GB2048406A - Band brake assembly - Google Patents

Abstract

The assembly brakes a carrier (44) in an automatic power transmission mechanism and comprises a band 56 surrounding a drum 54 defined by carrier (44), a fluid pressure operated servo 74 with a piston rod 128 connected to the operating end of the band 56 by a strut 130, and the the anchor end of the band 56 being connected by a reaction strut 112 to a reaction pin 114 mounted in the housing 100 of the transmission; the struts 130, 112 are respectively received in recesses in the ends of the band 56 and one held therein by retainer means in the form of pins 136; 126 passing through aligned openings 134, 132; 124, 122, or (as seen in Fig. 3) in the form of tabs on the ends of the band. The lengths of the struts can be chosen to suit any particular application - this makes it unnecessary to provide mechanical adjustment in the servo to compensate for slack in the band. <IMAGE>

Description

SPECIFICATION Brake servo assembly for an automatic power transmission This invention relates to friction brake assemblies for automatic transmission systems.

According to the present invention, there is provided a friction brake assembly for use in an automatic power transmission mechanism for anchoring a reaction gear element against a stationary transmission housing comprising a brake drum adapted to be connected to said reaction gear element, a brake band encircling said drum, a reaction element supported by said housing adjacent one end of the said brake band, a fluid pressure operated servo supported by said housing and having a piston rod, one end of said piston rod being located adjacent the operating end of said band, the anchor end of said band being formed to define a recess, a reaction strut received in said recess, one end of said strut being adapted to be anchored against said reaction element, an opening forced in the end of said strut within said recess and retainer means carried by the anchor end of said band and extending within the opening in said strut to retain said strut in its assembled condition, the operating end of said band being formed to define a recess, a second strut between said operating end and said piston rod, an opening formed in said second strut adjacent said operating end of said band and retainer means in said operating end of said band received in the opening in the adjacent strut end to retain said strut in the assembled position.

The invention is especially suitable for use in an automatic transmission system similar to that shown in U.S. patent No. 3,404,575.

Such systems include a gear system that comprises a compound planetary gear unit with two torque input elements and two torque reaction elements. Clutch means are provided for connecting selectively the turbine of a torque converter to either one or the other or both of the torque input elements. The impeller of the torque converter is connected to a vehicle engine crankshaft.

An output gear element of the gear system is connected to a driven shaft, which n turn is connected to the vehicle traction wheels through a driveshaft and differential mechanism.

A reaction element of the gear system is connected to a brake drum which is surrounded by a brake band. A piston for a fluid pressure operated servo is connected at the operating end of the brake band by means of a strut, and the reaction end of the brake band is connected by means of a strut to a reaction point on the stationary transmission housing. The latter strut is formed with a precalibrated length so that adjustment of the brake servo would not be required after final assembly.

The operating end of the brake band is connected mechanically to one end of the associated strut prior to the final assembly operation and a corresponding connection is established between one end of the reaction strut and the reaction end of the brake band.

These connections facilitate final assembly of the brake band and the transmission mechanism and their lengths, or the length of one strut, can be calibrated so that it is unnecessary to provide for brake band adjustment for any particular transmission installation. In one embodiment of the invention, the connection between each of the band ends and their respective strut is achieved by means of a roll pin that extends through registering openings in the strut and in the end of the brake band.

According to another embodiment the connection is established by means of a tab formed on the brake band ends and an opening in the adjacent end of the strut that registers with the tab.

A preferred embodiment of the invention will now be described, by way of example, with reference to the drawings, in which: Figure 1 shows an automatic power transmission mechanism having a brake band servo capable of using the invention.

Figure 2 is a cross-sectional assembly view of a brake band for use in the construction of Fig. 1.

Figure 2A is a detail view of a brake band end as seen from the plane of section line 2A-2A of Fig. 2.

Figure 3 is a view similar to Fig. 2 showing an alternative embodiment for the brake band strut retaining means.

Figure 3A is a detail view of a brake band end as seen from the plane of section line 3A-3A of Fig. 3.

In Fig. 1 numeral 10 designates an internal combustion engine for an automotive vehicle driveline. Numeral 1 2 designates a driven shaft which is adapted to be connected to vehicle traction wheels 14 through a drive shaft and a differential-and-axle assembly. A hydrokinetic torque converter 1 6 is situated between the engine 10 and a multiple ratio gear assembly indicated generally by reference character 1 8.

The converter 1 6 includes a bladed impeller 20, a bladed turbine 22 and a bladed stator 24. The turbine, the impeller and the stator are arranged in known fashion in a torus circuit. The impeller is connected drivably to engine crankshaft 26, and turbine 22 is connected to a turbine shaft 28. The stator 24 is mounted on a stationary stator sleeve shaft 30. An overrunning brake 32 anchors the stator 24 against rotation in a direction opposite to the direction of rotation af the impeller, but which permits freewheeling motion of the stator in the direction of rotation of the impel ler.

The gear assembly 1 8 comprises a pair of sun gears of differential diameter, the larger sun gear being shown at 36. A first set of long planet pinions 38 mesh with sun gear 34 and also with ring gear 40. A set of short 34 and also with ring gear 40. A set of short planet pin ions 42 mesh with small sun gear 36 and with the long planet pinions 38. The planet pinions 42 and the planet pinions 38 are rotatably supported on a common carrier 44. Ring gear 40 is connected drivably to power output shaft 1 2. Small sun gear 36 is connected to intermediate shaft 46 and large sun gear 34 is connected to sleeve shaft 48.

The carrier 44 is adapted to be braked against the transmission housing by means of an overrunning brake 50 located between the carrier and a transmission center support 52 which is connected to the housing. Carrier 44 defines a friction brake drum 54 about which is positioned brake band 56.

A forward drive friction clutch 58 is adapted to connect the turbine shaft 28 to the intermediate shaft 46. It includes friction discs carried by clutch element 60 and by intermediate shaft 46 which are adapted to be engaged drivably by fluid pressure operated clutch servo 62. Clutch element 60 forms also a part of high-and-reverse clutch 64 which establishes a driving connection between the larger sun gear 34 and the clutch element 60.

Clutch 64 includes a clutch servo 66 having an annular piston that engages clutch discs carried by brake drum 68 and by companion clutch element 60. A brake band 70 surrounds the drum 68 and is engaged and released by a fluid pressure operated brake servo 72.

Brake band 56 for the carrier 44 is applied and released by fluid pressure operated brake servo 74. Brake servo 72, unlike brake servo 74, is a double acting servo. it is applied when fluid pressure is admitted to the pressure chamber 76 on the left hand side of the piston 78. It is released when both the pressure chamber 76 and the opposed pressure chamber 80 are pressurized. Brake band 56 is applied when pressure is admitted to the pressure chamber 82 of the servo 74. Brake band 56 is released by spring 84 acting on the piston 86.

Overdrive operation in the low speed ratio is obtained by engaging clutch 58. Turbine torque then is delivered to sun gear 36 through shaft 46. Carrier 44 acts as a reaction member since it is braked by the overrunning brake 50 against the housing. With the ring gear 40 acting as a torque output element, the output shaft 1 2 is driven at its lowest speed ratio. An upshift to the intermediate speed ratio is achieved by engaging the brake band 70 thus anchoring the sun gear 34. The overrunning brake 50 freewheels in this condition. Clutch 58 is engaged during operation in each of the overdriving ratios.

Direct drive operation is achieved by disengaging the brake 70 and applying both clutches 58 and 64 simultaneously. This locks together the elements of the gearing for rotation in unison to establish a 1:1 speed ratio.

Reverse drive operation is achieved by disengaging the clutch 58 and engaging the clutch 64. The brake band 56 is applied so that the carrier 44 acts as a reaction member as the ring gear 40 is driven in a reverse direction relative to the direction of motion'of the sun gear 34.

These are shown in Fig. 1 in schematic form the elements of the automatic control valve system. This includes a fluid pressure governor 88 connected to the output shaft 1 2. A transmission throttle valve 90, which is actuated by an engine intake manifold pressure sensitive transducer 92, supplies a torque sensitive pressure signal to the control valve system 94. The governor 88 supplies a speed signal to the same control valve system.

Pressure for the control valve system is supplied by an engine driven pump 97. the valve system responds to the signals from the throttle valve to the governor to distribute control pressure from the pump to the brake servos and the clutch servos to establish the shift sequence, previously described. The transducer 92 responds to a vacuum signal from the engine intake manifold 96. A driver controlled accelerator pedal 98 adjusts the position of the throttle valve blade in the throat of the carburetor associated with the manifold 96.

In Fig. 2 are shown in detail the servo and the brake band assembly for the carrier 44 illustrated schematically in Fig. 1. Numeral 100 designates the transmission housing.

Brake drum 54 is surrounded by brake band 56. The internal surface of the brake band 56 is formed with a semi-circular bend 104 and the operating end of the brake band 56 is formed similarly with a semicircular bend 106. The anchor end of the brake band 56 is nested in a brake band adaptor 108, which defines a continuation of the internal friction surface of the brake band. A reaction strut is disposed between the anchor end of the brake band 56 and a reaction pin 114 which is received in opening 11 6 in the housing 1 00.

Reaction pin 114 is provided with a groove 118 which receives a recess 1 20 in the adjacent end of the strut 11 2. This is best seen in Fig. 2A.

The end of the strut adjacent the brake band is provided with an opening 1 22 which is aligned with an opening extending in a generally radial direction with respect to the brake band as shown at 1 24. Opening 1 24 extends through the adaptor 108 and through the bend 104 of the brake band 56. A roll pin 1 26 extends through the aligned openings 1 22 and 1 24 thereby retaining the strut 11 2 in its assembled condition.

The operating end of the band is connected to servo piston rod 1 28 by means of brake band strut 1 30. The end of the strut 1 30 adjacent the brake band is received in the bend 106 and is formed with an openinig 1 32 which is aligned with an opening 1 34 formed in the bend 106 and the adaptor 11 0.

A roll pin 1 36 is received through the aligned openings 1 34 and 1 32 thereby retaining the strut 1 30 in its assembled condition.

The piston rod 1 28 is positioned slidably in opening 1 38 in the housing 100. It is attached to servo piston 86, which is slidably positioned in brake operating cylinder 142.

The outboard end of the piston rod 1 28 is provided with a notch 144 which receives the adjacent end of the strut 1 30.

The length of the strut 11 2 can be chosen to suit any particular application. This makes it unnecessary to provide a mechanical adjustment in the servo to compensate for slack in the brake band. It is possible to use a common servo and piston rod for any of a variety of transmission installations merely by choosing the correct blank for strut 11 2 as well as for the strut 1 30. In this way the dimension "X" shown in Fig. 2, which is a critical dimension, can be maintained. The roll pins that are used with the brake band ends and with the associated struts make it possible to assemble the brake band assembly during high volume manufacturing operations with no difficulty.

In the embodiment of Figs. 3 and 3A are provided an alternate means for attaching the ends of the brake band struts to the ends of the brake band. In the Fig. 3 and Fig. 3A embodiment the operating end of the brake band is provided with a tab 136' which extends radially inwardly toward the center of the band. The tab 144 is received within the opening 132' in the strut 130'. This tab connection is used in lieu of the roll pin 1 36 shown in Fig. 2. In a similar fashion the anchor end of the brake band is provided with a tab 126' which extends radially inwardly and which is received in opening 122' in the brake band strut 112'. Tab 126' serves the purpose of a roll pin 1 26. In other respects the construction of Fig. 3 is the same as the construction of Fig. 2, and the elements of the Fig. 3 construction have been identified by similar reference characters although prime notations are added.

Claims (4)

1. A friction brake assembly for use in an automatic power transmission mechanism for anchoring a reaction gear element against a stationary transmission housing comprising a brake drum adapted to be connected to said reaction gear element, a brake band encircling said drum, a reaction element supported by said housing adjacent one end of said brake band, a fluid pressure operated servo supported by said housing and having a piston rod, one end of said piston rod being located adjacent the operating end of said band, the anchor end of said band being formed to define a recess, a reaction strut received in said recess, one end of said strut being adapted to be anchored against said reaction element, an opening forced in the end of said strut within said recess and retainer means carried by the anchor end of said band and extending within the opening in said strut to retain said strut in its assembled condition, the operating end of said band being formed to define a recess, a second strut between said operating end and said piston rod, an opening formed in said second strut adjacent said operating end of said band and retainer means in said operating end of said band received in the opening in the adjacent strut end to retain said strut in the assembled position.

2. The combination as set forth in Claim 1 wherein each retainer means comprises a pin received through an opening formed in the associated end of said band, said pin extending through the opening in the adjacent end of the associated strut.

3. The combination as set forth in Claim 1 wherein said retainer means for each end of the band comprises a tab deformed from the material of the band end, said tab being received in the adjacent opening of the strut thereby retaining the associated strut in an assembled condition.

4. A friction brake assembly substantially as hereinbefore described and as illustrated in the drawings.