging chamber108.