The invention relates to a four-stroke internal combustion engine with a crankcase and at least one cylinder arranged in this crankcase and in which a working piston is guided by a crankshaft, with at least one cylinder head that closes the cylinder and whose intake and exhaust ports are managed by at least one intake valve and exhaust valve loaded with a closing spring, wherein these valves can be activated by transmission elements driven by the camshaft, and with a brake control device by which pressure is built up in the exhaust system, in particular, in the exhaust channels, and/or an additional opening of at least one exhaust valve.
Such a class-forming internal combustion engine is generally known. Known are, furthermore, several systems for engine-brake controlling.
One system includes an exhaust-gas choke that is arranged in the exhaust-gas system of the internal combustion engine. Here, the engine must work against the increased pressure in the exhaust-gas system and thus generates braking power.
A different system, disclosed in DE-39 04 497 C1, has a decompression device. In this system, before the end of the compression cycle, the exhaust valve is opened and thus the generated pressure in the combustion chamber is released. Therefore, the energy for the subsequent depressurization cycle is no longer returned to the engine and a braking effect is generated.
It is furthermore known, from EP-0 974 740 A2, to keep open one of the exhaust valves during the braking process, in order to hold it open a small amount, so that continuous decompression with corresponding braking effect is realized.
It has been shown that hydraulic valve clearance compensation elements, also called “HVA” in the present patent application, do not function or do not function satisfactorily in connection with braking devices, because there is the risk, e.g., that the “HVA” makes an undesired adjustment during the braking operation.
Therefore, the object of the invention is to modify a hydraulic valve clearance compensation element so that it is suitable for installation in the valve drive of internal combustion engines with engine brake devices. Here, the “HVA” should be designed so that it does not generate an adjustment also in connection with an engine brake controller. It should be in the position to guarantee a reliably operating function under all conditions.
The objective of the invention is met in that a hydraulic valve clearance compensation element is installed in at least one of the transmission elements between the camshaft and at least one intake and/or exhaust valve that has at least one piston, a cylinder housing part interacting with the piston, a return spring installed in-between, and a check valve, and a locking device that can be activated is provided that limits the movement of the piston relative to the cylinder housing part and/or of the cylinder housing part relative to an outer housing connected to the transmission elements or a transmission element at least in one direction of movement, and the piston is supported on a stop body that is connected to the outer housing or the transmission element. Through this construction it is achieved that during the engine brake operation, the HVA function is maintained, but the HVA cannot be adjusted past the movement limit. Therefore, the pumping of the HVA is prevented, although the exhaust valve or valves are partially opened in the engine brake operation and the transmission elements are at least partially depressurized. During the locking limit, the HVA can fade under loading and during depressurization can be adjusted within the limited region, wherein when leaving the braking operation, the HVA again compensates the maximum possible fading path.
In another construction of the invention it is provided that the locking device that can be activated has a clamping sleeve that is arranged between the cylinder housing part and the outer housing or the transmission element, and the clamping sleeve forms a stop with the outer housing or the transmission element, and the clamping sleeve can be fixed relative to the cylinder housing part.
According to an alternative construction of the invention it is provided that the locking device that can be activated has a clamping sleeve that is arranged between the stop body and the outer housing or the transmission element, the clamping sleeve forms a stop with the cylinder housing, and the clamping sleeve can be fixed relative to the stop body.
In this way it is achieved that the cylinder housing part does not continue to pump for an open exhaust valve, that is, for an at least partial depressurization of the transmission elements. In this way, because the locking device can be locked at an arbitrary point, the position of the stop is variable and adapts to the working position of the HVA. Therefore, in the position in which it is located at the beginning of the engine brake control, a stop is allocated to the HVA and thus limits the movement in one direction.
Advantageously, the stop can have a spring ring that is arranged in a recess of the clamping sleeve or in a recess of the cylinder housing part and is in active connection with a support surface on the outer housing or on the transmission element or with a support surface on the clamping sleeve. In these features, both constructions are integrated and comprise both the version in which the clamping sleeve is arranged around the cylinder housing part and also the version in which the clamping sleeve is arranged essentially around the stop body and the stop is arranged between the clamping sleeve and the cylinder housing part.
In the construction in which the clamping sleeve is arranged around the cylinder housing part, a clamping sleeve spring is installed that is constructed as a compression spring and that is supported on one side on the clamping sleeve and on the other side on the stop body that is formed in this case as a stop plate.
In the construction in which the clamping sleeve is arranged around the stop body, the clamping sleeve spring is arranged so that it is supported on one side on the clamping sleeve and on the other side on the outer housing or on the transmission element.
The locking device contains at least one clamping body that is supported so that it can move in the cylinder housing part or in the alternative construction in the stop body, wherein the clamping body is loaded on one side by a spring and can be loaded on the other side by a pressurized fluid and wherein the clamping sleeve can be fixed by the clamping body relative to the stop body or the cylinder housing part. In this way it is achieved that at the beginning of the engine brake control the at least one clamping body is pressed by a spring or pressurized fluid against the clamping sleeve and thus the clamping sleeve is fixed accordingly.
Advantageously, teeth, grooves, or the like or other types of roughened sections adapted to each other are provided to the clamping body on its surface facing the clamping sleeve and to the clamping sleeve on its surface facing the clamping body, so that the clamping sleeve can be clearly fixed. Obviously, the teeth, grooves, or the like on the clamping sleeve have a longer extent in the adjustment direction of the HVA, so that the clamping sleeve can be fixed in all of the possible operating positions at the beginning of the engine brake control.
In connection with the construction in which the clamping sleeve is arranged around the cylinder housing part, it is provided that at least two clamping bodies are provided that are supported against each other by a clamping body spring and that the clamping sleeve has, in its wall, in the region of the clamping body, openings that can be connected controllably to a pressurized fluid source. In this construction, in normal operation of the HVA, pressurized fluid is provided by the openings and the clamping body is compressed against the force of the clamping body spring, so that the HVA can work without limitation. At the beginning of the braking operation, when the pumping of the HVA is to be limited, the connection of the openings to the pressurized fluid source is interrupted and the openings are depressurized, so that the clamping body spring presses the clamping body in the direction of the clamping sleeve and the teeth engage in each other, so that the stop is active.
So that the openings of the clamping bodies are adapted, the clamping sleeve is locked in rotation relative to the cylinder housing part. The rotational locking can be realized by an alignment pin that is arranged in the clamping body and that is in active connection with a longitudinal groove in the cylinder housing part.
Furthermore, it is provided that the facing surfaces of the clamping body are in active connection with an adjustment pin that is arranged in the cylinder housing part. The adjustment pin is advantageously formed similarly as a fitted key, so that it simultaneously causes a ventilation of the inner space between the clamping bodies in which is arranged advantageously the clamping body spring.
According to the alternative construction in which the clamping sleeve is arranged around the stop body, it is provided that there are at least two clamping bodies that are loaded against each other by a tension spring and that, in the region of the facing surfaces of the clamping bodies, a borehole is provided in the stop body, wherein this borehole can be connected controllably to a pressurized fluid source. In this construction, the clamping bodies are held together by the tension spring and brought with the clamping sleeve out from the active connection, so that the HVA can operate in the normal state. At the beginning of the brake control, when the HVA is to be limited, pressurized fluid is fed via the borehole between the clamping bodies, so that these engage with their teeth in the teeth of the clamping sleeve and the stop becomes active.
Advantageously, the tension spring is formed as a tubular spring that is arranged in grooves in the surfaces of the clamping body facing the clamping sleeve. Advantageously the stop body then also obtains grooves, so that the tubular spring can be placed like a ring around the stop body and the clamping body. Between the facing surfaces of the clamping bodies, a spring ring is inserted in the stop body, wherein this spring ring is arranged in an extension of the borehole, so that, on one hand, pressurized fluid can always reach between the clamping bodies and, on the other hand, these can have an inner stop.
For further explanation of the invention, refer to the drawings in which embodiments of the invention are shown simplified. Shown are:
In
In the embodiment according to
In the cylinder housing part 2, two clamping bodies 11 are installed underneath the piston 3 and guided so that they can move in the radial direction. Between the clamping bodies 11, a clamping body spring designated with 12 is installed that is constructed as a compression spring and loads the clamping bodies outward in the radial direction. The clamping bodies 11 have teeth on their surfaces facing the clamping sleeve 6, wherein these teeth are complementary to corresponding teeth on the inner surface of the clamping sleeve. The teeth region on the inner surface of the clamping sleeve is extended in the longitudinal direction of the HVA across the clamping bodies, so that the teeth engagement between the clamping bodies and clamping sleeve can be realized at arbitrary positions of the HVA. In the region of the clamping body end faces, openings 13 are machined into the clamping sleeve 6, wherein these openings are in active connection with an annular recess in the outer housing 1 and wherein a not-shown pressurized oil source is connected to the annular recess.
As shown in the embodiment according to
In the embodiment according to
In the embodiment according to
Grooves 20 are machined into the surfaces of the clamping bodies 11 facing the clamping sleeve 6, wherein, not shown, a tubular spring formed as a tension spring is inserted into these grooves. This tubular spring presses the clamping bodies 11 together, so that these are not in active connection with the teeth of the clamping sleeve 6, as shown in
Number | Date | Country | Kind |
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10 2007 051 302 | Oct 2007 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2008/063031 | 9/29/2008 | WO | 00 | 4/26/2010 |
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WO2009/053223 | 4/30/2009 | WO | A |
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