GB2320071A

GB2320071A - Booster e.g.for the brake system of an automobile

Info

Publication number: GB2320071A
Application number: GB9718111A
Authority: GB
Inventors: Masahiro Ikeda
Original assignee: Jidosha Kiki Co Ltd
Current assignee: Jidosha Kiki Co Ltd
Priority date: 1994-02-28
Filing date: 1995-02-06
Publication date: 1998-06-10
Anticipated expiration: 2015-02-06
Also published as: GB2320071B; GB9718111D0

Abstract

A booster e.g. for the brake system of an automobile comprises means to reduce the generation of sounds when pressure fluid is introduced into a variable pressure chamber (B, Figure 1) from a pressure passage 23 via a variable pressure passage 21 in valve body 6, which variable pressure passage has an uneven surface. The uneven surface improves the muffler effect without degrading the response of the booster. The uneven surface may be provided by grooves in the surface or in synthetic resin 35 covering the surface, a plurality of steps (106b, 106c, Figure 5), a spiral or annular groove(s) (306d, Figure 7), a deposit of synthetic resin (406d, Figure 8), or a coil spring or rings press (506b, Figure 9) fitted into the valve body.

Description

BOOSTER The invention relates to a booster as may be used in a brake of an automobile, for example, and more particularly, to a muffler for booster which reduces the generation of noise as a pressure fluid is introduced into a variable pressure chamber of the booster.

A booster is known in the art which comprises a tubular valve body slidably disposed within a shell, an annular, first valve seat formed around the inner peripheral surface of the valve body, a valve plunger slidably fitted inside the valve body, an annular, second valve seat formed on the valve plunger, a valve element which is urged by a spring disposed within the valve body so as to be seated upon either the first or the second valve seat, a constant pressure passage providing a communication between a portion which is located radially outward of a first seat defined by the contact between the first valve seat and the valve element and a constant pressure chamber which is partitioned within the shell, a pressure passage for providing a communication between a portion which is located radially inward of a second seat defined by the contact between the second valve seat and the valve element and a source of pressure fluid, and a variable pressure passage for providing a communication between a portion located intermediate the first and the second seat and a variable pressure chamber which is also partitioned within the shell.

In the inoperative condition of the booster described above, the valve plunger is retracted to cause the valve element to be seated upon the second valve seat and to be spaced from the first valve seat. Under this condition, the second seat defined by the contact between the second valve seat and the valve element is closed to thereby close the pressure passage which communicates with the internal portion thereof while the first seat defined by the contact between the first valve seat and the valve element is opened to allow a communication between the constant pressure passage, located outside the first seat, and the variable pressure passage, located inside the first seat. In this manner, the constant pressure chamber communicating with the constant pressure passage and the variable pressure chamber communicating with the variable pressure passage assume an equal pressure, whereby the booster is inoperative.

By contrast, when the booster is operated, the depression of a pedal causes the valve plunger to be advanced, whereupon the valve element is seated upon the first valve seat to close the first seat, thus interrupting a communication between the constant and the variable pressure chamber. A continued advancement of the valve plunger causes the valve element to be removed from the second valve seat to open the second seat, whereupon the pressure passage, located inside the second seat, communicates with the variable pressure passage, located outside the second seat, allowing pressure fluid to be introduced into the variable pressure chamber to create a pressure differential between the constant and the variable pressure chamber to operate the booster.

When the booster is operated, that is, when pressure fluid is introduced into the variable pressure chamber through the pressure passage, sounds may be acoustically generated. To accommodate for this, it has been a practice to provide an acoustic absorbing material adjacent the inlet of the pressure passage to present a resistance to the passage of pressure fluid therethrough in an attempt to reduce the rate at which the pressure fluid is introduced into the variable pressure chamber in order to suppress the generation of sounds. However, such muffler suffers from a disadvantage that the response of the booster is degraded inasmuch as the provision of the acoustic absorbing material within the pressure passage presents a resistance to the passage of pressure fluid therethrough.

According to the present invention, a booster is provided comprising a tubular valve body slidably disposed within a shell, an annular, first valve seat formed on the inner peripheral surface of the valve body, a valve plunger slidable within the valve body having an annular, second valve seat, a valve element arranged to contact the first or the second valve seat to form a first or a second seal therewith respectively, a constant pressure passage for providing communication between a region located radially outward of said first seal and a constant pressure chamber within the shell, a further passage for communication between a region located radially inward of said second seal and a source of pressure fluid, and a variable pressure passage for providing communication between a region intermediate the first and the second seals and a variable pressure chamber within the shell, at least one wall region of the variable pressure passage being provided with projections and/or depressions to form an uneven surface.

The provision of the uneven surface on said at least one wall region of the variable pressure passage can reduce the generation of noise during the suction stroke as compared with a conventional arrangement. The uneven surface need not present any resistance to the passage of pressure fluid through the pressure passage as compared with an arrangement having an acoustic absorbing material disposed therein, so it need not have any compromising effect upon the response.

Further features and advantages of the invention will become apparent from the following description with reference to the accompanying drawings. In the drawings: Fig. 1 is a longitudinal section of a brake booster; Fig. 2 is a cross section of part shown in Fig. 1 to an enlarged scale; Fig. 3 is an enlarged cross section of part shown in Fig. 2; Fig. 4 is a graphical illustration of comparison between the present invention and a conventional arrangement in the generation of acoustic sounds during the suction stroke, as measured in terms of sound pressure level; Fig. 5 is a cross section illustrating a second embodiment of the invention; Fig. 6 is a cross section illustrating a third embodiment of the invention; Fig. 7 is a cross section illustrating a fourth embodiment of the invention; Fig. 8 is a cross section illustrating a fifth embodiment of the invention; and Fig. 9 is a cross section of a sixth embodiment of the invention.

Referring to the drawings, several embodiments of the invention will be described. Initially referring to Fig. 1, which shows a brake booster, this comprises an enclosed vessel consisting of a front shell 1 and a rear shell 2, and a center plate 3 which is disposed centrally therein to partition the interior into a front chamber 4 and a rear chamber 5. A substantially tubular valve body 6 slidably extends through axial portions of the rear shell 2 and the center plate 3 and are hermetically sealed by annular seal members 7 and 8, respectively, thereagainst.

A front power piston 9 and a rear power piston 10, which are disposed within the front chamber 4 and the rear chamber 5, respectively, are connected to the valve body 6, and a front diaphragm 11 and a rear diaphragm 12 are applied to the back surfaces of the power pistons 9 and 10, respectively, thus defining a constant pressure chamber A and a variable pressure chamber B across the front diaphragm 11 and a constant pressure chamber C and a variable pressure chamber D across the rear diaphragm 12.

A valve mechanism 13 which switches a fluid circuit between the pair of constant pressure chambers A, C and the pair of variable pressure chambers B, D is disposed within the valve body 6. Specifically, the valve mechanism 13 comprises an annular, first valve seat 14 formed around the inner peripheral surface of the valve body 6, an annular, second valve seat 16 which is disposed radially inward of the first valve seat 14 and formed on the right end of a valve plunger 15 which is slidably disposed within the valve body 6, and a valve element 18 which is urged from the right hand side, as viewed in Fig. 1, by a spring 17 so as to be seated upon either valve seat 14 or 16.

A space located radially outward of a first annular seat defined by the contact between the first valve seat 14 and the valve element 18 communicates with the constant pressure chambers A and C through axial constant pressure passages 19 and 19' which are formed in the valve body 6, and the constant pressure chamber A communicates with an intake manifold of an engine through a tubing 20 which introduces a negative pressure.

A space located radially inward of the first annular seat defined by the contact between the first valve seat 14 and the valve element 18, but located radially outward of a second annular seat defined by the contact between the second valve seat 16 and the valve element 18, or the space located intermediate the first and the second seat communicates with the variable pressure chamber D through a variable pressure passage 21 formed in the valve body 6. The variable pressure chamber D in turn communicates with the variable pressure chamber.B through an axial varaible pressure passage 22 also formed in the valve body 6.

Finally, a space located radially inward of the second or inner seat defined by the contact between the second valve seat 16 and the valve element 18 communicates with the atmosphere, serving as a source of pressure fluid, through a pressure passage 23 in which a filter 24 is disposed.

The right end of the valve plunger 15 is pivotally connected with the end of an input shaft 25, the other end of which is connected to a brake pedal, not shown.

On the other hand, a plunger plate 26 and a reaction disc 27 are sequentially disposed to the left of the valve plunger 15, and the reaction disc 27 is fitted in the right end of a push rod 28.

The left end of the push rod 28 slidably extends through the axial portion of the front shell 1, with a seal member 29 disposed therebetween, to the outside of the shell for connection with a piston of a master cylinder, not shown. The valve body 6 is normally maintained in its inoperative position shown by a return spring 30.

The valve body 6 includes a tubular terminal end 6a which projects through an opening in the rear shell 2 in the axially rearward direction, and is covered by a dust cover 31 formed of rubber at a location outside the opening.

The described arrangement is identical to a known arrangement of a conventional booster.

As shown to an enlarged scale in Fig. 2, the second valve seat 16 is formed into a spherical surface, upon which an annular bulge 18a which is formed around the inner periphery of the valve element 18 is adapted to be seated. Accordingly, the contact between the second valve seat 16 and the annular bulge 18a of the valve element 18 defines a second seat S2, and in relation to the second seat S2, to the radially inner side thereof lies the pressure passage 23 while to the radially outer side lies the variable pressure passage 21.

On the other hand, a first seat S1 is annularly defined by the contact between the first valve seat 14 and the valve element 18, and in relation to the first seat S1, to the radially outer side thereof lies the constant pressure passage 19 while to the radially inner side lies the variable pressure passage 21. It will be seen that the variable pressure passage 21 extends forwardly from a location intermediate the first seat S1 and the second seat S2, and is defined by an inner surface 6b of the valve body 6 which extends axially forward from the first valve seat 14 and which is circular in section, and an inner surface 6c of the valve body 6 which extends radially outward and which is square-shaped in section.

A covering 35 of synthetic resin is fitted over the inner surface 6b of the valve body 6 and is integrally secured thereto, while a covering 36 of synthetic resin is fitted over the inner surface 6c of the valve body 6 and is integrally secured thereto.

These coverings 35, 36 are tubular in configuration and are circular or square-shaped in section in accordance with the configuration of the inner surfaces 6b and 6c.

As indicated in Fig. 3, the inner surface of each covering 35 or 36 is formed with a multitude of annular grooves 35a therein to provide an uneven surface.

In the embodiment shown, the annular grooves 35a extend in a direction orthogonal to the direction in which the fluid flow passes, but may be formed to extend in a direction parallel to the direction of the passage of the fluid flow or at an angle thereto. Alternatively, it may be formed in grid-like configuration or the uneven surface may be irregularly shaped or formed at random.

In operation, when a brake pedal, not shown, is depressed to cause the input shaft 25 and its connected valve plunger 15 to advance in an integral manner, the valve element 18 also advances integrally while being seated upon the second valve seat 16 until the valve element 18 is seated upon the first valve seat 14 on the valve body 6 to interrupt the communication between the variable pressure passages 21 and 22 and the constant pressure passages 19 and 19'.

With continued advancement of the input shaft 25 and the valve plunger 15, the valve element 18, which is now seated upon the first valve seat 14 and is prevented from advancing further forward, is removed from the second valve seat 16, whereupon pressure fluid is introduced from the pressure passage 23 into the variable pressure chambers B and D through the constant pressure passages 21 and 22.

At this time, the provision of the coverings 35,36 over the inner surfaces 6b,6c of the variable pressure passage 21 formed in the valve body 6 and having the inner surfaces which are formed as uneven surfaces is effective to reduce the generation of sounds as the pressure fluid passes through such region.

Fig. 4 illustrates graphically the results of experiments conducted upon a booster constructed according to this embodiment of the invention and upon a conventional booster having smooth inner surfaces 6b,6c without the coverings 35,36, to measure the actual generation of sounds. Measured values obtained from the booster according to the invention are indicated by squares, which are joined by a two-dot phantom line. Measured values obtained from the conventional booster are indicated by circles, which are joined together by a solid line.

In Fig. 4, it will be noted that when the rate of pressure rise is equal to 50 kgf/cm2/sec, the sound pressure level produced from the booster of the present embodiment is equal to 52.7 dB while the sound pressure level from the conventional booster is equal to 53.0 dB.

When the rate of pressure rise increases to 100 kgf/cm2/sec, the sound pressure level of the booster of the present embodiment rises to 55.4 dB, while the sound pressure level of the conventional booster rises to 59.2 dB. At higher rates of pressure rise of 200 and 300 kgf/cm2/sec, respectively, the sound pressure level in the booster of the invention are 59.7 and 62.0 dB, respectively, while the sound pressure level of the conventional booster is equal to 64.5 and 65.8 dB, respectively. It will be seen from the described results of the experiments that in each case the sound pressure level of the described booster is lower than that of the conventional booster. Since no acoustic absorbing material is disposed within the pressure passage, the response remains unchanged from a booster having a conventional construction, thus without degradation in the response.

Second Embodiment Fig. 5 shows another embodiment of the invention.

In this embodiment, a valve body 106 is formed with a variable pressure passage 121 having inner surfaces 106b,106c in which a plurality of steps are formed, thereby providing uneven surfaces. The plurality of steps are formed in the valve body 6 by utilizing a corresponding draw mold, not shown, during the injection molding of the valve body 6 from synthetic resin to allow the mold to be withdrawn from the valve body. The internal diameters of the steps are sequentially increased in the drawing direction to permit the mold to be withdrawn from the valve body 106. In Fig. 5, numeral 114 represents a first valve seat, 115 a valve plunger, 116 a second valve seat, 118 a valve element, 119 a constant pressure passage, 123 a pressure passage, and 125 an input shaft.

Third Embodiment As shown in Fig. 6, the outer periphery of the draw mold may be formed with a plurality of grooves in the draw direction, thereby forming a plurality of ribs 206d on an inner surface 206b of a variable pressure passage 221 formed in a valve body 206 so as to extend axially of the valve body 6 and at an equal spacing around the circumference of the inner surface 206d, thus presenting an uneven surface.

Other Embodiments Furthermore, as shown in Fig. 7, an uneven surface may be provided by cutting at least one spiral groove or a plurality of annular grooves 306d directly in an inner surface 306b of a variable pressure passage 321 formed in a valve body 306. Alternatively, an uneven surface may be prow ded on an inner surface 406b of a variable pressure passage 421 formed in a valve body 406 by spraying synthetic resin 406d or the like, as shown in Fig. 8. Additionally, a coiled spring or a plurality of rings 506d may be placed as a pressure fit in an inner surface 506b of a variable pressure passage 521 formed in a valve body 506 to provide an uneven surface, as illustrated in Fig. 9.

In each instance, an uneven surface formed in this manner in the inner surface of the variable pressure passage functions a substantially similar effect as described above in connection with the first embodiment.

While an uneven surface has been described as being formed over the entire inner surface of the variable pressure passage in the described embodiments, such uneven surface may be formed only part of the inner surface of the variable pressure passage, for example, on only one of the inner surfaces 6b and 6c, depending on the muffling effect demanded.

While the invention has been illustrated and described above in connection with several embodiments thereof, it should be understood that a number of changes, modifications and substitutions therein will readily occur to one skilled in the art without departing from the scope of the invention defined by the appended claims. Reference can also be made to our copending application No. 9502267.9 (GB 2286864) from which the present application has been divided.

Claims

1. A booster comprising a tubular valve body slidably disposed within a shell, an annular, first valve seat formed on the inner peripheral surface of the valve body, a valve plunger slidable within the valve body having an annular, second valve seat, a valve element arranged to contact the first or the second valve seat to form a first or a second seal therewith respectively, a constant pressure passage for providing communication between a region located radially outward of said first seal and a constant pressure chamber within the shell, a further passage for communication between a region located radially inward of said second seal and a source of pressure fluid, and a variable pressure passage for providing communication between a region intermediate the first and the second seals and a variable pressure chamber within the shell, at least one wall region of the variable pressure passage being provided with projections and/or depressions to form an uneven surface.

2. A booster according to claim 1 in which said uneven surface is formed by a covering member or members secured to the valve body.

3. A booster according to claim 1 or claim 2 in which said uneven surface comprises a plurality of annular grooves.

4. A booster according to claim 1 or claim 2 in which said uneven surface comprises at least one spiral groove.

5. A booster according to claim 1 or claim 2 in which said uneven surface comprises annular depressions or projections forming a plurality of steps having diameters which increase progressively in the direction of fluid flow towards the variable pressure chamber.

6. A booster according to claim 1 or claim 2 in which said uneven surface is formed by a plurality of axially extending ribs and gaps between adjacent ribs.

7. A booster according to claim 1 or claim 2 in which said uneven surface is formed by a deposit of synthetic resin on an axially extending wall region, to produce the uneven surface thereon.

8. A booster according to claim 1 or claim 2 in which a plurality of spaced rings or a coiled spring is disposed along an axially extending wall region to form therewith said uneven surface.

9. A booster constructed and arranged for use and operation substantially as described herein with reference to any of the embodiments illustrated in the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS 1. A booster comprising a substantially tubular valve body slidably disposed within a shell, an annular, first valve seat formed on the inner peripheral surface of the valve body, a valve plunger slidable within the valve body having an annular, second valve seat, a valve element arranged to contact the first or the second valve seat to form a first or a second seal therewith respectively, a constant pressure passage for providing communication between a region located radially outward of said first seal and a constant pressure chamber within the shell, a further passage for communication between a region located radially inward of said second seal and a source of pressure fluid, and a variable pressure passage for providing communication between a region intermediate the first and the second seals and a variable pressure chamber within the shell, at least one wall region of the variable pressure passage being formed by the valve body and said wall region being provided with projections and/or depressions radially outwardly of the plunger to form an uneven surface for reducing noise in operation.

5. A booster according to claim 1 in which said uneven surface comprises a plurality of steps.

6. A booster according to claim 5 in which a radially inner wall of the variable pressure passage has a plurality of annular steps having diameters which decrease progressively in the direction of fluid flow towards the variable pressure chamber.

7. A booster according to claim 1 or claim 2 in which said uneven surface is formed by a plurality of axially extending ribs and gaps between adjacent ribs.

8. A booster according to claim 1 in which said uneven surface is formed by a deposit of synthetic resin on an axially extending wall region, to produce the uneven surface thereon.

9. A booster according to claim 1 in which a plurality of spaced rings or a coiled spring is disposed as a pressure fit along an axially extending wall region to form therewith said uneven surface.

10. A booster constructed and arranged for use and operation substantially as described herein with reference to any of the embodiments illustrated in the accompanying drawings.