Abstract:
A hydraulic pressure supply system of an automatic transmission for a vehicle may generate low hydraulic pressure and high hydraulic pressure using oil stored in an oil pan and may supply the low hydraulic pressure and the high hydraulic pressure respectively to a low pressure portion and a high pressure portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority of Korean Patent Application Number 10-2012-0097301 filed on Sep. 3, 2012, the entire contents of which application is incorporated herein for all purposes by this reference. 
       BACKGROUND OF INVENTION 
       [0002]    1. Field of Invention 
         [0003]    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 which can improve safety and reliability as a consequence that the automatic transmission can be operated normally using hydraulic pressure of a low-pressure hydraulic pump when a high-pressure hydraulic pump is stopped. 
         [0004]    2. Description of Related Art 
         [0005]    Recently, vehicle makers direct all their strength to improve fuel economy due to worldwide high oil prices and strengthen of exhaust gas regulations. 
         [0006]    Improvement of fuel economy may be achieved by improving power delivery efficiency in an automatic transmission, and improvement of the power delivery efficiency may be achieved by minimizing unnecessary power consumption of a hydraulic pump. 
         [0007]    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). 
         [0008]    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. 
         [0009]    Since power consumption for driving the hydraulic pumps can be minimized, fuel economy may be enhanced. In addition, since a load applied to the hydraulic pumps is reduced, noise and vibration may be reduced and durability may be improved. 
         [0010]    Since hydraulic pressure generated by the low-pressure hydraulic pump is supplied to the high-pressure hydraulic pump and the high hydraulic pressure is generated by the high-pressure hydraulic pump according to a conventional hydraulic pressure supply system, the hydraulic pressure supplied to the high pressure portion is insufficient and vehicle cannot drive if the high-pressure hydraulic pump is out of order. 
         [0011]    The information disclosed in this Background 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. 
       SUMMARY OF INVENTION 
       [0012]    Various aspects of the present invention provide for a hydraulic pressure supply system of an automatic transmission for a vehicle having advantages of improving safety and reliability when a high-pressure hydraulic pump is out of order or is stopped as a consequence of normally operating the hydraulic pressure supply system only by using hydraulic pressure of a low-pressure hydraulic pump. 
         [0013]    A hydraulic pressure supply system of an automatic transmission for a vehicle may generate low hydraulic pressure and high hydraulic pressure using oil stored in an oil pan and may supply the low hydraulic pressure and the high hydraulic pressure respectively to a low pressure portion and a high pressure portion. 
         [0014]    The hydraulic pressure supply system may include: a low-pressure hydraulic pump receiving the oil stored in the oil pan through a first input line, generating hydraulic pressure, and discharging the hydraulic pressure to a first low-pressure line; a first switch valve selectively opening or closing a hydraulic line through which the hydraulic pressure is supplied from the first low-pressure line; a low-pressure regulator valve connected to the first switch valve through a second low-pressure line, controlling the hydraulic pressure supplied through the second low-pressure line to be stable hydraulic pressure, and supplying the stable hydraulic pressure to the low pressure portion through a third low-pressure line; a high-pressure hydraulic pump increasing the hydraulic pressure supplied from the low-pressure hydraulic pump through the first low-pressure line, and discharging the increased hydraulic pressure to a high-pressure line; a second switch valve disposed between the first low-pressure line and the high-pressure line, and selectively connecting the first low-pressure line to the high-pressure line or not; a high-pressure regulator valve controlling the hydraulic pressure supplied from the high-pressure hydraulic pump through the high-pressure line and the hydraulic pressure supplied from the low-pressure hydraulic pump through the second switch valve to be stable high hydraulic pressure, and supplying the stable high hydraulic pressure to the high pressure portion; and a second input line connecting the oil pan to the first low-pressure line. 
         [0015]    The low-pressure hydraulic pump may be a mechanical hydraulic pump driven by an engine, and the high-pressure hydraulic pump may be an electric hydraulic pump driven by an electric motor. 
         [0016]    Each of the first switch valve and the second switch valve may be controlled by control pressure of a first solenoid valve that is an on/off solenoid valve. 
         [0017]    The low-pressure regulator valve may recirculate a portion of the hydraulic pressure supplied from the second low-pressure line through a first recirculation line so as to control the hydraulic pressure of the second low-pressure line to be stable, and may supply the stable hydraulic pressure to a third low-pressure line. 
         [0018]    The first recirculation line may be connected to the first input line. 
         [0019]    The low-pressure regulator valve may be controlled by elastic force of an elastic member disposed at a side thereof and the hydraulic pressure of the second low-pressure line supplied to the other side thereof. 
         [0020]    The high-pressure regulator valve may be selectively connected to the first low-pressure line through the second switch valve and may be directly connected to the high-pressure line so as to recirculate through a second recirculation line a portion of the hydraulic pressure supplied from the first low-pressure line or the high-pressure line and to control the hydraulic pressure to be stable. 
         [0021]    The second recirculation line may be connected to the third low-pressure line. 
         [0022]    The high-pressure regulator valve may be controlled by control pressure of a second solenoid valve, elastic force of an elastic member, and the hydraulic pressure of the first low-pressure line or the high-pressure line counteracting the control pressure of the second solenoid valve. 
         [0023]    The second solenoid valve may be a proportional control solenoid valve. 
         [0024]    A check valve for preventing back flow may be mounted on the second input line. 
         [0025]    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 
         [0026]      FIG. 1  is a schematic diagram of an exemplary hydraulic pressure supply system according to the present invention when a low-pressure hydraulic pump and a high-pressure hydraulic pump are operated normally. 
           [0027]      FIG. 2  is a schematic diagram of an exemplary hydraulic pressure supply system according to the present invention when a high-pressure hydraulic pump is operated abnormally. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    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 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. 
         [0029]    Description of components that are not necessary for explaining the present exemplary embodiment will be omitted, and the same constituent elements are denoted by the same reference numerals in this specification. 
         [0030]    In the detailed description, ordinal numbers are used for distinguishing constituent elements having the same terms, and have no specific meanings. 
         [0031]      FIG. 1  is a schematic diagram of a hydraulic pressure supply system according to various embodiments of the present invention when a low-pressure hydraulic pump and a high-pressure hydraulic pump are operated normally. 
         [0032]    Referring to  FIG. 1 , a hydraulic pressure supply system according to various embodiments of the present invention is adapted to supply low hydraulic pressure generated by a low-pressure hydraulic pump  2  to a low pressure portion  4  such as a torque converter (T/C), a cooling portion, a lubrication portion and to supply high hydraulic pressure generated by a high-pressure hydraulic pump  6  to a high pressure portion  8  for operating friction members related to shifting. 
         [0033]    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. 
         [0034]    The low hydraulic pressure is generated by the low-pressure hydraulic pump  2  and is supplied to the low pressure portion  4  through a first switch valve  10  and a low-pressure regulator valve  12 . 
         [0035]    The low-pressure hydraulic pump  2 , as is well known to a person of an ordinary skill in the art, is a mechanical pump driven by torque of an engine. The low-pressure hydraulic pump  2  is connected to an oil pan P through a first input line  14 , and the low hydraulic pressure generated by the low-pressure hydraulic pump  2  is discharged to a first low-pressure line  16 . 
         [0036]    The first switch valve  10  may be a spool valve and is controlled by a first solenoid valve SOL 1  that is on/off-controlled so as to selectively deliver the hydraulic pressure of the first low-pressure line  16  to the low-pressure regulator valve  12 . 
         [0037]    That is, if the first solenoid valve SOL 1  is switched off, the first switch valve  10  supplies the hydraulic pressure of the first low-pressure line  16  to the low-pressure regulator valve  12  through a second low-pressure line  18 . If the first solenoid valve SOL 1 , on the contrary, is switched on, the first switch valve  10  is not connect the first low-pressure line  16  to the second low-pressure line  18 . 
         [0038]    The low-pressure regulator valve  12  is connected to the first switch valve  10  through the second low-pressure line  18  and is connected to the first input line  14  through a first recirculation line  20 . Therefore, the low-pressure regulator valve  12  recirculates a portion of the hydraulic pressure supplied from the first switch valve  10  to the first input line  14  through the first recirculation line  20  so as to control the hydraulic pressure. 
         [0039]    That is, the low-pressure regulator valve  12  is controlled by elastic force of an elastic member  22  disposed at a side thereof and the hydraulic pressure of the second low-pressure line  18  supplied to the opposite side of the elastic member  22  so as to control the hydraulic pressure, and delivers the controlled hydraulic pressure to the low pressure portion  4  through a third low-pressure line  24 . The elastic force of the elastic member  22  is set according to the hydraulic pressure demanded by the low pressure portion  4 . 
         [0040]    In addition, a second switch valve  26  connected to the first low-pressure line  16  selectively delivers the hydraulic pressure of the first low-pressure line  16  to the high pressure portion  8 . 
         [0041]    For this purpose, the second switch valve  26  may be a spool valve, and is controlled by the first solenoid valve SOL 1  that is on/off-controlled so as to selectively deliver the hydraulic pressure of the first low-pressure line  16  to the high pressure portion  8 . 
         [0042]    That is, if the first solenoid valve SOL 1  is switched off, the second switch valve  26  is not connect the first low-pressure line  16  to the high pressure portion  8 . If the first solenoid valve SOL 1 , on the contrary, is switched on, the second switch valve  26  delivers the hydraulic pressure of the first low-pressure line  16  to the high pressure portion  8 . 
         [0043]    The high-pressure hydraulic pump  6  may be an electric pump driven by an electric motor. In addition, the high-pressure hydraulic pump  6  increases the low hydraulic pressure supplied through the first low-pressure line  16  to the high hydraulic pressure, and discharges the high hydraulic pressure to a high-pressure line  28 . In addition, the hydraulic pressure discharged from the high-pressure hydraulic pump  6  to the high-pressure line  28  is controlled to be a stable high hydraulic pressure by a high-pressure regulator valve  30 , and the stable high hydraulic pressure is supplied to the high pressure portion  8 . 
         [0044]    The high-pressure regulator valve  30  is connected to the high-pressure line  28  and is connected to the third low-pressure line  24  through a second recirculation line  32 . Therefore, the high-pressure regulator valve  30  recirculates a portion of the hydraulic pressure supplied through the high-pressure line  28  to the third low-pressure line  24  through the second recirculation line  32  so as to control the hydraulic pressure. 
         [0045]    For this purpose, the high-pressure regulator valve  30  may be a conventional spool valve. In addition, the high-pressure regulator valve  30  is controlled by control pressure of a second solenoid valve SOL 2  performing proportional control, elastic force of an elastic member  34 , and the hydraulic pressure of the high-pressure line  28  counteracting the control pressure of the second solenoid valve SOL 2 . The elastic force of the elastic member  34  is set according to the hydraulic pressure demanded by the high-pressure line  28 . 
         [0046]    The second recirculation line  32  is connected to the third low-pressure line  24  so as to supply the hydraulic pressure to the low pressure portion  4  when only the high-pressure hydraulic pump  6  is operated. 
         [0047]    In addition, the high-pressure hydraulic pump  6  is connected to the oil pan P through a second input line  38 . A check valve  36  for preventing back flow is disposed on the second input line  38 . Therefore, the high-pressure hydraulic pump  6  directly receives the oil from the oil pan P so as to generate the high hydraulic pressure when the hydraulic pressure is not supplied from the low-pressure hydraulic pump  2  to the high-pressure hydraulic pump  6 . 
         [0048]    When the low-pressure hydraulic pump  2  and the high-pressure hydraulic pump  6  are operated normally, the hydraulic pressure supply system according to various embodiments of the present invention supplies the low hydraulic pressure generated by the low-pressure hydraulic pump  2  to the low pressure portion  4  and supplies the high hydraulic pressure generated by the high-pressure hydraulic pump  6  to the high pressure portion  8 , as shown in  FIG. 1 . 
         [0049]    At this time, the first solenoid valve SOL 1  is switched off, and the low hydraulic pressure generated by the low-pressure hydraulic pump  2  is supplied to the low-pressure regulator valve  12  through the first switch valve  10  so as to be controlled to be the stable low hydraulic pressure. After that, the stable low hydraulic pressure is supplied to the low pressure portion  4 . 
         [0050]    In addition, a portion of the low hydraulic pressure generated by the low-pressure hydraulic pump  2  is increased to the high hydraulic pressure by the high-pressure hydraulic pump  6 , and the high hydraulic pressure is controlled to be the stable high hydraulic pressure by the high-pressure regulator valve  30  and is then supplied to the high pressure portion  8 . 
         [0051]      FIG. 2  is a schematic diagram of a hydraulic pressure supply system according to various embodiments of the present invention when a high-pressure hydraulic pump is operated abnormally. 
         [0052]    That is, oil flow when the high-pressure hydraulic pump  6  is not operated due to failure or lack of power in a battery is illustrated in  FIG. 2 . In this case, the first solenoid valve SOL 1  is switched on. 
         [0053]    At this time, the hydraulic pressure generated by the low-pressure hydraulic pump  2  is not supplied to the low-pressure regulator valve  12  by the first switch valve  10  and is supplied to the high-pressure line  28  by the second switch valve  26 . In addition, the hydraulic pressure supplied to the high-pressure line  28  is controlled to be the high hydraulic pressure by the high-pressure regulator valve  30 , and the high hydraulic pressure is supplied to the high pressure portion  8 . Therefore, the high pressure portion  8  can be operated smoothly. 
         [0054]    At this time the hydraulic pressure recirculated from the high-pressure regulator valve  30  to the third low-pressure line  24  through the second recirculation line  32  is supplied to the low pressure portion  4 . Therefore, the low pressure portion  4  can be operated smoothly. 
         [0055]    Since the hydraulic pressure supply system is operated normally using the low-pressure hydraulic pump  2  when the high-pressure hydraulic pump  6  is not operated, safety and reliability of the hydraulic pressure supply system having two hydraulic pumps  2  and  6  may be improved. 
         [0056]    Particularly, when the vehicle provided with the ISG system is stopped temporarily, the high hydraulic pressure may be supplied to the high pressure portion  8  in a state of engine stop. At this time, the high-pressure hydraulic pump  6  is operated so as to pump the oil in the oil pan P through the second input line  38  and generate the high hydraulic pressure. Therefore, the preparatory hydraulic pressure can be supplied to the high pressure portion  8 . 
         [0057]    That is, although the engine is stopped and the low-pressure hydraulic pump  2  is not operated, the high hydraulic pressure can be supplied to the high pressure portion  8  by operation of the high-pressure hydraulic pump  6 . 
         [0058]    According to various embodiments of the present invention, the low-pressure hydraulic pump  2  generates the low hydraulic pressure and the high-pressure hydraulic pump  6  generates the high hydraulic pressure by increasing the hydraulic pressure supplied from the low-pressure hydraulic pump  2 . Therefore, power loss of the hydraulic pumps may be minimized, durability may be improved, noise and vibration of the hydraulic pumps may be reduced. 
         [0059]    In addition, the hydraulic pressure supply system can be operated normally using the low-pressure hydraulic pump  2  when the high-pressure hydraulic pump  6  is not operated. Therefore, stability and reliability may be enhanced. 
         [0060]    In addition, since the high-pressure hydraulic pump  6  can generate the high hydraulic pressure independently, the system may be applied to the vehicle having the ISG system. 
         [0061]    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.