JP2841798B2 - diesel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a diesel engine.

(Conventional technology and its problems) A diesel engine has a higher compression ratio than a spark ignition type engine and compresses a large amount of air near a full load even at a partial load, so that the blow-by gas blow-through amount is relatively large, Fuel efficiency tends to be greatly deteriorated due to an increase in compression loss. In a conventional diesel engine, generally, a plurality of compression rings are interposed between a piston and a cylinder to ensure sealing performance.

However, in order to reduce the friction and the inertial mass of the piston, there has been a demand for a single compression ring.

As a countermeasure for this, it is conceivable to improve the sealing performance by forming an uneven portion that closes the gap between the compression rings (see Japanese Patent Application Laid-Open No. 56-159534). However, an intake throttle valve is provided in the middle of the intake passage. In the case of a diesel engine that reduces a part of exhaust gas to the intake system to reduce NOx emission (see Japanese Utility Model Laid-Open No. 62-29453), the intake throttle valve closes and the intake pipe negative pressure increases greatly. There is a problem that a single compression ring increases the consumption of oil sucked through the abutment gap.

An object of the present invention is to solve such a conventional problem and unify a compression ring provided on a piston of a diesel engine.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, an intake throttle is interposed in an intake passage, and an exhaust recirculation passage communicating the intake passage and the exhaust passage downstream of the intake throttle is provided. In the diesel engine provided, a notch opening on the lower surface is formed at one of the ring ends opposed to each other with the opening gap therebetween, and a projection having a shape to supplement the notch is formed at the other end. One compression ring and an oil ring are interposed between the piston and the cylinder, and a negative pressure detecting means is provided in the intake passage, and a predetermined amount of oil consumption in which the intake pipe negative pressure is sucked to the combustion chamber side is sufficiently reduced. And a pressure control means for controlling the opening degree of the intake throttle valve based on the detected negative pressure so as to be equal to or less than the negative pressure value.

(Operation) During the compression / expansion process, the compression ring closes the gap at the bottom of the ring groove with a projection shaped to compensate for the notch, and a single compression ring sufficiently blows blow-by gas. Prevention and maintain fuel economy.

During the intake stroke, the protrusion of the compression ring separates from the bottom of the ring groove, and an oil gap that creates communication between the crank chamber and the combustion chamber is created by the gap between the openings.However, the opening of the intake throttle is adjusted to adjust the intake pipe load. Since the pressure control means for suppressing the pressure to a predetermined value or less is provided, the consumption of oil sucked into the combustion chamber by the single compression ring can be sufficiently reduced.

As a result, in a diesel engine having an exhaust gas recirculation device in which an intake throttle valve is interposed in the middle of the intake passage, it is possible to provide a single compression ring, reduce the friction and weight of the piston, and reduce the weight of the diesel engine. Performance is improved.

(Example) Hereinafter, an example of the present invention is described based on an accompanying drawing.

As shown in FIG. 1, the diesel engine has an intake pipe 52 for introducing intake air and an exhaust pipe 53 for discharging exhaust gas.
Is installed. The intake pipe 52 and the exhaust pipe 53 are connected to the EGR passage 5
EGR valve 5 which is connected by 5,56 and is provided in the middle
Opening / closing is controlled by 7. A throttle valve 59 is interposed in the ventilation pipe 52, and is driven by a diaphragm device 60. The negative pressure of the vacuum pump 58 driven by the engine 10 is sent to the pressure regulating valves 62 and 63 via the negative pressure passage 61, and the pressure regulating valves 62 and 63 reduce the negative pressure in accordance with a signal from the electronic control unit 68. Adjust the diaphragm device 6 through the negative pressure passages 64, 65
0 and the EGR valve 57 are respectively operated.

The electronic control unit 68 basically includes the fuel injection pump 54
Signals from an accelerator lever opening sensor 66 and a rotation sensor 67 provided in the controller are input, and the pressure adjustment values of the pressure adjustment valves 62 and 63 are calculated and output. As a result, the recirculation amount of the exhaust gas is controlled according to the preset EGR control map.

In FIG. 2, 16 is a cylinder head, 1 is a piston, 2 is a cylinder, and a cavity is provided at the top of the piston 1.
The fuel injection nozzle 12 is mounted facing the combustion chamber defined by the openings 11. 13 is an intake port, 14 is an intake valve, and 15 is a cam for driving the intake valve to open and close.

Between the piston 1 and the cylinder 2, an oil ring 3 for forming an appropriate lubricating oil film and a compression ring 4 for sealing the combustion chamber are individually provided.

As shown in FIG. 3, the front end of the right end of the ring forming the abutment gap 22 of the compression ring 4 is notched along the circumferential direction of the ring, and the left end of the ring is formed on the left end. A projection 24 is formed to compensate for the notch 23,
The abutment gap 22 is closed on the sliding surface side between the cylinder 24 and the cylinder wall.

The compression ring 4 has a projection 24 with a ring groove.
26 is incorporated so as to be located on the bottom surface 26a side.

As a result, as shown in FIGS. 4A and 4B, during the compression / expansion process in which the compression ring 4 is pressed against the bottom surface 26a of the ring groove 26, the projection 24 comes into close contact with the bottom surface 26a of the ring groove 26. As shown by the arrow in the figure, the gas leakage path between the upper combustion chamber and the crank chamber is formed by a notch 23
It is limited to only 24 small gaps, and the amount of blow-by gas blow-through can be reduced sufficiently.

On the other hand, as shown in FIGS. 5A and 5B, during the suction stroke, the compression ring 4
When pressed against b, the projection 24 separates from the bottom surface 26a of the ring groove 26, and the crank chamber and the combustion chamber communicate with each other through the opening gap 22. For this reason, in the operation state in which the intake throttle valve 59 is closed, the oil held between the piston 1 and the cylinder wall surface 27 passes through the opening gap 22 to the low-pressure combustion chamber side as shown by the arrow in the figure. There is a problem that the water is sucked up and the oil consumption increases.

Therefore, the present invention provides a pressure sensor downstream of the throttle valve 59 of the intake pipe 52 as control means for suppressing the suction negative pressure to a predetermined value or less.
The electronic control unit 68 is provided with the pressure sensor 69
Is configured to control the opening of the throttle valve 59 on the basis of the detection signal.

This control will be described with reference to the flowchart shown in FIG.

First, in step 1, the rotation speed N, the fuel injection amount Q, the water temperature
Tw and the intake pipe negative pressure P are read.

In steps 2, 3, 4, and 5, the water temperature Tw is after the warm-up of a predetermined value or more, the fuel injection amount Q is in a low-medium load region where the fuel injection amount Q is a predetermined value or less, and the rotation speed N is a low-medium speed where the rotation speed N is a predetermined value or less. After it is determined that the EGR valve 57 is open in the range, the process proceeds to step 6, and if the negative pressure P of the intake pipe 52 is equal to or less than the predetermined value, the process proceeds to step 7 to close the throttle valve 59. In other operating states, the routine proceeds to step 8, and the throttle valve 59 is opened.

FIG. 7 shows the results of an experiment in which the degree of change in the oil consumption in accordance with the intake pipe negative pressure was measured. In the case of this embodiment, as indicated by a broken line (TR3) in the figure, the intake pipe negative pressure is set to a predetermined value. It has the characteristic that the oil consumption increases sharply when it increases beyond. Therefore, by adjusting the opening of the throttle valve 59 based on the detection signal P of the pressure sensor 69 and maintaining the intake pipe negative pressure in a predetermined range, the oil consumption can be reduced. The maximum value of the intake pipe negative pressure regulated by this control is significantly smaller than that of a normal spark ignition gasoline engine. In FIG. 7, the characteristic indicated by the one-dot chain line (TR2) is the characteristic when the compression ring 4 is incorporated so that the projection 24 is located on the upper surface 26b side of the ring groove 26, and the solid line (TR1) The characteristic represented by parentheses is the characteristic of a compression ring having a so-called straight-shaped abutment end parallel to the sliding direction of the piston.

FIG. 8 shows the results of an experiment in which the degree of increase in fuel efficiency was measured in accordance with the blow-by gas blow-through amount. It can be seen that the fuel efficiency of a diesel engine is greatly reduced due to an increase in pressure loss as compared with a gasoline engine. According to the present invention, even when a single compression ring 4 is used, the protruding portion 24 receives the combustion gas pressure during the expansion stroke so that the bottom surface 26a of the ring groove 26 is formed.
To shut off the abutment gap 22 and the lower crankcase side, it is possible to sufficiently reduce the blow-by amount of blow-by gas.

Generally, a gasoline engine runs over 7000 rpm, while a diesel engine runs 5000 rpm
Since the compression ring 4 is operated at a pressure of less than about 1, the compression ring 4 is not lifted by the inertial force during the expansion stroke in which the piston 1 descends, and the sealing performance can be maintained.

(Effects of the Invention) As described above, according to the present invention, in a diesel engine provided with an intake throttle valve in the middle of an intake pipe, blow-by gas can be sufficiently prevented from flowing through, and fuel efficiency can be maintained. The oil consumption can be kept sufficiently low, a single compression ring can be provided, and the friction and weight of the piston can be reduced to improve the performance and contribute to the reduction in size and weight of the diesel engine.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an exhaust gas recirculation device showing an embodiment of the present invention,
FIG. 2 is a cross-sectional view of the engine, FIG. 3 is a perspective view of a main part of the compression ring, and FIGS. 4 (A) and 4 (B) are views of an opening gap portion for explaining the operation during the compression / expansion process. FIGS. 5 (A) and 5 (B) are longitudinal sectional views for explaining the operation during the suction stroke, perspective views of the abutment gap portion, FIG. 6 is a flowchart showing the control contents, Seventh
FIG. 8 and FIG. 8 are diagrams showing the operation. 1 ... piston, 2 ... cylinder, 3 ... oil ring, 4 ... compression ring, 22 ... gap
23 ... recess, 24 ... projection, 26 ... ring groove, 26a ...
Ring groove bottom, 52 …… Intake pipe, 59 …… Intake throttle valve, 68 ……
Electronic control unit, 69 …… Pressure sensor.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F02D 45/00 364 F02D 41/02 360 F02D 9/02 F02F 5/00

Claims (1)

(57) [Claims] In a diesel engine having an intake throttle valve interposed in an intake passage and an exhaust gas recirculation passage communicating the intake passage and the exhaust passage downstream of the intake throttle valve, ring ends opposed to each other with an opening gap interposed therebetween. A single compression ring formed with a notch opening on the lower surface of one of the parts and a projection shaped to supplement the notch at the other end, and an oil ring is provided between the piston and the cylinder. And a negative pressure detecting means is provided in the intake passage,
Pressure control means is provided for controlling the intake throttle valve opening based on the detected negative pressure so that the negative pressure of the intake pipe becomes equal to or less than a predetermined negative pressure value for sufficiently reducing the oil consumption sucked into the combustion chamber. A diesel engine characterized by that: