Patent Publication Number: US-2004041119-A1

Title: Pressure-regulating valve

Description:
BACKGROUND OF THE INVENTION  
       [0001] The present invention relates to a pressure-regulating valve.  
       [0002] From DE 195 01 447 A1, a pressure-regulating valve for a crank housing exhaust is known. This pressure-regulating valve has a closure body that can be actuated by a regulating membrane. As the material for the regulating membrane, typically elastomers, for example, fluosilicon, are used, which, however, have disadvantages. Fluosilicon is expensive in machining and as a raw material and in addition, has a high permeability for hydrocarbons, which is problematic in view of statutory regulations relating to hydrocarbon emissions. In addition, fluosilicon has only a limited chemical durability relative to oil, fuel, fuel additives, acids, and formaldehydes. The elastomer ECO is move advantageous than fluosilicon, however, may no longer be used in the future.  
       [0003] It is also disadvantageous that the elasticity or deformability of the elastomer is greatly decreased with the minus temperatures of winter and, thereby, the function of the pressure-regulating valve is greatly impaired.  
       [0004] In the non-published German patent application with the reference number 10201823.5, a pressure-regulating valve with a thermoplastic membrane is proposed. With a thermoplastic membrane, the omission of a separate spring for biasing of the membrane is possible. The function of the spring can be integrated into the membrane; a spring action of the thermoplastic membrane, however, is comparatively greatly dependent on temperature.  
       SUMMARY OF THE INVENTION  
       [0005] The pressure-regulating valve of the present invention, in contrast, has the advantage that in a simple manner, an improvement of the qualities compared with known pressure-regulating valves for adjusting the negative pressure in a crank housing of a motor vehicle is achieved, in which a metallic membrane is used. In the metallic membrane, a temperature-independent spring action for opening of the pressure-regulating valve is integrated, so that no separate spring is required. The metallic membrane assumes also the function of a housing cover. This simplifies the construction and minimizes manufacturing costs. The metallic membrane also has a high ability for sealing relative to hydrocarbons and is substantially cheaper than the elastomer membrane.  
       [0006] It is very advantageous if the membrane is made of stainless steel, since stainless steel has a high chemical durability relative to oil, fuel, fuel additives, acids, and formaldehydes.  
       [0007] It is particularly advantageous if a closing wall is provided as the closing body, which is a part of the metallic membrane. In this manner, the closing body can be eliminated, so that the pressure-regulating valve can be further simplified and the manufacturing costs lowered.  
       [0008] It is also advantageous if the metallic membrane is corrugated with valleys and elevations or if the membrane is graduated, since in this manner, a high elasticity is achieved. In the membrane, only bending tensions occur, which can be absorbed well by the membrane. Damaging tensile strains on a clamping position are avoided, so that a high longevity of the membrane is permitted.  
       [0009] It is also advantageous when a seal is arranged on a valve seat, on which the closing wall rests in the closed state of the pressure-regulating valve. The seal cushions the closing wall upon closing of the pressure-regulating valve and seals it off.  
       [0010] Furthermore, it is advantageous to provide a seal on the closing wall that cooperates with the valve seat, since in this manner, the valve seat is simplified and only comprises a level valve seat wall. A seal-receiving groove can be eliminated.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011] Embodiments of the invention are shown in a simple manner in the drawings and are explained in greater detail in the following description.  
     [0012]FIG. 1 shows a view in a longitudinal section of the pressure-regulating valve with a corrugated membrane; and  
     [0013]FIG. 2 shows a view in a longitudinal section of the pressure-regulating valve with a graduated membrane.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0014]FIG. 1 shows a pressure-regulating valve according to the present invention with a corrugated membrane. The inventive pressure-regulating valve is preferably used in a crank housing exhaust or vent, in order to regulate a pressure in a crank housing to a predetermined, constant valve by means of the spring force of the metallic membrane. However, it is also possible to use the pressure-regulating valve in other areas for a pressure regulation.  
     [0015] During operation of an internal combustion engine, gas, based on a small leakage between pistons, piston rings, and cylinder running surface, flows from a combustion chamber into a crank housing. This gas is designated as blow-by gas. The term “gas” will be used for the term “blow-by gas” in the following description. By means of the leakage, a pressure increase occurs in the crank housing, so that it is necessary to achieve a pressure balance by means of a so-called crank housing exhaust or vent. Since the gas has a high hydrocarbon concentration, it is not possible that the gas can be released into the atmosphere. The crank housing exhaust therefore leads the gas via the inventive pressure-regulating valve into a suction rube of the internal combustion engine, so that from there, it can be supplied to combustion.  
     [0016] In the crank housing, by means of the gas flowing in at high speeds and by means of moving parts in the crank housing, an oil mist with many small and large oil particles exists. These oil particles must be separated by the crank housing exhaust with the assistance of an oil separator, in order to avoid a high oil loss.  
     [0017] The inventive pressure-regulating valve comprises a housing  1  with an inlet channel  2  that is at least directly connected with the crank housing and an outlet channel  3 .  
     [0018] The cross section of the housing  1 , the inlet channel  2 , and the outlet channel  3  is round, for example. However, it is also possible that the cross section of the housing and/or the inlet channel  2  and/or the outlet channel  3  can be square, polygonal, or oval. The inlet channel  2  and the outlet channel  3  are connected with a recess  4  of the housing  1 . The outlet channel  3  and the recess  4 , for example, are centrally disposed on an axis  5  of the housing  1 . The inlet channel  2  is provided radially outward from the axis  5 . On an end of the outlet channel  3  facing the recess  4 , a valve seat  7  is provided, in which, for example, an annular seal  8  is arranged. The seal  8 , for example, is an O-ring. The seal  8  can also be eliminated, when an absolute seal on the valve seat  7  is not desired. The seal  8  is arranged in a sealing groove  9 , which is formed in a valve seat wall  10 . The valve seat  7  cooperates with a moveable, flat closing body wall  13 , which, for example, is a part of a membrane. If the closing body wall rests on the valve seat  7 , the connection, via the recess  4 , between the input channel  2  and the output channel  3  is broken and the pressure-regulating valve is closed. If the closing body wall  13  does not rest on the valve seat  7 , the pressure-regulating valve is opened. The closing body wall  13  is arranged in the recess  4  without an outer force action with spacing to the valve seat  7  between the valve seat wall  10  and a housing side  18 . The membrane  14  is made from metal, for example, stainless steel. The membrane is corrugated with valleys  15  and projections  16 . In this manner, a good elastic deformability, and therewith, a good spring action is achieved. In addition, only bending tensions occur in the material of the membrane  14 , which can be easily absorbed by the thin-walled membrane  14 . The corrugated form begins on the flat closing body wall  13 , which, for example, is round in cross section, and extends radially outward. The membrane  14  closes off the recess  4  relative to the surroundings and is attached to the housing  1 , for example, by a flanging  19  on a shoulder  17  near the housing side  18  of the housing  1 . In this manner, the membrane  14  also assumes the function of a housing cover of the housing  1 . The membrane  14 , however, also can be attached to the housing by means of adhesive, welding, or clamping. On the shoulder  17 , a second seal  21  is provided for sealing off the housing  1  from the surroundings. The seal  21 , for example, is a sealing ring arranged in a second sealing groove  22 . The second sealing groove  22  is arranged in the shoulder  17  on the housing side  18  facing the recess  4 .  
     [0019] With the pressure-regulating valve of FIG. 2, like parts or similarly operating parts as those of FIG. 1 are designated with the same reference numerals. The pressure-regulating valve according to FIG. 2 differs from the pressure-regulating valve of FIG. 2 in that the metallic membrane is graduated with steps  23  and the seal  8  is not provided on the valve seat  7 , rather on the closing body wall  13  of the membrane  14 . The seal  8 , for example, is vulcanized or adhered. The seal  8  can be eliminated, if no absolute seal on the valve seat  7  is desired.  
     [0020] The graduated form of the membrane  14  begins also on the closing body wall  13  and extends radially outward, whereby the steps  23  are arranged to be inclined radially outward from the closing body wall  13  in the direction of the housing side  18 . By means of the graduated form, a good elastic deformability and therewith, a good spring action is also achieved.  
     [0021] On the shoulder  17 , a second seal  21  for sealing the housing  1  from the surroundings is provided. The seal  21 , for example, is vulcanized or adhered to the membrane on a periphery of the shoulder  17  on an inner side of the membrane  14  facing the housing  1 . For sealing off the housing  1 , as in FIG. 1, a sealing ring in the second sealing groove  22  is also possible.  
     [0022] Since the pressure in the suction tube of the internal combustion engine sharply fluctuates and the crank housing is connected with the suction tube upon ventilation, the pressure fluctuations are expanded until in the crank housing. The pressure-regulating valve avoids this.  
     [0023] With an opened pressure-regulating valve, a inner chamber-pressure, which is predetermined from the pressure in the suction tube and the pressure in the crank housing, in an inner chamber  20  surrounded by the membrane  14  and the recess  4  is adjusted. The inner chamber-pressure is a negative pressure and acts on a large surface  25  of the membrane  14 .  
     [0024] With a closed pressure-regulating valve, only the inner chamber-pressure is adjusted, which is predetermined from the pressure in the crank housing, which is a very small negative pressure and acts on the large surface  25 , less a small surface  24 , of the membrane  14 . The prevailing negative or low pressure in the suction tube acts on the small surface  24 .  
     [0025] An equilibrium of forces is adjusted on the membrane  14 , on which a spring force of the membrane  14 , determined by the shape and thickness of the membrane, and a force resulting from the pressure difference of the inner chamber-pressure and surrounding pressure, are involved. With a closed pressure-regulating valve, additionally a suction force is involved, which results in the negative or low pressure prevailing in the suction tube and acting on the small surface  24 .  
     [0026] Depending on the equilibrium of forces, the pressure-regulating valve opens or closes.  
     [0027] As soon as the closing body wall  13  lies on the vale seat  7 , only a negative or low pressure acts on the small surface  24 . The spring force of the membrane  14  is laid out such that the pressure-regulating valve now is again open, so that again, a negative or low pressure acts on the large surface  25 . It adjusts an equilibrium, in which the closing body wall  13  has a constant distance to the valve seat wall  10 .  
     [0028] The spring force of the membrane  14  is configured such that the pressure-regulating valve is then closed in a safety position, when the negative or low pressure in the suction tube exceeds a predetermined value. This then prevents the crank housing from being suctioned empty by means of a high negative pressure.  
     [0029] By the construction of the spring force of the membrane  14 , the pressure can be determined, which is adjusted in the crank housing.  
     [0030] The smaller the distance between the closing body wall  13  and the valve seat wall  10  is, the smaller the volume flow of the blow-by gas in the suction tube is.  
     [0031] It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.  
     [0032] While the invention has been illustrated and described herein as a pressure-regulating valve, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.  
     [0033] Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.  
     [0034] What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.