JPS62277115A - Heating system for fuel - Google Patents

Abstract

PURPOSE:To compact a heating system so as to facilitate the handling thereof and to facilitate the action such as maintenance and inspection by incorporating a heater, a switch and a sensor in one housing. CONSTITUTION:Fuel is passed through an inlet pipe 107 of fuel and a nipple 106 and introduced into an inlet port 101 by the action of a fuel pump and entered to diaphragm chamber 105 by pushing and opening the suction part 111 of a valve mechanism 110 and introduced into an upstream fuel passage 102 by pushing and opening the discharge part 112 of the valve mechanism 110. Fuel is passed through a heating system 500 and introduced into a downstream fuel passage 103 and filtered in filter elements 202 and thereafter allowed to flow to the outside through an outlet port 104. Further, a negative-pressure sensor 150 indirectly detects the amount of wax incorporated in fuel, when the amount of wax is reached to the prescribed value and above and thereby the clogging starts to be caused in filter elements 204, both a movable contact 171 and a fixed contact 172 are closed to heat a heating element 141.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention is attached to a fuel filter device provided in a vehicle equipped with a diesel engine, for example, and heats the fuel in the filter. Regarding equipment.

[Conventional technology]

Diesel engine fuel, ie, light oil, begins to solidify into a waxy state when the temperature reaches a low temperature range of −10° C. or lower, which may clog the filter element.

Such clogging may impede fuel supply to the engine and may worsen the operating condition of the engine. Therefore, it is necessary to heat the fuel at low temperatures.
JP-A-59-190462, JP-A-59-224
Japanese Patent No. 463 discloses a configuration in which a heater made of a positive characteristic semiconductor is provided in a fuel passage of a fuel filter device, and the heater heats the fuel to melt wax components.

[Problem that the invention seeks to solve]

The conventional fuel heating device described above has a problem in that the switch and the heater are provided in separate locations, making the entire device large.

[Means for solving problems]

A fuel heating device according to the present invention includes a housing in which a fuel passage through which fuel passes is formed, a heater facing into the fuel passage and generating heat when energized, a power source for supplying electric power to the heater, and A switch provided in an electric circuit connecting a power source and a heater and housed in the housing, and a switch housed in the housing and connected to the switch detect the amount of wax in the fuel. The present invention is characterized by comprising a wax detection means that closes the switch when the wax exceeds a predetermined value.

〔Example〕

The present invention will be explained below with reference to illustrated embodiments.

FIG. 1 shows a fuel filter device equipped with a fuel heating device according to a first embodiment of the invention. In this figure, the fuel filter device includes a metal upper body 100, a filter &
[It is composed of a Z body 200, a level switch device 300, a hand pump 400, and an upper body 10.
0 is provided with a fuel heating device 500. The main parts of the filter assembly 200 include a metal case 201, an axial flow filter element 202, and a filter element 2.
A water reservoir space 203 is formed below 02. A cylindrical member 204 is provided at the axial center of the metal case 201,
Filter element 202 is fitted into this cylindrical member 204. Fuel flows into the space 203 from the inlet passage of the upper body 100 through the cylindrical member 204, is filtered while passing through the filter element 202, and flows out from the outlet passage of the upper body 100.

The upper body 100 includes an inlet boat 101, an upstream fuel passage 102, a downstream fuel passage 103, and an outlet boat 1-1.
A diaphragm chamber 105 is formed above the upper body 100 by the diaphragm 401 of the hand pump 400, and an outlet chamber 109 communicating with the output port 104 is formed below the upper body 100. A nipple 106 is installed at the entrance of the entrance boat 101.
is screwed onto the nipple 106, and a fuel inlet pipe 107 is fixed to the nipple 106. Accordingly, fuel flows into the artificial port 101 through the fuel manifold pipe 107 and the nipple 106 due to the action of the fuel pump (not shown), and the fuel flows into the manifold port 101 through the valve mechanism 110 which will be described later.
The fuel flows into the diaphragm chamber 105 by pushing open the suction part Ill of the fuel, and then pushes open the discharge part 112 of the valve mechanism 110 to flow into the upstream fuel passage 102. This fuel is heated by the heating device 500.
It flows into the downstream fuel passage 103 through the filter element 202, and then flows out from the outlet port 104.

2 and 3 show the structure of the valve mechanism 110 in detail. The valve mechanism 110 includes a valve member 118 and a support member 11.
It consists of 9. The valve member 118 is integrally formed by punching out spring steel, and includes a disc-shaped suction part 111 and a disc-shaped discharge part 112.
and a ring part 113, the suction part 111 and the ring part 113 are connected by a flexible plate part 114, and the discharge part 112 and the ring part 113 are connected by a flexible plate part 115, respectively. - The force support member 119 is integrally formed by punching out stainless steel by press molding, for example, and the force support member 119 is formed integrally with the valve member 1.
The stopper portion 116 facing the upper surface of the ring portion 18 and the ring portion 1
13 and a disk portion 117 that engages with the upper surface of the discharge portion 112
A through hole 117a is bored in the center of the disk portion 117.

These valve member 118 and support member 119 are assembled as shown in FIG. That is, the support member 119 places the stopper part 116 above the suction part 111 and the disc part 1.
17 is positioned above the discharge portion 112 and is placed above the valve member 118 . The assembly of the support member 119 and the valve member 118 is attached to the upper surface of the upper body 100 so that the suction part 111 closes the artificial port 101 and the discharge part 112 closes the upstream fuel passage 102 ( (See Figure 1). That is, the ring portion 113 and the disc portion 117 are fitted into the artificial portion 121 of the upstream fuel passage 102. The inner circumferential edge of the entrance portion 121 is crushed by a jig at multiple locations to form claws 122 that protrude inward, and these claws 122 fix the disc portion 117 and the ring portion 113 onto the upper body 100. be done. Thus, the suction portion 111 is deformed upward by the fuel pressure in the inlet boat 101 to open this port 101, so that fuel flows from the port 101 into the diaphragm chamber 105. Here, the amount of upward deformation of the suction section 111 is regulated by the stopper section 116. The discharge part 112 is deformed downward by the fuel pressure in the diaphragm chamber 105 and opens the upstream fuel passage 102, so that the fuel flows into the diaphragm chamber 10.
5 into the fuel passage 102.

As shown in FIG. 1, a hand pump 400 is provided in the upper part of the diaphragm chamber 105.
05 is isolated from the atmosphere by the diaphragm 401 of the hand pump 400. The diaphragm 401 is molded from a flexible material such as rubber, and the outer peripheral edge of the diaphragm 401 is connected to the upper end of the cylindrical wall 123 by a metal cover 402 fitted to the upper end of the cylindrical wall 123 of the upper body 100. Fixed. Also, the diaphragm 401 is a metal plate 40
3 and 404, and the metal plates 403 and 404 are fixed to the diaphragm 401 by fitting the tip of the metal attachment member 405.

The upper end of the mounting member 405 protrudes to the outside of the cover 402, and a cup-shaped operation member 411 made of resin is attached to this upper end with screws 410. This operating member 411
has a shape that covers the upper part of the cover 402, and a coil spring 412 is provided between the cover 402 and the laterally expanded portion so as to cover it. Therefore, when the operating member 405 is pushed by hand, the coil spring 412 is compressed, the mounting member 411 is lowered, and the diaphragm 401 is deflected. When you release your hand from the operating member 411, the coil spring 412 stretches and connects the mounting member 405 via the operating member 411.
rises, and the diaphragm 401 returns to its original state.

The reciprocating motion of the operating member 411 causes pressure fluctuations within the diaphragm chamber 105, which allows fuel to be supplied to the filter assembly 200 via the valve mechanism 110.

A fuel heating device 500 is provided in the upper body 100. FIG. 4 shows the structure of this heating device 500 in detail. In this figure, a cylindrical hole 131 is formed in the upper body 100 , and this hole 131 communicates with the diaphragm chamber 105 via an upstream fuel passage 102 , and communicates with the diaphragm chamber 105 via a downstream fuel passage 103 . It communicates with the shaped member 204 (FIG. 1). Further, a negative pressure passage 132 communicating with the outlet chamber 109 is bored below the hole 131 of the upper body 100.

A tube member 134 made of heat-resistant resin, that is, an insulating material, is fitted into the hole 133 that connects the negative pressure passage 132 and the hole 131. This tube member 134 protrudes into the hole 131, and an O-ring 135 for sealing is provided between the tube member 134 and the hole 133. A lower housing 151 of a negative pressure sensor 150 is located inside the cylindrical portion 136 formed at the upper part of the tube member 134.
A cylindrical spacer 137 made of heat-resistant resin, that is, an insulating material, is inserted into the hole 131 together with the O-ring 139 . Spacer 137 has a port 138 that communicates with downstream fuel passage 103. Thus, the annular chamber 140 is formed by the upper body 100, the spacer 137, the lower housing 151, and the tube member 134.
is formed. Upstream and downstream fuel passages 102.103
communicates with the annular chamber 140, but the negative pressure passage 132 does not communicate with the annular chamber 140, but communicates with the negative pressure sensor 150 via a passage 139 formed in the axial center of the tube member 134.

The annular chamber 140 houses an annular ceramic heating element 141 made of positive temperature coefficient (PTC) porcelain semiconductor material.

Electrodes 142 made of silver or the like and having a thickness of several microns to several tens of microns are welded to the upper and lower surfaces of this heating element 141, as shown in FIG. As shown in FIG. 7, these electrodes 142 are covered with metal washers 143 and 144 made of copper or the like having good electrical and thermal conductivity and having the same shape as the heating element 141. A second metal washer 145 is provided on the lower surface of washer 144 located further below. A suitable number of protrusions 146 having spherical tips are formed at the bottom of the hole 131. The second metal washer 145 is placed on top of these protrusions 146!
! A heating element 141 is provided thereon, sandwiched between metal washers 143,144. Upper metal washer 143 and lower housing 151 of negative pressure switch 150
A ring-shaped spring 147 is elastically installed between the two.

This spring 147 causes the metal washer 143°1
44, heating element 141 and second metal washer 145
are pressed together, and the second metal washer 145 is pressed against the protrusion 146. The protrusion 146 allows the second metal washer 145 to make good electrical contact with the upper body 100 and also allows the heat of the heating element 141 to be transferred to the upper body 100.
This will prevent them from escaping.

The housing of the negative pressure sensor 150 is a lower housing 15.
1 and an upper housing 153. The lower housing 151 has a large diameter portion 154 and a small diameter portion 155.
54 is fitted inside the spacer 137 together with the O ring 156, and the small diameter portion 155 is fitted together with the O ring 152 into the cylindrical part 136 of the tube member 134. The upper housing 153 is fitted and fixed inside the upper edge 157 of the large diameter portion 154 of the lower housing 151.

An annular support surface 158 is formed between the large diameter portion 154 and the small diameter portion 155 of the lower housing 151.
A disc member 161 is provided between 58 and the lower end of the upper housing 153. The diaphragm 162 is disposed below the disk member 161, and the outer peripheral edge of the diaphragm 162 is held between the ring member 163 provided on the support surface 158 and the disk member 161. A passage 139 of the tube member 134 and a negative pressure passage 1 are provided on the lower surface of the diaphragm 162.
32 leads to the pressure in the outlet chamber 109 of the filter assembly. That is, the diaphragm acts as a pressure sensor. Disc-shaped metal plate 164 that performs snap action
is fixed to the upper surface of the diaphragm 162, and the rod member 165 formed on the upper surface of this dish-shaped metal plate 164 is fixed to the upper surface of the diaphragm 162.
The disk member 16 is inserted through the hole 166 drilled in the hole 161.
Projects above 1. On the other hand, a dish-shaped resin plate 167 is provided below the diaphragm 161, and a spring 169 is provided between the resin plate 167 and an adjustment nut 168 screwed into the small diameter portion 155 of the lower housing 151.
As a result, it is always urged upward and comes into contact with the diaphragm 161.

A movable contact 171 and a fixed contact 172 are provided within the housing. The movable contact 171 and the fixed contact 172 have a material and size that can withstand a large current. The fixed contact 172 is formed at one end of a conductive metal connecting plate 173 provided on the disc member 161.
The other end is clamped and fixed by the lower end of the upper housing 153, the upper edge 157 of the lower housing 151, and the disc member 161. The fixed contact 172 is a conductive metal connecting plate 17 whose one end is fixed to the inner wall of the upper housing 153.
4 at the other end.

A rod member 165 comes into contact with the lower surface of this metal connecting plate 174, and as the rod member L65 moves up and down, the contacts 171, 172
opens and closes. That is, when substantially no negative pressure is introduced to the lower surface of the diaphragm 162, the diaphragm 162 is in the upper position due to the elastic force of the spring 169, and the rod member 16
5 rises and pushes up the metal connecting plate 174 to contact the contact 171.5.
172 is opened. On the other hand, the diaphragm 162
When a substantially negative pressure is introduced to the underside of the diaphragm 16
2 is in the downward position due to suction by this negative pressure, and the rod member 165 descends to displace the metal connecting plate 174 downward,
Contacts 171 and 172 are closed. A terminal 175 connected to the metal connecting plate 174 is coupled to a terminal 177 connected to a lead wire 176, and the lead wire 176 is connected to the positive terminal of a power source 181 (FIG. 5). Therefore, the power source 181, the contacts 171 and 172, and the heating element 141 are connected to the fifth
Electrically connected as shown, contacts 171.172
By closing, the heating element 141 is supplied with power and generates heat.

Note that the deep dish-shaped cover 182 is fixed to the upper body 100 with screws (not shown), covers the upper housing 153 and the terminals 175 and 177, and covers the lead wire 176.
extends from the cover 182 to the outside and is connected to the power source 181. This cover 182 prevents rainwater and the like from entering. Further, the operating pressure of the switch 150 can be adjusted using a NAND 1
This is done by rotating the spring 68 to change the elastic force of the spring 169.

Now, in FIG. 1, the level switch 'AM300 is equipped with a reed switch 303 using a float 302 with a magnet 301, and the base 304 of this level switch device 300 is connected to the case 201 of the filter assembly 200. It is attached to a nut portion 305 provided on the bottom wall. A drain plug 310 for draining water is attached to the base 304 of the level switch He3000. In addition,
When the drain plug 310 is slightly loosened from the base 304, the horizontal groove (not shown) communicates with the vertical groove 311, and the water reservoir space 203 communicates with the outside.

The operation of this embodiment will be explained.

By the action of the fuel pump, the fuel introduced into the present fuel filter device passes through the heating device 500 and then flows into the water storage space 203, and while staying in this space, it is heated due to the difference in specific gravity between water and fuel. Water sinks below the space 203 and is separated from the fuel. After water is separated from the fuel, the fuel is filtered and purified as it passes through the filter element 202 in the axial direction, and is led from the outlet boat 104 provided in the upper body 100 to the fuel pump and engine (not shown). .

When a certain amount of water settles in the water storage space 203, the float 302 of the level switch device 300 floats up and the magnet 301 turns the reed switch 303 into the ○N state. This activates a warning light or buzzer placed on an instrument panel or the like to warn the driver.

When a predetermined amount of water is detected, the drain plug 310 is turned to communicate the inside of the space 203 with the outside, and the hand pump 400
The operating member 411 is moved up and down to displace the diaphragm 404 and cause pressure fluctuations within the diaphragm chamber 105.

As a result, the discharge part 112 of the mechanism 110 is intermittently opened and pressure is applied to the water surface in the space 203, so that water is discharged through the mechanism 311 of the drain plug 310.

Incidentally, the hand pump 400 is used not only to drain drain water, but also to temporarily supply fuel into the filter assembly 200 when the filter assembly 200 is replaced with a new one.

Note that during normal operation, the interior of the hand pump 400 constitutes a part of the fuel system path, as described above.

On the other hand, when the temperature is low, wax is present in the fuel, and this wax causes the filter element 202 to become clogged. Accordingly, the negative pressure on the downstream side of the filter element increases, and when this negative pressure exceeds a predetermined value, the contacts 171 and 172 of the negative pressure sensor 150 come into contact, and the current flows through the lead wire 176, terminal 177, terminal 175, Contact 1
71, contact 172, connection plate 173, lower housing 15
4, spring 147, washer 143, heating element 14
1, washer 144, and washer 145 in this order. Therefore, the heating element 141 is energized and generates heat. While the fuel goes around the annular chamber 140, it is heated by the heating element 141, thereby melting not only the wax component in the fuel but also the wax component that is clogging the filter element 202. However, filter element 2
The negative pressure downstream of 02 decreases, which opens the contacts 171 and 172 of the negative pressure sensor 150, and the heating element 1
The power supply to 41 is stopped. In this way, negative pressure sensor 1
50 indirectly detects the amount of wax in the fuel,
When the amount of wax exceeds a predetermined value, filter element 2
02 starts to become clogged, the contacts 171 and 172 are closed to cause the heating element 141 to generate heat.

When this negative pressure sensor 150 is turned off, the filter element 202 begins to become clogged again due to the temperature of the fuel, and the above process is repeated until the fuel circuit reaches a temperature that melts the wax, but this has a negative impact on the engine. Since it operates only when there is a blockage, the amount of electricity used is kept to a minimum.

Further, in order to obtain high thermal efficiency, it is preferable that the heating element 141 be in direct contact with fuel, but if the electrode 142 comes into contact with moisture during energization, it will deteriorate or dissolve. Therefore, in this embodiment, the electrode 142 is covered with metal members 143 and 144 to form a sandwich structure as described above. Therefore, the electrode 142 is not exposed and comes into contact with moisture, and deterioration of the electrode 142 is prevented while maintaining high thermal efficiency.

Further, in this embodiment, a washer 145 is provided below the washer 144. Washer 1 like this
The effect of stacking 44.145 will be explained. The upper body 100 is preferably molded from aluminum in terms of moldability, conductivity, and cost. On the other hand, when the electrode 142 is formed by welding silver to the heating element 140, it is desirable that the washers 143 and 144 be made of copper, which has a small potential difference with respect to silver, in order to prevent electrolytic corrosion. However, the potential difference between copper and aluminum is large, and therefore, if the washer 144 and the protrusion 146 are brought into contact, there is a risk that electrolytic corrosion will occur.

Therefore, in this embodiment, the washer 144 and the protrusion 14 are
A washer 145 made of stainless steel or the like having a potential intermediate between that of copper and aluminum is inserted between the holes 6 and 6 to prevent electrolytic corrosion from occurring.

Also, in this embodiment, the lower housing 154 of the negative pressure switch 150 is used as a positive electrode with respect to the heating element 141, and the spring 147 causes the heating element 141 to
is pressed downward. With this structure, the connection between the positive electrode of the heating element 141 and the negative pressure sensor 150 can be omitted, and the structure is also simple.

Furthermore, the negative pressure sensor 150 of this embodiment has a snap-action dish-shaped metal plate 164 that allows the contacts 171.1 to
72 is turned ON and OFF instantly, and the contacts have a material and shape that can control large currents, so there is no need for relays, and there is no need for wiring between negative pressure sensors and relays, making it easy to use. It has a structure.

Note that in this embodiment, the heating element 141 and the washer 1
43 and 144 have a donut shape, but they may also have a disk shape. Also, the heating element 141 is made of a PTC semiconductor material that has a positive resistance temperature characteristic and whose resistance value increases rapidly at a specific temperature. However, the present invention is not limited thereto, and other known ceramic heating elements may be used.

FIG. 8 shows a second embodiment of a fuel heating device 500.

In this second embodiment, the washer 143 provided on the lower side of the heating element 141 is in direct contact with the hemispherical protrusion 146 formed on the upper body 100, as is clear from FIG. The second metal washer 145 provided in the embodiment is omitted. In addition, adhesive 18 is applied to the portion of the cover 182 from which the lead wire 176 protrudes.
3 is filled, thereby preventing water from entering the cover 182 and fixing the connection Fi 173. The other configurations are basically the same as those of the first embodiment.

This second embodiment can be adopted when the potential difference between the washer 143 and the protrusion 146 is not large enough to cause electrolytic corrosion, and the structure can be simpler than the first embodiment. Note that the operation of the second embodiment is the same as that of the first embodiment except for the operation of the second metal washer 145.

FIG. 1O shows a third embodiment of a fuel heating device 500. This third embodiment differs from the first and second embodiments in that a temperature sensor 650 is used instead of the negative pressure sensor,
Moreover, a dish-shaped bimetal 664 is provided in place of the dish-shaped metal plate 164. That is, the temperature sensor 650 detects the fuel temperature via the lower housing 151, and when this temperature is higher than a predetermined value, the bimetal 664 is bent upward to open the contacts 171 and 172 via the rod member 165, so that the temperature increases. When lower than a predetermined value, bimetal 664 flexes downward, closing contacts 171 and 172 via rod member 165. According to the third embodiment, however, there is no need to detect the negative pressure in the outlet chamber 109 of the filter assembly (therefore, there is no need for a passage, diaphragm, or pressure regulating mechanism to guide this negative pressure).

11 and 12 show a fourth embodiment of a fuel heating device 500. FIG. This fourth embodiment is different from the first embodiment shown in FIG. 4 in the configuration of the heating element, and the other configurations are basically the same. That is, 3 having the same shape
Heating elements 141a, 141b and 141c are provided in a stacked manner, and ring-shaped spacers 641a and 641b made of a conductive material are inserted between each heating element, respectively. These spacers 641a.

641b has approximately the same thickness as each heating element and has a smaller radial width than those heating elements. Therefore, the upper and lower surfaces of each heating element have a sufficiently large area in contact with the fuel, and the heating elements 141a, 141b, 141c are electrically connected in series, as clearly shown in FIG.

Although not shown in FIG. 11, the heating element 141a
, 141b, and 141c are each formed with an electrode and covered with a metal washer, and a metal washer provided on the lower surface of the lowermost heating element 141c is provided with a groove on the underside to prevent electrolytic corrosion. It is preferable that a second metal washer is provided as in FIG. 7.

In this configuration, three heating elements are connected in series.
Compared to a configuration in which heating elements 141a,
The diameters of 141b and 141c can be reduced,
Conversely, heating elements of the same diameter can improve fuel heating performance. Furthermore, the configuration of this embodiment increases the contact area with the fuel, so that the heating efficiency of the fuel can be improved.

Note that the number of heating elements is not limited to three, and may be increased or decreased as necessary.

13 and 14 show a fifth embodiment of a fuel heating device 500. FIG. This fifth embodiment is different from the fourth embodiment in that heating elements 141a, 141b, and L41c are electrically connected in parallel, and the other configurations are the same as the fourth embodiment. That is, the annular chamber 14 of the lower housing 151
A first cylindrical member 740 having an angular cross-section is fixed to the surface facing 0, and a second cylindrical member 741 having an angular cross-section and surrounding the first cylindrical member 740 is fixed to the upper surface of the protrusion 146. . Three heating elements 141a, 141b, 141c are arranged between the first and second cylindrical members 740,741. The outer peripheral surface of the first cylindrical member 740 has three
Positive electrode members 742a, 742b, 742c are provided, and two negative electrode members 743a, 743b which also serve as springs are provided on the inner peripheral surface of the second cylindrical member 741. The heating element 141a includes an electrode member 742a,
The heating element 141b is sandwiched between the electrode members 742b and 743b. heating element 14
1c is the electrode member 742C and the bottom 7 of the second cylindrical member 741.
41a.

Thus, each heating element 141a, 141b, 141c
are electrically connected in parallel as clearly shown in FIG. Further, the upper and lower surfaces of the heating elements 141a, 141b, and 141c are respectively formed with electrodes and covered with metal washers.

Also in this embodiment, each heating element 141a, 141b
.

Since the upper and lower surfaces of 141c are in contact with the fuel, the heating efficiency of the fuel is improved. Also a heating element 141a.

By electrically connecting 141b and 141c in parallel, the size of the heating element required to obtain a given heat capacity can be reduced, or alternatively, heating elements of the same size can be used to increase the heat capacity and increase the heating speed. It is possible to improve the

It goes without saying that the number of heating elements can be determined completely arbitrarily.

〔Effect of the invention〕

As described above, according to the present invention, since the heater, switch, and sensor are housed in one housing, the heating device becomes compact and easy to handle, and maintenance and inspection work becomes easier.

[Brief explanation of drawings]

1 is a partial sectional view showing a fuel filter device to which the first embodiment of the present invention is applied; FIG. 2 is an exploded perspective view of the valve mechanism; FIG. 3 is a perspective view of the valve mechanism; The figure is a sectional view showing the first embodiment, Figure 5 is an electric circuit diagram in the first embodiment, Figure 6 is a sectional view showing the heating element, and Figure 7 is an exploded perspective view of the heating element and metal washer. Figure 8 is a sectional view showing the second embodiment; Figure 9 is an exploded perspective view of the heating element and metal washer; Figure 10 is a sectional view showing the third embodiment; 12 is an electric circuit diagram of the fourth embodiment, FIG. 13 is a sectional view of the fifth embodiment, and FIG. 14 is an electric circuit diagram of the fifth embodiment. 100... Upper body, 141... Heating element (heater), 150... Negative pressure sensor (wax detection means)
, 171172... Contact, 181... Power supply, 2
00...Fuel filter assembly, 650...Temperature sensor (wax detection means). Figure 3 Figure 5 Figure 6 Figure 9 Figure 10

Claims (1)

[Claims] 1. A fuel heating device that is attached to a fuel filter assembly provided in the middle of a fuel supply path to an engine and heats fuel flowing through a filter element in the fuel filter assembly. , a housing in which a fuel passage through which fuel passes is formed, a heater that faces the fuel passage and generates heat when energized, a power source for supplying power to the heater, and an electric circuit that connects these power sources and the heater. a switch provided in the fuel and housed in the housing; and a switch housed in the housing and connected to the switch to detect the amount of wax in the fuel and detect the amount of wax when the amount of wax exceeds a predetermined value. A fuel heating device comprising: wax detection means for closing a switch. 2. The fuel heating device according to claim 1, wherein the heater is a ceramic heating element. 3. The fuel heating device according to claim 1, wherein the electrodes provided on both sides of the heater are each covered with a metal member. 4. One electrode of the heater is electrically connected to the housing, and a second metal member having an intermediate potential between the potential of the electrode and the potential of the housing is provided between the metal member covering the electrode and the housing. The fuel heating device according to claim 3, characterized in that: 5. The wax detection means is a negative pressure sensor that detects the pressure difference between upstream and downstream of the filter element, and this negative pressure sensor closes the switch when the downstream pressure becomes lower than the upstream pressure by a predetermined value or more. 2. The fuel heating device according to claim 1, wherein the fuel heating device is characterized in that: 6. The fuel according to claim 1, wherein the wax detection means is a temperature sensor that detects the fuel temperature, and this temperature sensor closes a switch when the fuel temperature becomes lower than a predetermined value. heating device.