Patent Description:
For example, a fuel pump that supplies fuel from a fuel tank to a fuel injection device is mounted on an engine unit mounted on a working machine such as a brush cutter. For example, a diaphragm pump may be used as a fuel pump to supply fuel without using electric power. This diaphragm pump operates by receiving a pulsating pressure in a crank chamber of an engine. Such a diaphragm pump is described, for example, in <CIT>. Also, <CIT> discloses a diaphragm pump according to the preamble of claim <NUM>.

In the engine unit described above, it is preferable that the fuel with an increased pressure can be supplied to the fuel injection device in order to improve the atomization of the fuel in the fuel injection device. However, in the configuration described in Patent Document <NUM> using a diaphragm pump, the fuel can be pressurized to only the same level as the internal pressure of the crank chamber, and further improvement of the diaphragm pump is required.

Accordingly, the present disclosure describes a diaphragm pump capable of further pressurizing fuel by receiving a pulsating pressure in a crank chamber of an engine to supply the further pressurized fuel. This is achieved by a diaphragm pump having the features of claim <NUM>.

An aspect of the present disclosure is [<NUM>] "A diaphragm pump (<NUM>) that operates by receiving a pulsating pressure in a crank chamber (2a) of an engine (<NUM>), the diaphragm pump including: a low pressure side diaphragm (<NUM>) forming a part of a pulsation operating chamber (R11) to which the pulsating pressure is transmitted and configured to operate by receiving the pulsating pressure; a high pressure side diaphragm (<NUM>) forming a part of a pump chamber (R21) for supplying fuel to the engine (<NUM>) and configured to send the fuel to the engine (<NUM>) by operating; and a connecting portion (<NUM>) connecting the low pressure side diaphragm (<NUM>) and the high pressure side diaphragm (<NUM>) to each other, wherein the high pressure side diaphragm (<NUM>) operates in conjunction with the low pressure side diaphragm (<NUM>) by being connected to the low pressure side diaphragm (<NUM>) by the connecting portion (<NUM>), and wherein an area of a high pressure side operating portion (20a) that is a portion of the high pressure side diaphragm (<NUM>) which operates in conjunction with the low pressure side diaphragm (<NUM>) is smaller than an area of a low pressure side operating portion (10a) that is a portion of the low pressure side diaphragm (<NUM>) which operates by receiving the pulsating pressure.

In this diaphragm pump (<NUM>), the diaphragm (the low pressure side diaphragm (<NUM>)) that operates by receiving the pulsating pressure in the crank chamber (2a) and the diaphragm (the high pressure side diaphragm (<NUM>)) that sends the fuel are separately provided. The high pressure side diaphragm (<NUM>) operates in conjunction with the low pressure side diaphragm (<NUM>), and the area of the high pressure side operating portion (20a) is smaller than the area of the low pressure side operating portion (10a). That is, due to the difference in area between the low pressure side operating portion (10a) and the high pressure side operating portion (20a), the high pressure side diaphragm (<NUM>) can apply a pressure higher than the pulsating pressure in the crank chamber (2a) to the fuel. In this way, the diaphragm pump (<NUM>) can further pressurize the fuel by receiving the pulsating pressure in the crank chamber (2a) of the engine (<NUM>) and supply the further pressurized fuel.

The above-described diaphragm pump (<NUM>) may be [<NUM>] "The diaphragm pump (<NUM>) according to the above-describe [<NUM>], further including: a low pressure side backup (<NUM>) attached to the low pressure side operating portion (10a); and a high pressure side backup (<NUM>) attached to the high pressure side operating portion (20a), wherein an area of the low pressure side backup (<NUM>) is larger than an area of the high pressure side backup (<NUM>). " In this case, in the diaphragm pump (<NUM>), it is possible to curb unintended deflection of the low pressure side diaphragm (<NUM>) and the high pressure side diaphragm (<NUM>) with the low pressure side backup (<NUM>) and the high pressure side backup (<NUM>) and to appropriately operate the low pressure side diaphragm (<NUM>) and the high pressure side diaphragm (<NUM>).

The above-described diaphragm pump (<NUM>) may be [<NUM>] "The diaphragm pump (<NUM>) according to above-described [<NUM>], wherein the low pressure side diaphragm (<NUM>) has an annular low pressure side movable portion (10b) around the low pressure side backup (<NUM>), wherein the high pressure side diaphragm (<NUM>) has an annular high pressure side movable portion (20b) around the high pressure side backup (<NUM>), and wherein a width of the annular low pressure side movable portion (10b) in a radial direction is smaller than a width of the annular high pressure side movable portion (20b) in a radial direction. " Here, in a case where the width of the low pressure side movable portion (10b) is increased, it is conceivable that only this low pressure side movable portion (10b) will move by receiving the pulsating pressure in the crank chamber (2a). Therefore, by reducing the width of the low pressure side movable portion (10b), it is possible to curb only the low pressure side movable portion (10b) being movable. As a result, the entire low pressure side diaphragm (<NUM>) moves, and the high pressure side diaphragm (<NUM>) can be appropriately operated in conjunction with the low pressure side diaphragm (<NUM>). Further, since the width of the high pressure side movable portion (20b) is larger than the width of the low pressure side movable portion (10b), a stroke (a movement amount) of the high pressure side diaphragm (<NUM>) can be ensured to be larger. As a result, when the high pressure side diaphragm (<NUM>) operates in conjunction with the low pressure side diaphragm (<NUM>), the high pressure side diaphragm (<NUM>) can be operated without being restricted in the amount of movement caused by the width of the high pressure side movable portion (20b).

According to the aspect of the present disclosure, it is possible to further pressurize fuel by receiving a pulsating pressure in a crank chamber of an engine and to supply the further pressurized fuel.

Embodiments of the present disclosure will be described below with reference to the drawings. In the drawings, the same or corresponding elements are denoted by the same reference signs, and redundant description will be omitted.

As shown in <FIG>, a diaphragm pump <NUM> according to the present embodiment functions as a fuel pump that supplies fuel to an engine <NUM>. The diaphragm pump <NUM> operates by receiving a pulsating pressure in a crank chamber 2a of the engine <NUM> (pressure fluctuation of gas in the crank chamber 2a). Here, the diaphragm pump <NUM> is connected to the crank chamber 2a of the engine <NUM> with a pipe L3. As a result, the diaphragm pump <NUM> can receive the pulsating pressure of the crank chamber 2a via the pipe L3.

The diaphragm pump <NUM> sucks the fuel from the fuel tank <NUM> via a pipe L2 and supplies the fuel with an increased pressure to a fuel injection device 2b provided in the engine <NUM> via a pipe L1. Further, the diaphragm pump <NUM> may have a mechanism for returning surplus fuel not supplied to the engine <NUM> of the fuel sucked from the fuel tank <NUM> to the tank.

More specifically, the diaphragm pump <NUM> includes a low pressure side diaphragm <NUM>, a high pressure side diaphragm <NUM>, a connecting portion <NUM>, a main body portion <NUM>, an intake valve <NUM>, and a discharge valve <NUM>, as shown in <FIG>.

The main body portion <NUM> has therein a first operating region R10, a second operating region R20, and the like, which will be described later. In the present embodiment, the main body portion <NUM> is formed by stacking a first main body portion <NUM>, a second main body portion <NUM>, a third main body portion <NUM>, and a fourth main body portion <NUM> in that order. A gasket is appropriately disposed between the stacked members of the first main body portion <NUM> to the fourth main body portion <NUM>. The first main body portion <NUM> to the fourth main body portion <NUM> are fixed to each other by a screw (not shown) or the like.

The first operating region R10 is formed between the first main body portion <NUM> and the second main body portion <NUM>. The first operating region R10 is a region in which the low pressure side diaphragm <NUM> operates. The general shape of the first operating region R10 is a thin columnar shape whose axis is a stacking direction of the first main body portion <NUM> and the second main body portion <NUM>.

Here, a recess 41a is provided in a surface of the first main body portion <NUM> on a side of the second main body portion <NUM>. Further, a recess 42a is provided in a surface of the second main body portion <NUM> on a side of the first main body portion <NUM>. The recess 41a and the recess 42a face each other. The first operating region R10 is formed by the recess 41a of the first main body portion <NUM> and the recess 42a of the second main body portion <NUM>.

A pulsation transmitting port S1 is formed in the first main body portion <NUM>. The pipe L3 (see <FIG>) leading to the crank chamber 2a of the engine <NUM> is connected to the pulsation transmitting port S1. Further, a pulsation transmitting channel L11 that connects the pulsation transmitting port S1 and the first operating region R10 to each other is formed in the first main body portion <NUM>.

The second operating region R20 is formed between the second main body portion <NUM> and the third main body portion <NUM>. The second operating region R20 is a region in which the high pressure side diaphragm <NUM> operates. The general shape of the second operating region R20 is a thin columnar shape whose axis is a stacking direction of the second main body portion <NUM> and the third main body portion <NUM>.

Here, a recess 42b is provided in a surface of the second main body portion <NUM> on a side of the third main body portion <NUM>. A recess 43a is provided in a surface of the third main body portion <NUM> on a side of the second main body portion <NUM>. The recess 42b and the recess 43a face each other. The second operating region R20 is formed by the recess 42b of the second main body portion <NUM> and the recess 43a of the third main body portion <NUM>.

An intake port S2 and a discharge port S3 are formed in the fourth main body portion <NUM>. The pipe L2 (see <FIG>) leading to the fuel tank <NUM> is connected to the intake port S2. The pipe L1 leading to the fuel injection device 2b of the engine <NUM> is connected to the discharge port S3.

A low pressure side diaphragm <NUM> is disposed between the first main body portion <NUM> and the second main body portion <NUM>. That is, the low pressure side diaphragm <NUM> partitions the first operating region R10 into two. One of the spaces defined by the low pressure side diaphragm <NUM> is a pulsation operating chamber R11 and the other is a first back chamber R12. The pulsation operating chamber R11 is the space between the low pressure side diaphragm <NUM> and the recess 41a of the first main body portion <NUM> in the first operating region R10. The pulsation transmitting channel L11 is connected to the pulsation operating chamber R11 and transmits the pulsating pressure to the low pressure side diaphragm <NUM>.

The pulsation operating chamber R11 receives the pulsating pressure. The pulsation operating chamber R11 communicates with the crank chamber 2a via the pulsation transmitting channel L11 and the pipe L3. Hereinafter, the space between the low pressure side diaphragm <NUM> and the recess 41a of the first main body portion <NUM> in the first operating region R10 is referred to as a pulsation operating chamber R11. The pulsating pressure of the crank chamber 2a is transmitted to the pulsation operating chamber R11 via the pulsation transmitting channel L11 and the pipe L3.

Here, in the present embodiment, two plates <NUM> are disposed between the first main body portion <NUM> and the second main body portion <NUM>. The low pressure side diaphragm <NUM> is disposed between the two plates <NUM>. Further, the plate <NUM> is provided with an opening portion 12a in a portion located within the first operating region R10. The opening portion 12a has a circular shape. That is, a portion of the low pressure side diaphragm <NUM> in the opening portion 12a of the plate <NUM> is an operating range of the low pressure side diaphragm <NUM>. Hereinafter, the portion of the low pressure side diaphragm <NUM> in the opening portion 12a of the plate <NUM> is referred to as a low pressure side operating portion 10a.

A low pressure side backup <NUM> is attached to the low pressure side operating portion 10a of the low pressure side diaphragm <NUM>. The low pressure side backup <NUM> is a plate-shaped member fixed to the low pressure side operating portion 10a. The low pressure side backup <NUM> supports the low pressure side diaphragm <NUM>. In the present embodiment, two low pressure side backups <NUM> are provided. The low pressure side diaphragm <NUM> is sandwiched between the two low pressure side backups <NUM>. The diameter of the low pressure side backup <NUM> is smaller than the inner diameter of the opening portion 12a of the plate <NUM>. That is, as shown in <FIG>, an annular gap is provided between the outer peripheral edge of the low pressure side backup <NUM> and the circular opening portion 12a of the plate <NUM> in a radial direction of the circular low pressure side backup <NUM>. In the present embodiment, the corner of the outer peripheral edge of the low pressure side backup <NUM> is rounded not to damage the low pressure side diaphragm <NUM> when the low pressure side diaphragm <NUM> operates (see <FIG>).

In this way, the low pressure side diaphragm <NUM> faces the pulsation operating chamber R11. That is, the low pressure side diaphragm <NUM> forms a part of the pulsation operating chamber R11 to which the pulsating pressure of the crank chamber 2a of the engine <NUM> is transmitted. For this reason, the low pressure side diaphragm <NUM> operates by receiving the pulsating pressure of the crank chamber 2a.

As shown in <FIG>, the high pressure side diaphragm <NUM> is disposed between the second main body portion <NUM> and the third main body portion <NUM>. That is, the high pressure side diaphragm <NUM> partitions the second operating region R20 into two. One of the spaces defined by the high pressure side diaphragm <NUM> is a pump chamber R21 and the other is a second back chamber R22. The pump chamber R21 is the space between the high pressure side diaphragm <NUM> and the recess 43a of the third main body portion <NUM> in the second operating region R20. The pump chamber R21 receives the fuel and sends the fuel to the engine <NUM>. A volume of the pump chamber R21 is smaller than a volume of the pulsation operating chamber R11.

A portion of the high pressure side diaphragm <NUM> in the second operating region R20 is an operating range of the high pressure side diaphragm <NUM>. Hereinafter, the portion of the high pressure side diaphragm <NUM> in the second operating region R20 is referred to as a high pressure side operating portion 20a.

A high pressure side backup <NUM> is attached to the high pressure side operating portion 20a of the high pressure side diaphragm <NUM>. The high pressure side backup <NUM> is a plate-shaped member fixed to the high pressure side operating portion 20a. The high pressure side backup <NUM> supports the high pressure side diaphragm <NUM>. In the present embodiment, two high pressure side backups <NUM> are provided. The high pressure side diaphragm <NUM> is sandwiched between the two high pressure side backups <NUM>. The diameter of the high pressure side backup <NUM> is smaller than the diameter of the opening edge of each of the recess 42b of the second main body portion <NUM> and the recess 43a of the third main body portion <NUM>. That is, as shown in <FIG>, an annular gap is provided between the outer peripheral edge of the high pressure side backup <NUM> and the opening edge of the recess 43a of the third main body portion <NUM> in a radial direction of the circular high pressure side backup <NUM>. In the present embodiment, the outer peripheral edge of the high pressure side backup <NUM> is curved away from the high pressure side diaphragm <NUM> not to damage the high pressure side diaphragm <NUM> when the high pressure side diaphragm <NUM> operates (see <FIG>).

In this way, the high pressure side diaphragm <NUM> faces the pump chamber R21. The pump chamber R21 produces pressurized fuel for supply to the fuel injection device 2b of the engine <NUM>, as will be described later. That is, the high pressure side diaphragm <NUM> forms a part of the pump chamber R21 from which the fuel is supplied to the fuel injection device 2b of the engine <NUM>. The high pressure side diaphragm <NUM> operates in conjunction with the low pressure side diaphragm <NUM> to suck the fuel from the fuel tank <NUM> and to send the fuel to the fuel injection device 2b of the engine <NUM>.

As shown in <FIG>, an intake channel L12 that connects the intake port S2 and the pump chamber R21 to each other is formed in the main body portion <NUM>. The intake channel L12 is fluidly coupled with the pump chamber R21. That is, the intake channel L12 guides the fuel guided from the fuel tank <NUM> to the intake port S2 via the pipe L2 to the pump chamber R21. In the present embodiment, the intake channel L12 is formed by grooves and holes provided in the second main body portion <NUM>, the third main body portion <NUM>, and the fourth main body portion <NUM>.

Further, a discharge channel L13 that connects the pump chamber R21 and the discharge port S3 to each other is formed in the main body portion <NUM>. The discharge channel L13 is fluidly coupled with the pump chamber R21. That is, the discharge channel L13 guides the fuel pressurized in the pump chamber R21 to the discharge port S3. In the present embodiment, the discharge channel L13 is formed by grooves and holes provided in the second main body portion <NUM>, the third main body portion <NUM>, and the fourth main body portion <NUM>.

The second main body portion <NUM> is located between the first operating region R10 and the second operating region R20. The second main body portion <NUM> is located between the low pressure side diaphragm <NUM> and the high pressure side diaphragm <NUM>. The second main body portion <NUM> is an example of wall portion. A guide hole 42c penetrates the second main body portion <NUM>.

The connecting portion <NUM> is passed through a guide hole 42c. The connecting portion <NUM> is movable in a penetrating direction of the guide hole 42c. The connecting portion <NUM> connects the low pressure side diaphragm <NUM> and the high pressure side diaphragm <NUM> to each other. The connecting portion <NUM> operates the high pressure side diaphragm <NUM> to send the fuel to the engine <NUM> in response to the low pressure side diaphragm <NUM> receiving the pulsating pressure.

The connecting portion <NUM> has a first end portion 30a and a second end portion 30b. The first end portion 30a is attached to the low pressure side diaphragm <NUM>. The second end portion 30b is attached to the high pressure side diaphragm <NUM>. For example, the first end portion 30a is fixed to a center of the low pressure side diaphragm <NUM>, and the second end portion 30b is fixed to a center of the high pressure side diaphragm <NUM>.

The connecting portion <NUM> includes a sleeve <NUM> and a rivet <NUM>. The sleeve <NUM> is disposed between the low pressure side diaphragm <NUM> and the high pressure side diaphragm <NUM>. The sleeve <NUM> is passed through the guide hole 42c. The rivet <NUM> is passed through an inside of the sleeve <NUM> and fix the sleeve <NUM> to the low pressure side diaphragm <NUM> and the high pressure side diaphragm <NUM>. The sleeve <NUM> is disposed between the low pressure side backup <NUM> provided on a surface of the low pressure side diaphragm <NUM> on a side of the second main body portion <NUM>, and a high pressure side backup <NUM> provided on a surface of the high pressure side diaphragm <NUM> on a side of the second main body portion <NUM>. The sleeve <NUM> is fixed to the low pressure side diaphragm <NUM> via the low pressure side backup <NUM> and fixed to the high pressure side diaphragm <NUM> via the high pressure side backup <NUM>.

The rivet <NUM> fixes the low pressure side diaphragm <NUM> and the high pressure side diaphragm <NUM> to the sleeve <NUM> in a state where the sleeve <NUM> is sandwiched between the low pressure side diaphragm <NUM> and the high pressure side diaphragm <NUM>. Here, the rivet <NUM> collectively fixes the two low pressure side backups <NUM> and the low pressure side diaphragm <NUM> and the two high pressure side backups <NUM> and the high pressure side diaphragm <NUM> to the sleeve <NUM>. As a result, the high pressure side diaphragm <NUM> operates in conjunction with the low pressure side diaphragm <NUM>. That is, the high pressure side diaphragm <NUM> operates in conjunction with the low pressure side diaphragm <NUM> by being connected to the low pressure side diaphragm <NUM> by the connecting portion <NUM>, wherein the low pressure side diaphragm operates with the pulsating pressure in the crank chamber 2a of the engine <NUM>.

The guide hole 42c provided in the second main body portion <NUM> has a cylindrical shape extending in a direction in which the low pressure side diaphragm <NUM> and the high pressure side diaphragm <NUM> are arranged. The outer peripheral surface of the sleeve <NUM> of the connecting portion <NUM> is in slidable contact with the inner peripheral surface of the guide hole 42c of the second main body portion <NUM>. That is, the movement direction of the sleeve <NUM> of the connecting portion <NUM> is guided by the guide hole 42c of the second main body portion <NUM>. As a result, the operating directions of the low pressure side diaphragm <NUM> and the high pressure side diaphragm <NUM> are defined.

Here, in the high pressure side diaphragm <NUM>, a portion of the high pressure side operating portion 20a described above operates in conjunction with the low pressure side diaphragm <NUM>. In the low pressure side diaphragm <NUM>, a portion of the low pressure side operating portion 10a described above operates by receiving the pulsating pressure in the crank chamber 2a of the engine <NUM>. In the present embodiment, an area of the high pressure side operating portion 20a of the high pressure side diaphragm <NUM> is smaller than an area of the low pressure side operating portion 10a of the low pressure side diaphragm <NUM>.

Further, an area of the low pressure side backup <NUM> is larger than an area of the high pressure side backup <NUM>. Here, the area of the low pressure side backup <NUM> is an area of the low pressure side backup <NUM> located in the pulsation operating chamber R11 of the two low pressure side backups <NUM> in the present embodiment. Further, the area of the low pressure side backup <NUM> here is an area of a surface facing the inside of the pulsation operating chamber R11 (a surface facing a side of the recess 41a of the first main body portion <NUM>) of the outer surface of the low pressure side backup <NUM> located in the pulsation operating chamber R11. Similarly, the area of the high pressure side backup <NUM> is an area of the high pressure side backup <NUM> located in the pump chamber R21 of the two high pressure side backups <NUM> in the present embodiment. Further, the area of the high pressure side backup <NUM> here is an area of a surface facing the inside of the pump chamber R21 (a surface facing a side of the recess 43a of the third main body portion <NUM>) of the outer surface of the pump chamber R21 located in the high pressure side backup <NUM>.

As described above, the low pressure side diaphragm <NUM> is sandwiched between the two low pressure side backups <NUM>. For this reason, a movable portion of the low pressure side diaphragm <NUM> is a portion between the outer peripheral edge of the low pressure side backup <NUM> and the inner peripheral edge of the plate <NUM>. That is, the low pressure side diaphragm <NUM> has an annular low pressure side movable portion 10b (a movable portion) around the low pressure side backup <NUM> (see <FIG>).

Similarly, the high pressure side diaphragm <NUM> is sandwiched between the two high pressure side backups <NUM>. For this reason, a movable portion of the high pressure side diaphragm <NUM> is a portion between the outer peripheral edge of the high pressure side backup <NUM> and the opening edge of the recess 42a of second main body portion <NUM> or the like. That is, the high pressure side diaphragm <NUM> has an annular high pressure side movable portion 20b (a movable portion) around the high pressure side backup <NUM>.

Here, in the present embodiment, a width A10 of the annular low pressure side movable portion 10b in a radial direction, which is shown in <FIG>, is smaller than a width A20 of the annular high pressure side movable portion 20b in a radial direction, which is shown in <FIG>.

The intake valve <NUM> is provided in the intake channel L12. The discharge valve <NUM> is provided in the discharge channel L13. The intake valve <NUM> and the discharge valve <NUM> are opened and closed such that when the high pressure side diaphragm <NUM> operates, the fuel is sent from the intake channel L12 to the pump chamber R21 and the fuel is discharged from the pump chamber R21 via the discharge channel L13. That is, the intake valve <NUM> and the discharge valve <NUM> are opened and closed such that a pump mechanism is realized through the operation of the high pressure side diaphragm <NUM>.

More specifically, the intake valve <NUM> includes a valve body <NUM> and a spring <NUM>. The valve body <NUM> may be configured to selectively open or close the intake channel L12. Here, the valve body <NUM> may be configured to selectively open or close an opening portion of a flow channel portion provided in the third main body portion <NUM> of the members forming the intake channel L12. The spring <NUM> biases the valve body <NUM> such that the intake channel L12 is closed. The intake valve <NUM> allows circulation of the fuel only in a direction from the intake port S2 to the pump chamber R21 in the intake channel L12 and cuts off circulation of the fuel in a direction opposite to the above-described direction by opening and closing the valve body <NUM>.

The discharge valve <NUM> has a valve body <NUM> and a spring <NUM>. The valve body <NUM> may be configured to selectively open or close the discharge channel L13. Here, the valve body <NUM> may be configured to selectively open or close an opening portion of a flow channel portion provided in the third main body portion <NUM> of the members forming the discharge channel L13. The spring <NUM> biases the valve body <NUM> such that the discharge channel L13 is closed. The discharge valve <NUM> allows circulation of the fuel only in a direction from the pump chamber R21 to the discharge port S3 in the discharge channel L13 and cuts off circulation of the fuel in a direction opposite to the above-described direction by opening and closing the valve body <NUM>.

As described above, in this diaphragm pump <NUM>, the low pressure side diaphragm <NUM> that operates by receiving the pulsating pressure in the crank chamber 2a and the high pressure side diaphragm <NUM> that sends the fuel are separately provided. The high pressure side diaphragm <NUM> operates in conjunction with the low pressure side diaphragm <NUM>, and the area of the high pressure side operating portion 20a is smaller than the area of the low pressure side operating portion 10a. That is, due to the difference in area between the low pressure side operating portion 10a and the high pressure side operating portion 20a, the high pressure side diaphragm <NUM> can apply a pressure higher than the pulsating pressure in the crank chamber 2a to the fuel. In this way, the diaphragm pump <NUM> can further pressurize the fuel by receiving the pulsating pressure in the crank chamber 2a of the engine <NUM> and supply the further pressurized fuel.

In the diaphragm pump <NUM>, the area of the low pressure side backup <NUM> attached to the low pressure side diaphragm <NUM> is larger than the area of the high pressure side backup <NUM> attached to the high pressure side diaphragm <NUM>. In this case, in the diaphragm pump <NUM>, it is possible to curb unintended deflection of the low pressure side diaphragm <NUM> and the high pressure side diaphragm <NUM> with the low pressure side backup <NUM> and the high pressure side backup <NUM> and to appropriately operate the low pressure side diaphragm <NUM> and the high pressure side diaphragm <NUM>.

The low pressure side diaphragm <NUM> has the annular low pressure side movable portion 10b around the low pressure side backup <NUM>. The high pressure side diaphragm <NUM> has the annular high pressure side movable portion 20b around the high pressure side backup <NUM>. Further, the width A10 of the annular low pressure side movable portion 10b in the radial direction is smaller than the width A20 of the annular high pressure side movable portion 20b in the radial direction.

Here, in a case where the width of the low pressure side movable portion 10b is increased, it is conceivable that only this low pressure side movable portion 10b will move by receiving the pulsating pressure in the crank chamber 2a. Therefore, by reducing the width of the low pressure side movable portion 10b, it is possible to curb only the low pressure side movable portion 10b being movable. As a result, the entire low pressure side diaphragm <NUM> moves, and the high pressure side diaphragm <NUM> can be appropriately operated in conjunction with the low pressure side diaphragm <NUM>.

Further, since the width of the high pressure side movable portion 20b is larger than the width of the low pressure side movable portion 10b, a stroke (a movement amount) of the high pressure side diaphragm <NUM> can be ensured to be larger. As a result, when the high pressure side diaphragm <NUM> operates in conjunction with the low pressure side diaphragm <NUM>, the high pressure side diaphragm <NUM> can be operated without being restricted in the amount of movement caused by the width of the high pressure side movable portion 20b.

Claim 1:
A diaphragm pump (<NUM>) that operates by receiving a pulsating pressure in a crank chamber (2a) of an engine (<NUM>), the diaphragm pump comprising:
a low pressure side diaphragm (<NUM>) forming a part of a pulsation operating chamber (R11) to which the pulsating pressure is transmitted and configured to operate by receiving the pulsating pressure, wherein the low pressure side diaphragm (<NUM>) has a low pressure side operating portion (10a) which operates by receiving the pulsating pressure; and
a high pressure side diaphragm (<NUM>) forming a part of a pump chamber (R21) for supplying fuel to the engine (<NUM>) and configured to send the fuel to the engine (<NUM>) by operating, wherein the high pressure side diaphragm (<NUM>) has a high pressure side operating portion (20a) which operates in conjunction with the low pressure side diaphragm (<NUM>), and wherein an area of the high pressure side operating portion (20a) is smaller than an area of the low pressure side operating portion (10a)
a connecting portion (<NUM>) connecting the low pressure side diaphragm (<NUM>) and the high pressure side diaphragm (<NUM>) to each other, wherein the connecting portion (<NUM>) comprises a first end portion (30a) fixed to the low pressure side diaphragm (<NUM>), and a second end portion (30b) fixed to the high pressure side diaphragm (<NUM>) to operate the high pressure side diaphragm (<NUM>) in conjunction with the low pressure side diaphragm (<NUM>),
characterized in that:
the diaphragm pump (<NUM>) further comprises:
a wall portion (<NUM>) located between the low pressure side diaphragm (<NUM>) and the high pressure side diaphragm (<NUM>);
a guide hole (42c) penetrating the wall portion (<NUM>),
wherein the connecting portion (<NUM>) passes through the guide hole (42c) and is movable relative to the guide hole (42c) in a penetrating direction of the guide hole (42c).