Abstract:
A regulable hydraulic dashpot for motor vehicles and including a cylinder ( 1 ) filled with hydraulic fluid and a piston ( 2 ) that is attached to the end of a piston rod ( 7 ), travels back and forth inside the cylinder, and divides it into two chambers ( 3  &amp;  4 ) that communicate through at least one bypass. The bypass&#39;s cross-section can be varied in size by a component that is, preferably continuously, controlled by a motor or magnet. To facilitate adjusting the dashpot, the cross-section varying component is a plate-shaped slide ( 23 ) provided with one or more breaches ( 25 ) and traveling from side to side, preferably in a slot ( 24 ), with its flat surface ( 27 ) subjected to fluid from each cylinder chamber alternately by way of channels ( 14, 15,  &amp;  16 ).

Description:
BACKGROUND OF THE INVENTION 
     The present invention concerns regulable dashpots for motor vehicles and a method of adjusting such a dashpot. 
     Dashpots are manufactured regulable to allow adaptation of a motor vehicle&#39;s performance to given driving and road conditions. Additional regulable bypass valves are accordingly assigned to the shock-absorbing valves in the dashpot&#39;s piston. The regulation is usually carried out by way of electronic programs that control the level of attenuation in accordance with the results of such various measurements as vehicle speed, steering-wheel state, and travel dynamics. 
     A regulable dashpot is known from German 4 011 358 C1 and GB 2 222 227 A. These dashpots employ a motor to adjust a positioning component. The motor rotates or displaces a bell or rotating component in relation to a main interior bore provided with subsidiary radial bores. 
     These dashpots have drawbacks. The rotation or displacement requires both powerful adjustment forces and powerful retaining forces in that the rapid flow inside the bypass valve can lead to unintended self-adjustment and especially to total closing. This can have two results. Either the motor or the corresponding magnet is too large to fit inside the dashpot or some or all of the excess heat generated therein is too high to divert. Adjustments accordingly have to be undertaken outside the dashpot itself. This requirement, however, further aggravates the problems encountered in retention and control. 
     Another regulable dashpot of the genus is known from German 19 850 152 C1. The problems of powerful adjustment and stabilization forces are solved in this dashpot by hydraulically relieving a component of the controls, a stroke piston. 
     This embodiment, however, has the drawback that the controls component is composed of many parts. It also requires a complicated system of channels and check valves in that the hydraulic relief employs additional channels. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is a simpler controls component that will demand less powerful adjustment and retaining forces. 
     The present invention has several advantages. It exploits simple means to keep the adjustment and retaining forces low-powered. Of particular advantage from this aspect is that the valve will have a very high level of self-retention even when the pressure differences are extensive, counteracting any powerful induced adjustment forces. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One embodiment of the present invention will now be specified with reference to the drawing, wherein 
     FIG. 1 is a transverse section through a dashpot piston and bypass valve, 
     FIG. 2 a larger-scale detail of the bypass valve, 
     FIG. 3 illustrates the bypass valve illustrated in FIG. 2 rotated 90 °, 
     FIG. 4 is a transverse section similar to FIG. 1 but with the piston valves subjected to pressure, 
     FIG. 5 illustrates the bypass valve illustrated in FIG. 4 rotated 90 ° as in FIG. 3, 
     FIG. 6 is a section through the housing of a bypass valve with an optimized flow cross-section, 
     FIG. 7 is a spatial representation of the housing in FIG. 6, 
     FIG. 8 is a transverse section through another embodiment of the valve illustrated in FIG. 1, and 
     FIG. 9 depicts a single regulation-and-check valve located outside the dashpot cylinder. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The dashpot illustrated in FIG. 1 has a cylinder  1  divided into two chambers  3  and  4  by a piston  2 . Piston  2  is conventionally provided with unillustrated valves and is mounted by way of a threaded section  5  and nut  6  on the end of a piston rod  7  that travels back and forth inside cylinder  1 . 
     A bypass valve  8  is mounted around piston rod  7  either above piston  2  as illustrated or below it. Both bypass valve  8  and piston  2  are provided with backflow-preventing gaskets  9  and  10  in the form of cup springs. Bypass valve  8  and piston  2  communicate with the cylinder&#39;s upper chamber  3  by way of channels that will be specified hereinafter. 
     The lower end of piston rod  7  is provided with a central bore  11 . The upper end of bore  11  is occupied by a continuously variable bypass valve  12 , illustrated in detail in FIGS. 2 and 3. The body  13  of bypass valve  12  is penetrated by channels and by an annular compartment that allow communication between cylinder chambers  3  and  4 . In contrast to the one illustrated in FIG. 1, the bypass valve  12  in FIGS. 2 and 3 is accommodated in a cup  19  at the top of the central bore  11  in piston rod  7  rather then inside it. The aforesaid channels and compartment consist of an intake channel  14 , a controls channel  15 , and an annular compartment  16 . Intake channel  14  communicates hydraulically with central bore  11 , controls channel  15  opens into it at a right angle, and annular compartment  16  communicates hydraulically with upper cylinder chamber  3  by way of subsidiary bores  17  through the wall  18  of cup  19 . 
     Accommodated above bypass valve  12  is an electromagnet  20 . Its core  21  travels up and down continuously against the force exerted by a helical spring  22 . Core  21  is a component of the overall controls and is provided with a slide  23  in the form of a plate. Slide  23  extends at a right angle to controls channel  15  and is accommodated on all sides in a slot  24 . The slide  23  in the illustrated embodiment is a resilient tongue with a gable-shaped breach  25 . As long as bypass valve  12  is closed, breach  25  will rest below controls channel  15  and prevent fluid from flowing through it. The gabled shape of breach  25  allows bypass valve  12  to be opened a little at a time in that controls channel  15  can be initially actuated only by the breach&#39;s peak  26 . Controls channels and breaches of different shapes will occur to one of skill in the art as the occasion arises. Bypass valve  12  will be completely open once the cross-section of breach  25  is totally aligned with the cross-section of controls channel  15 . 
     As will be immediately evident from FIGS. 1 and 2, any considerable difference between the pressure of the fluid in upper cylinder chamber  3  and that in lower cylinder chamber  4  will force the flat surfaces  27  of slide  23  against the opposing surfaces of slot  24 , automatically closing off the slide&#39;s accommodation. Hence, electromagnet  20  will need to exert almost no retaining force. 
     Once the level of pressure in upper cylinder chamber  3  equals that of the pressure in lower cylinder chamber  4 , primarily once piston rod  7  has arrived at its point of return, that is, the self-inhibition will be canceled. Slide  23  will be easily accessible inside slot  24  and can be adjusted without exerting a great deal of force. Since the piston rod in a dashpot arrives very frequently at its upper and lower points of return, finely tuned regulation will be possible even when adjustment is carried out only at those times. The controls slide can accordingly be regulated in various ways. Electromagnet  20  can for example be turned on at low current. When the difference in cylinder-chamber pressures is high in this event, the closing forces exerted on the slide  23  will be so powerful that the magnet will be unable to handle them, and adjustment will occur only as piston rod  7  travels through its point of return. Alternatively, the controls can intentionally be set to ensure that adjustment occurs only at that point. 
     The dashpot illustrated in FIG. 4 also has a cylinder  1  divided into two chambers  3  and  4  by a piston  2 . Piston  2  is conventionally provided with attenuating valves  28  and  29  and fastened by a threaded section  5  and a nut  6  and by way of a controls housing  30  and a cup  19  to a piston rod  7  that travels back and forth inside cylinder  1 . Controls housing  30  essentially accommodates an electromagnet  20  with a core  21  that travels continuously or incrementally back and forth against the force exerted by a helical spring  22 . Electromagnet  20  is screwed onto piston rod  7 . Piston rod  7  is hollow and accommodates electrical connections  31 . Electromagnet  20  and controls housing  30  can, as in the illustrated embodiment, comprise a single component. 
     Cup  19  is screwed onto a threaded section at the lower end of controls housing  30 . The lower end of cup  19  is provided with a pin  32  that accommodates piston  2  and with further components that will be specified hereinafter. At least two subsidiary bores  33  and  34 , components of a system of channels, extend axially parallel through pin  32 . 
     Exterior compression compartments  37  and  38  border on channels  35  and  36  that penetrate piston rod  7  and are closed off by attenuating valves  28  and  29 . Compression compartments  37  and  38  comprise housings  39  and  40  anneals  41  and  42  that move relative to them and rest on attenuating valves  28  and  29 . Housings  39  and  40 , seals  41  and  42 , attenuating valves  28  and  29 , and piston  2  rest against and enclose piston-accommodating pin  32  and are secured to it by nut  6 . Compression compartments  37  and  38  communicate with subsidiary bores  33  and  34  through radial accesses  43  and  44  that extend through compression-compartment housings  39  and  40  and the wall of piston-accommodating pin  32 . 
     The top of cup  19  accommodates a controls valve with a body  13 . Subsidiary bores  33  and  34  continue on into valve body  13  and communicate with each other and with an annular compartment  16  through a transverse channel  46 . Annular compartment  16  communicates hydraulically with upper cylinder chamber  3  by way of subsidiary bores  17 . 
     Mounted on the core  21  of electromagnet  20  is a slide  23  in the form of a flat plate, also evident in FIG.  2 . Slide  23  extends at a right angle to transverse channel  46  between the outlets of subsidiary bores  33  and  34  and is accommodated on all sides in a slot  24 . 
     As long as the controls valve is closed, in the state represented in FIGS. 1 and 2, compression compartments  37  and  38  will communicate hydraulically with their associated chambers  4  and  3 . Compression compartment  38  will communicate with upper cylinder chamber  3  by way of radial access  44 , subsidiary bore  33 , transverse channel  46 , annular compartment  16 , and subsidiary bores  17 , and compression compartment  37  with lower cylinder chamber  4  by way of radial access  43 , and subsidiary bore  34 , supporting the level of pressure against attenuating valves  28  and  29  by way of compression compartments  37  and  38 . Partial or total opening of the controls valve will now both create a bypass between upper cylinder chambers  3  and  4  by way of subsidiary bore  34 , transverse channel  46 , and subsidiary bores  17  and reduce the pressure in compression compartments  37  and  38 . 
     The slide  23  in the illustrated example is a resilient tongue provided with a gable-shaped breach  25 . As long as the controls valve is closed, breach  25  will rest below transverse channel  46  and prevent fluid from flowing through it. The gabled shape of breach  25  allows the controls valve to be opened a little at a time in that the valve can be initially actuated only by the breach&#39;s peak  26 . Transverse channels and breaches of different shapes will occur to one of skill in the art as the occasion arises. The controls valve will be completely open once thecross-section of breach  25  is totally aligned with the cross-section of transversechannel  46 . 
     What has been specified hereintofore with respect to self-inhibition and adjustment on the part of the slide  23  depicted in FIGS. 2 and 3 also applies to the embodiment illustrated in FIGS. 4 and 5. 
     FIG. 6 shows a piston system like the one illustrated in FIG. 1 with piston  2  screwed onto a bypass valve  8  located below it. 
     Bypass valve  8  is a “for-convenience” valve, active only in the suction direction. It is accordingly provided only with a single backflow-preventing gasket  9 . The same valve, however, could just as well act in both the suction and the compression directions. A double degressive valve could also be employed. 
     The channel through valve body  13  has been optimized for flow. The section of controls channel  15  toward upper cylinder chamber  3  extends in a plane more or less perpendicular to the axis of the piston rod. It expands in both height and width, starting at slide  23 . This section of controls channel  15  terminates in a circumferentialsection  47 . The wall  18  of cup  19  is provided with a matching cutout  48 . 
     The section of controls channel  15  that opens into central bore  11  extends smoothly into intake channel  14  and also expands starting at slide  23  and curves, terminating more or less at the center of the lower surface of valve body  13 , where it merges into central bore  11 . 
     FIG. 7 is a spatial representation of the valve body  13  depicted in FIG.  6 . 
     FIG. 8 illustrates another embodiment of the valve system illustrated in FIG. 1 but represents only the structure of the controls valve in conjunction with the bypass piston and the cup. 
     The cup  19  in the embodiment illustrated in FIG. 8 accommodates and secures a bypass valve  8  along with its body  13 . Both components are mounted against and fastened to the cup&#39;s wall  18 . Wall  18  is provided with an inside thread, by way of which it is screwed onto electromagnet  20 . The controls channel  15  and intake channel  14  are similar to the ones illustrated in FIGS. 6 and 7 except that the intake channel need not terminate more or less atthe center of the lower surface of valve body  13 . As in the embodiment illustrated in FIG. 1, bypass valve  8  is provided with two backflow-preventing gaskets  9  and  10 , which have a corresponding attenuation function. The central bore  11  extends through a pin-like cup-supporting bolt  49 . An unillustrated piston is secured to bolt  49  by a nut  6 . 
     The embodiment illustrated in FIG. 9 has a single regulation-and-check valve accommodated in a separate cup-shaped housing  50 . Regulation-and-check valves of this species are employed to control bypasses in regulable dashpots when there is not enough height or space to accommodate them. Such valves are mounted on the outside of the dashpot&#39;s cylinder. The cylinder  1  in the present embodiment is penetrated by controls channels that communicate with intakes  51  and  52  into the, separate, valve. Although the regulation-and-check valve illustrated in FIG. 9 is generally similar to the valve illustrated in FIG. 8, it is, like the one illustrated in FIG. 6, provided with only one backflow-preventing gasket  9  for bypass valve  8 . Controls channel  15  communicate directly with controls intake  51 . The intake channel  14  terminates, eccentric in the present example, above bypass valve  8  at the lower surface of valve body  13 . Bypass valve  8  communicates hydraulically with intake channel  14 . As long as there is pressure in controls intake  51  and as long as slide  23  is more or less open, backflow-preventing gasket  9  will remain elevated above the bore  53  through bypass valve  8 , keeping the hydraulic communication with a hydraulics compartment  54  open. The regulation-and-check valve will now communicate again by way of controls intake  52  with the hydraulic region of the regulable dashpot that is to be supplied with pressure. The structure of the base  55  has been optimized to further reduce impedance. 
     Two or more regulation-and-check valves like those illustrated in FIG. 9 can be mounted on the cylinder of a single regulable dashpot. These components could also be accommodated in a housing  50  associated with several regulation-and-check valves, communicating hydraulically with one another in accordance with the specific purpose. 
     List of Parts 
     1. hydraulic cylinder 
     2. piston 
     3. upper cylinder chamber 
     4. lower cylinder chamber 
     5. threaded section 
     6. nut 
     7. piston rod 
     8. bypass 
     9. backflow-preventing gasket 
     10. backflow-preventing gasket 
     11. central bore 
     12. bypass valve 
     13. valve body 
     14. intake channel 
     15. controls channel 
     16. annular compartment 
     17. subsidiary bore 
     18. wall 
     19. cup 
     20. electromagnet 
     21. core 
     22. spring 
     23. slide 
     24. slot 
     25. breach 
     26. peak 
     27. surface of slide  23   
     28. shock-absorbing valve 
     29. shock-absorbing valve 
     30. controls housing 
     31. electrical connections 
     32. piston-accommodating pin 
     33. subsidiary bore 
     34. subsidiary bore 
     35. piston-penetrating channel 
     36. piston-penetrating channel 
     37. compression compartment 
     38. compression compartment 
     39. compression-compartment housing 
     40. compression-compartment housing 
     41. compression-compartment seal 
     42. compression-compartment seal 
     43. radial access 
     44. radial access 
     45. controls valve 
     46. transverse channel 
     47. circumferential section 
     48. cutout 
     49. cup-supporting bolt 
     50. housing 
     51. controls intake 
     52. controls intake 
     53. bore 
     54. hydraulics compartment 
     55. base