JP6538414B2 - Differential pressure detection device and filtration device - Google Patents

Description

  The present invention relates to a differential pressure detection device and a filtration device.

  According to Patent Document 1, when the filter element is incorporated in the hydraulic circuit, a pressure difference between the pressure inside the inner cylindrical member and the pressure in the space between the storage tank and the filter element is applied to the upper end support plate member. It is disclosed that a differential pressure detecting device for detecting is provided.

JP, 2013-252512, A

  In the invention described in Patent Document 1, a reed switch is used in the differential pressure detection device. FIG. 7 is a diagram schematically showing a conventional differential pressure detection device 100. As shown in FIG. Although FIG. 7 is a cross-sectional view, hatching of a plurality of parts including the case 101 is omitted for the explanation of the operation and the like.

  In the differential pressure detection device 100, in the case 101, a reed switch 102 and a spool 103 provided with a magnet 104 are provided. The reed switch 102 is provided along a plane (xy plane) orthogonal to the central axis A of the case 101.

  When the two reed pieces inside the reed switch 102 are magnetized by the magnetic field of the magnet 104, the reed switch 102 is in a state where the internal circuit is closed (hereinafter referred to as ON state). When the spool 103 is separated from the reed switch 102, the reed switch 102 is switched from the ON state to the open state (hereinafter referred to as the OFF state) of the internal circuit. In FIG. 7, when the reed switch 102 is in the ON state, the position of the magnetic field of a predetermined strength by the magnet 104 is within the range of the ON region S of the reed switch 102 (see the dashed dotted line and hatching in FIG. 7). Is shown as a case where lines (hereinafter referred to as magnetic lines of force M) indicating.

  The magnetic force of the magnet 104 is biased due to variations in the manufacturing process. For example, in the magnet 104, the magnetic force on the right side is stronger than the magnetic force on the left side in FIG. Therefore, as the magnet 104 rotates, the position of the magnetic force line M in the z direction changes. Therefore, in the conventional differential pressure detection apparatus 100, an error in differential pressure detection may increase, that is, detection of the differential pressure may not be stable.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a differential pressure detection device and a filtration device capable of stabilizing detection of differential pressure.

  In order to solve the above problems, a differential pressure detection device according to the present invention is, for example, a case having a substantially cylindrical shape, and a substantially cylindrical hole having a central axis substantially parallel to a central axis of the case is formed. A case, a substantially cylindrical spool slidably provided inside the hole, a first space being a low pressure side space, and a second space being a high pressure side space; And a substantially cylindrical reed switch provided on the opposite side of the spool to the inside of the case with the bottom surface of the hole interposed therebetween, wherein the central axis is substantially the same as the central axis of the case. A reed switch provided in parallel, an elastic member biasing the spool toward the second space from the first space, and a surface facing the bottom of the hole of the spool On the central axis of the reed switch Comprising a magnet kicked, and the case and the spool, characterized by having a detent mechanism for the spool to prevent rotation relative to the case.

  According to the differential pressure detection device of the present invention, the rotation stop mechanism does not rotate the spool with respect to the case. Thereby, detection of differential pressure can be stabilized.

  The spool may have a first radius and a second radius larger than the first radius around the central axis of the spool at the position where the magnet is provided. By using such a rotation stop mechanism, a highly effective rotation stop mechanism can be obtained with a simple configuration.

  Here, the hole may be a first hole formed to have a first diameter and a first depth, a second diameter which is a diameter larger than the first diameter, and a first depth shallower than the first depth. A second hole formed at a depth of 2; a central axis of the second hole substantially coincides with a central axis of the case; and a central axis of the first hole is the case The spool is substantially identical to the first diameter and a flange portion having a diameter substantially the same as the second diameter, and the central axis of the flange portion And the tip portion whose central axis is offset by the first distance. By using such a rotation stop mechanism, a highly effective rotation stop mechanism can be obtained with a simple configuration.

  Here, the case is formed with a hole communicating the first hole with the outside of the case, and the hole is formed by interposing the central axis of the case and the central axis of the first hole It may be formed on the side opposite to the side deviated by the first distance. As a result, the operation of the spool can be stabilized without deformation of the case.

  Moreover, the filtration apparatus which concerns on this invention has these differential pressure detection apparatuses, for example. Here, the upstream side of the filter may communicate with one of the first space and the second space, and the downstream side of the filter may communicate with the other.

  According to the present invention, differential pressure detection can be stabilized.

FIG. 1 is a schematic view of a filtration device 1 according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of a head 4; FIG. 5 is a cross-sectional view of an indicator 5; It is a perspective view which shows the outline of the spool. It is sectional drawing of the indicator 5A used with the filtration apparatus in 2nd Embodiment. It is a perspective view showing the outline of spool 54A used with indicator 5A. It is a figure which shows the outline of the conventional differential pressure detection apparatus 100. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First Embodiment
FIG. 1 is a schematic view of a filtration device 1. The filtering device 1 removes dust and the like contained in a liquid such as oil and water using a filter, and is incorporated in a hydraulic circuit such as a heavy machine provided with a hydraulic actuator, for example. Hydraulic fluid is flowing in the hydraulic circuit.

  The filtration device 1 mainly includes a housing 2, a filter element 3, a head 4, an indicator 5 and a drain 6.

  The housing 2 is a substantially bottomed cylindrical member whose one end is substantially closed and the other end is opened. A drain 6 is provided at the lower end of the housing 2. Note that providing the drain 6 is not essential.

  The opening of the housing 2 is attached to the head 4. The head 4 is provided with an indicator 5. The indicator 5 is provided with a lamp not shown. The indicator 5 displays ON / OFF of the internal reed switch 53 (described in detail later) by turning on / off the lamp. When the opening of the housing 2 is attached to the head 4, the filter element 3 attached to the head 4 is accommodated inside the housing 2.

  The filter element 3 mainly includes an inner cylinder 11, a filter medium 12, and plates 13 and 14 provided at both ends of the filter medium 12.

  The inner cylinder 11 is a substantially hollow cylindrical member having an opening at both ends. The inner cylinder 11 is formed using a material (for example, resin or metal) having high corrosion resistance.

  The filter medium 12 has a substantially hollow cylindrical shape having a thickness in the radial direction. The filter medium 12 is formed by folding sheet-like filter paper using synthetic resin, paper or the like, connecting both ends of the folded filter paper, and rolling it into a cylindrical shape.

  The plate 13 is provided at one end of the filter medium 12 and the plate 14 is provided at the other end. The plate 13 and the plate 14 are members having a substantially cylindrical shape with a bottom, and are formed using a material (for example, resin or metal) having high corrosion resistance.

  The plate 13 is provided on the upper end of the filter medium 12. A central cylinder 42 (described in detail later) of the head 4 is inserted into the plate 13. A seal member 22 (e.g., an O-ring) is provided between the plate 13 and the central cylinder 42. The seal member 22 seals the liquid between the plate 13 and the central cylinder 42 so as not to leak to the outside. Further, since the inner cylinder 11 is provided on the plate 13, when the central cylinder 42 is inserted into the plate 13, the internal space of the inner cylinder 11 communicates with the central cylinder 42.

  The head 4 mainly has a main body 41, a central cylinder 42, an inflow passage 43, an outflow passage 44, and a mounting hole 45.

  The main body 41 is a member having a substantially bottomed cylindrical shape, and is made of, for example, a material having high corrosion resistance (for example, formed of metal. An external thread 41a is formed on the outer periphery near the opening end of the main body 41. When the portion 41 a is screwed to the female screw portion 2 a (see FIG. 1) formed on the inner periphery of the housing 2, the head 4 is attached to the housing 2.

  A seal member 21 (e.g., an O-ring) is provided between the housing 2 and the head 4. The sealing member 21 seals the liquid from between the housing 2 and the head 4 so as not to leak to the outside.

  The central cylinder 42 is a substantially cylindrical member and is integrally formed with the main body 41. The central cylinder 42 protrudes from the substantially central bottom surface of the main body 41 in the same direction as the side surface of the main body 41. The central cylinder 42 is inserted into the hollow portion of the plate 13.

  A space (a space outside the central cylinder 42) S <b> 1 formed by the side surface of the main body 41 and the central cylinder 42 communicates with the inflow path 43. Further, the space S2 inside the central cylinder 42 communicates with the outflow passage 44.

  The hydraulic oil L1 of the hydraulic oil to be filtered is supplied to the filter device 1 through the inflow passage 43. The hydraulic oil L 1 flows into the housing 2 and is then filtered by the filter medium 12 and flows out to the inside of the inner cylinder 11. Further, the filtered hydraulic oil L 2 which has flowed out to the inside of the inner cylinder 11 is discharged from the outflow passage 44 to the outside of the filter device 1.

  The mounting hole 45 is formed in the vicinity of the bottom surface of the main body 41. The mounting hole 45 is provided with an indicator 5. The attachment of the indicator 5 will be described with reference to FIG.

  FIG. 2 is a cross-sectional view of the head 4. The mounting hole 45 has an opening on the side surface of the main body 41, and the depth d thereof is equal to or greater than the radius r of the bottom surface of the main body 41. A female screw 45 a is formed on the side surface of the mounting hole 45. When the male screw 51e (described in detail later) formed on the indicator 5 is screwed into the female screw 45a, the indicator 5 is attached to the head 4.

  Sealing members 23 and 24 (for example, an O-ring) are provided between the mounting hole 45 and the indicator 5. The sealing members 23 and 24 seal the liquid from between the mounting hole 45 and the indicator 5 so as not to leak to the outside.

  The depth d of the mounting hole 45 is equal to or greater than the radius r of the bottom surface of the main body 41, and the vicinity of the bottom of the mounting hole 45 is communicated with the outflow passage 44, that is, the space S2. Since the bottom of the indicator 5 has an opening, the space S2 communicates with the hole 512b (described in detail later) inside the indicator 5.

  The female screw 45 a of the mounting hole 45 communicates with the space S 1 through the hole 46. The space S1 communicates with a hole 511b (described in detail later) inside the indicator 5 through a hole 51d (described in detail later) formed in the indicator 5.

  Next, the indicator 5 will be described in detail. The indicator 5 corresponds to the differential pressure detection device of the present invention. FIG. 3 is a cross-sectional view of the indicator 5. In FIG. 3, hatching of a plurality of parts is omitted to make the drawing easy to see.

  The indicator 5 mainly includes a case 51, a reed switch assembly 52, a reed switch 53, a spool 54, a magnet 55, and a spring 56.

  The case 51 has a substantially cylindrical shape, and holes 51a and 51b are formed at both ends. Each of the holes 51a and 51b has a substantially cylindrical shape. The bottom surfaces of the holes 51a and 51b face each other.

  The hole 51 a is formed at the end on the + z side of the case 51. The reed switch assembly 52 is provided in the hole 51a. An internal thread portion 51c is formed inside the hole 51a.

  The hole 51 b is formed at the end on the −z side of the case 51. A spool 54 is provided in the hole 51b.

  The holes 51b mainly include a hole 511b and a hole 512b. The diameter of the hole 512b is larger than the diameter of the hole 511b.

  The central axis of the hole 512 b coincides with the central axis A 1 of the case 51. The central axis A2 of the hole 511b is separated from the central axis of the hole 512b (the central axis A1 of the case 51) by a distance d (offset). The central axis A1 and the central axis A2 are substantially parallel.

  The hole 51d is formed on the opposite side to the side where the central axis A2 is offset from the central axis A1 across the central axis A1. In FIG. 3, the central axis A2 is offset from the central axis A1 in the + x direction, and the hole 51d is formed on the -x side of the hole 511b. The thickness of the case 51 on the + x side of the hole 511b is thinner than the −x side of the hole 511b because the central axis A2 is offset from the central axis A1 in the + x direction. Therefore, in order to stabilize the operation of the spool 54 without deforming the case 51, it is desirable to form the hole 51d on the -x side in FIG.

  The reed switch assembly 52 has a substantially cylindrical shape, and a male screw 52a is formed around the periphery. By screwing the male screw portion 52a to the female screw portion 51c, the height (position in the z direction) of the reed switch assembly 52 can be adjusted in the hole 51a.

  A hole 52 b is formed substantially at the center of the reed switch assembly 52. The reed switch 53 is provided in the hole 52b. That is, the reed switch 53 is provided on the opposite side to the spool 54 across the bottom of the hole 51 b. When the reed switch assembly 52 is provided inside the hole 51 a, the central axis of the hole 52 b, that is, the reed switch 53 is substantially the same as the central axis A 1 of the case 51.

  The reed switch 53 is a member in which two leads (not shown) made of a ferromagnetic material are enclosed in a glass tube at a predetermined interval. When a magnetic field is externally applied to the reed switch 53, the two reeds are magnetized and come in contact with each other to close the circuit. As a result, the reed switch 53 is turned on. Also, when the magnetic field is erased, the two leads are elastically separated and the circuit is opened. As a result, the reed switch 53 is turned off. The reed switch 53 is known and thus the description thereof is omitted.

  Reed pieces 53a and 53b protrude from both ends of the reed switch 53, respectively. The lead pieces 53 a and 53 b are bent substantially at right angles so as to be substantially orthogonal to the central axis A 1 of the case 51. The lead pieces 53a and 53b are electrically connected to the lead wire 57, respectively. The lead wire 57 connects the lead pieces 53a and 53b to a lamp or the like (not shown).

  The spool 54 is a substantially cylindrical member. FIG. 4 is a perspective view showing an outline of the spool 54. As shown in FIG. The spool 54 mainly has a front end 54a, a flange 54b, and a rear end 54c.

  The tip portion 54a has a diameter substantially the same as that of the hole 511b. The flange portion 54b has a diameter substantially the same as the diameter of the hole 512b. The central axis A3 of the tip portion 54a is offset from the central axis A4 of the flange portion 54b by a distance d. The central axis A3 and the central axis A4 are substantially parallel.

  The tip portion 54a has a first radius r1 and a second radius r2 larger than the first radius r1 around the central axis A4 of the spool 54. A substantially cylindrical hole 54d centered on the central axis A4 is formed in the distal end portion 54a. The hole 54d is provided with a magnet 55 (see FIG. 3).

  The rear end portion 54c has a central axis substantially coincident with the central axis A4 of the flange portion 54b, and is smaller than the diameter of the flange portion 54b.

  It returns to the explanation of FIG. The tip portion 54a is mainly inserted into the hole 511b, and the flange portion 54b is inserted into the hole 512b. At this time, the central axis A3 coincides with the central axis A2, and the central axis A4 coincides with the central axis A1.

  The spool 54 slides inside the hole 51b along the central axis A1 (in the z direction). The tip 54 a slides inside the hole 511 b, and the flange 54 b slides inside the hole 512 b. Thus, the spool 54 has a hole 51b, a space on the high pressure side formed by the hole 511b and the front end 54a, and a space on the low pressure side formed by the hole 512b, the flange 54b, and the rear end 54c. Divide into

  The high-pressure space formed by the hole 511b and the + z-side end (tip portion 54a) of the spool 54 communicates with the space S1 via the hole 51d formed in the case 51. A space on the low pressure side formed by the hole 512b and the -z side end (flange portion 54b and rear end portion 54c) of the spool 54 communicates with the mounting hole 45 and the outflow passage 44, that is, the space S2.

  When the spool 54 is provided inside the hole 51b, the magnet 55 is provided on the surface of the spool 54 facing the bottom of the hole 51b.

  The spring 56 has one end provided at the rear end 54 c and the other end fixed to the case 51 via the E-ring 58. The spring 56 biases the spool 54 in the direction from the hole 512 b to the hole 511 b (force in the + z direction). The spool 54 is movable in the + z direction by the biasing force of the spring 56 until the flange portion 54b abuts on the bottom surface 513b of the hole 512b.

  Next, the operation of the indicator 5 will be described. When clogging of the filter medium 12 does not occur and the pressure difference between the space S1 and the space S2 is equal to or less than the threshold value, the spool 54 is in a position where the reed switch 53 is turned ON by the biasing force of the spring 56. .

  On the other hand, when the pressure in the space S1 is increased due to clogging of the filter medium 12 or the like, the spool 54 moves downward (in the -z direction) against the biasing force of the spring 56. Along with this, the magnet 55 also moves downward.

  When the pressure difference between the space S1 and the space S2 in the filtration device 1 is equal to or more than the threshold, that is, the distance between the reed switch 53 and the magnet 55 is equal to or more than the threshold, the two leads are separated by elasticity and the circuit is opened. As a result, the reed switch 53 is turned off. When the reed switch 53 is switched from the on state to the off state, the lamp is switched between off and on. Thereby, the user can easily know that the pressure difference between the space S1 and the space S2 in the filtration device 1 has become equal to or greater than the threshold value, that is, the filter medium 12 of the filter element 3 is clogged.

  Thereafter, when the filter element 3 is replaced by the user and the pressure in the space S1 becomes low, the biasing force of the spring 56 moves the spool 54 upward (in the + z direction). As a result, the reed switch 53 is turned on again.

  In the present embodiment, the central axis A2 of the hole 511b and the central axis A3 of the tip 54a are offset from the central axis A1 of the case 51 and the central axis A4 of the flange 54b by the distance d. Therefore, when the spool 54 moves along the central axis A1 (in the ± z direction), the spool 54 does not rotate. That is, the offset of the hole 51 b and the spool 54 is a detent mechanism that prevents the spool 54 from rotating relative to the case 51.

  According to the present embodiment, the detection of the differential pressure can be stabilized. For example, when the magnet can be rotated as shown in FIG. 7 (prior art), the reed switch may be turned on or off depending on the position of the magnet in the rotational direction due to the variation in magnetization. In other words, detection of differential pressure may not be stable. This is noticeable when the pressure difference between the space S1 and the space S2 is near the threshold.

  In particular, the circumferential position (the position on the xy plane) of the bent lead piece 53a has a low impression value (good sensitivity) indicating the sensitivity of the reed switch 53. Therefore, when the portion of the magnet 55 where the magnetic field is strong coincides with the circumferential position of the bent lead piece 53a, the pressure difference between the space S1 and the space S2 is smaller than the threshold as compared with the case where it is not. The switch 53 may be turned on.

  On the other hand, when the spool 54 is provided with a rotation stopping mechanism for preventing the spool 54 from rotating relative to the case 51 as in the present embodiment, the positional relationship between the lead piece 53a and the magnet 55 does not change. Therefore, the pressure difference between the space S1 and the space S2 when the reed switch 53 changes from the ON state to the OFF state can be made constant, that is, the detection of the differential pressure can be stabilized.

  Further, according to the present embodiment, the spool 54 is formed by offsetting the central axis A2 of the hole 511b and the central axis A3 of the tip 54a with respect to the central axis A1 of the case 51 and the central axis A4 of the flange 54b. It is possible to realize a rotation stopping mechanism that does not rotate with respect to the case 51 with a simple configuration. In such a rotation stopping mechanism, the amount of rotation of the spool 54 is 0 when the gap between the hole 511b and the tip 54a is reduced (the diameter of the hole 511b and the diameter of the tip 54a are substantially the same). Since it can be in the vicinity, it is possible to provide a highly effective rotation stopping mechanism with a simple configuration. In such a rotation stop mechanism, the amount of offset of the axis (the distance d in the present embodiment) can be arbitrarily set at a value equal to or less than the difference between the radius of the hole 512b and the radius of the hole 511b. By increasing the offset amount, a more effective rotation stopping mechanism can be obtained.

  In the present embodiment, the space formed by hole 511b and tip portion 54a is a space on the high pressure side communicating with space S1, and is formed by hole 512b, flange portion 54b, and rear end portion 54c. The space is the low pressure side space communicating with the space S2, but the space formed by the hole 511b and the tip 54a is the low pressure side space, and is formed by the hole 512b, the flange 54b and the rear end 54c. The space to be stored may be the space on the high pressure side. For that purpose, for example, instead of the hole 51d, a hole connecting the hole 512b with the space S1 and a hole connecting the hole 511b with the space S2 may be formed in the main body 41 of the head 4. In this case, instead of the spring 56 biasing the spool 54 in the + z direction, a spring may be provided inside the hole 511b to bias the spool 54 in the −z direction.

  In the present embodiment, the central axis of the reed switch 53 coincides with the central axis A1, but the central axis of the reed switch 53 may be substantially parallel to the central axis A1, and does not necessarily coincide with the central axis A1. May be The configuration in which the central axis of the reed switch 53 does not coincide with the central axis A1 is possible because the spool 54 and the hole 51b have a rotation stopping mechanism.

  Further, in the present embodiment, the central axis of the reed switch 53 coincides with the central axis of the magnet 55, but the central axis of the reed switch 53 does not necessarily coincide with the central axis of the magnet 55. In order for the magnetic field of the magnet 55 to turn on and off the reed switch 53, the magnet 55 may be on the central axis of the reed switch 53.

Second Embodiment
In the first embodiment, as a rotation stopping mechanism for preventing the spool 54 from rotating with respect to the case 51, the central axis A2 of the hole 511b and the central axis A3 of the tip 54a, the central axis A1 of the case 51 and the flange Although the offset is made with respect to the central axis A4 of the portion 54b, the rotation stopping mechanism for preventing the spool from rotating with respect to the case is not limited to this.

  FIG. 5 is a cross-sectional view of the indicator 5A used in the filtration device in the second embodiment. Since the difference between the first embodiment and the second embodiment is only the use of the indicator 5 or the use of the indicator 5A, only the indicator 5A will be described below. The same parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The indicator 5A mainly includes a case 51A, a reed switch assembly 52, a reed switch 53, a spool 54A, a magnet 55, and a spring 56.

  A hole 51f is formed in the case 51A. The holes 51 f mainly include a hole 511 f and a hole 512 f. The holes 512 f are the same as the holes 512 b, and thus the description thereof is omitted.

  The diameter of the hole 512f is larger than the diameter of the hole 511f. Therefore, the bottom surface 513 f is formed between the hole 511 f and the hole 512 f.

  The central axes of the hole 511 f and the hole 512 f coincide with the central axis A 1 of the case 51. The hole 511f is partially cut away at a plane 514f substantially parallel to the central axis A1.

  The hole 511 f is a space on the high pressure side communicated with the space S 1 through the hole 51 d formed in the case 51. Further, the hole 512 f is a low pressure side space communicating with the space S 2.

  FIG. 6 is a perspective view schematically showing the spool 54A used in the indicator 5A. The spool 54A mainly includes a front end 54e, a flange 54b, and a rear end 54c.

  The tip portion 54e is formed smaller in diameter than the flange portion 54b with the center axis A4 as the center, and a part of the tip portion 54e is cut away in a plane 54f substantially parallel to the center axis A4. The tip portion 54e has a first radius r3 and a second radius r4 larger than the first radius r3 around the central axis A4 of the spool 54. The tip portion 54e is formed with a substantially cylindrical hole 54d centered on the central axis A4.

  The tip portion 54e is mainly inserted into the hole 511f. Therefore, when the spool 54A moves along the central axis A1 (± z direction), the spool 54A is prevented from rotating relative to the case 51A by the flat surface 514f contacting the flat surface 54f (rotation stop) mechanism).

  According to the present embodiment, when the flat surface 514 f and the flat surface 54 f are provided as a rotation stopping mechanism that prevents the spool 54 from rotating relative to the case 51, the reed switch 53 changes from the ON state to the OFF state. The pressure difference between the space S1 and the space S2 can be made constant, that is, the detection of the differential pressure can be stabilized. Although the indicator 5A according to the second embodiment has the same function and effect as the indicator 5 according to the first embodiment, it is more difficult to process than the indicator 5, and in this respect the indicator is better than the indicator 5A. 5 is preferable.

  The embodiment of the present invention has been described in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like within the scope of the present invention are also included. . Those skilled in the art can appropriately change, add, convert, etc. the elements of the embodiment.

  For example, when the spools 54, 54A, etc. do not rotate with respect to the cases 51, 51A, the magnetic field formed by the magnets 55 provided on the spools 54, 54A becomes stable. By stabilizing the magnetic field, stable detection results can be obtained when the differential pressure is constantly detected. In this case, in place of the reed switch, it is possible to use, for example, a Hall IC which is a noncontact magnetic sensor that outputs an electric signal according to a magnetic field by using a Hall effect. By always measuring the magnetic field formed by the magnet 55 using a Hall IC or the like, a voltage corresponding to the pressure difference between the space S1 and the space S2 can be constantly and stably acquired. In the Hall element, a voltage substantially proportional to the magnetic flux density is generated. Therefore, by providing the Hall IC in the magnetic field generated by the magnet 55, the magnetic field can be constantly measured. By continuously inputting the results thus obtained to a computer or the like and comparing the sensor output with the test result, it is possible to predict the remaining life of the filter element. Also, for example, the result obtained continuously and the threshold value are compared using an electric circuit or the like, and the result is input to a computer or the like as a 0 or 1 digital signal to turn off or turn on the light, or A display prompting replacement of the filter element can be displayed on the display unit.

  Further, in the present invention, “abbreviation” is a concept including not only the case of strictly identical but also an error and a deformation that do not lose the sameness. For example, “substantially parallel” is not limited to the case of strictly parallel but is a concept including an error of several degrees, for example. Further, for example, when expressing simply as parallel, orthogonal, coincidence, etc., not only strictly parallel, orthogonal, coincidence, etc., but also substantially parallel, substantially orthogonal, substantially coincidence, etc. shall be included. Further, in the present invention, “near” means including a range (which can be arbitrarily determined) of a region near a reference position. For example, the term “in the vicinity of A” is a concept that indicates a range of area near A, which may or may not include A.

1: Filter device 2: Housing 2a: Female screw part 3: Filter element 4: Head 5, 5A: Indicator 6: Drain 11: Inner cylinder 12: Filter material 13, 14: Plates 22, 23, 24: Sealing member 41: Main body 41a A male screw portion 42: a central cylinder 43: an inflow passage 44: an outflow passage 45: a mounting hole 45a: a female screw portion 46: a hole 51, 51A: a case 51a: a hole 51b: a hole 51c: a female screw portion 51d: a hole 51e: a male screw portion 51f: Hole 52: Reed switch assembly 52a: Male thread 52b: Hole 53: Reed switch 53a, 53b: Reed piece 54, 54A: Spool 54a, 54e: Tip 54b: Flange 54c: Rear end 54d: Hole 54f: Flat 55: Magnet 56: Spring 57: Lead wire 58: E ring 511b: Hole 511f: Hole 512b: Hole 512 f: Hole 513 b: Bottom 513 f: Bottom 514 f: Plane

Claims (5)

A case having a substantially cylindrical shape, in which a substantially cylindrical hole having a central axis substantially parallel to a central axis of the case is formed;
A spool having a substantially cylindrical shape slidably provided inside the hole, the spool dividing the hole into a first space and a second space;
A substantially cylindrical reed switch provided inside the case on the opposite side to the spool across the bottom of the hole, the reed being provided such that the central axis is substantially parallel to the central axis of the case With the switch
An elastic member that biases the spool in a direction from the first space to the second space;
And a magnet provided on a central axis of the reed switch on a surface of the spool facing the bottom surface of the hole.
The case and the spool have a detent mechanism that the spool is prevented from rotating relative to the casing,
In the spool, a tip end portion provided with the magnet and a body portion other than the tip portion are axially aligned, and a distance from a central axis of the body portion to an outer periphery of the tip portion when viewed from the axial direction is A differential pressure detection device characterized in that it is not constant . A case having a substantially cylindrical shape, in which a substantially cylindrical hole having a central axis substantially parallel to a central axis of the case is formed;
A spool having a substantially cylindrical shape slidably provided inside the hole, the spool dividing the hole into a first space and a second space;
A substantially cylindrical reed switch provided inside the case on the opposite side to the spool across the bottom of the hole, the reed being provided such that the central axis is substantially parallel to the central axis of the case With the switch
An elastic member that biases the spool in a direction from the first space to the second space;
And a magnet provided on a central axis of the reed switch on a surface of the spool facing the bottom surface of the hole.
The case and the spool have a rotation stop mechanism that prevents the spool from rotating relative to the case,
The hole has a first hole formed with a first diameter and a second hole formed with a second diameter that is larger than the first diameter,
The central axis of the second hole substantially coincides with the central axis of the case;
The central axis of the first hole is offset from the central axis of the case by a first distance,
The spool is substantially the same as the first diameter, and a flange portion having a diameter substantially the same as the second diameter, and the central axis is offset by the first distance with respect to the central axis of the flange portion A differential pressure detection device, comprising: The differential pressure detection device according to claim 2 , wherein
The case is formed with a hole communicating the first hole with the outside of the case.
The differential pressure detection device according to claim 1, wherein the hole is formed on the opposite side of the side where the central axis of the first hole is deviated by the first distance with respect to the central axis of the case. A filtration apparatus comprising the differential pressure detection device according to any one of claims 1 to 3 . The filtration device according to claim 4 , wherein
An upstream side of the filter communicates with one of the first space and the second space, and a downstream side of the filter communicates with the other.

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