JPH04159427A - Variable valve timing system - Google Patents

Abstract

PURPOSE:To increase a negative pressure inside a brake booster and improve feeling of using a brake by making such control as advancing the close timing of an intake valve when a specified deceleration condition is judged, in such a system in which the close timing of the intake valve is controlled to be on delay side at the time of a low load. CONSTITUTION:The valve timing of an internal combustion engine B which is provided with a throttle valve and mounted on a vehicle A is variably adjusted, and a valve timing system C controlled in such a way that the close valve timing of an intake valve is delayed at the time of a low load is provided with a variable valve timing device D which varies the valve timing of the intake valve and a control means E which operates the variable valve timing device D in response to the operational condition of the engine B. In this case, there is provided a deceleration condition judging means F which judges whether the driving condition of the vehicle A is under the specified acceleration or not, and when the vehicle A is judged by the deceleration condition judging means F, under the specified deceleration condition, the operation of the variable valve timing device D is controlled by the control means E so that the close timing of the intake valve may be advanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a variable valve timing system that variably adjusts the valve timing of an engine depending on the running condition of a vehicle and the operating condition of the engine.

[Conventional technology]

As is well known in the art, a cam is attached to the camshaft of an internal combustion engine, and the cam controls the opening and closing of intake valves and exhaust valves of the internal combustion engine. It is also known to provide a plurality of camshafts so that the intake valve and exhaust valve can be controlled separately.

Since the operating conditions of the engine change in various ways during operation, conventional fixed valve timing may not be very appropriate for the various conditions, and there is a limit to engine performance. Therefore, a technique is known in which a variable valve timing device is used to change the valve timing according to the operating condition of the engine so as to further improve the output, fuel efficiency, emission performance, etc. of the engine.

In such a variable valve timing device, when the load is low, the closing timing of the intake valve is generally delayed in order to lower the effective compression ratio and reduce the negative pressure in the intake pipe in order to reduce pump loss.

(For example, JP-A No. 59-119007, Utility Model Application No. 57-1
74712. (Utility Model Application Publication No. 59-137343) [Problem to be Solved by the Invention] When the brake is used, the load is generally low, and in the type of control described above, the closing timing of the intake valve is delayed. The variable noise timing device is controlled so that

However, when intake pipe negative pressure is taken into the brake booster,
For those with a brake device that utilizes that negative pressure,
When using the brakes, if the closing timing of the intake valve is delayed as described above, the negative pressure in the brake booster will decrease due to the increase in intake pipe pressure, and a large pedal force will be required when using the brakes. There was a problem that the usable area deteriorated.

The present invention solves the above problem by increasing the intake pipe negative pressure and increasing the negative pressure in the brake booster using a variable valve timing device when the vehicle is in a predetermined deceleration state. The purpose is

[Means to solve the problem]

The structure of the present invention that achieves the above object is shown in the claims correspondence diagram of FIG. That is, the present invention is a variable valve timing system C that variably adjusts the valve timing of an internal combustion engine B having a throttle valve mounted on a vehicle A, and is controlled to delay the closing timing of the intake valve when the load is low. The variable valve timing system C is
A variable valve timing device that varies the valve timing of an intake valve, a control means E that operates the variable valve timing device according to the operating state of an engine B, and a vehicle A.
and a deceleration state determination means F for determining whether the running state of the vehicle A is in a predetermined deceleration state, and when the deceleration state determination means F determines that the vehicle A is in the predetermined deceleration state, the control It is characterized in that the means E controls the operation of the variable valve timing device to advance the closing timing of the intake valve.

[Effect]

The deceleration state determining means determines whether the vehicle is in a predetermined deceleration state, and if the vehicle is in the predetermined deceleration state, the control means advances the closing timing of the intake valve. The variable valve timing device is operated as follows. This increases the negative pressure in the intake pipe and increases the negative pressure in the brake booster, which eliminates the need for a large pedal force when using the brakes and improves the feeling of using the brakes.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows an overall configuration diagram of the variable valve timing system of this embodiment.

1 is an intake valve, 2 is an exhaust valve, 3 is an intake camshaft, 4
is the exhaust camshaft, 5 is the intake pipe, 6 is the piston, 7
is a spark plug.

This internal combustion engine is a so-called DOHC type internal combustion engine, and each of the intake and exhaust camshafts has a timing pulley 8.9 attached to its shaft end, and a timing belt (not shown) pulls the pulley on the crankshaft. (not shown).

As is well known, the intake valve 1 and the exhaust valve 2 open while the camshaft 8.9 rotates.

In this embodiment, the intake camshaft 3 is provided with a variable valve timing device 10, which will be described later, so that the valve timing of the intake valve 1 can be changed.

Reference numeral 13 denotes a brake booster, which is communicated via a one-way valve 15 via a communication pipe 14 from the downstream side of the throttle valve of the intake pipe.

As is well known, the brake booster 13 is a brake force multiplier that utilizes intake pipe negative pressure, and a detailed explanation of its structure will be omitted.

A brake ON-OFF sensor 1 is attached to the brake 16, and detects whether the brake 16 is in use.

Note that the present invention can be applied to a 5ouc type internal combustion engine, and various known types of variable valve timing devices can be adopted. For example, a configuration as shown in FIG. 3 can be adopted.

The variable valve timing device used in this embodiment shown in FIG. 3 will be explained.

An inner sleeve 31 is integrally attached to the camshaft 3 on the circumferential surface of the shaft end of the intake camshaft 3 by means of knock pins 32 and bolts 33. A boss portion of a timing pulley 8 is held between the inner circumference of the inner sleeve 31 and the outer circumference of the camshaft 3 so as to be rotatable relative to the camshaft 3 but immovable in the axial direction. A cylindrical portion 34 coaxial with the camshaft 3 is formed in the timing pulley 3 so as to cover the outer peripheral side of the inner sleeve 31 .

The outer peripheral surface of the inner sleeve 31 and the cylindrical portion 3
Helical teeth are formed on the inner circumferential surfaces of the inner sleeves 4 over the entire circumference, and an outer sleeve 35 having helical teeth on the inner and outer peripheries is provided between the inner sleeve 31 and the cylindrical portion 34. The timing pulley 80 is arranged to mesh with teeth on the outer circumference of the timing pulley 80 and teeth on the inner circumference of the cylindrical portion 34 . The outer sleeve 35 is attached to a drive portion 37 of a step motor 36 via a bearing 38 so as to be relatively rotatable. The drive section 37 of the step motor 36 has an external thread formed on its outer circumferential surface and is configured as a worm gear, and the inner circumference of the bearing 38 has an internal thread formed thereon so as to rotate relative to the drive section 37 of the step motor 36. are movably engaged. Further, an extension part 39 is formed in the axial direction on the step motor 36 side of the bearing 38, and a groove 40 is provided in the axial direction in a part of the outer peripheral surface of the extension part 39. It engages with a protrusion 42 formed on a part of the inner peripheral surface of the provided cylindrical guide member 41 to prevent the bearing 38 from moving in the rotational direction and to enable relative movement in the axial direction. There is. When the drive part 37 is rotated by the step motor 36, the bearing 38, which is engaged with the outer periphery of the drive part 37 and is prevented from moving in the rotational direction, moves in the axial direction, and furthermore, the outer sleeve 35 attached to the bearing 38 moves in the axial direction. Move to.

When the outer sleeve 35 moves in the axial direction, the inner sleeve 31 and the cylindrical portion 34 of the timing pulley 8 rotate relative to each other, and the rotational phases of the camshaft 3 and the timing pulley 8 shift, thereby changing the valve timing. Here, when the drive section 37 of the step motor rotates forward, the outer sleeve 35 moves to the right in FIG.
If the rotation is reversed, the outer sleeve 35 moves to the left and the valve timing becomes delayed.

The valve timing is determined by the operating state of the engine, such as the engine speed Ne and the throttle opening TA that represents the load. For example, the engine speed Ne and the throttle opening TA are as shown in Figure 5. Contour VI.

In this embodiment, the contour lines as shown in FIG. One point in the table is calculated and set as the target valve timing position, and is instructed to the variable valve timing device 10.

The operation of the variable valve timing device 10 is controlled by a control circuit 11, and the control circuit 1 functions as a microcomputer. Signals from various driving state detection sensor groups are input to the control circuit 11 . The rotation speed sensor 52 generates a pulse signal according to the position of a detection piece provided on the crankshaft.

The throttle opening sensor 51 detects the movement angle of the throttle valve based on the fully closed state of the throttle valve.

The water temperature sensor 53 is provided so as to be in contact with the cooling water in the water jacket of the cylinder block.
ll is detected. Also, brake 0N-OFF sensor 17
is linked to the brake light, and the brake pedal's 0N-O
Detects FF. The LL sensor 54 detects whether the throttle valve is fully open.

A control circuit 11 processes signals from these sensor groups to form a drive signal for the step motor.

FIG. 4 schematically shows the control circuit 11 as a block diagram. The input/output boat 5o is the throttle opening sensor 5
1. Rotation speed sensor 52, water temperature sensor 53, brake 0N
- Receives signals from the OFF sensor 17 and LL sensor 54. The output port 0 is connected to the stator coil of the step motor 36 via a latch circuit 61 and a gate 62. The step motor 36 has a plurality of excitation coils,
By sequentially selecting the excitation coils to be magnetized, the excitation coils are rotated step by step in a predetermined direction. The gate 62 has the role of selecting a part of the excitation coils to be magnetized from among the plurality of excitation coils. Further, the latch circuit 61 is
It receives instructions from the microcomputer about the direction in which the step motor should rotate and the number of steps it should rotate, and has the role of outputting an opening/closing command for the gate 62 according to a predetermined sequence to execute the instructions. Note that the detailed structure of the stem motor 36 is not related to the features of the present invention, so a detailed explanation thereof will be omitted here.

The input/output port 50 and the output port 0 are connected by a bus 70 to components of the microcomputer system, such as a microprocessing unit 71 (MPU), a read-only memory 72 (ROM), and a random access memory 73 (RAM). 74 is a clock signal generator (CLOCK). The ROM 72 stores a routine that implements the valve timing switching control of this embodiment in the form of a program. MPU 71 is ROM
This program for controlling the valve timing according to the stored contents of 72 is shown as a flowchart in FIG. 6, and this flowchart will be explained step by step below.

In FIG. 6, 100 indicates the start of this routine, which is an interrupt routine executed at predetermined time intervals.

When this time interrupt request is received by the MPU 71, this interrupt routine starts to be executed, and at 101, the MPU 71 enters the RA
LL sensor 54 stored in a predetermined area of M73
The data of the LL signal from is taken in and it is determined whether the LL signal is ON. If the determination is Yes, it is determined that the vehicle is decelerating, and the process proceeds to step 120.

If the determination is NO, the process proceeds to step 102, and the valve timing is changed as follows.

In step 102, a target valve timing value V□□ is calculated from the current operating state. That is, MPU 71
are throttle opening TA data from the throttle opening sensor 51, rotation speed Ne data from the rotation speed sensor 52, and cooling water temperature TOH data from the water temperature sensor 53, which are stored in a predetermined area of the RAM 73. Incorporate RO? Contour line data as shown in FIG. 4 is stored in the I72 as a table, and the MPU 71 determines the target valve timing at that time from the reference position of the step motor, for example, based on the data of the actually measured throttle opening TA and rotational speed Ne. The rotation angle is calculated as V tt, .

Then, necessary corrections are made according to the cooling water temperature TH- at that time.

In the next step 103, the MPU 71 takes in the current rotational angular position Vpasit of the step motor stored in a predetermined area of the RAM 73, and subtracts it from the target value V5tep calculated as described above. This subtraction result is 5TEP
is the deviation of the valve timing from the target value expressed as the number of steps the step motor should rotate.

In 104, it is determined whether 5TEP-0 or not.
If it is s, it is determined that the valve timing has not deviated from the target value, and the routine proceeds to step 114 and ends. If NO, it is considered that the valve timing is deviated from the target value, and step 105 is entered.

In lO5, it is determined whether 5TEP>0. If Yes, it is determined that the step motor 36 should be corrected in the direction of forward rotation, and the rotation direction indicator flag DIR is set to “0” in step 106.
", and if No, it is determined that the step motor 36 should be corrected in the reverse direction, and the rotation direction indicator flag DIR is set to "1" in 107. In this case, the step motor 36 calculated in 103 is set to "1". Number of steps to rotate 5TE
Since P is negative, the absolute value is taken at step 108 and converted to a positive sign.

In the next step 109, it is determined whether DIR is 1 or not. If Yes, the step motor 36 should be reversed, and the reversal process is performed in step 110. The MPU 71 calculates the ON/OFF state of the gate 62 to be reversed based on the ON/OFF state of the gate 62 during the previous step execution, and writes it to the latch 61 from the output port 0. Therefore, the step motor 36 reverses by one step. If it is 109, N
If the judgment is o, normal rotation processing is performed in the same way at 111.0 Next, at 112, 5TEP minus 1 is 5T
Replaced with EP, in 113 it is determined whether 5TEP is 0 or not, and steps 109 to 112 are repeated until it becomes 0. As a result, the step motor is calculated by 103, which is the deviation between the target value and the control value. Rotate in a predetermined direction by the number of steps.

If the determination in step 101 is Yes, the process proceeds to 120, and from 120 onwards, the valve timing fixing routine is executed.

At 120, it is determined whether the vehicle speed is equal to or higher than a first predetermined speed (60 km/h). If the vehicle speed is equal to or higher than the first predetermined speed, the process proceeds to step 125, in which negative pressure is accumulated in the brake booster so that a predetermined braking force can be obtained no matter when the brake is used. Issuing a command to fix the valve timing to the advanced side of the valve timing, that is, the target value of the valve timing ■11. is replaced with a predetermined value that corresponds to the predetermined advance timing. When the routine returns to 103 and the routine is executed, the valve timing becomes the predetermined advance timing.

If it is determined in step 120 that the vehicle speed is less than the first predetermined speed, the process proceeds to step 121.

In step 121, it is determined whether a fuel cut is being executed. If a fuel cut is in progress,
Proceeding to step 125, the valve timing is fixed to the advance side as described above in order to accumulate negative pressure in the brake booster so that a predetermined braking force can be obtained whenever the brake is used.

If the fuel cut has not been executed, the process advances to step 122.

In step 122, the vehicle speed is changed to a second predetermined speed (5 km/h).
) or more. If the vehicle speed is equal to or higher than the second predetermined speed, the process proceeds to step 123.

In step 123, the brake ON-OFF sensor 17 determines whether the brake is being used.

If the brake is being used, the process proceeds to step 125, where the valve timing is fixed to the advance side in the same manner as above.

In step 125, when the valve timing of the intake valve is set to the advanced side, the intake air is no longer blown back and the intake pipe negative pressure becomes large. When the intake pipe negative pressure increases, the negative pressure within the brake booster 13 communicated with the intake pipe 5 increases.

If it is determined in step 122 that the vehicle speed is less than the second predetermined speed, it is determined that a large braking force is not necessary, and the process proceeds to step 124.

In step 124, a command is issued to fix the closing timing of the intake valve to the delayed side, that is, the target valve timing value V□0. is replaced with a predetermined value that corresponds to the predetermined timing on the delayed side.In the 0th step, 10
When the routine returns to Step 3 and the routine is executed, the valve timing becomes the predetermined delayed timing.

As explained above, in this embodiment, pressure is accumulated so that a predetermined braking force can be obtained immediately when braking at 08, so regardless of whether the brake is ON or OFF during a predetermined deceleration operation.
The structure is such that the intake pipe negative pressure is increased by advancing the closing timing of the intake valve.

Further, when the vehicle speed is extremely low or the throttle is fully closed when the vehicle is stopped, the timing of the intake valve is controlled to the delayed side, so that there is little deterioration in idling fuel efficiency.

〔Effect of the invention〕

According to the present invention, since the closing timing of the intake valve is advanced by the variable valve timing device when the vehicle is in a predetermined deceleration state, the negative pressure in the intake pipe increases, and the pressure inside the brake booster communicating with the intake pipe increases. Since the negative pressure increases, the brake application device exhibits a predetermined performance, and when using the brake, a large brake pedal force is not required, and the feel of the brake application is improved.

[Brief explanation of drawings]

FIG. 1 shows a block diagram outlining the present invention. FIG. 2 shows a configuration diagram of a variable valve timing system used in the present invention. FIG. 3 shows a configuration diagram of the variable valve timing device used in this embodiment. FIG. 4 is a block diagram showing the configuration of the control circuit of the variable valve timing device used in this embodiment. FIG. 5 is a diagram showing required valve timing characteristics for combinations of engine speed and throttle opening. FIG. 6 shows a flowchart of the control routine of the variable valve timing system according to this embodiment. Explanation of symbols 1 - Intake valve 3 - Intake camshaft 5 - Intake pipe 8 - Timing pulley 10 - Variable valve timing device 11 - Control circuit 13 - Brake booster 16 - Brake 17 - ---Brake 0N-OFF sensor Applicant Toyota Motor Corporation Figure 1 Figure 5

Claims (1)

[Scope of Claims] A variable valve timing system that variably adjusts the valve timing of an internal combustion engine equipped with a throttle valve mounted on a vehicle and is controlled to delay the closing timing of the intake valve when the load is low. A variable valve timing device that makes valve timing variable; a control means that operates the variable valve timing device according to the operating state of the engine; and a deceleration state that determines whether the running state of the vehicle is a predetermined deceleration state. and determining means, and when the deceleration state determining means determines that the vehicle is in a predetermined deceleration state, the control means controls the operation of the variable valve timing device to advance the closing timing of the intake valve. A variable valve timing system featuring: