Abstract:
A hydraulic pressure supply system of an automatic transmission for a vehicle may include a hydraulic pump receiving oil stored in an oil pan through an input line, generating hydraulic pressure, and discharging the generated hydraulic pressure in the oil through a low-pressure discharge port and a high-pressure discharge port, a first switch valve switching a first switch hydraulic line in order to supply the hydraulic pressure discharged from the low-pressure discharge port of the hydraulic pump selectively to the low pressure portion or the high pressure portion, a second switch valve switching a second switch hydraulic line in order to selectively supply the hydraulic pressure supplied from the first switch valve to the low pressure portion or to return the hydraulic pressure supplied from the first switch valve to the oil pan, a low-pressure regulator valve, and a high-pressure regulator valve.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2013-0158824 filed Dec. 18, 2013, the entire contents of which is incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a hydraulic pressure supply system of an automatic transmission for a vehicle. More particularly, the present invention relates to a hydraulic pressure supply system of an automatic transmission for a vehicle that supplies necessary pressure to a necessary portion by using a mechanical hydraulic pump having a low-pressure discharge port and a high-pressure discharge port, and minimizes driving loss of the hydraulic pump and improves fuel economy by returning unnecessary hydraulic pressure. 
     2. Description of Related Art 
     Recently, vehicle makers direct all their strength to improve fuel economy due to worldwide high oil prices and strengthening of exhaust gas regulations. 
     Improvement of fuel economy may be achieved by improving power delivery efficiency, and the improvement of the power delivery efficiency may be achieved by minimizing unnecessary power consumption of a hydraulic pump. 
     A recent automatic transmission is provided with a low-pressure hydraulic pump and a high-pressure hydraulic pump so as to improve fuel economy. Therefore, hydraulic pressure generated by the low-pressure hydraulic pump is supplied to a low pressure portion (i.e., a torque converter, a cooling device, and a lubrication device), and hydraulic pressure generated by the high-pressure hydraulic pump is supplied to a high pressure portion (i.e., friction members selectively operated when shifting). 
     In further detail, general hydraulic pressure of the automatic transmission is generated for the low pressure portion (i.e., generated by the low-pressure hydraulic pump), and hydraulic pressure demanded by the high pressure portion is generated by the high-pressure hydraulic pump and then is supplied to the high pressure portion. 
     Therefore, fuel economy may be improved by minimizing power consumption for driving the hydraulic pump, and noise and vibration may be reduced and durability may be improved by reducing load applied to the hydraulic pump. 
     In the hydraulic pressure supply system, the low-pressure hydraulic pump and the high-pressure hydraulic pump are driven by one drive shaft, or the low-pressure hydraulic pump is driven by driving torque of an engine and the high-pressure hydraulic pump is driven by driving torque of a motor. 
     If both of the low-pressure hydraulic pump and the high-pressure hydraulic pump are used, structure of the automatic transmission may be complex and weight may be increased. 
     In addition, if two hydraulic pumps are used, manufacturing cost may increase and mountability may be deteriorated. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
     BRIEF SUMMARY 
     Various aspects of the present invention are directed to providing a hydraulic pressure supply system of an automatic transmission for a vehicle having advantages of supplying necessary pressure to a necessary portion by using a mechanical hydraulic pump having a low-pressure discharge port and a high-pressure discharge port, and minimizing driving loss of the hydraulic pump and improving fuel economy by returning unnecessary hydraulic pressure. 
     A hydraulic pressure supply system of an automatic transmission for a vehicle which generates a low hydraulic pressure and a high hydraulic pressure using oil stored in an oil pan and supplies the low hydraulic pressure and the high hydraulic pressure to a low pressure portion and a high pressure portion respectively, may include a hydraulic pump receiving the oil stored in the oil pan through an input line, generating hydraulic pressure, and discharging the generated hydraulic pressure through a low-pressure discharge port and a high-pressure discharge port, a first switch valve switching a first switch hydraulic line in order to supply the hydraulic pressure discharged from the low-pressure discharge port of the hydraulic pump selectively to the low pressure portion or the high pressure portion, a second switch valve switching a second switch hydraulic line in order to selectively supply the hydraulic pressure supplied from the first switch valve to the low pressure portion or to return the hydraulic pressure supplied from the first switch valve to the oil pan, a low-pressure regulator valve regulating the hydraulic pressure supplied from the second switch valve to be stable and supplying the regulated hydraulic pressure to the low pressure portion, and a high-pressure regulator valve regulating the hydraulic pressure supplied from the high-pressure discharge port of the hydraulic pump to be stable, supplying the regulated hydraulic pressure to the high pressure portion, and selectively supplying a portion of the hydraulic pressure supplied from the high pressure discharge port to the low-pressure regulator valve. 
     An upstream of the first switch valve may be connected to a first low-pressure line connected to the low-pressure discharge port of the hydraulic pump, and a downstream of the first switch valve may be connected to a second low-pressure line and a first bypass line connected to the high-pressure regulator valve. 
     The first switch valve may be controlled by hydraulic pressure returned from the high-pressure regulator valve and elastic force of a first elastic member counteracting against the returned hydraulic pressure. 
     An upstream of the second switch valve may be connected to the first switch valve through the second low-pressure line, and a downstream of the second switch valve may be connected to a third low-pressure line and a second recirculation line. 
     The second switch valve may be controlled by the hydraulic pressure returned from the high-pressure regulator valve and elastic force of a second elastic member counteracting against the returned hydraulic pressure. 
     The second switch valve may switch the second switch hydraulic line at a higher pressure than the first switch valve switches the first switch hydraulic line. 
     The low-pressure regulator valve may be connected to the second switch valve through a third low-pressure line, may recirculate a portion of the hydraulic pressure supplied from the third low-pressure line through a first recirculation line to regulate the hydraulic pressure of the third low-pressure line to be stable, and may supply the regulated hydraulic pressure to the low pressure portion. 
     The first recirculation line may be connected to the input line. 
     The low-pressure regulator valve may be controlled by the hydraulic pressure supplied to the low pressure portion, and a control pressure of a first solenoid valve and elastic force of a third elastic member counteracting against the hydraulic pressure of the low pressure portion. 
     The high-pressure regulator valve may recirculate a portion of the hydraulic pressure supplied through a high-pressure line from the high-pressure discharge port of the hydraulic pump through a second recirculation line so as to regulate the hydraulic pressure of the high-pressure line to be stable, and may supply the regulated hydraulic pressure to the high pressure portion and to the low-pressure regulator valve selectively through a second bypass line. 
     An orifice may be disposed on the second recirculation line, and first and second control pressure lines may be bifurcated from the second recirculation line at an upstream of the orifice so as to supply a control pressure respectively to the first and second switch valves. 
     The high-pressure regulator valve may be controlled by the hydraulic pressure supplied to the high pressure portion, and a control pressure of a second solenoid valve and elastic force of a fourth elastic member counteracting against the hydraulic pressure of the high pressure portion. 
     It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an exemplary hydraulic pressure supply system according to the present invention. 
         FIG. 2  is a schematic diagram of the exemplary hydraulic pressure supply system illustrating that hydraulic pressure is not sufficiently supplied to a high pressure portion according to the present invention. 
         FIG. 3  is a schematic diagram of the exemplary hydraulic pressure supply system illustrating that hydraulic pressure is sufficiently supplied to a high pressure portion according to the present invention. 
         FIG. 4  is a schematic diagram of the exemplary hydraulic pressure supply system illustrating that excessive hydraulic pressure is supplied to a high pressure portion and a low pressure portion according to the present invention. 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
       FIG. 1  is a schematic diagram of a hydraulic pressure supply system according to various embodiments of the present invention. 
     Referring to  FIG. 1 , a hydraulic pressure supply system according to various embodiments of the present invention is adapted to supply a low hydraulic pressure discharged through a low-pressure discharge port  4  of a hydraulic pump  2  to a low pressure portion  6  such as a torque converter (T/C), a cooling portion, and a lubrication portion and to supply high hydraulic pressure discharged through a high-pressure discharge port  8  of the hydraulic pump  2  to a high pressure portion  10  for operating friction members related to shifting. 
     The low hydraulic pressure is a lower pressure facilitating operation of the torque converter (T/C) and cooling and lubrication, and the high hydraulic pressure is a high pressure facilitating operation of a plurality of friction members. 
     The low hydraulic pressure discharged through the low-pressure discharge port  4  of the hydraulic pump  2  is supplied to the low pressure portion  6  through a first low-pressure line  14 , a first switch valve  16 , a second low-pressure line  18 , a second switch valve  20 , a third low-pressure line  22 , and a low-pressure regulator valve  24 . 
     The high hydraulic pressure discharged through the high-pressure discharge port  8  of the hydraulic pump  2  is supplied to the high pressure portion  10  through a high-pressure line  26  and a high-pressure regulator valve  28 . 
     In addition, the low hydraulic pressure discharged through the low-pressure discharge port  4  is selectively supplied to the high pressure portion  10  through a first bypass line  30  connecting the first switch valve  16  to the high-pressure line  26 , and a portion of the high hydraulic pressure discharged through the high-pressure discharge port  8  is supplied to the low pressure portion  6  through a second bypass line  32  connecting the high-pressure regulator valve  28  to the third low-pressure line  22 . 
     In addition, a portion of the hydraulic pressure supplied to the low-pressure regulator valve  24  is recirculated to the input line  12  through a first recirculation line  34 , and a portion of the hydraulic pressure supplied to the high-pressure regulator valve  28  is recirculated to the input line  12  through a second recirculation line  36  and is supplied to the first and second switch valves  16  and  20  through first and second control pressure lines  38  and  40  as control pressures respectively. 
     The hydraulic pressure supply system according to various embodiments of the present invention will be described in further detail. 
     The hydraulic pump  2  is a gear pump that receives oil from an oil pan P through the input line  12  and discharges the oil through two paths, for example through the low-pressure discharge port  4  and the high-pressure discharge port  8 . The hydraulic pump  2  is driven by an engine. 
     The first switch valve  16  is a spool valve and is configured to supply the hydraulic pressure discharged from the low-pressure discharge port  4  selectively to the low pressure portion  6  or the high pressure portion  10 . 
     For this purpose, an upstream of the first switch valve  16  is connected to the first low-pressure line  14  connected to the low-pressure discharge port  4  of the hydraulic pump  2 , and a downstream of the first switch valve  16  is connected to the second low-pressure line  18  and the first bypass line  30 , 
     In addition, the first switch valve  16  is controlled by a control pressure supplied from the high-pressure regulator valve  28  through the first control pressure line  38  and elastic force of an elastic member  42  counteracting against the control pressure so as to supply the hydraulic pressure supplied from the hydraulic pump  2  through the first low-pressure line  14  selectively to the second low-pressure line  18  or the first bypass line  30 . 
     The second switch valve  20  supplies the hydraulic pressure supplied from the first switch valve  16  to the low-pressure regulator valve  24  until the hydraulic pressure of the high pressure portion  10  reaches a target hydraulic pressure, and returns the hydraulic pressure supplied from the first switch valve  16  to the input line  12  if the hydraulic pressure of the high pressure portion  10  is greater than the target hydraulic pressure. 
     For this purpose, an upstream of the second switch valve  20  is connected to the second low-pressure line  18  and a downstream of the second switch valve  20  is connected to the third low-pressure line  22  and the second recirculation line  36 . 
     In addition, the second switch valve  20  is controlled by the hydraulic pressure supplied from the high-pressure regulator valve  28  through the second control pressure line  40  and elastic force of the elastic member  44  counteracting against the hydraulic pressure so as to supply the hydraulic pressure supplied from the hydraulic pump  2  through the first low-pressure line  14  and the first switch valve  16  selectively to the third low-pressure line  22  or the second recirculation line  36 . 
     The elastic force of the elastic member  42  used in the first switch valve  16  is smaller than that of the elastic member  44  used in the second switch valve  20 . 
     Therefore, the first and second switch valves  16  and  20  stay at initial positions thereof if the control pressure supplied to the first and second control pressure lines  38  and  40  is smaller than the elastic force of the elastic member  42  used in the first switch valve  16 . The first switch valve  16  switches a hydraulic line and the second switch valve  20  stays at the initial position thereof if the control pressure supplied to the first and second control pressure lines  38  and  40  is greater than the elastic force of the elastic member  42  used in the first switch valve  16  and is smaller than the elastic force of the elastic member used in the second switch valve  20 . The first and second switch valves  16  and  20  switch hydraulic lines if the control pressure supplied to the first and second control pressure lines  38  and  40  is greater than the elastic force of the elastic member  44  used in the second switch valve  20 . 
     The low-pressure regulator valve  24  regulates the hydraulic pressure supplied from the second switch valve  20  and supplies the regulated hydraulic pressure to the low pressure portion  6 . 
     In addition, the low-pressure regulator valve  24  is controlled by the hydraulic pressure supplied to the low pressure portion  6 , and elastic force of an elastic member  46  and a control pressure of a first solenoid valve SOU counteracting against the hydraulic pressure so as to regulate the low hydraulic pressure to be stable, supply the regulated hydraulic pressure to the low pressure portion  6 , and recirculate remaining hydraulic pressure to the input line  12  through the first recirculation line  34 . 
     The high-pressure regulator valve  28  regulates the hydraulic pressure supplied from the high-pressure line  26  and supplies the regulated hydraulic pressure to the high pressure portion  10 . 
     In addition, the high-pressure regulator valve  28  is controlled by the hydraulic pressure supplied to the high pressure portion  10 , and elastic force of an elastic member  48  and a control pressure of a second solenoid valve SOL 2  counteracting against the hydraulic pressure so as to regulate the high hydraulic pressure to be stable, supply the regulated hydraulic pressure to the high pressure portion  10 , supply a portion of the regulated hydraulic pressure to the third low-pressure line  22  through the second bypass line  32 , and recirculate remaining hydraulic pressure to the input line  12  through the second recirculation line  36 . 
     An orifice OR is disposed on the second recirculation line  36 , and the first and second control pressure lines  38  and  40  are bifurcated from an upstream of the orifice OR. 
       FIG. 2  is a schematic diagram of the hydraulic pressure supply system illustrating that hydraulic pressure is not sufficiently supplied to a high pressure portion according to the present invention. 
     Referring to  FIG. 2 , hydraulic lines are formed to supply the hydraulic pressure generated by the hydraulic pump  2  to the high pressure portion  10  at an initial starting of the engine. 
     That is, the first switch valve  16  connects the first low-pressure line  14  to the first bypass  30  and the second switch valve  20  connects the second low-pressure line  18  to the third low-pressure line  22  at the initial starting of the engine. 
     In this case, the hydraulic pressure discharged through the low-pressure and high-pressure discharge ports  4  and  8  of the hydraulic pump  2  is supplied to the high pressure portion  10  through the high-pressure regulator valve  28 . 
     Therefore, the hydraulic pressure of the high pressure portion  10  can reach a target hydraulic pressure quickly and shift responsiveness may be improved. 
     At this time, a portion of the hydraulic pressure supplied to the high-pressure regulator valve  28  may be supplied to the low pressure portion  6  through the second bypass line  32 . 
       FIG. 3  is a schematic diagram of the hydraulic pressure supply system illustrating that hydraulic pressure is sufficiently supplied to a high pressure portion according to the present invention. 
     Referring to  FIG. 3 , if the hydraulic pressure of the high pressure portion  10  reaches the target hydraulic pressure and the hydraulic pressure of the second recirculation line  36  wins against the elastic force of the elastic member  42  of the first switch valve  16 , the first switch valve  16  disconnects the first low-pressure line  14  and the first bypass line  30  and connects the first low-pressure line  14  and the second low-pressure line  18 . 
     In this case, the hydraulic pressure discharged through the low-pressure discharge port  4  is supplied to the low pressure portion  6  through the first and second switch valves  16  and  20  and the low-pressure regulator valve  24 , and the hydraulic pressure discharged from the high-pressure discharge port  8  is supplied to the high pressure portion  10 . 
     If the hydraulic pressure of the high pressure portion  10  reaches the target hydraulic pressure, driving torque of the hydraulic pump  2  may be lowered by supplying the hydraulic pressure discharged through the low-pressure discharge port  4  to the low pressure portion  6 . 
       FIG. 4  is a schematic diagram of a hydraulic pressure supply system illustrating that excessive hydraulic pressure is supplied to a high pressure portion and a low pressure portion according to various embodiments of the present invention. 
     Referring to  FIG. 4 , the hydraulic pressure of the high pressure portion  10  is greater than the target hydraulic pressure due to rise of engine speed and the hydraulic pressure of the second recirculation line  36  wins against the elastic force of the elastic member  44  of the second switch valve  20 , the second switch valve  20  disconnects the second low-pressure line  18  and the third low-pressure line  22  and connects the second low-pressure line  18  and the second recirculation line  36 . 
     Therefore, the hydraulic pressure discharged through the low-pressure discharge port  4  is returned to the input line  12  through the first and second switch valves  16  and  20  and the second recirculation line  36 . 
     In addition, the hydraulic pressure discharged through the high-pressure discharge port  8  is supplied to the high pressure portion  10  and is supplied to the low pressure portion  6  through the high-pressure regulator valve  28  and the second bypass line  32 . 
     If the hydraulic pressure is excessively supplied to the high pressure portion  10 , the hydraulic pressure discharged through the low-pressure discharge port  4  is returned to the input line  12  and the hydraulic pressure discharged through the high-pressure discharge port  4  is supplied to the high pressure portion  10  and the low pressure portion  6 . Therefore, capacity of the hydraulic pump  2  may be reduced. 
     The hydraulic pressure supply system of an automatic transmission according to various embodiments of the present invention may supply the hydraulic pressure to the low pressure portion  6  and the high pressure portion  10  using one hydraulic pump  2  having two discharge ports. Therefore, a layout may be simple, weight may be reduced, and manufacturing cost may be curtailed. 
     In addition, power loss of the hydraulic pump may be minimized. 
     In addition, since the hydraulic pressure discharged from the low-pressure discharge port  4  and the high-pressure discharge port  8  is supplied to the high pressure portion  10  at the initial starting, shift responsiveness may be improved. 
     If the hydraulic pressure is excessively supplied to the high pressure portion  10  due to rise of the engine RPM, the hydraulic pressure discharged through the low-pressure discharge port  4  is returned to the input line  12  (or oil pan) and the hydraulic pressure discharged through the high-pressure discharge port  4  is supplied to the high pressure portion  10  and the low pressure portion  6 . Therefore, capacity of the hydraulic pump  2  may be reduced. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.