This application is the U.S. national stage of International Application No. PCT/EP2011/000251 filed on Jan. 21, 2011, which claims priority to German patent application no. 10 2010 007 235.4 filed on Feb. 9, 2010.
The invention relates to a method for varying the duration of a supply stroke of a pump element, the supply stroke of which is actuated by a rotatably-driven pump shaft over a predetermined rotational position range of the pump shaft. The invention further relates to a pump device for performing the method.
Distributor injection pumps, in particular distributor injection pumps for diesel engines with direct injection, are known. In such distributor injection pumps, in general a pump shaft is driven by the crankshaft of an internal combustion engine, which pump shaft drives a pre-supply pump contained in a housing and a high-pressure pump connected downstream of the supply pump. The high-pressure pump contains a single pump element, which is formed as a distributor piston, which carries out a rotational motion as well as a stroke motion and in the sequence of its rotation is sequentially connected with outlets leading to individual cylinders of the internal combustion engine via a distributor.
A peculiarity of the distributor injection pumps is that the injection pressure depends on the rotational speed of the pump shaft and for example increases linearly or even exponentially with the rotational speed. This means a low injection pressure at low engine rotational speeds and a high injection pressure at high engine rotational speeds. The injection pressure, which is available at the injection valves that in general open against a spring force, is an important operating parameter having a strong influence on emissions and torque.
It is an object of the present teachings to disclose an injection pump, whose supply speed and/or supply injection pressure can be held at an at least substantially constant value and, if necessary, at a relatively high value, independent of the rotational speed of a drive shaft of the injection pump.
In one aspect of the present teachings, a kinematic transmission is preferably disposed between the pump shaft, whose angular speed and/or rotational speed determines the supply speed and/or the duration of the stroke of one or more pump elements, and a drive shaft, with which the pump shaft is driven, which kinematic transmission makes it possible to increase or decrease the angular speed of the pump shaft, as required, for a drive shaft that rotates at a constant rotational speed or angular speed within the rotational position ranges of the pump shaft; a supply stroke or a fluid supply cycle, for example liquid fuel, takes place within the rotational position ranges.
The invention is suitable for substantially all types of pumps or pump devices, in which a predetermined volume of fluid is supplied to an outlet conduit over a rotational position range of a rotatably-driven pump shaft of a pump element, which is moved by the pump shaft.
With the assistance of schematic drawings, the invention will be explained below in an exemplary manner and with further details.
According to
Overall, as the pump shaft P rotates, the individual outlets 20 are sequentially loaded with fuel supplied by the pump element or the pump elements during predetermined rotational position intervals of the pump shaft P, wherein without taking additional measures, the amount of fuel supplied in accordance with the rotation of the pump shaft is independent of the rotational speed of the pump shaft; however, with increasing rotational speed of the pump shaft, the supply duration, i.e. the period of time within which a predetermined amount of fuel is supplied, becomes shorter, and the supply speed, i.e. the speed of the pump element when executing a supply stroke, increases. In this way, a pressure resulting at a throttle point or an inlet of an injector valve generally increases with increasing rotational speed of the pump shaft P.
In the embodiment according to
It is assumed that a direct-injection diesel engine has an operating range between 1,000 and 4,000 revolutions per minute of the crankshaft. The drive from the crankshaft to the pump shaft is then such that the pump shaft—for an embodiment of the internal combustion engine as a four-stroke engine—rotates at one-half the rotational speed of the crankshaft, i.e. at a rotational speed between 500 and 2,000 min.−1. With a conventional drive of the pump shaft P at one-half the rotational speed of the crankshaft, the pressure acting at the outlets changes in accordance with the rotational speed of the pump shaft between a minimal value of 500 min.−1 and a maximal value of 2,000 min.−1. This pressure fluctuation makes an optimal layout of the entire injection system more difficult and leads to difficulties with the simultaneous fulfillment of emission regulations and sufficient torque at low rotational speeds.
According to the invention the kinematic transmission 16 is connected upstream of the drive of the pump shaft P, which makes it possible that, at a constant rotational speed of the drive shaft A and/or of an input link of the kinematic transmission 16, the angular speed of the pump shaft P increases and decreases during one rotation of the pump shaft P as often as the outlets 20 associated with the individual cylinders are loaded with supplied fuel or pressure at equal angular intervals of the pump shaft.
The function of the kinematic transmission 16 will be explained with the assistance of
In the following, the rotational speed of the drive shaft and/or of the input shaft is designated as the rotational speed, because the angular speed of the drive shaft during one rotation—except for rotational oscillations of the crankshaft—is constant when the crankshaft rotates at a constant rotational speed. The rotational speed of the pump shaft, which changes during one revolution as often as the number of outlets of the pump, is designated as the angular speed.
It is assumed, for example, that the rotational speed of the drive shaft and/or of the input element of the kinematic transmission is one-half of the crankshaft speed of the internal combustion engine (for four-stroke engines). If the minimum operating rotational speed of the internal combustion engine is 1,000 min.−1, in the embodiments according to
The disk 14 rotatably driven by the endless belt/chain means 12 is rigidly connected with a support rod 22, which is borne on an axle 24 concentric to the rotational axis of the disk 14. A planetary gear 26 is rotatably borne on the support rod 22; the external teeth of the planetary gear 26 mesh with external teeth of a large gear 28, which is disposed concentric to the axle 24 and is rigidly connected with an adjusting arm 29, which is part of an adjusting device 30. The rotational position of the large gear 28 can be adjusted using the adjusting device 30.
Eccentric to the bearing of the planetary gear 26 on the support rod 22, a push rod 32 is borne on the planetary gear 26; the push rod 32 is rotatably borne on an extension 34 at the end of the push rod 32 that faces away from the rotatable bearing at the planetary gear 26; the extension 34 is rigidly connected with an annular part 36, which is rotatable coaxially relative to axle 24 and is connected with the pump shaft P so as to rotate therewith (
If the diameter of the planetary gear 26 for example is one-fourth of the diameter of the large gear 28, the planetary gear 26 rotates about the large gear 28 four times during one full rotation about its axis for its revolution accompanying the rotation of the disk 14, so that the extension 34 advances or retards the support rod 22 four times during one rotation. In this way, during one revolution, four times the annular part 36 or the pump shaft P has a larger angular speed and four times it has a smaller angular speed than the disk 14 and/or the drive shaft A. The amplitude of the increase of the angular speed and the decrease of the angular speed of the pump shaft P relative to that of the disk 14 can be adjusted by changing the length of the push rod 32, by changing the distance of the rotatable support of the push rod 32 to the extension 34 from the rotational axis of the annular part 36 and by changing the distance of the rotatable of the push rod 32 to the planetary gear 26 from its rotational axis. The amplitude of these angular speed changes can be adjusted for example by varying of the last-mentioned distance using a cam. The phase position of the angular speed change of the annular part 36 (of the pump shaft P) relative to the disk 14 (of the crankshaft KW) can be changed by changing the rotational position of the stationary large gear 28 using the adjusting device 30.
Referring to
Another advantageous possibility, which is made possible with the described kinematic transmission, is as follows: As can be seen from
In the embodiment according to
It is understood that other forms of a symmetric arrangement of the transmission with more than two (e.g. three or four transmissions according to
In the embodiment according to
The further planetary gear 40 does not mesh with the external teeth of the gear 28, but rather with internal teeth of a further gear 46, whose teeth are concentric to the teeth of the gear 28. The diameter of the further planetary gear 40 is larger than that of the first planetary gear 26, so that the rotational speed of both planetary gears is the same. The endless belt/chain means 12 drives a hub of the support rod 22. The support rod 22 is not connected with the further gear 46. The further gear 46 is held rotationally fixed, wherein its rotational position is adjustable using a further adjusting device 48. The function of the kinematic drive according to
In
The figure part b) indicates the ratio of the angular speed ω2 of the extension 34 to the angular speed ω1 of the guide rod 42 in dependence on the rotational position Φ1 of the guide rod 42, which ratio is given by the eccentric bearing of the push rod 44 on the second planetary gear 40.
The figure part c) indicates the ratio between the angular speed ω2 of the extension 34 and the angular speed ω0 of the support rod 22 for the case that the two angular speed changes related to the planetary gears 26 and 40 are substantially in phase and lead to maximum changes of the angular speed of the extension 34 (pump shaft) relative to the angular speed of the support rod 22 (drive shaft or crankshaft). An adjustment of the adjusting device 30 does not lead to a change of the relative positions of the two planetary gears 26 to one another, but rather only to a parallel shift of the curve according to
c) indicates the change resulting from the superposition of the two angular speed changes of the angular speed ω2 of the extension 34 relative to the angular speed ω0 of the support rod 22 over the rotational position Φ0 of the support rod 22 for the case that the eccentric bearings of the push rod 44 on the planetary gear 40 and the push rod 32 on the planetary gear 26 act in opposite directions.
Through a suitable choice of the values that mediate the angular speed changes, such as the eccentricities of the bearings of the push rods 44 and 32, the radial location of the linkage of the push rod 44 to the extension 34 and the relative rotational positions of the two planetary gears 26 and 40, the amplitude of the angular speed change can be reduced to a very small amount, in the ideal case so far that the angular speed of the extension 34 is constantly substantially the same amount as the angular speed of the support rod 22. The function of the adjusting device 30 of
The curves indicated in
The Figures explain only a few examples for kinematic transmissions, which can be modified in various ways. For example in
For the lubrication of the transmission, either an immersion oil lubrication with one-time filling and corresponding change intervals, or a spray oil supply with corresponding oil drain can be provided. For the spray oil supply, the existing engine oil circulation system of the internal combustion engine can be used.
The invention can in general be used for pumps or pump devices wherein, in dependence on the rotational position of a pump shaft, at least one outlet is loaded with supply pressure that depends on the angular speed of the pump shaft. Examples for such pumps are distributor injection pumps, in-line injection pumps as well as insertion pumps having separate camshafts for pump-line-nozzle systems.
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10 2010 007 235 | Feb 2010 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2011/000251 | 1/21/2011 | WO | 00 | 8/8/2012 |
Publishing Document | Publishing Date | Country | Kind |
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WO2011/098208 | 8/18/2011 | WO | A |
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Number | Date | Country | |
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20120301327 A1 | Nov 2012 | US |