The present invention relates to a method and apparatus with partial load control of internal combustion engines with internal combustion in several working spaces, in which with a decreasing load, the number of working or power strokes with internal combustion is reduced per time unit.
With a known method of this type (German Offenlegungsschrift No. 18 06 695), certain cylinders, for the purpose of control in the partial load range, are cut off from the fuel supply in a predetermined cycle sequence depending on the magnitude of the desired partial load. As a result thereof, the charge exchange work which is unfavorable from a fuel consumption point of view, can be reduced overall. However, in that case also the cylinders which are not supplied with fuel have to produce charge exchange work. In order to reduce the proportion of the charge exchange work which fall on the latter cylinder, methods are known in the prior art in which the valves of the corresponding cylinders are rendered inoperable, i.e., are halted.
The present invention is concerned with the task to further improve the efficiency with a method of the type described hereinabove.
The underlying problems are solved according to the present invention in that an increasing part of the working spaces are changed-over to an after-expansion operation which includes a number of displacement- and after-expansion cycles divisible by two, whereby the operating gas which is only incompletely expanded in the non-changed-over working spaces in a respective working cycle, is fed to the changed-over working spaces instead of a fresh mixture and is continued to be expanded within the same or in that with a decreasing load all working spaces are changed-over increasingly to a higher number of cycles or strokes, whereby an increasing number of after-fill and after-expansion stroke pairs follows a respective operating cycle containing a power stroke with internal combustion engine.
The method according to the present invention is preferably suitable for internal combustion engines with quantity control.
Accordingly, it is an object of the present invention to provide a method for the partial load control of internal combustion engines which avoids by simple means the aforementioned shortcomings and drawbacks encountered in the prior art.
Another object of the present invention resides in a method for the partial load control of internal combustion engines in which the efficiency is improved.
A further object of the present invention resides in a method for the partial load control of internal combustion engines in which wasted charge-exchange work is minimized.
Still another object of the present invention resides in a method for the partial load control of internal combustion engines which is highly reliable in operation, yet is simple and can be realized by controls known as such in the prior art.
These and other objects, features, and advantages of the present invention will become more apparent from the following description of two preferred methods for the partial load control of internal combustion engines in accordance with the present invention.
The method for the partial load control of internal combustion engines with quantity control and with internal combustion in several working spaces essentially consists in that with a decreasing load the number of working or power strokes with internal combustion is increasingly reduced per time unit in favor of subsequent after-expansion strokes.
In one method of this type according to the present invention, an increasing number of the working spaces is changed-over with a decreasing load to an at least two-cycle after-expansion operation whereby the working gas which is only incompletely expanded in the non-changed-over working spaces is fed to the changed-over working spaces in lieu of a fresh mixture and is continued to be expanded within the same.
Either two or more working spaces thereby operate directly together or an intermediate storage device is used by way of which the working spaces cooperate.
Depending on the construction of the internal combustion engine, the possibility of a single or multiple after-expansion with corresponding higher stroke numbers exists with the present invention.
In a second method of this type according to the present invention, all working spaces are changed-over with a decreasing load to an increasing stroke or cycle number, whereby each working cycle or power stroke is enlarged by a number of refill and after-expansion strokes divisible by two.
Preferably both methods can be carried out by separate valves by means of a separation of the exhaust into high pressure pre-exhaust and low pressure exhaust.
Therebeyond, the exhaust gas emission can be reduced in that during the working strokes with internal combustion engine, a rich mixture is used for the NO.sub.X decrease and additional air is blown in for the after-expansion so that simultaneously an after-oxidation of the uncombusted components takes place which is favorable from an efficiency point of view.
The present invention is also concerned with the internal combustion engine apparatus for carrying out the above-discussed novel methods of engine operation.
These and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein: