Patent Description:
There is a diaphragm pump configured to drive a diaphragm by converting the rotation of a motor into a reciprocating motion. To reduce a discharge flow rate in a diaphragm pump of this type, a method of reducing the rotation speed of a motor by lowering a voltage applied to the motor is often employed.

To suppress the discharge flow rate to a remarkably low flow rate by this method, the voltage applied to the motor needs to be considerably lowered. However, if the applied voltage is considerably lowered, the motor stops because of shortage of torque, or the rotation becomes unstable to make the pulsation of the pump motion large. It is therefore impossible to obtain a stable low flow rate. Hence, it is difficult to suppress the discharge flow rate to a considerably low flow rate, for example, <NUM>% of the rated flow rate.

The present inventor considered that the above-described problem can be solved to some extent by providing the diaphragm pump with a leak structure for intentionally leaking the pressure in a pump chamber. This is because even if the voltage applied to the motor is not considerably lowered to such a point that the motor stops due to shortage of torque, or the rotation becomes unstable, the discharge flow rate can be suppressed low because a fluid leaks from the leak structure.

For another purpose, a diaphragm pump with a leak structure is disclosed in <CIT> (literature <NUM>) and <CIT> (literature <NUM>). In literature <NUM>, a convex portion is provided on a base that holds a diaphragm. When the diaphragm is brought into tight contact with the base, a gap is formed at an end of the convex portion. A fluid partially leaks from this gap. In literature <NUM>, a convex portion is provided on the valve seat of a check valve. Even in a state in which the check valve is closed, a gap is formed around the convex portion, and a fluid slightly flows out from the gap.

However, in the leak structure disclosed in literature <NUM>, if a foreign substance is put in the gap between the diaphragm and the convex portion on the base, the foreign substance cannot be removed basically, and therefore, the discharge flow rate cannot be reduced. For this reason, performance may be unstable in the diaphragm pump with the leak structure.

In the leak structure disclosed in literature <NUM>, since the hardness of the valve seat is higher than the hardness of the check valve, the valve body of the check valve that repetitively comes into contact with the convex portion wears, and dust is generated. For this reason, durability performance is low in the diaphragm pump with the leak structure. Further, US Patent Application <CIT> discloses a diaphragm pump includes a fluid inlet, a fluid discharge port, and a fluid exhaust port that are open to outside of the diaphragm pump. <CIT> discloses a fluid pump having a chamber, a diaphragm cooperating with the chamber and actuated by a solenoid, and inlet and outlet check valves communicating with the chamber.

It is an object of the present invention to provide a diaphragm pump capable of suppressing a discharge flow rate to a remarkably low flow rate and improving performance stability and durability performance.

In order to achieve the above object of the present invention, there is provided a diaphragm pump (<NUM>) comprising a diaphragm (<NUM>) including a deformation portion (<NUM>) having a cup shape, a partition (<NUM>) configured to close an opening portion of the deformation portion (<NUM>) and form a pump chamber (<NUM>) together with the deformation portion (<NUM>), a suction through hole (<NUM>) extending through the partition (<NUM>), a suction passage (<NUM>) communicating with the pump chamber (<NUM>) via the suction through hole (<NUM>), a discharge through hole (<NUM>) extending through the partition (<NUM>), a discharge passage (<NUM>) communicating with the pump chamber (<NUM>) via the discharge through hole (<NUM>), a driving mechanism (<NUM>) configured to convert rotation of a motor (<NUM>) into a reciprocating motion and alternately deform the deformation portion (<NUM>) in a direction of increasing a capacity of the pump chamber (<NUM>) and in a direction of decreasing the capacity of the pump chamber (<NUM>), a suction valve (<NUM>) attached to the partition (<NUM>) and configured to open the suction passage (<NUM>) in a stroke of increasing the capacity of the pump chamber (<NUM>) and close the suction passage (<NUM>) in a stroke without increasing the capacity, and a discharge valve (<NUM>) attached to the partition (<NUM>) in the discharge passage (<NUM>) and configured to open the discharge passage (<NUM>) in a stroke of decreasing the capacity of the pump chamber (<NUM>) and close the discharge passage (<NUM>) in a stroke without decreasing the capacity, wherein the partition (<NUM>) includes a seat surface (<NUM>) on a side facing the pump chamber (<NUM>), and the suction valve (<NUM>) includes a valve body (31b) configured to come into contact with or separate from the seat surface (<NUM>), and the valve body (31b) includes a leak structure (<NUM>) configured to form a channel (<NUM>) between the valve body (31b) and the seat surface (<NUM>).

A diaphragm pump according to an embodiment of the present invention will now be described in detail with reference to <FIG>.

A diaphragm pump <NUM> shown in <FIG> is attached to a motor <NUM> located at the lowermost position in <FIG>, and is driven by the motor <NUM>. The diaphragm pump <NUM> according to this embodiment is a pump that sucks and discharges air.

The diaphragm pump <NUM> includes a housing <NUM> fixed to the motor <NUM>. Functional components that constitute the diaphragm pump <NUM> are held by the housing <NUM>. The housing <NUM> is formed into a columnar shape by combining a plurality of members in the axial direction of the motor <NUM> and located on the same axis as a rotation shaft <NUM> of the motor <NUM>.

The plurality of members that constitute the housing <NUM> include a bottom body <NUM>, a diaphragm holder <NUM>, a valve holder <NUM>, a lid body <NUM>, and the like. The bottom body <NUM> is a member that has a bottomed cylindrical shape and is attached to the motor <NUM>. The diaphragm holder <NUM> is attached to the opening portion of the bottom body <NUM>. The valve holder <NUM> is a disc-shaped member (partition) attached to the diaphragm holder <NUM> in a state in which a diaphragm <NUM> to be described later is sandwiched between the valve holder <NUM> and the diaphragm holder <NUM>. The lid body <NUM> is attached to the valve holder <NUM> while being overlaid on the valve holder <NUM>.

The diaphragm <NUM> is held while being sandwiched between the diaphragm holder <NUM> and the valve holder <NUM>. The diaphragm <NUM> includes a plurality of cup-shaped deformation portions <NUM> opening to the valve holder <NUM>. The deformation portion <NUM> is arranged in each of a plurality of regions formed by dividing the diaphragm <NUM> in the circumferential direction of the housing <NUM>. The opening portion of the deformation portion <NUM> is closed by the valve holder <NUM>, and a pump chamber <NUM> is formed between the deformation portion <NUM> and the valve holder <NUM>. That is, the valve holder <NUM> forms the pump <NUM> together with the deformation portion <NUM>. A connecting piece <NUM> projecting in a direction opposite to the pump chamber <NUM> is provided on a bottom wall 11a of the deformation portion <NUM> having a cup shape. A driving mechanism <NUM> is connected to the connecting piece <NUM>.

The driving mechanism <NUM> includes a crank body <NUM> attached to the rotation shaft <NUM> of the motor <NUM>, a driving body <NUM> connected to the crank body <NUM> via a driving shaft <NUM>, and the like. The crank body <NUM> is fixed to the rotation shaft <NUM>, and rotates integrally with the rotation shaft <NUM>. The driving shaft <NUM> is fixed to an eccentric portion of the crank body <NUM> while tilting with respect to the rotation shaft <NUM> of the motor <NUM>. The tilting direction of the driving shaft <NUM> is a direction in which the eccentric amount to the rotation shaft <NUM> becomes small at the distal end portion of the driving shaft <NUM>.

The driving body <NUM> includes a columnar shaft portion <NUM> connected to the driving shaft <NUM>, and a plurality of arm portions <NUM> projecting from the shaft portion <NUM> outward in the radial direction. The arm portion <NUM> is provided for each deformation portion <NUM> of the diaphragm <NUM>, and extends radially from the shaft portion <NUM> outward in the radial direction. A through hole 26a is formed in the arm portion <NUM>. The connecting piece <NUM> of the diaphragm <NUM> is engaged in the through hole 26a. The connecting piece <NUM> extends through the arm portion <NUM> and is fixed to the arm portion <NUM> in this state. Hence, the arm portion <NUM> is connected to each of the plurality of deformation portions <NUM> of the diaphragm <NUM>.

According to the driving mechanism <NUM>, when the rotation shaft <NUM> of the motor <NUM> rotates, the crank body <NUM> and the driving shaft <NUM> rotate about the rotation shaft <NUM>. At this time, since the rotation of the driving body <NUM> is impeded by the diaphragm <NUM>, the driving body <NUM> swings along with a change of the tilting direction of the driving shaft <NUM>. By this swing, the arm portion <NUM> pushes or pulls the deformation portion <NUM>. In this way, the driving body <NUM> converts the rotation of the rotation shaft <NUM> into a reciprocating motion and transmits it to the deformation portion <NUM>.

If the deformation portion <NUM> of the diaphragm <NUM> is pulled by the arm portion <NUM> to the side of the motor <NUM>, and the deformation portion <NUM> expands, the capacity of the pump chamber <NUM> increases. On the other hand, if the deformation portion <NUM> of the diaphragm <NUM> is pushed by the arm portion <NUM> to the side of the valve holder <NUM>, and the deformation portion <NUM> contracts, the capacity of the pump chamber <NUM> decreases. For this reason, when the crank body <NUM> continuously rotates, a state in which the capacity of the pump chamber <NUM> increases and a state in which the capacity decreases are alternately repeated.

A suction through hole <NUM> and a discharge through hole <NUM> are formed in a portion of the valve holder <NUM>, which forms the wall of the pump chamber <NUM>. A suction valve <NUM> is provided near the suction through hole <NUM>. The suction valve <NUM> is made of a rubber material and attached to the valve holder <NUM> for each pump chamber <NUM>. As shown in <FIG>, the suction valve <NUM> according to this embodiment includes a shaft portion 31a inserted into the shaft hole <NUM> formed in the valve holder <NUM> and fixed to the valve holder <NUM>, and a valve body 31b that comes into contact with or separates from a seat surface <NUM> of a valve seat formed on the valve holder <NUM>. The seat surface <NUM> is a smooth surface formed on a side of the valve holder <NUM> facing the pump chamber <NUM>.

The valve body 31b of the suction valve <NUM> is formed into an annular plate shape, as shown in <FIG>. As shown in <FIG>, the valve body 31b according to this embodiment is formed into a shape that is curved to gradually approach the seat surface <NUM> toward the outer edge.

Also, as shown in <FIG>, the valve body 31b includes a leak structure <NUM> configured to form a minute channel <NUM> between the valve body 31b and the seat surface <NUM>. The valve body 31b includes a seal surface <NUM> facing the seat surface <NUM>, and the leak structure <NUM> is constituted by an unevenness <NUM> formed by concave portions <NUM> and convex portions <NUM> provided all over the seal surface <NUM>. The seal surface <NUM> is formed in a range indicated by hatching in <FIG>. In <FIG>, the unevenness <NUM> is drawn by a wavy curved line to help understanding of the configuration of the leak structure <NUM>. However, an angled portion or a valley portion having a steep tilting surface may exist in the unevenness <NUM>.

Note that as long as the channel <NUM> from the suction through hole <NUM> into the pump chamber <NUM> is formed, the leak structure <NUM> formed by the unevenness <NUM> need not always be provided all over the seal surface <NUM>. For example, the leak structure <NUM> formed by the unevenness <NUM> may be provided only on the outer edge portion of the seal surface <NUM>, which comes into contact with the seat surface <NUM> when the suction valve <NUM> closes the suction through hole <NUM>.

The valve body 31b is molded using a mold <NUM> shown in <FIG>. The mold <NUM> includes a molding surface 42a for emboss processing. The unevenness <NUM> of the valve body 31b is an unevenness formed by transferring the shape of the molding surface 42a of the mold <NUM>. That is, the unevenness <NUM> is formed by performing emboss processing on the seal surface <NUM> when molding the valve body 31b using the mold <NUM> that molds the valve body 31b into a desired shape. The surface shape of the unevenness <NUM> formed by emboss processing is, for example, a leather pattern, a wood pattern, a rock grain pattern, a sand pattern, a satin pattern, or a geometric pattern.

As shown in <FIG>, the suction through hole <NUM> is a hole that extends through the valve holder <NUM> to communicate the pump chamber <NUM> with a suction passage <NUM> to be described later. The opening of the suction through hole <NUM> on the side of the pump chamber <NUM> is opened/closed by the valve body 31b of the suction valve <NUM>. When the valve body 31b separates from the opening, the suction passage <NUM> is opened. When the valve body 31b closes the opening, the suction passage <NUM> is closed. In a stroke of increasing the capacity of the pump chamber <NUM>, the valve body 31b separates from the opening. In remaining strokes, the valve body 31b closes the opening. That is, the suction valve <NUM> opens the suction passage <NUM> (or the suction through hole <NUM>) in the stroke of increasing the capacity of the pump chamber <NUM>, and closes the suction passage <NUM> (or the suction through hole <NUM>) in the remaining strokes. The remaining strokes are strokes without the increase of the capacity of the pump chamber <NUM>, and include a stroke of decreasing the capacity of the pump chamber <NUM>, and a stroke of maintaining the capacity.

The suction passage <NUM> is formed by a suction fluid chamber <NUM> to which the suction through hole <NUM> opens, a driving mechanism storing chamber <NUM> in the housing <NUM>, which is connected to the suction fluid chamber <NUM> via a communicating path (not shown), and an inlet passage <NUM> extending, from the driving mechanism storing chamber <NUM>, through the valve holder <NUM> and the lid body <NUM>. The suction fluid chamber <NUM> is formed between the valve holder <NUM> and the lid body <NUM>. The driving mechanism storing chamber <NUM> is a space in which the driving mechanism <NUM> is stored. The inlet passage <NUM> is formed by a through hole <NUM> formed in the valve holder <NUM>, and a through hole <NUM> including the hollow portion of a suction pipe <NUM> provided in the lid body <NUM>.

The discharge through hole <NUM> is a hole that extends through the valve holder <NUM> to communicate the pump chamber <NUM> with a discharge passage <NUM>. The discharge passage <NUM> is formed by a discharge fluid chamber <NUM> formed at the center between the valve holder <NUM> and the lid body <NUM>, and a discharge pipe <NUM> projecting at the axial portion of the lid body <NUM>.

In the discharge passage <NUM>, a discharge valve <NUM> is attached to the valve holder <NUM>. The discharge valve <NUM> has a so-called hat shape and is made of a rubber material. The discharge valve <NUM> includes a valve body <NUM> that has an annular plate shape and opens/closes the opening of the discharge through hole <NUM>, and is fitted on a projection <NUM> of the valve holder <NUM> and is fixed to the valve holder <NUM>.

The opening of the discharge through hole <NUM> on the side of the discharge fluid chamber <NUM> is opened/closed by the valve body <NUM> of the discharge valve <NUM>. When the valve body <NUM> separates from the opening, the discharge passage <NUM> is opened. When the valve body <NUM> closes the opening, the discharge passage <NUM> is closed. In a stroke of decreasing the capacity of the pump chamber <NUM>, the valve body <NUM> separates from the opening. In remaining strokes, the valve body <NUM> closes the opening. That is, the discharge valve <NUM> opens the discharge passage <NUM> (or the discharge through hole <NUM>) in the stroke of decreasing the capacity of the pump chamber <NUM>, and closes the discharge passage <NUM> (or the discharge through hole <NUM>) in the remaining strokes. The remaining strokes are strokes without the decrease of the capacity of the pump chamber <NUM>, and include a stroke of increasing the capacity of the pump chamber <NUM>, and a stroke of maintaining the capacity.

In the discharge stroke in which the discharge valve <NUM> is opened, and air in the pump chamber <NUM> is discharged to the discharge passage <NUM>, the valve body 31b of the suction valve <NUM> is pressed against the seat surface <NUM> by the pressure in the pump chamber <NUM>. At this time, the seal surface <NUM> of the valve body 31b comes into contact with the seat surface <NUM>. The minute channel <NUM> is formed on the seal surface <NUM>.

In the discharge stroke in which the capacity of the pump chamber <NUM> decreases, if the rising speed of the pressure in the pump chamber <NUM> is relatively high, that is, if the rotation speed of the motor <NUM> is relatively high, the channel <NUM> substantially functions as a diaphragm, and the amount of air that leaks from the pump chamber <NUM> to the suction passage <NUM> via the channel <NUM> becomes relatively small. For this reason, the discharge flow rate of the diaphragm pump <NUM> in this case is a flow rate substantially corresponding to the rotation speed of the motor <NUM>.

On the other hand, if the rotation speed of the motor <NUM> is relatively low, more specifically, if the rotation speed is as low as not to make the motor <NUM> stop due to shortage of torque or not to make the rotation unstable, the amount of air that leaks from the pump chamber <NUM> to the suction passage <NUM> via the channel <NUM> in the discharge stroke increases. For this reason, while rotating the motor <NUM> at the minimum rotation speed that is as low as not to make the motor <NUM> stop or not to make the rotation unstable, the discharge flow rate of the diaphragm pump <NUM> can be decreased as compared to a case where the leak structure <NUM> is not provided.

The seat surface <NUM> which the valve body 31b of the suction valve <NUM> comes into contact with or separates from is formed into a smooth surface. Hence, the leak structure <NUM> of the valve body 31b that repetitively comes into contact with the seat surface <NUM> hardly wears. The difficulty in wear means that dust is generated little, and the durability is high. In a case where a foreign substance is put in the leak structure <NUM>, when the valve body 31b moves along with opening/closing, the foreign substance drops from the leak structure <NUM> and is thus removed. For this reason, the leak structure <NUM> has high stability. Hence, according to this embodiment, it is possible to provide a diaphragm pump capable of suppressing the discharge flow rate to a remarkably low flow rate and improving performance stability and durability performance.

The leak structure <NUM> according to this embodiment is formed by the unevenness <NUM> provided all over the seal surface <NUM> of the valve body 31b. Hence, since air can be leaked from the whole region of the seal surface <NUM>, the discharge flow rate can be further decreased at the low rotation speed.

The unevenness <NUM> according to this embodiment is an unevenness formed by transferring the shape of the molding surface 42a for emboss processing, which is provided on the mold <NUM> used to mold the valve body 31b. For this reason, the unevenness <NUM> having a complex shape can easily be formed, and the unevenness <NUM> according to the performance of the diaphragm pump <NUM> can easily be formed.

According to the present invention, there is provided a diaphragm pump (<NUM>) comprising a diaphragm (<NUM>) including a deformation portion (<NUM>) having a cup shape, a partition (<NUM>) configured to close an opening portion of the deformation portion (<NUM>) and form a pump chamber (<NUM>) together with the deformation portion (<NUM>), a suction through hole (<NUM>) extending through the partition (<NUM>), a suction passage (<NUM>) communicating with the pump chamber (<NUM>) via the suction through hole (<NUM>), a discharge through hole (<NUM>) extending through the partition (<NUM>), a discharge passage (<NUM>) communicating with the pump chamber (<NUM>) via the discharge through hole (<NUM>), a driving mechanism (<NUM>) configured to convert rotation of a motor (<NUM>) into a reciprocating motion and alternately deform the deformation portion (<NUM>) in a direction of increasing a capacity of the pump chamber (<NUM>) and in a direction of decreasing the capacity of the pump chamber (<NUM>), a suction valve (<NUM>) attached to the partition (<NUM>) and configured to open the suction passage (<NUM>) (or the suction through hole (<NUM>)) in a stroke of increasing the capacity of the pump chamber (<NUM>) and close the suction passage (<NUM>) (or the suction through hole (<NUM>)) in a stroke without increasing the capacity, and a discharge valve (<NUM>) attached to the partition (<NUM>) in the discharge passage (<NUM>) and configured to open the discharge passage (<NUM>) (or the discharge through hole (<NUM>)) in a stroke of decreasing the capacity of the pump chamber (<NUM>) and close the discharge passage (<NUM>) (or the discharge through hole (<NUM>)) in a stroke without decreasing the capacity, wherein the partition (<NUM>) includes a seat surface (<NUM>) on a side facing the pump chamber (<NUM>), and the suction valve (<NUM>) includes a valve body (31b) configured to come into contact with or separate from the seat surface (<NUM>), and the valve body (31b) includes a leak structure (<NUM>) configured to form a channel (<NUM>) between the valve body (31b) and the seat surface (<NUM>).

When a fluid leaks from the leak structure (<NUM>) of the valve body (31b), the discharge flow rate can be suppressed small. Also, even if the leak structure (<NUM>) of the valve body (31b) repetitively comes into contact with the seat surface (<NUM>) of the partition (<NUM>), the leak structure (<NUM>) hardly wears. Furthermore, in a case where a foreign substance is put in the leak structure (<NUM>), when the valve body (31b) moves along with opening/closing, the foreign substance drops from the leak structure (<NUM>) and is thus removed. It is therefore possible to provide a diaphragm pump capable of improving performance stability and durability performance while employing the configuration capable of suppressing the discharge flow rate to a remarkably low flow rate.

The valve body (31b) may include a seal surface (<NUM>) facing the seat surface (<NUM>). The leak structure (<NUM>) may include an unevenness (<NUM>) provided on the seal surface (<NUM>). The unevenness (<NUM>) may include an angled portion and/or a valley portion having a tilting surface.

The unevenness (<NUM>) may be provided all over the seal surface (<NUM>). The unevenness (<NUM>) may be provided only on the outer edge portion of the seal surface (<NUM>), which comes into contact with the seat surface (<NUM>) when the suction valve (<NUM>) closes the suction through hole (<NUM>). The unevenness (<NUM>) may be provided at least on the outer edge portion of the seal surface (<NUM>).

The unevenness (<NUM>) may be an unevenness formed by transferring a shape of a molding surface (42a) for emboss processing, which is provided on a mold (<NUM>) used to mold the valve body (31b).

The seat surface (<NUM>) may be a smooth surface. When the seat surface (<NUM>) is formed into a smooth surface, the leak structure (<NUM>) of the valve body (31b) that repetitively comes into contact with the seat surface (<NUM>) more hardly wears.

Claim 1:
A diaphragm pump (<NUM>) comprising:
a diaphragm (<NUM>) including a deformation portion (<NUM>) having a cup shape;
a partition (<NUM>) configured to close an opening portion of the deformation portion (<NUM>) and form a pump chamber (<NUM>) together with the deformation portion (<NUM>);
a suction through hole (<NUM>) extending through the partition (<NUM>);
a suction passage (<NUM>) communicating with the pump chamber (<NUM>) via the suction through hole (<NUM>);
a discharge through hole (<NUM>) extending through the partition (<NUM>);
a discharge passage (<NUM>) communicating with the pump chamber (<NUM>) via the discharge through hole (<NUM>);
a driving mechanism (<NUM>) configured to convert rotation of a motor (<NUM>) into a reciprocating motion and alternately deform the deformation portion (<NUM>) in a direction of increasing a capacity of the pump chamber (<NUM>) and in a direction of decreasing the capacity of the pump chamber (<NUM>);
a suction valve (<NUM>) attached to the partition (<NUM>) and configured to open the suction passage (<NUM>) in a stroke of increasing the capacity of the pump chamber (<NUM>) and close the suction passage (<NUM>) in a stroke without increasing the capacity; and
a discharge valve (<NUM>) attached to the partition (<NUM>) in the discharge passage (<NUM>) and configured to open the discharge passage (<NUM>) in a stroke of decreasing the capacity of the pump chamber (<NUM>) and close the discharge passage (<NUM>) in a stroke without decreasing the capacity,
wherein the partition (<NUM>) includes a seat surface (<NUM>) on a side facing the pump chamber (<NUM>), and
the suction valve (<NUM>) includes a valve body (31b) configured to come into contact with or separate from the seat surface (<NUM>),
characterized in that the valve body (31b) includes a leak structure (<NUM>) configured to form a channel (<NUM>) between the valve body (31b) and the seat surface (<NUM>).