Patent Publication Number: US-2010109428-A1

Title: Vibration isolation mechanism for coil spring and booster using the same

Description:
BACKGROUND ART 
     The present invention relates to a technical field of a vibration isolation mechanism for a coil spring, used in various devices, such as negative-pressure boosters, fluid-pressure boosters, etc., in which an input applied to input means is boosted by power to be output, and more particularly, to a technical field of a vibration isolation mechanism for a coil spring, capable of suppressing an abnormal noise generated by vibrations in a mounted state, and a booster using the same. 
     In a brake system for automobiles, a fluid-pressure booster, in which a fluid pressure boosts a pedal treading force to generate a large output force, is frequently adopted in order to enable obtaining a large braking force even with a small pedal treading force. As one of such fluid-pressure boosters, there is well known a negative-pressure booster, in which a negative pressure as power boosts a pedal treading force to obtain a large output force. 
       FIG. 6  is a cross sectional view showing such conventional, general negative-pressure booster. In the figure, the reference numeral  1  denotes a negative-pressure booster,  2  a front shell,  3  a rear shell,  4  a power piston member, a diaphragm,  6  a power piston,  7  a constant-pressure chamber maintained at a negative pressure,  8  a variable pressure chamber, into which the atmosphere is introduced in operation,  9  a valve body,  10  an input shaft,  11  a valve plunger,  12  a atmosphere valve seat provided on the valve plunger  11 ,  13  a negative-pressure valve seat provided on the valve body  9 ,  14  a control-valve body,  15  a control valve,  16 ,  17 ,  18  passage holes,  19  an output shaft,  20  a return spring that biases the power piston  6  toward a non-operation position at all times,  21  a reaction disk,  22  a negative-pressure introducing pipe, and  23  an atmosphere inlet port. 
     In the negative-pressure booster  1 , a negative pressure is introduced through the negative-pressure introducing pipe  22  into the constant-pressure chamber  7  at all times. In a state, in which the negative-pressure booster  1  is not operated, the atmosphere valve seat  12  of the control valve  15  abuts against the control-valve body  14  and the control-valve body  14  is slightly separated from the negative-pressure valve seat  13 , so that the control valve  15  is put in a non-operating state. Accordingly, the variable pressure chamber  8  is cut off from the atmosphere and communicated to the constant-pressure chamber  7  through a clearance between the passage holes  17 ,  16  and the control-valve body  14  and the negative-pressure valve seat  13 , and through the passage hole  18 , and so a negative pressure is introduced into the variable pressure chamber  8 . 
     When a brake pedal (not shown) is trodden from such non-operating state, the input shaft  10  makes a stroke forward (leftward in  FIG. 6 ), the control-valve body  14  is seated on the negative-pressure valve seat  13 , and then the atmosphere valve seat  12  separates from the control-valve body  14 . That is, the control valve  15  is switched over. Thereby, the variable pressure chamber  8  is cut off from the constant-pressure chamber  7  and communicated to the atmosphere. Then, the atmosphere is introduced into the variable pressure chamber  8  through a clearance between the control-valve body  14  and the atmosphere valve seat  12  and through the passage holes  16 ,  17 . Thereby, a differential pressure is generated between the variable pressure chamber  8  and the constant-pressure chamber  7 , so that the power piston  6  comprising the power piston member  4  and the diaphragm  5  advances (moves leftward) to generate an output. The output is transmitted to a brake master cylinder (not shown) through the valve body  9 , the reaction disk  21 , and the output shaft  19 . Then, the brake master cylinder is actuated to generate a braking pressure. 
     Since a reaction force produced by the braking pressure of the brake master cylinder causes the output shaft  19  to push the reaction disk  21 , the reaction disk  21  is pressingly interposed between the valve body  9  and the output shaft  19  to be elastically deformed to abut against the valve plunger  11 . Then, a force produced by the elastic deformation of the reaction disk  21  is transmitted as a reaction force to a brake pedal through the valve plunger  11  and the input shaft  10 . 
     As the variable pressure chamber  8  is increased in pressure, an output of the power piston  6  is increased to cause the valve body  9  to advance further, so that the control-valve body  14  abuts against the atmosphere valve seat  12  while maintaining a state of being seated on the negative-pressure valve seat  13 . Thereby, the atmosphere is not further introduced into the variable pressure chamber  8  and so a pressure in the variable pressure chamber  8  becomes one corresponding to an input (a force related to a pedal treading force) applied to the input shaft  10 . An output of the power piston  6  at this time becomes a large output obtained by boosting the pedal treading force, with the result that a master cylinder generates a braking pressure corresponding to an input of the input shaft  10 . A brake is actuated by the braking pressure of the master cylinder. A braking force at this time becomes one obtained by boosting the pedal treading force. 
     When the brake pedal is released, both the input shaft  10  and the valve plunger  11  retreat and the control-valve body  14  is unseated from the negative-pressure valve seat  13 . Then, the variable pressure chamber  8  is communicated to the constant-pressure chamber  7  and the atmosphere introduced into the variable pressure chamber  8  is discharged from the negative-pressure introducing pipe  22  through the passage holes  17 ,  16 , a clearance between the control-valve body  14  and the negative-pressure valve seat  13 , the passage hole  18 , and the constant-pressure chamber  7 . Thereby, the variable pressure chamber  8  is decreased in pressure and a spring force of the return spring  20  causes all the valve body  9 , the power piston  6 , and the output shaft  19  to retreat to come to a non-operating position and the control valve  15  is put in a non-operating state shown in the figure. Thus, with the negative-pressure booster  1 , a large output can be obtained by a small pedal treading force. 
     By the way, a coil spring is generally used for the return spring  20  of the negative-pressure booster  1 . The coil spring is normally formed from a spring wire material to comprise seat winding portions (portions of a first turn) wound substantially one turn at both ends in a plane perpendicular to a length direction of the coil spring and a coil portion wound spirally and continuously between the seat winding portions. Ordinarily, with a coil spring of this kind, minute clearances are produced between portions of the seat winding portions and portions of second turn portions. 
     In this manner, when minute clearances are produced between portions of the seat winding portions and portions of second turn portions, a spring property of the return spring  20  vibrates the power piston  6  when the negative-pressure booster  1  operates with the brake pedal being trodden to cause the power piston  6  to advance. Since vibrations of the power piston  6  are transmitted to the brake pedal through the reaction disk  21 , the valve plunger  11 , and the input shaft  10 , there is caused a problem that a pedal feeling is deteriorated. Also, the coil spring vibrates due to vibrations of the power piston  6 , and when the coil spring vibrates, there is caused a problem that an abnormal noise generates since portions of the seat winding portions and portions of second turn portions, which are separated from each other with minute clearances therebetween, contact with each other. 
     Hereupon, for example, JP-A-2006-341790 and JP-A-2006-77904 propose boosters, in which portions in predetermined ranges of second turns of a coil spring are brought into close contact with seat winding portions to prevent an abnormal noise from being generated upon contact and separation between portions of the second turns and portions of the seat winding portions even when the coil spring vibrates. 
     In that structure, in which portions in predetermined ranges of second turns of a coil spring are brought into close contact with seat winding portions as described above, however, it is difficult to surely damp vibrations of the coil spring. Besides, in order to effectively prevent the generation of an abnormal noise due to vibrations of the coil spring, it is necessary to accurately and strictly control an extent of close contact between portions of the second turns and the seat winding portions and dimensions of closely contacted regions, or the like. Therefore, there is caused a problem that a vibration isolation mechanism for a coil spring is not so much favorable in productivity and high in cost. 
     DISCLOSURE OF THE INVENTION 
     It is an object of the invention to provide a vibration isolation mechanism for a coil spring, which can be improved in productivity while damping vibrations of the coil spring to suppress the generation of an abnormal noise, and a booster using the same. 
     Also, it is a further of the invention to provide a booster that damps vibrations caused by a coil spring, which constitutes a return spring of a power piston, to enable making an operating feeling favorable. 
     In order to attain the object, a vibration isolation mechanism for a coil spring, according to the invention, includes a coil spring having seat winding portions at both ends and a coil portion provided continuously between the seat winding portions, and a spring retainer supporting one of the seat winding portions, the spring retainer including a pair of holding portions, which hold one of the seat winding portions. 
     Also, the vibration isolation mechanism for a coil spring, according to the invention, has a feature in that one holding portion of the pair of holding portions holds at least an outer peripheral side of the seat winding portion of the coil spring and the other holding portion holds at least an inner peripheral side of the seat winding portion of the coil spring. 
     Further, the vibration isolation mechanism for a coil spring, according to the invention, has a feature in that an opposite surface of the spring retainer to a surface thereof toward the coil spring is supported on a spring retainer supporting member both in an axial direction and in a radial direction. 
     Further, the vibration isolation mechanism for a coil spring, according to the invention, has a feature in that the spring retainer includes a first retainer and a second retainer, one holding portion of the pair of holding portions is provided on the first retainer, and the other holding portion of the pair of holding portions is provided on the second retainer. 
     Further, the vibration isolation mechanism for a coil spring, according to the invention, has a feature in that one holding portion of the first retainer holds at least an outer peripheral side of the seat winding portion of the coil spring and the other holding portion of the second retainer holds at least an inner peripheral side of the seat winding portion of the coil spring. 
     Further, the vibration isolation mechanism for a coil spring, according to the invention, has a feature in that the other holding portions are provided at equal intervals in a predetermined number of locations in a circumferential direction. 
     Further, the vibration isolation mechanism for a coil spring, according to the invention, has a feature in that openings being the same in number as the other holding portions are formed at equal intervals on the first retainer in a circumferential direction and the other holding portions extend through the corresponding openings from an opposite side to the coil spring. 
     Further, the vibration isolation mechanism for a coil spring, according to the invention, has a feature in that the second retainer is supported on a spring retainer supporting member both in an axial direction and in a radial direction and the first retainer is supported on the spring retainer supporting member in a radial direction. 
     On the other hand, the booster according to the invention includes at least a power piston actuated by the action of power corresponding to an input to boost the input to output the same, and a return spring that biases the power piston toward a position of non-operation, the booster being characterized by including that vibration isolation mechanism for a coil spring, which prevents vibrations of the coil spring, the vibration isolation mechanism for a coil spring being the coil spring according to any one of claims  1  to  8 . 
     With the vibration isolation mechanism of the invention for a coil spring thus structured in this manner, the pair of holding portions provided on the spring retainer hold the seat winding portion of the coil spring, so that even when the coil spring vibrates, vibrations thereof can be forcedly damped. Accordingly, even when a minute clearance is produced between the seat winding portion and a second turn portion of the coil spring, it is possible to effectively suppress the generation of an abnormal noise. 
     Also, it does not matter whether a minute clearance is produced between the seat winding portion and a second turn portion of the coil spring, it gets along without accurately and strictly controlling an extent of close contact between the second turn portion and the seat winding portion and dimensions of closely contacted regions, or the like, so that a vibration isolation mechanism for a coil spring can be improved in productivity and decreased in cost. 
     On the other hand, with the booster according to the invention, a return spring of a power piston includes a coil spring and vibrations caused by the coil spring in operation are damped to enable suppressing the generation of an abnormal noise, so that it is possible to make an operating feeling of the booster favorable and to decrease the booster in cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view partially showing a negative-pressure booster, to which an example of an embodiment of a vibration isolation mechanism for a coil spring, according to the invention, is applied. 
         FIG. 2  shows a pedestal retainer, which constitutes a spring retainer shown in  FIG. 1 ,  FIG. 2(   a ) being a front view, and  FIG. 2(   b ) being a cross sectional view taken along the line II-II in  FIG. 2(   a ). 
         FIG. 3  shows a holding retainer, which constitutes the spring retainer shown in  FIG. 1 ,  FIG. 3(   a ) being a front view, and  FIG. 3(   b ) being a cross sectional view taken along the line III-III in  FIG. 3(   a ). 
         FIG. 4  is a cross sectional view partially showing a negative-pressure booster, to which a further example of an embodiment of a vibration isolation mechanism for a coil spring, according to the invention, is applied. 
         FIG. 5  shows a pedestal retainer being a spring retainer shown in  FIG. 4 ,  FIG. 5(   a ) being a front view, and  FIG. 5(   b ) being a cross sectional view taken along the line V-V in  FIG. 5(   a ). 
         FIG. 6  is a cross sectional view showing an example of a conventional negative-pressure booster. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     A best mode for carrying out the invention will be described with reference to the drawings. 
       FIG. 1  is a cross sectional view partially showing a negative-pressure booster, to which an example of an embodiment of a vibration isolation mechanism for a coil spring, according to the invention, is applied. In addition, in the following descriptions, the same constituents as those in an example or examples preceding an associated example and a conventional example shown in  FIG. 6  are denoted by the same reference numerals as those in the latter, and so a detailed explanation therefor is omitted. 
     A booster, to which a vibration isolation mechanism for a coil spring, according to the example, is applied, is a negative-pressure booster  1  used in a brake booster, etc. The negative-pressure booster  1  is different only in a partial construction from the conventional negative-pressure booster  1  shown in  FIG. 6  but the same in a major construction as the conventional negative-pressure booster  1 . Accordingly, an explanation will be given only to the construction of that part of the negative-pressure booster  1  of this example, which is different from the conventional negative-pressure booster  1 . 
     As shown in  FIG. 1 , with the negative-pressure booster  1  of this example, an end of a return spring  20 , which includes a coil spring, toward a valve body  9  is supported on the valve body  9  with a spring retainer  24  therebetween. The spring retainer  24  includes a pedestal retainer  25  (corresponding to a first retainer in the invention), which directly supports the end of the return spring  20  in a fore and aft direction (a left and right direction in  FIG. 1 ), and a holding retainer  26  (corresponding to a second retainer in the invention), which elastically holds a seat winding portion  20   a  being a first turn of the return spring  20 . 
     As shown in  FIGS. 2(   a ) and  2 ( b ), the pedestal retainer  25  is substantially the same in structure as the spring retainer used in the conventional and general negative-pressure booster  1 . That is, the pedestal retainer  25  includes a stepped, annular disk portion  27  having an annulus step  27   c  so that a flat, center portion  27   a  is positioned forwardly (leftward in  FIG. 2(   b )) of a flat, outer peripheral portion  27   b  disposed therearound, and a cylindrical-shaped guide support  28 , which is concentric with the center portion  27   a  of the stepped, annular disk portion  27  to project forward. 
     A predetermined number (eight in the example as shown) of openings  29  are formed circumferentially at equal intervals on the outer peripheral portion  27   b  of the stepped, annular disk portion  27 . Also, an annulus flange  30  projecting forward is formed on an outer peripheral edge of the outer peripheral portion  27   b . The flange  30  includes an annulus holding portion  30   a , which holds an outer peripheral side of the seat winding portion  20   a  of the return spring  20 , and an annular guide portion  30   b , which is in the form of a frustum to project divergingly forwardly of the holding portion  30   a.    
     As shown in  FIG. 1 , the guide support  28  is fitted onto an output shaft  19  to radially position the spring retainer  24  so as to make the same concentric with the output shaft  19 . 
     As shown in  FIGS. 3(   a ) and  3 ( b ), the holding retainer  26  is formed to assume the shape of an annulus and holding pawls  31  being the same in number as the openings  29  of the stepped, annular disk portion  27  are provided protrusively at an inner peripheral edge of the holding retainer  26  to be spaced equally forward in an axial direction and in a circumferential direction. Provided on the holding pawls  31 , respectively, are a holding portion  31   a  composed of a curved recess, which elastically holds an inner peripheral side of the seat winding portion  20   a  of the return spring  20 , and an annular guide portion  31   b , which is in the form of a frustum to project divergingly forwardly of the holding portion  31   a . The respective holding pawls  31 , respectively, can extend through corresponding openings  29  of the stepped, annular disk portion  27 . Also, an annulus flange  32  is provided protrusively rearward (leftward in  FIG. 3(   b )) at an outer peripheral edge of the holding retainer  26 . 
     As shown in  FIG. 1 , the spring retainer  24  is formed by having the holding pawls  31  of the holding retainer  26 , respectively, extending through the respective openings  29  of the pedestal retainer  25  from the rear (an opposite side to the flange  30  of the pedestal retainer  25 , that is, an opposite side to the return spring  20 ) and integrally assembling the holding retainer  26  to the pedestal retainer  25 . 
     The annulus flange  32  of the holding retainer  26  is fitted onto an outer periphery of a large-diameter forward end  9   a  of the valve body  9  and the annulus step  27   c  of the pedestal retainer  25  is fitted onto a small-diameter forward end  9   b  of the valve body  9 , whereby the spring retainer  24  is assembled to the valve body  9 . 
     In this manner, in a state, in which the spring retainer  24  is assembled to the valve body  9 , an annulus holding space is formed between the holding portion  30   a  of the flange  30  and the holding portions  31   a  of the holding pawls  31 . Then, an end of the return spring  20  toward the valve body  9  is fitted between the guide portion  30   b  of the flange  30  and the guide portions  31   b  of the holding portions  31   a  of the holding pawls  31  rearward in an axial direction from the front. Then, the holding pawls  31  are elastically spread, so that the seat winding portion  20   a  of the return spring  20  enters into the holding space between the holding portion  30   a  and the holding portions  31   a  as shown in  FIG. 1 . In this state, since the holding pawls  31  are elastically restored, the seat winding portion  20   a  of the return spring  20  is elastically and firmly held between the holding portion  30   a  and the holding portions  31   a.    
     Thereby, even when the power piston  6  vibrates, vibrations of the return spring  20  are forcedly damped, so that the generation of an abnormal noise is effectively suppressed even when a minute clearance is generated between the seat winding portion and the second turn portion of the return spring  20 . In this manner, the vibration isolation mechanism for a coil spring, according to the invention, includes the holding portion  30   a  of the pedestal retainer  25  and the holding portions  31   a  of the holding retainer  26 . 
     Also, an inner peripheral surface of the annulus step  27   c  of the pedestal retainer  25  is supported radially on an outer periphery of the small-diameter forward end  9   b  of the valve body  9  and an opposite surface of the pedestal retainer  25  to the return spring  20  is supported on a surface of the holding retainer  26  toward the return spring  20  in an axial direction of the return spring  2 , so that the pedestal retainer  25  is positioned radially and axially relative to the valve body  9  (In addition, the pedestal retainer  25  is positioned axially through the holding retainer  26 ). Accordingly, the valve body  9  constitutes a spring retainer supporting member of the invention. 
     Further, an inner peripheral surface of the annulus flange  32  of the holding retainer  26  is supported radially on an outer periphery of the large-diameter forward end  9   a  and an opposite surface of the holding retainer  26  to a surface of the return spring  20  is supported on the valve body  9  in axial directions of the return spring  2  and the valve body  9 , so that positioning is accomplished both in a radial direction and in an axial direction. 
     With the vibration isolation mechanism, according to the example, for the return spring  20 , the seat winding portion  20   a  of a coil spring, which constitutes the return spring  20 , is held between the holding portion  30   a  of the pedestal retainer  25  and the holding portions  31   a  of the holding retainer  26 , so that even when the power piston  6  vibrates, it is possible to forcedly damp vibrations of the return spring  20 . Accordingly, even when a minute clearance is generated between the seat winding portion and the second turn portion of the return spring  20 , it is possible to effectively suppress the generation of an abnormal noise caused by vibrations of the return spring  20 . 
     Also, since it does not matter whether a minute clearance is generated between the seat winding portion and the second turn portion of the return spring  20 , it gets along without accurately and strictly controlling an extent of close contact between the second turn portion and the seat winding portion and dimensions of closely contacted regions, or the like, so that the vibration isolation mechanism for the return spring  20  can be improved in productivity and decreased in cost. 
     Further, with the negative-pressure booster  1  provided with the vibration isolation mechanism of the example for the return spring  20 , the return spring  20  of the power piston  6  includes a coil spring and vibrations caused by the coil spring in operation are damped to enable suppressing the generation of an abnormal noise, so that it is possible to make an operating feeling of the negative-pressure booster  1  favorable and to decrease the negative-pressure booster  1  in cost. 
     Other constitution, functions, and effects of the negative-pressure booster  1  according to the example are the same as those in the conventional negative-pressure booster  1  shown in  FIG. 6 . 
       FIG. 4  is a cross sectional view partially showing a negative-pressure booster, to which a further example of an embodiment of a vibration isolation mechanism for a coil spring, according to the invention, is applied. 
     While the spring retainer  24  in the example described above includes two members, that is, the pedestal retainer  25  and the holding retainer  26 , with a vibration isolation mechanism, according to the present example, for a coil spring, a spring retainer  24  includes a single member, that is, a pedestal retainer  25 . 
     As shown in  FIGS. 5(   a ) and  5 ( b ), the pedestal retainer  25  is almost the same in structure as the pedestal retainer  25  shown in  FIGS. 2(   a ) and  2 ( b ), but the pedestal retainer  25  is partially different from the pedestal retainer  25  of the example described above. That is, a predetermined number (eight in the example as shown) of openings  29  formed on the pedestal retainer  25  are provided with holding pawls  31 , which are the same in number as the openings  29 . All the holding pawls  31  are quite the same in structure as the holding retainer  26  shown in  FIGS. 3(   a ) and  3 ( b ). That is, the holding pawls  31  include a holding portion  31   a  composed of a curved recess, which elastically holds a seat winding portion  20   a  of a return spring  20 , and an annular guide portion  31   b , which is in the form of a frustum to project divergingly forwardly of the holding portion  31   a.    
     With the vibration isolation mechanism of the example for a coil spring, thus structured in this manner, the pedestal retainer  25  is assembled to a valve body  9  and an output shaft  19  of the negative-pressure booster  1  in the same manner as in the example described above. In the same manner as in the example described above, the seat winding portion  20   a  of the return spring  20  toward the valve body  9  is elastically and firmly held between a holding portion  30   a  and the holding portions  31   a.    
     With the vibration isolation mechanism of the example for a coil spring, the spring retainer  24  is composed of only a single member, that is, the pedestal retainer  25 , so that it is possible to reduce parts in number to achieve a decrease in cost and to assemble the spring retainer  24  simply. 
     Other constitution, functions, and effects of the negative-pressure booster  1  provided with the vibration isolation mechanism of the example for a coil spring are the same as those in the negative-pressure booster  1  of the example described above and in the conventional negative-pressure booster  1  shown in  FIG. 6 . 
     INDUSTRIAL APPLICABILITY 
     The vibration isolation mechanism, according to the invention, for a coil spring can be preferably made use of for a vibration isolation mechanism for a coil spring, which is mounted in a state of being applied by a preset compressive set load and on which an externally operating force is exerted. 
     Also, the booster according to the invention can be preferably made use of for a booster system and a booster, in which an operating force of an operator is boosted to be used, as well as for a booster of a brake system.