Abstract:
A manual valve of a hydraulic pressure control system for an automatic transmission includes: a valve body that includes an input port and two reverse range pressure supply ports for supplying a hydraulic pressure from the input port to two friction elements; and a valve spool that is disposed in the valve body and that is connected to a select lever, wherein at least one exhaust passage is formed on a land of the valve spool that opens/closes the two reverse range pressure supply ports of the valve body.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority to and the benefit of Korean Patent Application No. 10-2005-0123173 filed in the Korean Intellectual Property Office on Dec. 14, 2005, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     (a) Field of the Invention  
         [0003]     The present invention relates to a manual valve that is applied to a hydraulic pressure control system of an automatic transmission for a vehicle. More particularly, the present invention relates to a manual valve that optimally controls an automatic transmission fluid (ATF) that is exhausted when the vehicle is shifted from reverse to neutral in various circumstances, such as at very low temperatures and at room temperature.  
         [0004]     (b) Description of the Related Art  
         [0005]     In general, automatic transmissions control a plurality of solenoid valves based on speed of the vehicle and throttle valve opening, etc., so as to control a hydraulic pressure. Accordingly, since a shift gear of a target shift range is moved by the hydraulic pressure, shifting occurs automatically.  
         [0006]     If a driver moves a select lever into a desired shift range, ports of the manual valve of the hydraulic pressure control system are changed such that the hydraulic pressure is supplied from a hydraulic pump to a plurality of operational elements, which are operated by the hydraulic pressure. In particular, such operational elements are selectively operated according to the duty cycles of the solenoid valves, such that the shift is accomplished.  
         [0007]     In a conventional manual valve, hydraulic pressure is exhausted only through exhaust ports when the vehicle is shifted from reverse to neutral. Accordingly, since release pressure is not controlled, the following problems may occur:  
         [0008]     Since release time of a reverse range pressure is not controlled, the hydraulic pressure is always exhausted through the exhaust ports in the same way despite different circumstances, which include at room temperature, when viscosity of a transmission fluid is low, and at very low temperatures, when viscosity of the transmission fluid is high.  
         [0009]     At room temperature when viscosity of the transmission fluid is low, since the transmission fluid is exhausted quickly, shift shock may occur. At very low temperatures when the viscosity of the transmission fluid is high, since exhaust time of the transmission fluid is extended, that is, since a release of a friction element is insufficient, the vehicle may unintentionally reverse.  
         [0010]     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention provides a manual valve of a hydraulic pressure control system for an automatic transmission that optimally controls automatic transmission fluid (ATF) that is exhausted when the vehicle is shifted from reverse to neutral in various circumstances, such as at very low temperatures and at room temperature.  
         [0012]     An exemplary embodiment of the present invention provides a manual valve of a hydraulic pressure control system for an automatic transmission that includes a valve body that includes an input port and two reverse range pressure supply ports for supplying a hydraulic pressure from the input port to two friction elements; and a valve spool that is disposed in the valve body and connected to a select lever, wherein at least one exhaust passage is disposed on a land that opens/closes the two reverse range pressure supply ports. The at least one exhaust passage may include first and second exhaust passages.  
         [0013]     The first exhaust passage may include a radial hole connecting a first principal groove to a second principal groove, wherein the first and second principal grooves are formed on surfaces of a land that is disposed at the same position as the two reverse range pressure supply ports when a reverse range is selected; and an axial hole that communicates a middle portion of the radial hole with an exterior.  
         [0014]     The second exhaust passage may include an exhausting groove that is formed on a surface of the land between the first and second principal grooves, and that is disposed along the axial direction of the valve spool. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a circuit diagram showing a hydraulic control system of an automatic transmission according to an exemplary embodiment of the present invention;  
         [0016]      FIG. 2  is a perspective view showing a valve spool according to an exemplary embodiment of the present invention;  
         [0017]      FIG. 3  is a cross-sectional view taken along the line III-III in  FIG. 2 ;  
         [0018]      FIG. 4  is a cross-sectional view taken along the line IV-IV in  FIG. 2 ; and  
         [0019]      FIG. 5  is a cross-sectional view showing a manual valve of a hydraulic control system of an automatic transmission according to an exemplary embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings.  
         [0021]      FIG. 1  shows a hydraulic pressure system for explaining an applied state of a manual valve according to an exemplary embodiment of the present invention. The manual valve of the present invention can be applied to not only the hydraulic pressure system as shown in  FIG. 1 , but also to all hydraulic control systems to which an N-D control valve is applied.  
         [0022]     An exemplary hydraulic control system, to which the manual valve of the present invention is applied, will be hereinafter described with reference to  FIG. 1 . Hydraulic pressure, which is generated from a hydraulic pump  2 , is supplied into a pressure regulating valve  4 , a torque converter control valve  6 , a damper clutch control valve  8 , etc.  
         [0023]     In addition, a first predetermined portion of the hydraulic pressure is supplied into a reducing valve  10  and a manual valve  12 , and then the hydraulic pressure is reduced through the reducing valve  10 . A second predetermined portion of the reduced hydraulic pressure is supplied into a first pressure control valve  14  and a second pressure control valve  16  so as to be converted into a control pressure of the shift range.  
         [0024]     While the second predetermined portion of the reduced hydraulic pressure is supplied into the first and second pressure control valves  14  and  16 , a third predetermined portion thereof is supplied into an N-R control valve  18 . In addition, when the manual valve  12  has a drive D range state, a shift control valve  22 , which converts a passage according to a control of a first solenoid valve S 1  and a second solenoid valve S 2 , is connected to a line  20  in which the hydraulic pressure moves, such that the shift control valve  22  performs a shift control with the manual valve  12 .  
         [0025]     A first speed line  24  branches from the line  20 . In addition, the line  20  is connected with the first and second pressure control valves  14  and  16 , which are controlled by third and fourth solenoid valves S 3  and S 4 , through the first speed line  24  so as to receive a shift control pressure.  
         [0026]     A second speed line  26 , a third speed line  28 , and a fourth speed line  30  are connected to the shift control valve  22 . In detail, the second speed line  26  is connected with a 1-2 shift valve  32 , a control switching valve  34 , and a fail-safe valve  36 . The third speed line  28  branches into first and second branch lines  38  and  40 , the first branch line  38  being connected with a 2-3/4-3 shift valve  42  and the second branch line  40  supplying the hydraulic pressure into the control switching valve  34  and an end clutch valve  44 .  
         [0027]     In addition, the fourth speed line  30  connects a rear clutch release valve  46  to the 2-3/4-3 shift valve  42 , and one portion of the fourth speed line  30  supplies the hydraulic pressure into the pressure regulating valve  4  through a high-low pressure valve  48  such that a line pressure is regulated.  
         [0028]     A timing control pressure line  50  of the manual valve  12  connects the control switching valve  34  to the high-low pressure valve  48  so as to be controlled by a fifth solenoid valve S 5 .  
         [0029]     In addition, when the manual valve  12  has a reverse R range state, while the hydraulic pressure is supplied into a first reverse control line  52 , the hydraulic pressure is supplied into a front clutch C 4  and a release side chamber of a kick down servo C 2  through a rear clutch release valve  46  and the 2-3/4-3 shift valve  42 , and is simultaneously supplied as a control pressure to the fail-safe valve  36 .  
         [0030]     While the hydraulic pressure is supplied into a second reverse control line  54 , the hydraulic pressure is supplied into a low-reverse brake C 5  through the N-R control valve  18  and the 1-2 shift valve  32 .  
         [0031]     An exemplary manual valve  12 , which can be applied to the above-mentioned or other hydraulic control systems, is shown in FIGS.  2  to  4 . A valve spool  60 , as shown in  FIG. 2 , includes a connecting part  61 , which is configured to be connected to the select lever of a driver&#39;s seat (not shown), and first, second, and third lands  62 ,  63 , and  64 . Lands  62 - 64  are formed apart from each other by predetermined gaps according to a port design of the valve body.  
         [0032]     In addition, an exhaust hole (not shown) is disposed on the valve spool  60  from an end portion of the connecting part  61  to a portion between the first and second lands  62  and  63 , an interior end portion of the exhaust hole is radially connected with an intake hole  65  in the valve spool  60 , so that a transmission fluid that flows into the intake hole  65  is exhausted through the exhaust hole and an orifice  66 .  
         [0033]     An exemplary valve body in which the valve spool  60  is inserted, as shown in  FIG. 5 , includes a first port  70  that receives the hydraulic pressure supplied from the hydraulic pump, a second port  71  that supplies the hydraulic pressure from the first port  70  to the timing control pressure line  50 , a third port  72  that supplies the hydraulic pressure as control pressure from the first port  70  to the regulator valve  4 , a fourth port  73  that supplies the hydraulic pressure from the first port  70  to the shift control valve  22 , and fifth and sixth ports  74  and  75  that supply the hydraulic pressure from the first port  70  to the first and second reverse pressure lines  52  and  54  when a reverse R range is selected.  
         [0034]     Accordingly, the hydraulic pressure, which is always generated when an engine is running, is first supplied into the first port  70 . In the park P range, the supplied hydraulic pressure is exhausted through the intake hole  65  and the orifice  66 , while in the reverse R range, the supplied hydraulic pressure is supplied into the fifth and sixth ports  74  and  75 . Further, in the neutral N range, the supplied hydraulic pressure is supplied into the second port  71  and the third port  72 , and in the drive D range, the supplied hydraulic pressure is supplied into the second, third, and fourth ports  71 ,  72 , and  73 .  
         [0035]     In such a manual valve  12 , the third land  64  has a predetermined width such that the fourth and fifth ports  74  and  75  can be fully accommodated.  
         [0036]     A first exhaust passage may be formed as follows: First and second principal grooves  80  and  81  ( FIGS. 2 and 3 ) with a first predetermined depth are formed on a periphery of a middle portion of the third land  64  such that they are disposed at the same positions as the fourth and fifth ports  74  and  75  ( FIG. 5 ) when the neutral N range is selected. Furthermore, the first and second principal grooves  80  and  81  are respectively positioned to upper and lower portions of the periphery of the third land  64 . The principal grooves  80  and  81  communicate with each other by a radial hole  82 , which is opened to an exterior by an axial hole  83 .  
         [0037]     Accordingly, when the reverse R range is shifted into the neutral N range, the transmission fluid, which is supplied into the fifth and sixth ports  74  and  75 , is exhausted through holes  82  and  83  of the principal grooves  80  and  81 .  
         [0038]     Further, a second exhaust passage may be formed as follows. First and second exhausting grooves  84  and  85  ( FIGS. 2 and 4 ) with a second predetermined depth are disposed on a periphery of the third land  64  along the axial direction of the valve spool  60 . Furthermore, each inner side end (i.e., an inner surface that is toward the second land  63 , in an inner surface of the exhausting grooves) thereof is disposed at the same axial position as the middle portions of the first and second principal grooves  80  and  81 , and each exterior side end (i.e., a portion that is outward with respect to the axial direction of the valve spool  60 ) thereof is open.  
         [0039]     Accordingly, when the reverse R range is shifted into the neutral N range, the transmission fluid, which is supplied into the fifth and sixth ports  74  and  75 , is exhausted through holes  82  and  83  of the principal grooves  80  and  81 , and is also exhausted through the first and second exhausting grooves  84  and  85  at the same time.  
         [0040]     The sizes of the holes  82  and  83  and the exhausting grooves  84  and  85  are predetermined according to a design rule of the automatic transmission.  
         [0041]     While it has been explained that each inner side end of the exhausting grooves  84  and  85  is disposed at about the same axial position as the middle portions of the principal grooves  80  and  81 , each inner side end of the exhausting grooves  84  and  85  may be closer to the second land  63 , or may be closer to each outer side end of the exhausting grooves  84  and  85 .  
         [0042]     If each inner side end of the exhausting grooves  84  and  85  is closer to the second land  63 , since the exhausting grooves  84  and  85  are large, the release time is shortened. In addition, if each inner side end is closer to each outer side end of the exhausting grooves  84  and  85 , since the exhausting grooves  84  and  85  are small, the release time is delayed. Accordingly, the position of each inner side end may be predetermined according to characteristics of the automatic transmission.  
         [0043]     The above-mentioned manual valve  12  has a state like  FIG. 5  in the neutral N range state, in which the transmission fluid, which is supplied through the fifth and sixth ports  74  and  75 , is exhausted through the holes  82  and  83  of the principal grooves  80  and  81 , and is exhausted through the exhausting grooves  84  and  85  at the same time.  
         [0044]     An exhaust of the transmission fluid is governed by each size of the holes  82  and  83  and the exhausting grooves  84  and  86 . Accordingly, each size may be predetermined such that the release time has a range in which shift shock is not generated when the reverse R range is shifted into the neutral N range.  
         [0045]     At low temperatures when viscosity of the transmission fluid is high, if a driver moves the select lever (not shown) a little toward the drive D range, the valve spool  60  moves toward the drive D range, and the size of the exhausting grooves  84  and  85  is enlarged, and as a result the release time is fast.  
         [0046]     In addition, at very low temperatures (about  30  degrees below zero), if the third solenoid valve S 3  is controlled such that a valve spool of the N-R control valve  18  is moved to the right in  FIG. 1 , an exhausting port EX is opened, and accordingly, the transmission fluid is directly exhausted from the N-R control valve  18  without being exhausted through the manual valve  12 .  
         [0047]     As has been explained, according to the present invention, regardless of temperature, the exhaust of automatic transmission fluid (ATF) can be controlled when the reverse R range is shifted into the neutral N range. As a result, shift shock is prevented.  
         [0048]     In addition, according to the present invention, even though the viscosity of the transmission fluid is high in a state of very low temperature, the release time can be shortened. As a result, accidents due to a release deficiency of a reverse frictional element can be prevented.  
         [0049]     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.