JP3153282B2 - Anti-vibration device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid filled type vibration damping device used for vehicles, general industrial machines and the like, which absorbs and attenuates vibration from a vibration generating portion.

[0002]

2. Description of the Related Art In an automobile engine, an anti-vibration device as an engine mount is disposed between the engine and a vehicle body.
The vibration of the engine is prevented from being transmitted to the vehicle body. The vibration generated in the engine includes so-called shake vibration generated when the vehicle is running at high speed, and so-called idle vibration generated when the vehicle is idling and when the vehicle is running at about 5 km / h. The frequency is different between the shake vibration and the idle vibration.

A control engine mount has been proposed in which a plurality of restriction passages having different sizes are provided to absorb such vibrations having different frequencies, and the restriction passage corresponding to a desired frequency is switched by an on-off valve. ing. However, this vibration isolator has many components of the on-off valve, and has a disadvantage that the structure is complicated due to problems such as sealing.

As an anti-vibration device which solves the above-mentioned disadvantage, a diaphragm is brought into close contact with a wall surface of an air chamber by utilizing a negative pressure generated in an intake manifold of an engine, and has the same effect as switching a restriction passage. Has been proposed.

In this vibration isolator, a solenoid valve is provided between the intake manifold and the air chamber, and a restriction passage that does not want liquid to flow back and forth is switched by switching the restriction passage solenoid valve to connect the intake manifold to the intake manifold. The diaphragm is fixed by making the air chamber communicate with the air chamber and making the air chamber a negative pressure. When the liquid flows back and forth in the restricted passage, the solenoid valve is switched to communicate the air chamber with the outside air. As a result, the auxiliary liquid chamber can be expanded and contracted, and when the diaphragm is moved by the vibration, the air moves between the air chamber and the outside air through a solenoid valve and a pipe such as a rubber hose connecting the solenoid valve and the air chamber.

[0006]

However, the solenoid valve has a small diameter of the internal passage and the diameter of the valve hole, and has a high air passage resistance. In addition, air is not generated even in piping such as a rubber hose connecting the solenoid valve and the air chamber. Subject to passage resistance. Therefore, in particular,
At the time of vibration having a high frequency, the air passage is clogged and the diaphragm cannot move freely. For this reason, there is a problem that the liquid column hardly resonates with the liquid column in the restricted passage, and it is not possible to secure the vibration isolation characteristics.

The present invention has been made in view of the above circumstances, and has as its object to provide an anti-vibration device capable of securing anti-vibration characteristics and reliably damping and absorbing vibrations over a wide frequency range.

[0008]

According to a first aspect of the present invention, there is provided an anti-vibration device, wherein a first mounting member is connected to one of a vibration generating section and a vibration receiving section, and is connected to the other of the vibration generating section and the vibration receiving section. A second mounting member, an elastic body provided between the first mounting member and the second mounting member, which is deformed when vibration occurs, and a pressure receiving member capable of expanding and contracting the elastic body as a part of a partition wall. A liquid chamber, a plurality of sub-liquid chambers isolated from the pressure-receiving liquid chamber, a restriction passage communicating the pressure-receiving liquid chamber with the sub-liquid chamber, a diaphragm constituting a partition of the sub-liquid chamber, and the diaphragm Substantially hemispherical to stop the movement of the diaphragm
A pressing member, and driving means for moving the pressing member toward and away from the diaphragm , wherein the pressing member is
When contacting the diaphragm, the diaphragm is
An anti-vibration device characterized by not contacting an opening of a restriction passage .

According to a second aspect of the present invention, there is provided the vibration isolator according to the first aspect, further comprising a contact member that is in contact with the diaphragm on a side of the diaphragm opposite to a pressing member side. I have.

[0010]

According to the vibration damping device of the first aspect, for example, when the first mounting member is connected to the vibration source and the second mounting member is connected to the vibration receiving portion, the vibration is transmitted to the first mounting member. Elastic body,
It is supported by the vibration receiving portion via the second mounting member. At this time, the vibration is absorbed not only by the resistance based on the internal friction of the elastic body but also by the passage resistance of the liquid flowing through the restriction passage or the liquid column resonance.

When absorbing the vibration of the desired frequency, the driving means is operated to move the diaphragm of the sub-liquid chamber other than the sub-liquid chamber connected to the restriction passage absorbing the vibration of the desired frequency. The pressing member is pressed. As a result, the diaphragm is fixed in close contact with the pressing member, and the auxiliary liquid chamber to which the diaphragm is fixed cannot be expanded or contracted. For this reason, the liquid flows only through the restricted passage that absorbs vibration at the desired frequency,
The vibration at a predetermined frequency is reliably absorbed by the resistance and the liquid column resonance when the liquid passes.

In the vibration isolator according to the second aspect of the present invention, a contact member is provided on the opposite side of the diaphragm from the pressing member side, so that the diaphragm is pressed when the pressing member is pressed against the diaphragm. The diaphragm is clamped between the member and the close contact member, and the diaphragm is securely fixed.

[0013]

【Example】

First Embodiment A first embodiment of the vibration isolator 10 according to the present invention will be described with reference to FIGS.

As shown in FIG. 2, the vibration isolator 10 is provided with a mounting frame 12 for mounting to a vehicle body (not shown), and a first mounting member is mounted on an annular portion 14 of the mounting frame 12. Is inserted. A thin rubber layer 18 is vulcanized and bonded inside the outer cylinder 16. A part of the upper side of the thin rubber layer 18 is a large diaphragm 20 which is separated from the inner peripheral surface of the outer cylinder 16.
As shown in FIG. 3, a first air chamber 24 is provided between the outer cylinder 16 and the large diaphragm 20. Note that the first air chamber 24 may be communicated with the outside air as needed.

On the other hand, a part of the lower side of the thin rubber layer 18 is a small diaphragm 22 separated from the inner peripheral surface of the outer cylinder 16. The small diaphragm 22 is formed in a substantially hemispherical convex shape toward the inside of the outer cylinder 16. A large-diameter hole 17 is formed in the outer cylinder 16 corresponding to the small diaphragm 22, and the large-diameter hole 17 is closed by a boss 55 fixed to the outside of the annular member 14. A second air chamber 26 is provided between the small diaphragm 22 and the boss 55,
The air holes 55A provided in the boss 55 communicate with the outside air. The air hole 55A is set to a size that allows air to enter and exit the second air chamber 26 without resistance.

As shown in FIG. 2, an intermediate block 28 and an intermediate block 30 are inserted into the outer cylinder 16. The intermediate block 28 has flange portions 28 at both ends in the axial direction.
A is formed so that the outer peripheral surface is in close contact with the thin rubber layer 18, and an intermediate block 30 is fitted between the flange portions 28A. The intermediate block 30 has a substantially semicircular block shape when viewed from the axial direction of the outer cylinder 16, and has an outer peripheral surface in close contact with the thin rubber layer 18.

A notch 28B is formed in the intermediate block 28 at the center facing the intermediate block 30, and an inner cylinder 32 as a second mounting member extends therethrough. This inner cylinder 3
2 is arranged coaxially with the outer cylinder 16, and a main rubber 34 as an elastic body is stretched between the outer cylinder 16 and the intermediate block 28. This allows the inner cylinder 32 to move relative to the outer cylinder 16.

As shown in FIG. 1, a part of the outer peripheral surface of the main rubber 34 is in close contact with the top surface 30A of the intermediate block 30, and a part of the intermediate part is located between the intermediate block 30 and the pressure receiving liquid chamber. A notch portion 34A forming the first portion 36 is formed. Further, between the flange portions 28A of the intermediate block 28, the inner peripheral surface is formed by the intermediate block 28, and the outer peripheral surface is formed by the thin rubber layer 1.
8 and a first sub liquid chamber 38 defined by the large diaphragm 20.

As shown in FIGS. 2 and 3, a narrow groove 40 is formed on the outer periphery of the intermediate block 30 along the circumferential direction. One end of the narrow groove 40 is connected to the first auxiliary liquid chamber 38,
The other end is connected to the pressure receiving liquid chamber 36 through the opening 40A, and forms a first restriction passage 42 surrounded by the outer cylinder 16 and used for absorbing shake vibration. The intermediate block 30 has one end connected to the second auxiliary liquid chamber 44 and the other end formed in an opening 46 </ b> A formed in the inner peripheral portion of the intermediate block 30.
A second restriction passage 46 for absorbing idle vibration, the longitudinal section of which is connected to the pressure receiving liquid chamber 36 through the through hole, is formed. On the other hand, a cutout portion 30A is formed below the intermediate block 30, and the cutout portion 30A is surrounded by the thin rubber layer 18 and the small diaphragm 22 to form a second auxiliary liquid chamber 44. In the second sub liquid chamber 44,
An abutment plate 45 is provided as a substantially hemispherical contact member that protrudes toward the opposite side to the small diaphragm 22 side.
The contact plate 45 is separated from the small diaphragm 22 by a predetermined dimension, so that the contact plate 45 does not contact when the small diaphragm 22 vibrates. The contact plate 45 has a number of small holes 45B formed therein, and the liquid 48 in the second sub liquid chamber 44 is formed.
So that it does not hinder the distribution of

The pressure receiving liquid chamber 36, the first sub liquid chamber 38, the second sub liquid chamber 42, the first restriction passage 42 and the second restriction passage 46 are filled with a liquid 48 such as ethylene glycol. Have been.

A pressing member 50 is provided in the second air chamber 26.
Are arranged. In the pressing member 50, the small diaphragm 22 side is a substantially hemispherical contact surface 50A, and the opposite side is a flat surface portion 50B. The front end of a movable shaft 54 of a solenoid 52 as a driving means is fixed to the center of the flat portion 50B.
The solenoid 52 is attached to a boss 55. When a voltage is applied to a built-in electromagnetic coil (not shown), a movable iron core (not shown) is attracted by an exciting current and the movable shaft 5 is moved.
4 instantaneously moves to the electromagnetic coil side (not shown) (the direction of arrow U in FIG. 1). Further, when the voltage application to the electromagnetic coil is cut off, the movable shaft 54 instantaneously returns to the side opposite to the electromagnetic coil side by the biasing force of a built-in spring (not shown).

Therefore, when no voltage is applied to the electromagnetic coil of the solenoid 52, the movable shaft 54 moves toward the small diaphragm 22, as shown in FIG. Pressing member 5
The small diaphragm 22 is sandwiched between the contact plate 45 and the contact diaphragm 45. On the other hand, when the voltage application is cut off, the movable shaft 54 moves in the direction away from the small diaphragm 22 and the pressing member 50 separates from the small diaphragm 22.

A control means 56 is connected to the solenoid 52, and the control means 56 controls the solenoid 5.
2 is controlled. Further, the control means 56 is driven by a vehicle power supply, receives the detection signals from at least the vehicle speed sensor 58 and the engine speed sensor 60, detects the vehicle speed and the engine speed, and determines whether the vehicle is idling or shaking. Can be.

Next, the operation of this embodiment will be described. When a vehicle equipped with the anti-vibration device 10 according to the present invention as an engine mute runs at, for example, 70 to 80 km / h, shake vibration (less than 15 Hz) occurs. The control means 56 determines whether or not a shake vibration has occurred based on the vehicle speed sensor 58 and the engine speed sensor 60. When the control means 56 determines that shake vibration is occurring, the control means 56
2 is energized. As a result, the pressing member 50 is instantly moved to the small diaphragm 22 side, and the small diaphragm 22 is moved.
And the small diaphragm 22 is sandwiched between the pressing member 50 and the contact plate 45 (see FIG. 4). For this reason,
The movement of the small diaphragm 22 is completely prevented, and the second sub-liquid chamber 44 cannot be expanded or contracted.
Stop flowing inside. Therefore, the liquid 48 moves between the pressure receiving liquid chamber 36 and the first sub liquid chamber 38 through the first restriction passage 42, and the resistance and the liquid column when the liquid 48 passes through the first restriction passage 42 Shake vibration is absorbed by resonance.

When the engine is idling or when the vehicle speed is 5 km / h or less, the idle vibration (20
４０40 Hz). The control means 56 determines whether or not idle vibration has occurred based on the vehicle speed sensor 58 and the engine speed sensor 60. When the control means 56 determines that idle vibration is occurring, the control means 56
2 is not energized. For this reason, the pressing member 50 instantaneously separates the small diaphragm 22 (see FIG. 1), and the second sub liquid chamber 4
4 can be scaled. In the idle vibration, the first restricting passage 42 is clogged, but the liquid 48 passes through the second restricting passage 46, moves back and forth between the pressure receiving liquid chamber 36 and the second auxiliary liquid chamber 44, and passes through the second restricting passage. The liquid column resonates in 46. As a result, the dynamic spring constant of the vibration isolator 10 decreases, and idle vibration is absorbed. At this time, the air in the second air chamber 26
The air flows back and forth with the expansion and contraction of the sub-liquid chamber 44, but does not involve an electromagnetic valve or a pipe unlike the conventional vibration isolator.
Can move freely without hindering the movement, and can reliably lower the dynamic spring constant. Further, the vibration isolator 10 of the present invention has a configuration in which the pressing member 50 is moved by the solenoid 52 when the diaphragm is fixed, so that compared with a conventional vibration isolator configured to fix the diaphragm by negative pressure of air. Fast switching of anti-vibration characteristics,
Operation is assured.

[Second Embodiment] An anti-vibration device 10 according to the present invention.
A second embodiment of the present invention will be described with reference to FIGS. The same components as those of the first embodiment are denoted by the same reference numerals,
The description is omitted.

As shown in FIG. 5, the vibration isolator 10 is provided with a bottom plate 112 as a first mounting member. The bottom plate 112 has a mounting bolt 114 protruding from the lower center thereof, and is fixed to a vehicle body (not shown) as an example.

The periphery of the bottom plate 112 is a cylindrical upright wall portion 112A bent at a right angle, and a right angle bent flange portion 112B is continuously formed at the upper end of the upright wall portion 112A.

The lower end of an outer cylinder 116 fixed to the bottom plate 112 is caulked and fixed to the flange 112B. The periphery of the large diaphragm 118 is sandwiched between the flange 112B and the lower end of the outer cylinder 116. An air chamber 120 is provided between the large diaphragm 118 and the bottom plate 112, and communicates with the outside as needed.

The upper end of the outer cylinder 116 is an enlarged portion 116B whose inner diameter is enlarged, and the outer periphery of the main rubber 122 is vulcanized and bonded. A support base 124 as a second mounting member is vulcanized and bonded to the central top of the main rubber 122. In addition, a part of the main rubber 122 is extended to a part of the cylindrical part 116C of the outer cylinder 116 and a part of the lower end, and is vulcanized and bonded. The support base 124 is a mounting portion of an engine (not shown), and has mounting bolts 126 for fixing the engine.

Here, the inner peripheral portion of the outer cylinder 116, the main rubber 12
2 and the large diaphragm 118, the liquid chamber 12
The liquid chamber 128 is filled with a liquid 129 such as ethylene glycol.

Further, a restriction passage constituting member 130 is disposed in the liquid chamber 128, and the liquid chamber 128 is
2 and a first sub liquid chamber 134. The restricting passage constituting member 130 is formed in a substantially hat shape in cross section by a synthetic resin or the like, and a peripheral edge of a lower end is sandwiched between a lower end of the outer cylinder 116 and the large diaphragm 118.

As shown in FIGS. 5 and 6, a narrow groove 144 having a rectangular cross section is formed along the circumferential direction on the outer periphery of the restriction passage constituting member 130. The narrow groove 144 is
The 16th side is closed by an extension of the main rubber 122 to form a first restriction passage 152. The first restriction passage 152 has an opening 144 having a rectangular shape at one longitudinal end.
A communicates with the pressure receiving liquid chamber 132 via A, and the other end communicates with the first auxiliary liquid chamber 134 via the opening 144B.

Further, a rectangular hole 142 is formed in the restricted passage forming member 130 from the outer periphery to the outer periphery on the opposite side. The rectangular hole 142 has a distal end communicating with the pressure receiving liquid chamber 132 through the opening 142A to form a second restriction passage 146.

A boss 160 is fixed to the outer periphery of the cylindrical portion 116C of the outer cylinder 116 corresponding to the rectangular hole 142. The boss 160 has a substantially hemispherical concave portion 162 formed on the side opposite to the cylindrical portion 116C side.
2 is closed by the holding plate 164. The boss 160 has an annular recess 166 outside the opening of the recess 162.
Are formed coaxially, and a peripheral portion of the small diaphragm 168 is sandwiched between the annular concave portion 166 and the pressing plate 164.

A hole 162A is formed at the center of the concave portion 162, and the hole 162A communicates with the rectangular hole 142 through a through hole 172 penetrating the outer cylinder 116. The space from the through hole 172 to the small diaphragm 168 is a second sub-liquid chamber 170, and the small diaphragm 16
A second air chamber 174 is provided between the pressure plate 8 and the holding plate 164. The holding plate 164 is provided with an air hole 164A, and the second air chamber 174 is communicated with the outside air by the air hole 55A.

In the second air chamber 174, a pressing member 50 is provided as in the first embodiment. The solenoid 52 is attached to the outer surface of the holding plate 164, and the movable shaft 54 of the solenoid 52 passes through the holding plate 164, and the tip is fixed to the center of the flat portion 50 </ b> B of the pressing member 50.

Next, the operation of the second embodiment will be described. In the vibration isolator 10 of the present embodiment, the bottom plate 112 is fixed to a vehicle body (not shown) via mounting bolts 114, and the engine is mounted on a support 124 and fixed by mounting bolts 126.

When the vibration is a shake vibration (less than 15 Hz), the control means 56 does not energize the solenoid 52 as in the first embodiment. Therefore, as shown by the imaginary line in FIG. 5, the pressing member 50 comes into close contact with the small diaphragm 168,
The second sub liquid chamber 170 cannot be expanded or contracted, and the second restriction passage 1
There is no flow of liquid 129 in 46. As a result, the liquid 129 moves back and forth between the pressure receiving liquid chamber 232 and the first sub liquid chamber 134 through the first restriction passage 152, and
Is shaken by the resistance and the liquid column resonance when the liquid crystal passes through the first restriction passage 152.

When the vibration is idle vibration, the control means 56 energizes the solenoid 52. As a result, as shown by the solid line in FIG. 5, the pressing member 50 is separated from the small diaphragm 168 to be in a free state, and the second auxiliary liquid chamber 170 can be expanded and contracted. As a result, the liquid 129 passes through the second restriction passage 146 and is
The fluid flows back and forth between the sub liquid chamber 170 and the liquid column resonates in the second restriction passage 142, whereby the dynamic spring constant is reduced and the idle vibration is absorbed.

In the vibration isolator 10 of the second embodiment, as in the case of the vibration isolator 10 of the first embodiment, when the second auxiliary liquid chamber 170 expands and contracts, the air in the second air chamber 174 resists. Since the small diaphragm 168 can move in and out freely without movement, the small diaphragm 168 can move freely without hindering movement. Therefore, the dynamic spring constant can be reliably reduced for idle vibration.

[Third Embodiment] An anti-vibration device 10 according to the present invention.
The third embodiment will be described with reference to FIG. The third
The embodiment is a modification of the second embodiment, and the same components as those of the second embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 7, in this embodiment, an iron plate 202 is fixed to the center of the small diaphragm 168. An electromagnet 200 is attached to the holding plate 164 instead of the solenoid 52. The tip 200A of the electromagnet 200 is separated from the iron plate 202 by a predetermined dimension so as not to contact when the small diaphragm 168 vibrates. The electromagnet 200 is connected to the control means 56. When the electromagnet 200 is energized, the electromagnet 200 attracts the iron plate 202. The inner surface of the holding plate 164 is formed in a trumpet shape so as to be in close contact when the small diaphragm 168 is sucked.

When the vibration is a shake vibration (less than 15 Hz), the control means 56 energizes the electromagnet 200. As a result, the iron plate 202 is attracted to the electromagnet 200 and the small diaphragm 168 comes into close contact with the inner surface of the holding plate 164, so that the second sub-liquid chamber 170 cannot be expanded or contracted, and the flow of the liquid 129 in the second restriction passage 146 is reduced. Disappears. As a result, the liquid 129 moves back and forth between the pressure receiving liquid chamber 232 and the first sub liquid chamber 134 through the first restriction passage 152, and
Is shaken by the resistance and the liquid column resonance when the liquid crystal passes through the first restriction passage 152.

When the vibration is idle vibration, the control means 56 does not energize the electromagnet 200. Thereby, the suction of the iron plate 202 is released, and the small diaphragm 16 is released.
8, the second sub liquid chamber 170 can be expanded and contracted. As a result, the liquid 129 passes through the second restriction passage 146.
Through the pressure receiving liquid chamber 132 and the second sub liquid chamber 170, the liquid column resonates in the second restriction passage 142, the dynamic spring constant decreases, and the idle vibration is absorbed.

In the vibration isolator 10 of this embodiment, similarly to the vibration isolator 10 of the previous embodiment, when the second sub liquid chamber 170 expands and contracts, the air in the second air chamber 174 is free without any resistance. Since the small diaphragm 168 can move in and out, it can move freely without hindering the movement. Therefore, the dynamic spring constant can be reliably reduced for idle vibration.

In the first and second embodiments, the pressing member 5
Although the solenoid is used as the means for moving 0, the present invention is not limited to this, and another driving means such as a motor may be used.

Further, in the embodiments, the vibration damping device as the engine mount is shown, but the present invention is not limited to this, and it is needless to say that the present invention may be applied to a cabinet mount, a body mount and the like.

Further, in each of the above embodiments, the second air chamber is configured to communicate with the outside air through the air hole. However, the present invention is not limited to this, and the small diaphragm is on the side opposite to the second sub liquid chamber side. May be configured to directly face the outside air.

[0050]

As described above, the anti-vibration device of the present invention has the above-mentioned configuration, and therefore has an excellent effect that the anti-vibration characteristics can be secured and vibrations over a wide frequency range can be reliably attenuated and absorbed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a vibration isolator according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of the vibration isolator according to the first embodiment of the present invention.

FIG. 3 is a side view of a restriction passage constituting member according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a state in which a small diaphragm is in close contact with the vibration isolator according to the first embodiment of the present invention.

FIG. 5 is a sectional view taken along an axis of a vibration isolator according to a second embodiment of the present invention.

FIG. 6 is a sectional view taken along line 6-6 in FIG. 5, according to a second embodiment of the present invention;

FIG. 7 is a sectional view taken along an axis of a vibration isolator according to a third embodiment of the present invention.

[Description of Signs] 10 Vibration isolator 16 Outer cylinder (first attachment member) 20 Large diaphragm 22 Small diaphragm 24 Air chamber 26 Air chamber 32 Inner cylinder (second attachment member) 34 Body rubber (elastic body) 36 Pressure receiving Liquid chamber 38 First sub-liquid chamber 42 First restriction passage 44 Second sub-liquid chamber 45 Contact plate (contact member) 46 Second restriction passage 48 Liquid 50 Pressing member 52 Solenoid (drive means) 112 Bottom plate (First) 118 Large diaphragm 122 Main body rubber (elastic body) 124 Support base (second mounting member) 132 Pressure receiving liquid chamber 134 First sub liquid chamber 146 Second restricted passage 152 First restricted passage 168 Small diaphragm 170 Second sub liquid chamber 174 Second air chamber

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16F 13/26 B60K 5/12

Claims (2)

(57) [Claims] A first mounting member connected to one of the vibration generating unit and the vibration receiving unit; a second mounting member connected to the other of the vibration generating unit and the vibration receiving unit; and the first mounting An elastic body provided between the member and the second mounting member and deforming when vibration occurs, a pressure-receiving liquid chamber capable of expanding and contracting the elastic body as a part of a partition, and a plurality of pressure-receiving liquid chambers isolated from the pressure-receiving liquid chamber A sub-liquid chamber, a restriction passage communicating between the pressure-receiving liquid chamber and the sub-liquid chamber, a diaphragm constituting a partition of the sub-liquid chamber, and a substantially hemispherical shape which abuts on the diaphragm to prevent movement of the diaphragm. comprising of a pressing member, and a driving means for contacting and separating the pressing member relative to said diaphragm, said press
When the pressure member contacts the diaphragm, the diaphragm
The flam does not contact the opening of the restriction passage . 2. An anti-vibration device according to claim 1, wherein a contact member is provided on the opposite side of said diaphragm from said pressing member side to contact said diaphragm.