JP2019219316A - Filter differential pressure detection device - Google Patents

Abstract

To provide a filter differential pressure detection device capable of continuously detecting changes in differential pressure between upstream and downstream sides of a filter element in a filter device.SOLUTION: A first filter differential pressure detection device 10 which comprises a case body 20, a movable unit 30, and a magnetic sensor unit 50 is mounted on a filter device 100 with the case body 20 partially fitted in a filter head 110. When differential pressure is generated with pressure of hydraulic oil in an inflow passage 116C getting larger than that in an outflow passage 117B, a movable body 31 mounted with a magnet 37 is moved closer to the magnetic sensor unit 50. The magnetic sensor unit 50 detects changes in a magnetic field of the magnet 37 in accordance with movement of the movable body 31 as changes in the differential pressure and outputs voltage corresponding to the detected differential pressure.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a filter differential pressure detecting device for detecting a differential pressure across a filter element in a filter device used for filtering a fluid.

  2. Description of the Related Art Conventionally, a filter device for filtering a fluid is provided in a tank for storing a fluid such as water, hydraulic oil, and fuel, and in a flow path through which the fluid flows. The filter device includes, for example, a filter case having a primary side flow path and a secondary side flow path, and a filter element housed in the filter case. Then, the fluid introduced into the filter case through the primary flow path is allowed to pass through the filter element and then flow out through the secondary flow path, so that dirt, dust, metal powder, and the like in the fluid are removed. Foreign matter is captured and removed by the filter element. When the filter element is clogged, it becomes difficult for the fluid to pass through the filter element, and the differential pressure across the filter element increases, thereby damaging the filter element and releasing foreign substances trapped by the filter element. There is a possibility that such troubles may occur.

  Patent Document 1 below discloses a clogging detection device that detects a clogged state of a filter that filters compressed air. This clogging detection device receives the pressure of the compressed air on the inlet side and the outlet side of the filter via the primary side flow path and the secondary side flow path, and includes a primary diaphragm and a secondary side in the detection device. A diaphragm and a clogging detection shaft that moves in the axial direction under the force of a compression coil spring are provided. A permanent magnet is mounted on the clogging detection shaft, and two sensors sensitive to the magnetic force of the permanent magnet are provided at different positions in the axial direction outside the case of the detection device. When the detection shaft moves in the axial direction together with the permanent magnet in response to a change in the pressure difference between the primary side flow path and the secondary side flow path, that is, the pressure difference before and after the filter, the detection is performed by the sensor, and the detection of the filter is performed. The clogging state can be detected in three stages: a normal state, a clogged state within an allowable range, and a clogged state requiring replacement of a filter.

Japanese Patent No. 4094158

  The clogging detection device described in Patent Literature 1 detects a clogged state of a filter in three stages. However, if a change in the clogged state can be continuously detected, the filter may be used. For example, it is easy to predict the replacement time of the vehicle in advance, and convenience is improved. If the change in the differential pressure before and after the filter can be continuously detected, it is possible to continuously detect the change in the clogging state based on the change. However, in the above-described clogging detection device, in order to continuously detect a change in the differential pressure before and after the filter, it is necessary to greatly increase the number of installed sensors, which is difficult to realize.

  The present invention has been made in view of such circumstances, and has as its object to provide a filter differential pressure detecting device capable of continuously detecting a change in differential pressure across a filter element in a filter device. I do.

The filter differential pressure detection device according to the present invention, the fluid introduced into the filter case through the primary side flow path formed in the filter case, passing through the filter element stored in the filter case, the A filter differential pressure detecting device for detecting a differential pressure of a fluid pressure in the primary side channel and a fluid pressure in the secondary side channel in a filter device flowing out through a secondary side channel formed in a filter case, A case body having therein a movable body installation space connected to the primary side flow path and the secondary side flow path; a first space communicating the movable body installation space with the primary side flow path; A movable body that is partitioned into a second space communicating with the side flow path and that is movably provided in the movable body arrangement space and that moves in accordance with the differential pressure; and in the first space or the second space Provided in the above An urging body that urges the body in the moving direction and regulates an amount of movement of the movable body that moves in accordance with the differential pressure; a permanent magnet provided on the movable body; and a predetermined position of the case body. A magnetic sensor that senses a magnetic field at the predetermined position by the magnet; and a detection unit that obtains the differential pressure based on the strength of the magnetic field sensed by the magnetic sensor.

  In the filter differential pressure detection device according to the present invention, the detection unit obtains the position of the movable body provided with the magnet based on the strength of the magnetic field sensed by the magnetic sensor, based on the obtained position. Preferably, the differential pressure is determined by determining the biasing force of the biasing body.

  In the filter differential pressure detecting device according to the present invention, it is preferable that the filter is configured to be mounted on the filter case in a state where a part of the case body is fitted in the filter case.

  In the filter differential pressure detection device according to the present invention, the case body is provided at one end of the case base so as to surround an outer surface of one end of the case base having the movable body installation space therein, and one end of the case base. And a cylindrical peripheral wall portion, and the magnetic sensor is preferably disposed on an outer surface of the one end portion.

  Further, in the filter differential pressure detecting device according to the present invention, the case base may be formed of a non-magnetic material, the peripheral wall may be formed of a magnetic material, and may be detachably attached to the case base. The case base and the peripheral wall may be integrally formed of a non-magnetic material.

  Further, in the filter differential pressure detecting device according to the present invention, the detecting unit outputs a signal having a level corresponding to the obtained differential pressure, and operates while the magnetic sensor is operating even when the differential pressure is 0 or less. Preferably, the case body is configured to output a signal of a predetermined level, and the case body includes a portion connecting the first space and the primary side flow path and the second space and the secondary side flow path. It is preferable that a porous sintered metal body is provided at the connecting portion.

  According to the filter differential pressure detecting device according to the present invention, the movable body moves in the movable body installation space according to the differential pressure of the fluid pressure in the primary side flow path and the secondary side flow path. At this time, since the magnet provided on the movable body also moves together with the movable body, the relative position (distance) to the magnetic sensor changes, and the change in the relative position changes the strength of the magnetic field sensed by the magnetic sensor. Since the detection unit obtains the differential pressure based on the strength of the magnetic field sensed by the magnetic sensor, it is possible to continuously detect a change in the differential pressure before and after the filter element.

  Further, according to the filter differential pressure detecting device of the present invention, the filter clogging detecting device can be made compact by adopting a configuration in which a part of the case body is fitted into the filter case in a state of being fitted into the filter case. It can be attached to the device.

  Further, according to the filter differential pressure detecting device according to the present invention, the case body is provided at one end of the case base so as to surround the outer surface of the case base having the movable body installation space therein and the one end of the case base. The magnetic sensor can be surrounded and protected by the peripheral wall by arranging the magnetic sensor on the outer surface of one end of the magnetic sensor. Therefore, it is possible to prevent a situation in which a tool or the like collides with the magnetic sensor and the magnetic sensor is damaged.

  Further, according to the filter differential pressure detecting device according to the present invention, the case base is formed of a non-magnetic material (a material through which magnetic flux easily passes), and the peripheral wall portion is formed with a magnetic material (a material through which magnetic flux does not easily pass). The magnetic field by the magnet in the case base can be sensed by the magnetic sensor without being disturbed by the case base, and the external magnetic field around the magnetic sensor is blocked by the peripheral wall portion, and the influence is exerted on the magnetic sensor Can be prevented. Therefore, it is possible to improve the detection accuracy of the magnetic sensor. Further, by configuring the peripheral wall portion to be detachably attached to the case base, the magnetic sensor can be installed with the peripheral wall portion removed, so that the peripheral wall portion hinders the installation of the magnetic sensor. And installation work can be easily performed.

  Further, according to the filter differential pressure detecting device of the present invention, the case base and the peripheral wall are integrally formed of a non-magnetic material, so that the magnetic field generated by the magnet in the case base is not obstructed by the case base. The detection can be performed by the sensor, and the configuration of the case body can be simplified.

  Further, according to the filter differential pressure detecting device according to the present invention, the detecting section is configured to output a signal having a level corresponding to the obtained differential pressure. Can be determined. Further, the detection unit is configured to output a signal of a predetermined level during the operation of the magnetic sensor even when the differential pressure is 0 or less, so that if the signal is not output from the detection unit, the signal line is disconnected. Since it can be determined that some kind of abnormality has occurred, it is possible to detect the occurrence of the abnormality at an early stage.

  Further, according to the filter differential pressure detecting device according to the present invention, the case body has a porous portion in a portion connecting the first space and the primary flow path and a portion connecting the second space and the secondary flow path. By providing the sintered metal body, it is possible to capture and remove foreign matter such as iron powder which tends to flow into the movable body installation space by the sintered metal body. Therefore, it is possible to prevent the magnetic sensor from malfunctioning or malfunctioning due to foreign matter such as iron powder adhering to the magnet.

1 is a cross-sectional view of a filter device to which a first filter differential pressure detecting device according to the present invention is attached. FIG. 4 is a partial cross-sectional view of the filter device in a state where the first filter differential pressure detecting device is mounted. FIG. 2 is a front view of the first filter differential pressure detecting device. It is sectional drawing of the said 1st filter differential pressure detection apparatus. FIG. 3 is a circuit diagram around a magnetic sensor unit of the first filter differential pressure detecting device. It is a figure showing the graph of the output voltage characteristic of the above-mentioned magnetic sensor unit. FIG. 4 is a diagram illustrating a relationship among an output voltage of the magnetic sensor unit, a differential pressure, and a clogging rate. It is sectional drawing of the 2nd filter differential pressure detection apparatus which concerns on this invention. It is an exploded sectional view of the case body of the above-mentioned 2nd filter differential pressure detecting device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIGS. 1 and 2 show a filter device 100 to which a first filter differential pressure detecting device 10 according to the present invention is attached. First, an overall configuration of the filter device 100 will be described with reference to these drawings.

  The filter device 100 is used, for example, as a line filter of a hydraulic circuit mounted on a working vehicle, and is provided with a filter head 110 provided in the middle of a hydraulic oil passage (positive pressure line) between a hydraulic pump and an actuator. And an element assembly (cartridge assembly) 130 detachably attached to the filter head 110.

  The filter head 110 is configured with a body 111 formed in a cylindrical shape using a metal material such as aluminum or cast iron or a resin material as a base. The body 111 has an inlet port 112 communicating with the outside (upstream of the hydraulic oil passage) to allow the hydraulic oil to flow into the filter device 100, and a body 111 communicating with the outside (downstream of the hydraulic oil passage) of the filter device 100. An outlet port 113 for allowing hydraulic oil to flow out. The body 111 has an outer cylindrical portion 114 and an inner cylindrical portion 115 formed in a double cylindrical shape projecting downward in the figure, inflow passages 116A to 116C as primary flow passages, and a secondary flow passage. Outflow passages 117A and 117B are provided.

  The inflow passage 116A is a passage that is connected to the inlet port 112 and extends in the left-right direction in the drawing, and the inflow passage 116B is a passage that is connected to the inflow passage 116a and is extended in the vertical direction in the drawing. The inflow passage 116C is a passage extending in an annular shape between the inner peripheral surface of the outer cylindrical portion 114 and the outer peripheral surface of the inner cylindrical portion 115, and is open at a lower portion and formed inside the element assembly 130. It is connected to the element arrangement space 143 vertically in the drawing. The inflow passages 116A to 116C guide the hydraulic oil flowing from the inlet port 112 in the order of the inflow passages 116A, 116B, and 116C, and flow into the element arrangement space 143 (an inflow space 143A described later).

  The outflow passage 117A is a passage that is surrounded by the inner peripheral surface of the inner cylindrical portion 115 and extends vertically in the drawing, and the outflow passage 117B is a passage that is connected to the outlet port 113 and extends in the left and right direction in the drawing. The outflow channel 117a is open at the lower part, and is connected vertically to the element disposition space 143 formed inside the element assembly 130 in the figure. The outflow passages 117A and 117B are connected to each other, and the hydraulic oil after filtration from the element arrangement space 143 (outflow space 143B to be described later) is guided in the order of the outflow passages 117A and 117B so as to flow out from the outlet port 113. Has become.

  A partition wall 118 is provided between the inflow path 116A and the outflow path 117B, and a relief valve 160 is installed on the partition wall 118. The relief valve 160 mainly includes a shaft 161, a poppet 162, and a compression coil spring 163, and the shaft 161 is held by a partition wall 118 so as to be movable in the left-right direction in the figure. The poppet 162 of the relief valve 160 is normally pressed against the valve seat 121 by the urging force of the compression coil spring 163, thereby closing between the inflow passage 116A and the outflow passage 117B. . In addition, the pressure on the outflow passage 117B acts on the poppet 162 to the left in the drawing, and the pressure on the inflow passage 116A acts on the right in the drawing via the fine holes 119 formed in the partition wall 118. I do. When the pressure on the inflow passage 116A increases and the force acting on the poppet 122 rightward in the drawing due to the pressure difference between the inflow passage 116A and the outflow passage 117B exceeds the urging force of the compression coil spring 123, , The poppet 122 is separated from the valve seat portion 119 so that the inflow passage 116A and the outflow passage 117B communicate with each other.

The body 111 is provided with a communication hole 123 that communicates the outflow path 117B with the external space, and a communication hole 124 that communicates the outflow path 117B and the inflow path 116C. As shown in FIG. 2, the first filter differential pressure detecting device 10 is attached to the communication holes 123 and 124 (details will be described later).

  The element assembly 130 includes an element case 140 detachably attached to the filter head 110, and a filter element 150 inserted and held in the element case 140. The filter head 110 and the element case 140 constitute a filter case in the present invention.

  The element case 140 is formed in a bottomed cylindrical shape that is open upward, and has an element disposition space 143 that can accommodate the filter element 150 therein. A seal ring 141 formed of an elastic member such as synthetic rubber is mounted on the outer surface of the upper end of the element case 140. A male screw 142 is formed on the upper outer peripheral surface of the element case 140 so as to be screwed with a female screw 125 formed on the lower peripheral inner surface of the filter head 110. By combining, the element assembly 130 can be assembled to the filter head 110.

  The filter element 150 is formed by winding a filter material 152 having a chrysanthemum-shaped cross section, which is folded in a bellows shape, around a thin-walled cylindrical inner cylinder 151 made of a punch sheet or the like having a large number of small holes 151a. An annular upper end plate 153 is fixed to the upper end of the filter element 150, and a disk-shaped lower end plate 155 is fixed to the lower end. The inner tube 151 and the filter medium are fixed by the upper and lower end plates 153 and 155. Both ends in the direction of the cylindrical axis 152 are sandwiched.

  A seal ring 154 formed of an elastic member such as synthetic rubber is attached to a central portion (central opening) of the upper end plate 153. When the inner cylindrical portion 115 of the filter head 110 is inserted into the inner diameter of the seal ring 154, the inner cylindrical portion 115 of the filter head 110 is fitted and held by the elastic force of the seal ring 154 (the filter element 150 and the inner cylindrical portion). The gap between the outer peripheral surface of the portion 115 and the outer peripheral surface is maintained in a liquid-tight state.

  The filter medium 152 is configured by pleating (folding) a filter medium sheet capable of collecting foreign matter in hydraulic oil into a bellows shape with a constant bending width and winding it into a substantially cylindrical shape. The filter medium 152 is, for example, a cylindrical one made of glass fiber or non-woven fabric having a predetermined thickness, a one formed by combining these materials, or a sintered product formed in a cylindrical shape. The most suitable material and shape are selected according to the liquid to be filtered, the solid matter to be removed, and the like.

  In a state where the element assembly 130 is mounted on the filter head 110, the element arrangement space 143 in the element case 140 includes a space on the outer peripheral side of the filter element 150 (referred to as an “inflow space 143A”) and the filter element 150. (Referred to as “outflow space 143B”). The inflow space 143A serves as a dirty side through which hydraulic oil before filtration (hydraulic oil flowing into the inflow space 143A from the inlet port 112 via the inflow passages 116A, 116B, and 116C) flows, and the outflow space 143B serves as a dirty side. It becomes a clean side through which the hydraulic oil (the hydraulic oil flowing out of the outlet port 113 via the outflow passages 117A and 117B after passing through the filter element 150) flows.

  Next, the configuration of the first filter differential pressure detecting device 10 (hereinafter, also simply referred to as “first detecting device 10”) will be described with reference to FIGS. 3 to 5 additionally. As shown in FIG. 3, the first detection device 10 mainly includes a case body 20, a movable body unit 30, and a magnetic sensor unit 50.

  The case body 20 is closed at one end (upper end in the drawing) and opened at the other end (lower end in the drawing), and has a cylindrical case base 21 having a movable body installation space 40 therein; And a cylindrical peripheral wall 22 provided at one end of the case base 21 so as to surround an outer surface 21 a of one end of the case 21. The case base 21 and the peripheral wall 22 are integrally formed of a nonmagnetic material such as aluminum. A hexagonal column-shaped tool engaging portion 23 is provided on the upper outer peripheral surface of the case base 21 in the drawing, and a male screw 24 is formed on the outer peripheral surface of the case base 21 on the lower side of the tool engaging portion 23 in the drawing. ing. An annular groove 25 is formed in a portion of the outer peripheral surface of the case base 21 between the tool engaging portion 23 and the male screw 24.

  The movable body unit 30 includes a movable body 31, a coil spring 35, and a permanent magnet 37. The movable body 31 includes a cylindrical large-diameter shaft portion 32 and a cylindrical small-diameter shaft portion 33 provided coaxially with the large-diameter shaft portion 32 on the upper end surface of the large-diameter shaft portion 32 in the drawing. The large-diameter shaft portion 32 and the small-diameter shaft portion 33 are integrally formed of a nonmagnetic material such as aluminum. The movable body 31 has a large-diameter shaft portion 32 that divides the movable body installation space 40 into a first space 41 below the large-diameter shaft portion 32 in the drawing and a second space 41 above the large-diameter shaft portion 32 in the drawing. It is partitioned into a space 42 and is provided in the movable body arrangement space 40 so as to be movable in the axial direction (vertical direction in the figure).

  The coil spring 35 is disposed between the upper surface portion 42a of the second space 42 and the large-diameter shaft portion 32 with one end held by the upper surface portion 42a and the other end held by the large-diameter shaft portion 32. . The coil spring 35 is elastically deformed to the compression side by, for example, the movable body 31 that moves upward in the figure, and urges the movable body 31 downward in the figure by its restoring force, thereby restricting the moving amount of the movable body 31 It is configured to The permanent magnet 37 (for simplicity, also referred to as “magnet 37”) is provided at the tip of the small diameter shaft portion 33. Specifically, for example, a hole is formed at the tip of the small-diameter shaft portion 33, and the magnet 37 is press-fitted and held in the hole.

  The magnetic sensor unit 50 is composed of, for example, a linear Hall IC. As shown in FIG. 5, the magnetic sensor unit 50 includes a Hall element 52 as a magnetic sensor and a detection unit 53 in a package 51, and three terminals (power supply voltage terminals 54) on the periphery of the package 51. , A ground terminal 55 and an output terminal 56). The Hall element 52 is an element that generates an electromotive force by the Hall effect when a magnetic field acts. The detection unit 53 includes an amplifier, a comparator, a control circuit, and the like, and is configured to output a signal (voltage) having a level according to a differential pressure across the filter element 150 from the output terminal 56 to the control device 70. (Details described later).

  The power supply voltage terminal 54 is connected to a power supply 61 that supplies a voltage of, for example, 5 V (volt), and a capacitor 62 is arranged on a circuit between the power supply voltage terminal 54 and the ground terminal 55. Although not shown in FIG. 4 and the like, the magnetic sensor unit 50, together with the capacitor 62, is installed on an insulating plate made of bakelite or the like, and is provided on the outer surface 21a at one end of the case base 21 via this insulating plate. Be placed. Further, lead wires are connected to the three terminals 54 to 56, respectively, and the respective lead wires are drawn out of the peripheral wall portion 22. The magnetic sensor unit 50 is disposed in the space 26 inside the peripheral wall 22, and is filled with a filler such as resin in a state where the lead wire is drawn out therefrom.

As shown in FIG. 4, a cylindrical communication hole 27 that connects the inside (second space 42) of the case base 21 to the outside is provided in the middle part of the case base 21 in the vertical direction in the drawing (the lower part of the male screw 33). A cylindrical sintered metal body 45 having an outer diameter substantially the same as the inner diameter of the communication hole 27 is press-fitted and fixed in the communication hole 27. A disc-shaped sintered metal body 46 having an outer diameter substantially equal to the inner diameter of the open end 21b is press-fitted and fixed inside the open end 21b of the case base 21. The sintered metal bodies 45 and 46 are formed in a state where the contacts of the metal powder are connected to each other, and a large number of fine holes (for example, about several μm to several tens μm) are formed between the powder metal on the surface and inside. (Porous diameter). The sintered metal bodies 45 and 46 have a function of capturing and removing foreign matter such as iron powder that is going to flow into the movable body arrangement space 40 (the first space 41 and the second space 42).

  The first detection device 10 configured as described above is mounted on the filter device 100 as shown in FIG. Specifically, as shown in FIG. 1, a female screw 127 is formed on the inner peripheral surface of the communication hole 123 formed in the filter head 110, and the first detection device 10 The case base 21 is inserted from its open end 21b side, and the male screw 24 on the outer peripheral surface of the case base 21 is screwed with the female screw 127 on the inner peripheral surface of the communication hole 123. As a result, the first detection device 10 has a state in which a part of the case body 20 (the part below the tool engagement portion 23 of the case base 21) is fitted into the filter head 110 as shown in FIG. Thus, the filter device is compactly mounted on the filter device 100. When mounting the first detection device 10 on the filter device 100, the mounting operation can be performed by engaging a tool for tightening and loosening such as a wrench with the tool engagement portion 23 of the case base 21. When the first detection device 10 is mounted on the filter device 100, a seal ring (not shown) is appropriately disposed in the groove 25 of the case base 21.

  Next, the operation of the first detection device 10 mounted on the filter device 100 will be described with reference to FIGS. 6 and 7 additionally. As shown in FIG. 2, in the first detection device 10 mounted on the filter device 100, the open end 21 b of the case base 21 is fitted into a communication hole 124 (see FIG. 1) in the filter device 100. Thereby, the first space 41 in the case base 21 is communicated with the inflow passage 116 </ b> C in the filter device 100 via the sintered metal body 46. Further, in a state of being mounted on the filter device 100, the communication hole 27 of the case base 21 faces the outflow passage 117 </ b> B in the filter device 100, whereby the second space 42 in the case base 21 is Through the body 45, it is connected with the outflow channel 117B in the filter device 100.

  As shown in FIG. 2, in a state where the first space 41 in the case base 21 is connected to the inflow path 116C and the second space 42 is connected to the outflow path 117B, the movable body 31 in the case base 21 has the inflow path. An upward pressing force (hereinafter also referred to as “primary pressing force”) in the figure due to the pressure of the hydraulic oil flowing into the first space 41 from the pressure 116C, and the pressure of the hydraulic oil flowing into the second space 42 from the outflow passage 117B. (Hereinafter also referred to as “secondary side pressing force”). When the two pressing forces are equal to each other, the movable body 31 is in a position where the urging force of the coil spring 35 does not act on the movable body 31 (a state in which the coil spring 35 is not elastically deformed) (hereinafter, “initial position”). (The effect of the gravitational force and frictional force acting on the movable body 31 can be ignored). In the case of this example, when the filter element 150 of the filter device 100 is not clogged at all, the primary side pressing force and the secondary side pressing force are equal, and the movable body 31 is located at the initial position. I do.

  When the filter element 150 is clogged, it becomes difficult for the hydraulic oil to pass through the filter element 150, and the pressure of the hydraulic oil in the inflow passage 116C becomes larger than the pressure of the hydraulic oil in the outflow passage 117B (hereinafter referred to as “the differential pressure”). The pressure difference before and after the filter is also generated). Due to the pressure difference before and after the filter, the primary-side pressing force acting on the movable body 31 becomes larger than the secondary-side pressing force, and the movable body 31 moves to the second space 42 side due to the influence. When the movable body 31 moves toward the second space 42, the coil spring 35 is elastically deformed toward the compression side, and urges the movable body 31 toward the first space 41 by the restoring force. The movable body 31 moves to a position where the combined force of the urging force received from the coil spring 35 and the secondary-side pressing force is balanced with the primary-side pressing force, and stops. Since the differential pressure across the filter increases as the clogging of the filter element 150 progresses, the position of the movable body 31 changes in proportion to the change in the differential pressure across the filter.

  The magnet 37 provided at the tip of the movable body 31 forms a predetermined magnetic field around it. This magnetic field (magnetic flux) passes through the case base 21 without being hindered by the case base 21 because the case base 21 is formed of a nonmagnetic material. The Hall element 52 (see FIG. 5) of the magnetic sensor unit 50 installed on the outer surface 21a of the distal end of the case base 21 senses this magnetic field without contacting the magnet 37. At this time, the strength (magnetic flux density) of the magnetic field sensed by the Hall element 52 changes according to the distance between the Hall element 52 and the magnet 37. Specifically, as the magnet 37 approaches the Hall element 52, the strength of the magnetic field sensed by the Hall element 52 increases. As described above, the position of the movable body 31 changes as the differential pressure across the filter increases, and this change in position causes the magnet 37 to approach the Hall element 52. Therefore, as the differential pressure across the filter increases, the strength of the magnetic field sensed by the Hall element 52 increases.

  The detection unit 53 (see FIG. 5) of the magnetic sensor unit 50 outputs a voltage of a level corresponding to the differential pressure across the filter based on the strength of the magnetic field sensed by the Hall element 52. FIG. 6 shows an example of the characteristic of the output voltage. In this example, when the differential pressure across the filter is 0 (unit: kPa: kilopascal) or less (hereinafter referred to as “no-load state”), a voltage of 2.5 V is output, and the differential pressure across the filter is 500 kPa. In the state described above, a voltage of 5.0 V is output. When the differential pressure across the filter is between 0 V and 500 V, a voltage having a value (proportional) according to the differential pressure value is output. As described above, since the voltage of 2.5 V is output even in the no-load state, when the output voltage value is significantly lower than 2.5 V (for example, 0 V), the magnetic sensor unit 50 functions normally. It can be determined that some abnormality has occurred, such as that the connection has not been made or that the electric wire connected to the magnetic sensor unit 50 has been broken. Also, no matter how large the differential pressure across the filter becomes, a voltage exceeding 5 V is not output. Therefore, the output voltage value becomes excessive due to the increase in the differential pressure across the filter, and the magnetic sensor unit 50 may be overloaded. Can be prevented.

  This output voltage characteristic is set as follows. That is, based on the relationship between the change in the urging force of the coil spring 35 with respect to the change in the position of the movable body 31 (magnet 37) and the relationship between the change in the differential pressure with respect to the change in the urging force of the coil spring 35, The relationship between the movable body position and the differential pressure, which indicates the relationship between the change in the position and the change in the differential pressure across the filter, is determined. Further, a movable body position-magnetic field relationship indicating a relationship between a change in the position of the movable body 31 and a change in the strength of the magnetic field sensed by the Hall element 52 is obtained. Then, based on the obtained movable body position-differential relation and movable body position-magnetic field relation, a magnetic field-differential pressure relation indicating a relation between a change in the differential pressure across the filter and a change in the magnetic field strength is obtained. Further, a magnetic field-output voltage relationship indicating the correspondence between the strength of the magnetic field sensed by the Hall element 52 and the output voltage value is determined, and the output voltage is determined based on the magnetic field-output voltage relationship and the magnetic field-differential pressure relationship. The output voltage characteristic of FIG. 6 showing the correspondence between the pressure and the differential pressure is determined.

As described above, the detecting unit 53 obtains the position (for example, a relative position with respect to the initial position) of the movable body 31 provided with the magnet 37 based on the strength of the magnetic field sensed by the Hall element 52, and sets the obtained position to Based on the biasing force of the coil spring 35, the differential pressure across the filter is determined, and a voltage having a level corresponding to the determined differential pressure across the filter is output. Further, in this example, as shown in FIG. 7, the differential pressure across the filter is associated with the clogged state (clogging rate) of the filter element 150, so that the detection unit 53 (magnetic sensor unit 50) outputs The applied voltage value is an index indicating the clogging rate of the filter element 150. In the case of this example, the time when the differential pressure before and after the filter becomes 300 kPa is set as the replacement reference time of the filter element 150, and the clogging rate at that time is set to 100%. It has passed). Correlation between the clogging rate and the pressure difference before and after the filter can be appropriately performed according to the type of the filter element 150, the use environment, and the like. For example, in a situation where it is desired to set the time when the differential pressure before and after the filter is 200 kPa or 400 kPa as the replacement reference time, the correspondence may be set with the clogging rate at that time being 100%. The first detection device 10 is configured to output a voltage at a level corresponding to the differential pressure value when the differential pressure across the filter is in the range of 0 to 500 kPa. Therefore, if the exchange reference time can be set within the above range, it is possible to cope without changing the characteristics of the coil spring 35, the magnet 37, the magnetic sensor unit 50, and the like, and the versatility is high.

  The voltage output from the detection unit 53 is input to the control device 70 (see FIG. 5). The control device 70 can perform a predetermined process according to the input voltage value. For example, the input voltage value, the differential pressure value corresponding to the voltage value, or the clogging rate may be displayed on a display (not shown). Further, when the input voltage value reaches a predetermined value (for example, 4.0 V), a display for prompting a filter replacement may be displayed on the display. When the input voltage value becomes 0 V, it is determined that an abnormality such as disconnection has occurred, and a warning lamp (not shown) is turned on, or a sound generator (not shown) is used. A warning sound may be generated.

  As described above, according to the first detection device 10, a change in the strength of the magnetic field sensed by the Hall element 52 can be regarded as a change in the differential pressure across the filter. It is possible to continuously detect a change in the differential pressure across the filter based on the strength of the magnetic field. Further, since the differential pressure across the filter is associated with the clogged state (clogging rate) of the filter element 150, a change in the clogged state of the filter element 150 is continuously detected based on the detected differential pressure across the filter. It is possible to do. As a conventional technique, a movable body that moves in the case body according to a change in the pressure difference before and after the filter and a terminal body fixed to the case body are provided, and the movable body comes into contact with the terminal body or separates from the terminal body. There is known a differential pressure detecting device configured to electrically detect the fact. In this type of differential pressure detecting device, it is necessary to seal between the insulated portion and the case body in a state where the movable body or the terminal body is insulated from the case body, but it is difficult to ensure sufficient sealing performance. Therefore, it is not suitable when the fluid pressure is high. On the other hand, the first detection device 10 only needs to seal the portion where the case body 20 is attached to the filter head 110 (for example, dispose a seal ring in the groove 25 of the case base 21). However, even when the pressure is high, sufficient sealing performance can be ensured.

  Next, the configuration of the second filter differential pressure detecting device 10K (hereinafter, also simply referred to as “second detecting device 10K”) will be described with reference to FIGS. 8 and 9 additionally. As shown in FIGS. 8 and 9, the second detection device 10K mainly includes a case body 20K, a movable body unit 30K, and a magnetic sensor unit 50K. In the second detection device 10K shown in FIGS. 8 and 9, elements that are conceptually common to the components of the above-described first detection device 10 are denoted by the same reference numerals as those used in the first detection device 10. It is attached.

  In the second detection device 10K, the movable unit 30K and the magnetic sensor unit 50K have the same configurations and functions as the above-described movable unit 30 and the magnetic sensor unit 50, respectively, and a detailed description thereof will be omitted. . The main difference from the first detection device 10 lies in the configuration of the case body 20K. This case body 20K has a cylindrical case base 21K having one end (upper end in the drawing) closed and the other end (lower end in the drawing) open, and a movable body installation space 40 inside, and a case. A cylindrical peripheral wall 22K detachably attached to one end of the case base 21 so as to surround the outer surface 21a of the one end of the base 21K.

As shown in FIG. 9, a male screw 28 is formed on the outer peripheral surface of the upper end of the case base 21K in the figure, and an annular flange 81 is formed below the male screw 28 in the figure. On the other hand, a female screw 29 is formed on a lower inner peripheral surface of the peripheral wall portion 22K in the drawing, and an annular groove portion 82 is formed below the female screw 29 in the drawing. The peripheral wall portion 22K is in a state in which the female screw 29 is screwed into the male screw 28 of the case base 21K so that the flange 81 of the case base 21K is fitted to the groove 82 (
(See FIG. 8), and is attached to one end of the case base 21K. The case base 21K is formed of a non-magnetic material such as aluminum, whereas the peripheral wall 22K is formed of a magnetic material such as steel.

  In the second detection device 10K, the work of installing the magnetic sensor unit 50 on one end outer surface 21a of the case base 21K can be performed in a state where the peripheral wall 22K is detached from the case base 21K. There is an advantage of improving. Further, by forming the peripheral wall 22K from a magnetic material, external magnetism (for example, disturbance magnetism such as terrestrial magnetism) around the peripheral wall 22K can be cut off by the peripheral wall 22K. It is possible to prevent the 50K from malfunctioning or malfunctioning. The peripheral wall 22K and the case base 21K may be joined and integrated.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention. For example, in the above-described embodiment, the configuration is such that the magnet 37 approaches the Hall element 52 as the differential pressure across the filter increases, but this is not a limitation, and the differential pressure across the filter increases. May be configured so that the magnet 37 is separated from the Hall element 52 according to the above. Further, a magnetic sensor other than the Hall element 52 may be used.

  In the above-described embodiment, the case where the filter differential pressure detecting device according to the present invention is mounted on a line filter for filtering hydraulic oil has been described as an example. However, the present invention is not limited to this. It is also possible to use it by attaching it to a filter device such as an oil filter for filtering a liquid (for example, lubricating oil, fuel, water, etc.), or a filter device other than a line filter such as a suction filter and a return filter. . Further, in the above-described embodiment, the type in which the case is removed and the internal filter element is replaced has been described as an example of the filter device. However, the present invention is not limited to this. A filter device of a type (spin-on type) or a type (return type) mounted in a tank may be used.

10 First filter differential pressure detecting device 10K Second filter differential pressure detecting device 20, 20K Case body 21, 21K Case base 21a One end outer surface 22, 22K Peripheral wall 30, 30K Movable body unit 31 Movable body 35 Coil spring 37 Permanent magnet 40 Movable body installation space 41 First space 42 Second space 50, 50K Magnetic sensor unit 52 Hall element 53 Detector 54 Power supply voltage terminal 55 Ground terminal 56 Output terminal 100 Filter device 110 Filter head 111 Body 112 Inlet port 113 Outlet ports 116A to 116C Inflow paths 117A and 117B Outflow paths 130 Element assembly 140 Element case 150 Filter element 152 Filter media

Claims (8)

The fluid introduced into the filter case through the primary flow path formed in the filter case passes through the filter element housed in the filter case, and the secondary flow path formed in the filter case A filter differential pressure detecting device for detecting a differential pressure of fluid pressure in the primary side flow path and the secondary side flow path in the filter device flowing out through the filter device,
A case body having therein a movable body arrangement space connected to the primary side flow path and the secondary side flow path,
The movable body arrangement space is divided into a first space communicating with the primary side flow path and a second space communicating with the secondary side flow path, and is provided so as to be movable in the movable body arrangement space, A movable body that moves according to the differential pressure;
An urging body provided in the first space or the second space to urge the movable body in a moving direction, and to regulate a moving amount of the movable body that moves in accordance with the differential pressure;
A permanent magnet provided on the movable body,
A magnetic sensor held at a predetermined position of the case body and sensing a magnetic field at the predetermined position by the magnet,
A detection unit that obtains the differential pressure based on the strength of the magnetic field sensed by the magnetic sensor.   The detection unit obtains a position of the movable body provided with the magnet based on the strength of the magnetic field sensed by the magnetic sensor, and obtains an urging force by the urging body based on the obtained position. The filter differential pressure detecting device according to claim 1, wherein the differential pressure is obtained.   The filter differential pressure detecting device according to claim 1, wherein the filter body is configured to be mounted on the filter case with a part of the case body fitted into the filter case. 4.   The case body has a case base having the movable body arrangement space therein, and a cylindrical peripheral wall provided at one end of the case base to surround an outer surface of one end of the case base. The filter differential pressure detecting device according to any one of claims 1 to 3, wherein the magnetic sensor is arranged on an outer surface of the one end portion.   The filter differential pressure detecting device according to claim 4, wherein the case base is formed of a non-magnetic material, and the peripheral wall is formed of a magnetic material and is detachably attached to the case base.   The filter differential pressure detecting device according to claim 4, wherein the case base and the peripheral wall are integrally formed of a non-magnetic material.   The detection unit is configured to output a signal of a level corresponding to the obtained differential pressure, and to output a signal of a predetermined level during operation of the magnetic sensor even when the differential pressure is 0 or less. The filter differential pressure detecting device according to claim 1, wherein: The case body is characterized in that a porous sintered metal body is provided at a portion connecting the first space and the primary flow path and at a portion connecting the second space and the secondary flow path. The filter differential pressure detecting device according to claim 1.

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