ELECTROMAGNETIC PUMP

Abstract

An electromagnetic pump including a pump portion that includes a cylinder that is formed with an intake port and a discharge port that are in communication with a flow passage of a fluid pressure circuit, a pin groove, and a piston that through a reciprocal movement inside the cylinder suctions a fluid from the intake port and discharges the fluid from the discharge port; and an electromagnetic portion that reciprocates the piston. Inserting the pump portion inside a fluid pressure circuit with the electromagnetic portion externally exposed from the fluid pressure circuit, and inserting a pin from outside into the pin groove incorporates the electromagnetic pump inside a fluid pressure circuit, and the pin groove is formed at a position farther from an electromagnetic portion side than the discharge port.

Description

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2011-068805 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 pump portion that includes a cylinder that is formed with an intake port and a discharge port that are in communication with a flow passage of a fluid pressure circuit, a pin groove, and a piston that through a reciprocal movement inside the cylinder suctions a fluid from the intake port and discharges the fluid from the discharge port; and an electromagnetic portion that reciprocates the piston, wherein inserting the pump portion inside the fluid pressure circuit with the electromagnetic portion externally exposed from the fluid pressure circuit, and inserting a pin from outside into the pin groove incorporates the electromagnetic pump inside the fluid pressure circuit.

DESCRIPTION OF THE RELATED ART

As an electromagnetic pump of this type, related art has proposed an electromagnetic pump that is incorporated into a hydraulic circuit (valve body) of an automatic transmission mounted in an automobile that has an idling stop function (e.g., see Japanese Patent Application Publication No. JP-A-2010-181010). The electromagnetic pump is used to maintain a clutch of the automatic transmission to a stroke end pressure while an engine is stopped.

SUMMARY OF THE INVENTION

The electromagnetic pump described above is designed with a relatively high discharge performance because of the need to apply a hydraulic pressure to an oil chamber of the clutch. Hydraulic fluid is thus prone to leak from the discharge port, and the discharge performance of the electromagnetic pump may suffer as a consequence.

An electromagnetic pump of the present invention secures discharge performance by suppressing hydraulic fluid leakage.

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

An electromagnetic pump according to the present invention includes: a pump portion that includes a cylinder that is formed with an intake port and a discharge port that are in communication with a flow passage of a fluid pressure circuit, a pin groove, and a piston that through a reciprocal movement inside the cylinder suctions a fluid from the intake port and discharges the fluid from the discharge port; and an electromagnetic portion that reciprocates the piston. In the electromagnetic pump, inserting the pump portion inside the fluid pressure circuit with the electromagnetic portion externally exposed from the fluid pressure circuit, and inserting a pin from outside into the pin groove incorporates the electromagnetic pump inside the fluid pressure circuit. In addition, the pin groove is formed at a position farther from an electromagnetic portion side than the discharge port.

According to the present invention, the electromagnetic pump includes: a pump portion that includes a cylinder that is formed with an intake port and a discharge port that are in communication with a flow passage of a fluid pressure circuit, a pin groove, and a piston that through a reciprocal movement inside the cylinder suctions a fluid from the intake port and discharges the fluid from the discharge port; and an electromagnetic portion that reciprocates the piston. In the electromagnetic pump, inserting the pump portion inside the fluid pressure circuit with the electromagnetic portion externally exposed from the fluid pressure circuit, and inserting a pin from outside into the pin groove incorporates the electromagnetic pump inside the fluid pressure circuit. In addition, the pin groove is formed at a position farther from an electromagnetic portion side than the discharge port. Since there is no leakage path from the discharge port through the pin groove to outside, hydraulic fluid leakage can thus be suppressed. As a consequence, the discharge performance of the electromagnetic pump can be secured.

In the electromagnetic pump described above, the intake port may be formed on an end surface of the cylinder on a side opposite from the electromagnetic portion side, the discharge port may be formed in a side surface of the cylinder, and the pin groove may be formed on the side surface of the cylinder.

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 an exterior view that shows the exterior of the electromagnetic pump 20 of the embodiment;

FIG. 3 is a cross-sectional view that shows a cross section A-A of the electromagnetic pump 20 in FIG. 2; and

FIG. 4 is an explanatory diagram that shows how the electromagnetic pump 20 of the embodiment is attached to a valve body 80.

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 80 formed with a plurality of oil passages 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. The plug 68 is formed as a ring-shaped member that includes a center hole 69 with an inner diameter smaller than the outer diameter of the ball 64. The ball 64 biased by the spring 66 is pressed against the center hole 69.

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.

FIG. 2 shows the exterior of the electromagnetic pump 20 of the embodiment. FIG. 3 shows a cross section A-A of the electromagnetic pump 20 in FIG. 2. FIG. 4 shows how the electromagnetic pump 20 of the embodiment is incorporated into the valve body 80. As shown in the figures, the side surface of the cylinder 42 of the electromagnetic pump 20 is formed with an arc-shaped pin groove 44 at a position farther from the solenoid portion 30 than a position at which the discharge port 43 is formed. In the electromagnetic pump 20 of the embodiment, the pump portion 40 is inserted into the valve body 80 with the solenoid portion 30 exposed, and a pin 84 is passed through a pin hole 82 formed in the valve body 80 such that the pin 84 engages with the pin groove 44 inside the valve body 80 to fix the pump portion 40 to the valve body 80. The following assumes that the pin groove 44 is formed at a position on the cylinder 42 closer to the solenoid portion 30 than a position at which the discharge port 43 is formed. Since the discharge port 43 is under a high pressure due to the operation of the electromagnetic pump 20, the hydraulic oil tends to leak from the discharge port 43 to a gap between the cylinder 42 and the valve body 80. The hydraulic oil leakage may therefore reach the solenoid portion 30 side via the pin groove 44, and in such case, may result in a loss of hydraulic pressure. However, in the embodiment, the pin groove 44 is formed at a position farther from the solenoid portion 30 than a position at which the discharge port 43 is formed so that such a failure does not occur.

According to the electromagnetic pump 20 of the embodiment described above, the pump portion 40 is inserted into the valve body 80 with the solenoid portion 30 exposed, and the pin 84 is passed through the pin hole 82 formed in the valve body 80 such that the pin 84 engages with the pin groove 44 inside the valve body 80 to fix the electromagnetic pump 20. The pin groove 44 is formed at a position farther from the solenoid portion 30 than a position at which the discharge port 43 is formed. Therefore, even if the hydraulic oil leaks from the discharge port 43 to the gap between the cylinder 42 and the valve body 80, the hydraulic oil is much less likely to reach the solenoid portion 30 side, and a loss of hydraulic pressure can thus be prevented.

In the electromagnetic pump 20 of the embodiment, the intake check valve 60 and the discharge check valve 70 are embedded inside the cylinder 42. However, one or both of the intake check valve 60 and the discharge check valve 70 may be disposed outside the cylinder 42.

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 hydraulic circuit that includes the valve body 80 corresponds to a “fluid pressure circuit”; the cylinder 42 to a “cylinder”; the piston 50 to a “piston”; the solenoid portion 30 to an “electromagnetic portion”; and the pin groove 44 to a “pin groove”. 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 pump portion that includes a cylinder that is formed with an intake port and a discharge port that are in communication with a flow passage of a fluid pressure circuit, a pin groove, and a piston that through a reciprocal movement inside the cylinder suctions a fluid from the intake port and discharges the fluid from the discharge port; and

an electromagnetic portion that reciprocates the piston, wherein

inserting the pump portion inside the fluid pressure circuit with the electromagnetic portion externally exposed from the fluid pressure circuit, and inserting a pin from outside into the pin groove incorporates the electromagnetic pump inside the fluid pressure circuit, and

the pin groove is formed at a position farther from an electromagnetic portion side than the discharge port.

2. The electromagnetic pump according to claim 1, wherein

the intake port is formed on an end surface of the cylinder on a side opposite from the electromagnetic portion side,

the discharge port is formed in a side surface of the cylinder, and

the pin groove is formed on the side surface of the cylinder.