JPS6222661Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention is a brake booster in which a diaphragm that is displaced in response to a pressure difference is housed in a shell, and the shell is protruded from the inside of the shell in order to be attached to a predetermined location on the vehicle body. The present invention relates to a mounting structure for fixing bolts.

FIG. 1 shows an example of this type of brake vacuum booster, in which a diaphragm 3 is clamped between a front shell 1 and a rear shell 2, and inside the shell is this diaphragm 3 and a piston attached to it. 4 into a negative pressure chamber 5 and a variable pressure chamber 6. As is well known, this booster uses a valve mechanism to introduce atmospheric air into the variable pressure chamber 6 during a brake operation that displaces the input shaft 7, and a pressure difference is generated between the variable pressure chamber 6 and the negative pressure chamber 5. Accordingly, piston 4
A thrust force is applied to a push rod 8 supported thereon, and the operating force is transmitted via the push rod 8 to an adjacent master cylinder (not shown).

By the way, in order to fix this brake booster to the vehicle body side, as shown in the figure, a bolt insertion hole 10 is inserted into the master cylinder side mounting portion 9 of the front shell 1.
A fixing bolt 11 is inserted into the hole 10 from the inside of the front shell 1. Similarly, a bolt insertion hole 13 is provided in the attachment part 12 of the rear shell 2, and a fixing bolt 14 is inserted through the hole 10. There is.

Since these fixing bolts 11 and 14 are required to be tightly and tightly attached to each shell 1 and 2, conventionally, the fixing bolts 11 and 14 are shown in FIG.
As shown in an enlarged view, in the bolt insertion hole 10 provided in the front shell 1, the outer surface of the shell 1 is chamfered in a conical shape to form a dish-shaped portion 10a, and the fixing bolt 11 is provided with a conical chamfer. Base step part 1 in advance
1a is provided, and the stepped portion 11a is plastically deformed by caulking or the like to compensate for the inside of the dish-shaped portion 10a, and the fixing bolt 11 is tightly fixed to the front shell 1. Note that the fixing bolt 14 also relies on similar means.

In this way, in the above conventional means, the outer periphery of the bolt insertion hole 10 is chamfered to form the dish-shaped portion 1.
0a is formed and this is compensated for by plastic working, but in this method, if the shell plate thickness can be taken to a sufficient value as in the conventional method, the compensation space formed by the dish-shaped portion 10a can also be relatively large, Almost satisfactory results were obtained in plastic working. However, due to the recent demand for lighter weight devices, a shell plate with a thin shell plate thickness of about half that of a conventional one has been adopted, and the storage volume inside the dish-shaped portion 10a literally becomes thin and small. It is difficult to set the dimensions of the bolt side step portion 11a whose interior is to be compensated for by plastic deformation, and in normal cases, as a result of the plastic deformation, a bulge due to redundant material is generated at the periphery of the bolt base end. Ta. However, the outer mounting end surface 9a of the mounting portion 9 is required to have high smoothness so as to be in close contact with the mating mounting surface in order to maintain the mounting dimensional accuracy of the air chamber. However, this had the disadvantage of requiring extra processing means to grind and smooth it.

Furthermore, chamfering the bolt insertion hole 11 as described above leads to a reduction in strength at the periphery of the hole, which is one of the factors that prevents the realization of the above-mentioned request for thinner and lighter shells.

In view of the above points, the present invention makes it possible to use a thinner shell plate by using a reinforcing plate without causing the above-mentioned bulge on the shell mounting surface and without deteriorating the strength at the periphery of the bolt insertion hole. The purpose is to ensure airtightness, and a diaphragm that is displaced in response to a pressure difference is installed inside the shell, and a bolt insertion hole is drilled in the mounting part of the shell. and a brake booster in which a fixing bolt is made to protrude from inside the shell through the bolt insertion hole; is accommodated in a hole surrounding the bolt shaft of a reinforcing plate interposed between the fixing bolt head and the shell inner wall surface, and the bolt shaft is plastically deformed. It is characterized in that the inside of the annular step surrounding the section is filled.

The present invention will be explained below with reference to the illustrated embodiments.
In FIG. 3, the peripheral edge of a bolt insertion hole 21 bored in the shell 20 is bent inward to form an annular stepped portion 21a, and a fixing bolt 22 is passed through the bolt insertion hole 21 from inside the shell. There is.

The base end shaft portion 22a of this fixing bolt 22 is
is set to have approximately the same diameter as the inner diameter of the bolt insertion hole 21 and a larger diameter than the screw shaft portion 22b.
Therefore, an annular recess 23 is formed by the proximal shaft portion 22a and the annular step portion 21a, and within this recess 23 there is a shoulder excess portion 22c of the proximal shaft portion 22a, that is, the shoulder portion 22c of the proximal shaft portion 22a. The inside of the recessed portion is compensated for by plastically deforming the portion indicated by the broken line in FIG. 2 by caulking or the like. According to this configuration, the excess thickness of the bolt 22 deformed and transferred into the recess 23 is transferred to the outer circumferential surface of the shell 20, that is, the mounting end surface 20a.
The shape of the annular stepped portion 21a can be easily set to have a sufficiently large transition space so as to prevent further protrusion.

On the other hand, on the inner peripheral surface side of the shell 20, there is a washer-shaped reinforcing plate 24 that surrounds the annular step 21a and has a thickness that is approximately the same as the height of the step 21a.
The reinforcing plate 24 is clamped between the head 22d of the fixing bolt 22 and the shell 20. In other words, the stepped portion 21a is accommodated in an annular recess 22e formed between the hole of the reinforcing plate 24 and the base end shaft portion 22a. In addition, a plurality of conical anti-rotation protrusions 25 are provided on the contact surface of the bolt head 22d with the reinforcing plate 24, and when the fixing bolt 22 is attached to the shell 20, the protrusions 25
5 is press-fitted into the reinforcing plate 24 to prevent the bolt 22 from rotating. Note that the reinforcing plate 24 is not limited to a washer shape, but may be a donut shape that extends along the entire circumference of the shell 20 on the mounting surface side.

The device of this embodiment having the above-described configuration has an annular recess 23 formed in a bent manner, and an excess wall portion 22 of the bolt 22 attached to the annular recess 23.
c, the size and shape of the annular recess 23 can be freely set according to the purpose, use, etc. of the device. There is no fear that the shell will protrude from the shell mounting end surface 20a. Further, by providing the reinforcing plate 24, the strength performance near the bolt insertion hole 21 is improved, and it becomes possible to firmly tighten the fixing bolt 22 to the shell 20 and the mating material. In addition, since the bolt insertion hole 21 is not chamfered as in conventional bolt insertion holes, the strength of the periphery of the insertion hole is not reduced, and the thickness of the shell 20 itself can be reduced, which in turn reduces the weight of the device. can be achieved.

Note that the shape of the annular stepped portion 21a does not necessarily have to be a perfect annular shape, and the fixing bolt 22 may be prevented from rotating by forming irregularities on its periphery.

As described above, according to the present invention, the annular step formed in the shell in advance is housed in the hole of the reinforcing plate, and this annular step is compensated for by plastic deformation of the bolt shaft. The supplementary portion not only ensures the airtightness of the shell, but also completely eliminates the possibility that this portion will come loose during use.

In addition, unlike conventional bolts, the extra wall of the bolt that is transferred and formed by plastic deformation does not protrude from the shell mounting end surface, and the bolt insertion hole is not chamfered, and there is a gap between the bolt head and the shell. Since the reinforcing plate is interposed in the shell, the plate thickness of the shell itself can be made as thin as possible, which in turn makes it possible to reduce the weight of the entire brake booster.

[Brief explanation of the drawing]

Fig. 1 shows a conventional brake vacuum booster, a partially sectional side view, Fig. 2 is an enlarged sectional view showing the fixing bolt attachment part of Fig. FIG. 2 is a cross-sectional view showing an enlarged main part of one embodiment. 1, 2, 20... Ciel, 3... Diaphragm, 9, 12... Mounting part, 10, 13, 21...
Bolt insertion hole, 11, 14, 22... Fixing bolt, 21a... Annular step, 22d... Head, 22
e... annular depression, 23... annular recess.

Claims (1)

[Scope of utility model registration request] A brake booster in which a diaphragm that is displaced in response to a pressure difference is installed in a shell, a bolt insertion hole is bored in the mounting part of the shell, and a fixing bolt is made to protrude from inside the shell through the bolt insertion hole, The bolt of the reinforcing plate has a circumferential edge of the bolt insertion hole of the shell bent inward to form an annular step, and the annular step is interposed between the fixing bolt head and the inner wall surface of the shell. A brake booster which is housed in a hole surrounding a shaft portion, and is configured to plastically deform the shaft portion of the fixing bolt to compensate for the inside of the annular stepped portion surrounding the bolt shaft portion.