JPH045442A - Fuel injection type two-cycle engine - Google Patents

Abstract

PURPOSE:To improve the detecting accuracy by putting the pressure sensing unit of a pressure sensor for detecting internal pressure of a crank chamber between two crank webs of a crank shaft, thereby allowing the pressure sensor to be less subject to the effect of changes in internal pressure of the crank chamber with the rotation of the crank shaft. CONSTITUTION:A pressure sensor 56 for detecting internal pressure P of a crank chamber 24 is mounted on a crankcase 18. The pressure sensing unit of the pressure sensor 56 is put into between two crank webs of the crank shaft 20. The crank webs thus are not rotated in proximity to the pressure sensor 56, and thereby detection errors of the pressure sensor 56 due to the rotation of the crank shaft 20 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a crank chamber pre-pressure type fuel injection type two-stroke engine which determines the fuel injection amount by detecting the intake air amount from the crank chamber pressure. It is.

(Background of the Invention) The applicant of the present application has already proposed a fuel injection device for a crank chamber preload type two-stroke engine that determines the amount of intake air from changes in crank chamber pressure and determines the amount of fuel injection. 58-98632, 59-5875, etc.)
. In these existing proposals, the pressure sensor that detects the pressure in the crank chamber is fixed directly to the crankcase, or
It was fixed to the vehicle body side and communicated with the crank chamber through a pressure impulse pipe. In the case where the pressure sensor is directly fixed to the crankcase as in the former case, there is a problem in that the pressure sensor is greatly affected by pressure fluctuations due to the rotation of the crank web of the crankshaft, resulting in a decrease in pressure detection accuracy.

In addition, when a pressure detection sensor is installed on the car body pod side and communicated with the crank chamber through a pressure pipe, not only does lubricant oil enter the pressure pipe, but the volume of the pressure pipe causes poor response. However, there was still a problem that highly accurate pressure detection was not possible.

(Objective of the Invention) The present invention has been made in view of the above circumstances, and it is an object of the present invention to improve the detection responsiveness of the crank chamber pressure in response to the influence of pressure fluctuations in the crank chamber pressure due to the rotation of the crankshaft. It is an object of the present invention to provide a fuel injection type two-stroke engine that can improve detection accuracy.

(Structure of the Invention) According to the present invention, in a fuel injection type two-stroke engine that determines the fuel injection amount by detecting the intake air amount from the crank chamber pressure, a pressure sensor for detecting the crank chamber pressure is installed in the crankcase. This is achieved by mounting the pressure sensor on a fuel-injected two-stroke engine characterized in that the pressure-sensitive part of the pressure sensor faces between two crank webs of the crankshaft.

The same object also includes a fuel injection two-stroke engine, which is characterized in that a pressure sensor for detecting crank chamber pressure is attached to the scavenging passage of the cylinder, and the pressure sensitive part of the pressure sensor is disposed within the scavenging passage. This can also be achieved by

Furthermore, the same purpose is to provide a fuel injection type two-stroke engine that is located close to the upstream side of the reed valve in a fuel injection type two-cycle engine that determines the fuel injection amount by detecting the amount of intake air taken into the crank chamber through the reed valve from the crank chamber pressure. This can also be achieved by a fuel-injected two-stroke engine, which is characterized by being equipped with a pressure sensor.

(Embodiment) FIG. 1 is an overall configuration diagram of an embodiment of the present invention, and FIG. 2 is a sectional view including the vicinity of a pressure sensor mounting portion.

In these figures, reference numeral 10 is a two-stroke, two-cylinder engine with preloaded crank chamber, 12 is a sill, 14 is a piston, 16 is a spark plug, 18 is a crankcase, 20 is a crankshaft, and 22 is a connecting rod. crank case 18
A crank chamber 24 is formed inside.

26 is a throttle body, the downstream side of which is connected to an intake port 30 via a reed valve 28 as a one-way valve. A plate-shaped valve body 26a as a throttle valve is attached to this throttle body 26, and this valve body 26a
moves obliquely forward and backward into the intake passage 32. This valve body 26a
The upper part of the lever 26b is connected to the rotating end of the lever 26b by a link 26c. The lever 26b rotates in conjunction with a throttle operating mechanism such as an accelerator pedal or an accelerator grip, and the valve body 26a is eventually opened and closed by the throttle operating mechanism.

34 is an exhaust port, and 36 is an exhaust passage. Exhaust passage 3
An approximately pincushion-shaped exhaust control valve 37 with a portion cut out is attached to the upper edge of the exhaust valve 6, and the exhaust timing is made variable by rotating the exhaust control valve 37. For example, it is controlled by a servo motor to advance or delay the opening timing of the exhaust port 34 in response to an increase or decrease in the rotational speed of the engine.

38 is a scavenging port, and this scavenging port 38 communicates with the crank chamber 24 through a scavenging passage 40.

42 is a fuel tank, 44 is a strainer for removing dust from the fuel, and 46 is an electric fuel pump. Reference numeral 48 denotes an electromagnetic fuel injection valve, and fuel pumped from the fuel pump 46 is supplied to this injection valve 48. Reference numeral 50 denotes a pressure regulator that keeps the pressure of the fuel fed from the fuel pump 44 to the injection valve 48 constant. That is, when the fuel pressure supplied from the fuel pump 46 to the injection valve 48 exceeds a predetermined pressure,
Pressure regulator 50 opens to allow a portion of the fuel to flow back into fuel tank 42 via vibrator 52 .

Reference numeral 56 denotes a pressure sensor attached to the crankcase 18, and a thin stainless steel plate serving as a pressure sensing portion at the tip faces the gap formed between the crank webs 20a and 20b of each cylinder. The pressure sensor 56 used here has a closed space defined by a thin stainless steel plate that serves as a pressure sensitive part facing the crank chamber 24, and this closed space is filled with silicone oil to detect the displacement of the thin stainless steel plate through the silicone oil. It has a structure in which the pressure is detected by a semiconductor pressure sensor.

As shown in FIG. 2, each pressure sensor 56 is attached via a heat insulating material 56a so that a thin stainless steel plate for detecting the pressure faces the crank chamber 24, 24 of each cylinder of the crankcase 18. That is, this pressure sensor 56 is
After being screwed into the holder 56b and fixed with a lock nut 56C, the holder 56b is fixed to the crankcase 18 with a bolt 56d with the heat insulating material 56a in between. Here, the washer 56e of the bolt 56 is also made of a heat insulating material. As a result, the pressure sensor 56 is thermally isolated from the crankcase 18.

This pressure sensor 56 detects the internal pressure P of the crank chamber 24 from the displacement of the thin stainless steel plate, and outputs an electrical signal whose voltage changes in response to changes in the internal pressure P, that is, a pressure signal p. 58 is a potentiometer that detects the throttle valve opening e, and detects the throttle valve opening e from the rotation angle of the lever 26b.

60 is a control device composed of a digital arithmetic unit.

This control device 60 stores in advance a fuel injection amount M corresponding to the operating conditions in a memory, and uses the pressure signal p output from the pressure sensor 56 and the rotational speed N of the crankshaft 20 to determine the optimum fuel injection amount M for the operating conditions. The fuel injection amount M is calculated using data in the memory. Then, an injection signal (2) indicating an injection time width corresponding to this injection amount M is sent to the injection valve 48 in synchronization with the rotation angle θ of the crankshaft 20. The electromagnetic solenoid of the injection valve 48 is opened at a predetermined timing for a predetermined time width by this signal, and injects an injection amount M of fuel.

Here, the control device 60 calculates the intake air temperature T obtained from the temperature sensor 74 provided in the throttle body 26.

Alternatively, the injection amount M may be corrected using information indicating other operating conditions, such as the engine temperature T determined by a temperature sensor 76 provided in the cylinder head.

Next, the operation of this embodiment will be explained. When the internal pressure of the crank chamber 24 decreases due to the rise of the piston 14, the intake passage 32
Intake air flows into the crank chamber 24 through the reed valve 28. Since a predetermined amount of fuel is injected from the fuel injection valve 48 in synchronization with the rotation of the crankshaft 20, the fuel is mixed into the intake air to form a mixture, and this mixture flows into the crank chamber 24. . When the piston 14 descends, this air-fuel mixture is pre-pressurized within the crank chamber 24. Here, the internal pressure P of the crank chamber 24 corresponds to the amount of intake air, and
It changes almost in synchronization with the rotation of 0. This internal pressure P is detected by the pressure sensor 56, and the output p during one cycle is
While determining the peak value p1 or the variation amount Δp, the rotational speed N is also detected to determine the amount of intake air. The control device 60 determines the injection amount M in accordance with the driving situation at this time by using the memory.

According to this embodiment, since the pressure sensitive part of the pressure sensor 56 is arranged so as to face the gap between the crank webs 20a and 20b, the crank webs 20a and 20b do not rotate close to the pressure sensor 56. , the detection error of the pressure sensor 56 due to the rotation of the crankshaft 20 is reduced.

3 to 6 are plan views showing embodiments in which pressure sensors 56 are attached to the scavenging passage 40, and these are plan views showing examples in which pressure sensors 56 are installed in the scavenging passage 40.
This is the one with the .

The pressure sensor 56 in FIG. 3 is attached to the first scavenging passage 40A, and the pressure sensor 56 in FIG. 4 is attached to the second scavenging passage 40B. Figure 5.6 shows the third scavenging passage 40C.
A pressure sensor 56 is attached to the scavenging passage 40C, in which the pressure sensor 56 is attached parallel to the curved direction of the scavenging passage 40C in the one shown in FIG. 5, and perpendicular to the curved direction in the one shown in FIG. This sixth
According to the diagram, it is possible to make the curved scavenging passage 40C less susceptible to the influence of dynamic pressure due to the flow of scavenging air.

According to the embodiments of these FIGS. 3-6, the pressure sensor 56
Since the pressure sensing portion is located far from the crankshaft 20, the influence of fluctuations in the internal pressure of the crank chamber 24 due to rotation of the crankshaft 20 is reduced.

7-9 are cross-sectional views showing various embodiments of the structure for mounting the pressure sensor 56 to the sill 12. In the one shown in FIG. 7, a holder 106 is attached to the sill 12 by a bolt 104 with a heat insulating washer 102 via a heat insulating material 100. In the one shown in FIG. 8, the heat insulating material 100A extends into the gap between the sill 12 and the pressure sensor 56. The one in Figure 9 is a shilling 12 and a pressure sensor 56A.
An O-ring 108 is inserted into the gap between the two to provide heat insulation and improve sealing performance.

As in the above embodiment, if the pressure sensor 56.56A is installed through the heat insulating material 100.100A, etc., the heat of the engine will be difficult to be transmitted to the pressure sensor 56.56A, and the pressure sensor 56 will be affected by the engine heat. can be prevented from decreasing.

The pressure sensor 56 may be provided not only in the crankcase 18 and the scavenging passage 40 as described above, but also in a position close to the upstream side of the reed valve 28. In this case, the pressure sensor 56B may be provided in the throttle body 26, which is separate from the crankcase 18, as shown by the imaginary line in FIG. 1, and the heat of the crankcase 18 will not be directly transmitted to the pressure sensor 56B. Therefore, the pressure sensor 56B is less susceptible to the effects of engine heat, and its pressure detection accuracy is further improved.

(Effects of the Invention) As described above, the invention of claim (1) is arranged such that the pressure sensitive part of the pressure sensor for detecting the crank chamber pressure faces between the crank webs, so that the crank chamber pressure due to the rotation of the crankshaft is controlled. is less susceptible to pressure fluctuations, improving detection accuracy. Furthermore, since the pressure sensor directly detects the crank chamber pressure, the detection response is good.

According to the invention of claim (2), since the pressure sensor is attached to the scavenging road, the pressure can be detected at a position far from the crankshaft, and it is less affected by the rotation of the crankshaft, resulting in high precision and high responsiveness. detection is possible.

According to the invention of claim (3), since the pressure sensor is mounted close to the upstream side of the reed valve, the pressure detection section is likewise far away from the crankshaft and is less susceptible to the influence of the rotation of the crankshaft. This improves detection accuracy and responsiveness.

(Margin below)

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention, and FIG. 2 is a sectional view including the vicinity of a pressure sensor mounting portion. 3 to 6 are plan views showing embodiments in which pressure sensors 56 are attached to different positions of the scavenging passage in a five-scavenging bottom type engine. 7 to 9 are cross-sectional views showing various embodiments of the structure of the mounting of the pressure sensor 56 on the sill 2. 10...engine, I2...schilling, 24...
...Crank chamber, 28...Reed valve, 40...Scavenging passage, 56.56A...Pressure sensor, patent applicant
Yamaha Motor Co., Ltd.

Claims (3)

[Claims] (1) In a fuel injection type two-stroke engine that determines the fuel injection amount by detecting the intake air amount from the crank chamber pressure, a pressure sensor that detects the crank chamber pressure is attached to the crankcase, and the pressure sensing part of this pressure sensor is connected to the crank case. A fuel-injected two-stroke engine characterized by being placed between the two crank webs of the shaft. (2) In a fuel injection type two-stroke engine that determines the fuel injection amount by detecting the intake air amount from the crank chamber pressure, a pressure sensor that detects the crank chamber pressure is installed in the scavenging passage of the cylinder, and the pressure sensing part of this pressure sensor A fuel-injected two-stroke engine characterized by having a scavenging passage facing into the scavenging passage. (3) In a fuel injection type two-stroke engine that determines the fuel injection amount by detecting the amount of intake air sucked into the crank chamber through a reed valve from the crank chamber pressure, a pressure sensor is provided adjacent to the upstream side of the reed valve. A fuel injection type two-stroke engine characterized by being equipped with a sensor.