HYDRAULIC PRESSURE REGULATING ARRANGEMENT

Abstract: Herein disclosed is a hydraulic pressure regulating arrangement for generating a servo actuating fluid pressure under which hydraulic fluid is supplied to a servo motor. This arrangement comprises a pressure regulating valve having a valve spool movable in response to hydraulic fluid pressure building up in a feedback chamber in such a direc­ tion as to increase opening degree of a drain port opening to a servo actuating fluid supply line as the pressure in the feedback chamber increases. A reservoir is provided which communicates with the servo actuating fluid supply line. A flow restrictor is disposed between the reservoir and the servo actuating fluid supply line and restricts flow of hy­ draulic fluid entering the reservoir. The feedback chamber communicates with the reservoir so that, upon start-up of an associated oil pump driven by an engine, the valve spool stays in a position to close the drain port until hydraulic fluid discharged by the pump fills the reservoir, thus allowing unregulated servo actuating fluid pressure to build up in the servo actuating fluid supply line.

Description: HYDRAULIC PRESSURE REGULATING ARRANGEMENT BACKGROUND OF THE INVENTION The present invention relates to a hydraulic pressure regulating arrangement for generating a servo actuating fluid pressure at which hydraulic fluid pressure is supplied to a servo motor for friction device of an automatic transmission. Hydraulic control systems for automatic transmissions employ an engine driven pump that pumps hydraulic fluid out of a source into a servo actuating fluid supply line that leads to a servo motor, a line pressure regulator valve having a drain port opening to the servo actuating fluid supply line, a feedback chamber communicating with the servo actuating fluid supply line, and a valve spool movable responsive to hydraulic fluid pressure building up in the feedback chamber in such a direction as to decrease opening degree of the drain port as the hydraulic fluid pressure within the .z t feedback chamber increases so as to regulate hydraulic fluid pressure in the servo actuating fluid supply line. Because, the viscosity of hydraulic fluid used in 'the automatic transmissions is temperature dependent and gets high at low ambient temperatures, the automatic transmission shows very poor start-up performance if ambient temperature is very low to an extent lower than such as -l00C. That is, at such low ambient temperature, hydraulic fluid pressure builds up abnormally slowly within a servo motor for a starting friction device such as a forward clutch, when a manual shift lever is set to a forward drive range position immediately after the pump starts pumping hydraulic fluid into the servo actuating fluid supply line. This is because hydraulic fluid passes through the servo actuating fluid supply line at an abnormally slow rate owing to high viscosity thereof. Thus, it takes a considerable time for the transmission to assume a power transferrable state where the forward clutch is engaged after the manual shift lever is set to the forward drive range position. This delay is often called as wlow temperature lag." An object of the present invention is to solve the above mentioned problem. SUMMARY OF THE INVENTION According to the present invention, the above mentioned problem has been solved by temporarily keeping servo actuating fluid pressure at a level high enough to force hydraulic fluid to pass through a servo actuating fluid supply line into a servo motor quickly after start-up of a pump. Specifically, in order to keep servo actuating fluid pressure (which may be often called as "line pressure) at a high level for a period of time after start-up of a pump, feedback pressure build-up within a feedback chamber of a pressure regulating valve is delayed by the provision of a fluid reservoir communicating with a servo actuating fluid supply line and a flow restrictor for restricting flow of hydraulic fluid entering the reservoir. The feedback chamber communicates with the reservoir so that no fluid pressure builds up within the feedback chamber until hydraulic fluid discharged by the pump fills the reservoir. Since the flow rate of hydraulic fluid entering the reservoir is restricted by the flow restrictor, the reservoir is left unfilled for a period of time after start-up of the pump and thus feedback pressure does not build up within the feedback chamber for this period of time. Thus, since pressure regulation is not initiated by the pressure regulating valve until the feedback pressure builds up in the feedback chamber, hydraulic fluid biased by hydraulic pressure unregulated by the pressure regulating valve is supplied quickly to the servo motor, thus shortening time till engagement of the associated friction device. Alternatively, in order to keep servo actuating fluid pressure at a high level for a period of time after start-up of a pump, a signal pressure regulating valve which produces a regulated signal fluid pressure upon which a servo actuating fluid pressure produced by a servo actuating fluid pressure regulating valve is boosted is modified such that feedback pressure build-up within a feedback chamber of the signal pressure regulating valve is delayed by the provision of a fluid reservoir communicating with a servo actuating fluid supply line and a flow restrictor for restricting flow of hydraulic fluid entering the reservoir. The feedback chamber communicates with the reservoir so that no fluid pressure builds up within the feedback chamber until hydrauic fluid discharged by the pump fills the reservoir. Since the flow rate of hydralic fluid entering the reservoir is restricted by the flow restrictor, the reservoir is left unfilled for a period of time after start-up of the pump and thus feedback pressure does not build up within the feedback chamber for this period of time. Since the signal pressure regulating valve does not effect pressure regulation, a signal fluid pressure unregulated is supplied to the servo actuating fluid pressure regulating valve to help same boost the level of the servo actuating fluid pressure in the servo actuating fluid supply line. BRIEF DESCRIPTION OF THE DRAZIINGS Fig. 1 is a diagram showing a first embodiment; Fig. 2 is a diagram showing a second embodiment; Fig. 3 is a diagram showing a third embodiment; Fig. 4 is a diagram showing a fourth embodiment; Fig. 5 is a diagram showing a fifth embodiment; and Fig. 6 is a diagram showing a sixth embodiment. DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments according to the present invention are described in connection with Figs. I to 6 of the accompanying drawings. (First EmbodiDent) Referring to Fig. 1, there is shown a hydraulic pressure reulating arrangement according to the present invention which includes a pressure regulating valve 10 in the form of a line pressure regulator valve. The line pressure regulator valve 10 is formed with a valve bore 12. Disposed within the valve bore 12 are a pressure responsive valve spool 14, a hollow sleeve 16, a plug 18 that is fit in the hollow sleeve 16, and a spring 22 that acts on the spool 14 to bias same upwardly as viewed in Fig. 1. There are a plurality of ports 12a#12h opening to the valve bore 12. The port 12a is supplied with hydraulic pressure from a pressure modifier valve, not shown, when a predetermined condition is satisfied. The ports 12b, 12c and 12e are connected to a servo actuating fluid supply line leading to a servo motor 2 for a friction device, such as a forward clutch of an automobile automatic transmission. Although, not shown, a manual selector valve operable by a manual shift lever may be fluidly disposed in the servo actuating fluid supply line 26 in a conventional manner. The supply line 26 leads from an pump 24 that is driven by an engine. The pump 24 is operable to pump hydraulic fluid out of a source 4 into the supply line 26. A flow restrictor 20 of the choke type is disposed in a branch line 6 connecting the port 12b with the supply line 26. The restrictor 20 of the choke type has a length which is long in proportion to its flow cross sectional area. A fluid resevoir, in the form of a chamber 60, is provided between the restrictor 20 of the choke type and the port 12b in such a manner that it communicates with the supply line 26 via the restrictor 20 and communicates in an unrestricted manner with the port 12b opening to a feedback chamber 8. The chamber 60 has a predetermined volume. The chamber 60 is provided with a one-way valve 62 via which it is communicable with the ambient atmosphere. The port 12d serves as a discharge port via which hydraulic fluid from the port 12c is supplied to a torque converter, for example, via a torque converter fluid supply line 27. The port 12f serves as a drain port via which hydraulic fluid from the port 12c is drained. The port 12g is connected with a reverse booster line 28 that is supplied with line pressure (servo actuating fluid pressure) when the manual selector valve is set to R-range (reverse drive range). The port 12h is connected with a throttle boost line 29 that is supplied with throttle pressure (signal pressure) variable with engine load. Although, not shown in Fig. 1, the throttle pressure is produced by a throttle pressure by regulating line pressure in response to engine manifold vacuum or throttle position. The spool 14 is formed with a plarality of lands l4a#I4e. The lands 14c, 14d and 14e are the same in diameter. The land 14b is smaller in diameter than they are. The land 14a is smaller in diameter than the land 14b is. Formed between the lands 14a and 14b is a pressure acting area which hydraulic pressure developed in the port 12a acts upon. Formed between the lands 14b and 14c is a feedback pressure acting area which hydraulic pressure in the port 12b acts upon. The sleeve 16 is formed with a step bore which lands 18a and 18b of the plug 18 are slidably fit in. The land 18b is smaller in diameter than the land 18a is. The sleeve 16 is formed with a radial passage 16a via which hydraulic pressure from the port 12h passes to act upon the bottom end face (as viewed in Fig. 1) of the land 18b. It is formed also with another radial passage 16b via which hydraulic pressure from the port 12g passes to act upon a pressure acting area formed between the lands 18a and 18b. The operation of this embodiment is described. It is now assumed that hydraulic pressure at the port 12b is equal to hydraulic pressure at the port 12e. Under this condition, the spool 14 of the regulator valve 10 is subject to hydraulic pressure at the port 12b and that at the port 12a, and urged to move downward as viewed in Fig. 1 against the action of the spring 22. At its spring set position, the spool 14 has its lands 14d and 14e to close the ports 12d and 12f, respectively. An increase in the hydraulic pressure at the port 12b causes a downward movement of the spool 14 against the spring 22, causing the land 14d to open the port 12d and a further increase in the hydraulic pressure at the port 12b causes a further downward movement of the spool 14, causing the land 14e to open the port 12f. The ports 12d and 12f are thus allowed to open to the supply line 26, draining hydraulic fluid and thus causing a reduction in hydraulic pressure in the servo line 26 and also at the port 12b. This reduction in hydraulic pressure causes the spool 14d to move upward under the influence of the spring 22, causing the land 14e to reduce the opening degree of the port 12f and, if this reduction is excessive, causing the land 14d to reduce the opening degree of the port 12d. As a result, an increase in hydraulic pressure takes place. In this manner, the spool 14 regulates hydraulic pressure in the supply line 26 by varying opening degree of the port 12d and opening degree of the port 12f until the total of downward forces resulting from hydraulic pressures at the ports 12a and 12b balance with the total of upward force by the spring 22. The action of the spring 22 is assisted by a line pressure booster including the plug 18. The plug 18 is urged to move upward, as viewed in Fig. 1 as signal pressure (throttle pressure) at the port 12h increases so that an increase in the throttle pressure causes an increase in hydraulic pressure (line pressure) in the supply line 26. The plug 18 is urged to move upward to boost the line pressure also when hydraulic pressure (manual second boost pressure) is applied to the port 12g. Let us now consider the case when all of hydraulic fluid is discharged from the port 12b and also from the chamber 60 which would occur when a considerably long time has past after the pump 24 has ceased its operation. No hydraulic pressure exists at the port 12b under this condition, allowing the spool 14 to assume its spring set position, i.e., its uppermost position, where both of the ports 12d and 12f are closed. When, under this condition, the pump 24 starts operating to discharge hydraulic fluid into the supply line 26, hydraulic fluid flows past the restrictor 20 into the chamber 60 until it fills in the chamber 60. Air displaced by the hydraulic fluid entering the chamber 60 is allowed to escape toward the ambient atmosphere via the one-way valve 62. When the hydraulic fluid fills the chamber 60, the one-way valve 62 is closed. Hydraulic pressure build-up at the port 12b begins after the chamber 60 has been filled with hydraulic fluid. This pressure build-up causes the spool 14 to move downward as viewed in Fig. 1, initiating pressure regulation of hydraulic pressure in the supply line 26. Thus, a considerable period of time passes after the pump 24 is set into its operation until the pressure regulator valve 10 starts effecting pressure regulation by valving the ports 12d and 12f. The length of this time, i.e., a delay, is dependent on the volume of the chamber 60 and the flow rate of fluid flow determined by the size and design of the flow restrictor 20. As mentioned before, the spool 14 stays in the spring set position where discharge of hydraulic fluid via the ports 12d and 12f is prohibited during the delay after the pump 24 starts its operation, so that hydraulic pressure in the supply line 26 is kept at a high level. This high hydraulic pressure forces hydraulic fluid to flow quickly through the supply line 26 no matter how high the viscosity of hydraulic fluid might be, thus quickly filling the associated servo motor 2. As a result, the servo motor 2 is quickly set into operation immediately after the pump 24 starts, actuating the associated friction device to put the transmission into power transferrable state. After bydraulic pressure build-up at the port 12b, the normal pressure regulation is effected by the line pressure regulator valve 10. Since the flow rate of hydraulic fluid passing through the flow restrictor 20 of the choke type drops as the viscosity of hydraulic fluid increases in response to a temperature drop in hydraulic fluid, the period of time during which hydraulic pressure in the supply line 26 is kept high is longer when the temperature is low than the case when the temperature is high. Thus, when the fluid temperature is low, the line pressure regulator valve 10 is set into its pressure regulating states upon expiration of a considerably long time after the pump 24 starts, whereas when the fluid temperature is high or eleveted, this delay is considerably shortened, thus preventing high pressure from existing for an unnecessarily long period of time after the pump 24 starts. (SECOND EMBODIMENT) There is shown in Fig. 2 a second embodiment according to the present invention. This embodiment is substantially the same as Fig. 1 first embodiment, but it is different from the same in that, instaed of delaying pressure build-up, hydraulic pressure in a throttle boost line 29 is temporarily kept high by holding a throttle valve 30 out of its pressure regulating state during a considerable period of time after a pump 24 is set into operation. The throttle valve 30 has in a valve bore 32 thereof a spool 34. The valve bore 32 is provided with a plurality of ports 32a-32d. The port 32b communicates with the throttle pressure boost line 29. Provided between the boost line 29 and the port 32d is a flow restrictor 20 of the choke type. A fluid reservoir in the form of a chamber 60 is provided between the restrictor 20 and the port 32d. The chamber 60 is provided with a one-way valve 61. Supplied to the port 32c is line pressure from a servo actuating fluid supply line 26 via a branch line 42. The port 32a is a drain port. The spool 34 has formed thereon same diameter lands 34a and 34b. Axial length of a groove defined between the lands 34a and 34b is set almost equal to axial distance between the ports 32a and 32c. Pressing force generated by a vacuum diaphragm 50 is applied to the spool 34 via a rod 48. The vacuum diaphragm 50 functions to apply a force that is inversely proportional to engine induction vacuum acting thereon from a vacuum pipe 52 to the rod 48. This construction permits the throttle valve 30 to regulate fluid pressure in the throttle boost line 44 in such a manner as to balance upward force caused by fluid pressure at the port 32d with downward force applied by the rod 48. Since, like the first embodiment, the reservoir 60 and the restrictor 20 of the choke type are used, there occurs a delay in fluid pressure build-up at the port 32d after the pump 24 starts, particularly at low temperatures. Under this condition, the port 32b remains in communication with the port 32c, and thus throttle pressure in the boost line 29 is kept as high as the pressure in the fluid line 42. Since the associated line pressure regulator valve 10 regulates hydraulic pressure in the servo actuating fluid supply line 26 in accordance with this elevated throttle pressure, the hydraulic pressure (line pressure) in the servo actuating fluid supply line 26 is kept high for a considerably long time after the oil pump 24 starts. (THIRb EMBODIMENT) There is shown in Fig. 3 a third embodiment according to the present invention. This third embodiment is substantially the same as Fig. 1 first embodiment except the provision of a flow restrictor 64 in the place of the one-way valve 62 used in the first embodiment. Throttling effect provided by the restrictor 64 is set larger than that provided by the restrictor 20 of the choke type, so the flow rate of fluid passing through the restrictor 64 is less than that passing through the restrictor 20 of the choke type. As a result, although hydraulic fluid flows out of a chamber 60 continuously, this embodiment provides an operation similar to the first embodiment does because the flow rate of fluid passing through the restrictor 64 is considerably less than the flow restrictor 20. After all of hydraulic fluid has been discharged from the chamber 60, when a pump 24 is set into operation, hydraulic fluid is supplied to and fills the chamber 60 via the restrictor 20 although a portion of the fluid is continuously discharged via the restrictor 64. Since the hydraulic fluid is kept supplied to the chamber 60, hydraulic pressure at the port 12b is kept almost as high as that in the servo actuating fluid supply line 26. (FOURTH EMBODIMENT) There is shown in Fig. 4 a fourth embodiment according to the present invention. This embodiment is substantially the same as Fig. 1 first embodiment except the provision of an accumulator 66, as a reservoir, in the place of the chamber 60 and one-way valve 62 used in the first embodiment. In this fourth embodiment, when pump 24 is set into operation under the condition where the accumulator 66 is empty, hydraulic fluid entering the accumulator 66 urges an accumulator piston 66a against a spring 66b. Since the flow rate of hydraulic fluid passing through a restrictor 20 is restricted, it takes a considerably long time until the accumulator 66 is filled with hydraulic fluid after the pump 24 starts. As a result, sufficiently high pressure build-up at a port 12b does not occur during this period of time. (FIFTH EMBODIMENT) There is shown in Fig. 5 a fifth embodiment according to the present invention. This embodiment is substantially the same as the first embodiment except the provision of a long pipe 68 in the place of the fluid chamber 60 used in the first embodiment. This embodiment provides substantially the same effect as the first embodiment does only if volume of the pipe 68 is set equal to that of the chamber 60. (SIXTH EMBODIMENT) There is shown in Fig. 6 a sixth embodiment according to the present invention. This sixth embodiment is substantially the same as Fig. 3 third embodiment except the provision of a long tube 68 in the place of the oil chamber 60 used in the third embodiment. If provides substantially the same effect as the third embodiemnt does only if volume of the pipe 68 is set equal to that of the chamber 60 of the third embodiment. In each of the previously described embodiments, a restrictor of the choke type is used, but a restrictor of the orifice type may be used instead. However, the restrictor of the oriffice type cannot elongate the amount of delay in delivery of a feedback fluid pressure as fluid temperature drops. Thus, high hydraulic pressure is maintained even at low temperature for substantially the same long time as is provided at high temperature.

Claims: WHAT IS CLAIMED IS: 1. A hydraulic pressure regulating arrangement for generating a servo actuating fluid pressure under which hydraulic fluid is supplied to a servo motor, comprising: a source of hydraulic fluid with temperature dependent viscosity; means defining a servo actuating fluid supply line leading to the servo motor; pump means for pumping hydraulic fluid out of said source into said servo actuating fluid supply line; a pressure regulating valve having a drain port opening to said servo actuating fluid supply line, a feedback chamber communicating with said servo actuating fluid supply line, and pressure responsive means for valving said drain port responsive to hydraulic fluid pressure within said feedback chamber; means for defining a reservoir communicating with said servo actuating fluid supply line and capable of receiving a predetermined volume of hydraulic fluid; ; a flow restrictor means fluidly disposed between said reservoir and said servo actuating fluid supply line for restricting flow of hydraulic fluid entering said reservoir; and means for causing said pressure responsive means to reduce opening degree of said drain port until said reservoir is filled with said hydraulic fluid, thereby to allow high servo actuating fluid pressure to build up in said servo actuating fluid supply line. 2. A hydraulic pressure regulating arrangement as claimed in claim 1, wherein said causing means includes means for establishing fluid communication between said feedback chamber and said reservoir. 3. A hydraulic pressure regulating arrangement as claimed in claim 2, wherein said reservoir includes a hydraulic fluid chamber establishing communication with the ambient atmosphere, and one-way valve means for controlling said communication. 4. A hydraulic pressure regulating arrangement as claimed in claim 3, wherein said flow restrictor means is of the choke type. 5. A hydraulic pressure regulating arrangement as claimed in claim 1, wherein said causing means includes: a signal pressure regulating valve having an inlet port communicating with said servo actuating fluid supply line, an outlet port, and a fluid passage connecting said inlet port with said outlet port, a feedback chamber, and pressure responsive means for leaving said fluid passage open responsive to hydraulic fluid pressure within said feedback chamber of said signal pressure regulating valve below a predetermined value; said reservoir communicating with said servo actuating fluid supply line via said outlet port, said fluid passage, and said inlet port of said signal pressure regulating valve means, said reservoir communicating with said feedback chamber of said signal pressure regulating valve means; ; said flow restrictor means fluidly disposed between said reservoir and said outlet port of said signal pressure regulating valve, and wherein said causing means also includes: booster means communicating with said outlet port of said signal pressure regulating valve for urging said pressure responsive means of said pressure regulating valve to close said drain port in response to hydraulic pressure at said outlet port of said signal pressure regulating valve. 6. A hydraulic pressure regulating arrangement as claimed in claim 5, wherein said signal pressure regulating valve includes actuator means responsive to loading on the engine for biasing said pressure responsive means of said signal pressure regulating valve. 7. A hydraulic pressure regulating arrangement as claimed in claim 6, wherein said booster means includes an end plug formed with a pressure acting area which is subject to hydraulic fluid pressure at said outlet port of said signal pressure regulating valve, said end plug being movable to act on said pressure responsive means of said pressure regulating valve. 8. A hydraulic pressure regulating arrangement as claimed in claim 7, wherein said reservoir includes a hydraulic fluid chamber establishing communication with the ambient atmosphere, and one-way valve means for controlling said communication. 9. A hydraulic pressure regulating arrangement as claimed in claim 8, wherein said flow restrictor means is of the choke type. 10. A hydraulic pressure regulating arrangement as claimed in claim 2, wherein said reservoir includes a hydraulic fluid chamber establishing communication with the ambienst atmosphere, and a second flow restrictor means fluidly disposed in said communication, and wherein said second flow restrictor means provides throttling effect larger than said first mentioned flow restrictor means does. 11. A hydraulic pressure regulating arrangement as claimed in claim 10, wherein said first mentioned flow restrictor means is of the choke type and said second flow restrictor means is of the orifice type. 12. A hydraulic pressure regulating arrangement as claimed in claim 2, wherein said reservoir includes an accumulator. 13. A hydraulic pressure regulating arrangement as claimed in claim 12, wherein said flow restrictor means is of the choke type. 14. A hydraulic pressure regulating arrangement as claimed in claim 2, wherein said reservoir includes a tube having one end communicating with the ambient atmosphere, and one-way valve means for controlling communication. 15. A hydraulic pressure regulating arrangement as claimed in claim 14, wherein said flow restrictor means is of the chock type. 16. A hydraulic pressure regulating arrangement as claimed in claim 2, wherein said reservoir includes a tube having one end communicating with the ambient atmosphere, and a second flow restrictor means fluidly disposed in said communication, and wherein said second flow restrictor means provides throttle effect larger than said first mentioned flow restrictor means does. 17. In an automatic transmission for a motor vehicle having an engine, the automatic transmission having a servo motor: a source of hydraulic fluid with temperature dependent viscosity; a pump driven by the engine for pumping hydraulic fluid out of said source and discharging hydraulic fluid; means for defining a servo actuating fluid supply line leading from said pump to said hydraulic servo; ; a pressure regulating valve having a drain port opening to said hydraulic fluid passage, a feedback chamber communicating with said hydraulic fluid passage, a spool means, and a resilient means for biasing said spool means to a position where said spool means closes said drain port, said spool means having a pressure acting area subjected to hydraulic fluid pressure within said feedback chamber to be urged against said resilient means in a direction to increase opening degree of said drain port; means for defining a reservoir capable of receiving a predetermined volume of hydraulic fluid, said reservoir communicating with said servo actuating fluid supply line; a flow restrictor means fluidly disposed between said reservoir and said hydraulic servo actuating fluid supply line for restricting flow of hydraulic fluid entering said reservoir; and means for causing said spool means to stay in said position where said spool means closes said drain port until said reservoir is filled with hydraulic fluid.

Inventors: SHIBAYAMA, TAKASHI, SUGANO, KAZUHIKO, UEKI, AKIHIRO
Applicants: NISSAN MOTOR CO., LTD.
Application year: 1985
Main classification: F15B21
IPC codes: F16H61, G05D16