Flow regulator valve in hydraulic control system for automatic transmission

In an hydraulic control system for an automatic transmission of a vehicle, when a low range frictional engagement mechanism is engaged in response to shift-down operation of the transmission, a flow regulator valve serves to steplessly regulate flow of fluid from a source of line pressure to the low range frictional engagement mechanism in accordance with changes of travel speed of the vehicle.

BACKGROUND OF THE INVENTION 
The present invention relates to an hydraulic control system for an 
automatic transmission of a vehicle, and more particularly relates to a 
flow regulator valve disposed within the hydraulic control system for 
regulating the flow of fluid supplied from a source of line pressure to a 
servomotor of a frictional engagement mechanism of the transmission. 
To prevent undesired shocks and various noises in shift-down operation of 
the transmission, it is required that the low range frictional engagement 
mechanism is gradually engaged in relation to disengagement of the high 
range frictional engagement mechanism. 
SUMMARY OF THE INVENTION 
It is, therefore, a primary object of the present invention to provide an 
hydraulic control system wherein when the low range frictional engagement 
mechanism is engaged in response to shift-down operation of the automatic 
transmission, a flow regulator valve serves to steplessly regulate the 
flow of fluid from the pressure source to the low range frictional 
engagement mechanism in accordance with changes of travel speed of the 
vehicle. 
According to the present invention, there is provided a hydraulic control 
system for an automatic transmission having an input shaft adapted to be 
driven by an engine, an output shaft adapted to drive the vehicle, a 
change-speed gearing including low and high range frictional engagement 
mechanisms for respectively completing low and high speed ratio power 
trains between the input and output shafts, the hydraulic control system 
comprising a fluid reservoir, a source of line pressure, a first fluid 
passage in communication with the pressure source, a second fluid passage 
in communication with the low range frictional engagement mechanism, a 
third fluid passage in communication with the high range frictional 
engagement mechanism, a throttle valve connected to the pressure source 
for producing throttle pressure in accordance with depression of an 
accelerator pedal, a governor valve connected to the pressure source and 
driven by the output shaft for producing governor pressure in accordance 
with rotational speed of the output shaft, and a shift valve responsive to 
the governor pressure and the throttle pressure for respectively 
connecting the second and third fluid passages to the first fluid passage 
and said reservoir when the governor pressure is lower than the throttle 
pressure and for respectively connecting the second and third fluid 
passages to the reservoir and the first passage when the governor pressure 
increases higher than the throttle pressure, and wherein the improvement 
comprises a flow regulator valve disposed within the second passage and 
responsive to the governor pressure to control the flow of fluid from the 
pressure source to the low range frictional engagement mechanism in 
accordance with the governor pressure.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, in particular to FIG. 1, a conventional 
automatic transmission may be seen to comprise a drive shaft 1, an input 
shaft 2, intermediate shafts 3, 4, and an output shaft 5. The drive shaft 
1 may be the usual crankshaft of a vehicle engine, and the output shaft 5 
may be connected by any suitable means with the driving road wheels of the 
vehicle. The input shaft 2 and the intermediate shafts 3, 4 are in effect 
piloted with respect to shafts 1, 5. The transmission comprises in general 
a hydraulic torque converter 20, hydraulically operated friction clutches 
10, 11, hydraulically operated friction brakes 12, 13, one-way clutches 
14, 24, and planetary gear sets 30, 40. 
The hydraulic torque converter 20 includes a pump impeller 21, a turbine 
runner 22 and a vaned stator 23. The pump impeller 21 is driven by drive 
shaft 1, and the turbine runner 22 is connected to input shaft 2. The 
stator 23 is rotatably mounded on a stationary sleeve 7, which is fixed to 
transmission housing 6, and the one-way clutch 24 is disposed between the 
stator 23 and stationary sleeve 7. The one-way clutch 24 is so arranged as 
to allow free rotation of stator 23 in the forward direction, that is in 
the same direction in which the drive shaft 1 rotates and prevents 
rotation of stator 23 in the reverse direction. 
The first friction clutch 10 is arranged to connect the input shaft 2 with 
the intermediate shaft 3, and the second friction clutch 11 is arranged to 
connect the input shaft 2 with the intermediate shaft 4 rotatable on the 
shaft 3. The first planetary gear set 30 comprises a first sun gear 31 
fixed to intermediate shaft 4, a planet gear 32 in mesh with sun gear 31, 
and a ring gear 33 in mesh with planet gear 32. The planet gear 32 is 
journalled on a carrier 34 which is rotatably disposed within transmission 
housing 6 through the one-way clutch 14. The carrier 34 is provided 
thereon with the second friction brake 13, and the ring gear 33 is 
connected to output shaft 5. The one-way clutch 14 is so arranged as to 
allow free rotation of carrier 34 in the forward direction, that is in the 
same direction in which the drive shaft 1 rotates and prevents rotation of 
carrier 34 in the reverse direction. 
The second planetary gear set 40 comprises a second sun gear 41 fixed to 
intermediate shaft 4, a second planet gear 42 in mesh with sun gear 41, 
and a ring gear 43 in mesh with planet gear 42. The ring gear 43 is 
connected to intermediate shaft 3, and the planet gear 42 is journalled on 
a carrier 44 which is connected to output shaft 5. The intermediate shaft 
4 is provided thereon with the first friction brake 12. 
For understanding respective drive power trains under each shifted position 
of the transmission, the relative engagement and disengagement of the 
friction clutches, the friction brakes and the one-way clutch may be 
summarized in the following chart. In the chart, the symbol of "0" means 
engagement of the indicated friction brakes and clutches, the symbol of 
"X" means engagement of the indicated friction brakes during engine 
braking operation of the vehicle, and the symbol of "#" means engagement 
of the one-way clutch during travel of the vehicle. 
______________________________________ 
One-way 
Clutches Brakes Clutch 
(10) (11) (12) (13) (14) 
______________________________________ 
First 0 X # 
Second 0 0 
Third 0 0 
Reverse 0 0 
______________________________________ 
In FIG. 2, there is illustrated an hydraulic control system for the 
transmission which comprises a fluid pump 101, a pressure regulator valve 
200 and a manual selector valve 210. The fluid pump 101 is connected to a 
fluid reservoir 100 and driven by drive shaft 1 to produce line pressure 
in a fluid passage 102 as a source of hydraulic pressure. The pressure 
regulator valve 200 is provided therein with an upper chamber 204 formed 
by an upper spool and lower chambers 205, 206 formed by a lower spool. In 
operation of the regulator valve 200, the upper spool is moved in 
accordance with variation of pressure in chambers 204, 205, 206 to control 
flow of fluid from the pump 101 to a passage 103 such that the line 
pressure in passage 102 is regulated in a predetermined value. 
The manual selector valve 210 includes a spool 211 which is displaced by a 
manual shift lever (not shown) provided in the vehicle cab for desired 
operation of the operator. With the selector valve 210, the line pressure 
in passage 102 is applied into fluid passages 104 to 107 by displacements 
of spool 211, as showing in the following second chart. 
______________________________________ 
Selected Passage Passage Passage Passage 
Position (104) (105) (106) (107) 
______________________________________ 
Reverse -- -- 0 0 
Neutral -- -- -- -- 
D-range 0 -- -- -- 
2nd-range 
0 0 -- -- 
Low-range 
0 0 0 -- 
______________________________________ 
In the second chart, the symbol of "-" means interruption of the indicated 
passage, and the symbol of "O" means communication of the indicated 
passage with the line pressure. The selected positions respectively 
indicate the positions of the mannual selector valve 210 to condition the 
transmission for the selected drive range. 
In the hydraulic control system, servomotors 360, 370 are provided to 
engage the friction clutches 10, 11 respectively, and servomotors 380, 390 
are provided to engage the friction brakes 12, 13 respectively. The line 
pressure applied to servomotor 360 is controlled by an orifice in a check 
valve 280 and an accumulator 330, and also the line pressure applied to 
servomotor 370 is controlled by an orifice in a check valve 290 and an 
accumulator 340. Furthermore, the line pressure applied to servomotor 380 
is controlled by an orifice in a check valve 300, a flow regulator valve 
500 and an accumulator 350. In this embodiment, it should be recognized 
that provision of the regulator valve 500 is the subject matter to 
complete the present invention. The construction and operation of the 
regulator valve 500 will be described later in detail to clearly point out 
the subject matter of the present invention. 
The hydraulic control system further includes a throttle valve 240 for 
producing a throttle pressure in response to depression of an accelerator 
pedal of the vehicle, and a governor valve 260 for producing a governor 
pressure in response to rotational speed of output shaft 5. The throttle 
valve 240 includes a down-shift plug 241 movable within a stepped bore to 
be moved by the accelerator pedal, and further includes a spool 243 
movable within the bore to control the flow of fluid from passage 102 to a 
passage 108. The down-shift plug 241 is interconnected with spool 243 
through a spring 242 to control the flow of fluid from passage 102 to a 
passage 110. Thus, the throttle pressure from throttle valve 240 is 
applied through passage 108 to a 1-2 shift valve 220 and a 2-3 shift valve 
230, and is also applied through a passage 117 to regulator valve 200. 
The governor valve 260 is provided on the output shaft 5 to control the 
line pressure from passage 104 in accordance with increase of the 
rotational speed of output shaft 5, thereby producing a governor pressure. 
The governor pressure is applied through a passage 109 to the 1-2 and 2-3 
shift valves 220, 230, and is also applied through a passage 116 to a 
cut-off valve 250. The cut-off valve 250 serves to control the flow of 
fluid from passage 108 to passage 118 in accordance with variation of the 
throttle and governor pressure from throttle and governor valves 240, 260. 
Thus, the throttle pressure is decreased by the cut-off valve 250 to 
prevent unnecessary power loss of fluid pump 101. 
The 1-2 shift valve 220 includes a pair of spools 221, 222 movable within a 
stepped bore and a spring 223 interposed between the spools 221, 222. The 
spool 221 is moved upwardly in accordance with increase of the governor 
pressure in passage 109 to connect the passage 104 to a passage 111 for 
2-3 shift valve 230. When the governor pressure decreases, the spool 221 
is moved downwardly by the throttle pressure from passage 108 to connect 
the passage 111 to a drain port. The spool 221 is also moved downwardly by 
the line pressure from passage 110 to connect the passage 111 to the drain 
port. The spool 222 is moved downwardly by the line pressure from the 
passage 106 to connect the passage 106 to a passage 112 for the servomotor 
390. 
The 2-3 shift valve 230 comprises spools 231, 232, 233 movable within a 
stepped bore and a spring 234 interposed between the spools 231, 233. The 
spools 231, 232 are moved upwardly in accordance with increase of the 
governor pressure from passage 109 to connect the passage 111 to a passage 
114 for the servomotor 370 and to connect a passage 113 for the servomotor 
380 to a drain passage 235. When the governor pressure decreases, the 
spools 231, 232 are moved downwardly by the throttle pressure from passage 
108 such that the passage 111 is disconnected from the passage 114 and 
connected to the passage 113. When the spool 233 is moved down by the line 
pressure from passage 105, the spools 231, 232 are also moved downwardly 
by the spring 234 to connect the passage 111 to the passage 113. When the 
spool 232 is moved down by the line pressure from the passage 110, the 
spool 231 is moved downwardly by the spring 234 to connect the passage 111 
to the passage 113. 
FIG. 3 illustrates an embodiment of the flow regulator valve 500 which 
comprises a spool 501 movable within a bore 511 of a valve housing 510 and 
a compression spring 502 biasing the spool 501 upwardly. The valve housing 
510 has first and second inlet ports 512, 513, an outlet port 514 and a 
pilot port 517. The first inlet port 512 is connected through a bypass 
passage 113a to the passage 113, the second inlet port 513 is connected 
through the check valve 300 to the passage 113, the outlet port 514 is 
connected to a passage 113b for the servomotor 380, and the pilot port 517 
is connected to the governor valve 260 through the passage 109. The valve 
housing 510 is also provided with a recess 512a of a V-shaped 
cross-section at the bottom wall portion of the first inlet port 512, as 
shown in FIGS. 3, 4. The recess 512a opens at its upper edge into the 
first inlet port 512 and also opens at its inner vertical edge into the 
bore 511. 
The spool 501 is provided thereon with a pair of lands A, C which 
subdivides the interior of the bore 511 into three chambers 515a to 515c. 
The upper chamber 515a is in communication with the passage 109 through 
the pilot port 517, and the lower chamber 515c is in communication with a 
drain passage. The intermediate chamber 515b opens toward the interior of 
recess 512a to lead therein flow of fluid from the bypass passage 113a. 
The intermediate chamber 515b is also in communication with the passage 
113 through the second inlet port 513 and is in communication with the 
passage 113b through the outlet port 514. The upper land A of spool 501 
has a stepped portion B which is cooperable with the V-shaped peripheral 
wall of recess 512a to provide a variable orifice 516 within the chamber 
515b. While the spool 501 is maintained in the upper stroke end due to 
biasing force of the spring 502, the orifice 516 provides a maximum 
opening area to permit a maximum amount of fluid flowing from the passage 
113a of the passage 113b, as shown in FIG. 4. When the spool 501 is moved 
downwardly in accordance with increase of the governor pressure from 
passage 109 against biasing force of the spring 502, the opening area of 
orifice 516 is decreased to steplessly throttle flow of fluid from the 
passage 113a to the passage 113b, as shown in FIG. 5. 
In operation, when the engine is rotated in the neutral position of the 
manual selector valve 210 to drive the fluid pump 101 and torque converter 
20, fluid from the pump 101 is partly applied by the pressure regulator 
valve 200 to the passage 102 as the line pressure, and the remaining fluid 
is applied by the regulator valve 200 to the torque converter 20 and other 
lubricated portions through the passage 103. The line pressure from 
passage 102 is applied to the accumulators 330 to 350 and the throttle 
valve 240 but is not applied to the passages 104 to 107 to condition the 
servomotors 360 to 390 inoperative. Thus, the output shaft 5 may not be 
rotated regardless of rotation of the input shaft 2. 
When the manual selector valve 210 is shifted to its Drive range position, 
the line pressure from passage 102 is applied to the passage 104 and then 
applied to the servomotor 360 and governor valve 260. In this instance, 
the line pressure to servomotor 360 is controlled by the orifice in the 
check valve 280 and the accumulator 330 to conduct smooth engagement of 
the friction clutch 10. Thus, the transmission is conditioned for the 
first speed ratio power train. When the accelerator pedal is depressed to 
increase rotational speed of the engine, the vehicle travels at the first 
speed ratio power train in the forward direction. The spool 243 of 
throttle valve 240 is also moved in response to depression of the 
accelerator pedal to produce the throttle pressure in passage 108, and the 
governor valve 260 is operated in response to the forward travel of the 
vehicle to produce the governor pressure in passages 109, 116. 
When the governor pressure is increased in accordance with increase of the 
vehicle speed, the spool 221 of 1-2 shift valve 220 is moved upwardly 
against the throttle pressure from the passage 108 and biasing force of 
the spring 223 to connect the passage 104 with the passage 111. Then, the 
line pressure is applied through the 2-3 shift valve 230 and the flow 
regulator valve 500 to the servomotor 380. In this instance, the line 
pressure to servomotor 380 is controlled by the orifice in check valve 300 
and the accumulator 350 to conduct smooth engagement of the friction brake 
12. Thus, the transmission is conditioned for the second speed ratio power 
train. 
When the governor pressure is further increased, the spools 231, 232 are 
moved upwardly against the throttle pressure from the passage 108 and 
biasing force of the spring 234 to connect the passage 111 with the 
passage 114 and to connect the passage 113 with the drain passage 235. 
Then, the line pressure from servomotor 380 is released through the 
passages 113, 235 to disengage the brake 12. At the same time, the line 
pressure from passage 111 is applied to the servomotor 370 through the 
passage 114, the check valve 310 and the passage 115. In this instance, 
the line pressure to servomotor 370 is controlled by the orifice in check 
valve 290 and the accumulator 340 to conduct smooth engagement of the 
friction clutch 11. Thus, the transmission completes the third speed ratio 
power train. 
When the accelerator pedal is deeply depressed to shift down from the third 
speed ratio power train to the second speed ratio power train, the 
down-shift plug 241 of throttle valve 240 is moved upwardly to apply the 
line pressure from the passage 102 to the 2-3 shift valve 230 through the 
passage 110. At the same time, the throttle pressure of a high value is 
produced by the throttle valve 240 in response to deep depression of the 
accelerator pedal and is applied to the 2-3 shift valve 230 through the 
passage 108. This moves downwardly the spools 231, 232 of 2-3 shift valve 
230 against the governor pressure from passage 109. Then, the passage 114 
is disconnected from the passage 111 and is connected to the reservoir 100 
through the passage 107 and the manual selector valve 210, whereas the 
passage 111 is connected to the passage 113. Thus, the line pressure from 
servomotor 370 is released through the check valves 290, 310 to disengage 
the friction clutch 11, whereas the line pressure from passage 111 is 
applied to the servomotor 380 to engage the friction brake 12. 
In the shift-down operation of the transmission described above, the 
rotational speed of the engine and the governor pressure from governor 
valve 260 increase in accordance with increase of travel speed of the 
vehicle respectively, and centrifugal force acting on fluid within the 
servomotor 370 also increases in accordance with increase of travel speed 
of the vehicle. Then, a rate of fluid releasing from the servomotor 370 is 
decreased due to the centrifugal force to delay completion of 
disengagement of the friction clutch 11. Meanwhile, the spool 501 of flow 
regulator valve 500 is moved downwardly due to the governor pressure 
against biasing force of the spring 502 to move the stepped portion B of 
upper land A toward the V-shaped peripheral wall of recess 512a. This 
throttles steplessly fluid flowing from the passage 113a to the servomotor 
380 through the passage 113b to delay completion of engagement of the 
friction brake 12. 
In summary, it will be recognized that even if the vehicle runs at any 
travel speed, the friction brake 12 is gradually engaged by operation of 
flow regulator valve 500 in relation to disengagement of the friction 
clutch 11 to smoothly conduct the shift-down operation of the transmission 
so as to prevent undesired shocks and various noises. 
Although in the embodiment the variable orifice 516 of flow regulator valve 
500 includes the recess 512a of the V-shaped cross-section cooperable with 
the stepped portion B of the upper land A, it should be noted that various 
modifications may be made without departing from the spirit of the present 
invention and the scope of the appended claims.