Patent Publication Number: US-8978694-B2

Title: Oil relief valve

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2012-0122918, filed on Nov. 1, 2012, 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 an oil relief valve, and more particularly, to an oil relief valve capable of reducing an oil pressure shock, increasing a relief valve opening speed, and reducing an oil pressure trembling phenomenon. 
     2. Description of Related Art 
     Generally, a fluid such as oil needs to be supplied to apparatuses such as an engine, a transmission, and the like, of a vehicle at a predetermined pressure. For this purpose, there is a need to drive a pump such as an oil pump. In this case, a pressure of a discharged fluid is changed according to the driving of the pump. The oil pump shows a linear increase in a flux as an engine RPM increases. The increase in a flow rate causes pressure to rise within an engine oil circuit and when an engine pressure is higher than necessary, a problem of oil leakage may occur due to an increase in internal pressure of an oil sealing part and power loss may be increased at the time of the rotation of the oil pump. 
     In order to prevent the above problems, as illustrated in  FIG. 1 , an oil pump housing  100  is provided with a relief valve  1 . The relief valve  1  includes a plunger  20  that slidably moves vertically in a valve hole  10 , a spring  30  that elastically supports the plunger  20 , and a support  40  that supports the spring  30 . When an oil pressure is above a set pressure, the relief valve  1  interconnects an oil passage  60  with a relief passage  50  to discharge oil through a bypass flow that returns oil to an oil fan again. Therefore, there is a need to appropriately maintain an oil discharge pressure of the oil pump at an appropriate level and prevent damage due to a high pressure. That is, the relief valve  1  is directly received with an oil pressure of oil that is pumped and discharged from the oil pump and when an oil pressure is largely increased, the plunger  20  moves downwardly while the spring  30  is compressed. As the plunger  20  moves downwardly, the oil passage  60  and the relief passage  50  are interconnected with each other such that a part of oil is introduced into the relief passage  50 . 
     According to the relief valve  1  of the related art, the flux of oil that is introduced and returns to the relief passage  50  is linearly controlled by an oil pressure and a spring  30  constant within the relief valve  1 . Therefore, as illustrated in  FIG. 2 , an oil pressure trembling phenomenon excessively occurs on the way to the opening and closing of the oil relief valve  1 , such that an operation of the relief valve  1  controlled depending on the oil pressure may be instable and a response speed may be slow until the relief valve  1  becomes a full open state, that is, the operation of the relief valve  1  reaches a normal state. Further, the speed of the relief valve  1  is slow immediately after the relief valve  1  starts to open under the condition that oil viscosity is low, such as cold starting during winter season and thus, a large oil pressure is still generated, causing the oil pressure shock to be large. Therefore, a sealing part may be damaged and power loss may occur. 
     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 an oil relief valve capable of reducing an oil pressure shock, increasing a relief valve opening speed, and reducing an oil pressure trembling phenomenon. 
     In an aspect of the present invention, an oil relief valve apparatus may include a valve hole that is formed in a pump housing of an oil pump and is provided between an oil passage and a relief passage to communicate therebetween, a plunger provided on an upper end of the valve hole, a support provided on a lower end of the valve hole, and an elastic member provided between the plunger and the support to elastically support the plunger, wherein the valve hole may have an upper portion and a lower portion and is provided with the plunger that may have different cross sectional areas therein, wherein the plunger may have an upper end and a lower end having different cross sectional areas and face-contacts to the valve hole, and wherein the upper end of the plunger is slidably engaged to the upper portion of the valve hole. 
     By this configuration, the load pressing the elastic member is changed according to the change in a cross sectional area, thereby changing the bypassed amount of oil. 
     The valve hole may be provided so that the cross sectional area of the upper portion of the valve hole is smaller than that of the lower portion thereof, and the plunger may be provided so that the cross sectional area of the upper end of the plunger is smaller than that of the lower end thereof. 
     Therefore, the load pressing the elastic member may increase according to the increase in the cross sectional area from the upper end to the lower end, thereby increasing the bypassed oil. 
     An inclined portion inclined downwardly may be provided between the upper portion and the lower portion of the valve hole. 
     By this configuration, the flow of oil may be guided to the relief passage. 
     A height of the upper end of the plunger may be smaller than that between an upper surface of the inclined portion of the valve hole and an upper surface of the relief passage. 
     The support may be integrally provided with the pump housing to guide the movement of the relief valve. 
     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 diagram illustrating an oil relief valve according to the related art. 
         FIG. 2  is a diagram illustrating an oil pressure depending on an engine RPM of the oil relief valve according to the related art. 
         FIG. 3  is a diagram illustrating an oil relief valve according to an exemplary embodiment of the present invention. 
         FIG. 4  is a diagram illustrating an operation of the oil relief valve according to the exemplary embodiment of the present invention. 
         FIG. 5  is a diagram illustrating a comparison of the oil pressure depending on the engine RPM of the oil relief valve according to an exemplary embodiment of the present invention with the related art. 
     
    
    
     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. 
     In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
     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. 
     Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.  FIG. 3  is a diagram illustrating an oil relief valve according to an exemplary embodiment of the present invention,  FIG. 4  is a diagram illustrating an operation of the oil relief valve according to the exemplary embodiment of the present invention, and  FIG. 5  is a diagram illustrating a comparison of the oil pressure depending on the engine RPM of the oil relief valve according to an exemplary embodiment of the present invention with the related art, wherein the same parts as the related structure are denoted by the same reference numerals. 
     As illustrated in  FIG. 3 , the oil relief valve according to an exemplary embodiment of the present invention includes a relief valve including a valve hole  10  that is formed in a pump housing  100  of an oil pump and is provided between an oil passage  60  and a relief passage  50  to communicate therebetween and a relief valve provided in the valve hole  10 . The relief valve includes a plunger  20  that slidably moves vertically in the valve hole  10 , a spring  30  that elastically supports the plunger  20 , and a support  40  that supports the spring  30 . 
     The valve hole  10  has an upper end on which the plunger  20  of the relief valve is provided and a lower end on which the support  40  of the relief valve is provided. The upper end of the valve hole  10  is provided with an upper portion  11  that is a portion communicating with the oil passage  60  and a lower portion  12  of which one side communicates with the relief passage  50  and extends to a lower end of the valve hole  10 , wherein the upper portion  11  and the lower portion  12  are provided to have different cross sectional areas, that is, the cross sectional area of the upper portion  11  is formed to be smaller than that of the lower portion  12 . In this configuration, a connection portion of the upper portion  11  and the lower portion  12  is provided with an inclined portion  13  inclined downwardly. Therefore, oil discharged from the oil passage  60  is guided to the relief passage  50 . 
     The plunger  20  is provided on the upper end of the valve hole  10 . The plunger  20  is provided with an upper end  21  and a lower end  22 , wherein a cross sectional area of the upper end  21  is formed to be smaller than that of the lower end  22 . That is, when a vertically projected sectional area of the upper end  21  is referred to as A 1  and a vertically projected sectional area of the lower end  22  is referred to as A 2 , a ratio of A 1  to A 2  exceeds  1 . In this case, the upper end  21  of the plunger  20  face-contacts to the upper portion  11  of the upper portion of the valve hole  10  and the lower end  22  of the plunger  20  face-adheres to the lower portion  12  of the upper portion of the valve hole  10 . Further, when the relief valve is in a closed state, the upper end  21  of the plunger  20  is provided over the upper portion  11  and the lower portion  12  of the upper portion of the valve hole  10  and the lower end  22  of the plunger  20  is provided on the lower portion  12  of the upper portion of the valve hole  10  to stop the relief passage  50 , such that the closed state of the relief valve is maintained. At least one step  23  having different cross sectional areas may be provided between the upper end  21  and the lower end  22  of the plunger  20 . 
     In an exemplary embodiment of the present invention, step  23  may include a slanted portion  24  and is configured to selectively contact with the inclined portion  13  of the valve hole  10 . 
     The plunger  20  is provided so that a height of the upper end  21  of the plunger  20  is equal to or smaller than a height between an upper surface of the lower portion  12  of the lower end of the valve hole  10  and an upper surface of the relief passage  50 . That is, when the upper end  21  of the plunger  20 , that is, a height of a portion at which the cross sectional area is A 1  is set to be h 1  and a starting height of the A 2  sectional area of the valve hole  10 , that is, a height between the upper surface of the step  13  of the valve hole  10  and the upper surface of the relief passage  50  is set to be h 2 , a ratio of h 1  to h 2  is set to be 1 or less. The reason is that when h 1  is larger than h 2 , the lower end  22  of the plunger  20  still stops a relief passage  50  even though the spring  30  is pressed by the introduced oil. 
     The support  40  is provided on the lower end of the valve hole  10 . The support  40  is separately assembled or may be buried in the pump housing  100  or may be integrally provided with the pump housing  100 . 
     The spring  30  is provided between the support  40  and the plunger  20  to elastically support the plunger  20 . In this case, the spring elastically supports the plunger  20  upwardly. 
     An operation and a principle of the oil relief valve according to an exemplary embodiment of the present invention that is provided as described above will be described with reference to  FIGS. 4 and 5 . For convenience of explanation, a load pressing the spring  30  is set to be F, an oil pressure is set to be P, the cross sectional area of the upper end  21  of the plunger  20  is set to be A 1 , the cross sectional area of the lower end  22  of the plunger  20  is set to be A 2 , the spring constant is set to be k, and a displacement of the spring  30  is set to be x. 
     According to the oil relief valve of the exemplary embodiment of the present invention, the cross section of the plunger  20  is changed from A 1  to A 2  according to the operation area of the oil pressure at the time when the relief valve starts to open or in the vicinity of the time. Therefore, a force pressing the spring  30  is changed from F=P A 1  to F=P A 2 . Therefore, since A 2  is provided to be larger than A 1 , the force pressing the spring  30  increases as much as A 2 /A 1  times. As the force pressing the spring  30  increases A 2 /A 1  times, the displacement x of the spring  30  also increases A 2 /A 1  times, such that the bypassed flux of oil also increases. That is, the actuation speed of opening the relief valve increases. 
     Describing in more detail, when the oil pressure is ranging from 0 to 5 bar and above 5 bar in an actuation example, the cross sectional area of the plunger  20  is changed from A 1  to A 2 . Therefore, when the oil pressure P 1  in the oil pump is actuated in an area in which the oil pressure is ranging from 0 to 5 bar, a force F 1  pushing the relief valve downwardly by a contact surface A 1  of the upper end  21  of the plunger  20  vertical to the oil pressure P 1  is applied. That is, F 1 =P 1  A 1 . The spring force applied in the opposite direction becomes kx obtained by multiplying the spring constant k by the displacement x. Therefore, a resultant of force is F 1 −kx, such that the displacement of the spring  30  is determined and the opening and the closing of the oil relief valve that stops or opens the relief passage  50  by the displacement of the spring  30  are determined. When the oil pressure P 1  in the oil pump is actuated in the area in which the oil pressure is above 5 bar, a force F 2  pushing the relief valve downwardly by a contact surface A 2  of the lower end  22  of the plunger  20  vertical to the oil pressure P is applied. That is, F 2 =P 2  A 2 . The spring force applied in the opposite direction becomes kx obtained by multiplying the spring constant k by the displacement x. Therefore, a resultant of force is F 2 −kx, such that the displacement of the spring is determined and the opening and closing of the oil relief valve are determined. That is, when the oil pressure above 5 bar is actuated, the spring displacement x depends on the A 2  cross sectional area of the lower end  22  of the plunger  20 , such that the opening speed of the relief valve increases. In the present actuation example, the actuation area of the oil pressure is divided into two steps, but the step  23  having different cross sectional areas of the plunger  20  is provided at three stages or more, such that the actuation area of the oil pressure may be more subdivided. 
       FIG. 5  is a diagram illustrating a comparison of the change in an oil pressure depending on the engine RPM of the oil relief valve according to an exemplary embodiment of the present invention with the related art. As illustrated in  FIG. 5 , the response speed of the relief valve is faster than the related art until the relief valve is opened and then, becomes the full open state. Further, since the speed of opening the relief valve is fast, the bypassed amount of oil increases, such that the oil pressure shock may be reduced and the oil pressure trembling phenomenon may be improved. 
     As set forth above, the oil relief valve can change the force pressing the elastic member according to the change in the cross sectional area of the relief valve to increase the bypassed oil amount, thereby reducing the oil pressure shock, increasing the relief valve opening speed, and reducing the oil pressure trembling phenomenon. 
     For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner” and “outer” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
     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.