Abstract:
An electronically controlled transmission has microprocessor and a clutch housing including an integrated solenoid controlled valve; the clutch housing including a valve track operatively receiving a valve element connected for operation by the integrated solenoid controlled valve; and a friction disc pack within the clutch housing having a piston actuator pressurized by fluid flow regulated by operation of the integrated solenoid controlled valve in response to electronic control signals from the microprocessor.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to electronically controlled transmissions and more particularly to such transmissions having a plurality of solenoid valves grouped as a unit. 
     2. Description of the Prior Art 
     Automatic transmissions for use in vehicular applications are known in which multiple forward ratios from 3 to 5 speeds at the present time. Such systems can be mechanical and hydraulic controls that are load responsive to perform the drive and gear ratio selection. Such systems include one way clutches and various planetary gear sets along with clutches and brakes that are operated in response to the operation of grouped servo valves to execute shifts without interrupting the power flow from a power source to drive wheels of the vehicle. 
     In order to further improve transmission performance electronic transmission controls have been developed that combine electronic processing of vehicle operation to establish output signals to selectively energize the various solenoid valves to control the gear selection and for adapting the pressures within the transmission in accordance with the torque flow of the drive train. Examples of such transmissions are set-forth in U.S. Pat. No. 4,750,384. 
     It has been proposed that such electronically controlled transmissions have their solenoid valves operated so that the clutch apply and release sequences can be programmed in a manner to eliminate the need for one way clutch devices for smoothing gear shifts in the transmission. 
     Theoretically, such electronic controls appear to be able to produce shift smoothing without one-way clutches. In practice this has not been the experience of transmission designers. 
     The reason for a difference between theory and practice is in part due to the fact that the solenoid controlled valves are grouped in a valve housing on one part of the outer case of the transmission. 
     In such arrangements each of the solenoid valves that are grouped in one location on the transmission must be separately calibrated against a master. Likewise, the various clutch and brake units within the transmission must be separately calibrated. Once the clutches/brakes are assembled within a clutch housings it in turn is assembled within an outer transmission case that includes suitable internal flow patterns to connect the operating pistons of the clutch/brakes to one or more individual valves in a grouped valve arrangement thereon including the separately calibrated solenoid operated control valves. 
     Once assembled, variations in the separately calibrated components can produce unexpected lag between apply and release control steps at the clutch/brake components and as a consequence gear shift performance can be adversely affected. 
     It is known to provide a single solenoid controller for a clutch pack as set-forth in U.S. Pat. No. 4,750,384. However, in this arrangement the solenoid controller is mounted on the outer case of the transmission and the clutch pack is in a separate clutch housing. There is no suggestion that the solenoid controller be directly integrated within the clutch housing so that the clutch housing and solenoid controller can be calibrated as a single unit prior to assembly such that the operation thereof can be precisely determined prior to assembly. 
     Another problem with such arrangements is that the grouped solenoid operated control valves are located in a valve housing at a single location on the outer case of a transmission. This results in different length hydraulic flow paths to actuators located at radially and axially spaced locations with respect to a common centerline through the transmission. The pressure losses in such paths further add to the difficulty in properly calibrating the fluid and mechanical components of a transmission so as to be suitable for accurate electronic control without performance lag. 
     As a consequence the ability to affect various smoothing controls is limited not by the monitoring and electronic processing but rather by lags caused by differences in the imposition of pressure changes due to inadequate calibration. 
     SUMMARY OF THE INVENTION 
     The present invention includes the integration of solenoid controlled valves and clutch housings for use in automatic electronically controlled multi-speed transmissions so that they can be calibrated as a unit so as to improve friction disc pack response to electronic control signals in an electronic transmission control. 
     An object is to provide for such integration in a configuration that will reduce lag between solenoid controlled valve operation and imposition of hydraulic pressure on the actuator for a friction disc pack. 
     A further object is to provide for such integration by including the solenoid controlled valve within a drop in housing for a friction disc pack for controlling gear sets within an automatic transmission. 
     A feature of the invention is to provide such reduced lag arrangements wherein the transmission has a clutch housing for gear ratio control clutch or brake of the type having a friction disc pack. Such packs have a first plurality of discs connected to a first transmission component and a second plurality of disc connected to a second transmission component. A solenoid-controlled valve and valve tracking are directly integrated into the clutch housing and the solenoid-controlled valve is responsive to an output signal from a high-speed microprocessor. The valve tracking communicates a pressurized inlet plenum within the clutch housing to a piston for actuating the friction disc pack in a manner that reduces the hydraulic lag time so as to improve the response of the clutches to pressure changes directed thereto. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary sectional view of an integrated clutch housing and solenoid controlled valve of the present invention. 
     FIG. 2 is a diagrammatic view of a prior art multi-speed electronically controlled transmission. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 2 shows a electron transmission control  10  of the prior art including a selector lever and position switch  12  and a microprocessor  14  that receives a position switch signal from the selector lever and position switch  12 . Other monitors including a program switch  16 ; kick down switch  18  throttle valve angle sensor  20 ; output rpm sensor  22 ; engine torque  24  and engine rpm  26 ; all of which direct input signals to the microprocessor  14  for processing in a known manner and wherein the microprocessor  14  is programmed in a known manner to produce output signals for selectively actuating a plurality of solenoid controlled valves  30  that are grouped at one location on the underside of a transmission housing  32 . 
     In the past the fluid pressure from a pump is directed through valves in the grouped solenoid controlled valves and then through a passage or external line to a point of use. 
     As shown in FIG. 1, the transmission  40  of the present invention includes a plurality of friction couplings that are operated by a piston when a pressurized fluid is directed there against. One such friction coupling is shown in FIG.  2 . In order to avoid the lag problem of the prior art, the transmission  40  includes an outer case  42  and one or more drop in brake or clutch housings  44  for one or more friction disc packs  45 . 
     In the illustrated arrangement the drop in housing  44  has a splined inner surface  46  that is connected to externally splined plates  48 . The plates  48  are interleaved with internally splined friction discs  50 ,  56  coupled to a hub portion  52  of a gear shift gear set (not shown) of a known type. 
     The drop in housing  44  is secured with respect to the outer case  42  by being slidably engaged with an internal rib  42   a  on the interior surface thereof. 
     In accordance with the invention the drop in housing  44  is integrated with a solenoid controlled valve assembly  54 . A solenoid coil housing  56  is connected by a bracket  58  to the outer end  60  of the housing  44 . In this embodiment, the outer end  60  is formed on an annular cover  62  closing a brake housing surface  64  that can have a plurality of suitable passages therein for feeding one or more brake units if desired. 
     The cover  62  and housing  44  have a valve track bore  66  formed therethrough. The bore  66  has a suitable seal gland  68  at the outboard end thereof. It receives a valve track  70  therein with spaced shoulders  72 ,  74 ,  76  sealed against the bore  66  to form annular cavities  78  and  80 . The housing  44  includes an inlet passage  82  connected to a source of pressurized actuating fluid directed to cavity  78 . The cavity  80  connects to an outlet passage  84  in the housing  44  that is communicated with a piston bore  86  therein. The piston bore  86  receives an actuating piston  88  that will be acted upon by pressure from the inlet  88  to engage the friction disc pack  45 . When the actuation pressure is connected to an exhaust  90  in the controller  54  the piston  88  is biased by a return spring  92  so as to disengage the plates  48  and friction discs  50  of the pack  45 . The control of pressurized fluid within the controller  54  is by a valve element  92  of a known type with suitable lands thereon that seal against an internal bore  94  to control flow between the inlet passage  82 , the outlet passage  84  and the exhaust  90  via openings  96 ,  98  in the valve track  70  and as is known by those skilled in the prior art. 
     The solenoid operated control valve  54  is connected to a high speed microprocessor and because it is directly integrated on the housing  44  can be calibrated to accurately process outputs from such a microprocessor to produce a no lag response to brake engagement and release to produce a desired control of an associated gear set. 
     The solenoid operated control valve  54  will respond to output signals to shift the valve element  92  connected thereto within the valve track  70  such that pressurized flow from the transmission pump will be directly applied to the brakes such that the speed range of the multi-speed gear set can be adjusted smoothly in response to a variety of desired operating programs. 
     The invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation. 
     Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.