Fuel pressure sensor

Abstract

To provide a fuel pressure sensor that can accurately detect fuel pressure.SOLUTION: A fuel pressure sensor is fitted to a fuel pipe while being separated from an inner wall of the fuel pipe and is positioned outside from the inner wall.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a fuel pressure sensor. [Background technology]

[0002] A fuel pressure sensor that detects the pressure of the fuel is provided in a pipe that supplies fuel to the fuel injection valve (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-275692 A Summary of the Invention [Problem to be solved by the invention]

[0004] It has been difficult to accurately detect the fuel pressure. Therefore, an object of the present invention is to provide a fuel pressure sensor capable of detecting the fuel pressure accurately. [Means for solving the problem]

[0005] The above object can be achieved by a fuel pressure sensor attached to a fuel pipe and spaced apart from and positioned outside an inner wall of the fuel pipe. Effect of the Invention

[0006] It is possible to provide a fuel pressure sensor capable of detecting the fuel pressure accurately. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram illustrating an engine system. [Diagram 2] Fig. 2(a) is a cross-sectional view illustrating an example of a fuel pressure sensor, and Fig. 2(b) is an enlarged view of a portion of the fuel pressure sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The fuel pressure sensor of the present embodiment will be described below with reference to the drawings. However, the dimensions and ratios of the various parts in the drawings may not be illustrated to be completely consistent with the actual ones. Also, some details may be omitted in the drawings.

[0009] 1 is a schematic diagram illustrating an engine system 100. The engine system 100 includes an internal combustion engine 10, a fuel pump 16, an ECU (Electronic Control Unit) 20, and a fuel pressure sensor 30.

[0010] The internal combustion engine 10 is a gasoline engine, a diesel engine, or the like. The fuel is, for example, gasoline, diesel, alcohol, or the like. An intake passage (not shown) and an exhaust passage (not shown) are connected to the internal combustion engine 10. The internal combustion engine 10 has, for example, four cylinders. Air that has passed through the intake passage is supplied to the cylinders.

[0011] A fuel injection valve 12 is provided in each of the four cylinders of the internal combustion engine 10. The four fuel injection valves 12 are connected to a fuel pipe 14 (common rail). A fuel pump 16 is connected to the fuel pipe 14. The fuel pump 16 pumps fuel from a fuel tank (not shown) and supplies it to the fuel pipe 14. The fuel is injected from the fuel injection valve 12 into the cylinder. A mixture of fuel and air is generated in a combustion chamber formed in the cylinder. The mixture is burned to generate power. Exhaust gas generated by the combustion is discharged from an exhaust passage.

[0012] The fuel pipe 14 is provided with a fuel pressure sensor 30. An air flow meter 22 is provided in an intake passage (not shown). An air-fuel ratio sensor 24 is provided in an exhaust passage. The fuel pressure sensor 30 detects the pressure of the fuel in the fuel pipe 14. The air flow meter 22 detects the flow rate of air. The air-fuel ratio sensor 24 detects the air-fuel ratio.

[0013] The ECU 20 includes a calculation device such as a CPU (Central Processing Unit) and storage devices such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The ECU 20 is electrically connected to the fuel pump 16, an air flow meter 22, an air-fuel ratio sensor 24, and a fuel pressure sensor 30. The ECU 20 acquires the air flow rate detected by the air flow meter 22 and the air-fuel ratio detected by the air-fuel ratio sensor 24. The ECU 20 acquires the fuel pressure detected by the fuel pressure sensor 30.

[0014] The ECU 20 controls the fuel pump 16 and the fuel injection valve 12 based on the air flow rate, the air-fuel ratio, the fuel pressure, etc. The ECU 20 controls the discharge amount of the fuel pump 16 and the injection time from the fuel injection valve 12, thereby controlling the amount of fuel injected. The air-fuel ratio is determined according to the amount of fuel injected.

[0015] The ECU 20 controls the fuel injection amount so that the air-fuel ratio becomes the target value. For example, when the air-fuel ratio detected by the air-fuel ratio sensor 24 differs from the target value, the ECU 20 determines a learning value. The ECU 20 adjusts the fuel injection amount based on the learning value to set the air-fuel ratio to the target value.

[0016] Table 1 shows an example of the learned values ​​of the air-fuel ratio. For example, learned values ​​A1 to A7 are set for each of the air flow rates G1 to G7. [Table 1]

[0017] FIG. 2(a) is a cross-sectional view illustrating an example of a fuel pressure sensor 30. FIG. 2(b) is an enlarged view of a portion of the fuel pressure sensor 30. As shown in FIG. 2(a), the fuel pressure sensor 30 has a mounting portion 32 and a sensor portion 34. The mounting portion 32 is formed of metal, plastic, or the like, and has, for example, a cylindrical shape. The sensor portion 34 is a portion that detects the fuel pressure, and is provided inside the mounting portion 32. The mounting portion 32 has a passage 36. The passage 36 extends from a tip end 32a of the mounting portion 32 to the sensor portion 34. Fuel enters the passage 36 and flows to the sensor portion 34. The sensor portion 34 detects the fuel pressure.

[0018] A hole 42 is provided in the fuel pipe 14. The hole 42 penetrates the wall of the fuel pipe 14. The mounting portion 32 is inserted into the hole 42. As shown in Figures 2(a) and 2(b), the tip 32a of the mounting portion 32 is spaced from the inner wall 40 of the fuel pipe 14 and is located outside the inner wall 40. The distance between the tip 32a and the inner wall 40 is L. The distance L is greater than 0. The sensor portion 34 is spaced from the tip 32a and the inner wall 40. The diameter of the hole 42 is D. The diameter D is constant along the extension direction of the hole 42.

[0019] If the fuel pressure sensor protrudes into the inside of the fuel pipe 14, or if the hole 42 has a narrowed portion (a portion with a small diameter), it is difficult to detect the fuel pressure accurately. If the fuel pressure acquired by the ECU 20 differs from the actual fuel pressure, the ECU 20 controls the fuel injection amount based on the incorrect fuel pressure. It is difficult to set the air-fuel ratio to the target value.

[0020] According to this embodiment, the tip 32a of the fuel pressure sensor 30 does not protrude into the fuel pipe 14, but is located outside the inner wall 40. The flow of fuel is not easily hindered by the fuel pressure sensor 30. Accurate fuel pressure can be detected. For example, the pulsating pressure and average pressure of the fuel can be detected.

[0021] The distance L between the tip 32a of the fuel pressure sensor 30 and the inner wall 40 is determined based on, for example, the kinetic viscosity coefficient v of the fuel, the flow rate u of the fuel, and the diameter D of the hole 42. As an example, the distance L is set to be equal to or greater than √(V×D / 2÷u). The greater the kinetic viscosity coefficient v and the diameter D, the greater the distance L. The smaller the flow rate u of the fuel, the greater the distance L.

[0022] The diameter D of the hole 42 is constant in the direction in which the hole 42 extends, and does not have any narrowed portions. This suppresses changes in fuel pressure due to changes in diameter, and allows accurate detection of fuel pressure.

[0023] The ECU 20 obtains an accurate fuel pressure and controls the fuel injection amount based on the fuel pressure, thereby enabling precise control of the fuel injection amount and the air-fuel ratio.

[0024] Although a preferred embodiment of the present invention has been described in detail above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0025] 10 internal combustion engine, 12 fuel injector, 14 fuel pipe, 16 fuel pump, 20 ECU, 22 air flow meter, 24 air-fuel ratio sensor, 30 fuel pressure sensor, 32 mounting portion, 32a tip portion, 34 sensor portion, 36 passage, 40 inner wall, 42 hole, 100 engine system

Claims

[Claim 1] Attached to the fuel pipe, a fuel pressure sensor located outside and spaced apart from an inner wall of the fuel pipe;

Images