JP2005105887A - Engine valve system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To set an optimum lift load in not only normal operation but also transient response. <P>SOLUTION: The spring constant of a valve spring 5 for pushing up a valve 1 is set to be a value for normal operation in a region where an engine speed Ne and an engine revolving acceleration α are both low. In a region where the engine speed Ne and the engine revolving acceleration α are both high, a solenoid coil 6 is excited by carrying a current from an assist control unit 7 to generate an assist load Fa' which operates on a valve stem 2 in the same direction as that of the energizing force of the valve spring 5. As a result, in a low revolution/low revolving acceleration region, a lift load Fv for pushing up the valve 1 is generated by the sum of a spring load Fs of the valve spring 5 and an inertial load Fi of the valve 1. In a region where at least one of the engine speed Ne and the engine revolving acceleration α is high, the lift load Fv is increased by the assist load Fa' and set to be an optimum value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a valve operating apparatus for an engine that varies an urging force applied to a valve in accordance with an engine speed or the like.

  In general, in a four-cycle engine, an intake valve and an exhaust valve are respectively provided in an intake port and an exhaust port formed in a cylinder head, and a stem end of a valve stem provided in each valve is formed by an intake cam and an exhaust cam. By pressing at a predetermined timing, each port is opened.

  A spring retainer is fixed to each stem end, and each valve is always urged in the valve closing direction by the urging force of the valve spring interposed between the spring retainer and the spring seat formed on the cylinder head. Yes.

By the way, the lift load Fv that pushes up the valve stem is the sum of the urging force (spring load) Fs of the valve spring and the inertia load Fi, excluding the load due to natural vibration,
Fv = Fs + Fi (1)
It becomes.

Here, the spring load Fs can be obtained approximately from Expression (2).
Fs≈L · k + ko (2)
Here, L is the valve lift amount, k is the spring constant of the valve spring, and ko is the set load of the valve spring.

Further, the inertial load Fi can be obtained approximately from the equation (3).
Fi≈M · a (3)
Here, M is the mass of the valve, and a is the valve lift acceleration.

  As shown in Expression (2), the spring load Fs is a value determined by the valve lift amount L and is hardly affected by the engine speed. On the other hand, since the inertial load Fi is determined by the valve lift acceleration a, as is clear from the equation (3), it is affected by the engine rotation fluctuation.

  As shown in FIG. 7, the valve lift acceleration a rapidly increases near the beginning of valve opening and near the end of closing, and shows a negative acceleration near the maximum valve lift position (crank angle β). In the vicinity of the maximum valve lift position (crank angle β), a negative acceleration is indicated. Therefore, when determining the spring constant k of the valve spring, it is necessary to consider valve bounce and jump at the maximum valve lift position (crank angle β). There is.

To suppress valve bounces and jumps,
| Fs |> | Fi | (4)
Must satisfy the relationship. In other words, as shown in FIG. 7, it is necessary to set the lift load Fv at the maximum valve lift position (crank angle β) to be 0 or more. In order to satisfy the inequality (4) in the entire operation region, the spring load Fs may be set large.

  However, if the spring load Fs is set to be large, the friction increases and affects the output and fuel consumption, so it cannot be set to a value larger than necessary.

As a countermeasure, for example, in JP-A-2-221608, a permanent magnet and an electromagnet are arranged opposite to a spring retainer and a spring seat that support both ends of a valve spring, and the energization direction and current value for the electromagnet are set. A technique is disclosed in which the lift load Fv is adjusted using the attractive and repulsive forces generated between the two magnets by variably setting according to the engine speed.
JP-A-2-221608

  Japanese Patent Application Laid-Open No. 2-221608 discloses a technique for setting an electric current value for an electromagnet according to an engine speed using the engine speed as a parameter. A valve lift acceleration a as a function of the inertia load Fi is Since it is influenced by the engine speed and the engine rotational acceleration, the lift load Fv cannot be adjusted to an optimum value only by the engine speed.

  That is, for example, at the time of a transient response such as when the accelerator pedal is depressed even when the engine is in a low speed range, the inertial load Fi increases as the engine rotational acceleration increases, so an attempt was made to obtain the optimum lift load Fv. In this case, it is necessary to set the engine rotational acceleration in consideration.

  Further, since the permanent magnet is fixed to the spring retainer, the inertial mass of the valve system increases, and therefore the inertial load Fi increases. Therefore, in order to maintain the relationship of inequality (4), the spring load Fs must be increased. As a result, the lift load Fv becomes large, making it difficult to employ it in recent engines that tend to have low fuction.

  In view of the above circumstances, the present invention can set an optimum lift load not only during steady operation but also during transient response, and not only provides good operating performance but also increases the inertial mass of the valve train. It is an object of the present invention to provide an engine valve operating device that suppresses the above-described problem and enables low friction.

  In order to achieve the above object, the present invention provides a valve spring that constantly biases a valve that is driven to open by a cam that rotates synchronously with a crankshaft, and an auxiliary bias that biases the valve in the closing or opening direction. And an urging force of the auxiliary urging means is controlled on the basis of the engine speed and the engine rotational acceleration.

  According to the present invention, since the urging force of the auxiliary urging means is controlled based on the engine speed and the engine rotation acceleration, it is possible to set an optimum lift load not only during steady operation but also during transient response, Good driving performance can be obtained.

  Further, by arranging the auxiliary urging means along the side surface of the lifter, an increase in the inertial mass of the valve operating system is suppressed, and low friction can be realized.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration diagram of a valve operating apparatus having a valve spring assist mechanism.

  Reference numeral 1 in the figure denotes an intake / exhaust valve. The intake / exhaust valve is a general term for an intake valve and an exhaust valve, and is applied to all intake valves and exhaust valves provided in each cylinder.

  A spring retainer 3 is fixed to the stem end of the valve stem 2 of the intake / exhaust valve 1, and a valve formed at the lower end of the valve stem 2 between the spring retainer 3 and a spring seat 4 a formed on the cylinder head 4. A valve spring 5 that constantly urges the body 2a in the valve closing direction is interposed. Although not shown, a cam is connected to the stem end of the valve stem 2 via a rocker arm. The cam is provided on a camshaft that rotates synchronously with the crankshaft at a speed of 1/2.

  A solenoid coil 6 is disposed on the outer periphery of the valve stem 2. The solenoid coil 6 may be disposed so as to drive the spring retainer 3. Further, when the valve mechanism is a direct acting type, a lifter is disposed on the upper part of the spring retainer 3, and the solenoid coil 6 may be disposed on the outer periphery of the lifter.

  Further, at least a region facing the solenoid coil 6 in the moving range of the valve stem 2 is formed of a magnetic material such as iron, and this portion functions as a plunger.

  The solenoid coil 6 is connected to an assist control unit 7, and a rotational speed sensor 8 that detects an engine rotational speed Ne [rpm] from the rotation of the crankshaft or the like is connected to the assist control unit 7. The assist control unit 7 calculates the engine rotational acceleration α [rpm / s] from the amount of change based on the engine rotational speed Ne detected by the rotational speed sensor 8, and based on the engine rotational speed Ne and the engine rotational acceleration α, Whether or not the solenoid coil 6 is energized is checked with reference to the operation region map shown in FIG.

  As shown in FIG. 2, the driving region map is divided into the driving region based on the engine speed Ne and the engine rotational acceleration α, and in the region where both the engine rotational speed Ne and the engine rotational acceleration α are low, the solenoid coil 6 is de-energized, and the solenoid coil 6 is energized in a region where at least one of the engine rotational speed Ne and the engine rotational acceleration α is high. Therefore, even if one of the engine rotational speed Ne and the engine rotational acceleration α is low but the other is high, the solenoid coil 6 is energized and excited.

  That is, even when the engine speed Ne is low, during a transient response when the accelerator pedal is depressed, the inertial load Fi increases as the engine rotational acceleration α increases. From this balance, the solenoid coil 6 is energized, and the valve stem 2 The assist load Fa is generated by electromagnetic force to apparently increase the spring load Fs.

  In addition, even in a region where the engine speed Ne is high, such as constant speed traveling on a high-speed road, the acceleration at the time of opening and closing of the intake / exhaust valve 1 increases in proportion to the engine speed Ne, and the inertia load Fi also increases. Therefore, from the balance, the solenoid coil 6 is energized, and the spring load Fs is apparently increased.

  On the other hand, in a region where both the engine speed Ne and the engine rotational acceleration α are low, such as when driving on a general road at a constant speed, the inertial load Fi is low. The valve stem 2 is pushed up with the lift load Fv.

  That is, when the solenoid coil 6 is excited by energization, an assist load Fa that urges the valve stem 2 in the valve closing direction is generated in the valve stem 2. As a result, the spring load Fs becomes a virtual spring load Fs ′ to which the assist load Fa is added.

Fs′≈Fs + Fa (2 ′)
In order to suppress valve bounce and jump, the virtual spring load Fs ′ and the inertia load Fi are similar to the inequality (4).
| Fs '|> | Fi | (4')
It is necessary to satisfy the relationship. In other words, as shown in FIG. 4, the lift load Fv at the maximum valve lift position (crank angle β) is set to be at least zero.

  In this embodiment, as the valve spring 5, in a region where both the engine speed Ne and the engine rotational acceleration α are low (non-energized region in FIG. 2), as shown in FIG. 7, at the maximum valve lift position (crank angle β). A low-load spring having a spring constant k such that the lift load Fv is at least 0 is employed.

  Further, when the solenoid coil 6 is energized, the electromagnetic force generated in the valve stem 2 is as shown in FIG. 4 in a region where one of the engine rotational speed Ne and the engine rotational acceleration α is high (the energized region in FIG. 2). In addition, the lift load Fv at the maximum valve lift position (crank angle β) is set to a value that can generate the assist load Fa so that it is at least zero.

Next, the operation of this embodiment will be described.
When the engine is operating, the camshaft rotates at a half speed in synchronization with the rotation of the crankshaft. As the cam shaft rotates, the cam provided on the cam shaft presses the valve stem 2 of the intake / exhaust valve 1 at a predetermined timing and opens the valve stem 2 against the urging force of the valve spring 5.

  At this time, the assist control unit 7 reads the engine rotational speed Ne [rpm] detected by the rotational speed sensor 8, and further calculates the engine rotational acceleration α [rpm / s] from the change in the engine rotational speed Ne.

  Next, using the engine speed Ne and the engine rotational acceleration α as parameters, the operation region map shown in FIG. 2 is referred to and it is checked whether the current operation region is a non-energized region or an energized region.

  When the current is in the non-energized region, the solenoid coil 6 is not energized. As a result, the lift load Fv that pushes up the valve stem 2 is approximately the sum of the spring load Fs proportional to the spring constant k of the valve spring 5 and the inertia load Fi (Fv = Fs + Fi) according to the equation (2). In a region where both the engine speed Ne and the engine rotational acceleration α are low, it is possible to realize low friction. In addition, the engine output can be improved relatively, and fuel consumption can be reduced.

  Further, when the operation region is the energization region, that is, when at least one of the engine speed Ne and the engine rotation acceleration α is high, the solenoid coil 6 is energized. Then, the solenoid coil 6 is excited, and the valve stem 2 generates an assist load Fa due to electromagnetic force.

  As a result, as shown in FIG. 4, the sum of the virtual spring load Fs ′ obtained by adding the assist load Fa to the spring load Fs and the inertia load Fi becomes a lift load Fv that pushes up the valve stem 2 (Fv = Fs ′). + Fi).

  Accordingly, at least one of the engine rotational speed Ne and the engine rotational acceleration α is high, and even if the inertia load Fi increases accordingly, the lift load Fv is increased by the assist load Fa. At (crank angle β), the lift load Fv is at least 0, and valve bounce and jump can be suppressed.

  Note that the boundary between the energized region and the non-energized region in the operation region map shown in FIG. 2 is determined by the balance between the inertial load Fi and the spring constant k of the valve spring 5 for each operation region.

  Further, in this embodiment, the current value supplied to the solenoid coil 6 is constant, but the assist load Fa generated in the valve stem 2 is proportionally controlled by variably controlling the current value or by duty control. May be. For example, in the driving region map shown in FIG. 3, the engine speed Ne and the engine rotational acceleration α are used as parameters, and the non-energized region shown in FIG. 2 is duty cycle as the engine rotational speed Ne and the engine rotational acceleration α increase. The ratio is set to increase stepwise from 10% to 80%.

  According to the operation region map shown in the figure, the assist load Fa can be generated even in a region where both the engine speed Ne and the engine rotational acceleration α are low. The load Fv can be obtained.

  In this case, the current value or duty ratio energized to the solenoid coil 6 is influenced by the intake pipe pressure by taking into account the intake pipe pressure downstream of the throttle valve or the exhaust pressure during exhaust brake operation in the case of a diesel engine. If this is set in consideration, finer control becomes possible.

  As another aspect of the present embodiment, the valve spring 5 may be a high load spring, and the assist load Fa generated by energizing the solenoid coil 6 may be operated in a direction opposite to the urging direction of the valve spring 5. .

  Specifically, the lift load Fv at the maximum valve lift position (crank angle β) in a region where at least one of the engine rotational speed Ne and the engine rotational acceleration α is high is at least 0. Set to a value such that The solenoid coil 6 is deenergized in the energized region of FIG. 2 and energized in the non-energized region.

As a result, in this aspect, the normal spring load Fs is set in the energization region of FIG. On the other hand, in the non-energized region, a virtual spring load Fs ″ as shown in Expression (2 ″) is set.
Fs ″ ≈Fs−Fa (2 ″)
Next, a specific arrangement example of the solenoid coil 6 will be described.

  FIG. 5 shows a cross-sectional view of a main part of the valve gear according to the first embodiment. In addition, about the same component as FIG. 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The valve stem 2 is inserted into and supported by a valve guide 11 mounted on the cylinder head 4 so as to freely advance and retract. A yoke 12 is fixed to the upper end of the valve guide 11, and the solenoid coil 6 is housed in the yoke 12.

  Further, a cylindrical portion 13 that extends from the spring retainer 3 and is attached to the valve stem 2 is exposed between the inner periphery of the solenoid coil 6 and the valve stem 2. A side surface of the spring retainer 3 facing the solenoid coil 6 of at least the cylindrical portion 13 is formed of a magnetic material, and this portion functions as a plunger. Accordingly, the entire spring retainer 3 may be formed of a magnetic material.

  In this embodiment, the assist coil Fa is generated by exciting the solenoid coil 6 and generating an electromagnetic force in the cylindrical portion 13.

  Thus, in this embodiment, since the solenoid coil 6 is fixed to the valve guide 11 via the yoke 12, the inertial mass of the valve stem 2 does not increase and the increase in the inertial load Fi can be relatively suppressed. it can.

  FIG. 6 shows a cross-sectional view of the main part of the valve gear according to the second embodiment. In addition, about the same component as FIG. 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  This embodiment shows an example in which the valve spring assist mechanism according to the present embodiment is applied to a direct acting valve mechanism. In the direct-acting valve mechanism, a piston-type lifter 21 is connected to the stem end of the valve stem 2, and a shim 22 that adjusts the valve clearance is mounted on the top. Further, an intake / exhaust cam 23 is slidably contacted on the shim 22. The intake / exhaust cam 23 is a general term for an intake cam and an exhaust cam, and is applied to all intake / exhaust cams and exhaust cams arranged in each cylinder.

  When the intake / exhaust cam 23 rotates during engine operation, this rotational motion is converted into a reciprocating motion by the lifter 21 slidably in contact with the intake / exhaust cam 23, and the valve body 2a provided at the lower end of the valve stem 2 opens and closes Is done.

  The lifter 21 is formed in a cylindrical shape, and its side surface 21 a reciprocates along the cylinder part 4 a formed in the cylinder head 4. A solenoid coil 6 is attached to a portion of the cylinder portion 4a that faces the moving region of the side surface 21a. A portion of at least the side surface 21a of the lifter 21 facing the solenoid coil 6 is formed of a magnetic material, and this portion functions as a plunger. Therefore, the entire lifter 21 may be formed of a magnetic material.

  The solenoid coil 6 generates an electromagnetic force on the side surface 21a of the lifter 21 to generate an assist load Fa.

  In this embodiment, since the solenoid coil 6 is fixed to the cylinder portion 4a formed in the cylinder head 4, the inertial mass of the valve stem 2 does not increase, and the increase in the inertial load Fi can be relatively suppressed.

Schematic configuration diagram of a valve gear equipped with a valve spring assist mechanism Illustration of operation area map Illustration of driving area map according to another aspect Explanatory drawing of lift load that pushes up valve stem The principal part schematic block diagram of the valve operating apparatus provided with the valve spring assist mechanism by Example 1. FIG. The principal part schematic block diagram of the valve operating apparatus provided with the valve spring assist mechanism by Example 2 Explanatory drawing of lift load that pushes up conventional valve stem

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Intake / exhaust valve 2 Valve stem 3 Spring retainer 4 Cylinder head 5 Valve spring 6 Solenoid coil 7 Assist control unit 8 Rotational speed sensor 13 Cylindrical part 21 Lifter 21a Side surface 23 Intake / exhaust cam alpha Engine rotational acceleration Fa Assist load Fi Inertial load Fs Spring load Fs' Virtual spring load Fv Lift load Ne Engine speed a Valve lift acceleration k Spring constant

Agent Patent Attorney Susumu Ito

Claims (4)

A valve spring that constantly biases the valve that is driven to open by a cam that rotates synchronously with the crankshaft, in the closing direction;
In a valve operating apparatus for an engine comprising auxiliary biasing means for biasing the valve in a closing direction or an opening direction,
A valve operating apparatus for an engine, wherein the urging force of the auxiliary urging means is controlled based on an engine speed and an engine rotational acceleration. 2. The engine valve operating apparatus according to claim 1, wherein the urging force of the auxiliary urging means is increased as at least one of the engine rotational speed and the engine rotational acceleration increases. The auxiliary biasing means is an electromagnetic solenoid,
3. The valve operating device for an engine according to claim 1, wherein the valve operating device is arranged along a side surface of a cylindrical portion extending from a spring retainer that supports the valve spring. The auxiliary biasing means is an electromagnetic solenoid,
3. The engine valve operating apparatus according to claim 1, wherein the engine valve operating apparatus is disposed along a side surface of a lifter provided in the direct acting valve operating apparatus.

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