ELECTROMAGNETIC PUMP

Abstract

An electromagnetic pump including a piston that reciprocates inside a cylinder; an electromagnetic portion and a biasing member that respectively forwardly and backwardly move the piston; a support for the biasing member that defines a chamber with the cylinder and the piston; a valve incorporated into the support member that allows fluid to move from an intake port to the chamber and prohibits reverse flow; and a valve that allows the fluid to move from the chamber to a discharge port and prohibits reverse flow. The support member includes a bottomed hollow portion accommodating at least a portion of the intake on-off valve, and a hole providing communication between a bottom portion of the hollow portion on the chamber side and the chamber. The support member includes a portion that supports the biasing member, and a portion that communicates with the hole and projects from the support toward the piston.

Description

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2011-068808 filed on Mar. 25, 2011 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to an electromagnetic pump including: a cylinder; a piston that can reciprocate inside the cylinder; an electromagnetic portion that forwardly moves the piston; a biasing member that backwardly moves the piston; a support member that supports the biasing member and, with the cylinder and the piston, defines a pump chamber; an intake on-off valve that is incorporated into the support member, and allows a hydraulic fluid to move from an intake port to the pump chamber and prohibits reverse movement of the hydraulic fluid; and a discharge on-off valve that allows the hydraulic fluid to move from the pump chamber to a discharge port and prohibits reverse movement of the hydraulic fluid.

DESCRIPTION OF THE RELATED ART

A past example of this type of electromagnetic pump (e.g., see Japanese Patent Application Publication No, JP-A-2011-21593) includes: a cylinder; a piston that reciprocates inside the cylinder to change the volume inside a pump chamber; a solenoid portion that forwardly moves the piston; a spring that backwardly moves the piston; an intake check valve that allows a hydraulic fluid to move from an intake port to the pump chamber and prohibits reverse movement of the hydraulic fluid; and a discharge check valve that allows the hydraulic fluid to move from the pump chamber to a discharge port and prohibits reverse movement of the hydraulic fluid. According to this electromagnetic pump, the intake check valve and the discharge check valve are accommodated inside the cylinder. The intake check valve is configured from a ball; a hollow cylindrical body that accommodates the ball therein, and is formed with an axially center hole that provides communication between the intake port and the pump chamber and forms an opening portion of the intake port with an inner diameter smaller than the outer diameter of the ball; a spring that biases the ball with respect to the opening portion of the intake port in a direction opposite from the direction in which the hydraulic oil flows from the intake port; and a spring seat that receives the spring. In the intake check valve, the spring seat faces the pump chamber, and a surface of the spring seat on the pump chamber side also supports the spring that backwardly moves the piston.

SUMMARY OF THE INVENTION

In the type of electromagnetic pump described above, the piston and the intake check valve are accommodated facing one another inside the cylinder, and the pump chamber is defined by the cylinder, the piston, and the intake check valve. Therefore, how the intake check valve is configured is an extremely critical factor for determining the volume of the pump chamber and also determining the biasing force of the spring accommodated inside the pump chamber.

An electromagnetic pump of the present invention further improves discharge performance.

The electromagnetic pump of the present invention employs the following to achieve the above.

An electromagnetic pump according to the present invention includes: a cylinder; a piston that can reciprocate inside the cylinder; an electromagnetic portion that forwardly moves the piston; a biasing member that backwardly moves the piston; a support member that supports the biasing member and, with the cylinder and the piston, defines a pump chamber; an intake on-off valve that is incorporated into the support member, and allows a hydraulic fluid to move from an intake port to the pump chamber and prohibits reverse movement of the hydraulic fluid; and a discharge on-off valve that allows the hydraulic fluid to move from the pump chamber to a discharge port and prohibits reverse movement of the hydraulic fluid. In the electromagnetic pump, the support member includes therein a bottomed hollow portion accommodating from the intake port side at least a portion of the intake on-off valve, and a communication hole providing communication between a bottom portion of the hollow portion on the pump chamber side and the pump chamber. In addition, the support member is formed with a support portion that supports the biasing member, and a projection portion that is in communication with the communication hole and projects from the support portion toward the piston side.

According to the present invention, the electromagnetic pump includes: a cylinder; a piston that can reciprocate inside the cylinder; an electromagnetic portion that forwardly moves the piston; a biasing member that backwardly moves the piston; a support member that supports the biasing member and, with the cylinder and the piston, defines a pump chamber; an intake on-off valve that is incorporated into the support member, and allows a hydraulic fluid to move from an intake port to the pump chamber and prohibits reverse movement of the hydraulic fluid; and a discharge on-off valve that allows the hydraulic fluid to move from the pump chamber to a discharge port and prohibits reverse movement of the hydraulic fluid. In the electromagnetic pump, the support member includes therein a bottomed hollow portion accommodating from the intake port side at least a portion of the intake on-off valve, and a communication hole providing communication between a bottom portion of the hollow portion on the pump chamber side and the pump chamber. In addition, the support member is formed with a support portion that supports the biasing member, and a projection portion that is in communication with the communication hole and projects from the support portion toward the piston side. Thus, the spacing for supporting the biasing member can be set by the support portion, and the volume inside the pump chamber can be controlled by the projection portion, thereby further improving discharge performance.

In the electromagnetic pump of the present invention described above, a diameter of the projection portion on the piston side may be formed smaller than a diameter of the projection portion on the support portion side. In the electromagnetic pump according to this aspect of the present invention, the projection portion may be formed into a truncated conical shape. Thus, processing of the support member can be made easier.

In the electromagnetic pump of the present invention, the hydraulic fluid may be discharged by the biasing member backwardly moving the piston. Since the biasing force of the biasing member exhibits less variation due to temperature compared to the electromagnetic force, the axial length of the electromagnetic pump can be shortened by using the biasing force to discharge the hydraulic fluid, and application of the present invention enables further shortening of the axial length.

In the electromagnetic pump of the present invention, the hollow portion of the support member may be formed such that the bottom portion is more toward the piston side than a support surface of the support portion. Thus, the length of the support member in the axial direction can be shortened and the overall pump can be downsized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural diagram that shows the overall configuration of an electromagnetic pump 20 as an embodiment of the present invention;

FIG. 2 is a perspective view of a piston 50 and an intake check valve 60 inserted inside a cylinder 42; and

FIG. 3 is an exterior view that shows the exterior of a valve body 62.

DETAILED DESCRIPTION OF THE EMBODIMENT

Next, an embodiment of the present invention will be described.

FIG. 1 is a structural diagram that shows the overall configuration of an electromagnetic pump 20 as an embodiment of the present invention. As shown in the figure, the electromagnetic pump 20 of the embodiment is configured as a piston pump that reciprocates a piston 50 to pressure-feed a hydraulic oil. The electromagnetic pump 20 also includes a solenoid portion 30 that generates an electromagnetic force, and a pump portion 40 that operates by the electromagnetic force of the solenoid portion 30. The electromagnetic pump 20 is incorporated into a valve body as a portion of a hydraulic circuit for turning on and off a clutch or a brake provided in an automatic transmission mounted in an automobile, for example.

The solenoid portion 30 has a case 31 as a bottomed cylinder member on which an electromagnetic coil 32, a plunger 34 as a movable element, and a core 36 as a fixed element are disposed. Applying a current to the electromagnetic coil 32 forms a magnetic circuit in which magnetic flux circles the case 31, the plunger 34, and the core 36, whereby the plunger 34 is suctioned and presses out a shaft 38 that is in contact with a proximal end of the plunger 34.

The pump portion 40 includes: a hollow cylindrical cylinder 42 that is joined to the solenoid portion 30; the piston 50 that is slidably disposed inside the cylinder 42, and has a base end surface that is coaxial with and contacts a proximal end of the shaft 38 of the solenoid portion 30; a spring 46 that contacts a proximal end of the piston 50, and applies a biasing force in a direction opposite from the direction in which the solenoid portion 30 applies an electromagnetic force; an intake check valve 60 that supports the spring 46 from a side opposite from the proximal end surface of the piston 50, and allows the hydraulic oil to flow in the suctioning direction toward a pump chamber 41 and prohibits the hydraulic oil from flowing in the reverse direction; a discharge check valve 70 that is embedded in the piston 50, and allows the hydraulic oil to flow in the discharging direction from the pump chamber 41 and prohibits the hydraulic oil from flowing in the reverse direction; a strainer 47 that is disposed upstream of the intake check valve 60, and catches foreign matter included in the hydraulic oil that is suctioned toward the pump chamber 41; and a cylinder cover 48 that covers an opening portion 42a on a side of the cylinder 42 opposite from the solenoid portion 30 with the piston 50, the discharge check valve 70, the spring 46, the intake check valve 60, and the strainer 47 incorporated in that order from the opening portion 42a. Spiral grooves are formed in the circumferential direction on an inner circumferential surface of the cylinder cover 48 and an outer circumferential surface of the opening portion 42a of the cylinder 42. Threadedly fastening the cylinder cover 48 with the opening portion 42a of the cylinder 42 attaches the cylinder cover 48 to the opening portion 42a of the cylinder 42. Note that, in the pump portion 40, an intake port 49 for suctioning the hydraulic oil is formed at an axial center of the cylinder cover 48, and a discharge port 43 for discharging the suctioned hydraulic oil is formed in a side surface of the cylinder 42.

The piston 50 is formed from a cylindrical piston body 52, and a cylindrical shaft portion 54b that has an outer diameter smaller than the piston body 52 and an end surface that contacts the proximal end of the shaft 38 of the solenoid portion 30. The piston 50 moves in association with the shaft 38 of the solenoid portion 30 and reciprocates inside the cylinder 42. A cylindrical, bottomed hollow portion 52a that can accommodate the discharge check valve 70 is formed at an axial center of the piston 50. The hollow portion 52a of the piston 50 runs from a proximal end surface of the piston 50 to inside the piston body 52, and extends to partway inside the shaft portion 54. In addition, two through holes 54a, 54b that intersect at a 90-degree angle in the radial direction are formed in the shaft portion 54. The discharge port 43 is formed around the shaft portion 54, and the hollow portion 52a of the piston 50 is provided in communication with the discharge port 43 through the two through holes 54a, 54b.

The intake check valve 60 includes: a valve body 62 that is fitted by insertion to an inner circumferential surface of the opening portion 42a of the cylinder 42, formed therein with a bottomed hollow portion 62a, and formed with a center hole 62b that provides communication between the hollow portion 62a and the pump chamber 41 at an axial center of the bottom of the hollow portion 62a; a ball 64; a spring 66 that applies a biasing force to the ball 64; and a plug 68 that is fitted by insertion to an inner circumferential surface of the hollow portion 62a with the ball 64 and the spring 66 incorporated into the hollow portion 62a of the valve body 62.

FIG. 2 is a perspective view of the piston 50 and the intake check valve 60 inserted inside the cylinder 42, and FIG. 3 is an exterior view that shows the exterior of the valve body 62. As shown in the figures, the valve body 62 is formed from a stepped structure that includes a cylindrical base portion 63a and a truncated conical projection portion 63b that projects from a seat surface of the base portion 63a. On a circumferential edge portion of the seat surface, the base portion 63a has a ring-shaped surface that supports the spring 46. The height of the seat surface is adjusted to allow spring spacing for realizing a required biasing force. The projection portion 63b is formed so as to project inside the pump chamber 41, and the projecting height and diameter are adjusted such that the volume inside the pump chamber 41 becomes a volume for realizing a required discharge pressure. In other words, the valve body 62 adjusts the biasing force of the spring 46 and the volume of the pump chamber 41 using the base portion 63a and the projection portion 63b.

The hollow portion 62a formed inside the valve body 62 runs through an axial center inside the base portion 63a from a back surface of the base portion 63a, and extends to the vicinity of a proximal end inside the projection portion 63b, with the ball 64, the spring 66, and the plug 68 incorporated in that order inside the hollow portion 62a. The intake check valve 60 can thus be made compact because the axial length of the valve body 62 need only correspond to a length required for incorporating the ball 64, the spring 66, and the plug 68.

When a differential pressure (P1-P2) between a pressure P1 on the intake port 49 side and a pressure P2 on the pump chamber 41 side is equal to or greater than a predetermined pressure that overcomes the biasing force of the spring 66, the spring 66 contracts and causes the ball 64 to separate from the center hole 69 of the plug 68, thereby opening the intake check valve 60. When the differential pressure (P1-P2) described above is less than the predetermined pressure, the spring 66 elongates and causes the ball 64 to press against the center hole 69 of the plug 68, thereby blocking the center hole 69 and closing the intake check valve 60.

The discharge check valve 70 includes: a ball 74, a spring 76 that applies a biasing force to the ball 74; and a plug 78 as a ring-shaped member that has a center hole 79 with an inner diameter smaller than the outer diameter of the ball 74. The spring 76, the ball 74, and the plug 78 are incorporated in that order from an opening portion 52b of the hollow portion 52a of the piston 50, and fixed by a snap ring 79.

When a differential pressure (P2-P3) between the pressure P2 on the pump chamber 41 side and a pressure P3 on the discharge port 43 side is equal to or greater than a predetermined pressure that overcomes the biasing force of the spring 76, the spring 76 contracts and causes the ball 74 to separate from the center hole 79 of the plug 78, thereby opening the discharge check valve 70. When the differential pressure (P2-P3) described above is less than the predetermined pressure, the spring 76 elongates and causes the ball 74 to press against the center hole 79 of the plug 78, thereby blocking the center hole 79 and closing the discharge check valve 70.

In the cylinder 42, the pump chamber 41 is formed by a space that is surrounded by an inner wall 42b on which the piston body 52 slides, a surface of the piston body 52 on the spring 46 side, and a surface of the valve body 62 of the intake check valve 60 on the spring 46 side. In the pump chamber 41, when the piston 50 moves by the biasing force of the spring 46, the volume inside the pump chamber 41 increases and causes the intake check valve 60 to open and the discharge check valve 70 to close, thereby suctioning the hydraulic oil through the intake port 49. When the piston 50 moves by the electromagnetic force of the solenoid portion 30, the volume inside the pump chamber 41 decreases and causes the intake check valve 60 to close and the discharge check valve 70 to open, thereby discharging the suctioned hydraulic oil through the discharge port 43.

Also, the cylinder 42 is formed with the inner wall 42b on which the piston body 52 slides, and an inner wall 42c on which the shaft portion 54 slides. The inner wall 42b and the inner wall 42c are arranged in a stepped configuration, and the discharge port 43 is formed at a stepped section thereof. The stepped section forms a space that is surrounded by a ring-shaped surface of the stepped section between the piston body 52 and the shaft portion 54, and an outer circumferential surface of the shaft portion 54. Because the space is formed on the opposite side of the piston body 52 from the pump chamber 41, the volume of the space decreases when the volume of the pump chamber 41 increases, and the volume of the space increases when the volume of the pump chamber 41 decreases. At such times, the change in the volume of the space is smaller than the change in the volume of the pump chamber 41, because the surface area (pressure-receiving surface area) of the piston body 52 that receives pressure from the pump chamber 41 side is larger than the surface area (pressure-receiving surface area) of the piston body 52 that receives pressure from the discharge port 43 side. Therefore, the space functions as a second pump chamber 56. In other words, when the piston 50 moves by the electromagnetic force of the solenoid portion 30, an amount of hydraulic oil that corresponds to the difference in the amount that the volume of the pump chamber 41 decreases and the amount that the volume of the second pump chamber 56 increases is delivered from the pump chamber 41 to the second pump chamber 56 via the discharge check valve 70 and discharged through the discharge port 43. When the piston 50 moves by the biasing force of the spring 46, an amount of hydraulic oil that corresponds to the amount that the volume of the pump chamber 41 increases is suctioned through the intake port 49 into the pump chamber 41 via the intake check valve 60, while an amount of hydraulic oil that corresponds to the amount that the volume of the second pump chamber 56 decreases is discharged from the second pump chamber 56 through the discharge port 43. Accordingly, one reciprocal movement of the piston 50 discharges the hydraulic oil twice from the discharge port 43, which can reduce discharge variation and improve discharge performance.

According to the electromagnetic pump 20 of the embodiment described above, the valve body 62 of the intake check valve 60 is formed from a stepped structure that includes the cylindrical base portion 63a and the truncated conical projection portion 63b that projects from the seat surface of the base portion 63a. In addition, the valve body 62 of the intake check valve 60 is also formed such that the base portion 63a has the ring-shaped surface that supports the spring 46 on the circumferential edge portion of the seat surface, and the projection portion 63b projects inside the pump chamber 41. Therefore, the spring spacing can be adjusted by adjusting the height of the seat surface of the base portion 63a, and the volume inside the pump chamber 41 can be adjusted by adjusting the projecting height and diameter of the projection portion 63b. As a consequence, a simple structure can optimize the biasing force of the spring 46 and the volume of the pump chamber 41, and also further improve discharge performance.

Moreover, the hollow portion 62a formed inside the valve body 62 runs through the axial center inside the base portion 63a from the back surface of the base portion 63a, and extends to the vicinity of the proximal end inside the projection portion 63b, with the ball 64, the spring 66, and the plug 68 incorporated inside the hollow portion 62a. Therefore, the intake check valve 60 can be made more compact because the axial length of the valve body 62 need only correspond to the length required for incorporating the ball 64, the spring 66, and the plug 68.

In the electromagnetic pump 20 of the embodiment, the discharge check valve 70 is embedded in the piston 50. However, the discharge check valve 70 may not be embedded in the piston 50, and may be incorporated into a valve body outside the cylinder 42, for example.

In the electromagnetic pump 20 of the embodiment, the projection portion 63b of the valve body 62 has a truncated conical shape. However, the present invention is not limited to this example, and the projection portion 63b may have any shape, such as a cylindrical shape, provided that the projection portion 63b projects inside the pump chamber 41.

In the electromagnetic pump 20 of the embodiment, the hollow portion 62a of the valve body 62 runs through the inside of the base portion 63a from the back surface of the base portion 63a, and extends to the vicinity of the proximal end inside the projection portion 63b. However, the hollow portion 62a may not extend to inside the projection portion 63b, In such case, the height of the base portion 63a may be increased to incorporate the ball 64, the spring 66, and the plug 68 in the hollow portion.

The electromagnetic pump 20 of the embodiment is configured as a type of electromagnetic pump in which one reciprocal movement of the piston 50 discharges the hydraulic oil twice from the discharge port 43. However, the present invention is not limited to this example. The electromagnetic pump 20 may be any type of electromagnetic pump provided that the electromagnetic pump is capable of discharging the hydraulic oil in association with the reciprocal movement of the piston. Such examples include an electromagnetic pump that suctions the hydraulic oil through the intake port into the pump chamber when the piston is forwardly moved by the electromagnetic force from the solenoid portion, and discharges the hydraulic oil inside the pump chamber from the discharge port when the piston is backwardly moved by the biasing force of the spring, as well as an electromagnetic pump that suctions the hydraulic oil through the intake port into the pump chamber when the piston is backwardly moved by the biasing force of the spring, and discharges the hydraulic oil inside the pump chamber from the discharge port when the piston is forwardly moved by the electromagnetic force from the solenoid portion.

The electromagnetic pump 20 of the embodiment is used to supply a hydraulic pressure for turning on and off a clutch or a brake of an automatic transmission mounted in an automobile. However, the present invention is not limited to this example, and the electromagnetic pump 20 may be used in any system that transports fuel, transports lubricating fluid, or the like.

Here, the correspondence relation will be described between main elements in the embodiment and main elements of the invention as listed in the Summary of the Invention. In the embodiment, the cylinder 42 corresponds to a “cylinder”; the piston 50 to a “piston”; the solenoid portion 30 to an “electromagnetic portion”; the spring 46 to a “biasing member”; the valve body 62 to a “support member”; the ball 64, the spring 66, and the plug 68 that constitute the intake check valve 60 to an “intake on-off valve”; the discharge check valve 70 to a “discharge on-off valve”; the base portion 63a of the valve body 62 to a “support portion”; and the projection portion 63b to a “projection portion”. Note that with regard to the correspondence relation between the main elements of the embodiment and the main elements of the invention as listed in the Summary of the Invention, the embodiment is only an example for giving a specific description of a best mode for carrying out the invention explained in the Summary of the Invention. This correspondence relation does not limit the elements of the invention as described in the Summary of the Invention. In other words, any interpretation of the invention described in the Summary of the Invention shall be based on the description therein; the embodiment is merely one specific example of the invention described in the Summary of the Invention.

The above embodiment was used to describe a mode for carrying out the present invention. However, the present invention is not particularly limited to such an example, and may obviously be carried out in various embodiments without departing from the scope of the present invention.

The present invention may be used in the manufacturing industry of an electromagnetic pump, and the like.

Claims

1. An electromagnetic pump comprising:

a cylinder;

a piston that can reciprocate inside the cylinder;

an electromagnetic portion that forwardly moves the piston;

a biasing member that backwardly moves the piston;

a support member that supports the biasing member and, with the cylinder and the piston, defines a pump chamber;

an intake on-off valve that is incorporated into the support member, and allows a hydraulic fluid to move from an intake port to the pump chamber and prohibits reverse movement of the hydraulic fluid; and

a discharge on-off valve that allows the hydraulic fluid to move from the pump chamber to a discharge port and prohibits reverse movement of the hydraulic fluid, wherein

the support member includes therein a bottomed hollow portion accommodating from the intake port side at least a portion of the intake on-off valve, and a communication hole providing communication between a bottom portion of the hollow portion on the pump chamber side and the pump chamber, and

the support member is formed with a support portion that supports the biasing member, and a projection portion that is in communication with the communication hole and projects from the support portion toward the piston side.

2. The electromagnetic pump according to claim 1, wherein a diameter of the projection portion on the piston side is formed smaller than a diameter of the projection portion on the support portion side.

3. The electromagnetic pump according to claim 2, wherein the projection portion is formed into a truncated conical shape.

4. The electromagnetic pump according to claim 1, wherein the hydraulic fluid is discharged by the biasing member backwardly moving the piston.

5. The electromagnetic pump according to claim 1, wherein the hollow portion of the support member is formed such that the bottom portion is more toward the piston side than a support surface of the support portion.