JPH048307Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel filter used in a fuel supply system of an engine or the like.

[Prior Art] For example, in a fuel filter installed in the fuel supply path of a diesel engine vehicle, the filter element may become clogged with wax precipitated from the fuel at low temperatures, making it difficult for the fuel to flow through the engine. This can easily lead to poor health.

As a measure to eliminate such inconveniences, fuel is supplied according to the usage environment, but when the temperature exceeds the usage limit, clogging of the filter element is still unavoidable.

For this reason, devices equipped with a built-in heater to heat the fuel have been developed. As a prior art related to such a fuel filter with a built-in heater, as shown in Japanese Utility Model Application Publication No. 1983-43666,
A head cover main body having a fuel introduction path and a fuel exit path, a filter cartridge having a built-in filter element and detachably attached to the head cover, a heater for heating the fuel provided in the fuel introduction path, Some devices include a temperature sensor attached to a portion of the fuel introduction path near the heater, and energization to the heater is turned on and off based on the detection result of the temperature sensor.

[Problems to be Solved by the Invention] However, in conventional fuel filters including the above device, power supply control to the fuel heater is performed by a single heater control device that operates based on a signal from the temperature sensor. It is now being done by In this case, since the fuel heating capacity of the heater is constant, if the capacity of the heater is set so as to satisfy a request for rapid fuel heating during a cold start, the value becomes considerably large.
On the other hand, in order to prevent chattering from occurring in the energization of the heater, it is necessary to set the hysteresis related to the switching to a certain degree of wide range. For this reason, in conventional systems, there is a wide operating range in which electricity continues to be applied to the large-capacity heater even though fuel is flowing normally, resulting in poor battery charging and discharging balance. There is this inconvenience.

The present invention aims to prevent the precipitation of fuel wax at low temperatures and to effectively eliminate the above-mentioned disadvantages with a simple structure.

[Means for Solving the Problems] In order to achieve such an object, the present invention includes a main heater and a sub-heater for heating fuel disposed in a fuel introduction path located upstream of a filter element, and a main bimetal that stops energizing the main heater when the temperature of the fuel flowing through the fuel introduction path exceeds an upper limit set value and resumes energizing the main heater when the temperature falls below the lower limit set value; has an upper limit set value in a temperature range lower than the upper limit set value and has a lower limit set value in a temperature range lower than the lower limit set value, and energizes the subheater when the temperature of the fuel exceeds the upper limit set value; and a sub-bimetal that restarts energization to the sub-heater when the lower limit setting value is exceeded, and the hysteresis of the sub-bimetal is maintained in a state where both the main heater and the sub-heater are operating. Based on the difference between the fuel temperature at the stage when the power supply to the sub-heater is cut off and the heating state is switched to only by the main heater, and the fuel temperature at the stage when the transient drop in fuel temperature is prevented by the heating effect of only the main heater. It is also characterized by a wide range of settings.

[Operation] According to such a configuration, when the temperature of the fuel is extremely low, such as during a cold start, the fuel flowing through the fuel introduction path is heated by the main heater and the sub-heater. Then, when the temperature of the heated fuel exceeds the upper limit setting value of the subheater, the subheater control means stops energizing the subheater. Since the lower limit set value of the main bimetal is set higher than the lower limit set value of the sub-bimetal, the fuel temperature will not be controlled by the main heater alone after that unless the fuel temperature falls below a predetermined value due to an engine stop, etc. It is done. However, since both the main heater and the sub-heater are controlled on and off by bimetals, there is no risk that the control device will become complicated. Moreover, since the hysteresis of the sub-bimetal is set as described above, even if the power to the sub-heater is cut off from the rapid heating state using both heaters and the temperature of the fuel drops, the power to the sub-heater will not be turned on again. There is no problem of starting and causing chattering. Therefore, even though simple bimetallic ON/OFF control is performed, it is possible to smoothly and appropriately control the fuel temperature.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

A fuel filter 1 according to the present invention is interposed in a fuel path passing through a fuel tank and a fuel injection pump of a diesel engine.

This fuel filter 1 has a filter cartridge 3 removably attached to a lower surface 4 of a head cover 2. The head cover 2 is block-shaped,
A priming pump 6 for increasing and decreasing the volume of the pump chamber 5 is provided on the upper part thereof, and a fuel introduction path 7 and a fuel derivation path 8 are provided inside. Fuel introduction route 7
a fuel introduction port 9 that guides fuel F introduced from the outside to the pump chamber 5 via a check valve (not shown); a heater chamber that communicates with the pump chamber 5 and the pump chamber 5 via a port 11; 12, and a terminal port 13 communicating with the heater chamber 12. The terminal port 13 opens at the lower end of a filter cartridge mounting portion 14 that projects from the center of the lower end of the head cover 2. The heater chamber 12 includes two main heaters (PTC elements) 15 and a single sub-heater (PTC element) for heating the fuel F passing through the fuel introduction path 7.
element) 16 are arranged. This main heater 1
The upper end electrodes of the main heater 15 and the sub heater 16 are connected to the (-) side terminal of the battery 20 via the partition wall 18 between the pump chamber 5 and the heater chamber 12, which forms an electrode plate. It is connected to the (+) side electrode of the battery 20 via a bimetal 19. The main bimetal 19 is configured so that a movable contact 22 held by a heat-sensitive deformable plate 21 can be brought into contact with and separated from a fixed contact 23 for ON/OFF operation.The movable contact 22 is connected to a conductive spring 24 and an electrode The fixed contact 23 is connected to the lower electrode of the main heater 15 via a plate 25.
is connected to the (+) side electrode of the battery 20 via a lead wire 26. In this main bimetal 19, when the temperature of the fuel F exceeds the upper limit set value _A1 , the movable contact 22 separates from the fixed contact 23 and becomes OFF, and the temperature of the fuel F rises to the lower limit set value _A2. , the movable contact 22 comes into contact with the fixed contact 23.
It is set to switch to the ON state. On the other hand, the lower electrode of the sub-heater 16 is connected to the (+) side electrode of the battery 20 via the sub-bimetal 27 and the main bimetal 19.
The sub bimetal 27 is the main bimetal 19
It has a similar configuration, and is set to turn OFF when the temperature of fuel F exceeds the upper limit set value B ₁ , and turn ON when the temperature of fuel F falls below the lower limit set value B ₂ . It has been set. Note that the upper limit setting value A ₁ of the main bimetal 19 is set higher than the upper limit setting value B ₁ of the sub-bimetal 27, and the lower limit setting value A ₂ of the main bimetal 19 is also the lower limit setting of the sub-bimetal 27. It is set higher than the value _B2 . Furthermore, the hysteresis H of the sub-bimetal 27 is set to be wider than the temperature difference Δt of the fuel F between when the main heater 15 and the sub-heater 16 are both operating and when only the main heater 15 is operating. (See Figure 4). To be more specific, the solid line a in FIG. 4 shows the variation in fuel temperature in this example. The broken line b shows the change in fuel temperature assuming that both the main heater 15 and the sub-heater 16 continue to be energized, and the dashed line c shows the change in fuel temperature when the sub-heater 16 is not energized at all and only the main heater is energized. This shows the change in fuel temperature assuming that the fuel is heated by . As is clear from this drawing, the hysteresis H of the sub-bimetal 27 described above is caused by the main heater 15 only, when the main heater 15 and the sub-heater 16 are both in operation, and then the sub-heater 16 is de-energized. Fuel temperature in stage d when switching to heating state
B ₁ and then stage e where the transient drop in fuel temperature is prevented by the heating effect of only the main heater 15.
(The stage when the rate of change in fuel temperature goes from a negative value to zero)
It is set wider than the difference Δt between the fuel temperature and the fuel temperature.

On the other hand, the filter cartridge 3 is provided with a filter element 3 in a case 31 that is screwed onto the filter cartridge mounting portion 14 of the head cover 2.
2, the inner space 33 of the filter element 32 is communicated with the terminal port 13 of the fuel introduction path 7, and the outer space 34 of the filter element 32 is communicated with the fuel outlet path via the port 35. It is connected to 8. The fuel F discharged from the fuel outlet 36 of the fuel outlet path 8 to the outside of the fuel filter is sent to a fuel injection pump (not shown).

With such a configuration, the fuel F introduced into the fuel filter 1 is guided from the fuel introduction port 9 to the heater chamber 12 via the pump chamber 5. And here, the main heater 15 and the sub heater 1
6, or the fuel F heated only by the main heater 15 is guided into the filter cartridge 3 via the terminal port 13. Therefore, the heated fuel F when passing through the heater chamber 12 is prevented from depositing wax, so that it flows without clogging the filter element 32 in the filter cartridge 3 and leads to the fuel outlet path. 8 to the fuel injection pump.

Here, the main heater 15 and the sub heater 1
6 will be explained. When the temperature of the fuel F is lower than the temperature of the two bimetals 19,
If it is lower than the lower limit setting values A ₂ and B ₂ of 27,
Both of these bimetals 19 and 27 are maintained in the ON state. As a result, power is supplied to both the main heater 15 and the sub-heater 16, and the fuel F is heated with a large amount of heat. Therefore, the temperature of fuel F rapidly rises as shown in FIG. Then, when the temperature of this fuel F exceeds the upper limit setting value B ₁ of the sub-bimetal 27,
This sub-bimetal 27 switches to the OFF state,
Power to the sub-heater 16 is cut off. Therefore,
The fuel temperature decreases one step further, and thereafter, the temperature of the fuel F is mainly controlled by turning on and off only the main heater 15. That is, when the temperature of the fuel F exceeds the upper limit setting position _A1 of the main bimetal 19, the main bimetal 19 is switched OFF, the power supply to the main heater 15 is stopped, and the temperature of the fuel F is lowered. When the lower limit setting value _A2 of the main bimetal 19 is lowered, the main bimetal 19 turns on and the main heater 1
5 is restarted. In a normal case, this operation is repeated as necessary, and the temperature control of the fuel F is continued. In addition, due to circumstances such as a temporary stoppage of the element or an extremely low outside temperature and insufficient capacity of the main heater 15, the temperature of the fuel F has fallen below the lower limit set values A ₂ and B ₂ of both bimetals 19 and 27. In this case, not only the main heater 15 but also
Of course, power supply to the sub-heater 16 is also restarted.

Therefore, if the fuel temperature is extremely low, such as during a cold start,
Electric power is supplied to both the main heater 15 and the sub-heater 16, and the fuel F is quickly heated.
When the temperature of the fuel F rises to a certain degree and the operating state is such that heat reception from the engine can be expected, the fuel temperature is maintained and managed by controlling the energization only to the main heater 15, and the wax failure occurs. from occurring. Therefore, the burden on the battery 20 can be reduced and the charging/discharging balance of the battery 20 can be improved.

Furthermore, in this device, the hysteresis H of the sub-bimetal 27 is set to be wider than the temperature difference Δt described above, so it is possible to prevent the inconvenience of chattering occurring in the ON/OFF control of the sub-heater 16 by the sub-bimetal 27. . Therefore, the sub-heater 16 is energized only at the minimum necessary time, such as at the initial stage of a cold start, and it is also possible to prevent the battery 20 from being unduly discharged.

Note that the number of main heaters and sub-heaters is of course not limited to those in the above embodiments,
For example, a plurality of sub-heaters may be provided, and these sub-heaters may be individually controlled by sub-heater control means having different upper limit settings.

[Effects of the invention] Since the present invention has the above-described configuration, it is possible to quickly and appropriately heat the fuel and effectively prevent clogging of the filter element due to wax precipitation. , it is possible to provide a fuel filter that can reasonably reduce the power supply to the heater. In particular, in the present invention, the hysteresis of the sub-bimetal is set as described above, so even if the power is cut off to the sub-heater and the fuel temperature drops from the rapid heating state using both heaters, the sub-heater will restart again. There is no problem of chattering caused by the start of energization. Therefore, it is possible to limit the power supply to the sub-heater to the minimum period necessary, and even though ON/OFF control is performed using a simple bimetal, it is possible to control the fuel temperature smoothly and appropriately. At the same time, inappropriate discharge of the battery can be effectively prevented.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which FIG. 1 is a schematic vertical sectional view showing the upper half of the fuel filter, FIG. 2 is a sectional view taken along the line -- in FIG. 1, and FIG. 3 is a heater and heater control means. 4th circuit explanatory diagram showing
The figure is an explanatory diagram of the action. 1...Fuel filter, 2...Head cover, 3
...Filter cartridge, 7...Fuel introduction route, 15...Main heater, 16...Sub heater, 19...Main bimetal, 27...Sub bimetal.

Claims (1)

[Scope of utility model registration request] A main heater and a sub-heater for heating fuel disposed in a fuel introduction path located upstream of the filter element, and a heater for heating the main heater when the temperature of the fuel flowing through the fuel introduction path exceeds an upper limit setting value. a main bimetal that restarts energization to the main heater when the energization is stopped and the lower limit set value is dropped; and the upper limit set value is in a temperature range lower than the upper limit set value and lower than the lower limit set value. A sub-sub which has a lower limit set value in a temperature range and stops energization to the sub-heater when the temperature of the fuel exceeds the upper limit set value, and restarts energization to the sub-heater when the temperature falls below the lower limit set value. bimetal, and the hysteresis of the sub-bimetal is determined by the fuel temperature at a stage when the main heater and the sub-heater are both operating to a state in which electricity is cut off to the sub-heater and the heating state is switched to only by the main heater. A fuel filter characterized in that the fuel filter is set to be wider than the difference between the fuel temperature and the fuel temperature at a stage after which a transient decrease in fuel temperature is prevented by the heating effect of only the main heater.