Device for adjusting the phase position between the camshaft and the crankshaft

Abstract

A device for adjusting the phase position between a camshaft and a crankshaft is provided. A quick and precise electronic adjustment for mechanical adjustment devices for adjusting the phase position between a camshaft and a crankshaft have previously not been known. The adjustment device is a component of an electronic circuit, either automatically adjusting the desired phase position directly or indirectly via another parameter, with the circuit including at least one loop between the control device and the adjustment path, by which a quick and precise adjustment can be achieved. Such arrangements are needed for a quick and precise adjustment of the phase position of a camshaft in reference to a crankshaft in internal combustion engines.

Description

BACKGROUND

The invention relates to a device for adjusting the phase position between a camshaft and a crankshaft of an internal combustion engine.

In internal combustion engines, the crankshaft drives one or more camshafts via a primary drive, provided, for example, as a toothed belt. For this purpose, a camshaft timing gear is mounted to each camshaft, by which the primary drive drives the camshaft. Here, at any time a transmission of the angle of rotation of the crankshaft occurs, in which a 720° angle of rotation of the crankshaft φ_K is transmitted into a 360° angle of rotation of the camshaft φ_N. Therefore, through this coupling the two angles of rotation are constant in reference to one another. In most applications, this fixed coupling of crankshaft and camshaft results in a ratio of $\frac{\phi N\left(t\right)}{\phi K\left(t\right)}=\frac{1}{2}$

However, the operational characteristics of an internal combustion engine can be optimized, particularly with regard of fuel consumption, exhaust emission, and running performance, when the system of camshaft and crankshaft, coupled via the primary drive, can be modified.

DE 100 38 354 A1 discloses an arrangement for adjusting the angle of rotation of a camshaft relative to a crankshaft using a wobble plate mechanism. Here, a second drive additionally acts on the camshaft via a wobble plate mechanism, which is arranged between the camshaft phasing gear and the camshaft. This causes the camshaft to be adjustable relative to the crankshaft.

SUMMARY

The objective of the invention is to provide a simple and cost effective adjustment device, by which the phase position between the camshaft and the crankshaft can be adjusted.

This objective is attained according to the invention. Here, the adjustment device is a component of an electronic circuit automatically adjusting the desired phase position either directly or indirectly via another parameter, with the circuit comprising a control device and a control path having a structure specified for that application.

The advantage of the invention lies in the fact that such an adjustment device, having such an electronic circuit, can adjust very quickly and precisely the desired value in the control path.

Advantageous further developments also result from the invention as further described below. Here, for example, the target value can be adjusted with the adjustment device even more quickly and more precisely by way of compensating variable disturbances, or by adjusting a cascading positioning or by way of a state control.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be explained in greater detail using three exemplary embodiments shown in the figures. In the drawings:

FIG. 1 is a schematic view of an adjustment device having a compensation for variable disturbances according to the invention.

FIG. 2 is a schematic view of an adjustment device having a cascading positioning adjustment in accordance with another embodiment of the invention.

FIG. 3 is a schematic view of an adjustment device having an optimized state control in accordance with another embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an adjustment device provided with a positioning control 1 having a compensation for variable disturbances 2. In state of the art mechanical phase adjustment devices, driven by electric motors, such as e.g., the ones known from DE 100 38 354 A1, the relative rotational speed of the electric motor is equivalent to the rotational speed of the sprocket or the belt pulley coupling the crankshaft with the camshaft, when the phase position remains unchanged. During the phase adjustment the relative rotational speed of the electric motor is faster or slower than the speed of the sprocket depending on the direction of the adjustment.

In the present exemplary embodiment the effect of the variable disturbance of the crank shaft rotational speed z is not collected only when it effects the control variable, but is already used for the pre-adjustment of the adjustment member 3. For example, the rotational speed of the sprocket or the belt pulley can be determined from the rotational speed of the crankshaft. The rotational speed z can be related to a corresponding self-inducting voltage y_R at the electric motor.

In FIG. 1, the target value w, in the exemplary embodiment the desired phase position, is entered into the control 4. The target value w acts on the electric motor of the adjustment member in the control path 3, e.g., a wobble plate mechanism. This causes the rotational speed of the sprocket or the belt pulley to change, resulting in a modified phase position. The actual value x of the phase position and/or the rotational speed of the sprocket or the belt pulley is fed back. The returned actual value determines the new target value for the control. This new target value is then fed to the control. The compensation for variable disturbances 2 is formed such that, additionally, from the rotational speed of the crankshaft z the self-induction voltage y_z is determined as an additional adjustment parameter for the electric motor of the adjustment member, also determining the rotational speed of the electric motor.

FIG. 2 shows an adjustment device having a cascading positioning control. In order to improve the adjustment times and to achieve higher dynamics in the circuit, here, several circuits are nested parallel to one another. Here, disturbances are compensated in the subordinate circuits, before they can have any effect on the superordinate circuits. In the present exemplary embodiment, the positioning control, provided with a positioning return, is provided with a subordinate rotational speed control of the electric motor, which is provided with a feed back of the angular speed. Here, the rotational speed and/or the angular speed of the electric motor can be determined in the form of a measurement or can be calculated indirectly via the trigger information of the camshaft and the crankshaft. Furthermore, the rotational speed control is cascaded by a control of the armature current, in which an additional compensation control can improve the dynamics. The control of the armature current and/or the measurement of the armature current can also occur via a measurement of the torque of the electric motor driving the adjustment device. In this exemplary embodiment, a target rotation angle φs is given, describing the position and/or phase position between the camshaft and the crankshaft. Depending on the angle φs the rotational speed and/or the angular speed ωs is given for the electric motor. The angular speed itself is determined by the torque of the electric motor. The torque M_L and/or the corresponding current is measured and returned and here compared with the corresponding target value Ms. When the values do not coincide, appropriate readjustments are made. Simultaneously the superordinate actual value ω of the angular speed is measured and subsequently returned for comparison to its target value ωs. In the event of any discrepancies, here too appropriate readjustments are made. Finally, the actual phase position φ is determined as well, returned, and adjusted to the target value φs.

FIG. 3 shows an adjustment device having a state control. Through the use of the state control, the dynamics of the control system are largely determined, because the conditions determining the dynamics directly enter the control. If the condition to be determined cannot be measured directly, it may be calculated by way of a state observer and/or a state equation.

Here, a time controlled input value w(t) is entered in to a pre-filter 5. The pre-filter generates an output value u_w(t) therefrom, which forms together with a value u_r(t) created by a state control 6 an input value u(t) for the state differential equation 7. Furthermore, the actual value x(t₀) at the time to is fed to the state differential equation 7. Using these values the state differential equation 7 calculates the state x(t). The state can be measured either directly or indirectly via a measuring device 8, with the measurement being able to influence the state control 6, which again influences the input value u(t) for the state differential equation 7. Additionally, the actual value x(t) can be fed to the output equation 9 for further processing, which then creates an output value y(t) for the control path 10. In the circuit shown, the control path 10 is formed by the state differential equation 7 and the output equation 9, which create the variable control. The control device 11, controlling the variable control, is essentially formed by the measuring device 8 and the state control 6. In the exemplary embodiment the control device 11 also includes the pre-filter 5.

All exemplary embodiments may be combined with one another in various ways depending on the particular application.

Claims

1. An electronically driven mechanical adjustment device for adjusting a phase position (φ) between a camshaft and a crankshaft, comprising an adjuster that is part of an electronic circuit, for automatically adjusting a desired phase position (φ) between the camshaft and the crankshaft, and the circuit including at least one loop, in which an output value is fed back to the input.

2. An adjustment device according to claim 1, wherein the electronic circuit includes a compensation for variable disturbances (2).

3. An adjustment device according to claim 1, wherein the electronic circuit includes several control loops, nested parallel in a cascading fashion, with at least one circuit being superordinate to another one.

4. Control device according to claim 1, wherein the circuit in which the adjustment device is arranged includes a state control (10, 11).