JPH0544502A - Engine valve timing control device - Google Patents

Abstract

PURPOSE:To raise fuel consumption efficiency in a normal operation region and enhance starting characteristic at the time of cold starting and also suppress power consumption at the time of hot starting and so lower the battery burden in controlling a valve timing variable mechanism having members being actuated according to applied voltage. CONSTITUTION:In a control section 20 for a valve timing variable mechanism 3, there are disposed a basic control means 26 whereby the voltage is not applied in a low/intermediate load region at higher rotation than a specified rotational speed and the voltage is applied in a region at lower rotation than a specified rotational speed and in a high load region and a starting control means 28 whereby the voltage is applied at the time of engine cold starting and the voltage is not applied at the time of hot starting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve timing control device for an engine equipped with a valve timing variable mechanism that is electrically operated to change the phases of a camshaft and a crankshaft.

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-63-162910.
As disclosed in Japanese Patent Publication No. JP-A-2003-264, a phase changing member (advancing ring or the like) and an electrically operated pressing member (retarder) are provided, and the pressing member is operated in response to voltage application and voltage release. A valve timing variable mechanism is known in which the phase of the camshaft and the crankshaft changes when the phase changing member is switched between the pressed state and the pressed release state. That is, the device disclosed in this publication connects an advancing member that is axially movable within a certain range to a hub member attached to a camshaft and an input member that interlocks with a crankshaft. The hub member and the input member are configured to rotate relative to each other in accordance with the axial movement of the advancing member, and the advancing ring and the hub member, which are rotatably coupled to the advancing member, are screw-shaped with respect to each other. Is provided and screwed with each other, and a non-rotating pressing member composed of an electromagnetic coil is arranged so as to face the advancing ring. When a voltage is applied to the pressing member, the pressing member is pressed against the advancing ring by an electromagnetic force, and the braking force by the frictional force acts on the advancing ring, so that the advancing ring moves by a predetermined rotation angle. Relative displacement causes the advancing member to move in the axial direction, which changes the rotational phase of the camshaft with respect to the input member. In this way, the opening / closing timing of the intake valve or the exhaust valve changes depending on whether the voltage is applied to the pressing member or when the applied voltage is released.

[0003]

In this type of device, the valve timing can be switched between the basic timing equivalent to the case of fixing the general valve timing and the specific timing changed to the pumping loss reducing direction. For example, the opening / closing timing of the intake valve can be switched to a basic timing and a specific timing in which the compression amount is reduced by retarding the basic timing to control the above specific timing in a normal operation region where there is a strong demand for improving fuel consumption. This has been done conventionally. When the variable valve timing mechanism having the pressing member composed of the electromagnetic coil is used, the basic timing is set in the voltage released state corresponding to the normal state, and the specific timing is set when the voltage is applied. However, it is common.

However, in this way, in the normal operation region where the fuel consumption is required to be improved, even if the pumping loss is reduced by setting the above-mentioned specific timing, the power is consumed because the voltage is applied. Also, energy loss occurs due to the frictional force applied to the rotating portion by the pressing member, so that the effect of improving fuel efficiency is reduced.

In view of this, the valve timing variable mechanism is configured so that the pumping loss is reduced at a specific timing when the voltage is released, and the pumping is controlled by controlling the valve to be in the voltage released state in the normal operation region. It is possible to reduce power consumption and energy loss due to frictional resistance when the loss is reduced, but in this case, the following problems remain.

That is, in this case, since the combustion stability is likely to be impaired if the above-mentioned specific timing is set at the time of idling, etc., combustion is performed with the valve timing as the basic timing by setting the voltage application state in the low rotation region. It is desirable to improve the sex. Then, even when the engine is started, it is required to enhance the combustibility to promote the start, especially at the cold start when the engine temperature is low, but on the other hand, a lot of electric power is required for the starter and the like when the engine is started. There is a demand to minimize the power consumption of the variable valve timing mechanism. There was room for improvement in this respect.

In view of such circumstances, the present invention improves the fuel efficiency in the normal operation region and improves the startability at the cold start, while the power consumption in the variable valve timing mechanism at the warm start. It is an object of the present invention to provide a valve timing control device for an engine capable of suppressing the load and reducing the load on the battery.

[0008]

In order to achieve the above-mentioned object, the present invention is such that a pressing member switches between a pressing state and a pressing release state with respect to a phase changing member in response to voltage application and voltage release. In an engine having a variable valve timing mechanism configured to change the phase between the camshaft and the crankshaft due to the change, the valve timing becomes a predetermined basic timing when voltage is applied, and the valve timing becomes the above basic timing when voltage is released. In comparison with setting the valve timing variable mechanism so as to have a specific timing that reduces pumping loss, the control unit that switches between the voltage applied state and the voltage released state for this valve timing variable mechanism is In the low / medium load region on the high rotation side, the above voltage is released and the area on the low rotation side is lower than the specified rotation speed. And a basic control means for setting the voltage applied state in the high load region, and a start-time control for setting the voltage applied state at the cold start and releasing the voltage state at the warm start based on detection of the engine temperature at the engine start. And means are provided.

[0009]

According to the above construction, in the low and medium load region on the high rotation side of the predetermined rotation speed which is the normal operation region, the pumping loss is reduced by setting the valve timing to the specific timing, and When the voltage is released, the power is saved and the energy loss due to the frictional force of the pressing member is removed. Further, while the valve timing which is advantageous for promoting the start is set at the cold start by the control of the starting control means, the power consumption of the variable valve timing mechanism is set at the warm start when the startability is originally relatively good. Can be avoided.

[0010]

Embodiments of the present invention will be described with reference to the drawings.
The structure of the variable valve timing mechanism in one embodiment of the present invention is shown in FIG. In this figure, reference numeral 1 denotes a camshaft that regulates the opening / closing timing of an intake / exhaust valve (not shown) of the engine, and a gear pulley 2a is provided on the outer peripheral surface outside one end of the camshaft so that the driving force of the engine is An input member 2 to be transmitted is arranged, and a valve timing variable mechanism 3 is provided between the input member 2 and the cam shaft 1. The variable valve timing mechanism 3 includes a hub 4 attached to the end of the camshaft 1, a drum 5 as a phase changing member, and an advancing plate 6.
The drum 5 is composed of an electromagnetic coil-type pressing member 7 or the like that switches between a pressed state and a pressed release state in response to voltage application and voltage release.

The hub 4 is fixed to the camshaft 1 by an end member 8 provided at the end of the camshaft 1 and a camshaft bolt 9. The drum 5 is arranged around the cam shaft 1, is connected to the hub 4 by the return spring 10, and the stopper plate 11 regulates the relative rotation range with respect to the cam shaft 1 and the hub 4. Corresponding screw portions 12 and 13 are formed on the outer peripheral surface of the drum 5 and the inner peripheral surface of the advancing plate 6, and the advancing plate 6 is screwed onto the drum 5. An engaging groove 15 is formed on the outer peripheral surface of the advancing plate 6 with which an axially extending ridge 14 protruding from the inner peripheral surface of the input member 2 engages.
And a slant groove 17 that engages with a helical pawl 16 that is connected to the hub 4. The helical pawl 16 and the oblique groove 17 are inclined in the circumferential direction by a certain angle with respect to the axial direction.

On the other hand, the pressing member 7 composed of the above electromagnetic coil
Is arranged so as to face the drum 5 around the camshaft 1, is fixed to the engine body while being prevented from rotating, and is attached so as to be movable in the axial direction. When no voltage is applied to the pressing member 7, the pressing member 7 is separated from the drum 5 and
The input member 2, the advancing plate 6, the hub 4, the drum 5, and the like rotate in a fixed positional relationship in a state where no braking force acts on the. On the other hand, when a voltage is applied to the pressing member 7, the pressing member 7 presses against the drum 5 and applies a braking force, so that the drum 5 moves relative to the hub 4 by a predetermined rotation angle regulated by the stopper plate 11. When the advancing plate 6 rotates, the advancing plate 6 moves in the axial direction by a certain amount, whereby the input member 2 and the camshaft 1 are relatively displaced in the rotational direction. In this way, the phase of the camshaft 1 with respect to the crankshaft changes according to the voltage application and the voltage release to the pressing member 7, and the valve timing changes.

As shown in FIG. 3, the variable valve timing mechanism 3 in this embodiment is such that the helical pawl 16 is tilted toward the camshaft rotation direction M, so that a voltage is applied to the pressing member 7 (with respect to the drum 5). The valve timing is advanced when the braking force is applied) than when the voltage is released. Then, as shown in FIG. 4, at least the opening / closing timing of the intake valve is changed by the variable valve timing mechanism 3, and the pumping loss is reduced at the valve timing at the time of releasing the voltage than at the valve timing at the time of applying the voltage. Is set. In other words, as is known from the past, the valve timing of the intake valve is a predetermined basic timing (general valve timing that is not intended to reduce pumping loss).
If the valve is retarded more than the above, the pumping loss reduction effect can be obtained, so the valve timing at the time of releasing the voltage becomes a specific timing that is retarded by a certain amount from the basic timing, and when the voltage is advanced, it becomes the above basic timing. ,
The variable valve timing mechanism 3 is set in advance.

With respect to the variable valve timing mechanism 3,
A control unit (EC) as a control unit for switching the voltage application and the voltage release to the electromagnetic coil type pressing member 7.
U) 20 is provided, and the electromagnetic coil type pressing member 7 is connected to the control unit 20 via the lead wire 7a. The control unit 20 includes an air flow meter 21 for detecting the amount of intake air, a rotation speed sensor 22 for detecting the engine speed, a starter switch 23 for detecting the start of the engine, and a water temperature sensor for detecting the cooling water temperature of the engine. Each signal from 24 and 24 is input.

As shown in FIG. 1, the control unit 20 is operated by an engine load equivalent amount such as an intake charge amount obtained from a signal from an air flow meter 21 and an engine speed detected by a speed sensor 22. State determination means 25, basic control means 26 for controlling voltage application according to this operation state determination, and means 27 for determining engine start based on a signal from the starter switch 23, engine speed, and the like. And a start time control means 28 for controlling the voltage application according to the start determination and the signal from the water temperature sensor 24. As the control by the basic control means 26, as shown in the control map of FIG. 5, the pressing member 7 of the variable valve timing mechanism 3 is turned on in the low and medium load region on the higher rotation side than the predetermined rotation speed.
FF (voltage released state), the pressing member 7 is turned ON (voltage applied state) in the low rotation side region and the high load region with respect to a predetermined rotation speed. Such a control map is previously stored in the control unit 20. It is stored. Also,
The control by the starting control means 28 is such that the pressing member 7 is turned on at the cold starting and the pressing member 7 is turned off at the warm starting.

FIG. 6 is a flow chart showing the control by the control unit 20. This control starts when the ignition switch and the starter switch are turned on to start the engine. At this engine starting stage, the engine water temperature is read in step S1 and the engine water temperature is equal to or higher than the set value in step S2. Whether or not warm start is determined by whether or not.

When the determination in step S2 is NO, that is, during cold start, the pressing member 7 is turned on in step S3.
It is said that. Then, in step S4, it is determined whether or not the start is completed by detecting the engine speed, etc., and the processes from step S1 are repeated until the start is completed. When the start is completed, the process proceeds to step S8 and subsequent steps described later.

When the determination in step S2 is YES, that is, during warm starting, the pressing member 7 is turned off in step S5.
FF. Then, in step S6, it is determined whether or not the start is completed, and the processes from step S1 are repeated until the start is completed. When the start is completed, the pressing member is turned on in step S7, and then the step is performed. The process moves to S8 and thereafter.

In step S8, the air flow meter 21
And the operating state is determined by the signal from the engine speed sensor 22. Subsequently, in step S9, as processing for performing the function of the basic control means 26, the O of the pressing member 7 is changed according to the operating state based on the control map shown in FIG.
Control to switch between N and OFF.

According to the apparatus of this embodiment, the valve timing variable mechanism 3 is controlled based on the control map of FIG. 5 by the processing as the basic control means 26 except when the engine is started. By the control based on this control map, in the low and medium load region on the higher rotation side than the predetermined rotation speed,
The pumping loss is reduced by setting the valve timing of the intake valve to a specific timing on the retard side, and further, such a valve timing is set when the voltage to the pressing member 7 is released, so that the pumping loss is reduced. At times, electric power is also saved, and energy loss due to frictional resistance due to the pressing member 7 is removed, so that fuel efficiency in this region is improved. In the high load region, the voltage is applied to the pressing member 7 and the valve timing is advanced to the basic timing, so that the engine output is increased and the basic timing is achieved even in the region lower than the predetermined rotation speed. By advancing to, the combustion stability at the time of idling etc. is enhanced.

On the other hand, as control at the time of engine starting by the starting control means 28, at the time of cold starting, as in the low rotation region when based on the above control map, the voltage is applied and the valve timing is up to the basic timing. By advancing the angle, the combustibility is enhanced and the starting is promoted, but at the time of warm starting, the load on the battery is reduced by being brought into the voltage release state. That is, when the engine is started, the power consumption is increased due to the drive of the starter, and the burden on the battery is likely to increase. Therefore, it is possible to avoid the power consumption in the variable valve timing mechanism 3 by setting the voltage release state. This is effective in reducing the load on the engine, and by doing so, the valve timing is delayed, but if the engine temperature is high, combustion failure will not occur, and startability will be ensured.

In the above embodiment, the valve timing of the intake valve is switched between the basic timing and the specific timing that is retarded by a certain amount, but the specific timing for reducing the pumping loss is less than the basic timing. Also, the timing may be advanced by a fixed amount, and in this case, the valve timing may be advanced when the voltage is released.

[0023]

According to the present invention, the valve timing variable mechanism is set so that the valve timing is the basic timing when the voltage is applied and the specific timing for reducing the pumping loss when the voltage is released. In the low to medium load region on the higher rotation speed side than the rotation speed, the basic control means for setting the voltage release state and the starting control means for setting the voltage application state at the cold start of the engine and the voltage release state at the warm start are provided. It is provided. Therefore, in the normal operation area, the pumping loss is reduced, the power consumption and the mechanical resistance are reduced to improve the fuel efficiency, and the combustibility is enhanced during the cold start to accelerate the start, and the variable valve timing mechanism is used during the warm start. It is possible to avoid power consumption and reduce the burden on the battery.

[Brief description of drawings]

FIG. 1 is a functional block diagram of a valve timing control device according to an embodiment of the present invention.

FIG. 2 is an overall sectional view of a variable valve timing mechanism.

FIG. 3 is a side view showing a cross section of a main part of a variable valve timing mechanism.

FIG. 4 is an explanatory diagram of valve timing.

FIG. 5 is a diagram showing a control map for controlling a valve timing variable mechanism according to an operating state.

FIG. 6 is a flowchart of valve timing control.

[Explanation of symbols]

 3 Valve timing variable mechanism 7 Electromagnetic coil type pressing member 20 Control unit 21 Air flow meter 22 Rotation speed sensor 23 Starter switch 24 Water temperature sensor 26 Basic control means 28 Starting control means

Claims (1)

[Claims] 1. A phase of a camshaft and a crankshaft changes as a pressing member switches between a pressing state and a pressing release state with respect to a phase changing member in response to voltage application and voltage release. In the engine having the variable valve timing mechanism configured as described above, the valve timing is variable so that the valve timing becomes a predetermined basic timing when a voltage is applied and the valve timing becomes a specific timing that reduces pumping loss compared to the basic timing when the voltage is released. The control unit, which sets the mechanism and switches between the voltage application state and the voltage release state for the variable valve timing mechanism, sets the voltage release state in the low / medium load region on the higher rotation side than the predetermined rotation speed, and sets the predetermined voltage. Basic control in which the above voltage is applied in the low-speed region and high-load region below the rotational speed Means and a start-time control means for setting the voltage applied state at the cold start and detecting the voltage release state at the warm start based on the detection of the engine temperature at the engine start. Timing control device.