EP2425104A1

EP2425104A1 - A control arrangement for an inlet valve in a piston engine

Info

Publication number: EP2425104A1
Application number: EP10718624A
Authority: EP
Inventors: Magnus Sundsten; Leif Knipström
Original assignee: Wartsila Finland Oy
Current assignee: Wartsila Finland Oy
Priority date: 2009-04-27
Filing date: 2010-04-09
Publication date: 2012-03-07
Anticipated expiration: 2030-04-09
Also published as: CN102414402B; WO2010125235A1; KR20120016068A; CN102414402A; KR101628424B1; FI20095462A; FI20095462A0; EP2425104B1; FI121512B

Abstract

The invention relates to a control arrangement for an inlet valve in a piston engine adapted between a cam device (5) of a camshaft (4) of the engine (1 ) and an inlet valve mechanism (6) arranged to open and close the inlet valve (3) in association with a cylinder of the engine, which control arrangement (7) comprises a body part (8), in which a piston device (9) is movably arranged to be in force transmission connection with the camshaft (4) and the valve mechanism (6), said body part (8) and the piston device (9) together defining a first chamber (13), into which hydraulic medium can be selectively fed, and a second chamber (19) connected to the first chamber via duct means (18,18', 18"), the flow of hydraulic medium from the first chamber (13) to the second chamber (19) being controlled for providing a delay in the closing of the inlet valve (3). The body p a r t ( 8 ) i s provided with two or more flow ducts (18a,18b,18c;18'a,18'b;18"a,18"b,18"c) for arranging different routes for the flow of hydraulic medium from the first chamber (13) to the second chamber (19). Control means (17, 17', 17") are provided for selecting the route of flow to be utilised in each case to provide different closing delay.

Description

A CONTROL ARRANGEMENT FOR AN INLET VALVE IN A PISTON ENGINE

Technical field

The invention relates to a control arrangement for an inlet valve in a piston en- gine according to preamble of claim 1.

Background art

There are situations in the operation of a four stroke internal combustion engine in which the cylinders are not provided with enough air for self-ignition to hap- pen during the compression stroke. This is specifically true as regards engines charged by high pressure such as two-stage turbo charged engines during engine start and during load variations. In engines of this kind higher pressures in combination with sharper or shorter cam nose forms are utilised resulting in charging action taking place in shorter time respectively. Hence, the opening times of the inlet valves under normal load of the engine are not long enough for such special situations.

On the other hand in order to minimise emissions from a diesel engine the timing of the inlet valves needs to be such that the inlet valve is closed early before the bottom dead centre of the piston, while the boost pressure is raised accord- ingly so as to get a sufficient amount of air to the cylinder. This kind of arrangement is, however, problematic with low engine loads, when the boost pressure of the turbocharger is still relatively low.

One solution could be intensified supply of inlet air during the opening phase of the inlet valve under such special situations. Another solution is to provide for a delay in the closing of the inlet valve for prolonging the opening time of the inlet valve when needed. One solution for such a variable inlet valve closure (VIC) is disclosed in patent publication WO 2008/000899 providing a certain delay for the closing of the inlet valve. An object of the invention is to provide a further improved control arrangement for delaying the closing of the inlet valve in a piston engine. A particular aim is to enable selection of different delaying times to comply with different situations, especially when combustion engines are operated under low engine loads and during start of the engines.

Disclosure of the invention

The objects of the invention can be met substantially as is disclosed in claim 1 and in the other claims presenting more details of different embodiments of the invention. According to the invention the body part is provided with two or more flow ducts for arranging different routes for the flow of hydraulic medium from the first chamber to the second chamber. In addition control means are provided for selecting the route of flow to be utilised in each case to provide different closing delay. A route may here include one or more flow ducts depending on the application in each case. Hereby it is possible to obtain a solution which is easy to put into practice, reliable and can be utilised according to need.

The two or more flow ducts are with advantage arranged to open in a common chamber or the like connection duct arranged in communication with the first chamber. Then the control means are arranged to operate in said common chamber or the like connection duct.

In practice it is of advantage that the second chamber is provided within a guide member arranged between the cam device and the piston device to be movably responsive with the movements of cam device. Thereby the two or more flow ducts are arranged to open into the second chamber at different positions along the track of movement of the guide member. This provides for a reliable construction. In addition the guide member is arranged to directly act on the piston device only in the direction for opening the inlet valve, when the delaying function is utilised.

According to one embodiment the flow of hydraulic medium is arranged via one of said flow ducts at a time and that the control means include a control valve with a movable valve member provided with a releasing means to be arranged at the position of one of said flow ducts. The releasing means can be a narrowing portion dimensioned to allow flow only through one duct at a time.

According to another embodiment the control arrangement includes a separate control valve for each of the flow ducts providing for a shortened delaying time.

The control means are with advantage arranged to be operated pneumatically by making use of the control systems included in the engine. Specifically charge air from a turbocharger of said piston engine can be utilised for controlling the control means. The operating pressure is with advantage arranged to occur against the force of a spring providing uncomplicated construction and control.

Brief Description of Drawings

In the following the invention will be described, by way of example only, with reference to the accompanying schematic drawing, in which

- Figure 1 shows a piston engine and a skeleton diagram of its valve mechanism,

- Figures 2 - 4 show a general view of a control arrangement according to the invention in separate consecutive stages of operation,

- Figure 5 shows an enlarged view of a first embodiment of control means ac- cording to the invention,

- Figures 6a and 6b show an enlarged view of a second embodiment of control means according to the invention in two operation positions,

- Figure 7 shows a relative opening curve of the inlet valve relating to the embodiment of figure 6a, and

- Figure 8 shows an enlarged view of a third embodiment of control means according to the invention. Detailed Description of Drawings

Figure 1 shows a schematic view of a piston engine 1 as far as it is relevant to the understanding of the invention. The gas exchange of the cylinders (not shown) in the piston engine 1 is carried out under the control of gas exchange valves, i.e. inlet valves and exhaust valves, located on a cylinder head 2. Only inlet valves 3 are shown and they are operated by means of valve mechanisms

6 which are typically guided by cam profiles 5' of cam devices 5 arranged on a camshaft 4 of the engine. The force transmission connection between each valve mechanism 6 and the corresponding cam device 5 is realised by a control arrangement 7.

The control arrangement 7 is shown in more detail in Figures 2 - 4, of which Figure 2 shows it in a non-operating state, whereby the inlet valve 3 in connection therewith is closed. The control arrangement 7 comprises a body part 8, which is typically attached to the engine body. A piston device 9 is movably arranged within the body part 8. The upper end of the piston device 9 is arranged in force transmission connection with the valve mechanism 6. This connection is in this case mechanical, but it could be hydraulic as well. The movements of the piston device 9 are controlled by a guide member 10 arranged at the lower end of the piston device within the body part 8. The guide member 10 is in engagement with and urged by a spring 11 towards a roller 12, which receives its guidance from the cam profile 5' of the cam device 5. Thus, when the cam shaft 4 rotates, in figures 2 - 4 in clockwise direction, the roller 12 follows the cam profile 5' of the cam device 5, and the changes in the cam profile 5' are transmitted so as to affect the opening and closing of the inlet valve 3.

The body part 8 and the piston device 9 together define a first chamber 13, into which hydraulic medium can be selectively fed via a feed duct 14, as indicated by arrow, for providing a delay in the closing of the inlet valve 3. In practice the feed duct is with advantage provided with a shut-off valve and a non-return valve, not shown. By means of the shut-off valve the feed line to the first chamber 13 may be connected or disconnected, depending on whether or not the aim is to use the delay function for the delayed closing of the inlet valve 3. Due to the non-return valve the control arrangement cannot cause any pulsations in the source of hydraulic medium. This is of importance when lubricating oil is used as a hydraulic medium.

The body part 8 is additionally provided with ducts 15 and 18 by means of which the first chamber 13 can be connected with a second chamber 19, which is located in the guide member 10. For this purpose the guide member 10 is provided with an aperture 10a. When the aperture 10a is at the position of the downward end opening of the duct 18 the flow connection between the cham- bers 13 and 19 is established. In addition, between the ducts 15 and 18 there is a chamber 16 or the like duct which includes control means 17 in accordance with the invention, the construction and operation of which is described more in detail below.

So in figure 2 the control arrangement 7 is in a non-operating state and the roller 12 is located on the base circle of the cam profile 5'. In figure 3 the cam device 5 has rotated clockwise so that the nose in the cam profile 5' has lifted the roller 12 upwards in the figure. Thus, also the guide member 10 and the piston device 9 have moved upwards and as a consequence the corresponding inlet valve 3 (not shown) has opened. Simultaneously the first chamber 13 is filled with hydraulic medium fed through the feed duct 14.

In figure 4 the roller 12 has returned on the base circle of the cam profile 5'. Due to the hydraulic medium in the first chamber 13 the piston device 9 remains first in its top position thereby keeping the inlet valve also open. As can be seen in figure 4 the engagement between the piston device 9 and the guide member 10 is hereby disconnected. Thereafter, when the aperture 10a of the guide member 10 is moved at the position of the opening of duct 18 the pressure in the first chamber 13 is released and the piston device 9 starts to move downwards in the figure thereby allowing also the inlet valve to close. Then also the contact between the piston device 9 and the guide member 10 is re-established. The hydraulic medium flows further from the chamber 19 to an oil sump providing lubrication for the camshaft and the parts connected therewith. In case the variable inlet valve closure (VIC) function related to the chamber 13 is not utilised the piston device 9 is in continuous connection with the guiding member 10 and the communication between the chamber 13 and the chamber 19 is established in a normal way.

Figure 5 shows a first embodiment of control means 17 according to the invention. The chamber 16 is provided with three ducts 18a, 18b and 18c which each can be arranged in communication with the chamber 19 via the aperture 10a by means of the control means 17, which include a control valve 17a movable in a chamber 20 located in the body part 8. The control valve 17a is provided with a valve member 17b and releasing means 17c, which in this case is a groove circumventing the valve member 17b. In figure 5 the releasing means 17c is at the position of the duct 18b, whereby communication between the chambers 13 and 19 is established through this duct 18b. As obvious from the figure the end openings of the ducts 18a, 18b and 18c are at different height. This means that during the movement of the guide member 10 the end openings of these ducts will be at the position of the aperture 10as at different time, whereby the releasing of pressure in chamber 13 will occur at different time respectively. This entails different delay of the closing of the inlet valve depending, thus, on the duct selected in each case.

The operation of the valve means 17 can with advantage be accomplished pneumatically by feeding pressure air into the chamber 20, as indicated by the arrow, which will result in urging the control valve 17a with the valve member 17b to the left in the figure against the force of a spring 21. Thus, the movement of the control valve 17a and the selection of the respective duct 18a, 18b and 18c is dependent on the pressure of the air to be fed into the chamber 20. Preferably the control systems of the engine should be availed of so that for instance the charge air from a turbocharger of the engine is utilised. Hereby variation in inlet valve closing can be accomplished more or less automatically as a function of the charge air pressure being dependent on the load of the engine in each case. Figures 6a and 6b disclose another embodiment of the control means 17'. In this case the chamber 16' which is formed as a connection duct is operationally connected with a control valve 17'a, a control member 17'b of which controlling the communication between the chamber 16' and a second duct 18'b. The con- trol valve 17'a is located in a chamber 20' into which pressure air is fed to urge it against the force of a spring 21 '. When the connection between the chamber 16' and the duct 18'b is closed, as shown in figure 6b, the communication between the chambers 13 and 19 is established via the duct 18'a. On the other hand when the connection between the chamber 16' and the duct 18'b is open, as shown in figure 6a, the communication between the chambers 13 and 19 is established earlier via the duct 18'b the end opening of which being above the end opening of the duct 18'a. However, also in this case the duct 18'a remains open, and there is no need to have a separate control valve for closing it.

The operation of the embodiment of figures 6a and 6b and its effect on the de- lay of the closing of the inlet valve of the engine is illustrated in figure 7 showing the relative opening curve of the inlet valve as a function of the cam angle of the engine. Curve C shows a situation, in which hydraulic medium is not led at all to the chamber 13, whereby the inlet valve control is carried out merely determined by the cam profile 5'. Curves A and B relate to the situation, in which hy- draulic medium is led to the chamber 13, while the piston device 9 moves in the opening direction of the inlet valve. It is thus possible to provide a delay in the closing of the inlet valve in relation to its normal operation e.g. in different load situations of the engine. The curve A relates to a situation when the delay is affected by selecting the communication between the chambers 13 and 19 via the duct 18'a, the control valve 17'a thus being in a position closing the duct 18'b as shown in figure 6b. The curve B then represents a situation corresponding to figure 6a, according to which the control valve 17'a is open and allows communication via the duct 18'b. Hereby the releasing of pressure in the chamber 13 occurs earlier and the inlet valve, thus, is closed earlier as well, but the closing is still delayed in comparison with the normal situation depicted by the curve A.

Figure 8 discloses a third embodiment of the control means according to the invention. This is a variation of the embodiment of figures 6a and 6b, which in- dudes a third duct 18"c in addition to the ducts 18"a and 18"b. As can be seen the end openings of each of these ducts is located at different height, that is at different position along the return movement of the guide member 10, thereby providing a possibility for changing the delay of the closing of the inlet valve. In principle a number of further ducts 18" could be provided as well depending on the need for closer variation of the delay available in each case for the closing of the inlet valve in question, and the space available in the body part 8 in the engine respectively.

In case of the embodiments of figures 6a, 6b and 8 the control valves 17, 17' and 17" can be operated by means of any pressure medium preferably available in the engine, i.e. pneumatic, hydraulic, or also electrically. The control of the control valves and the selection of the flow duct in each case can be arranged by making use of pressure sensors for each control valve and due control logic so as to determine the needed delay in each case and to ensure cor- rect operation of the control valves accordingly.

The invention is not limited to the examples mentioned above but can be implemented in many other different embodiments within the scope of the inventive idea and the attached claims.

Claims

1. A control arrangement for an inlet valve in a piston engine adapted between a cam device (5) of a camshaft (4) of the engine (1 ) and an inlet valve mechanism (6) arranged to open and close the inlet valve (3) in association with a cylinder of the engine, which control arrangement (7) comprises a body part (8), in which a piston device (9) is movably arranged to be in force transmission connection with the camshaft (4) and the valve mechanism (6), said body part (8) and the piston device (9) together defining a first chamber (13), into which hydraulic medium can be selectively fed, and a second chamber (19) connected to the first chamber via duct means (18,18', 18"), the flow of hydraulic medium from the first chamber (13) to the second chamber (19) being controlled for providing a delay in the closing of the inlet valve (3), characterised in that the body part (8) is provided with two or more flow ducts (18a,18b,18c;18'a,18'b;18"a,18"b,18"c) for arranging different routes for the flow of hydraulic medium from the first chamber (13) to the second chamber (19), and that control means (17,1 T , 17") are provided for selecting the route of flow to be utilised in each case to provide different closing delay.

2. A control arrangement according to claim 1 , characterised in that the two or more flow ducts (18a,18b,18c;18'a,18'b;18"a,18"b,18"c) are arranged to open in a common chamber (16,16', 16") or the like connection duct arranged in communication with the first chamber (13), and that the control means (17,1 T , 17") are arranged to operate in said common chamber (16,16', 16") or the like connection duct.

3. A control arrangement according to claim 1 or 2, characterised in that the second chamber (19) is provided within a guide member (10) arranged between the cam device (5) and the piston device (9) to be movably responsive with the movements of cam device (5), and that the two or more flow ducts (18a,18b,18c;18'a,18'b;18"a,18"b,18"c) are arranged to open into the second chamber (19) at different positions along the track of movement of the guide member (10).

4. A control arrangement according to claim 3, characterised in that the guide member (10) is arranged to directly act on the piston device (9) only in the direction for opening the inlet valve (3).

5. A control arrangement according to any one of the preceding claims, characterised in that the flow of hydraulic medium is arranged via one of said flow ducts (18a,18b,18c) at a time and that the control means (17) include a control valve (17a) with a movable valve member (17b) provided with a releasing means (17c) to be arranged at the position of one of said flow ducts (18a,18b,18c).

6. A control arrangement according to claim 5, characterised in that the releasing means (17c) is a narrowing portion dimensioned to allow flow only through one duct (18a,18b,18c) at a time.

7. A control arrangement according to any one of the claims 1 -4, characterised in that it includes a separate control valve (17'a,17"a) for each of the flow ducts (18'b;18"b,18"c) providing for a shortened delaying time.

8. A control arrangement according to any one of the preceding claims, characterised in that the control means (17,1 T , 17") are arranged to be operated pneumatically, preferably against the force of a spring, by making use of the control systems included in the engine.

9. A control arrangement according to claim 8, characterised in that charge air from a turbocharger of said piston engine is arranged to be utilised for controlling the control means (17,1 T , 17").