JP2009236269A - Relief valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce hysteresis of a relief valve due to influence of dynamic pressure. <P>SOLUTION: The upstream side of the valve element 50 of the relief valve other than a portion abutting on a valve seat 42 is formed in a conical shape. Thereby, a change in a direction of a fluid streamline A in the vicinity of the stagnation point of the valve element 50 becomes small in comparison with a spherical valve element. An average flow rate in the vicinity of the stagnation point when the valve is opened is thereby increased to reduce the dynamic pressure. As a result, hysteresis is reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a relief valve that adjusts a fluid pressure in a main passage to a predetermined pressure or less, and is suitable for, for example, a relief valve used in a vehicle fuel system.

  A relief valve is generally built in a fuel transfer pump mounted in a fuel tank of a vehicle. The relief valve includes a spherical valve body that opens and closes a relief passage and a spring that biases the valve body in a valve closing direction (see, for example, Patent Document 1).

The valve opening pressure of the relief valve must be higher than the system pressure of the vehicle and set to be as low as possible for protecting the piping. Generally, the relief valve has a pressure lower than the vehicle system pressure (about 300 to 400 kPa). The valve opening pressure is set to be 50 to 100 kPa higher.
JP-A-5-71436

  By the way, the valve opening pressure of the relief valve is almost determined by the static pressure in the pipe. On the other hand, once the relief valve is opened, the dynamic pressure of the fuel flowing out is applied to the valve body, so that it has a hysteresis characteristic that it is difficult to close once the relief valve is opened.

  Therefore, when the valve opening pressure of the relief valve is set low, that is, when the difference between the vehicle system pressure and the valve opening pressure of the relief valve is set small, the static pressure in the pipe is opened after the relief valve is opened. If the pressure does not drop below the vehicle system pressure, the relief valve may not close. On the other hand, when the valve opening pressure of the relief valve is set to be high in consideration of hysteresis, that is, when the difference between the vehicle system pressure and the valve opening pressure of the relief valve is set large, a filter or When the pipe is blocked, the pressure in the pipe rises too much, causing a problem of damaging the pump and the pipe.

  The present invention has been made in view of the above points, and an object thereof is to reduce the hysteresis of a relief valve due to the influence of dynamic pressure.

  In order to achieve the above object, according to the first aspect of the present invention, the main passage is arranged in the relief passage (41) branched from the main passage (30, 40) and allowing the fluid in the main passage (30, 40) to escape. In the relief valve for adjusting the fluid pressure in the (30, 40) to a predetermined pressure or less, the fluid pressure in the main passage (30, 40) is urged to open the relief passage (41), and the relief passage ( 41) a valve body (50) that opens and closes the relief passage (41) in contact with and away from the valve seat (42) formed therein, and a spring (51) that biases the valve body (50) in the valve closing direction. The valve body (50) is characterized in that the upstream side of the portion that contacts the valve seat (42) is conical.

  According to this, the change in the direction of the fluid stream line in the vicinity of the stagnation point of the valve body (50) is smaller than that in the case where the valve body is spherical. For this reason, the average flow velocity in the vicinity of the stagnation point at the time of valve opening becomes high and the dynamic pressure becomes small, and as a result, the hysteresis becomes small.

  As in the second aspect of the invention, the upstream tip (500a) of the valve body (50) can be a spherical surface.

  According to a third aspect of the invention, in the relief valve according to the second aspect, the diameter of the upstream relief passage hole (410) located upstream of the valve seat (42) in the relief passage (41) is D. When the radius of curvature of the spherical surface of the upstream tip (500a) of the valve body (50) is R, R ≦ D / 2.

  When the valve body is spherical, the diameter of the valve body is necessarily larger than the diameter D of the upstream relief passage hole (410), and Rb> D / 2.

  On the other hand, when the valve body (50) has a conical shape, the radius of curvature R of the spherical surface of the upstream end portion (500a) of the valve body (50) can be R ≦ D / 2. By setting R ≦ D / 2, the change in the direction of the fluid flow line in the vicinity of the stagnation point of the valve body (50) can be reliably reduced as compared with the case where the valve body is spherical, and thus hysteresis Can be reduced.

  In addition, the code | symbol in the bracket | parenthesis of each means described in a claim and this column shows the correspondence with the specific means as described in embodiment mentioned later.

  An embodiment of the present invention will be described. FIG. 1 is a sectional view of a pump using a relief valve according to an embodiment, and FIG. 2 is an enlarged sectional view of the relief valve of FIG.

  This pump is housed in a fuel tank of a vehicle or the like, and is used as a fuel pump that supplies fuel sucked from the fuel tank to the engine side. As shown in FIG. 1, the pump includes a pump unit 1 that boosts and discharges fuel, and a motor 2 that rotationally drives an impeller 12 of the pump unit 1. The pump unit 1 and the motor 2 are cylindrical. It is accommodated in the housing 3.

  The motor 2 is a DC motor, and a permanent magnet 20 is annularly arranged on the inner peripheral wall of the housing 3, and an armature 21 is arranged concentrically on the inner peripheral side of the permanent magnet 20. The shaft 22 of the armature 21 is rotatably held by a bearing member 24 supported by the bearing holder 23 and a bearing member 24 supported by the casing 11 of the pump unit 1. A commutator 25 is disposed at the end of the armature 21 on the side opposite to the pump portion, and power is supplied from a power source (not shown) to the coil of the armature 21 via the terminal 26, a brush (not shown), and the commutator 25. Supplied.

  The pump unit 1 includes a cover 10, a casing 11, an impeller 12, and the like. The casing 11 is disposed closer to the motor 2 than the cover 10, and a bearing member 24 is inserted in the central portion in the radial direction. A space is formed by the cover 10 and the casing 11, and a disk-shaped impeller 12 is rotatably accommodated in the space. A shaft 22 of an armature 21 (see FIG. 1) is inserted in the central portion of the impeller 12 in the radial direction, and the impeller 12 is rotationally driven by the motor 2.

  As the impeller 12 rotates, the fuel in the fuel tank is sucked from the suction passage 101 of the cover 10, further pressurized, and discharged from the discharge passage (not shown) of the casing 11 to the space 30 in the housing 3. The

  A resin end cover 4 is disposed on the side of the housing 3 opposite to the pump portion. The end cover 4 includes a discharge port 40 connected to the engine, and the fuel pressurized by the pump 1 and discharged into the space 30 in the housing 3 is supplied to the engine via the discharge port 40 and a fuel pipe (not shown). It has become so. A check valve (not shown) is disposed in the end cover 4 in order to prevent the backflow of fuel discharged from the discharge port 40. The space 30 and the discharge port 40 constitute a main passage of the present invention.

  As shown in FIGS. 1 and 2, the end cover 4 is formed with a relief passage 41 that branches from the space 30 and allows the fuel in the space 30 to escape into the fuel tank. In the middle of the relief passage 41, a valve seat 42 is formed in which a valve body 50 of a relief valve 5 described later contacts and separates. The relief passage 41 is a cylindrical upstream relief passage hole 410 located on the upstream side of the valve seat 42 and a cylindrical shape having a diameter larger than that of the upstream relief passage hole 410 and located on the downstream side of the valve seat 42. It consists of a downstream relief passage hole 411. In the following description, the flow line of the fuel flowing toward the valve body 50 in the downstream relief passage hole 411 when the relief valve 5 is opened is referred to as a relief fuel flow line A. Incidentally, the relief fuel flow line A is parallel to the axis of the upstream relief passage hole 410.

  The relief passage 41 is provided with a relief valve 5 that adjusts the fuel pressure in the space 30 to a predetermined pressure or less. The relief valve 5 is urged in the direction to open the relief passage 41 by the fuel pressure in the space 30, and the valve body 50 that contacts and separates from the valve seat 42 to open and close the relief passage 41, and closes the valve body 50. And a spring 51 biasing in the direction.

  The valve body 50 has a shape in which two cones are combined. Specifically, the upstream valve body 500 positioned upstream of the fuel flow has a conical shape whose diameter expands along the fuel flow, and the downstream valve body 501 positioned downstream of the fuel flow A conical shape whose diameter decreases along the flow. The upstream valve body 500 only needs to be conical on the upstream side of at least the portion that contacts the valve seat 42.

  The upstream tip 500a of the upstream valve body 500 is a spherical surface. Here, when the diameter of the upstream relief passage hole 410 is D and the radius of curvature of the spherical surface of the upstream tip portion 500a of the upstream valve body 500 is R, R ≦ D / 2. Desirably, R ≦ D / 4.

  Next, the operation of the pump configured as described above will be described. When electric power is supplied to the coil of the armature 21, the armature 21 is rotationally driven, and the impeller 12 fixed to the shaft 22 of the armature 21 is also rotationally driven. As the impeller 12 rotates, the fuel in the fuel tank is sucked from the suction passage 101 and is pressurized by the action of a plurality of blade grooves (not shown) of the impeller 12. The pressurized fuel is discharged into the space 30 in the housing 3 and supplied to the engine through the discharge port 40 and a fuel pipe (not shown).

  At this time, when the fuel pressure (static pressure) in the space 30 reaches a predetermined pressure, the valve body 50 is moved in the valve opening direction against the urging force of the spring 51 by the fuel pressure, and the valve body 50 is moved to the valve seat 42. Relief passage 41 is opened away from. As a result, the fuel in the space 30 is released into the fuel tank via the relief passage 41, so that the fuel pressure in the space 30 decreases.

  As described above, once the relief valve 5 is opened, the dynamic pressure of the fuel released into the fuel tank is applied to the valve body 50, and thus hysteresis occurs. However, as described below, in the relief valve 5 of the present embodiment, as described below. The hysteresis can be reduced.

Here, the dynamic pressure q is given by q = 1/2 · ρ · V ² . Here, ρ is the fuel density and V is the flow velocity. Further, when the flow velocity in the upstream relief passage hole 410 is V1, and the average flow velocity in the predetermined projected area near the stagnation point of the valve body 50 is V2, the flow velocity V is given by V = V1−V2.

  When the upstream valve body 500 is formed in a conical shape as in the present embodiment, the change in the direction of the relief fuel stream line A in the vicinity of the stagnation point is a conventional relief valve (that is, the valve body 50 is spherical). Smaller than. For this reason, in the relief valve 5 of this embodiment, the average flow velocity V2 in the vicinity of the stagnation point is higher than that of the conventional relief valve, and the dynamic pressure is reduced.

  By the way, when the valve body 50 is spherical, the diameter of the valve body 50 is inevitably larger than the diameter D of the upstream relief passage 41 hole, and if the radius of curvature of the spherical valve body 50 is Rb, then Rb> D / 2.

  On the other hand, when the valve body 50 has a conical shape, the radius of curvature R of the spherical surface of the upstream end portion of the valve body 50 can be R ≦ D / 2. By setting R ≦ D / 2, the change in the direction of the relief fuel flow line A in the vicinity of the stagnation point can be surely reduced as compared with the case where the valve body 50 is spherical, and thus the hysteresis is reduced. be able to.

  In the above embodiment, the downstream valve body portion 501 of the valve body 50 is conical, but the downstream valve body portion 501 of the valve body 50 may be hemispherical as in the modification shown in FIG. .

(Other embodiments)
Although the example which adjusts the pressure of fuel was shown in the said embodiment, this invention is applicable also to the relief valve which adjusts the pressure of fluids other than a fuel.

It is sectional drawing of the pump using the relief valve which concerns on one Embodiment of this invention. It is an expanded sectional view of the relief valve of FIG. It is sectional drawing of the principal part which shows the modification of the relief valve which concerns on one Embodiment.

Explanation of symbols

30 spaces (main passage)
40 Discharge port 40 (main passage)
41 Relief passage 42 Valve seat 50 Valve body 51 Spring

Claims (3)

It is arranged in a relief passage (41) that branches off from the main passage (30, 40) and allows the fluid in the main passage (30, 40) to escape, so that the fluid pressure in the main passage (30, 40) is below a predetermined pressure. In the relief valve to be adjusted,
The relief pressure (41) is urged by the fluid pressure in the main passage (30, 40) to open, and the valve seat (42) formed in the relief passage (41) is brought into contact with and separated from the valve seat (42). A valve body (50) for opening and closing the relief passage (41) and a spring (51) for urging the valve body (50) toward the valve closing direction are provided, and the valve body (50) includes the valve seat (42). A relief valve having a conical shape on the upstream side of the portion in contact with the contact portion.   The relief valve according to claim 1, wherein the upstream end (500a) of the valve body (50) has a spherical surface.   The diameter of the upstream relief passage hole (410) located on the upstream side of the valve seat (42) in the relief passage (41) is D, and the spherical surface of the upstream tip (500a) in the valve body (50). The relief valve according to claim 2, wherein R ≦ D / 2, where R is a curvature radius.

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