JP2018112092A - Variable valve gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable valve gear having a mechanism for switching between two types of cam lobes, while suppressing control dispersion when switching between the cam lobes.SOLUTION: The variable valve gear slides an outer cam in the axial direction of a cam shaft with a solenoid pin inserted into a switching groove for switching a driving cam lobe between two types of cam lobes to actually drive a valve. Besides, if the solenoid pin is not inserted into the switching groove, when switching the driving cam lobe, the variable valve gear applies a weak voltage lower than a voltage to be applied to a solenoid coil to the solenoid coil to calculate a resistance value for the solenoid coil, and controls a starting timing for applied voltage or voltage application to the solenoid coil at the time of switching the driving cam lobe, according to the resistance value for the solenoid coil.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a variable valve gear.

  2. Description of the Related Art Conventionally, there is known a variable valve operating device that switches a cam lobe that drives an intake valve or an exhaust valve of an internal combustion engine between two types of cam lobes having different cam profiles. Further, in such a variable valve operating device, there is known a device that controls the switching of the cam lobe by controlling the insertion of a solenoid pin into a switching groove formed in the outer cam. Furthermore, for example, Patent Document 1 discloses a variable valve operating apparatus in which the insertion timing of a solenoid pin is variable in accordance with engine operating conditions.

German Patent Application No. 102004027966 JP 2002-030950 A JP 2010-077921 A

  In the solenoid control for switching the cam lobe in the variable valve mechanism, the upper limit number of rotations at which the cam lobe can be switched can be expanded by accurately controlling the solenoid pin insertion operation. Further, by reducing variations in solenoid control, necessary specifications such as solenoid coil capacity can be reduced, and an effect of cost reduction can be expected.

  However, in order to achieve these, it is required to accurately control the target applied voltage value and energization timing, and for that purpose it is necessary to accurately grasp the protrusion time, which is the time required for inserting the solenoid pin. Become. Here, since the protruding time of the solenoid pin depends on the current applied to the solenoid, it is required to accurately grasp the resistance value of the solenoid.

  However, the resistance value of the solenoid varies depending on the coil temperature. The solenoid is generally mounted around the cylinder head of the engine, for example, on the head cover. For this reason, there are many disturbance factors that influence the coil temperature of the solenoid, such as the radiation temperature from the engine, the temperature of oil in the engine, the cooling according to the vehicle speed, and the temperature rise due to the dead soak. For this reason, the coil temperature and the resistance value of the solenoid vary greatly, and it is difficult to accurately grasp and control the protruding time of the solenoid pin.

  For example, when the coil temperature is estimated from the measured values such as the oil temperature and the outside air temperature indicating the surrounding conditions, the difference between the actual coil temperature and the estimated temperature becomes large. For this reason, control variation may occur in the solenoid control based on the energization timing calculated from the estimated coil temperature and the applied voltage.

  The present invention has been made in view of the above-described problems. That is, in a variable valve operating apparatus having a mechanism for switching between two types of cam lobes, an object is to suppress control variations during cam lobe switching.

  In order to achieve the above-described object, the variable valve operating apparatus of the present invention has the following configuration. That is, the variable valve device of the present invention can be inserted into two types of cam lobes with different cam profiles, a plurality of outer cams that hold the cam lobes in cylinder units or cylinder group units, and a switching groove formed in the outer cam. And a solenoid coil that protrudes when energized and is inserted into the switching groove. The variable valve operating apparatus switches the driving cam lob that actually drives the valve between the two types of cam lobes by sliding the outer cam in the axial direction of the camshaft by inserting the solenoid pin into the switching groove.

  Furthermore, when the solenoid pin is not inserted into the switching groove, the variable valve operating device applies a weak voltage smaller than the voltage applied to the solenoid coil when switching the drive cam lobe to the solenoid coil. The resistance value is calculated, and the voltage applied to the solenoid coil or the start timing of voltage application when the drive cam lobe is switched according to the resistance value of the solenoid coil is controlled.

  According to the present invention, when the drive cam lobe is switched, the resistance value of the solenoid coil is calculated in advance, so that, for example, the start timing of voltage application to the solenoid coil flows to the solenoid coil when the drive cam lobe is switched. The timing can be determined according to the current value. Therefore, the solenoid pin insertion can be controlled with high accuracy, and control variations can be suppressed.

It is the schematic which shows the structural example of the outer cam of a variable valve apparatus. It is the schematic which shows the structural example of the solenoid of a variable valve apparatus. It is a timing chart for demonstrating control of protrusion of the pin of a solenoid. It is a figure for demonstrating the relationship between the applied current to the coil of a solenoid, and the full stroke time of the pin of a solenoid. It is a figure for demonstrating the relationship between the coil temperature and resistance value of a solenoid, and the relationship between coil temperature and an electric current value. In embodiment, it is a flowchart for demonstrating the control routine which a control apparatus performs.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment.
[Configuration of variable valve gear]
In the present embodiment, the variable valve gear is mounted on a vehicle and used. As will be described later, the variable valve operating apparatus has a cam shift structure in which a pin is inserted into a switching groove of the outer cam to slide the outer cam using the rotation of the cam to switch the cam lobe. The variable valve operating apparatus includes a camshaft connected to the crankshaft of the engine and rotating in synchronization with the crankshaft. An outer cam formed of a hollow shaft is disposed on the camshaft at intervals corresponding to each cylinder.

  FIG. 1 is a schematic view showing a configuration example of an outer cam. In FIG. 1, the outer cam 10 is fixed in the rotational direction of the camshaft, and is slidable in the axial direction of the camshaft. 1A to 1D show the posture of the outer cam 10 obtained by rotating the camshaft by 90 degrees.

  The outer cam 10 carries two types of cam lobes 14 and 16 having different cam profiles in an adjacent state. Here, the cam profile means at least one of a lift amount and a working angle. In FIG. 1, the outer cam 10 is arranged in units of cylinders, and holds two sets of two types of cam lobes 14 and 16 per cylinder. This is because two intake / exhaust valves are provided for each cylinder. However, the number of valves per cylinder and the number of cam lobes corresponding thereto are not limited thereto. Further, the outer cam 10 is not limited to one that holds the cam lobes 14 and 16 in units of cylinders, and may be one that holds the cam lobes 14 and 16 in units of cylinder groups.

  A groove 18 is formed on the surface of the outer cam 10. The groove 18 is formed so that it is branched into two in the middle, and the branched portions extend in the axial direction of the camshaft in a spiral shape. In order to particularly distinguish the portion of the groove 18, the groove 18 after branching is referred to as grooves 18a and 18b, and the groove 18 before branching is referred to as groove 18c.

  The variable valve operating apparatus includes a solenoid 20 having two cam switching pins 22a and 22b for each cylinder as an actuator for switching a cam lobe. Hereinafter, when it is not necessary to distinguish the pins 22a or 22b, they are simply referred to as “pins 22”.

  The solenoid 20 is a self-holding solenoid, for example. FIG. 2 is a diagram illustrating a configuration example of a self-holding solenoid. As shown in FIG. 2, the solenoid 20 includes shafts 24a and 24b. Permanent magnets, springs, and the like are provided on the base end sides of the shafts 24a and 24b. The solenoid 20 has coils 26a and 26b and fixed iron cores 28a and 28b arranged in the housing.

  In the solenoid 20, the pin 22a operates in conjunction with the shaft 24a, and the pin 22b operates in conjunction with the shaft 24b. In FIG. 2, the shaft 24a and the pin 22a are in a protruding state. On the other hand, the coil 26b is not energized, and the shaft 24a and the pin 22b are in a retracted state. By energizing the coil 26a or 26b, the protruding state and the retracted state of the pin 22a or 22b can be switched. Further, when the energization of the solenoid 20 is cut off, the pin 22 is held in a retracted state by a permanent magnet, a spring, or the like.

  In the present embodiment, the variable valve gear includes an ECU as a control device. The ECU includes a RAM (random access memory), a ROM (read only memory), a CPU (microprocessor), and the like. The ECU captures and processes signals from various sensors mounted on the vehicle. The ECU processes the signals of the various sensors taken in and operates various actuators including the solenoid 20 in accordance with a predetermined control program.

[Cam lobe switching operation example]
With reference to FIG. 1 again, an example of the rotation operation of the outer cam 10 by the engagement of the pin 22 and the groove 18 will be described. In FIG. 1, it is assumed that the outer cam 10 rotates in a direction from the upper side to the lower side. In FIG. 1A, the pins 22a and 22b are both retracted. The pin 22a faces the groove 18a, and the pin 22b faces the portion of the outer cam 10 where the groove 18 is not formed.

  In the state of (B) in which the outer cam 10 is rotated 90 degrees from (A) in FIG. 1, the grooves 18 a and 18 b move to the near side, and the groove facing the paper surface and the pins 22 a and 22 b in FIG. The part of 18a, 18b formed in the orthogonal direction with respect to the axis | shaft of the outer cam 10 has appeared. Hereinafter, the portions of the grooves 18a and 18b in the orthogonal direction are also referred to as “orthogonal portions”.

  In FIG. 1B, when the coil 26a of the solenoid 20 is energized, the pin 22a is protruded, and the protruded pin 22a is smoothly inserted into the orthogonal portion of the groove 18a and engaged with the groove 18a. . As will be described later, the protrusion of the pin 22 is performed while the orthogonal portion of the groove 18 faces the pin 22.

  In the state of (C) rotated 90 degrees from (B) of FIG. 1, the portion facing the paper surface and pins 22a, 22b of FIG. 1 is inclined with respect to the axis of the outer cam 10 of the grooves 18a, 18b. The part that appears. The inclined portions of the grooves 18a and 18b depicted in FIG. 1C are also referred to as “inclined portions”. As can be seen by comparing FIG. 1C and FIG. 1B, in the state where the groove 18a is inserted into the pin 22a, the pin 22a moves along the inclined portion of the groove 18a, so that the outer cam 10 Slides to the left.

  In the state of (D) rotated 90 degrees further from (C) of FIG. 1, a groove 18 c appears on the paper surface of FIG. 1 and the portion facing the pins 22 a and 22 b. In this state, sliding of the outer cam 10 to the left is completed, and the cam lobe is switched.

  The switching by the pin 22b is performed in the same manner. That is, the protrusion of the pin 22b is performed while the pin 22 is opposed to the orthogonal portion of the groove 18b. When the pin 22 is inserted into the groove 18b, the outer cam 10 slides to the right as the pin 22b engaged with the groove 18b moves along the inclined portion of the groove 18b.

[Control of pin 22 protrusion]
FIG. 3 is a timing chart for explaining the control of the protrusion of the pin 22 when the cam lobe is switched. The cam lobe switching operation is performed during one rotation of the camshaft, and the cam lobe switching start timing, that is, the timing at which the outer cam 10 starts moving leftward or rightward depends on the engine speed and cam angle. Will be decided accordingly. Then, the target angle for completion of insertion of the pin 22 (that is, completion of the full stroke) is determined to be an angle that is advanced by a necessary margin from the switching start timing. The margin required here is appropriately determined in consideration of the margin required for control delay, hardware variation, and rotation increase.

  The insertion of the pin 22 is set so as to be completed during the pin insertion section, which is a period in which the pin 22 faces the orthogonal part of the groove 18. That is, the energization start timing for the solenoid 20 is set to an angle corresponding to the full stroke time, which is the time from the start of energization to the solenoid 20 until the protrusion of the pin 22 is completed, rather than the target angle for completion of full stroke. Only the angle obtained by adding the angle of the allowance considering the variation becomes the previous (that is, the advance side) angle.

[Calculation of full stroke time]
FIG. 4 is a diagram for explaining the relationship between the current value applied to the solenoid and the full stroke time of the solenoid. As shown in FIG. 4, the full stroke time has a correlation with the current value applied to the solenoid 20, and as the current value increases, the full stroke time decreases. The full stroke time can be calculated according to this correlation.

  FIG. 5 is a diagram for explaining the relationship between the coil temperature of the solenoid, the resistance value of the coil, and the current. As shown in FIG. 5, when the coil temperature increases, the resistance values of the coils 26a and 26b increase. Therefore, even when the same voltage is applied, the value of the current flowing through the coils 26a and 26b decreases as the coil temperature increases. As described above, since the value of the current flowing through the coils 26a and 26b changes according to the coil temperature, the full stroke time changes when the voltage applied to the solenoid 20 is constant.

  Therefore, in the present embodiment, the full stroke time is predicted before the pin 22 is protruded, and the protrusion of the pin 22 is completed during the pin insertion period according to the predicted full stroke time. The start timing of energizing the solenoid 20 is set. Specifically, when there is a cam lobe switching request, first, a weak voltage in a range where the pin 22 is not protruded is applied, and at that time, the current value flowing through the coil 26a or 26b is measured, whereby the coil 26a or The resistance value of 26b is calculated. In accordance with the calculated resistance value and the applied voltage value applied when the pin 22 protrudes, the current value flowing through the coil 26a or 26b when the pin 22 protrudes is calculated. According to the calculated current value, the full stroke time is calculated according to the relationship between the current value and the full stroke time. The energization start timing for the solenoid 20 is determined according to the calculated full stroke time.

[Specific Control of this Embodiment]
FIG. 6 is a flowchart for explaining a control routine executed by the control device in the present embodiment. In the routine of FIG. 6, it is first determined in step S102 whether or not a cam lobe switching request has been detected. If a cam lobe switching request is not detected in step S102, the current process is temporarily terminated.

  If a cam lobe switching request is detected in step S102, a weak voltage is applied to the solenoid 20 in step S104. Next, in step S106, the value of the current flowing through the solenoid 20 when the weak voltage is applied is measured.

  Next, in step S108, the resistance value of the coil 26a or 26b is calculated based on the relationship between the voltage and the current. Next, in step S110, the resistance value of the coil 26a or 26b and the applied voltage applied when the pin 22 protrudes are acquired. In step S112, the full stroke time is calculated according to the acquired resistance value and applied voltage of the coil 26a or 26b.

  Next, in step S114, the current cam angle and engine speed are acquired. In step S118, the energization start timing for the solenoid 20 is determined. More specifically, the energization start timing is calculated as an angle obtained by advancing the full stroke end target angle calculated from the current cam angle and engine rotation speed by the energization advance angle corresponding to the full stroke time. .

  Next, in step S120, energization is started at the calculated energization start timing. In step S122, energization is turned off after the full stroke is completed, and the current switching process is completed.

  As described above, according to the present embodiment, the resistance values of the coils 26a and 26b can be detected by applying a weak voltage before the cam lobe switching is started. Therefore, it is possible to execute the protrusion of the pin 22 while securing a necessary full stroke time according to the current resistance value of the coil. Therefore, even when the resistance value fluctuates due to a temperature change of the coil, cam lobe switching can be controlled with high accuracy, and control variations can be suppressed.

  In the present embodiment, the control for calculating the full stroke time from the resistance values of the coils 26a and 26b and determining the energization start timing according to this is described. However, the voltage applied to the solenoid 20 may be controlled so that a target current value is applied to the coils 26a and 26b in accordance with the resistance values of the coils 26a and 26b.

10 Outer cam 14, 16 Cam lobe 18, 18a, 18b, 18c Groove 20 Solenoid 22, 22a, 22b Pin 24a, 24b Shaft 26a, 26b Coil 28a, 28b Fixed iron core

Claims (1)

Two types of cam lobes with different cam profiles,
A plurality of outer cams that hold the cam lobes in cylinder units or cylinder group units;
A solenoid pin disposed so as to be inserted into a switching groove formed in the outer cam;
A solenoid coil that projects the solenoid pin by energization and inserts it into the switching groove;
With
A variable valve operating apparatus that switches between the two types of cam lobes by actually sliding the outer cam in the axial direction of the camshaft by inserting the solenoid pin into the switching groove. There,
When the solenoid pin is not inserted into the switching groove, a weak voltage smaller than the voltage applied to the solenoid coil when switching the drive cam lobe is applied to the solenoid coil, and the resistance value of the solenoid coil To calculate
Control the applied voltage to the solenoid coil or the start timing of voltage application when switching the drive cam lobe according to the resistance value of the solenoid coil.
A variable valve operating apparatus configured as described above.

Images