Patent Publication Number: US-6666655-B2

Title: Hydraulic pump nozzle and method of use

Description:
The disclosure incorporates the hydraulic pump nozzle and method of use disclosed in provisional application 60/290,630, filed May 11, 2001, whose priority is claimed for this application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This invention relates generally to hydraulic pump nozzles employed to boost the fluid flow and pressure of hydraulic fluid delivered to a hydraulic pump rotating group, such as a hydraulic pump of a vehicle transmission system. 
     2. Related Art 
     In a typical automotive hydraulic transmission system, a motor driven pump delivered hydraulic fluid under pressure to the transmission to operate the transmission with the return fluid being fed to the pump in a closed system. A prior hydraulic booster nozzle such as that illustrated at  10  in FIG. 1 is situated at the intake of the pump  11  and receives a primary flow  12  of hydraulic fluid returned from a sump of the transmission into a primary flow channel  13  of the nozzle  10 . In this system, a fraction of the high pressure flow delivered by the pump is diverted around the transmission and fed back to the pump as a bypass flow  14  into a bypass channel  15  of the nozzle  10 . This relatively high velocity, high pressure bypass flow  14  is fed through a restriction  16 , causing the fluid velocity to increase and the pressure to decrease at the restriction. The high velocity bypass stream exits the restriction and becomes a lower velocity, higher pressure flow at the intake of the rotating group of the pump  11  where it recombines with the primary flow  12 , resulting in an overall increased flow in pressure of the combined fluid flow  17  to the pump  11 . 
     While hydraulic boost nozzles of the type shown in FIG. 1 perform satisfactorily in boosting the pressure and flow of hydraulic fluid to the intake rotating group of the pump, there is a tendency to build unacceptably high levels of back pressure in the bypass flow line which cannot be tolerated by other parts of the flow system, particularly under heavy loading of the transmission and pump which are the typical cause of the excessive back pressure in the bypass line. Consequently, one designed constraint of current booster nozzles is that the flow constraint and other design characteristics of the flow channels must be such that they produce exceptionably low levels of back pressure in the bypass line under heavy loading of the pump within design limits of the other components of the system. However, designing the nozzle to decrease the back pressure in the bypass line has the effect of decreasing the boosting performance of the nozzle for delivering maximum flow of hydraulic fluid to the rotating group at the intake of the pump. 
     A booster nozzle constructed according to the present invention overcomes or greatly minimizes the foregoing limitations of prior booster nozzle constructions. 
     SUMMARY OF THE INVENTION AND ADVANTAGES 
     This invention provides a unique apparatus and method for boosting the pressure at the intake of a hydraulic pump, such as a transmission pump of a vehicle. The apparatus and method are particularly suitable for use in continuously variable transmission (CVT) pump applications. They provide reduced back pressure as compared to prior art booster nozzles, while at the same time providing increased fluid flow, and thus pressure, at the intake of the rotating group. This in turn results in improved pump operating performance, such as reduced cavitation and reduced pump noise at high speeds. 
     According to particularly preferred features of the invention, the apparatus comprises a nozzle body having a primary flow channel for receiving and delivering a primary flow of hydraulic fluid to the pump. The primary flow is fed from a sump and comprises that portion of the return flow necessary to drive the pump rotating group. The nozzle body is formed with a bypass flow channel that receives a bypass flow of hydraulic fluid from the pump. The bypass flows separately from the primary flow upline of the transmission using an appropriate means, such as splitting the return flow using a bifurcated return line leading from an appropriate flow diverter mechanism situated upstream of the transmission, directing the bypass flow to the bypass flow channel of the nozzle body. The bypass flow is restricted through a restriction device within the bypass flow channel, causing the bypass flow velocity to increase and the pressure to decrease at the restriction. The bypass flow exiting the restriction is recombined with the primary flow in close proximity to the intake of the pump rotating group. As the bypass flow exits the restriction, its flow of velocity decreases producing a corresponding increase in pressure at the intake of the pump rotating group, yielding an overall boost in pressure and flow of the combined primary and bypass flows to the pump. 
     According to a characterizing feature of the invention, a bypass valve communicates with the bypass channel of the nozzle body. This bypass valve is operated to sense the back pressure in the incoming bypass flow. In response to the back pressure exceeding a predetermined control pressure, the bypass valve opens an auxiliary bypass flow channel and diverts a fraction of the incoming bypass flow around the flow restriction device for direct combination with the delivery of the primary flow to the inlet of the pump. By incorporating a bypass valve into the flow system, a booster nozzle can be designed to optimize its boosting performance to the pump without concern for the effects that such optimized boosting performance would have on the back pressure of the incoming bypass line. The bypass valve can be set to relieve the buildup of back pressure at the appropriate control pressure so as to direct a fraction of the bypass flow around the flow restriction so as to maintain the optimum performance of the booster nozzle for delivery of flow to the pump rotating group, while maintaining the back pressure of the bypass flow below the upper threshold limit control pressure of the particular system. 
     Another advantage of the present invention is that for a given application, a booster nozzle can be provided with increased boosting performance over that of currently available booster nozzles that at the same time maintains the back pressure of the bypass flow within acceptable design limits. In this way, the boosting performance of the booster nozzle does not need to be sacrificed in order to maintain the back pressure of the bypass flow below design limits. 
     Another advantage of the present invention is that the same basic booster nozzle construction can be used for a number of difference applications having different bypass flow back pressure requirements, by simply replacing, altering or adjusting the bypass valve to set the control pressure of the valve at the appropriate level to maintain the back pressure below the design limit of the particular application. No longer is it necessary to tailor the flow characteristics of each nozzle body to meet the design criteria of each application, particularly with regard to the limitation set by the bypass back pressure. 
     Another advantage of the present invention is that the bypass valve can work in conjunction with virtually any combination of primary and bypass flow channel and flow restrictor constructions, and thus is insensitive to the particular design of the booster characteristics of the nozzle. Whatever the design, the bypass valve operates to relieve the back pressure by diverting a fraction of the bypass flow around the flow restrictor. Accordingly, the invention has the further advantage of enabling the same basic bypass valve to be utilized in conjunction with various primary and bypass flow channel configurations. It will thus be appreciated that the subject apparatus has built-in flexibility to meet the design criteria of virtually any flow system calling for a booster nozzle at the intake of a pump in order that the performance of the booster nozzle be optimized both in regard to the delivery of boosted flow to the pump and minimal impact to the performance of the remaining components of the flow system through control of the bypass flow back pressure. 
    
    
     THE DRAWINGS 
     Presently preferred embodiments of the invention are disclosed in the following description and in the accompanying drawings, wherein: 
     FIG. 1 is a prior art booster nozzle; 
     FIG. 2 is a schematic of a hydraulic flow system of the invention; 
     FIG. 3 is a perspective view of a booster nozzle constructed according to a presently preferred embodiment of the invention; 
     FIG. 4 is an enlarged cross-sectional view of the booster nozzle; 
     FIG. 5 is a cross-sectional view of the booster nozzle shown associated with an intake of a pump; and 
     FIGS. 6 and 7 are perspective views of the booster nozzle shown partly in section to illustrate further features of the nozzle body. 
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, and particularly FIG. 2, a hydraulic flow system  20  is shown having a hydraulic pump  22  driven by motor  24  for delivering a supply of hydraulic fluid to a diverter valve  26  which splits the flow, such that the amount of fluid needed to drive a device, such as the illustrated transmission  28  is passed through the diverter valve onto the transmission  28 , and the excess flow is returned through a bypass line  30  back to the pump  22  in a manner to be described below. 
     The flow of fluid from the transmission  28  is fed to a sump  32  which is then drawn through a filter  34  into an inlet  36  of a primary flow channel  38  of a booster nozzle  40  of the system  20 . The flow from the sump  32  represents a primary flow of hydraulic fluid needed to operate a rotating group of the pump  22 . The return flow through the bypass line  30  is fed to an inlet  44  of a bypass channel  46  of the booster nozzle  40 . The bypass channel  46  is fitted with an appropriate flow restrictor or flow restriction device  48 , such as an orifice or jet or other constriction in the flow path of the bypass flow  50 . The primary flow of fluid  42  in the primary flow channel  38  is passed on to the inlet of the pump  22 . The bypass flow  50  introduced to the bypass channel  46  is fed to the flow restrictor  48  which produces a sudden increase in velocity of the flow  50  at the flow restrictor  48 , and a corresponding increase in back pressure in the bypass line  30 . The high velocity bypass flow exiting the flow restrictor  48  suddenly decreased in velocity and produces a corresponding increase in pressure of the bypass flow downstream of the flow restrictor  48  where the bypass flow  50  recombines with the primary flow  42  at the intake of the pump  22  to yield a combined flow  52  of hydraulic fluid having an overall increased pressure in volume of flow to the pump  22  then would be provided without the boosting effect of the bypass flow  50  on the primary flow  42 . 
     Turning more particularly to the drawing FIGS. 3-7, it will be seen that the primary flow channel  38  may be preferably located centrally in a nozzle body  54  of the booster nozzle  40  having the inlet  36  at one end and an outlet  56  at the opposite end and being fully isolated along its length from the bypass flow channel  46 . 
     As also shown in these drawings, the nozzle body  54  may preferably have an overall generally cylindrical configuration formed with a set of O-ring grooves  60 ,  62  which are axially spaced on opposite sides of a reduced diameter section of the nozzle body  54  that serves as the inlet  44  of the bypass channel  46 . Suitable O-ring seals  64 ,  66  are carried in the O-ring grooves  60 ,  62 , respectively, and, as illustrated best in FIG. 5, form a fluid-type seal with a bore  68  of a pump body  70  of the pump  20  associated with the inlet  72  of the pump  22 . 
     The bypass flow  50  from the bypass line  30  is fed through the pump body  70  into the annular inlet  44  of the bypass channel  46 , where the bypass flow  50  is initially isolated from the primary flow  42  and sealed against leakage by the O-rings  64 ,  66 . As shown best in FIGS. 3-5, the flow restrictor device  48  may comprise at least one and preferably a plurality of flow restricting jets  74  having outlets  76  adjacent the outlet  56  of the primary flow channel  38 . When a plurality of jets  74  are employed, it is preferred that the outlets  76  be arranged in spaced location about the outlet  56  of the primary flow channel  38  to provide a full or partial outer enveloping of the discharge primary flow  42  by the boosted bypass flow  50 . It will be appreciated from FIG. 4 that the jets  74  represent a constricted flow passage for the bypass flow  50  as it passes from the bypass channel  46  to the outlet  76  of the jets  74 . As the boosted bypass flow  50  exits the outlet  76 , it is combined with the primary flow to yield the combined flow  52  of the recombined primary and bypass hydraulic flows at the inlet of the pump  22 . 
     Referring again to FIG.  2  and also to the remaining FIGS. 3-7, the booster nozzle  40  of the invention is fitted with a bypass valve  78 . The bypass valve  78  is an open flow communication with the bypass channel  46 . The bypass valve  78  is operative to sense the back pressure of the bypass flow  50  in the incoming bypass line  30 . In response to the back pressure exceeding a predetermined control pressure, the bypass valve  78  opens an auxiliary bypass flow channel  80  which serves to divert a fraction of the bypass flow  50  fed to the bypass channel  46  around the flow restrictor  48  for direct combination with the delivery of the primary flow  42  at the inlet  72  of the pump  22  so long as the back pressure remains above the control pressure. At a point where the back pressure falls below the control pressure, the bypass valve  78  operates to close the auxiliary flow path, directing all of the bypass flow through the flow restrictor  48 . 
     One embodiment of a suitable bypass valve  78  is illustrated in the drawings, but those skilled in the art will appreciate that other types and configurations of bypass valves could be utilized as an equivalent structure to achieve the same or similar result of bypassing a fraction of the incoming bypass flow around the diverter in the event that the back pressure in the bypass line exceeds a predetermined control pressure. 
     The illustrated bypass valve  78  includes a seat valve member  82  which is slideably supported in the bypass flow channel  80  and is biased by a spring  84  into seated engagement with a valve seat  86  of the nozzle body  54 . When seated, the seat valve member  82  closes the auxiliary bypass flow channel  80 . When the back pressure of the incoming bypass flow  50  exceeds the bias force of the spring  84 , the back pressure overcomes the spring  84 , causes the seat valve member  82  to unseat from the valve seat  86 , and compress the spring  84  until such point that the counteracting force of the spring on the seat valve member  82  equals that of the force applied by the back pressure. The seat valve member  82  is formed with at least one and preferably a plurality of fluid openings  88  which are normally blocked and thus closed when the seat valve member  82  is seated against the valve seat  86 , but are opened when the seat valve member  82  is unseated to open flow communication between the bypass channel  46  and the auxiliary bypass flow channel  80 . 
     The control pressure of the bypass valve  78  can be adjusted by corresponding adjustment of the closing bias force exerted by the spring  84 . As will be appreciated by those skilled in the art, an increase or decrease in the bias force of the spring can be achieved by compressing or decompressing the spring or replacing the spring with another spring having a different spring constant. In the embodiment shown, the bypass valve  78  includes a spring retainer  90  engaging the end of the spring  84  opposite that of the seat valve member  82 . The spring retainer  90  includes at least one fluid opening adjacent the outlet  56  of the primary flow  42  for discharging fluid from the auxiliary bypass flow channel  80 . As shown, the spring retainer  90  has a single central fluid opening  92  which is preferred, although two or more fluid openings would suffice and are contemplated by the invention. 
     To accommodate adjustment and/or removal and replacement of the spring  84 , the spring retainer  90  is removeably retained and preferably adjustable within the bypass flow channel  80 . For this purpose, the spring retainer  90  is formed with screw threads  94  on the outer perimeter which threadably engage screw threads  96  formed in the flow channel  80 . This enables the position of the spring retainer  90  to be adjusted within the channel and, if desired, the biasing force exerted on the seat valve member  82  to be adjusted by positioning the spring retainer  90  nearer to or further away from the seat valve member  82  in order to compress or decompress the spring  84 , respectively. Such also enables the spring retainer  90  to be removed from the nozzle body  54  in order to remove the spring  84  and replace it with another spring having different spring characteristics to achieve a change in the biasing force and thus control pressure of the bypass valve  78 . Accordingly, by exposing the bypass flow  50  upstream of the flow restrictor  48  to the bypass valve  78  of the invention, any back pressure that is built up in the incoming bypass flow due to the presence of a restrictor, is relieved by operation of the bypass valve  78  selectively opening the auxiliary bypass channel  80  to divert a fraction of the flow around the restrictor  48 . 
     The disclosed embodiments are representative of presently preferred forms of the invention, but are intended to be illustrative rather than definitive thereof. The invention is defined in the claims.