Level metering device for a fuel tank of a motor vehicle

Description: TECHNICAL FIELD [Detailed description of the invention]

Filling level measuring device for automobile fuel tanks Background technology The present invention is the filling for a fuel tank of an automobile as described in the superordinate concept of claim 1. It relates to a level measuring device. This type of filling level measuring device is available in the Federal Republic of Germany Patent Application Publication No. 3. It is known based on the specification of 914637. This known filling level measuring device burns It has a measuring tube located inside the charge tank, which is the bottom of the fuel tank. Starting from, it extends to at least the maximum filling level of the fuel tank, and this Fuel is sent into the measuring tube. In addition, the filling level measuring device has a differential pressure sensor. Therefore, one of the measurement inputs of this differential pressure sensor is connected to the lower end of the measuring tube. The other measurement input of this differential pressure sensor is negative due to hydraulic pressure at the bottom of the fuel tank. It has been loaded. The measuring tube has an overflow opening, and this overflow opening Is located at least at the highest filling level of the fuel tank. Measuring tube, The current fuel tank is provided by an opening or valve located near the bottom of the fuel tank. It can be emptied to the height of the point filling level. The measuring tube has an overflow opening When filled with fuel , Differential pressure sensor when the measuring tube is emptied to the current filling level of the fuel tank The filling level can be measured by the evaluation device based on the difference in the output signals of. Inside the measuring tube Fuel can be supplied to and from the return line through this return line. Fuel that has not been consumed by the internal combustion engine of the vehicle is returned to the fuel tank and guided. To. The fuel flowing through the return line is heated depending on the situation, so it should be inside the measuring tube. There is a temperature difference between a certain fuel and the fuel in the fuel tank, and this temperature difference is the same. As a result, there is a difference between the density of fuel in the measuring pipe and the density of fuel in the fuel tank. This causes an error in the output signal of the differential pressure sensor. further A fuel supply system is also known, and in this known fuel supply system, an internal combustion engine Since there is no return pipeline from Seki to the fuel tank, known filling level measurement The device is unusable. Advantages of the invention For a fuel tank of an automobile according to the present invention as opposed to a known filling level measuring device. The filling level measuring device has the advantage that the fuel sent into the measuring tube is not warmed. And the advantage of being able to be used in fuel supply systems without return lines Have. The advantageous form and the modified embodiment of the filling level measuring apparatus according to the present invention are claimed in claim 2 and above. It is listed below. Drawing Two embodiments of the filling level measuring apparatus according to the present invention are shown in the drawings. It is explained in detail below. Figure 1 shows the filling tank placed in the fuel tank of an automobile. It is a figure which shows the 1st Example in the state which the measuring tube of a bell measuring apparatus is filled with fuel. Therefore, in Fig. 2, the measuring tube located in the fuel tank shows the current fuel in the fuel tank. It is a figure which shows the state which was emptied to the height of, and FIG. 3 has a filling level measuring device. It is a figure which shows the 2nd Example of the fuel tank. Description of Examples Each of FIGS. 1 to 3 shows one fuel tank 10 for an automobile. The fuel tank 10 may be made of metal or plastic. Fuel tank A filling level measuring device 12 is arranged in 10, and this filling level measuring device 12 works to detect the filling level of the fuel tank 10, and this filling level is It is displayed in a known format on a display 34 arranged within the vehicle driver's field of view. The filling level measuring device 12 is arranged in the fuel tank 10 and extends in the vertical direction. It has one measuring tube 14, and the cross section of this measuring tube 14 is the side of the fuel tank 10. Remarkably small compared to the cross section. Is the measuring tube 14 made of, for example, plastic or metal? This fuel tank 1 may consist of the fuel tank 1 starting from the bottom 16 of the fuel tank 10. It extends to the vicinity of the ceiling 18 of 0. The measuring tube 14 is located near the upper end 20 thereof. It also has an overflow opening 22 that opens into the fuel tank 10. Further, the filling level measuring device 12 is a differential pressure sensor 2 arranged in the fuel tank 10. Has 4. This differential pressure sensor 24 has two measurement inputs 26 and 28. In this case, one measurement input unit 26 is connected to the lower end portion 30 of the measurement tube 14. Loaded by the hydrostatic pressure of the hydraulic column in the measuring tube 14 Has been done. The other measurement input unit 28 of the differential pressure sensor 24 is the bottom of the fuel tank 10. Connected to 16, thereby hydrostatic of the hydraulic column in the fuel tank 10. Loaded by pressure. The signal output unit of the differential pressure sensor 24 is in contact with the evaluation device 32. Continued, the indicator 34 is controlled again by this evaluation device 32. Differential pressure It is possible to use a micromachine pressure sensor, which is particularly inexpensive, as the sensor 24. It is profitable. A supply device 40 is arranged in the fuel tank 10, and the supply device 40 The fuel is sent from the fuel tank 10 to the injection device 44 of the internal combustion engine 46 of the automobile. To. The feeder 40 has a pump portion 41 and a drive portion 42, which drive the pump portion 41 and the drive portion 42. It is advantageous that the portion 42 is configured as an electric motor. The supply device 40 is detailed. It is held in the fuel tank 10 in a format not shown and burns in this case. A pot 48 can be provided in the charge tank 10, and a supply device is provided from this pot 48. 40 is sucking up fuel. By this pot 48, the supply device 40 is fueled. Sufficient fuel can be delivered even when the filling level of the ink 10 is low. Is guaranteed. Fuel tank 1 by jet pump or another pump Can be sent from 0 into pot 48. The supply device 40 is always operated with a uniform supply output when the internal combustion engine 46 is operated. Instead, the operation of the supply device 40 is performed by the internal combustion engine 46 in the current operating state. The amount of fuel consumed is controlled so that it is supplied by this supply device 40. Can be adjusted. For this purpose, it is supplied to the drive portion 42 of the supply device 40. The power or the voltage applied to this drive portion 42 can be changed. Supply device 4 0, mustThis operation is controlled in relation to the principal amount, consumption by the internal combustion engine 46 There is no need to return the unused fuel into the fuel tank 10. Supply device 40 Selectively in the fuel tank 10 for this operation, which is controlled in relation to the required amount A pressure regulator 45 can also be placed, which is located on the pressure side of the supply device 40. The connected inlet and the outlet connected to the injection device 44 of the internal combustion engine 46, It has a return pipe 47 that opens into the fuel tank 10. By pressure regulator 45 At least a nearly constant fuel pressure is adjusted within the injector 44. this Also in the configuration, from the internal combustion engine 46 to the fuel tank 10. No return pipeline is required. Fuel the pressure regulator 45 with, for example, the supply device 40 Can be held in tank 10 or as illustrated in Figure 1 fuel The opening 36 of the tank 10 can also be held by the closing lid 38. From the pressure side of the supply device 40, the fuel line 50 is connected to the injection device 44. It is derived. From the fuel line 50 or on the pressure side of the supply device 40, eg supply Another fuel line 54 branches directly from the connecting pipe piece 52 of the device 40, and this other fuel The toll line 54 is located near the lower end 30 of the measuring tube 14 of the filling level measuring device 12. It is open into the measuring tube 14 of. The fuel line 54 that opens into the measuring tube 14 It has a cross section that is much smaller than the fuel line 50 leading to the injection device 44. .. For this reason, the fuel pipeline 54 that opens into the measuring pipe 14 leads to the injection device 44. Since it is narrowed down compared to the fuel line 50, the measuring tube 1 is displayed from the supply device 40. A much larger amount of fuel is sent to the injector 44 than into 4. Supply device 40 is luck When rolled, the supply device 40 injects fuel through the fuel line 50. It is sent to the station 44, and fuel is sent into the measuring tube 14 via the fuel line 54. This In the case of, the measuring tube 14 is filled with fuel and this process is illustrated in Figure 1. So, it continues until the fuel reaches the height lo of the overflow opening 22. Inside the measuring tube 14 More fuel is supplied to In that case, the fuel flows out into the fuel tank 10 again through the overflow opening 22. To. For this reason, when the supply device 40 is in operation, the specified height lo is set in the measuring tube 14. A fuel column is generated, and this fuel column exerts a specified hydrostatic pressure. It is generated in the first measurement input unit 26 of the sensor 24. Second measurement input of differential pressure sensor 24 The force 28 is generated by a fuel column having a fuel height h in the fuel tank 10. It is loaded by the hydrostatic pressure applied. Fuel column in fuel tank 10 The current height h of is the filling level of the fuel tank 10. Therefore, the differential pressure sensor The output signal u (t) of the cell 24 is the hydrostatic pressure in the measuring tube 14 and the fuel tank. It is proportional to the difference from the hydrostatic pressure in the box 10. Output signal of differential pressure sensor 24 No. u (t) is sent to the evaluation device 32, which causes the evaluation device 32 to: Detect the output signal h (t) shown in the equation:<img file="JP2001511258A_D0001.tif" />In this case, g is the gravitational acceleration, ρ is the fuel density, and k is the transmission of the differential pressure sensor. Reach coefficient (sensitivity). For uo, the height of the hydraulic column in the measuring tube 14 is the fuel tank 10. It is an output signal of the differential pressure sensor for a state equal to the height h of the fuel inside. Supply device This condition occurs when the 40 is not operated. In this case, the measuring tube 14 has a height. From the state of fuel up to the overflow opening 22 in lo, it is illustrated in FIG. So, fuel tank 10 Empty up to the current height h of fuel inside. 1 and 2 show the filling level measuring device 12 based on the first embodiment. In this first embodiment, the fuel is measured when the supply device 40 is stopped. Outflow from the fixed pipe 14 through the fuel line 54 and the supply device 40 into the fuel tank 10. Can be Optionally, the measuring tube 14 is near its lower end 30 or The fuel line 54 can also have a small opening 56, through which the fuel can be fueled. Can flow out of the measuring tube 14 into the fuel tank 10. Opening in this case 56 is the supply device 40 during the operation of the supply device 40 within a predetermined time. Only less fuel than is sent into the measuring tube 14 by means of this opening 56 It is sized so that it cannot flow through. Opening 56 or providing measuring tube 14 By connecting to the fuel tank 10 via the feeder 40, the inside of the measuring tube 14 Due to the principle of communication pipes, fuel having the same height h as in the fuel tank 10 is produced. Is done. The output signal uo given in this state of the differential pressure sensor 24 is this output signal. Produces an offset of uo. This offset is the useful life of the differential pressure sensor 24. During that time, it undergoes some drift that impairs the accuracy of filling level measurements. this The offset is taken into account by the evaluator 32 based on the equation above, so the filling check There is no error when measuring the bell. Output signal of differential pressure sensor 24 uo can be detected each time after the supply device 40 is stopped, and the evaluation device 32 Can be memorized in. As a result, the output signal is output each time after the supply device 40 is stopped. The numbers stored for issue uo can be updated. By evaluation device 32 The detected filling level signal h (t) is continuously shown on a display device (not shown). Will be done. FIG. 3 shows the filling level measuring device 12 according to the second embodiment. In this case, the basic structure is the same as that of the first embodiment. Unlike the first embodiment, the supply device A valve 60 is located in the fuel line 54 between the station 40 and the measuring tube 14. This valve 6 0 is the first position shown by the solid line in FIG. 3 and the chain line shown in FIG. It is switchable between the second position and in the first position this valve 60 is the measuring tube 14 Is connected to the supply device 40 via the fuel line 54, and in the second position this valve 60 Opens the fuel line 54 and connects the measuring tube 14 to the fuel tank 10. Valve 60 May be formed as an electrically switchable solenoid valve. Valve 60 Switching between both positions can be controlled by the evaluation device 32. Normal In the form of valve 60, the measuring tube 14 is connected to the supply device 40 when the supply device 40 is in operation. Because it is in the first position where it is filled up to height lo with fuel The fuel tank 10 is currently filled with the differential pressure sensor 24 and the evaluation device 32. The bell can be detected. At predetermined time intervals, the valve 60 fuels the measuring tube 14. Connected to the link 10 to enable the detection of the output signal uo of the differential pressure sensor 24, and This switches to a second position to compensate for zero drift. Valve 6 This switching of 0 is when the internal combustion engine 46 is stationary when the supply device 40 is stopped. Not only that, it can be performed while the supply device 40 is in operation. Optionally, the valve 60 opens the fuel line 54 at one position by the valve 60. , The fuel line 54 may be formed so as to be cut off at the other position. This place In the fuel line 54 between the valve 60 and the measuring tube 14, as in the first embodiment. , Or in the area of the lower end 30 of the measuring tube 14, emptying this measuring tube 14 An opening 56 is provided to enable this.