JP2971095B2 - Fuel injection two-stroke engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection type two-stroke engine of a crankcase preload type that detects an intake air amount from a crankcase pressure to determine a fuel injection amount. It is.

BACKGROUND OF THE INVENTION The applicant of the present application has already proposed a fuel injection device for a crankcase preload type two-stroke engine in which an intake air amount is obtained from a fluctuation in a crankcase pressure and a fuel injection amount is determined (Japanese Patent Application Laid-open No. Sho. Nos. 58-98632 and 59-5875). Here, in these existing proposals, the pressure sensor for detecting the pressure in the crankcase is directly fixed to the crankcase, or fixed to the body side of the vehicle body, and the crankcase is communicated with the pressure guiding tube. When the pressure sensor is directly fixed to the crankcase as in the former case, there is a problem that the pressure sensor is greatly affected by the pressure fluctuation due to the rotation of the crank web of the crankshaft, and the accuracy of the pressure detection is reduced.

Further, when a pressure detection sensor is mounted on the body side of the vehicle and is connected to the crank chamber and the impulse line, not only the lubricating oil enters the impulse line but also the response is poor due to the volume in the impulse line. As a result, there is a problem that highly accurate pressure detection cannot be performed.

(Object of the Invention) The present invention has been made in view of such circumstances,
An object of the present invention is to provide a fuel injection type two-stroke engine that is less susceptible to pressure fluctuations in crank chamber pressure due to rotation of a crankshaft, and that improves detection response of crank chamber pressure and can increase detection accuracy. And

(Constitution of the Invention) According to the present invention, an object of the present invention is to provide a fuel injection type two-stroke engine which detects an intake air amount from a crank chamber pressure to determine a fuel injection amount, and a pressure sensor for detecting a crank chamber pressure is provided in a crankcase. The pressure sensor at the tip of the pressure sensor is arranged so as to be substantially continuous with the inner surface of the crank chamber from between two opposing crank webs with a connecting rod connected to the crank shaft interposed therebetween and to face the crank chamber. This is achieved by a fuel injection type two-cycle engine.

The same object is also provided in a fuel injection type two-stroke engine which detects an intake air amount from a crank chamber pressure to determine a fuel injection amount, and a pressure sensor for detecting a crank chamber pressure is mounted on a scavenging passage of a cylinder. A fuel injection type two-stroke engine characterized in that a pressure-sensitive portion at the tip is substantially continuous with an inner surface of the scavenging passage and faces the scavenging passage.
Is also achieved by

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

In these figures, reference numeral 10 denotes a crankcase preload two-cycle two-cylinder engine, 12 denotes a cylinder, 14 denotes a piston,
16 is a spark plug, 18 is a crankcase, 20 is a crankshaft, 22
Is a connecting rod. A crank chamber 24 is formed in the crank case 18. The crankshaft 20 is provided with crank webs 20a and 20b opposed to each other across the connecting rod 22 of each cylinder, and the connecting rod 22 is connected to a crankpin connecting the crank webs 20a and 20b.

Reference numeral 26 denotes 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-like valve body 26a as a throttle valve is attached to the throttle body 26, and the valve body 26a
Move diagonally within 32. The upper portion of the valve body 26a is connected to the pivot end of the lever 26b by a link 26c. Lever 26
b rotates in conjunction with a throttle operation mechanism such as an accelerator pedal or an accelerator grip, and eventually the valve element 26a is opened and closed by the throttle operation mechanism.

34 is an exhaust port, and 36 is an exhaust passage. At the upper edge of the exhaust passage 36, a substantially thread-wound exhaust control valve 37 with a portion cut away is provided.
The exhaust timing is variable by the rotation of the exhaust control valve 37. For example, the timing is controlled by a servomotor so as to advance or delay the opening timing of the exhaust port 34 in response to an increase or decrease in the rotation speed of the engine.

38 is an exhaust port, and this exhaust port 38 is an exhaust passage.
40 communicates with the crank chamber 24.

42 is a fuel tank, 44 is a strainer for removing dust in the fuel, and 46 is an electric fuel pump. Numeral 48 denotes an electromagnetic fuel injection valve to which fuel pumped from a fuel pump 46 is supplied. Reference numeral 50 denotes a pressure regulator which keeps a constant fuel pressure fed from the fuel pump 44 to the injection valve 48. That is, when the fuel pressure supplied from the fuel pump 46 to the injection valve 48 becomes equal to or higher than a predetermined pressure, the pressure regulator 50 opens and a part of the fuel is returned to the fuel tank 42 via the pipe 52.

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

As shown in FIG. 2, each pressure sensor 56 is mounted via a heat insulating material 56a such that a stainless steel plate for detecting the pressure faces the crank chambers 24, 24 of each cylinder of the crank case 18. That is, the pressure sensor 56 is
After fixing the holder 56b to the crankcase 18 with the heat insulating material 56a interposed therebetween,
Fixed at d. Here, the pressure sensing portion 56f of the pressure sensor 56 faces the inside of the crank chamber 24 from the opening 18A provided in the crankcase 18, and the pressure sensing portion 56f is substantially continuous with the surface of the crank chamber.
The washer 56e of the bolt 56 is also made of heat insulating material. As a result, the pressure sensor 56 is in a state of being thermally disconnected from the crankcase 18.

The pressure sensor 56 detects the internal pressure P of the crank chamber 24 from the displacement of the stainless steel plate, and outputs an electric signal whose voltage changes in response to the change of the internal pressure P, that is, a pressure signal p. 58 is a potentiometer for detecting the throttle valve opening 開, which detects the throttle valve opening か ら from the rotation angle of the lever 26b.

Numeral 60 denotes a control device constituted by a digital operation device.
The control device 60 stores the fuel injection amount M according to the operating condition in a memory in advance, and uses the pressure signal p output from the pressure sensor 56 and the rotation speed N of the crankshaft 20 to optimize the operating condition. The fuel injection amount M is calculated using the data in the memory. Then, an injection signal I indicating an injection time width corresponding to the 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 opens at a predetermined timing for a predetermined time width according to the signal I, and injects the fuel of the injection amount M.

Here the control device 60, and the intake air temperature T _a determined from the temperature sensor 74 provided in the throttle body 26, such as engine temperature T _b obtained by the temperature sensor 76 provided in the cylinder head, the information indicating the other operating conditions The injection amount M may be corrected.

Next, the operation of this embodiment will be described. When the internal pressure of the crank chamber 24 decreases due to the rise of the piston 14, the intake air flows from the intake passage 32 into the crank chamber 24 via 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 with the intake air to form a mixture, and this mixture flows into the crank chamber 24. . When the piston 14 descends, the air-fuel mixture is pre-pressurized in the crank chamber 24. Here, the internal pressure P of the crank chamber 24 corresponds to the amount of intake air and changes substantially in synchronization with the rotation of the crankshaft 20. The internal pressure P is detected by the pressure sensor 56, while obtaining the peak value P _m or variation Δp of the output p during one cycle, the rotational speed N may detect and determine the amount of intake air. The control device 60 obtains the injection amount M according to the operating condition at this time using the data in the memory.

According to this embodiment, since the pressure-sensitive portion of the pressure sensor 56 is disposed 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. In addition, 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 an embodiment in which a pressure sensor 56 is attached to the scavenging passage 40, in which pressure sensors 56 are attached to different positions of the scavenging passage in a 5-scavenging port type engine.

FIG. 3 shows the case where the pressure sensor 56 is attached to the first scavenging passage 40A, and FIG. 4 shows the case where the pressure sensor 56 is attached to the second scavenging passage 40B. 5 and 6 show the case where the pressure sensor 56 is attached to the third scavenging passage 40C, the one shown in FIG. 5 is parallel to the bending direction of the scavenging passage 40C, and the one shown in FIG. 6 is orthogonal to the bending direction. It was attached. According to FIG. 6, the influence of dynamic pressure due to the flow of scavenging gas in the curved scavenging passage 40C can be reduced.

According to these embodiments of FIGS.
Is far from the crankshaft 20, the influence of the fluctuation of the internal pressure of the crank chamber 24 due to the rotation of the crankshaft 20 is reduced.

7 to 9 are sectional views showing various embodiments of the structure for mounting the pressure sensor 56 to the cylinder 12. FIG. In FIG. 7, a holder 106 is attached to a cylinder 12 by a bolt 104 having a heat insulating washer 102 via a heat insulating material 100. In FIG. 8, the heat insulating material 100A is extended into the gap between the cylinder 12 and the pressure sensor 56. In FIG. 9, the O-ring 108 is sandwiched in the gap between the cylinder 12 and the pressure sensor 56A to provide heat insulation and improve sealing performance.

As in the above embodiment, if the pressure sensors 56, 56A are attached via the heat insulating materials 100, 100A, etc., the pressure sensors 56, 56A
Thus, it is possible to prevent the heat of the engine from being transmitted to the pressure sensor 56 and prevent the pressure sensor 56 from lowering the detection accuracy due to the engine heat.

(Effect of the Invention) As described above, according to the invention of claim (1), the pressure-sensitive portion at the tip of the pressure sensor for detecting the pressure in the crank chamber is cranked from between two crank webs opposed to each other across the connecting rod of each cylinder. Since the vehicle faces the crank chamber almost continuously to the indoor surface, it is less susceptible to the pressure fluctuation of the crank chamber pressure due to the rotation of the crank shaft, and the detection accuracy is improved.
Also, since the pressure sensor directly detects the crankcase pressure,
Good detection response.

According to the invention of claim (2), since the pressure sensor is attached to the scavenging passage, the pressure can be detected at a position far from the crankshaft, and is less affected by the rotation of the crankshaft, and has high accuracy 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 detecting portion is similarly far from the crankshaft, and is less affected by the rotation of the crankshaft. Therefore, the detection accuracy is improved, and the response is improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of one embodiment of the present invention, and FIG. 2 is a cross-sectional view including the vicinity of a pressure sensor mounting portion. 3 to 6 are plan views showing an embodiment in which the pressure sensor 56 is mounted at different positions of the scavenging passage in the 5-scavenging port type engine. 7 to 9 are sectional views showing various embodiments of the structure for mounting the pressure sensor 56 to the cylinder 12. FIG. 10 ... Engine, 12 ... Cylinder, 18 ... Crankcase, 18A ... Opening, 20 ... Crankshaft, 20a, 20b ... Crank web, 22 ... Connecting rod, 24 ... Crankcase, 40 ... Scavenging Passageway, 56, 56a …… Pressure sensor, 56f …… Pressure-sensitive part.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F02D 41/00-45/00 395 F02D 35/00

Claims (2)

(57) [Claims] 1. A fuel injection type two-stroke engine for detecting an intake air amount from a crank chamber pressure to determine a fuel injection amount. A pressure sensor for detecting a crank chamber pressure is mounted on a crankcase. A fuel injection type two-stroke engine characterized in that the pressure portion is substantially continuous with the inner surface of the crank chamber from between two crank webs opposed to each other across a connecting rod connected to a crank shaft and faces the crank chamber. 2. A fuel injection type two-stroke engine which detects an intake air amount from a crank chamber pressure to determine a fuel injection amount. A pressure sensor for detecting a crank chamber pressure is mounted on a scavenging passage of a cylinder. A fuel injection type two-stroke engine characterized in that the pressure-sensitive portion is substantially continuous with the inner surface of the scavenging passage and faces the scavenging passage.