Abstract:
A vibration suppressor is disclosed that is configured for use in a system having a hose under pulsating hydraulic pressure. The pulsating hydraulic pressure causes vibration of the hose at the pulsation frequency. The vibration suppressor is applied to the hose and is constructed to have a resonant frequency slightly below the pulsation frequency where the pulsating hydraulic pressure is at a peak level, due to, but not limited to, the existence of a resonance in the hydraulic system.

Description:
BACKGROUND 
       [0001]    There are a wide variety of machines that employ high-pressure hydraulic systems. Such machines include, for example, tool presses, aircraft systems, and the like. Another such system is a hydraulically actuated, electronically controlled, fuel injection system that is commonly used in diesel engines. 
         [0002]    Many of these hydraulic systems require transportation of high-pressure hydraulic fluid between system units. For example, in a diesel engine, hydraulic fluid, such as oil, is transferred between a high-pressure pump and a rail through a hose. The rail, in turn, includes a plurality of outputs through which the fluid is distributed to injectors to assist the injection of fuel into the engine cylinders for combustion. 
         [0003]    In a diesel engine, pressure of the hydraulic fluid in the hose is pulsated as it flows between the pump and rail. The pulsation frequency is determined by the operation speed of the pump. The amplitude of this pulsation is exacerbated when the pulsation frequency is close to a resonance of the hydraulic system. As a result, the hose is deformed when it is pressurized. When the pressure is released, the hose typically returns to its original shape. This elastic deformation results in a lateral vibration of the hose. Over time, the vibration can cause fatigue of the hose and/or its connections to the pump and/or rail resulting in a failure of the hydraulic system. 
       SUMMARY 
       [0004]    Embodiments described herein relate to a high-pressure hose vibration suppressor and associated methods. In one embodiment, a vibration suppressor is configured for use in a system having a hose under pulsating hydraulic pressure at a pulsation frequency. The pulsating hydraulic pressure causes vibration of the hose at the pulsation frequency. The vibration suppressor comprises a suppressor mass and a resilient member configured to extend radially between an exterior surface of the hose and the suppressor mass. The suppressor mass and resilient member form a mechanical system which has a resonant frequency tuned slightly below the frequency where the hose vibrates most significantly, so that suppressor mass will impose a force via the resilient member on the hose to counter the motion of the hose. 
         [0005]    Another embodiment provides a method for use in a system having a hose under pulsating hydraulic pressure. The method comprises applying the pulsating hydraulic pressure so as to result in hose vibration at the pulsation frequency, and applying a vibration suppressor about a periphery of the hose. The vibration suppressor has a resonant frequency slightly below the pulsation frequency. 
         [0006]    Still another embodiment provides an engine comprising a high-pressure pump providing hydraulic fluid at a pulsation frequency, a distribution rail, and a hose connected to provide hydraulic fluid from the high-pressure pump to the distribution rail. The hose vibrates at the pulsation frequency in response to pulsating pressure induced between the high-pressure pump and the distribution rail. A vibration suppressor is disposed about a periphery of the hose and has a resonant frequency slightly below the pulsation frequency. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  illustrates a high-pressure hydraulic system that does not include a vibration suppressor. 
           [0008]      FIG. 2  illustrates the high-pressure hydraulic system shown in  FIG. 1 , where a vibration suppressor has been applied to the hose. 
           [0009]      FIG. 3  is a cross-sectional view of the hose and vibration suppressor along lines III-III of  FIG. 2 . 
           [0010]      FIG. 4  is a graph of vibration frequency vs. vibration amplitude in an exemplary hydraulic system without a vibration suppressor. 
           [0011]      FIG. 5  is a graph of vibration frequency vs. vibration amplitude in the exemplary hydraulic system referenced in  FIG. 4 , but with a vibration suppressor. 
           [0012]      FIG. 6  shows operations that may be executed to adjust a vibration suppressor to a resonant frequency slightly below the pulsation frequency. 
           [0013]      FIG. 7  illustrates selected portions of a high-pressure hydraulic system of a diesel engine, where a vibration suppressor has been applied to a hose. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1  illustrates a high-pressure hydraulic system that does not include a vibration suppressor. The system  10  includes a hose  15  that carries a fluid  20  under a pulsating pressure, as designated by the end point arrows of fluid  20 . 
         [0015]    The fluid  20  may be provided at an inlet  25  of the hose  15  from any one of a number of different types of hydraulic supply units  30 , such as a high-pressure pump. An exemplary pressure profile of the fluid  20  through hose  15  is shown at  35 . Fluid received at the inlet  25  proceeds to an outlet  40  of the hose  15 , which may be connected to any of a number of different types of hydraulic system units  45  that are to receive the high-pressure fluid  20 . One such system is the rail of a diesel engine. 
         [0016]    The hydraulic supply unit  30  pressure rises the hydraulic fluid  20  in the hose  15  at a pulsation frequency as it flows to the hydraulic system unit  45 . The hose  15  is deformed so that it is elongated in the direction shown by arrow  50  when it is subject to a positive pressure. When the pressure is released, the hose  15  typically returns to its original shape in the direction shown by arrow  55 . As the both ends of the hose are fixed, this elongation motion of the hose often becomes a motion in the lateral direction. It should be noted that this example is directed to a positive pressure system, and that the deformation of the hose  15  would occur in directions opposite to those shown at  50  and  55  in a negative pressure system. 
         [0017]    The pulsating pressure through the hose  15  results in a lateral vibration, for example, along a radial axis  60 . The lateral vibration occurs at the same pulsation frequency of the fluid provided by the hydraulic supply unit  30 . Over time, this vibration can cause fatigue of the hose  15  resulting in failure of the hose material. Further, the vibration may fatigue the connections between the hose  15  and the units  30  and  45  resulting in fluid leakage and/or connection failure. 
         [0018]      FIG. 2  illustrates a further high-pressure hydraulic system  70  of the type shown in  FIG. 1 . However, unlike hydraulic system  10 , the high-pressure hydraulic system  70  includes a vibration suppressor  75  applied to the hose  15 . The vibration suppressor  75  is designed to suppress vibration of the hose  15  in the lateral direction that is caused by the pressure pulsation. Vibration suppression is achieved by designing the vibration suppressor  75  to generate a force that counters the lateral motion of the hose  15 . The resonance frequency of the vibration suppressor is adjusted to just slightly below the pulsating frequency so as to maximize the amplitude of the counter force. As a result, the amplitude of the hose vibration is reduced. By reducing the amplitude of the vibration, the reliability and life expectancy of the hose  15  are increased. 
         [0019]    Depending on system structure and operational requirements, the vibration suppressor  75  may be applied to the hose in matters other than the one shown in  FIG. 2 . For example, although a single vibration suppressor  75  is shown, multiple vibration suppressors  75  may be used. Still further, multiple vibration suppressors  75  may be tuned to different resonant frequencies, where each resonant frequency is slightly below the pulsation frequencies where amplitudes of hose vibration are significant. 
         [0020]      FIG. 3  is a cross-sectional view of the hose  15  and vibration suppressor  75  along lines III-III of  FIG. 2 . The cross-sectional view illustrates one manner of constructing the vibration suppressor  75  and placing it about hose  15 . In  FIG. 3 , the hose  15  may be flexible and include an interior cavity  80  through which the hydraulic fluid flows at the pulsation frequency and an exterior surface  85  in contact with the vibration suppressor  75 . 
         [0021]    The vibration suppressor  75  also includes a suppressor mass  90 , which may be in the form of a metal sleeve, and one or more resilient members  100  and  105 . In  FIG. 3 , two resilient members  100  and  105  are used. However the two resilient members  100  and  105  may be connected with one another at their end portions. In such instances, resilient members  100  and  105  are in the form of a single resilient member that is divided at a mid-portion of the vibration suppressor  75  to effectively form two resilient members at the mid-portion. Hose and suppressor mass may be molded together via the resilient member to form an integrated hose with a vibration suppressor. 
         [0022]    In the embodiment of  FIG. 3 , each resilient member  100  and  105  may be formed from an elastomeric material, such as rubber or other elastomer. As shown, the resilient members  100  and  105  may be disposed on opposite sides of the hose  15 . In this configuration, resilient members  100  and  105  deforms radially between a first portion of the exterior surface  85  of hose  15  and a first portion of the interior surface  110  of the suppressor mass  90 . 
         [0023]      FIG. 4  is an exemplary graph of the amplitude of the vibration of the hose  15  versus frequency. The hose  15  of  FIG. 4  does not include a vibration suppressor  75 . In this example, the hose  15  experiences a general peak vibration amplitude about the pulsation frequency 335 Hz of approximately 0.15 mm (RMS). The hose does not have a structural resonance at 335 Hz. However, the vibration amplitude of the hose increases around 335 Hz because the amplitude of the pulsating pressure increases which is due to the existence of a 335 Hz resonance in the hydraulic system. 
         [0024]      FIG. 5  is an exemplary graph of the amplitude of the vibration of the hose  15  versus frequency when the vibration suppressor  75  is applied to the hose  15 . As shown, the hose  15  experiences a general peak vibration amplitude of about 335 Hz. However, when compared to the vibration experience by the hose  75  in  FIG. 4 , the peak vibration amplitude has been reduced to approximately 0.04 mm (RMS). This amounts to a reduction of the peak vibration amplitude to approximately ⅓ of that experienced by a hose  15  that does not have the vibration suppressor  75  applied. Even though the vibration suppressor  75  helps to reduce the hose vibration, it has almost no effect on the resonance of the hydraulic system (i.e., the pulsating pressure is almost unchanged). 
         [0025]      FIG. 6  shows one example of a method that may be used to tune the vibration suppressor  75 , such as the one shown in  FIG. 3 , to a resonant frequency that is slightly below the pulsation frequency. The method may start at operation  150  with a baseline vibration suppressor  75  having a predetermined suppressor mass and predetermined resilient member structure. The baseline vibration suppressor  75  may be attached to a rigid support rod at operation  155 . At operation  160 , the baseline vibration suppressor  75  is excited. Such excitation may include striking the vibration suppressor  75  with an instrumented hammer. The frequency of the vibration of the vibration suppressor  75  is measured at operation  165  using an accelerometer. A check is made at operation  170  to determine whether the measured resonant frequency is slightly below the pulsation frequency. If it is not, the method may be continued at operation  175  to adjust the resonant frequency to bring it closer to the frequency that is slightly below the pulsation frequency. This may be done by adjusting the characteristics of the resilient member and/or suppressor mass. For example, such an adjustment may include changing the mass of the suppressor mass, changing the elastomeric material of the resilient member(s), changing the dimensions of the resilient member(s), changing the diameter of the suppressor mass opening, and the like. After making the adjustment, the vibration suppressor  75  may be reattached to the rigid support rod, as at operation  185 , and the resonance of the suppressor system is re-evaluated beginning again at operation  160 . This cycle may be repeated until a satisfactory resonant frequency is obtained, at which point, the method may be ended at  180 . 
         [0026]    As previously noted, the vibration suppressor  75  may be used in an engine, such as a diesel engine. Such a diesel engine is shown generally at  200  of  FIG. 7 . The exemplary engine  200  includes a tank  205  that stores a hydraulic fluid, such as oil or fuel. The content of tank  205  is extracted by a high-pressure hydraulic pump  210  through a fluid conduit  215 . 
         [0027]    The high-pressure hydraulic pump  210  directs the hydraulic fluid to a rail  220  at a pulsation frequency which is determined by the pump rotating speed through hose  15 . The hose  15  is provided with a vibration suppressor  75 , which reduces the vibration of the hose  15  that would otherwise occur about the pulsation frequency. 
         [0028]    The rail  220  provides the hydraulic fluid to a plurality of fuel injectors  225 . The pressure of the hydraulic fluid within rail  220  is such that the fluid is distributed to each of the plurality of fluid injectors  225  at substantially the same pressure. 
         [0029]    The pulsation frequency is determined by rotating speed of the pump  210 . The amplitude of the pressure pulsation is determined by the operating parameters of the pump (i.e., speed of the pump and the desired pressure level) and the response properties of the hydraulic system, which consists of the pump, hose, rail injectors and other components. The pressure pulsation increases dramatically when the pulsation frequency matches a resonance frequency of the hydraulic system. In those instances there are more than one response peaks over the engine operation speed range, multiple vibration suppressors  75  tuned to different resonant frequencies may be employed.