JP2008095657A - Valve drive system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve drive system allowing high-accuracy acquisition of correspondence relation between a rotation position of an electric motor and a rotation position of a cam. <P>SOLUTION: This valve drive system has: a motive power transmission mechanism 10A converting rotary motion of the electric motor 8A into opening/closing motion of an intake valve 3 provided in a cylinder 2 of an internal combustion engine 1 through the cam 9A and transmitting it; a mechanism part 21A provided in a motion transmission route from the electric motor 8A to the intake valve 3, capable of restricting rotation of the cam 9A by blocking the rotary motion of the cam 9A in a prescribed position; and a rotation position detection sensor 37 detecting the rotation position of the electric motor 8A. The rotation position of the electric motor 8A is acquired from the rotation position detection sensor 37 in a state that the rotary motion of the cam 9A is blocked in the mechanism part 21A, and the correspondence relation between the rotation position of the electric motor 8A and the rotation position of the cam 9A is stored on the basis of the rotation position of the electric motor 8A acquired in the state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention converts a rotational movement of an electric motor into an opening / closing movement of a valve provided in a cylinder of an internal combustion engine via a cam and transmits the valve, and stores a correspondence relationship between the rotational position of the electric motor and the rotational position of the cam. It relates to the drive system.

  As such a valve drive system, the electric motor torque required for the rotation of the cam shaft is detected with the electric motor rotating at a constant speed, and the rotation position of the electric motor and the rotation position of the cam are determined based on the torque change. One that executes an initialization process for storing the correspondence relationship is known (Patent Document 1). This system uses the relationship in which the rotational position of the cam is the position that gives the maximum lift amount to the valve when the torque of the electric motor reaches the maximum value in the initialization process.

JP 2004-183612 A

  However, even if the rotational speed of the electric motor is the same, the torque changes due to various factors such as a change in viscosity accompanying a change in temperature of the lubricating oil that lubricates the cam and a deterioration of the lubricating oil. For this reason, if the correspondence relationship between the rotational position of the electric motor and the rotational position of the cam is grasped based on the change in the torque of the electric motor, the relationship between the actual correspondence relationship is affected by the influence of the above-mentioned factors. Deviation may occur.

  Accordingly, an object of the present invention is to provide a valve drive system that can accurately grasp the correspondence between the rotational position of the electric motor and the rotational position of the cam.

  A valve drive system according to the present invention includes a power transmission mechanism that converts rotational movement of an electric motor into an opening / closing movement of a valve provided in a cylinder of an internal combustion engine via a cam, and a movement from the electric motor to the valve. A rotation angle limiting mechanism provided in the transmission path and capable of limiting the rotation of the cam to a predetermined angle range by preventing the rotational movement of the cam; and a motor rotation position detecting means for detecting the rotation position of the electric motor; The rotational position of the electric motor is acquired from the motor rotational position detecting means in a state where the rotational movement of the cam is blocked by the rotational angle limiting mechanism, and based on the rotational position of the electric motor acquired in the state The above-described problem is solved by providing position learning means for storing a correspondence relationship between the rotational position of the electric motor and the rotational position of the cam.

  According to this valve drive system, since the rotational position of the cam when the rotational movement of the cam is blocked is preset, the electric motor is based on the rotational position of the electric motor when the rotational movement of the cam is blocked. Can be associated with the rotational position of the cam. Since this correspondence is irrelevant to the change in torque of the electric motor, the influence of various factors that cause the change in torque is eliminated, and deviation from the actual correspondence can be reduced.

  As long as the rotation angle limiting mechanism can mechanically limit the rotation of the cam, the configuration is not particularly limited. For example, the rotation angle limiting mechanism includes a rotation restricting portion provided on the rotating member so as to be located radially outside the rotation center of the rotating member provided on the motion transmission path, and the rotation restricting portion. You may provide the movable member which can move between the restriction | limiting position which interferes in a passage range, and the non-restriction position away from the said passage range (Claim 2). According to this aspect, when the movable member moves from the non-restricted position to the restricted position, the movable member can interfere with the passage range of the rotation restricting portion and prevent the rotation member from freely rotating. Thereby, since transmission of the rotational motion of the electric motor by the power transmission mechanism is restricted in the motion transmission path, the rotation angle of the cam can be restricted.

  It is sufficient that the rotating member is provided in the motion transmission path. For example, when a transmission mechanism such as a gear train is provided between the electric motor and the cam shaft provided with the cam, a gear constituting the gear train may be provided as a rotating member. Moreover, you may make it provide the rotation member as another component in the gear shaft which rotates integrally with the gear. Furthermore, the rotating member may be provided so as to be integrally rotatable with the cam. In this case, since there is no play such as backlash or clearance between the cam and the rotating member, the rotation of the cam can be accurately restricted without considering such play. Thereby, the correspondence between the rotational position of the electric motor and the rotational position of the cam can be obtained with high accuracy.

  The rotation restricting portion provided in the rotating member may be in any form as long as the rotational movement of the cam can be prevented at a predetermined position, and the number thereof is not limited. Therefore, you may provide a some rotation control part in a rotation member. In this case, the rotation restricting portion may be provided with a plurality of rotation restricting portions arranged as different from each other in the range in which the rotation of the cam can be restricted as the rotation restricting portion. Good (Claim 4). In this case, since a plurality of rotation restricting portions are arranged on the same circumference, only one movable member is moved forward and backward with respect to the rotating member in order to restrict the rotation of the cam using each rotation restricting portion. It ’s enough. In addition, since the range in which the rotation of the cam can be restricted is different for each rotation restricting portion, it is possible to determine which rotation restricting portion restricts the rotation of the cam by checking the range in which the cam is restricted. Is possible.

  In order to realize such discrimination, in one aspect of the valve drive system of the present invention, when the movable member moves to the restriction position and the rotational movement of the cam is prevented, the rotational movement of the cam is blocked. Motor control means for controlling the electric motor so that the cam is reversed from the state where the cam is reversed, and from the state where the rotational movement of the cam is blocked until the cam is reversed and the rotational movement of the cam is blocked Limit angle acquisition means for acquiring a rotation angle may be further provided. In this case, a range in which the rotation of the cam is restricted by the rotation restricting portion is obtained by reversing the cam from the state in which the rotational movement of the cam is prevented and obtaining the rotational angle until the next rotational movement of the cam is prevented. Becomes clear. Therefore, based on the range, it is possible to determine which rotation restricting portion restricts the rotation of the cam.

  In the aspect in which the movable member interferes with the rotation restricting portion, the movable member interferes with the rotation restricting portion to forcibly prevent the rotational movement of the cam. Therefore, when this interference is repeated, the rotation restricting portion and the movable member are Each of these may be mechanically worn and cause an error in the regulation range. Therefore, in one aspect of the valve drive system of the present invention, when the movable member moves to the limit position and the rotational movement of the cam is blocked, the cam is moved from the state where the rotational movement of the cam is blocked. Motor control means for controlling the electric motor so as to be reversed; and a rotation angle of the cam from the state where the rotational movement of the cam is prevented until the cam is reversed and then the rotational movement of the cam is prevented And calculating the difference between the rotation angle acquired by the limit angle acquiring unit and the predetermined angle range, and correcting the correspondence stored in the position learning unit based on the calculation result And a correction means for performing the correction (claim 6). According to this aspect, since the correspondence is corrected in consideration of the wear generated in the rotation restricting portion and the movable member, the deviation from the actual correspondence caused by the wear can be reduced.

  The predetermined angle range that can be limited by the rotation angle limiting mechanism may be set as appropriate. For example, the predetermined angle range may be set to a range narrower than the range in which the maximum lift amount of the valve can be obtained, or further set to a range where the piston and valve of the internal combustion engine do not interfere with each other, that is, a range where no valve stamp is generated. May be. When the predetermined angle range is set to a range where no valve stamp is generated, the rotation of the cam is limited to the predetermined angle range when the rotation of the crankshaft of the internal combustion engine and the rotation of the cam are asynchronous. Further, a fail safe means for controlling the rotation angle limiting mechanism may be further provided (Claim 7). According to this aspect, when the rotation of the crankshaft of the internal combustion engine and the rotation of the cam are asynchronous, the rotation of the cam is limited by the rotation angle limiting mechanism. Under the limitation, the rotation of the cam does not exceed a predetermined angle range set so that the piston and the valve do not interfere with each other, so that the valve stamp can be reliably prevented.

  As described above, according to the valve drive system of the present invention, since the rotational position of the cam when the rotational movement of the cam is blocked is preset, the electric motor when the rotational movement of the cam is blocked is set. The rotational position of the electric motor and the rotational position of the cam can be associated with each other based on the rotational position. Since this correspondence is irrelevant to the change in torque of the electric motor, the influence of various factors that cause the change in torque is eliminated, and the deviation from the actual correspondence can be reduced.

(First form)
FIG. 1 schematically shows a main part of an internal combustion engine to which the valve drive system according to the first embodiment of the present invention is applied, and FIG. 2 shows the internal combustion engine of FIG. 1 as viewed from the direction of arrows II-II in FIG. The state is shown. The internal combustion engine 1 is mounted on a vehicle as a driving power source, and is an in-line four-cylinder internal combustion engine in which four cylinders 2 are arranged in a row. Each of the four cylinders 2 (only two are shown in FIG. 6) is provided with two intake valves 3 (not shown) and two exhaust valves (not shown) as valves according to the present invention. The intake valve 3 is provided so that the stem 3a can be reciprocated in the axial direction of the stem 3a by passing the stem 3a through a stem guide of a cylinder head (not shown). The intake valve 3 is urged in a direction in which the valve face is in close contact with the valve seat of the intake port by a compression reaction force of a valve spring (not shown). Each cylinder 2 is provided with a piston 6 connected to a crankshaft 5 via a connecting rod 4 so as to be able to reciprocate.

  The internal combustion engine 1 is provided with a first variable valve mechanism 7A and a second variable valve mechanism 7B for opening and closing the intake valve 3. One variable valve mechanism 7A is responsible for opening and closing the intake valves 3 of the outer two cylinders, ie, the first and fourth cylinders 2, and the other variable valve mechanism 7B is the inner two cylinders, ie, the second and third cylinders. Responsible for opening and closing the third cylinder 3. In FIG. 1, illustration of the third and fourth cylinders 2 is omitted. The variable valve mechanism 7A includes an electric motor 8A and a power transmission mechanism 10A that converts the rotational movement of the electric motor 8A into an opening / closing movement of the intake valve 3 and transmits the rotation movement via a cam 9A described later. Similarly, the variable valve mechanism 7B includes an electric motor 8B and a power transmission mechanism 10B that converts the rotational movement of the electric motor 8B into an opening / closing movement of the intake valve 3 through a cam 9B, which will be described later. A valve lifter 11 is interposed between each cam 9A, 9B and each intake valve 3.

  The first electric motor 8A and the second electric motor 8B have the same configuration, and for example, a DC brushless motor capable of controlling the rotation speed is used. Each of the electric motors 8A and 8B incorporates a rotational position detection sensor 37 such as a resolver or a rotary encoder as a motor rotational position detecting means for detecting the rotational position.

  The power transmission mechanism 10A includes a gear train 12A and a cam mechanism 13A. The gear train 12A has a motor gear 14A that rotates integrally with the output shaft of the electric motor 8A, and a cam drive gear 15A that meshes with the motor gear 14A. The cam mechanism 13A includes a cam shaft 16A that is coaxially and integrally rotatable with the cam drive gear 15A. The cam shaft 16A opens and closes the intake valves 3 of the first and fourth cylinders 2. A cam 9A is provided so as to be integrally rotatable. As shown in FIG. 2, the cam 9A on the first cylinder side indicated by the solid line and the cam 9A on the fourth cylinder side indicated by the broken line are cams so that the apexes of the nose are shifted from each other by 180 ° in the circumferential direction. Each of the shafts 16A is provided. Therefore, the opening timings of the intake valve 3 of the first cylinder 2 and the intake valve 3 of the fourth cylinder 2 do not overlap each other. The gear train 12A is configured such that the reduction ratio between the electric motor 8A and the cam 9A is 2: 1.

  On the other hand, as shown in FIG. 1, the power transmission mechanism 10B is also provided with a gear train 12B and a cam mechanism 13B, similarly to the power transmission mechanism 10A. The gear train 12B has the same configuration as the gear train 12A of the power transmission mechanism 10A except that the intermediate gear 16 is interposed between the motor gear 14B and the cam drive gear 15B. The cam mechanism 13B is provided with a hollow shaft-like cam shaft 16B that is coaxially and integrally rotatable with the cam drive gear 15B and is coaxially combined with the outer periphery of the cam shaft 16A of the power transmission mechanism 10A. The cam shaft 16B is provided with a cam 9B for opening and closing the intake valves 3 of the second and third cylinders 2 so as to be integrally rotatable. Although not shown, the cam 9B on the second cylinder side and the cam 9B on the third cylinder side have a camshaft 16B so that the apexes of the nose are shifted from each other by 180 ° in the circumferential direction as in the case of the cam 9A. The opening timings of the intake valve 3 of the second cylinder 2 and the intake valve 3 of the third cylinder 2 do not overlap each other. The gear train 12B is configured such that the reduction ratio between the electric motor 8B and the cam 9B is 2: 1.

  The internal combustion engine 1 is provided with a rotation angle limiting unit 20 as means for limiting the rotation of each of the cam 9A and the cam 9B. In the rotation angle limiting unit 20, a first mechanism portion 21A as a rotation angle limiting mechanism for limiting the rotation of the cam 9A and a second mechanism portion 21B as a rotation angle limiting mechanism for limiting the rotation of the cam 9B are integrated. It has become. The mechanism portion 21A includes a disc-shaped flange 22A as a rotating member provided so as to be rotatable integrally with the cam shaft 16A, and a stopper pin 23A as a movable member that moves forward and backward with respect to the flange 22A. Similarly, the mechanism portion 21B includes a flange 22B as a rotating member provided so as to be rotatable integrally with the cam shaft 16B, and a stopper pin 23B as a movable member that moves forward and backward with respect to the flange 22B.

  As shown in FIG. 2, the flange 22A is provided with two groove-like long holes 24A and 25A as rotation restricting portions. Each of the groove-like long holes 24A, 25A is formed in an arc shape so as to extend in the circumferential direction of the flange 22A, and has a size capable of inserting the stopper pin 23A. In addition, although the dimension regarding the circumferential direction of two groove-shaped long holes 24A and 25A is mutually different, detailed description is mentioned later. On the other hand, the flange 22B is also provided with two groove-like long holes 24B and 25B similar to the flange 22A, and each groove-like long hole 24B and 25B has a size into which the stopper pin 23B can be inserted, and The dimensions in the circumferential direction are different from each other.

  These stopper pins 23A and 23B are driven between a restricting position shown in FIG. 1 and an unrestricted position shown in FIG. 3 by a hydraulic mechanism 26 using hydraulic pressure. 1, the stopper pin 23A is inserted into one of the slotted long holes 24A and 25A, and the stopper pin 23B is inserted into one of the slotted elongated holes 24B and 25B. Interferes with the passing range of any one of the slotted long holes 24B and 25B, and the stopper pin 23B interferes with the passing range of any of the slotted elongated holes 24B and 25B. Thereby, the rotation of the cams 9A and 9B is limited. On the other hand, at the non-restricted position, the stopper pin 23A is separated from the passing range of either of the slotted long holes 24A, 25A, and the stopper pin 23B is separated from the passing range of the slotted elongated holes 24B, 25B. Thereby, the restriction | limiting of rotation of cam 9A, 9B is cancelled | released.

  The hydraulic mechanism 26 is supplied with hydraulic pressure generated by an oil pump (not shown) using the internal combustion engine 1 as a drive source, that is, hydraulic pressure generated as the internal combustion engine 1 is operated. The hydraulic mechanism 26 includes a housing 27 in which a hydraulic chamber 27a in which the stopper pin 23A is accommodated and a hydraulic chamber 27b in which the stopper pin 23B is accommodated, a supply passage 28 communicating with each of the hydraulic chambers 27a and 27b, and each hydraulic chamber 27a. , 27b, and an electromagnetic valve 29 provided in the supply passage 28 as means for switching between supply of hydraulic pressure and switching off of the hydraulic pressure. The stopper pin 23A has a bowl-shaped piston portion 30A that slides in the hydraulic chamber 27a. The stopper pin 23A is attached to the limit position side by a compression reaction force of a spring 31 as an urging means provided in the hydraulic chamber 27a. It is energized. On the other hand, the stopper pin 23B also has a bowl-shaped piston portion 30B that slides in the hydraulic chamber 27b, and is limited by the compression reaction force of the spring 31 as an urging means provided in the hydraulic chamber 27b. It is biased to the position side. Thus, when the supply passage 28 is opened by the electromagnetic valve 29, the hydraulic pressure is guided to the hydraulic chambers 27a and 27b, respectively. These hydraulic pressures act on the piston portion 30A of the stopper pin 23A and the piston portion 30B of the stopper pin 23B, so that each stopper pin 23A, 23B resists the reaction force of the spring 31 from the restricted position to the unrestricted position. Moving. On the other hand, when the supply passage 28 is closed by the electromagnetic valve 29, the supply of hydraulic pressure is cut off, so that the stopper pins 23A and 23B are moved from the non-restricted position to the restricted position by the compression reaction force of the spring 31.

  FIG. 4 is an enlarged view of the flange 22A and the cam 9A shown in FIG. 2, and the cam 9A provided on the first cylinder side is indicated by a solid line, and the cam 9A provided on the fourth cylinder side is indicated by a broken line. . In addition, since the flange 22B is the same as the flange 22A, description is abbreviate | omitted by substituting FIG. As shown in FIG. 4, the two groove-like long holes 24 </ b> A and 25 </ b> A have different dimensions in the circumferential direction. In other words, the two slotted long holes 24A and 25A limit the rotation of the cam 9A when the stopper pin 23A is inserted into the slotted elongated hole 24A and when the stopper pin 23A is inserted into the slotted elongated hole 25A. The range of possible angles is configured to be different. In other words, the two groove-like long holes 24A and 25A have different central angles β1 and β2 connecting the circumferential ends and the rotation center C of the flange 22A. In the illustrated form, the central angle β1 of the groove-like long hole 24A is configured to be smaller than the central angle β2 of the groove-like long hole 25A. Further, when the flange 22A rotates in the direction of the arrow in FIG. 4 (clockwise), the ends P1, P2 of the slotted holes 24A, 25A against which the stopper pin 23A is abutted are on a straight line L passing through the rotation center C of the flange 22A. Are lined up. As described above, since the cam 9A provided on the first cylinder side and the cam 9A provided on the fourth cylinder side are 180 ° out of phase with each other, the cam provided on the first cylinder side. The central angle α connecting the apex Q1 of the nose 9A and the end P1 of the slotted slot 24A with the rotation center C is the apex Q2 of the nose of the cam 9A provided on the fourth cylinder side and the slotted slot 25A. It becomes equal to the central angle α connecting the one end P2 with the rotation center C.

  The valve drive system of the present embodiment uses the rotation angle limiting unit 20 having the above configuration, and the relationship between the rotation position of the cam 9A and the rotation position of the electric motor 8A, the rotation position of the cam 9B, and the rotation of the electric motor 8B. Each of the relations with the position is grasped so that these relations are properly maintained. As is apparent from FIG. 4, when the stopper pin 23A moves from the non-restricted position to the restricted position while the cam 9A is rotating, the cam 9A rotates when the stopper pin 23A is at one end P1 of the slot-like elongated holes 24A and 25A. , P2 is blocked by hitting any one of them. The position where the stopper pin 23A hits one of the ends P1, P2 of the slot-like long holes 24A, 25A corresponds to the predetermined position of the present invention. If one of the ends P1 and P2 of the slotted long holes 24A and 25A can prevent the rotational movement of the cam 9A from being specified, the angle α from the ends P1 and P2 to the apex of the nose of the cam 9A is a predetermined value. The rotational position of 9A can be specified. At this time, if the rotational position of the electric motor 8A in a state where the rotational motion is blocked is acquired from the rotational position detection sensor 37, the correspondence between the rotational position of the electric motor 8A and the rotational position of the cam 9A can be grasped. Further, the correspondence between the rotational position of the electric motor 8B and the rotational position of the cam 9B can be grasped with the same concept.

  As shown in FIG. 1, the valve drive system according to the present embodiment controls the operation of the electric motors 8A and 8B and, based on the above concept, the correspondence between the rotational position of the electric motor 8A and the rotational position of the cam 9A. An engine control unit (ECU) 35 is provided to grasp the relationship and the correspondence between the rotational position of the electric motor 8B and the rotational position of the cam 9B. The ECU 35 is configured as a computer having a microprocessor and a RAM and a ROM as its main storage device. In addition to controlling the electric motors 8A and 8B and grasping the correspondence relationship, various parameters such as fuel injection amount and ignition timing are provided. Is controlled based on a predetermined logic. The ECU 35 has a crank angle sensor 36 that outputs a signal corresponding to the rotational position of the crankshaft 5, a throttle opening sensor, and an air flow meter (both are not available) as input means for information necessary for controlling the electric motors 8 A and 8 B. Various sensors such as those shown in FIG. Further, the ECU 35 also receives an output signal of the rotational position detection sensor 37 built in each electric motor 8A, 8B.

  Next, control by the ECU 35 will be described. In the following, control related to the first and fourth cylinders 2 will be described, but the same applies to control related to the second and third cylinders 2. FIG. 5 shows an example of a control routine of cam position learning control that the ECU 35 repeatedly executes at predetermined intervals in order to grasp the correspondence between the rotational position of the electric motor 8A and the rotational position of the cam 9A. By executing this control routine, the ECU 35 functions as position learning means according to the present invention.

  In this control routine, the ECU 35 first determines whether or not a learning start condition is satisfied in step S1. The learning start condition is appropriately set in consideration of the necessity of position learning. For example, this start condition may be satisfied when the internal combustion engine 1 is started or when the integrated value of the operation time of the internal combustion engine 1 exceeds a threshold value. If it is determined that the learning start condition is satisfied, the process proceeds to step S2, and if not, the process waits. In step S2, the operation of the electric motor 8A is controlled so that the cam 9A (cam shaft 16A) starts to rotate in one direction. Next, in step S3, the solenoid valve 29 is controlled so that the stopper pin 23A can be switched from the non-restricted position to the restricted position. As a result, the stopper pin 23A is inserted into one of the groove-like long holes 24A and 25A of the flange 22A. Next, in step S4, it is determined whether or not the rotational movement of the cam 9A is blocked, that is, whether or not the operation of the cam 9A is restricted by hitting one end P1 or P2 of the slotted long holes 24A or 25A. To do. This determination may be made as appropriate. For example, the supply current to the electric motor 9A, which is a physical quantity that correlates with the torque fluctuation of the electric motor 9A, may be monitored, and it may be determined that the rotational motion is prevented when the current value exceeds a predetermined determination value. Further, the rotational position detection sensor 37 built in the electric motor 9A stops its output signal when the rotational movement is blocked. Therefore, the rotational position detection sensor 37 determines whether or not the rotational movement is blocked based on the change of the signal. You can also.

  When the rotational motion is blocked, the process proceeds to step S5, and the rotational position θ of the electric motor 9A at the time when the rotational motion is blocked is stored in the RAM of the ECU 35. The rotation position θ is defined by a rotation angle from a predetermined rotation origin of the electric motor 9A, and is acquired based on a signal from the rotation position detection sensor 37. Next, in step S6, the rotational position θn of the electric motor with respect to the nose apex position of the cam 9A is calculated. The rotational movement of the cam 9A is prevented by the stopper pin 23A hitting any one of the slot-like long holes 24A and 25A, but it cannot be determined at this time which of the stopper pins 23A has been inserted. Therefore, with respect to the cam 9A on the first cylinder side, the rotational position θn of the electric motor 8A relative to the nose apex position of the cam 9A is determined in consideration of the reduction ratio between the electric motor 8A and the cam 9A. -2α or θ-2 (α + 180 °) (see FIG. 4). Therefore, by performing the processing of steps S7 to S12, it is determined in which elongated hole the stopper pin 23A has been inserted to prevent the rotational movement of the cam 9A, and the rotational position θn is determined based on the determination result. ing.

  In step S7, the electric motor 8A is controlled so that the cam 9A is reversed from the state where the rotational movement of the cam 9A is blocked. At this time, since the stopper pin 23A remains switched to the limit position, when the cam 9A rotates in the opposite direction, the stopper pin 23A is moved to the other end P'1, P'2 on the opposite side of the slot-like long holes 24A, 25A. (See FIG. 4), the rotational movement of the cam 9A in the opposite direction is prevented. By executing step S7, the ECU 35 functions as motor control means according to the present invention. Whether or not the rotational motion is blocked is determined by the same method as in step S4. If the rotational motion is blocked, the process proceeds to step S9. In step S9, the rotation angle β of the cam 9A from the state in which the rotational movement in one direction of the cam 9A is blocked to the rotation in the opposite direction of the cam 9A is acquired. As the rotation angle β, the rotational position θ ′ of the electric motor 8A when the rotational movement in the opposite direction is prevented is acquired based on the signal from the rotational position detection sensor 37, and stored in step S5 from this rotational position θ ′. Is obtained by subtracting the rotational position θ and multiplying by 1/2. That is, the rotation angle β is β = (θ′−θ) / 2. By executing step S9, the ECU 35 functions as a limit angle acquisition unit according to the present invention.

  Next, in step S10, it is determined whether or not the rotation angle β is equal to the central angle β1 of the groove-like long hole 24A. When β = β1, the stopper pin 23A is inserted into the groove-like long hole 24A, and the rotational movement of the cam 9A is prevented. Therefore, the process proceeds to step S11, where the rotational position θn of the electric motor 8A with respect to the nose apex position of the cam 9A provided on the first cylinder side is determined as θ-2α and provided on the fourth cylinder side. The rotational position θn of the electric motor 8A with respect to the apex position of the nose of the cam 9A is determined as θ-2 (α + 180 °). On the other hand, when β ≠ β1, the stopper pin 23A is inserted into the groove-like elongated hole 25A, and the rotational movement of the cam 9A is prevented. Therefore, the process proceeds to step S12, and the rotational position θn is determined contrary to the case of step S11. That is, the rotational position θn of the electric motor 8A relative to the nose apex position of the cam 9A provided on the first cylinder side is determined as θ-2 (α + 180 °), and the cam 9A provided on the fourth cylinder side. The rotational position θn of the electric motor 8A with respect to the nose apex position is determined as θ-2α.

  Next, in step S13, the determined rotational position θn is stored in the RAM of the ECU 35 as a correspondence relationship according to the present invention. In step S14, the electromagnetic valve 29 is controlled so that the stopper pin 23A can be switched from the restricted position to the unrestricted position, and the current routine is terminated.

  According to the routine of FIG. 5, since the rotational position of the cam 9A when the rotational movement of the cam 9A is blocked is preset, the rotational position θ of the electric motor 8A when the rotational movement of the cam 9A is blocked. The rotational position of the electric motor 8A and the rotational position of the cam are associated with each other. Since this correspondence relationship is irrelevant to the torque change of the electric motor 8A, the influence of various factors that cause the torque change is eliminated, and the deviation from the actual correspondence relationship can be reduced.

(Second form)
Next, the 2nd form of the valve drive system of this invention is demonstrated. In this embodiment, the size of each slot-shaped slot shown in FIG. 4, that is, the upper limits of the central angles β 1 and β 2 are set so that the piston 6 and the intake valve 3 do not interfere with each other. When the rotation and the rotation of the cams 9A and 9B are asynchronous, the rotation of the cams 9A and 9B is limited to prevent the valve stamp. Except for this feature, the second embodiment is the same as the first embodiment, and hence the description of the common parts with the first embodiment will be omitted.

  In order for the internal combustion engine 1 to operate normally, it is necessary to synchronize the rotation of the crankshaft 5 and the rotation of the camshafts 16A and 16B. The ECU 35 refers to the output signals of the crank angle sensor 36 provided on the crankshaft 5 and the output signals of the rotational position detection sensors 37 incorporated in the electric motors 8A and 8B. This is realized by controlling the operation. When a failure occurs in the internal combustion engine 1 due to some cause, these synchronizations may be lost. If any countermeasure is taken in an asynchronous state or if the operation of the internal combustion engine 1 is continued, a valve stamp may occur. Therefore, the ECU 35 executes the following fail-safe control for avoiding the valve stamp at the time of failure. By executing this control routine, the ECU 35 functions as fail-safe means according to the present invention.

  FIG. 6 is a flowchart showing an example of a control routine for fail-safe control. The program of this routine is held in advance by the ECU 35, and the ECU 35 reads it out appropriately and repeatedly executes it. First, in step S21, the ECU 35 detects the rotational position of the crankshaft 5 and the rotational positions of the camshafts 16A and 16B based on the output signals from the crank angle sensor 36 and the rotational position detection sensor 37, respectively. Next, in step S22, the ECU 35 checks whether or not the rotation of the crankshaft 5 and the rotation of the camshafts 16A and 16B are synchronized based on the detection result in step S21. As a result, when these are not synchronized, the process proceeds to step S23, and when the synchronization is confirmed, the process proceeds to step S26.

  In step S23, warning information such as a warning alarm is output in order to notify the driver that some abnormality has occurred in the internal combustion engine 1. Next, in step S24, the solenoid valve 29 is controlled so that the stopper pins 23A and 23B can be switched from the non-restricted position to the restricted position. In step S25, the electric motors 8A and 8B are controlled so that the operations of the cams 9A and 9B are stopped, and the current routine ends.

  On the other hand, in step S26, the solenoid valve 29 is controlled so that the stopper pins 23A and 23B can be switched from the restricted position to the non-restricted position, and this routine is finished. In addition, since step S28 is repeatedly performed at the normal time when the synchronization can be confirmed, the stopper pins 23A and 23B are held at the unrestricted positions.

  When the control of FIG. 6 is executed, when the crankshaft 5 and the camshafts 16A and 16B become asynchronous, the stopper pins 23A and 23B are switched to the limit positions. In this embodiment, since the size of each slot-shaped slot, that is, the upper limit of the central angles β1 and β2 shown in FIG. 4 is set so that the piston 6 and the intake valve 3 do not interfere with each other, the rotation angle limiting unit 20 The rotation angles of the cams 16A and 16B are physically limited to a range where the piston 6 and the intake valve 3 do not interfere with each other. Thereby, a valve stamp can be avoided reliably and reliability is improved.

(Third form)
Next, the 3rd form of the valve drive system of this invention is demonstrated. This form has the same configuration as the first form except that the contents of the cam position learning control are different. Hereinafter, differences will be described, and description of points common to the first embodiment will be omitted. FIG. 7 shows a control routine of the cam position learning control according to this embodiment. In this figure, the same processes as those in FIG. As described above, the operation for preventing the rotational movement of the cam 9A is such that the stopper pin 23A hits the groove-like long holes 24A, 25A and interferes therewith. Therefore, when this operation is repeated, the groove-like long holes 24A, The 25A and the stopper pin 23A are worn, and the central angles β1 and β2 of the groove-like long holes 24A and 25A may be larger than the design values. When the central angles β1 and β2 become larger than the design values, the angle α to the nose vertex Q1 of the cam 9A becomes smaller (see FIG. 4), and therefore an error occurs in the rotational position θn of the electric motor 8A with respect to the nose vertex position of the cam 9A. Will occur. Therefore, the ECU 35 executes the control routine shown in FIG. 7 to reduce the error.

  In FIG. 7, the ECU 35 executes steps S1 to S9 to obtain the rotation angle β. In the next step S30, it is determined whether or not the difference d between the rotation angle β and the center angle β1 is equal to or less than a predetermined value d1. judge. This predetermined value d1 is the difference between the central angle β1 and the central angle β2 (= | β1-β2 |) so that it can be determined in which elongated hole the stopper pin 23A has been inserted to prevent the rotational movement of the cam 9A. ) Is set to a smaller value. In step S30, when the difference d is equal to or smaller than the predetermined value d1, the stopper pin 23A is inserted into the slotted long hole 24A, and the rotational movement of the cam 9A is prevented. Therefore, the process proceeds to step S31, and the rotational position θn of the electric motor 8A with respect to the nose apex position of the cam 9A provided on the first cylinder side is calculated as θ-2α + d in consideration of the existence of the difference d. The rotational position θn of the electric motor 8A with respect to the nose apex position of the cam 9A provided on the fourth cylinder side is calculated as θ-2 (α + 180 °) + d. On the other hand, if the difference d exceeds the predetermined value d1 in step S30, the stopper pin 23A is inserted into the groove-like long hole 25A and the rotational movement of the cam 9A is prevented, so the process proceeds to step S32. In consideration of the existence of the difference d, the rotational position θn of the electric motor 8A relative to the nose apex position of the cam 9A provided on the first cylinder side is calculated as θ−2 (α + 180 °) + d and 4 The rotational position θn of the electric motor 8A with respect to the nose apex position of the cam 9A provided on the second cylinder side is calculated as θ-2α + d. As a result, the rotational position θn stored in step S13 is corrected by the ECU 35 so that the deviation from the actual value caused by the difference d is reduced. In this embodiment, by executing the control routine of FIG. 7, the ECU 35 performs position learning means according to the present invention, and by executing step S7 of FIG. 7, the ECU 35 functions as motor control means according to the present invention. By executing step S9, the ECU 35 functions as a limiting angle acquisition unit according to the present invention, and by executing steps S30 to S32 in the figure, the ECU 35 functions as a correction unit according to the present invention.

  The present invention is not limited to the above embodiments, and can be implemented in various forms within the scope of the gist of the present invention. The configuration of the rotation angle limiting mechanism is not limited to the above-described form. In the illustrated embodiment, the slot-like elongated hole as the rotation restricting portion is implemented as a concave portion, and the stopper pin as the movable member is implemented as a convex portion, and the concave portion and the convex portion engage with each other to prevent the rotation of the rotating member. However, it is easy to interchange the relationship between the concave and convex portions. That is, the side that prevents rotation may be a convex portion, and the side that prevents rotation may be a concave portion. Moreover, the form which makes a convex part and a convex part interfere may be sufficient. In addition to providing the rotating members on the cam shafts 16A and 16B, the cam shafts 16A and 16B themselves may be used as the rotating members. Further, in addition to the cam shaft, a member provided in a motion transmission path from the electric motor to the cam, such as an intermediate gear, may be used as the rotating member. In short, any mechanism that can physically limit the rotation angle of the cam shaft within a predetermined angle range may be used.

  8A and 8B correspond to a first modification of the form shown in FIG. 1, and FIG. 8A shows a state of the restricted position and FIG. 8B shows a state of the unrestricted position. In the following description, the same components as those in FIG. In this modification, a rotation angle limiting unit 120 including a hydraulic mechanism 126 that moves the stopper pins 23A and 23B in a direction perpendicular to the axis of the cam shafts 16A and 16B is provided. Curved grooves 124A and 124B as rotation restricting portions are formed on the outer peripheral surface of the cam shaft 16A and the outer peripheral surface of the cam shaft 16B, and each of the cam shafts 16A and 16B corresponds to a rotating member. The housing 127 is formed with a hydraulic chamber 127a in which the stopper pin 23A is accommodated and a hydraulic chamber 127b in which the stopper pin 23B is accommodated. Thereby, the function equivalent to the form of FIG. 1 can be exhibited, and especially the increase in the dimension of the rotation angle limiting unit 120 regarding the direction parallel to the axis of each cam shaft 9A, 9B can be suppressed.

  Further, the hydraulic mechanism of each embodiment described above is switched from the restricted position to the non-restricted position by supplying hydraulic pressure. On the contrary, as shown in FIG. 9, the hydraulic mechanism is switched from the non-restricted position to the restricted position by supplying hydraulic pressure. Is also possible. The form shown in FIG. 9 corresponds to a second modification of the form of FIG. 1, and the same components as those of the form of FIG. The hydraulic mechanism 226 is incorporated in the rotation angle limiting unit 220, and the spring 31 is urged against the stopper pins 23A and 23B in the reverse direction of the configuration shown in FIG. The stopper pins 23A and 23B are urged toward the non-restricted position by the spring 31. The hydraulic mechanism 226 includes a housing 227 in which a hydraulic chamber 227a in which the stopper pin 23A is accommodated and a hydraulic chamber 227b in which the stopper pin 23B is accommodated, and a supply passage 228 communicating with each of the hydraulic chambers 227a and 227b. The supply passage 228 is provided with the same solenoid valve 29 as that in FIG. 1 for guiding the hydraulic pressure generated in the internal combustion engine 1 and opening and closing the supply passage 228. Thus, when the supply passage 228 is opened by the electromagnetic valve 29, the hydraulic pressure is guided to the hydraulic chambers 227a and 227b, respectively. These hydraulic pressures act on the piston portion 30A of the stopper pin 23A and the piston portion 30B of the stopper pin 23B, so that each stopper pin 23A, 23B resists the reaction force of the spring 31 and is shown by a solid line in FIG. Move from the limit position to the limit position indicated by the broken line. On the other hand, when the supply passage 228 is closed by the electromagnetic valve 29, the supply of hydraulic pressure is interrupted, so that the stopper pins 23 </ b> A and 23 </ b> B are moved from the limit position to the non-limit position by the compression reaction force of the spring 31. The hydraulic mechanism 226 is suitable for application to an internal combustion engine having a high rotational speed at start-up, such as an internal combustion engine mounted on a so-called hybrid vehicle, or an internal combustion engine that frequently uses a high rotation / high load region.

  In each of the embodiments described above, the hydraulic mechanisms 26, 126, and 226 that use hydraulic pressure are provided as the movable member driving means. However, any mechanism may be used as long as the movable member can be moved. For example, a drive unit that can move the movable member between a restricted position and an unrestricted position using electromagnetic force may be used. An example of the drive means using such electromagnetic force is shown in FIG. The form of FIG. 10 corresponds to a third modification of the form of FIG. 1, and the same components as those of the form of FIG. This electromagnetic drive mechanism 50 is incorporated in the rotation angle limiting unit 320. Each stopper pin 23A, 23B is slidable and accommodated in a housing 327 in a state where it is urged by a spring 31 toward a limit position indicated by a solid line, and a solenoid 51 that generates a magnetic force by supplying current is provided in the housing 327. Is provided. When a current is supplied to the solenoid 51, the stopper pins 23A and 23B move from the restricted position to the unrestricted position indicated by the broken line against the compression reaction force of the spring 31. On the other hand, when the supply of current is stopped, the stopper pins 23A and 23B are moved from the non-restricted position to the restricted position by the compression reaction force of the spring 31. Thereby, by controlling the current supply to the solenoid 51, it can function in the same manner as the hydraulic mechanism described above. In addition, when using electromagnetic force, at least one part of each stopper pin 23A, 23B needs to be comprised with a magnetic body.

  In the form of FIG. 1 and its modification, the first mechanism portion 21A for limiting the rotation of the cam using the electric motor 8A as a drive source and the second mechanism for limiting the rotation of the cam using the electric motor 8B as a drive source. Although the rotation angle limiting units 20, 120, 220, and 320 that are integrated with the part 21B are provided, it is not essential to integrate these mechanism parts 21A and 21B, and these are provided separately and rotated. It may function as an angle limiting mechanism.

  In the above description, the variable valve mechanism for exclusively opening and closing the intake valve has been described. However, the above description also applies to the variable valve mechanism for the exhaust valve (not shown). Therefore, the rotation angle of the cam that drives the exhaust valve can be limited by applying the present invention. Further, by configuring the variable valve mechanism responsible for opening and closing the exhaust valve in the same manner as in the second embodiment, interference between the piston and the exhaust valve can be avoided.

The figure which showed typically the principal part of the internal combustion engine to which the valve drive system which concerns on the 1st form of this invention was applied. The figure which expanded and showed the state which looked at the internal combustion engine of FIG. 2 from the direction of arrow II-II of the figure. The figure which showed the state of the non-restricted position of the form of FIG. The figure which expanded and showed the flange and cam of FIG. The flowchart which showed an example of the control routine of the cam position learning control which concerns on a 1st form. The flowchart which shows an example of the control routine of the fail safe control which concerns on a 2nd form. The flowchart which showed an example of the control routine of the cam position learning control which concerns on a 3rd form. The figure which showed the principal part of the 1st modification of the form of FIG. 1, and showed the state of the restriction | limiting position. The figure which showed the principal part of the 1st modification of the form of FIG. 1, and showed the state of the non-restricted position. The figure which showed the principal part of the 2nd modification of the form of FIG. The figure which showed the principal part of the 3rd modification of the form of FIG.

Explanation of symbols

1 Internal combustion engine 2 Cylinder 3 Intake valve (valve)
8A, 8B Electric motors 9A, 9B Cams 10A, 10B Power transmission mechanism 21A First mechanism (rotation angle limiting mechanism)
21B Second mechanism (rotation angle limiting mechanism)
22A, 22B Flange (Rotating member)
23A, 23B Stopper pin (movable member)
24A, 24B, 25A, 25B Groove-shaped slot (rotation restricting part)
35 ECU (position learning means, motor control means, limit angle acquisition means, correction means, fail safe means)
37 Rotation position detection sensor (Motor rotation position detection means)

Claims (7)

  A power transmission mechanism that converts the rotational movement of the electric motor into a valve opening / closing movement provided in a cylinder of the internal combustion engine via a cam and transmits the movement, and a movement transmission path from the electric motor to the valve; A rotation angle limiting mechanism capable of limiting the rotation of the cam to a predetermined angle range by preventing the rotational movement of the motor at a predetermined position, motor rotation position detecting means for detecting the rotation position of the electric motor, and the rotation angle limitation The rotational position of the electric motor is acquired from the motor rotational position detection means in a state where the rotational movement of the cam is blocked by a mechanism, and the electric motor is controlled based on the rotational position of the electric motor acquired in the state. A valve drive system comprising: position learning means for storing a correspondence relationship between a rotational position and a rotational position of the cam.   The rotation angle limiting mechanism includes a rotation restricting portion provided in the rotating member so as to be positioned radially outward from a rotation center of the rotating member provided in the motion transmission path, and a passing range of the rotation restricting portion. The valve drive system according to claim 1, further comprising: a movable member that is movable between a restriction position that interferes with a non-restriction position that is distant from the passage range.   The valve driving system according to claim 2, wherein the rotating member is provided so as to be rotatable together with the cam.   The rotation member is provided with a plurality of rotation restricting portions arranged in a same circumference as the rotation restricting portions so that the ranges in which the rotation of the cam can be restricted are different from each other. The valve drive system according to claim 2 or 3.   Motor control means for controlling the electric motor so that the cam is reversed from a state in which the rotational movement of the cam is blocked when the movable member moves to the restriction position and the rotational movement of the cam is blocked; And a limit angle obtaining means for obtaining a rotation angle from a state where the rotational movement of the cam is prevented until the cam is reversed and then the rotational movement of the cam is prevented. Item 5. The valve drive system according to Item 4.   Motor control means for controlling the electric motor so that the cam is reversed from a state in which the rotational movement of the cam is blocked when the movable member moves to the restriction position and the rotational movement of the cam is blocked; A limit angle acquisition means for acquiring a rotation angle of the cam from the state in which the rotational movement of the cam is prevented until the cam is reversed and then the rotation movement of the cam is blocked; and the limit angle acquisition means And a correction unit that calculates a difference between the rotation angle acquired by the method and the predetermined angle range and corrects the correspondence stored in the position learning unit based on the calculation result. Item 5. The valve drive system according to any one of Items 2 to 4. The predetermined angle range is set to a range in which the piston of the internal combustion engine and the valve do not interfere with each other;
When the rotation of the crankshaft of the internal combustion engine and the rotation of the cam are asynchronous, it further comprises fail-safe means for controlling the rotation angle limiting mechanism so that the rotation of the cam is limited to the predetermined angle range. The valve drive system according to any one of claims 1 to 6, wherein

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