Camshaft adjuster with belt drive

Abstract

Camshaft adjuster (100) with a belt drive for an internal combustion engine comprising a stator (2) driven by a crankshaft of the internal combustion engine via a belt, a rotor (3) non-rotatably connected to the camshaft (1), working chambers (4) arranged between the stator (2) and the rotor (3) which can be pressurized with oil, the working chambers (4) being subdivided into opposing pressure chambers (24, 25) by vanes (23) associated with the rotor (3), wherein a central valve (26) with a piston (8) guided longitudinally displaceably in the central valve (26) is provided for controlling the oil pressure in the pressure chambers (24, 25) of the working chambers (4), which can be actuated with a force by an actuator (6) from a control side (A) of the camshaft adjuster (100), wherein oil pressure lines (31, 32) opening into the pressure chambers (24, 25) are provided, wherein the A central valve (26) is provided for controlling the oil flows into the oil pressure lines (31, 32),and the central valve (26) is inserted into a hollow central screw (5) that connects the rotor (3) to the camshaft (1), wherein the central valve (26) is formed from a hydraulic part (27) and a piston (8) which is guided longitudinally displaceably in the hydraulic part (27), wherein the oil pressure from an oil supply line (11) in the camshaft (1) is supplied to the oil pressure lines (31, 32) depending on the position of the piston (8), and the camshaft adjuster (100) has a seal (10, 17) on its actuation side (A) which prevents the oil flow from escaping into the installation space (B) accommodating the belt drive, characterized in that the seal (17) is formed by a bellows seal which is firmly connected to the camshaft adjuster (100) with its radially outer edge, and is connected centrally to a part (21) associated with the piston (8), on which the Actuator (6) is connected.

Description

[0001] The invention relates to a camshaft adjuster with belt drive having the features of the preamble of claim 1.

[0002] Camshaft adjusters are commonly categorized into two classes: chain-driven and belt-driven. Driven by a crankshaft via a belt or chain, the camshaft adjuster's function is to adjust the opening and closing times of the valves in an internal combustion engine. By adjusting these opening and closing times, the engine's fuel consumption and performance can be optimized, which is essential for modern engines due to high energy prices and stricter environmental regulations. The camshaft adjuster itself consists of a stator, driven by the crankshaft via a belt or chain, and a rotor, which is fixed to the camshaft.Between the rotor and the stator, working chambers are provided, which in turn are divided into two opposing pressure chambers by vanes arranged on the rotor.

[0003] To adjust the rotational angle of the rotor relative to the stator, and thus of the camshaft relative to the crankshaft, camshaft adjusters with chain drive, for example, incorporate a central valve. This valve is actuated by a solenoid located coaxially within a stationary engine structure. The central valve comprises a stationary hydraulic section and a piston that slides longitudinally within the hydraulic section. Both the hydraulic section and the piston contain oil channels that are interconnected depending on the piston's position. The oil channels in the hydraulic section are also connected to the working chambers and can be selectively pressurized depending on the piston's position, allowing the oil pressure in the working chambers to be controlled according to the piston's position.By changing the pressures in the working chambers, the rotation angle of the rotor relative to the stator, and thus the opening and closing times of the gas exchange valves, can be altered. During rotor adjustment, one pressure chamber is pressurized with an oil flow, while the oil from the pressure chamber on the other side of the rotor flows into a tank formed here by the chain case.

[0004] Such an outflow of oil into the belt housing (which corresponds to the chain case in belt drives) is unacceptable, as the belt drive must not run in oil. For this reason, the use of a central valve is not currently possible with belt-driven camshaft adjusters.

[0005] DE 698 09 586 T2 discloses a phase adjustment mechanism for an engine camshaft, which enables a change in the valve control of the engine so that it can be adapted to different operating conditions.

[0006] The AT 70 892 E shows an adjustment of a camshaft by a control valve.

[0007] German patent DE 10 2004 039 800 A1 discloses a camshaft adjustment system with a camshaft adjuster having two counter-rotating hydraulic chambers, comprising in particular a swivel motor camshaft adjuster and a control valve assembly. The control valve assembly of the camshaft adjustment system operates as a 4 / 4 valve. It has one connection for the first and one connection for the second hydraulic chamber. It also includes a tank connection and a connection for pressurization. The camshaft adjustment system is characterized by the fact that, in a first state, the unpressurized state, it is relieved of pressure by the valve. This is achieved by simultaneously hydraulically connecting the hydraulic chamber connections of the camshaft adjuster to the tank connection.

[0008] DE 10 2006 012 733 A1 discloses a valve and a suitable hydraulic circuit, in particular for camshaft adjusters of an internal combustion engine, in which a number of check valves or two-way valves functioning like check valves are placed to create a fast camshaft adjuster with high control quality.

[0009] DE 38 72 963 T2 discloses a valve timing control device for use in an internal combustion engine for continuously controlling or varying the valve timing of an intake or exhaust valve. A camshaft adjuster of this type is known from DE 10 2004 025 215 A1.

[0010] The task is to create a camshaft adjuster with a belt drive, whose oil flow is controlled via a central valve.

[0011] The object is solved according to the invention by a camshaft adjuster having the features of claim 1, while advantageous further developments can be found in the dependent claims.

[0012] According to the invention, to solve the problem, it is proposed that a central valve with a piston guided longitudinally displaceably in the central valve is provided for controlling the oil pressure in the pressure chambers of the working chambers, which can be acted upon by an actuator from a control side of the camshaft adjuster with a force, and the camshaft adjuster has a seal on its control side that prevents the oil flow from escaping into the installation space accommodating the belt drive.

[0013] Due to the solutions according to the invention, it is possible to control the camshaft adjuster with belt drive via a central valve without the draining oil being able to enter the installation space accommodating the belt drive, also called belt box.

[0014] According to the invention, the seal is formed by a bellows seal, the radial outer edge of which is rigidly connected to the camshaft adjuster, and the middle section of which is connected to a part associated with the piston against which the actuator rests. The bellows seal has the advantage of completely sealing the camshaft adjuster itself, preventing oil from escaping on this side and potentially entering the belt drive assembly. Furthermore, the bellows seal has the advantage of being designed as a static seal. Static seals are generally less susceptible to wear and simpler in design, resulting in a better sealing effect over the service life of the component being sealed and a lower cost. Another advantage of the bellows seal is that it can accommodate axial movements of the components, particularly the piston, without losing its sealing effect.

[0015] It is further proposed that the part connected centrally to the bellows seal and the piston be formed as a single piece. This directly converts the positioning movement of the actuator attached to the part into a movement of the piston, which is advantageous for the accuracy of the movement sequence of the interacting parts. Furthermore, this reduces the number of parts, which in turn is beneficial with regard to manufacturing, parts inventory, and reliability in continuous operation.

[0016] Alternatively, it is proposed that the part connected centrally to the bellows seal rests against the piston face in such a way that only compressive forces can be transmitted. This can be achieved very simply, for example, by forming the part connected centrally to the bellows seal and the piston from two separate parts. This prevents unintentional pressure fluctuations, especially negative pressures, from causing the bellows seal to pull the piston out of its intended position.

[0017] In an unclaimed embodiment, a camshaft adjuster according to the preamble of claim 1 comprises a sleeve which encompasses the piston exiting the central valve and the piston in a bore arranged coaxially to the central valve in a component wall of the installation space accommodating the belt drive. A seal is arranged between the sleeve and the camshaft adjuster. Since the component wall is stationary and the camshaft adjuster rotates, either the seal between the sleeve and the camshaft adjuster or a second seal between the sleeve and the component wall must be designed as a dynamic seal, e.g., a radial shaft seal. The sleeve has the advantage that the design of the seal prevents any axial forces acting on the piston that could lead to incorrect piston adjustment.

[0018] In this case, oil drainage can be achieved very simply by having the sleeve penetrate the component wall and have bores on its side of the component wall facing away from the camshaft adjuster, through which the oil drained from the pressure chambers escapes.

[0019] The piston can be hollow, and the oil drained from the pressure chambers can be guided through the piston to an oil drain bore located outside the installation space accommodating the belt drive.

[0020] The invention is described in more detail below by means of preferred embodiments, which can be seen in detail in the figures: Fig. 1: Camshaft adjuster with sealed sleeve, Fig. 2: Camshaft adjuster with bellows seal, Fig. 3: Camshaft adjuster with bellows seal and intermediate piece, Fig. 4: Basic structure of a camshaft adjuster with radial piston.

[0021] In Fig. Figure 4 shows the basic structure of a camshaft adjuster 100 for better understanding. The camshaft adjuster 100 consists of a stator 2 and a rotor 3 arranged in a cavity of the stator 2. The stator 2 is supported on the rotor 3 by radially inwardly directed projections, thus dividing the annular space between the stator 2 and the rotor 3 into working chambers 4. Furthermore, vanes 23 are provided on the rotor 3, which project into the working chambers 4 and, in turn, divide these into opposing pressure chambers 24 and 25. Oil pressure lines 31 and 32 open into the pressure chambers 24 and 25, through which the pressure chambers 24 and 25 can be pressurized with oil. When pressure is applied to the pressure chamber 24, the rotor 3 is rotated clockwise relative to the stator 2, and when pressure is applied to the pressure chamber 25, it is rotated counterclockwise.When pressure is applied to one of the pressure chambers 24 or 25, the oil is drained from the other pressure chamber 24 or 25, so that the adjustment movement cannot be disturbed.

[0022] In Fig. Figure 1 shows a camshaft adjuster 100 according to the invention, comprising a stator 2 driven by a belt 14 from a crankshaft of an internal combustion engine and a rotor 3 non-rotatably connected to the camshaft 1. A hollow central screw 5 is provided for connecting the rotor 3 to the camshaft 1, and a central valve 26 is provided in the screw for controlling the oil flow into the oil pressure lines 31 and 32. The central valve 26 itself consists of a hydraulic part 27 and a piston 8 which is guided longitudinally displaceably within the hydraulic part 27.

[0023] An oil supply line 11 is provided in the camshaft 1, through which the camshaft adjuster 100 can be pressurized with oil pressure, which is then supplied to the oil pressure lines 31 and 32 depending on the position of the piston 8. The oil routing in the hydraulic part 27 and the piston 8 is not discussed further here, as it is not modified by the invention and belongs to the prior art.

[0024] On the control side “A” of the camshaft adjuster 100, an actuator 6, designed as a solenoid, is fixedly held in the housing of the internal combustion engine and acts on the piston 8 of the central valve 26 via a plunger 7. The installation space “B” of the belt drive, also called the belt box, of the camshaft adjuster 100 is encapsulated by a component wall 28, so that, as described later, it does not run in oil.

[0025] In the component wall 28 separating the actuator 6 and the camshaft adjuster 10, a bore 20 is provided coaxially to the central valve 26 of the camshaft adjuster 100 and the tappet 7 of the actuator 6. A sleeve 9 is arranged in this bore and sealed by a static seal 29. The sleeve 9 extends at one end towards the camshaft adjuster 100 as far as the central screw 5 and at the other end to the actuator 6. In the area of ​​the overlap of the sleeve 9 and the central screw 5, a dynamic seal 10, designed as a radial shaft seal, is provided to prevent oil from the camshaft adjuster 100 from penetrating into the installation space "B".Between the end of the sleeve 9 that rests against the actuator 6 and the component wall 28, bores 12 are provided in the sleeve 9. Oil draining from the pressure chambers 24 and 25 can escape through these bores into a free space 13 of the internal combustion engine. From there, it is supplied via a pump (not shown) through the oil supply line 11 during the next actuation of the camshaft adjuster 100. In addition to the oil drainage via the bores 12, oil can also drain through a through-bore 15 in the piston 8 to the oil drain bore 16 located on the camshaft 1. This ensures that the oil drains from both sides, in accordance with arrow directions T1 and T2, preventing the build-up of axial forces in the camshaft adjuster 100 that could lead to an undesired adjustment of the rotor 3 relative to the stator 2.

[0026] In Fig. Figure 2 shows an alternative embodiment of the invention in which a bellows seal 17 is provided on the actuation side “A” of the camshaft adjuster 100. The bellows seal 17 is firmly held at its radially outer edge by the central screw 5 and, above this, by the camshaft adjuster 100. The bellows seal 17 is connected centrally to the piston 8 of the central valve 26. This seals the annular gap between the central valve 26 and the central screw 5, preventing oil from entering the installation space “B” which accommodates the belt drive 14 on this side. The actuator 6, with a plunger 7, rests centrally against the piston 8 on the outer side of the bellows seal 17. When the actuator 6 is actuated, a pressure force is exerted on the piston 8 via the plunger 7, causing the piston 8 to be displaced axially against the spring 22.

[0027] In this embodiment, the application of pressurized oil is identical to that described in Fig. In the embodiment shown in Figure 1, the oil is returned through the oil supply line 11 in the direction of arrow "P". The oil is then returned from the pressure chambers 24 and 25 through the bores 18 and 19 into the cavity of the piston 8 and further through the central screw 5 and through the oil drain bore 16 in the direction of arrow "T" to a tank from which it can be fed back to the oil supply line 11 in the direction of arrow "P" via an oil pump. The bellows seal 17 used has the clear advantage that it can perform axial movements together with the piston 8 without losing its sealing effect. Moreover, the bellows seal 17 is a static seal connected to the central screw 5 and the piston 8, which exhibits a very reliable sealing effect even in continuous operation. This is particularly advantageous because the camshaft adjuster in the internal combustion engine is very difficult to access and replacement is only possible with considerable effort and associated costs.

[0028] In the Fig. 3 is opposite to the Fig. Figure 2 shows a further developed embodiment of the invention, in which the seal is also implemented by a bellows seal 17. In contrast to the embodiment shown in Figure 2, the seal is further developed by a bellows seal 17. Fig. In this case, the bellows seal 17 is connected centrally to an intermediate piece 21, which rests against the piston 8. The adjustment movement of the piston 8 is then effected by the plunger 7 of the actuator 6, which rests against the intermediate piece, against the spring 22. In the event that pressure fluctuations occur in the central valve 26 and the bellows seal is unintentionally deflected against the plunger 7, this ensures that the bellows seal 17 does not pull the piston 8 along with it and thereby cause an unintentional adjustment of the rotation angle of the camshaft 1 relative to the crankshaft.

Claims

[1] Camshaft adjuster (100) with a belt drive for an internal combustion engine comprising a stator (2) driven by a crankshaft of the internal combustion engine via a belt, a rotor (3) non-rotatably connected to the camshaft (1), working chambers (4) arranged between the stator (2) and the rotor (3) which can be pressurized with oil, the working chambers (4) being divided by vanes (23) associated with the rotor (3) into opposing pressure chambers (24, 25), wherein a central valve (26) with a piston (8) being longitudinally displaceable in the central valve (26) is provided for controlling the oil pressure in the pressure chambers (24, 25) of the working chambers (4), which can be actuated with a force by an actuator (6) from a control side (A) of the camshaft adjuster (100), wherein oil pressure lines (31, 32) opening into the pressure chambers (24, 25) are provided are, wherein the central valve (26) is provided for controlling the oil flows into the oil pressure lines (31, 32),and the central valve (26) is inserted into a hollow central screw (5) which connects the rotor (3) to the camshaft (1), wherein the central valve (26) is formed from a hydraulic part (27) and a piston (8) which is guided longitudinally displaceably in the hydraulic part (27), wherein the oil pressure from an oil supply line (11) in the camshaft (1) is supplied to the oil pressure lines (31, 32) depending on the position of the piston (8), and the camshaft adjuster (100) has a seal (10, 17) on its actuation side (A) which prevents the oil flow from escaping into the installation space (B) which accommodates the belt drive, , characterized by , that the seal (17) is formed by a bellows seal which is firmly connected with its radial outer edge to the camshaft adjuster (100) and is connected in the middle to a part (21) associated with the piston (8) against which the actuator (6) rests. [2] Camshaft adjuster (100) according to claim 1, characterized by, that the part (21) connected centrally to the bellows seal (17) and the piston (8) are formed in one piece. [3] Camshaft adjuster (100) according to claim 1, characterized by , that the part (21) connected centrally to the bellows seal (17) rests against the front face of the piston (8) in such a way that only pressure forces can be transmitted.

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