Patent Abstract:
A hydraulic pump system for an automatic transmission has the advantages of preventing excessive power loss and durability deterioration. The hydraulic pump system may include a first hydraulic pump that generates a first hydraulic pressure to supply a low pressure portion with the first hydraulic pump, a second hydraulic pump that receives the first hydraulic pressure to generate a second hydraulic pressure higher than the first hydraulic pressure and supplies a high pressure portion with the second hydraulic pressure, and a drive portion that rotates a drive shaft that integrally connects the first hydraulic pump with the second hydraulic pump.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2010-0123019 filed Dec. 3, 2010, the entire contents of which application is incorporated herein for all purposes by this reference. 
     BACKGROUND OF INVENTION 
     1. Field of Invention 
     The present invention relates to a hydraulic pump system for an automatic transmission that is configured to minimize a power loss caused by a hydraulic pump. 
     2. Description of Related Art 
     For example, a hydraulic pump that is operated by an engine has a suction hole that is connected to an oil fan to supply a discharge hole with pumped oil in a hydraulic pump system for an automatic transmission. 
     The discharge hole is connected to a high pressure portion (for example, clutch) through a high pressure passage, and a high pressure regulating valve is disposed on a high pressure passage. The high pressure passage supplies a high hydraulic pressure to the high pressure portion. Also, a pressure reduction valve is interposed on the high pressure passage to be connected to a low pressure passage. The low pressure passage supplies a low pressure portion to a low pressure portion (for example, lubrication portion). 
     The high pressure regulating valve and the pressure reduction valve set a high pressure and a low pressure to recirculate remained oil to a suction hole of the hydraulic pump. Generally, the low pressure portion is used to lubricate an automatic transmission and therefore large amount of oil is necessary and the high pressure portion is used to control a clutch and therefore small amount of oil is necessary. 
     However, the hydraulic pump pumps entire oil flux base on the high pressure portion and therefore an excessive load is applied to the pump. A durability is deteriorated, a power is lost, and noise and pressure vibration are generated thereby. 
     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 
     Various aspects of the present invention provide for a hydraulic pump system for an automatic transmission having advantages of preventing excessive power loss and durability deterioration. 
     Various aspects of the present invention provide for a hydraulic pump system for an automatic transmission having advantages of pumping entire oil flux by a low pressure portion and discharging a necessary oil flux by a high pressure portion to reduce noise and pressure vibration of a hydraulic pump. 
     A hydraulic pump system for an automatic transmission according to various aspects of the present invention may include a first hydraulic pump that generates a first hydraulic pressure to supply a low pressure portion with the first hydraulic pump, a second hydraulic pump that receives the first hydraulic pressure to generate a second hydraulic pressure higher than the first hydraulic pressure and supplies a high pressure portion with the second hydraulic pressure, and a drive portion that rotates a drive shaft that integrally connects the first hydraulic pump with the second hydraulic pump. 
     The first hydraulic pump may be connected to an oil fan through a first suction hole to suck in oil and is connected to a low pressure portion through the first discharge hole to discharge the first hydraulic pressure, and the second hydraulic pump may suck the first hydraulic pressure through a connection passage that connects the first discharge hole with a second suction hole and is connected to the high pressure portion through the second discharge hole to discharge the second hydraulic pressure. 
     The first discharge hole may be connected to the low pressure portion through a low pressure passage and the second discharge hole may be connected to the high pressure portion through a high pressure passage. 
     A low pressure regulating valve that is connected to the low pressure passage may set the first hydraulic pressure to return remained oil to the oil fan. 
     The first switch valve that is connected to the high pressure passage may control a oil that is diverged from the second hydraulic pressure, and a high pressure regulating valve that is connected to the first switch valve may control oil passing the first switch valve that is turned on to set the second hydraulic pressure and recirculates remained oil to the second suction hole. 
     A second switch valve that is disposed on the high pressure passage may control the second hydraulic pressure that is supplied to the high pressure portion, supplies the high pressure portion with the second hydraulic pressure that is discharged from the second discharge hole by an operation of the first switch valve, and recirculates the first hydraulic pressure that is discharged from the second discharge hole by an disoperation of the first switch valve to the second suction hole. 
     The first switch valve and the second switch valve may be connected to a solenoid valve to be on/off controlled. 
     The hydraulic pump system for an automatic transmission may further include a first check valve that is disposed between the high pressure passage and the low pressure passage, and a second check valve that is disposed on the high pressure passage between the second switch valve and the high pressure portion. 
     The drive portion may include an engine or a motor. 
     A first oil flux of the first hydraulic pump may be larger than that of the second hydraulic pump. 
     In various embodiments of the present invention as described above, the first hydraulic pump discharges an entire oil flux based on a low pressure and the second hydraulic pump discharges a necessary high pressure such that an excessive load is not applied to the hydraulic pump to prevent a power loss and durability thereof. Also, noise and pressure vibration of the hydraulic pump can be reduced. 
     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 hydraulic circuit diagram showing a condition that a high pressure portion of an exemplary hydraulic pump system for an automatic transmission is operated according to the present invention. 
         FIG. 2  is a schematic diagram of a hydraulic pump that is applied to  FIG. 1 . 
         FIG. 3  is a hydraulic circuit diagram showing a condition that a high pressure portion of an exemplary hydraulic pump system for an automatic transmission is not operated according to the present invention. 
     
    
    
     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 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 hydraulic circuit diagram showing a condition that a high pressure portion of a hydraulic pump system for an automatic transmission (hereinafter, it is referred to as “hydraulic pump system”) is operated according to various embodiments of the present invention. That is, the hydraulic pump system supplies a high pressure portion (for example, clutch) (C) with a high hydraulic pressure and supplies the low pressure portion (for example, lubrication portion) (L) with a low hydraulic pressure. 
     Referring to  FIG. 1 , the hydraulic pump system according to various embodiments includes a first hydraulic pump  10  that generates a first hydraulic pressure (hereinafter, it is referred to as a “low pressure”), a second hydraulic pump  20  that generates a second hydraulic pressure (hereinafter, it is referred to as a “high pressure”), and a drive portion  40  that drives a drive shaft  31  of the first and second hydraulic pump  10  and  20 . 
     The low hydraulic pressure is supplied to the low pressure portion (L) of the automatic transmission to have a low pressure suitable to lubrication. The high hydraulic pressure is supplied to the high pressure portion (C) of the automatic transmission to have a high pressure suitable to effectively operate the clutch. 
     The drive portion  40  includes an engine or a motor to drive the drive shaft  31  such that the first and second hydraulic pump  10  and  20  are operated together. In this case, the first hydraulic pump  10  discharges a low hydraulic pressure to supply low pressure portion (L) with this and the second hydraulic pump  20  raises the low hydraulic pressure of the first hydraulic pump  10  to the high hydraulic pressure to supply the high pressure portion (C) with this. 
       FIG. 2  is a schematic diagram of a hydraulic pump that is applied to  FIG. 1 . Referring to  FIG. 2 , a first suction hole  11  is connected to an oil fan  50 , the first hydraulic pump  10  sucks oil through the first suction hole  11 , and the first discharge hole  12  is connected to the low pressure portion (L) to discharge a low hydraulic pressure to the first discharge hole  12 . 
     The second suction hole  21  is connected to the first discharge hole  12  through a connection passage  23 , the second hydraulic pump  20  sucks a low hydraulic pressure through the second suction hole  21 , and the second discharge hole  22  is connected to a high pressure portion (C) to supply a high hydraulic pressure. 
     The first and second hydraulic pump  10  and  20  is operated by a drive shaft  31  that is integrally formed to be built in a pump body. Accordingly, the connection passage  23  is formed between the first and second hydraulic pump  10  and  20  in the pump body  32  to connect the first discharge hole  12  with the second suction hole  21 . Accordingly, an equal hydraulic pressure i.e. a low pressure is applied to the first discharge hole  12  and the second suction hole  21 . 
     The oil of a low hydraulic pressure that is discharged by the first hydraulic pump  10  is larger than that of a high hydraulic pressure that is discharged from the second hydraulic pump  20 . The first hydraulic pump  10  discharges a total oil based on a low pressure, and the second hydraulic pump  20  boosts a pressure to discharge as much as it needs. Accordingly, a power loss for the hydraulic pump is minimized, durability is improved, and noise and pressure vibration of the hydraulic pump is reduced. 
     Referring to  FIG. 1 , the first suction hole  11  of the first hydraulic pump  10  is connected to the oil fan  50  through the suction passage  13  and the first discharge hole  12  is connected to a low pressure portion (L) through the low pressure passage  61 . The second discharge hole  22  of the second hydraulic pump  20  is connected to the high pressure portion (C) through the high pressure passage  62 . 
     A low pressure regulating valve  14  is connected to a oil passage diverged from the low pressure passage  61  to be connected to the oil fan  50  through a recirculation passage  15 . Accordingly, the low pressure regulating valve  14  sets an oil of a low hydraulic pressure that is supplied to the low pressure passage  61  and recirculates a remained oil to the oil fan  50  through the recirculation passage  15 . That is, a predetermined oil of low pressure is formed in the low pressure passage  61  according to the oil that is recirculated to the oil fan  50  from the low pressure regulating valve  14 . 
     The first switch valve  71  is connected to an oil passage that is diverged from the high pressure passage  62  and is on/off controlled by a solenoid valve  51  to regulate an oil of the high pressure passage  62 . 
     That is, while the first switch valve  71  is turned on (refers to  FIG. 1 ), a high hydraulic pressure of the high pressure passage  62  is transferred from an inflow port  711  to an outflow port  712 , and while the first switch valve  71  is turned off (refers to  FIG. 3 ), a low hydraulic pressure of the high pressure passage  62  is disconnected between the inflow port  711  and the outflow port  712 . 
     The high pressure regulating valve  24  is connected to an outflow port  712  of the first switch valve  71  to be connected to the second suction hole  21  of the second hydraulic pump  20  through a recirculation passage  25 . Also, the high pressure regulating valve  24  controls an oil of high pressure during an ‘ON’ of the first switch valve  71  and stops its operating during an ‘OFF’ thereof. 
     Accordingly, the high pressure regulating valve  24  sets a hydraulic pressure passing the first switch valve  71  to set an oil flux that is supplied to the high pressure passage  62  and recirculates a remained oil to the second suction hole  21  of the second hydraulic pump  20 . That is, an oil of a predetermined high pressure is formed in the high pressure passage  62  according to an oil that is recirculated to the second suction hole  21  of the second hydraulic pump  20  through the high pressure regulating valve  24 . 
     The second switch valve  72  is disposed on the high pressure passage  62  and is turned off or on by the solenoid valve  51  to regulate a high hydraulic pressure supplied to the high pressure portion (C). 
     That is, while the first switch valve  71  is turned on, the second switch valve  72  supplies an oil of high hydraulic pressure discharged from the second discharge hole  22  to the high pressure portion (C) (refers to  FIG. 1 ), and while the first switch valve  71  is turned off, the second switch valve  72  recirculates an oil of low hydraulic pressure discharged from the second discharge hole  22  to the second suction hole  21  (refers to  FIG. 3 ). 
     Also, a first check valve  81  is disposed between the high pressure passage  62  and the low pressure passage  61  to supply the high pressure portion (C) with a low hydraulic pressure from the low pressure passage  61  to lubricate the high pressure portion (C) that is not operated, while a high hydraulic pressure is not supplied to the high pressure passage  62 . 
     The second check valve  82  is disposed between the second switch valve  72  and the high pressure portion (C) on the high pressure passage  62  to prevent a low hydraulic pressure supplied to the high pressure portion (C) from being supplied to the second switch valve  72 . 
     Overall operations of a hydraulic pump system according to various embodiments will be described. Referring to  FIG. 1 , the first and second hydraulic pump  10  and  20  are operated by the drive shaft  31  that is rotated by the drive portion  40 . 
     A high hydraulic pressure that is discharged from the first hydraulic pump  10  to be controlled by the low pressure regulating valve  14  is supplied to the low pressure portion (L) through the low pressure passage  61  to lubricate the low pressure portion (L). 
     A low hydraulic pressure that is supplied from the first hydraulic pump  10  to the second hydraulic pump  20  through the connection passage  23  is boosted by the second hydraulic pump  20 . The boosted high hydraulic pressure is supplied to the high pressure portion (C) through the high pressure passage  62  to operate this. The second switch valve  72  cuts off the second suction hole  21  of the second hydraulic pump  20  from the high pressure passage  62 . This case includes a condition that the high pressure portion (C) i.e. the clutch is operated while the vehicle accelerates or travels a slant road. 
     That is, the solenoid valve  51  is turned off and the first and second switch valve  71  and  72  are turned on. A high hydraulic pressure supplied to the high pressure passage  62  passes the first switch valve  71  and is controlled by the high pressure regulating valve  24  to have a predetermined high pressure. A high hydraulic pressure passes the second switch valve  72  turned on to be supplied to the high pressure portion (C). 
       FIG. 3  is a hydraulic circuit diagram showing a condition that a high pressure portion of a hydraulic pump system for an automatic transmission is not operated according to various embodiments of the present invention. Referring to  FIG. 3 , a low hydraulic pressure that is discharged from the first hydraulic pump  10  to be controlled by the low pressure regulating valve  14  is supplied to the low pressure portion (L) through the low pressure passage  61  to lubricate this. 
     Also, a low hydraulic pressure that is supplied to the high pressure passage  62  from the low pressure passage  61  through the first check valve  81  is supplied to the high pressure portion (C) to lubricate the high pressure portion (C). 
     A low hydraulic pressure that is supplied to the second hydraulic pump  20  from the first hydraulic pump  10  through the connection passage  23  is discharged from the second hydraulic pump  20 . A low hydraulic pressure is recirculated to the second hydraulic pump  20  through the high pressure passage  62 . In this case, the second switch valve  72  connects the second suction hole  21  of the second hydraulic pump  20  with the high pressure passage  62 . This case includes a condition that the high pressure portion (C) i.e. a clutch is not operated while the vehicle travels a flat road. 
     That is, the solenoid valve  51  is controlled to be turned on and the first and second switch valve  71  and  72  are controlled to be turned off. A low hydraulic pressure supplied to the high pressure passage  62  is cut off by the first switch valve  71  that is turned off to not be boosted and passes the second switch valve  72  that is turned off to be recirculated to the second hydraulic pump  20 . 
     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.

Technology Classification (CPC): 5