| Arrays for controllable power supply of electrovalves of an electrohydraulic valve control -> Monitor Keywords |
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Arrays for controllable power supply of electrovalves of an electrohydraulic valve controlRelated Patent Categories: Internal-combustion Engines, Poppet Valve Operating Mechanism, Hydraulic SystemArrays for controllable power supply of electrovalves of an electrohydraulic valve control description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060137633, Arrays for controllable power supply of electrovalves of an electrohydraulic valve control. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention is directed to an arrangement for supplying current to the solenoid valves of an electro-hydraulic valve-timing system of an internal combustion engine in a controllable manner. BACKGROUND INFORMATION [0002] In known electrohydraulic valve-timing systems, solenoid valves are assigned to gas-exchange actuators. The solenoid valves are energized in order to control the flow of hydraulic oil to and from the gas-exchange actuator. In this context, it is known to provide a two-stage voltage supply for the solenoid valves. An inrush voltage is supplied by an inrush voltage source, and a holding voltage is supplied by a holding-voltage source, the inrush voltage being greater than the holding voltage. The actuation of the solenoid valve in response to the application of the inrush voltage leads to a rapid acceleration of the valve body. In this way, the valve's inertia is reduced. Following a free-running phase subsequent to the actuation by the inrush voltage, the solenoid valve is actuated by the holding voltage. The holding voltage is of sufficient magnitude to reliably bring the valve body into the end actuation position of the valve, and to hold it there. However, compared to the inrush voltage, the current consumption in the holding phase is lower. As a result, there is also less self-heating of the valve. The solenoid valves can be actuated independently of one another for the duration of an inrush current time by an inrush current that corresponds to the applied inrush voltage, and for the duration of a holding current time by a holding current that corresponds to the applied holding voltage. Thus, the duration of actuation of the solenoid valve is derived from the inrush current time, the time subsequent thereto for the free-running phase, and from the holding current time. In this context, the solenoid valve can be designed both as a normally-open as well as a normally-closed valve. If the solenoid valve is designed as a normally-open valve, then it interrupts a fluid path when energized, while a valve designed as a normally-closed valve clears a fluid path when actuated. In this context, one holding voltage line and one inrush voltage line are provided for each solenoid valve, the holding voltage line connecting the solenoid valve to the holding voltage source and the inrush voltage line connecting the solenoid valve to the inrush voltage source. Moreover, a ground lead leading from the solenoid valve to ground is provided, having one ground lead disconnector for switchably disconnecting the electrical connection between the solenoid valve and ground. [0003] In the above-described arrangement, besides the ground lead disconnector, for each solenoid valve, a changeover switch is also necessary to connect the solenoid valve alternatively to the inrush voltage line or to the holding voltage line. [0004] To actuate a gas-exchange valve, the solenoid valves assigned to this gas-exchange valve are driven. In the process, the controlled actuation of the changeover switch and of the ground lead disconnector is required to drive a solenoid valve. The electric power supply to the particular solenoid valve is switched via the ground lead disconnector, while the inrush voltage or the holding voltage is alternately applied to the solenoid valve via the changeover switch. [0005] A gas-exchange valve is typically controlled via two solenoid valves; one determines the supply of hydraulic fluid into a working chamber, and the other controls the discharge of the hydraulic fluid out of the working chamber. If an internal combustion engine has four gas-exchange valves (two intake valves and two exhaust valves) per cylinder, then eight solenoid valves and thus sixteen separately controllable switches are needed just to control one cylinder. An equivalent number of driving signals for actuating the solenoid valves must be generated time-synchronously to move the crankshaft. [0006] It is an object of the present invention to reduce the outlay required for circuitry and for control of solenoid valves. SUMMARY [0007] An arrangement for supplying current to the solenoid valves of an electrohydraulic valve-timing system of an internal combustion engine in a controllable manner has solenoid valves assigned to the gas-exchange actuators. A two-stage supplying of voltage is provided for the solenoid valves, namely the supplying of an inrush voltage from an inrush voltage source, and the supplying of a holding voltage from a holding voltage source. In this context, the inrush voltage is greater than the holding voltage. The solenoid valves may be actuated independently of one another for the duration of an inrush current time by an inrush current that corresponds to the applied inrush voltage, and for the duration of a holding-current time by a holding current that corresponds to the applied holding voltage. For each solenoid valve, one inrush voltage line and one holding voltage line are provided, which connect the solenoid valve to the inrush voltage source and to the holding voltage source, respectively. From each solenoid valve, a ground lead leads to ground, a ground lead disconnector being provided in the ground lead for switchably disconnecting the electrical connection between the solenoid valve and ground. [0008] In accordance with the present invention, a solenoid valve group is formed from a plurality of solenoid valves. Inrush voltage lines leading to the solenoid valves of a solenoid valve group have a common inrush-voltage circuit section, and a voltage disconnector is provided in the common inrush-voltage circuit section for establishing the switchable electrical connection between the inrush voltage source and the solenoid valves of the solenoid valve group. [0009] As a result of this arrangement, only one single switchable voltage disconnector needs to be provided for the solenoid valves of the solenoid valve group to establish the connection to the inrush voltage. This single voltage disconnector replaces the changeover switch that is provided for each valve. If the voltage disconnector is switched through, then the inrush voltage is applied to all solenoid valves of the solenoid valve group. The actual energizing of the solenoid valve with the inrush current derived from the inrush voltage is accomplished by the actuation of the individual ground lead disconnectors assigned to the solenoid valves. A solenoid valve is energized with inrush current when the voltage disconnector of the corresponding solenoid valve group is closed and, at the same time, when the corresponding ground lead disconnector of the solenoid valve is likewise closed. Due to the existence of the ground lead disconnector, the solenoid valves within the solenoid valve group continue to be individually controllable. [0010] Thus, the present invention makes it possible to reduce the number of required switches. Along with the reduction in the number of switches, the outlay for controlling the switches is also correspondingly reduced. Due to the presence of a common inrush-voltage circuit section, the outlay for circuit wiring is also reduced. [0011] In accordance with one example embodiment of the present invention, the holding-voltage line is designed to permanently supply the solenoid valves of at least one solenoid valve group with holding voltage. In this context, the holding voltage lines leading to the solenoid valves have a common holding voltage section. This measure reduces the outlay for circuit wiring. [0012] In accordance with another example embodiment, the voltage disconnector of a solenoid valve group connects the common inrush voltage section to the common holding voltage section of this solenoid valve group at a contact point. In this context, a blocking diode is provided in the common holding voltage section between the holding voltage source and the junction point. It blocks the current flow from the junction point to the holding voltage point. A common line for supplying the corresponding solenoid valve with inrush voltage and with holding voltage leads from the junction point to the solenoid valves of the solenoid valve group. This measure further reduces the outlay for circuit wiring. The inrush voltage and holding voltage may be supplied, in part, over the same line. If the voltage disconnector of a solenoid valve group is interrupted, then the holding voltage is applied to the solenoid valves. If the voltage disconnector is closed, then the inrush voltage is applied to the solenoid valves. The diode between the holding voltage source and the junction point source prevents current from flowing from the inrush voltage source to the holding voltage source and, thus, an undesired shunting. This measure as well reduces the outlay required for cabling or circuit wiring. [0013] The solenoid valves of a solenoid valve group are energized by the inrush current derived from the inrush voltage when the voltage disconnector is closed and, at the same time, when the ground lead disconnector assigned to the individual valve is likewise closed. A solenoid valve is actuated by the holding current derived from the holding voltage when the voltage disconnector of the solenoid valve group is disconnected and the ground lead disconnector assigned to the corresponding solenoid valve is closed. [0014] In accordance with one example embodiment of the present invention, the solenoid valves of a solenoid valve group are selected in such a way that the inrush-voltage actuation times do not overlap with the holding-voltage actuation times. This measure ensures that when it is necessary to supply one solenoid valve of the solenoid valve group with inrush voltage, that it is not necessary to supply another valve with holding voltage. Alternatively, either the inrush voltage or the holding voltage is applied to the voltage supply side of the solenoid valves. If there is no overlapping of the holding current times and the inrush current times, then the voltage disconnector may be suitably actuated to effect that the voltage level required at the particular instant is applied to the voltage side of the solenoid valves. [0015] In a classic valve-timing mechanism, the opening angular ranges of the gas-exchange valves over the crankshaft angle are, at a maximum, 240.degree. crankshaft angle. This considers both the opening times of the intake valves as well as of the exhaust valves. Accordingly, at a maximum, this is proportionally 33% of an engine's working cycle of over 720.degree. crankshaft angle, so that it is easily possible to combine a plurality of solenoid valves into one solenoid valve group, without the occurrence of any corresponding overlapping. [0016] In accordance with one example embodiment of the present invention, the ground lead disconnector of the solenoid valves is switchable in a clocked cycle. In this context, the make-to-break ratio is devised in such a way that when inrush voltage is supplied, the average current flow resulting from the clocked operation corresponds to the holding current derived from the holding voltage. Thus, by the timed switching of the ground lead disconnector, power may also be supplied using a current corresponding to the holding current when the inrush voltage is applied on the voltage-supply side. This measure is particularly advantageous when, within solenoid valves assigned to one solenoid valve group, an overlapping results between inrush-voltage actuation times and holding-voltage actuation times. However, it may also be utilized to reduce the number of switching operations of the voltage disconnector and to partially allow the inrush voltage to be applied on the voltage supply side even when it would actually suffice for just holding voltage to be supplied. In accordance with another example embodiment of the present invention, on the ground connection side, each solenoid valve has a feedback line which connects the ground connection of the solenoid valve to the inrush voltage source. In this context, a diode is connected in the feedback line. It blocks a current flow from the inrush voltage source to the ground connection of the solenoid valve. [0017] The advantage of this example embodiment of the present invention is that the currents flowing in the coil of a solenoid valve are able to be quickly reduced once the ground lead disconnector is opened. Simply stated, current is fed back via the feedback line to the inrush-voltage source. The diode situated in the feedback line prevents current from flowing from the inrush voltage source via the feedback line to the solenoid valve and, from there, to the holding voltage source. If a solenoid valve is actuated by an inrush current because the voltage disconnector was closed, then, in response to opening of the ground lead disconnector, the decaying coil current may flow back to the inrush voltage source. In between applications of in-rush current and holding current to the solenoid valve, the so-called free-wheeling or free-running phase is generated. In this free-running phase, the ground lead disconnector of the corresponding solenoid valve is opened. Similarly, a rapid extinguishing of current results, so that the solenoid valve is quickly moved back at the end of the holding phase predefined by the holding current time. If, in response to the application of holding voltage, the ground lead disconnector of a solenoid valve is opened, the still present coil current may only be fed back via the feedback line to the voltage source, which is at a higher potential than the holding voltage source. The result is a rapid decay of the coil current. [0018] In accordance with one example embodiment of the present invention, first and second solenoid valves are provided, the first solenoid valves being closed in a de-energized state, and the second solenoid valves being opened in a de-energized state. As an example, each gas-exchange actuator has a first and a second solenoid valve. Each cylinder of the internal combustion engine has, e.g., at least one intake valve and at least one exhaust valve, each of the intake and exhaust valves being able to be actuated by a gas-exchange actuator. A complete electrohydraulic valve actuation is accomplished by this arrangement. [0019] In accordance with one example embodiment of the present invention, all solenoid valves of the gas-exchange actuators assigned to one cylinder of the internal combustion engine are combined into one solenoid valve group. [0020] By combining into one solenoid valve group, all solenoid valves which are assigned to one cylinder because of their allocation to the gas-exchange actuators form a solenoid valve group for which it is ensured that the time periods during which the solenoid valves are actuated by inrush voltage do not overlap with those periods during which they are actuated by holding voltage. [0021] Given a reduced number of control elements and a reduced outlay for actuation, such an arrangement renders possible a valve control that is free of overlap times, even in the context of internal combustion engines having a large number of cylinders. Continue reading about Arrays for controllable power supply of electrovalves of an electrohydraulic valve control... 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