The invention relates to a camshaft adjusting system according to the preamble of the independent claim.
Camshaft adjusting systems consist of a number of different components. The number of the components may vary, although a common feature of many camshaft adjusting systems lies in the presence of a camshaft adjusting device and a control valve or a control valve group. There are different types of camshaft adjusting devices, all of which can rotate the relative position of a camshaft with respect to a further shaft, such as the crankshaft, of an internal combustion engine. One type of camshaft adjusting device which is frequently used is the oscillating motor camshaft adjusting device. An oscillating motor camshaft adjusting device is a rotatory vane-type motor which converts the hydraulic pressurization of one chamber with respect to another chamber into rotatory movement. The two chambers, which act in opposition, are separated by a mobile vane which changes the position according to pressure ratios. The camshaft, which is connected to the camshaft adjusting device, is in turn entrained and rotated in its position as a result of the change in position. The number of chambers of one direction of action, the number of vanes and the number of chambers of the opposite direction of action frequently correspond. Chambers of the same type are hydraulically interconnected. The chambers lead to a control valve group or a control valve. The functionality of a large-scale integrated control valve can be imitated through a skillful connection of a plurality of control valves. Considered in hydraulic terms, control valve groups consisting of a plurality of valves are consequently similar to control valves which consist of a single control valve provided with a plurality of connections. It is therefore to be assumed that the chambers of the first direction of action are all directly or indirectly interconnected and the chambers of the second direction of action lead to a further connection of the control valve group. The connections A and B are referred to in simplified terms.
It is desirable to know the relative position of the camshaft with respect to its reference shaft, in particular in the case of extraordinary operating states of the internal combustion engine. The patent literature discloses numerous proposals in which a defined position can be deduced by using special locking mechanisms. An example can be found in the German patent application DE 102004012460 A (HYDRAULIK-RING GMBH). - - - ., in which locking positions can be selected and planned through a skillful combination of a camshaft adjusting device with a spring.
Other areas of hydraulic motor vehicle technology disclose particular valves which, through their configuration, produce delays of a switching response in selected operating states.
DE 19816069 A (HYDRAULIK-RING GMBH). - - - . describes a valve which can preferably be used for automated manually shifted transmissions. A piston, which can be pressurized on both sides and which separates two pressure spaces from one another, is controlled via a valve with a safety function. In the zero switched position, the safety position, the three-way proportional valve does not have to close the coupling suddenly in the case of a disturbance.
Other valves which can be used with camshaft adjusting devices can be found in CN 2592932 Y (ZHONG WEISHING).Dec. 5, 2002. and in EP 1316733 A (SIMEONI S.R.L.).Sep. 23, 2002.
The inventors of the present invention were searching for a possibility, as simple and reliable as possible, of producing a defined state in a camshaft adjusting system. For this purpose they considered both changing the camshaft adjusting device in terms of components and taking action in the camshaft adjusting system at other locations, such as at the control, for example.
DE 10344816 A (AISIN SEIKI). - - - . presents a 7/6-way valve which, when the internal combustion engine is switched off, this being called the engine stop signal in the publication, moves a camshaft adjusting system into a particular state by supplying a sufficient quantity of electricity from an ECU in order to initiate a fluid drain function through setting a first regulating mechanism, the response of a blocking mechanism and setting a second regulating mechanism. Not only is it undesirable to integrate 7/6-way valves of a long construction into a cylinder head, but the camshaft adjusting system also requires turn-off run-down times instead of using the start delays for timing adjustment processes. Furthermore, a distinction is made in the method disclosed here between many different states when switching off in the camshaft adjusting system and when draining oil. The approach which is disclosed here appears to lie in constructing a highly complicated system having disadvantages due to its components.
The object according to the invention is achieved by a camshaft adjusting system according to the characterizing part of the independent claim. Advantageous developments can be found in the dependent claims. A suitable engine is disclosed in the second independent claim. A method according to the invention for operating a camshaft adjusting system according to the invention is disclosed in the third independent claim.
As already indicated, camshaft adjusting systems differ considerably, according to the system. However no camshaft adjusting system is effective without a camshaft adjusting device and a control valve or a control valve group. If the camshaft adjusting device works according to the principle of an oscillating motor camshaft adjusting device or a vane-type camshaft adjusting device, it has at least two opposed hydraulic chambers. When one hydraulic chamber becomes larger, the corresponding opposite hydraulic chamber becomes smaller. There are also oscillating motor camshaft adjusting devices with a high number of hydraulic chambers of the same type which act in the same direction.
The overall behavior is decisive for the control valve group. Irrespective of how the control valve group is constructed, it must as a whole behave like a 4/4-way valve towards the outside, in relation to its interfaces. A 4/4-way valve is a valve which has four defined operating states and interconnects four connections. The connections of the valve according to the invention comprise a connection for the first group of hydraulic chambers of the camshaft adjusting device, a connection for the second group of hydraulic chambers of the camshaft adjusting device, a tank connection and a connection which is supplied with pressurized hydraulic medium, the so-called connection for pressurization.
The control valve group, or the 4/4-way valve, switches the camshaft adjusting system into a first state. The first state is distinguished by the fact that both connections of the valve, which are to lead to the first and second hydraulic chamber groups, are hydraulically short-circuited with respect to the tank connection. There is a hydraulic connection between the tank connection and the connections for the camshaft adjusting device. The hydraulic medium thus flows out of both chambers of the camshaft adjusting device at the same time into a tank container or a tank region, preferably on account of the force of gravity or because of an underpressure. The camshaft adjusting device, previously still pressurized, is as a result switched directly pressureless, without further intermediate steps. It is pressure-relieved with respect to the tank connection. The term “pressureless” is to be understood as meaning that no appreciable pressure remains in relation to the maximum overall pressure in the camshaft adjusting device. The threshold for the insignificant pressure may lie, for example, at 10 percent of the operating pressure. However the term “pressureless” also denotes the state in which virtually all the hydraulic medium has left the camshaft adjusting device through the valve position. Hydraulic oil may still remain in several chambers, depending on the arrangement in the camshaft adjusting device. For example, in a camshaft adjusting device of the central feed duct type, in which a feed duct is brought partly via the camshaft in the centre of the camshaft adjusting device up to the individual advanced chambers, oil remains in the chamber parts which lie gravitationally below the central feed duct. The state is also called pressureless. It is therefore of interest, according to one aspect, that a minimum adjustment can still take place in the pressureless state.
Because the hydraulic oil may be heated, in particular during operation and when switching off the engine, and, according to current exhaust gas standards, the pollutant emission of the internal combustion engine is to be measured at the beginning of an operating cycle, according to one aspect of the invention, the pressureless state, the state I, can ideally be set upon starting the internal combustion engine, preferably passively through biasing forces of a valve spring, for example. Following this setting, the oil can for the most part be drained out of the camshaft adjusting device during the first operating seconds.
According to another aspect of the invention, the camshaft adjusting system may be provided with a check valve which is active for the normal operating phases in the pressurized feed line, while the return to the tank takes place without a check valve in the starting phase.
The described first state of the 4/4-way valve may be called operating end or operating start time state of the camshaft adjusting device. It is an operating end time state because the state is started when the camshaft adjusting system is to be turned off. It is called operating start time state when the adjusting device is put into operation while starting the internal combustion engine into which the camshaft adjusting system is integrated. The camshaft adjusting system is as a rule to be turned off when the internal combustion engine is to be either started, without a load or turned off. It is also possible to speak of an operating end time state when there is an electrical fault which turns off the camshaft adjusting system while the internal combustion engine continues to be operated. The internal combustion engine must be in a controllable and defined state in the phases of the operating end time state. The state is controllable when the relative position of the rotatable camshaft with respect to the reference shaft is known. It is desirable for the state to be taken up in particular when starting the internal combustion engine. In order to avoid complicating the starting of the internal combustion engine unnecessarily, it should be possible to use the initial period of starting the engine to hold the camshaft adjusting device pressureless, even if there were still to be residual oil pressures in the camshaft adjusting system. In conjunction with a suitable central locking system according to, for example, DE 102 53 883 A1, with all embodiments being part of the protective scope of this application for protection, the relative position rotation, once pressureless, is inhibited upon starting the internal combustion engine.
It is as a result of secondary importance for the invention whether the invention has been put into effect by means of a 4/4-way valve or whether an entire control valve group is interconnected such that it exhibits the behavior according to the invention.
There are three further states in addition to the first state. The states may be interchanged. They depend on the actual configuration of the camshaft adjusting system. One state is designed for the retarded adjustment of the camshaft adjusting device. In this state the hydraulic chamber for the retarded adjustment of the camshaft adjusting device is started with pressurized hydraulic medium. One state is intended for the holding position of the camshaft adjusting device. One state is selected when the camshaft adjusting device is to be brought to advance adjustment.
In an advantageously configured system the valve follows a certain state sequence. If the valve is in one state, it can only be moved into an adjacent state. If, therefore, the sequence of a valve according to the invention appears such that, after the operating end time state, the retarded adjustment and subsequently the holding position and, as the fourth, the advance adjustment follow, the valve can only trigger the holding position from the advance adjustment. The valve can be moved both into the operating end time state and into the holding position from the retarded adjustment.
Other sequences are just as conceivable. For example, it is conceivable for the valve to follow the sequences operating end time state, advance adjustment, holding position and retarded adjustment.
An important factor in the case of many valves is for the operating end time state to be the rest position of the valve without adjustment of the piston or of the tappet. A valve of this kind can be put into effect through a cartridge valve which is spring-biased on one side. The spring pushes the piston and the tappet into the rest position, from which the valve only changes over to another state by being energized. A further advantage of the cartridge valve lies in the fact that it can be mounted in an engine block instead of a valve previously used. The manufacturer or operator of an internal combustion engine can therefore improve an existing system by exchanging the valves. The cartridge valve is screwed in as a replacement for the old valve. In order to save construction room and space, the hydraulic piston is designed as a hollow piston which routes the hydraulic medium in its inner region in the direction of the tank connection. The states are attained through the possibility of attaining different overlaps between the hydraulic hollow piston and the individual connections of the valve, according to the travel of the hollow piston. The overlaps lie between the bushing and the hollow piston of the cartridge valve. The systems are compatible with one another with regard to their connection points, such as control unit connection, hydraulic medium connection, and dimensions.
The valve which is described in greater detail in the following is distinguished by the fact that, because of the spatial arrangement of the T-connection relative to the other connections of the 4/4-way valve, the piston retains virtually no residual oil quantities in its first state. An effective contribution towards the pressure relief not just of the camshaft adjusting device, but also of the valve is also achieved through the two armature spaces and the hydraulic preloading of the tappet. Admission openings in the piston are disposed such that no forces against the equilibrium of forces of the valve are produced through the hydraulic medium flowing off to the T-connection.
The camshaft adjusting device is held, moved and set by means of the valve. Together with the camshaft, the camshaft adjusting device is a system which is selected and formed according to positions of equilibrium. If the camshaft adjusting device is switched pressureless, the camshaft, supported on its bearing points, drives a rotor of the camshaft adjusting device together with the camshaft into a dwell position. The defined dwell position is the position of the camshaft adjusting device which is selected automatically. The dwell position is influenced by equilibriums and supports.
A separate locking system may be provided in the camshaft adjusting device in order to attain a distinct dwell position. The locking mechanism, such as, for example, that from DE 102 53 883 A1, takes account of the pressure states in the hydraulic chambers. If the pressure in the hydraulic chambers lies below a certain value, which may be considered in simplified terms as a pressureless state, the camshaft adjusting device locks in and blocks in the selected position. If a pressure difference between the different hydraulic chambers is exceeded, unlocking takes place, the locking mechanism being unlocked.
The described valve and the corresponding camshaft adjusting device, together with an internal combustion engine and a relevant engine control unit, in particular an electronic engine control unit with one or a plurality of microcontroller(s), form a drive unit. The engine control unit separately delivers a signal through which the turn-off state, the operating end time state, is triggered. The turn-off state of the engine control unit is skillfully selected such that the valve also starts out from a turn-off state if the actual engine control unit fails or is turned off. The safety function is called a fail-safe function, because the system enters into a state which is equivalent to the operating end time state if the engine control unit fails or the electrical connections of the valve sustain a mechanical break.
The camshaft adjusting system and the associated internal combustion engine can be used according to a method according to the invention of operating an internal combustion engine, in particular in a motor vehicle, with an electronic engine control unit and a camshaft adjusting system. In the method the first state is taken up upon starting the internal combustion engine with co-ordination between the control unit and the camshaft adjusting system, in particular independently of the process of switching off the internal combustion engine. The start times of the drive train of the motor vehicle, for example the reset and start process of the engine control unit, are used to produce the pressureless state.
A better understanding of the described invention can be obtained by referring to the following figures, wherein
Tappet bores in the form of damping bores delay the method in the first state. Short oil pressure or energization interruptions of the coil are as a result compensated. Although the operation is carried out with a pressureless state, the camshaft adjusting system as a whole becomes more stable than known camshaft adjusting systems.
The openings, bores and ducts and the entire valve are graphically represented in a rotationally symmetrical manner. It is understood that the rotationally symmetrical form of the valve naturally has no influence on the implementation of the invention.
The piston 13 has three grooves, two webs and two end elevations, which lie in the two outer end regions of the tappet. The sleeve 15 comprises inner webs which, together with the sleeve, can block the connections relative to one another. A suitable valve may, for example, be designed such that there is an overlap of 0.2 to 0.4 mm between the sleeve 15 and the piston 13 in the region of the connection D to the groove of the T-outlet duct 79. The overlap between the P-connection and the connection B may vary between 0.25 and 0.45 mm. The overlap between the P-connection and the connection A exceeds 1 mm, being 1.5 mm, for example.
The valves depicted in the sectional drawings of
The described cartridge valve 1 is hydraulically connected directly or via lines of the engine compartment indirectly to a camshaft adjusting device, which is illustrated in an open representation in
The flow volumes are represented in
The characteristic idealized in
To summarize, it can therefore be maintained that, according to one aspect of the invention, known camshaft adjusting systems are developed by having selected a pressureless state as selectable and accessible state. A further aspect of the invention lies in the fact that a suitable valve has been designed which reliably permits the pressureless state of the camshaft adjusting system. The two aspects combined result in a camshaft adjusting system according to the invention. Existing camshaft adjusting systems can be changed into a system according to the invention by replacing the valve and directions for reprogramming the control unit of the internal combustion engine.
Number | Date | Country | Kind |
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10 2004 039 800 | Aug 2004 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2005/052547 | 6/27/2005 | WO | 00 | 5/8/2006 |
Publishing Document | Publishing Date | Country | Kind |
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WO2006/018330 | 2/23/2006 | WO | A |
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6053139 | Eguchi et al. | Apr 2000 | A |
6408807 | Komazawa et al. | Jun 2002 | B1 |
6684835 | Komazawa et al. | Feb 2004 | B2 |
6701877 | Ottersbach et al. | Mar 2004 | B1 |
6820578 | Kanada et al. | Nov 2004 | B2 |
20020023602 | Komazawa et al. | Feb 2002 | A1 |
Number | Date | Country |
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25 92 932 | Dec 2003 | CN |
38 24 205 | Jan 1990 | DE |
198 16 069 | Oct 1999 | DE |
198 47 705 | Apr 2000 | DE |
198 53 670 | May 2000 | DE |
1 316 723 | Jun 2003 | EP |
Number | Date | Country | |
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20080115751 A1 | May 2008 | US |