JP2672374B2 - Power unit control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECT OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine whose valve operating characteristics are switchable,
The present invention relates to a power unit including a power transmission mechanism that transmits the engine output.

The switching of the valve operation characteristic means switching at least one of the opening / closing timing, the opening period, and the valve lift of the intake valve or the exhaust valve, and means at least one of a plurality of intake valves or exhaust valves in one cylinder. This includes setting the open period of the valve to substantially zero and switching it to the closed state.

(Prior Art) An engine in which the valve operating characteristics of the intake valve and / or the exhaust valve can be switched between a low speed valve operating characteristic suitable for a low rotation range and a high speed valve operating characteristic suitable for a high rotation range. However, Japanese Patent Publication No. 49-33289 discloses a low-speed valve operating characteristic in a region where the engine speed is lower than a predetermined value and the intake negative pressure is lower than a predetermined value (vacuum side). In other areas, it switches to high-speed valve operating characteristics. In this way, in each rotation range, it is possible to obtain a relatively high engine output torque over the entire rotation range compared with an engine in which one valve operating characteristic is dominant.

An example of such an output characteristic of the engine is shown in FIG.
In the figure, the characteristic is indicated by a line L when the low-speed valve operation characteristic is used, and the characteristic is indicated by a line H when the high-speed valve operation characteristic is used. Both characteristics intersect in terms of engine speed N _1, in the region of the engine speed Ne <N _1, the torque of the high-speed valve operating characteristic towards the torque (line A ₁₎ of the low-speed valve operating characteristic (line
B ₁ ), and in the region of Ne> N ₁ , the torque of the high-speed valve operation characteristic (line A ₂ ) is larger than the torque of the low-speed valve operation characteristic (line B ₂ ). In this case, called characteristic towards the torque is large (characteristic indicated by the line A ₁ and A ₂₎ and the high-torque valve operating characteristic, characteristic of the direction torque is small (the characteristic indicated by the line B ₁ and B ₂₎ low torque It is called the valve operating characteristic.

Further, as a power transmission mechanism of the engine, a transmission that uses hydraulic pressure to control gear shifting is disclosed in, for example, Japanese Patent Publication No. 60-4978.
There is one disclosed in Japanese Patent No. 6, which has a plurality of power transmission elements arranged between an input shaft and an output shaft. Each power transmission element is mainly composed of a drive gear arranged on the input shaft, a driven gear arranged on the output shaft or the counter shaft, and a friction element such as a hydraulic clutch for selectively operating the gear train. Thus, a combination of them constitutes one shift speed. For example,
In a shift stage in which an input shaft and a drive gear are rotatably attached, a hydraulic clutch provided between them is operated and engaged to integrally rotate them, and a driven gear engaged with the drive gear is rotated. . At this time, if the driven gear is attached integrally with the output shaft, the output shaft rotates as it is.If the driven gear is rotatable with respect to the output shaft, engage the hydraulic clutch provided between them. Rotate the output shaft.

(Problems to be Solved by the Invention) In a power unit including an engine and a transmission as described above, for example, a pressure oil for performing shift control of the transmission while the engine is operating with high torque valve operating characteristics. If the temperature rises too much, the hydraulic pressure for actuating and engaging the hydraulic clutch at the current shift stage will drop. Therefore, this fastening force is weakened, and slippage may occur in the hydraulic clutch. If the engine is operated with high torque valve operating characteristics as it is and a large rotational torque is applied to the transmission input shaft, the friction surface of the hydraulic clutch that is slipping may be worn or burned by friction heat. . Also,
Under such a high oil temperature, each sealing material or the like may be deteriorated, which may cause a decrease in hydraulic pressure due to oil leakage. These problems lead to a reduction in the durability of the transmission.

In view of the above problems, it is an object of the present invention to provide a method of controlling a power unit that enables appropriate operation even if the transmission efficiency of a power transmission mechanism such as a transmission is reduced.

B. Configuration of the Invention (Means for Solving the Problems) In order to solve the above problems, in the present invention, the hydraulic oil temperature for controlling the hydraulic operation of the clutch is equal to or higher than a predetermined value and the hydraulic pressure of the clutch is equal to the predetermined value. When it becomes lower, the valve operating characteristic is switched to the low torque valve operating characteristic.

(Operation) In such a power unit control method, while the engine is operating with the high torque valve operating characteristic, for example, the transmission oil temperature becomes high and the clutch operating oil temperature becomes a predetermined value or more,
Further, when the clutch control oil pressure becomes equal to or lower than a predetermined value, there is a high possibility that the clutch will slip, but at this time, switching to the low torque valve operating characteristic is performed, and the clutch slip is prevented. If the clutch slips, the transmission oil temperature rises, but by preventing slippage in this way, the transmission oil temperature can be lowered, and the transmission oil temperature becomes excessively high and the sealing material, etc. deteriorates. To prevent this, and improve the durability of the transmission.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a power unit controlled by the method according to the invention, which comprises an engine E having a variable valve timing and lift mechanism VT and an automatic transmission AT controlled by a hydraulic control valve CV. Be composed. Where the variable valve timing and lift mechanism VT
Is a mechanism for switching the opening / closing timing, opening period and lift amount of the intake valve of the engine E between a low speed valve operating characteristic suitable for a low rotation region and a high speed valve operating characteristic suitable for a high rotation region. Is a switching valve, as will be described later.
It is performed by supplying and discharging a predetermined hydraulic pressure by turning ON / OFF 91. In addition, the hydraulic control valve CV is an automatic transmission AT.
It is a valve that performs engagement control of the lock-up clutch, operation control of the shift clutch, and the like.

The operation of the switching valve 91 and the hydraulic control valve CV is controlled by an operation signal from the control unit CU, but the control unit CU detects the oil temperature in the transmission in order to perform the control method according to the present invention. An oil temperature signal T _OIL from the oil temperature sensor 92 and a pressure sensor 9 for detecting the hydraulic pressure of the line pressure for operating the hydraulic clutch of each shift stage.
3. Various signals such as the rotation signal Ne _I from the input shaft rotation sensor 94 that detects the rotation speed of the input shaft 61 of the transmission and the rotation signal Ne _C from the counter shaft rotation sensor 95 that detects the rotation speed of the counter shaft. The control unit CU outputs the switching signal VTS to the switching valve 91 based on these various signals.

First, the variable valve timing / lift mechanism VT will be described with reference to FIG. 2 and FIG. A pair of intake valves 1a and 1b are provided for each mechanism of the engine E, and the pair of intake valves 1a and 1b are connected to a camshaft 2 driven at a rotation ratio of 1/2 in synchronization with the rotation of the engine. A first low speed cam 3, a second low speed cam 3 'and a high speed cam 5 provided integrally, and first, second and third rocker arms pivotally supported by a rocker shaft 6 parallel to the cam shaft 2. It is opened and closed by the function of 7, 8, 9.

The camshaft 2 is rotatably disposed above the engine body, and the first low speed cam 3 is provided with one intake valve 1a.
Is provided integrally with the camshaft 2 at a position corresponding to
The second low-speed cam 3 'is provided integrally with the camshaft 2 at a position corresponding to the other intake valve 1b. The high-speed cam 5 is provided integrally with the camshaft 2 at a position corresponding to between the intake valves 1a and 1b. In addition, the first and second low speed cams 3, 3 'have high portions 3a, 3a' corresponding to the low speed operation of the engine. The high-speed cam 5 has a high-order portion 5a corresponding to high-speed operation of the engine.

The rocker shaft 6 has first to third rocker arms 7 to 9.
Are respectively pivoted, and the first and second rocker arms 7, 8
Extends to a position above each intake valve 1a, 1b. A cam slipper 10 that slides on the low-speed cam 3 is provided above the first rocker arm 7, and a cam slipper 11 that can contact the second low-speed cam 4 is provided above the second rocker arm 8.
Is provided. The intake valves 1a and 1b are urged by valve springs 16 and 17 in the valve closing direction, that is, upward.

The third rocker arm 9 includes first and second rocker arms.
The rocker shaft 6 pivots between 7,8. The third rocker arm 9 is connected to both intake valves 1a, 1
A cam slipper that extends slightly toward the b side and that is in sliding contact with the high-speed cam 5 is provided above the cam slipper.

As shown in FIG. 3, first to third rocker arms 7, 8, 9
Are connected to each other, and a connecting means 21 capable of switching between a state in which the relative angular displacement can be performed and a state in which the rocker arms 7 to 9 are integrally connected is provided by the first and second rocker arms 7. , 8,9.

The connecting means 21 includes a first piston 22 movable between a position for connecting the first and third rocker arms 7 and 9 and a position for releasing the connection, and the third and second rocker arms 9 and 8.
A second piston 23 movable between a position for connecting and a position for releasing the connection, and first and second pistons 22 and 2
3 and a stopper 2 for moving the first and second pistons 22 and 23 to the uncoupling position side.
And a spring 25 for urging the spring 4.

The movement of the first and second pistons 22 and 23 is performed by hydraulic pressure supplied to the hydraulic chamber 29 through the oil passages 31, 32 and 30 in accordance with the operation of the solenoid valve 91.

Such a variable valve timing / lift mechanism is disclosed in detail, for example, in Japanese Patent Application Laid-Open No. 62-121811.

Next, the operation of the variable valve timing / lift mechanism VT configured as described above will be described.

During low-speed operation of the engine E, the solenoid valve 91 is
OFF, the communication between the oil passage 31 and the hydraulic pressure source (not shown) is cut off as shown in FIG. 3, the hydraulic pressure is not supplied to the hydraulic chamber 29 of the connection switching means 21, and the stopper 24 is 25 pushes the third rocker arm 9 side. Therefore, each rocker arm 7, 8, 9 can be displaced independently.

In such a disconnected state of the connection switching means 21,
The rotation of the camshaft 2 causes the first rocker arm 7 to rotate.
Swings according to sliding contact with the first low-speed cam 3, and the second rocker arm 8 swings according to sliding contact with the second low-speed cam 3 '. Therefore, both intake valves 1a, 1b are opened and closed by the first and second low speed cams 3, 3 '. At this time, the third rocker arm 9 swings by sliding contact with the high-speed cam 5, but the swinging operation has no influence on the operation of the intake valves 1a and 1b.

In this way, when the engine E is running at low speed,
As shown by a broken line 3 and an alternate long and short dash line 3 'in the figure, one intake valve 1a opens and closes at a timing and a lift amount corresponding to the shape of the first low speed cam 3, and the other intake valve 1b opens and closes the second low speed cam 3b. The opening and closing operation is performed at a timing and a lift amount according to the shape of the cam 3 '. Therefore, an air-fuel mixture inflow speed suitable for low-speed operation can be obtained, fuel consumption can be reduced and kicking can be prevented, and optimal low-speed operation can be performed.

In order to obtain an air-fuel mixture inflow speed suitable for low-speed operation, for example, as shown in FIG. 5B, the second low-speed cam 3 '
The high-order portion 3a 'of the intake valve 1b may be made extremely small during low-speed operation by lowering the high-order portion 3a'. Alternatively, the valve 1b may not be opened at all to create a valve rest state.

When the engine E operates at high speed, the solenoid valve
91 is ON, and as shown in FIG.
The hydraulic pressure source (not shown) and the oil passage 31 communicate with each other, and the operating hydraulic pressure is supplied to the hydraulic chamber 29 of the connection switching means 21. As a result, as shown in FIG. 4, the first and second pistons 22 and 2 are moved until the stopper 24 contacts the regulating step 36.
3 moves, the first piston 22 connects the first and third rocker arms 7 and 9, and the second piston 23 connects the third and second rocker arms 9 and 8.

In this manner, when the first to third rocker arms 7, 8, 9 are connected to each other by the connection switching means 21, the swing amount of the third rocker arm 9 sliding on the high-speed cam 5 is the largest. The first and second rocker arms 7 and 8 swing together with the third rocker arm 9. Therefore, during high-speed operation of the engine E, as shown by the solid line 5 in FIG. 5A, the two intake valves 1a and 1b open and close at timings and lifts corresponding to the shape of the high-speed cam 5. In this case, the timing and the lift amount are larger than those at the time of low-speed operation, so that intake air suitable for high-speed operation can be obtained, and the engine output can be improved.

In the above operation, the opening / closing timing and the lift amount of the intake valves 1a, 1b based on the first and second low speed cams 3, 3 'are referred to as low speed valve operating characteristics.
The opening / closing timing and lift amount of the intake valves 1a and 1b based on the above are referred to as high-speed valve operating characteristics. Both valve operating characteristics are used separately in a low speed operation region and a high speed operation region,
The relationship between the engine output torque and the engine speed at this time is as shown in FIG. As described above, in this figure, the characteristic in the low-speed valve operation characteristic operation is indicated by the line L, and the characteristic in the high-speed valve operation characteristic operation is indicated by the line H.
The characteristics indicated by A ₁ and A ₂ are the high torque valve operating characteristics, and the line B
_1, the characteristic indicated by B ₂ is a low-torque valve operating characteristic.

Next, the automatic transmission AT will be described with reference to FIG.

The automatic transmission AT is composed of a torque converter 40 and the transmission mechanism 50. The torque converter 40 is a pump 46a connected to the engine output shaft E _OP, the output shaft (transmission mechanism input shaft) 6
Turbine 46b connected to 1 and stator 46 fixedly held
c, and further includes a lock-up clutch 47 capable of engaging and disengaging the pump 46a and the turbine 46b.

The transmission mechanism 50 has an input shaft 61 integral with the torque converter output shaft, a counter shaft 62 and an output shaft 63 parallel to the input shaft 61. Between the input shaft 61 and the counter shaft 62, five sets of gear trains meshing with each other, that is, first speed gear trains 51a, 51
b 2nd gear train 52a, 52b, 3rd gear train 53a, 53b, 4th gear train 5
4a, 54b and reverse gear trains 55a, 55b, 55C are arranged. Hydraulic clutches 64 to 68 for selecting each gear train are provided as drive gears or driven gears of each gear train. Power transmission by either gear train by selectively operating these hydraulic clutches 64 to 68 The route is selectively switched and the speed is changed.

Output gear trains 59a and 59b are provided between the counter shaft 62 and the output shaft 63, and the power shifted as described above is transmitted to the output shaft via the output gear trains 59a and 59b. .

The first-speed driven gear 51b and the second-speed driven gear 52b include:
One-way clutches 56 and 57 are mounted, and an emblem clutch 69 for holding these one-way clutches 56 and 57 in a locked state is provided.

The operation control of the lock-up clutch 47 and the operation control of each of the clutches 64 to 69 of the transmission mechanism 50 in the automatic transmission AT having the above configuration are performed by the control valve CV shown in FIG.

The control method according to the present invention in the power unit configured as described above will be described with reference to the control flow of FIG.

While the engine is operating at high torque valve operating characteristics HTVT,
First, in step S1, the transmission oil temperature T _OIL , the line pressure P _L , the transmission input shaft speed Ne _I, and the transmission counter shaft speed Ne _C are detected by the sensors shown in FIG. Next, in step S2, it is determined whether the oil temperature T _OIL is higher than a predetermined temperature T _{L. If the} temperature is higher than the predetermined temperature T _{L, the} seal material used in the transmission may deteriorate, and , It may cause a drop in the oil pressure. Therefore, the process proceeds to step S3, and it is determined whether or not the line pressure P _L for operating the hydraulic clutch (the first speed clutch 64, the second speed clutch 65, etc. in FIG. 7) is lower than the predetermined pressure P _LL . Here, if the line pressure P _L is low, the operating hydraulic pressure that should have completely engaged the currently selected hydraulic clutch decreases, so that the hydraulic clutch slips. Therefore, it is possible that the friction surface of the hydraulic clutch is worn or burned by friction heat. Therefore, the process proceeds to step S6 and the transmission input shaft 61
In order to reduce this rotation torque and suppress this slip, the engine is switched from operation with the high torque valve operation characteristic HTVT to operation with the low torque valve operation characteristic LTVT. At this time,
As shown in FIG. 6, if the engine speed Ne <N ₁ ,
As shown in FIG. 4, the connection switching means 21 is set to the connected state, and Ne>
If it is N ₁ , the connection is released as shown in FIG.

Such slippage is caused by the lockup clutch 47 shown in FIG.
May occur, and in that case, the same control as above is performed.

Further, in the case it is determined that the oil temperature T _OIL is less than the predetermined temperature T _L in step S2, the oil temperature T _OIL is the predetermined temperature T _L in step S3
Although it is higher, when it is determined that the line pressure P _L is equal to or lower than the predetermined pressure P _LL , it is not necessary to immediately switch to the low torque valve operating characteristic. However, there is a possibility that the hydraulic clutch slips for some reason, and in this case as well, the hydraulic clutch is damaged as described above, so it is desirable to switch the engine to the operation with the low torque valve operating characteristic. Therefore, first, in step S4, the current state is a state in which the hydraulic clutch is slipping because the gear is shifting or the lockup clutch 47 is controlled to slide according to the driving situation, so-called slip control. Determine if there is. When the slip control is not being performed, that is, when it is determined that the slip control is in the normal control state, it is determined in step S5 whether or not the slip e _CL is larger than the predetermined amount e _CLL . Here, the hydraulic clutch of each gear (the first clutch in FIG.
The slip e _{CL of the} high speed clutch 64, the second speed clutch 65, etc., is used to drive the shift speed selected at that time using the input shaft speed Ne _I and the counter shaft speed Ne _C detected in step S1. If the gear ratio of the gear and driven gear is k, (Ne _I −k
It is understood based on the value calculated in Ne _C ). Also, the slip of the lockup clutch 47 is caused by the engine output shaft and Ne above.
It is grasped based on the difference of _I. When it is determined in step S5 that e _CL > e _CLL , the process proceeds to step S6, and the engine is switched from the operation with the high torque valve operation characteristic HTVT to the operation with the low torque valve operation characteristic LTVT.

When it is determined in step S4 that the slip control is being performed and when it is determined in step S5 that e _CL <e _CLL , the process proceeds to step S16, and the high torque valve operating characteristic HTVT is maintained.

Thus, in the control method of the present invention, when the transmission oil temperature T _OIL becomes higher than the predetermined temperature T _L while the engine is operating at the high torque valve operating characteristic HTVT, the line pressure P _L becomes equal to or lower than the predetermined pressure P _L. even if there when and fluid temperature T _OIL is lower than the predetermined temperature T _L or the line pressure P _L is the predetermined pressure P _L or decreased,
When a slip e _CL of a predetermined amount e _CLL or more of a friction element such as a hydraulic clutch or lock-up clutch is detected, the engine is switched from the operation with the high torque valve operation characteristic HTVT to the operation with the low torque valve operation characteristic LTVT, Reduce the engine output torque. Therefore, the rotation torque of the transmission input shaft is reduced, slippage of the friction element can be prevented, and the oil temperature T _OIL
Therefore, it is possible to prevent deterioration of the sealing material and the like, and thus improve the durability of the automatic transmission AT.

C. As described above, in the power unit control method of the present invention, when the engine is operating with high torque valve operating characteristics, when the clutch operating oil temperature is equal to or higher than a predetermined value and the clutch control hydraulic pressure is equal to or lower than a predetermined value, Although there is a high possibility that slippage will occur in the clutch, at this time, switching to the low torque valve operating characteristic is performed, and slippage of the clutch is prevented, so the transmission oil temperature rise caused by slippage of the clutch is prevented. It is possible to prevent the deterioration of the sealing material and the like due to the excessively high temperature of the transmission oil, which in turn can improve the durability of the transmission.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the configuration of a power unit for using the method for controlling a power unit according to the present invention, and FIGS. 2, 3, and 4 are variable valves of an engine that constitute the power unit. 5A and 5B are cross-sectional views showing a timing / lift mechanism, FIGS. 5A and 5B are graphs showing changes in valve timing and lift amount of the variable valve timing / lift mechanism, and FIG. 6 is a graph showing the variable valve timing / lift mechanism. FIG. 7 is a graph showing the relationship between engine output torque and engine speed according to FIG. 7, FIG. 7 is a schematic diagram showing the configuration of an automatic transmission that constitutes the power unit, and FIG. 8 is a control flow of the control method for the power unit. Is. 1a, 1b …… Intake valve 3,3 ′ …… Low speed cam, 5 …… High speed cam 21 …… Connection switching means 40 …… Torque converter, 61 …… Input shaft 62 …… Counter shaft, 92 …… Oil Temperature sensor 93 …… Pressure sensor 94,95 …… Rotation sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Hanaoka 1-4-1, Chuo, Wako-shi, Saitama Inside Honda R & D Co., Ltd. (72) Inventor Junichi Miyake 1-1-4, Chuo, Wako-shi, Saitama Incorporated in Honda R & D Co., Ltd. (72) Inventor Masao Kubotera 1-4-1, Chuo, Wako, Saitama In R & D Co., Ltd. in Honda (56) Reference JP 61-119435 (JP, A) JP HEI 3 -33439 (JP, A) JP-B-49-33289 (JP, B2)

Claims (1)

(57) [Claims] 1. A power unit comprising an engine in which valve operation characteristics of at least one of an intake valve and an exhaust valve are switchable, and a power transmission mechanism for transmitting the output of the engine via a hydraulic clutch. When the temperature of the hydraulic oil for performing the hydraulic pressure control of the clutch is equal to or higher than a predetermined value and the hydraulic pressure of the clutch is lower than the predetermined value, the valve operating characteristic is set to generate a torque lower than the output torque at that time. A method of controlling a power unit, characterized by switching to a valve operating characteristic that is set.