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 Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[0005] The above object can be achieved by a fuel pressure sensor A sensor unit for detecting the pressure of the fuel inside, and a housing for the sensor unit that is inserted into a hole penetrating the inner wall of the fuel pipe, thereby connecting the sensor unit to the fuel pipe. attached It comprises a mounting portion, the mounting portion having a tip on the fuel piping side and a fuel passage extending from the tip to the sensor portion, and the diameter of the hole is constant in the direction in which the hole extends. The tip portion is located inside the hole, separated from Outward by a predetermined distance along the direction in which the hole extends the inner wall doing of the fuel pipe.

Effects of the Invention

[0006] A fuel pressure sensor capable of detecting an accurate fuel pressure can be provided.

Brief Description of the Drawings

[0007] [Figure 1] FIG. 1 is a schematic diagram illustrating an engine system. [Figure 2]Figure 2(a) is a cross-sectional view illustrating a fuel pressure sensor. Figure 2(b) is an enlarged view of a part of the fuel pressure sensor. [Modes for carrying out the invention]

[0008] The fuel pressure sensor of this embodiment will be described below with reference to the drawings. However, the dimensions and proportions of each part in the drawings may not perfectly match those of the actual parts. Also, some details may be omitted in the drawings.

[0009] Figure 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, etc. The fuel is, for example, gasoline, diesel fuel, alcohol, etc. The internal combustion engine 10 is connected to an intake passage and an exhaust passage, not shown. The internal combustion engine 10 has, for example, four cylinders. Air passing through the intake passage is supplied to the cylinders.

[0011] Each of the four cylinders of the internal combustion engine 10 is equipped with a fuel injector 12. The four fuel injectors 12 are connected to a fuel line 14 (common rail). A fuel pump 16 is connected to the fuel line 14. The fuel pump 16 draws fuel from a fuel tank (not shown) and supplies it to the fuel line 14. Fuel is injected from the fuel injectors 12 into the cylinders. A mixture of fuel and air is generated in the combustion chamber formed in the cylinder. Power is generated by the combustion of this mixture. Exhaust gas generated by combustion is discharged through the exhaust passage.

[0012] A fuel pressure sensor 30 is provided in the fuel line 14. An airflow meter 22 is provided in the intake passage (not shown). An air-fuel ratio sensor 24 is provided in the exhaust passage. The fuel pressure sensor 30 detects the fuel pressure in the fuel line 14. The airflow meter 22 detects the airflow rate. The air-fuel ratio sensor 24 detects the air-fuel ratio.

[0013] The ECU20 includes a processing unit such as a CPU (Central Processing Unit), and storage devices such as RAM (Random Access Memory) and ROM (Read Only Memory). The ECU20 is electrically connected to the fuel pump 16, airflow meter 22, air-fuel ratio sensor 24, and fuel pressure sensor 30. The ECU20 acquires the airflow rate detected by the airflow meter 22 and the air-fuel ratio detected by the air-fuel ratio sensor 24. The ECU20 also acquires the fuel pressure detected by the fuel pressure sensor 30.

[0014] The ECU 20 controls the fuel pump 16 and fuel injector 12 based on the airflow rate, air-fuel ratio, fuel pressure, etc. The ECU 20 controls the discharge amount from the fuel pump 16 and the injection time from the fuel injector 12 to control 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 reaches the target value. For example, if the air-fuel ratio detected by the air-fuel ratio sensor 24 differs from the target value, the ECU 20 determines a learned value. Based on the learned value, the ECU 20 adjusts the fuel injection amount to bring the air-fuel ratio to the target value.

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

[0017] FIG. 2(a) is a cross-sectional view illustrating the fuel pressure sensor 30. FIG. 2(b) is an enlarged view of a part 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, etc., 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 the tip 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 FIGS. 2(a) and 2(b), the tip 32a of the mounting portion 32 is spaced apart from the inner wall 40 of the fuel pipe 14 and is located outside the inner wall 40. Let the distance between the tip 32a and the inner wall 40 be L. The distance L is greater than 0. The sensor portion 34 is spaced apart from the tip 32a and the inner wall 40. Let the diameter of the hole 42 be D. Along the extending direction of the hole 42, the diameter D is constant.

[0019] When the fuel pressure sensor protrudes inside the fuel pipe 14 and there is a constricted portion (a portion with a small diameter) in the hole 42, it is difficult to accurately detect the fuel pressure. When the fuel pressure acquired by the ECU 20 is different 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 the present embodiment, the tip 32a of the fuel pressure sensor 30 does not protrude to the inside of the fuel pipe 14 and is located outside the inner wall 40. The fuel flow is less likely to be obstructed by the fuel pressure sensor 30. Accurate fuel pressure can be detected. For example, the pulsating pressure and the 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, for example, based on the kinematic viscosity coefficient v of the fuel, the fuel flow rate u, and the diameter D of the hole 42. As an example, the distance L is set to be greater than or equal to √(V × D / 2 ÷ u). The larger the kinematic viscosity coefficient v and the diameter D, the larger the distance L should be. The smaller the fuel flow rate u, the larger the distance L should be.

[0022] The diameter D of the hole 42 is constant in the direction of extension of the hole 42 and does not have a constricted portion. Changes in fuel pressure due to changes in diameter are suppressed. Accurate fuel pressure can be detected.

[0023] The ECU20 obtains accurate fuel pressure and controls the fuel injection amount based on that pressure. It can also control the fuel injection amount and air-fuel ratio with high precision.

[0024] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of Symbols]

[0025] 10 Internal combustion engine, 12 Fuel injector, 14 Fuel piping, 16 Fuel pump, 20 ECU, 22 Airflow meter, 24 Air-fuel ratio sensor, 30 Fuel pressure sensor, 32 Mounting section, 32a Tip section, 34 Sensor section, 36 Passage, 40 Inner wall, 42 Hole, 100 Engine system

Claims

[Claim 1] A sensor unit that detects the fuel pressure in the fuel line, The system includes a mounting portion which houses the sensor portion and is inserted into a hole that penetrates the inner wall of the fuel pipe, thereby attaching the sensor portion to the fuel pipe. The mounting portion has a tip on the fuel piping side and a fuel passage extending from the tip to the sensor portion. The diameter of the hole is constant in the direction in which the hole extends. The tip portion is spaced outward by a predetermined distance from the inner wall of the hole in the direction in which the hole extends. Fuel pressure sensor.

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