Pressure regulating arrangement with a damping device for a control pressure of an automatic change-speed transmission

In a pressure-regulating arrangement for the control pressure of a shifting arrangement of a change-speed transmission, a slide valve member is actuatable by an adjusting sleeve connected with a control member of a driving engine by way of a pressure member. A hydraulic damping device with two mutually relatively movable damping parts of the piston-cylinder-type construction is provided in which one damping part is adapted to be supported with respect to the housing and the other is actuatable by way of the pressure member and damping medium is thereby displaced against the action of a throttle. In order to improve the control behavior by decoupling the damping function from the control slide valve member, the damping device is arranged at the end face of the control slide valve member facing the pressure member and the damping part movable relative to the housing is connected with the pressure member while a damping chamber enclosed between the damping parts is connected by way of a relief valve with a space under atmospheric pressure.

The present invention relates to a pressure-regulating arrangement for a 
control pressure of a shifting mechanism of an automatic change-speed 
transmission arranged behind the driving engine in the direction of power 
transmission which is used for triggering shifting back operations. 
In a known pressure-regulating arrangement of this type (Printed 
Publication No. 6 510 6801 00-0483 2,5 of Daimler-Benz A.G., 
Stuttgart-Untertuerkheim), the control spool or slide valve member is 
constructed at its end face opposite to the adjusting sleeve in one piece 
with the damping member operating as cylinder so that for achieving a 
damping action relatively large stroke movements of the control slide 
valve member are necessary which, however, affect the regulating behavior 
disadvantageously. 
On the other hand, a delay of the response of the control slide valve 
member which is effected by the damping device, with respect to the signal 
action of the adjusting sleeve is desirable under certain circumstances. 
Thus, fuel-economizing shifting programs of fully automatic vehicle 
transmissions can be so constructed and designed that the highest speed is 
reached already at velocities below 50 km/h. This means that the 
engine--predominantly in the coasting operation--drops off to idling 
rotational speed. The oil pump which is provided for the pressure oil 
supply of the automatic transmission operates with the same rotational 
speed and supplies an oil stream correspondingly small in quantity and 
pressure. 
During a suddenly occurring acceleration desire of the driver, such a 
transmission is capable of shifting back (down) at least over two speeds. 
The driver expresses this acceleration desire by actuation of the drive 
pedal whereby, on the one hand, the engine regulation is actuated in the 
sense of a higher engine output and, on the other, the transmission 
control is actuated in the sense of a shifting back. 
A shifting back (shifting down) of the transmission with simultaneously 
increasing torque of the engine requires a sufficient availability of 
pressure oil in quantity and pressure which is not always assured with the 
vehicle condition described above from which the shifting-back is to take 
place. 
It is therefore advantageous to gain a time-spacing between the initiation 
of the engine signal and of the transmission signal at the initiation of 
the acceleration wish by the driver by way of the actuation of the drive 
pedal, in the sense that initially the engine increases its rotational 
speed and therewith the feed quantity of the pump increases and only 
thereafter the shifting-back signal for the transmission is triggered. It 
is assured under these circumstances that the shifting-back takes place 
properly and orderly with sufficient pressure oil supply. 
The task underlying the present invention essentially consists in improving 
the regulating behavior in a pressure-regulating arrangement of the type 
described above while assuring the pressure oil supply also when shifting 
down from low rotational speeds. 
The underlying problems are solved according to the present invention in 
that the damping device is arranged on side of the end face of the control 
slide valve member facing the pressure member and the damping part movable 
with respect to the housing is immovably connected with the pressure 
member and the damping chamber is connected by way of breather or relief 
valves with a space that is at least under atmospheric pressure. 
In the pressure-regulating arrangement according to the present invention, 
the damping function is decoupled from the control slide valve member and 
is placed on the pressure member actuated by the adjusting sleeve by way 
of a spring force so that the flow cross section controlled by the control 
slide valve member can be matched in its characteristics to very small 
stroke movements of the control slide valve member. 
On the other hand, during a sudden acceleration desire of the driver, the 
pressure member actuated thereby by the adjusting sleeve can be brought 
into action on the control slide valve member only under displacement of 
the hydraulic damping medium against the throttling effect, i.e., with 
sufficient delay with respect to the revving up of the engine so that the 
pressure oil supply for a subsequent shifting-back is assured.

Referring now to the single figure of the drawing, a shifting slide-valve 
housing 11 of a shifting arrangement of a change-speed transmission 
arranged behind the internal combustion engine in the direction of power 
transmission is secured in the customary manner (not shown) at the 
underside of a transmission housing in such a manner that it immerses into 
the oil sump 61. The housing 11 includes a housing bore which is stepped 
twice in diameter and thus includes three sections disposed one behind the 
other in relation to its bore axis 37--37, and more particularly a valve 
bore 42 displaceably receiving a control slide valve member or control 
spool 1, a cylinder bore 43 and a sealing bore 44 terminating, open as 
such, in a housing end surface 40. 
The valve bore 42 terminates at its one end in a pressure chamber 62 of the 
housing 11 which is connected by way of a valve connection and an 
interconnected connecting channel with a control pressure channel 54 
leading to command slide valves for the shifting between two speeds each 
of the shifting arrangement. Within its center area, the control slide 
valve member 1 is provided with a control groove 45 which is in constant 
communication with the control pressure channel 54. The control groove 45 
is axially limited by one collar 49 and 50 each of the control slide valve 
member 1, whereby the transitions are formed each by a sharp-edged control 
edge which control in an alternate manner a throttle connection between 
the control pressure channel 54 and an annular groove 57 of the valve bore 
42, on the one hand, or an annular groove 64 of the valve bore 42, on the 
other, or close off the control pressure channel 54 with respect to both 
annualar grooves 57 and 64. The annular groove 57 is in communication with 
the oil sump 61 either directly or by way of a connecting channel with a 
communicating annular groove in the cylinder bore 43. The annular groove 
64 is connected to a pressure line 56 which is adapted to be placed under 
a--preferably constant--input pressure. In this manner the control slide 
valve 1 is acted upon at the end face 51 which is located opposite the 
housing end face 40, by the regulated control pressure of the line 54. The 
other end face 13 of the control slide valve 1 is acted upon by the 
pressure--which is approximately equal to the atmospheric pressure--of a 
pressure chamber 15 which forms a section of the cylinder bore 43 
adjoining the valve bore 42 and discharges openly into the oil sump 61. 
The collar or shoulder 50 of the control slide valve member 1 which closes 
off in a pressure-tight manner the valve bore 42 and the pressure chamber 
15 with respect to one another, has a dead-end bore, open as such, at the 
end face 13, into which is inserted an end pin of a pressure member 19. In 
its axial center area, the pressure member 19 is provided with a 
flange-like collar 70, from which two cross arms 23 extend radially that 
protrude through slot-like openings 22 of a support sleeve 16 with 
movement clearance; the support sleeve 16 is arranged concentrically to 
the bore axis 3713 37 and is used for the support at the housing of a 
control spring 2 which is supported at the one end face of the collar 70 
that is supported with its other end face used as abutment 20 against the 
end face 13 of the control slide valve member 1. 
The support sleeve 16 includes at its end face facing the control slide 
valve member 1 a radial collar 73 which is held in abutment at a shoulder 
of the housing 11 formed by the diameter step by means of one spring end 
of a return spring 72. The other spring end of the return spring 72 is 
supported at the inner sleeve end of an adjusting sleeve 3 which includes 
a piston section 71 guided pressure-tight and axially displaceable in the 
cylinder bore 43; the piston section 71 is thereby located between the 
sleeve end and a radial annular piston surface 69 that is supported under 
the action of the return spring 72 at the inner end face--which is used as 
housing abutment for the adjusting sleeve 3--of a sealing sleeve 68. The 
sealing sleeve 68 which is inserted movably and pressure tight into the 
sealing bore 44 and the adjoining section of the cylinder bore 43, 
includes a ring seal 67 which is used for sealing the adjusting sleeve 3 
with respect to the sealing bore 44. An actuating arm 63 of a two-armed 
angle lever 60 engages at the outer end face 65 of the adjusting sleeve 3 
whose other lever arm includes a connecting eye 59 for the fastening of a 
Bowden cable 30. The angle lever 60 is retained at the housing 11 by means 
of a pivot bearing 58 whereas the Bowden cable 30 may be connected with 
the throttle valve of a carburetor of an internal combustion engine which 
is controlled by the drive pedal. 
The housing 11 includes a pressure connection 55 terminating in the 
cylinder bore 43 within the area of the end face of the sealing sleeve 68; 
the pressure connection 55, in turn, is connected by a connecting channel 
with the control pressure channel 54. The surfaces 51 and 69 which are 
acted upon by the control pressure are equally large. 
By reason of its stepped diameter configuration, the central passage 39 of 
the support sleeve 16 forms a radial shoulder as abutment for a 
ring-shaped socket of a sieve 38 inserted into the passage 39 whereby the 
control spring 2 is supported with its adjacent spring end at the support 
sleeve 16 by way of the socket. 
The return spring 72 is so dimensioned that the support sleeve 16 is held 
with its collar 73 in immovable abutment at the housing 11 under all force 
and pressure conditions. 
The adjusting sleeve 3 operates by way of an adjusting spring 4 on a 
concentric inner pressure member 5 which, with its axial inner end face 24 
is used for the actuation of the control slide valve member 1 by way of 
radial abutment surfaces 21 of the cross arms 23 of the pressure member 19 
which are located radially outside of the support sleeve 16. 
The adjusting spring 4 is supported between immovable spring abutments 47 
and 48 of the pressure member 5 whereby an abutment sleeve 46 with 
corresponding spring abutments is inserted between the one spring end and 
the associated spring abutment 47. For the actuation of the adjusting 
spring 4, the adjusting sleeve 3 operates by means of an actuating 
abutment on an actuating abutment of the abutment sleeve 46. 
The center section 35 of the support sleeve 16 which adjoins the sieve 38 
carries a ring seal 18 which cooperates with an internal cylinder wall 17 
that forms the section of a dead-end bore reduced in diameter of the 
pressure member 5 which terminates openly as such at the end face 24. 
The section 35 of the support sleeve 16 passes over by way of a further 
diameter reduction into a reduced end section that forms a valve passage 
52 for a breather or relief valve 14 which utilizes the adjoining end face 
31 of the support sleeve 16 as valve seat. In this manner, a damping 
chamber 8 is enclosed in the interior space of the dead-end bore which is 
separated with respect to the pressure chamber 15 by the ring seal 18 and 
the breather valve 14. 
The damping chamber 8 is a component of a telescopic damping device 7 of 
the piston-cylinder-type of construction in which the part of the support 
sleeve 16 including the ring seal 18, the sleeve section 35 and the relief 
valve 14 forms the one damping member (piston 9) and the section of the 
pressure member 5 having the cylinder bore 17 forms the other damping 
member (cylinder 10). 
During a relative movement of the pressure member 5 with respect to the 
support sleeve 16 in the direction toward the control slide valve member 
1, the volume of the damping chamber 8 is reduced so that damping medium 
which is contained in the damping chamber 8 is displaced by way of the 
adjoining valve passage 52 into the pressure chamber 15 connected with the 
oil sump 61 by way of a throttle 12 in the mushroom-shaped valve closure 
member 32 of the relief valve 14. 
During a relative movement of the pressure member with respect to the 
support sleeve 16 in a direction pointing away from the control slide 
valve member 1, the volume of the damping chamber 8 increases so that as a 
result of the occurring pressure drop, pressure medium is forced out of 
the pressure chamber 15 into the damping chamber 8 by way of the relief 
valve 14 which now opens against the only weak spring force of a valve 
spring, into the damping chamber 8. The sieve 38 is series-connected for 
the protection of the throttle 12 against contaminations from the oil 
sump. 
The valve spring of the relief valve 14 is supported at a spring abutment 
sleeve 33 for a further return spring 25 which is effectively arranged 
between the pressure member 5 and the support sleeve 16. The return spring 
25 is supported between two mutually immovable spring abutments 26 and 27 
of the spring abutment sleeve 33, whereby an abutment ring 29 provided 
with corresponding abutments is inserted between the spring end 
coordinated to the pressure member 5 and the spring abutment 27. 
The abutment ring 29 cooperates by way of the one abutment with an abutment 
of the pressure member 5. 
The spring abutment sleeve 33 which is form-lockingly mounted on the 
support sleeve 16 is provided with radial flow apertures 34 in order to 
keep the throttle 12 in communication with the damping chamber 8. 
Whereas the spring abutment sleeve 33 is supported in the direction 
pointing toward the control slide valve member 1 at a sleeve offset 
delimiting the sleeve section 35, its end face facing the control slide 
valve member 1 is used for retaining the ring seal 18 in the opposite 
direction. 
The operation of the described pressure-regulating arrangement is as 
follows: 
In the illustrated idling position 41 of the angle lever 60--which is 
actuatable in the manner indicated in dash and dotted lines by way of the 
Bowden cable 30 from the carburetor throttle valve--the adjusting sleeve 3 
is held in its idling position 53 by the return spring 72 which is fixed 
by abutment surfaces. The actuating arm 63 constantly abuts at the end 
face 65. 
The pressure member 5 is held in its idling position 36 by the return 
spring 25 whereby the abutment sleeve 46 and the adjusting sleeve 3 are 
also held in mutual abutment. In the idling position 36, the pressure 
member 5 has an idling stroke 28 with respect to the pressure member 19 
and thus with respect to the control slide valve member 1. 
If the angle lever 60 is now pivoted counterclockwise, then a displacement 
of the adjusting sleeve 3 in the direction toward the control slide valve 
member 1 takes place necessarily. During a slow displacement, the 
adjusting sleeve 3 and pressure member 5 remain initially clamped together 
immovably with respect to one another by the adjusting spring 4 whereas 
the return springs 25 and 72 undergo spring movements, i.e., are 
compressed. This movement of the adjusting sleeve 3 is assisted by the 
pressure force occurring at the ring piston surface 69 whereby the 
abutment ring 29 leaves the spring abutment 27 and pressure medium is 
displaced with throttling effect out of the damping chamber 8 into the 
pressure chamber 15. The braking action which occurs thereby at the 
pressure member 5 is thereby the greater the faster its stroke movement. 
If the braking action exceeds the spring force of the adjusting spring 4 
during more rapid displacement movements of the adjusting sleeve 3, then 
the adjusting spring 4 is compressed accompanied by a lifting-off of the 
abutment sleeve 46 from the spring abutment 47 and the pressure member 5 
undergoes a delay with respect to the adjusting sleeve 3. 
When the end face 24 of the pressure member 5 comes into abutment in a 
certain partial load position 6 at the abutment 21 of the pressure member 
19 and thus the idling stroke 28 becomes zero, the relative movements of 
the damping members 9 and 10 with respect to one another are very small 
because in that case a further increase of the adjusting path of the 
adjusting sleeve 3 becomes effective at the pressure member 19, 
respectively, at the control slide valve member 1 essentially only in an 
increase of the spring force of the adjusting spring 4 counteracting the 
control pressure. 
If the angle lever 60 moves in the direction towards its idling position 
and thus finally also the damping part 10 returns into its idling position 
36, then the relief valve 14 opens as a result of the pressure drop which 
establishes by the volume enlargement of the damping chamber 8 so that 
pressure medium is now forced back out of the pressure chamber 15 which is 
now under the higher pressure, by way of the sieve 38 into the damping 
chamber 8. 
This operation is connected with the lifting off of the end face 24 of the 
pressure member 5 from the abutment 21, as a result of which the control 
slide valve member 1 is again dependent alone from the regulating spring 
2, i.e., a constant pressure value is adjusted over the idling stroke 28. 
While we have shown and described only one embodiment in accordance with 
the present invention, it is understood that the same is not limited 
thereto but is susceptible of numerous changes and modifications as known 
to those skilled in the art, and we therefore do not wish to be limited to 
the details shown and described herein but intend to cover all such 
changes and modifications as are encompassed by the scope of the appended 
claims.