HK1060611B - Four-cycle internal combustion engine - Google Patents

Description

Four-stroke internal combustion engine

Technical Field

The invention relates to a four-stroke internal combustion engine with at least one cylinder; and a crankcase, which forms a crankshaft pump and which is connected, respectively, by means of valves, on the one hand to an air manifold for fresh air and, on the other hand, to an intake manifold that connects together the crankcase and the intake ports of the cylinders; with a tank for storing lubricating oil arranged on the conveying device for lubricating oil; and with an oil circuit comprising a crankcase and an oil separator arranged in the intake manifold; with means for injecting fuel into the intake manifold or combustion chamber of the cylinder.

Background

In order to pressurize the air drawn into a four-stroke internal combustion engine by means of a crankcase pump, it is known (EP O631040) to provide the crankcase with a fuel-air mixture that is rich in lubricating oil, which is supplied to the combustion chambers of the cylinders after it has been pressurized by the crankcase pump. However, these known four-stroke internal combustion engines suffer from the following disadvantages: the lubricating oil delivered to the combustion chamber of the cylinder together with the fuel-gas mixture is combusted, resulting in a higher pollutant load in the exhaust gases. Furthermore, as fuel enters the crankcase, the lubrication effect in the crankcase is reduced compared to pure oil lubrication. In other known constructions (US 5,785,610a), these disadvantages are avoided, in that only fresh air is drawn into the crankcase and fuel injection takes place only in the region of the cylinder intake port connected to the crankcase via the intake manifold. Since the oil separator is arranged in the intake manifold between the crankcase and the intake end in the direction in which the pressurized combustion air flows before fuel injection, and since the lubricating oil from the crankcase entrained by the combustion air is separated from the combustion air flow via the oil separator and returned to the crankcase via the intake manifold, it can be assumed that a fuel-air mixture without lubricating oil is supplied from the crankcase to the combustion chamber. Conventional oil lubricated arrangements require a sufficient amount of oil in the crankcase. This therefore imposes an unfavorable constructional precondition on the crankcase pump, in the case that the ratio between the volume of the crankcase and the displacement of the piston should be as small as possible.

In order to improve the conventional conditions of crankcase pumps, a recent known technique (DE 3731250C 1) separates the crankcase from an oil sump receiving lubricating oil which is pumped from the oil sump to the individual bearing points in the form of conventional forced oil lubrication. The pressurized combustion gases with lubricating oil from the crankcase are sent to the oil sump through a one-way valve where oil separation occurs due to air deflection around the baffle. The remaining oil is separated from the combustion air in an oil separator inserted in the intake manifold between the oil pan and the intake ports of the cylinders. As a result of the forced oil lubrication, a relatively large amount of oil is added to the combustion air flow, which increases the burden imposed on the required oil separation. Consequently, a consequent pressure loss in the event of impairment of the combustion air charging. Additional factors are: by adding an oil sump to the supply of combustion air, the total volume for pressurizing the combustion gas is increased, as a result of which the acceleration behavior of the internal combustion engine is adversely affected. Since the lubricating oil should be removed from the crankcase as quickly as possible for the subsequent oil separation in order to avoid swirling of the lubricating oil and thereby to avoid that the removed combustion gases carry lubricating oil, it is necessary to ensure a relatively large oil circulation speed in the oil circuit.

Disclosure of Invention

The invention is therefore based on the object of providing a four-stroke internal combustion engine of the type mentioned above in such a way that, in addition to favorable constructional preconditions for the crankcase pump, favorable oil lubrication can be ensured in the crankcase with a relatively small amount of oil without fear of any adverse effect on the acceleration behavior of the internal combustion engine.

The invention achieves the purpose by the following modes: that is, there is provided a four-stroke internal combustion engine having: at least one cylinder; a crankcase forming a crankshaft pump and connected, respectively, by means of valves, on the one hand to an air manifold for fresh air and, on the other hand, to an intake manifold connecting the crankcase and the intake ports of the cylinders together; and having a tank of lubricating oil arranged on a conveying device for lubricating oil; an oil circulation circuit including a crankcase and an oil separator disposed in the intake manifold; and means for injecting fuel into the intake manifold or combustion chamber of the cylinder, wherein the transfer means connected to the oil tank comprises a conduit for injecting lubricating oil into the crankcase, and the intake manifold leads to the oil separator by surrounding the oil tank.

Since the lubricating oil will be injected into the crankcase, being able to provide sufficient lubricating oil to the moving parts will be ensured without the need for oil passages or any forced oil lubrication. This means that a smaller amount of oil is needed, which is distributed in the crankcase by means of fresh air sucked into the crankcase. Due to the swirling of the lubricating oil required for lubrication at the lubrication points in the crankcase area, the lubricating oil can stay in the crankcase for a longer time, which again reduces the required oil flow through. Due to the lower oil quantity, favorable separation conditions are still obtained, so that only one oil separator can be arranged in the air manifold between the crankcase and the cylinder air inlet. The simple guidance of the intake manifold from the crankcase via the oil separator to the intake port of the cylinder avoids high pressure losses by surrounding the oil tank which stores the lubricating oil, and also ensures favorable acceleration characteristics of the internal combustion engine due to the limited total volume of pressurized combustion air.

The lubricating oil from the oil separating chamber of the oil separator can be recirculated via a recirculation line to a tank for lubricating oil, whereby the oil circulation is closed off via said tank. Another possibility is to connect the oil separator to the crankcase itself via a recirculation line starting from the oil separation chamber, leading to an oil circulation line comprising only the crankcase and the oil separator. The transfer device, which is connected to the oil tank and comprises a conduit for injecting lubricating oil into the crankcase, serves in this case only to compensate for the loss of lubricating oil. Since it must be desirable to have the lubricating oil slightly carry the fuel from the cylinder to the crankcase via the piston rings (piston gaskets) in the crankcase, such oil circulation offers the advantage that the lubricating oil is continuously supplied with fresh, non-entrained oil in the oil circulation carried by the fuel, whereas in the oil circulation via the fuel tank it is desirable to have the lubricating oil carry the fuel in the fuel tank.

The relevant aspects for making the consumption of lubricating oil low are: the lubricating oil is advantageously separated from the flow of pressurised combustion air. When the oil separator consists of a cyclone separator, the required high separation rate can advantageously be ensured.

Although the lubricating oil can be injected into the crankcase at different places in order to supply components with a high lubricating demand in a preferred manner, advantageous injection conditions are obtained, in particular when the conduit for lubricating oil is connected at least to a nozzle arranged in the region of the opening of the supply manifold for fresh air. For lubricating oil, an additional distribution effect of the lubricating oil can be achieved by fresh air flowing into the crankcase.

Drawings

The invention is described in detail with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic cross-sectional view of a four-stroke internal combustion engine according to the present invention; and

fig. 2 shows an embodiment of a four-stroke internal combustion engine corresponding to that of fig. 1.

Detailed Description

In the shown embodiment of the four-stroke internal combustion engine according to the invention, the cylinder assembly 1 forms one part 2 of a crankcase 3, the other part of which is arranged as a cylinder head 4. The connecting rod 7 of the piston 8 of at least one cylinder 9 is fixed to the crankpin 5 of a crankshaft 6 fixed in the crankcase 3, the head 10 of the cylinder 9 comprising at least one inlet 11 with an inlet valve 12 and an outlet 13 with an outlet valve 14.

The crankcase 3 in combination with the piston 8 forms a crankshaft pump, through which fresh air is sucked in and compressed. For this purpose, the crankcase 3 is connected via a non-return valve 15 to an air manifold 16 for fresh air. On the opposite peripheral side to the air manifold 16, connected to the crankcase 3 via a one-way valve 18, is an intake manifold 17 for combustion air pressurized in the crankcase 3. An oil separator 19 is inserted into the intake manifold 17 connected to the intake 11, which is arranged as a cyclone separator with a separation chamber 20 into which a branch 21 of the intake manifold 17 opens tangentially, which branch 21 leads out from the crankcase 3, while a connecting branch 22 to the intake 11 ensures that the air in the middle is discharged from the oil separation chamber 20. In the region of the junction of the connecting branch 22 of the intake manifold 17 leading to the intake port 11, an injection device 23 for fuel is provided, so that a pressurized fuel-air mixture is drawn in through the intake port 11.

According to the embodiment shown in fig. 1, a recirculation line 24 leads from the oil separation chamber 20 to an oil tank 25 for lubricating oil which circulates in an oil circulation circuit comprising a line 27, which line 27 is fed by a conveyor 26 and supplies a nozzle 28 which projects into the crankcase 3 in the region of the orifice of the supply line 16 with lubricating oil. The lubricating oil which is injected into the crankcase via several nozzles and whose distribution in the crankcase 3 is dominated by the fresh air which is sucked in ensures that there is sufficient oil lubrication in the crankcase 3. Since a portion of the lubricating oil injected via the nozzle 28 is removed from the crankcase via the branch 21 of the air manifold together with the pressurized combustion air and separated in the oil separator 19, oil lubrication in the crankcase is ensured, which ensures favorable oil lubrication in the crankcase 3 in addition to the tight-packed condition favorable for the pump pressure conditions.

In contrast to the embodiment according to fig. 1, the recirculation line 24 according to the embodiment of fig. 2 does not open into the oil tank 25, but into the crankcase 3 itself, whereby the oil circulation is closed off via the crankcase 3 by surrounding the oil tank 25 via the oil separator 19, with the advantage that the lubricating oil sprayed from the oil tank 25 into the crankcase 3 is free of fuel that reaches the crankcase from the cylinder 9.

It should be understood that the invention is not limited to the illustrated embodiments. Therefore, the fuel injection may not be provided in the region of the intake manifold 17, but may be provided directly in the combustion chamber 29. Furthermore, it is not mandatory to inject the lubricating oil in the orifice region of the air manifold 16 for fresh air. The oil tank 25 for lubricating oil may be part of a further oil circulation circuit of the combustion engine. The delivery device 26 for lubricating oil may also be formed without using an oil pump. In this case, the delivery of oil can be ensured by the pressure pulsation.

Claims (6)

1. A four-stroke internal combustion engine having: at least one cylinder (9); a crankcase (3) forming a crankshaft pump and connected, respectively, by means of valves (15, 18) to an air manifold (16) for fresh air on the one hand and to an intake manifold (17) connecting together the crankcase (3) and the intake ports (11) of the cylinders (9); and having a tank (25) of lubricating oil arranged on a conveying device (26) for lubricating oil; an oil circulation circuit having an oil separator (19) provided in an intake manifold (17) and including a crankcase (3); and means (23) for injecting fuel into the intake manifold (17) or combustion chamber (29) of the cylinder (9),

characterized in that the transfer device (26) connected to the oil tank (25) comprises a conduit (27) for injecting lubricating oil into the crankcase (3), and in that the inlet manifold leads to the oil separator (19) by surrounding the oil tank (25).

2. A four-stroke internal combustion engine as claimed in claim 1, wherein the oil separator (19) is connected to the oil tank (25) via a recirculation line (24) from the oil separation chamber (20).

3. A four-stroke internal combustion engine as claimed in claim 1, wherein the oil separator (19) is connected to the crankcase (3) via a recirculation line (24) from the oil separation chamber (20).

4. A four-stroke internal combustion engine as claimed in any one of claims 1 to 3, wherein the oil separator (19) consists of a cyclonic separator.

5. A four-stroke internal combustion engine as claimed in any one of claims 1 to 3, wherein the conduit (27) for lubricating oil is connected to at least one nozzle (28) arranged in the orifice area of the air manifold (16) for fresh air.

6. A four-stroke internal combustion engine as claimed in claim 4, wherein the conduit (27) for lubricating oil is connected to at least one nozzle (28) arranged in the orifice area of the air manifold (16) for fresh air.