JPH01120471A - Line pressure control method for continuously variable transmission - Google Patents

Abstract

PURPOSE:To improve feeling under low temperature by detecting oil temperature when transiting from hold mode to start mode, then increasing duty ratio for line pressure if the oil temperature is lower than a predetermined level and increasing the line pressure. CONSTITUTION:A continuously variable transmission 2 is controlled hydraulically, while a proper line pressure for holding a belt and transmitting torque, primary pressure for modifying speed change ratio and clutch pressure for coupling a hydraulic clutch 74 are ensured respectively. Oil temperature is detected through an oil temperature sensor when the hydraulic clutch 74 transits from holding mode to starting mode. If the detected oil temperature is lower than -20 deg.C, line pressure solenoid drive duty is increased to 90% so as to increase line pressure under low temperature thus enabling clutch control and improving feeling under low temperature.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a line pressure control method for a continuously variable transmission,
In particular, the present invention relates to a line pressure control method for a continuously variable transmission that increases line pressure at low temperatures, enables clutch control, improves the feeling at low temperatures, and prevents chain slip due to insufficient line pressure in drive mode.

[Conventional technology]

In a vehicle, a transmission is interposed between an internal combustion engine and drive wheels. This transmission changes the driving force and running speed of the drive wheels in accordance with the widely varying running conditions of the vehicle, thereby making full use of the performance of the internal combustion engine. The transmission has, for example, a fixed pulley part fixed to a rotating shaft and a movable bobbin part attached to the rotating shaft so as to be able to come into contact with and separate from the fixed pulley part. By decreasing or increasing the groove width formed using hydraulic pressure, the rotation radius of the belt wrapped around the pulley is decreased or increased, power is transmitted, and the gear ratio (
There is a continuously variable transmission that changes the belt ratio. As this continuously variable transmission, for example, Japanese Patent Application Laid-Open No. 57-18665
Publication No. 6, JP-A-59-43249, JP-A-59-Sho.
It is disclosed in Japanese Patent Application Laid-open No. 77159 and Japanese Patent Application Laid-Open No. 61-233256.

Further, some continuously variable transmissions have a hydraulic clutch that connects and disconnects power using hydraulic pressure. This hydraulic clutch is controlled in various control modes based on signals such as engine speed and carburetor throttle valve opening.

[Problem that the invention seeks to solve]

By the way, in the conventional line pressure control method, a problem occurs in which the line pressure does not rise as shown in FIG. 3 when the engine starts for the first time after a starting operation is performed at low or extremely low temperatures.

As a result, the clutch pressure does not reach the required value, making clutch control impossible, causing the engine speed to jump, engine torque not being transmitted to the wheels, the clutch not engaging, and eventually ending up in normal start mode. There is an inconvenience that it is not possible to migrate from .

Furthermore, as shown in Fig. 2, in line pressure control in the conventional normal start mode, the target line pressure (PLXNSP% or PL
x N) and the line pressure solenoid drive duty (DLIN) required to obtain this target line pressure.
) is read from the map (OLSCHD) and open loop control is performed to drive the solenoid at the drive duty rate. At this time, line pressure feedback control is not performed.

For this reason, by controlling the line pressure using open-loop control, it becomes impossible to correct the insufficient increase in line pressure at low temperatures, making clutch control impossible, worsening the feeling at low temperatures, and driving mode There was an inconvenience that chains slip occurred and safety decreased.

[Purpose of the invention]

Therefore, the purpose of this invention is to eliminate the above-mentioned disadvantages.
In a continuously variable transmission control method, oil temperature is detected when transitioning from hold mode to start mode, and when this oil temperature is below a predetermined temperature, line pressure duty is increased and control is performed to increase line pressure. , it is possible to increase the line pressure at low temperatures, perform clutch control, improve the feeling at low temperatures, and prevent chain slip due to insufficient line pressure in drive mode, improving safety. The object of the present invention is to realize an improved line pressure control method for a continuously variable transmission.

[Means for solving problems]

In order to achieve this object, the present invention hydraulically reduces or increases the groove width between the fixed pulley part and the movable pulley part attached to the fixed pulley part so as to be able to move toward and away from the fixed pulley part. In a continuously variable transmission control method that performs speed change control to change the gear ratio by decreasing or increasing the rotation radius of a belt wrapped around both pulleys, the oil temperature is detected when transitioning from hold mode to start mode, and this oil temperature is set to a predetermined temperature. In the following cases, the line pressure duty is increased and control is performed to increase the line pressure.

[Effect]

According to the method of the present invention, the oil temperature is detected when transitioning from the hold mode to the start mode, and when the oil temperature is below a predetermined temperature, the line pressure duty is increased and the line pressure is controlled to increase. Clutch control is enabled by increasing line pressure at low temperatures, which improves the feeling at low temperatures, and prevents chain slip due to insufficient line pressure in drive mode, improving safety.

〔Example〕

Embodiments of the present invention will be described in detail and specifically below based on the drawings.

1 to 7 show embodiments of this invention. In Figure 4.5, 2 is a continuously variable transmission, 4 is a belt,
6 is a driving side pulley, 8 is a driving side fixed bobbin part, 10 is a driving side movable pulley part, 12 is a driven side pulley, 14 is a driven side fixed pulley part, and 6 is a driven side movable pulley. It is a piece. As shown in FIG.
0, and a drive-side movable pulley piece 1 mounted on the rotating wheel 18 so as to be movable in the axial direction of the rotating shaft 18 but not rotatable.
0 exists. Further, the driven pulley 12 has the same configuration as the driving pulley 6, and includes a driven side fixed pulley piece 14 and a driven side movable pulley piece 16.

First and second housings 20.22 are respectively attached to the driving side movable pulley piece 10 and the driven side movable boolean piece 12, and first and second hydraulic chambers 24.26 are respectively formed therein. Ru. A pressing spring 28 is provided in the second hydraulic chamber 26 on the driven side to urge the driven side movable pulley piece 16 to approach the driven side fixed pulley piece 14.

An oil pump 30 is provided at the end of the rotating wheel 18. This oil pump 30 supplies oil from an oil pan 32 through an oil filter 34 to a hydraulic circuit 36.
The oil is supplied to the first and second oil pressure chambers 24.26 through first and second oil passages 38.40 that constitute the oil pressure chambers 24.26.

In the middle of the first oil passage 38, a primary pressure control valve 44, which is a speed change control valve and which constitutes the pressure control means 42, is interposed to control the primary pressure, which is the input shaft sheep pressure.

Also, the oil pump 30
The line pressure (generally 5 to 25 kg/d) is maintained at a constant pressure (1
・5～2. Constant pressure control valve 48 that controls the pressure to 0 kg/cd)
are set up consecutively. Furthermore, a first three-way solenoid valve 52 for primary pressure control is connected to the primary pressure control valve 44 via a fourth oil passage 50 .

Furthermore, a line pressure control valve 54 having a relief valve function for controlling line pressure, which is pump pressure, is connected to the second oil passage 40 via a fifth oil passage 56 . The line pressure control valve 54 is connected to a second three-way solenoid valve 60 for line pressure control via a sixth oil passage 58 .

Further, a clutch pressure control valve 62 for controlling clutch pressure is connected to the second oil passage 40 on the second hydraulic chamber 26 side via a seventh oil passage 64 than the part communicating with the line pressure control valve 54 . It is set up. This clutch pressure control valve 6
2 is connected to a third three-way solenoid valve 68 for clutch pressure control via an eighth oil passage 66.

Further, the primary pressure control valve 44, the first solenoid valve 52 for primary pressure control, the constant pressure control valve 48, the sixth oil passage 58, the second three-way solenoid valve 60 for line pressure control, and the clutch pressure control valve 62 are 9 are in communication with each other through oil passages 70.

The clutch pressure control valve 62 communicates with a hydraulic clutch 74 via a tenth oil passage 72, and also communicates with a hydraulic clutch 74 via a tenth oil passage 72.
A pressure sensor 78 is connected to the middle of the 0 oil passage 70 via an 11th oil passage 76. This pressure sensor 78
can directly detect the oil pressure when controlling the clutch pressure in hold and start modes, etc., and has a function of instructing the detected oil pressure to be set as the target clutch pressure. Furthermore, since the clutch pressure is approximately equal to the line pressure in the drive mode, it also contributes to line pressure control.

The hydraulic clutch 74 includes a piston 80, an annular spring 82, a first pressure coupler 84, a friction plate 86, a second pressure coupler 88, and the like.

In addition, a control section 90 is provided which inputs various conditions such as the throttle opening degree and engine rotation of a carburetor (not shown) of the vehicle, changes the duty rate, and performs gear change control. Solenoid valve 52, constant pressure control valve 48, second three-way solenoid valve 6 for line pressure control
0, and is configured to control the opening/closing operation of the third three-way solenoid valve 68 for clutch pressure control, and also to control the pressure sensor 78. In addition, the various signals input to the control section 90 and the functions of the input signals are as follows: (1) Shift lever position detection signal... Each range such as P, R, N, D, L, etc. The line pressure, ratio, and tarlatch control required for each range are determined by the signal, and the detection signal for the carburetor throttle opening is...
Detects the engine torque from the memory input into the program in advance, determines the target ratio or target engine speed, detects the carburetor idle position, and improves accuracy in correction and control of the carburetor throttle opening sensor. , Accelerator pedal signal: Detects the driver's intention based on the state of depression of the accelerator pedal, and determines the control method when driving or starting ■, Brake signal: Detects the driver's intention based on the state of depression of the accelerator pedal. Detects the presence and determines the control method such as clutch disengagement■, Power mode option signal...It is used as an option to make the performance of the vehicle more sporty (or more economical).

The control unit 90 detects the oil temperature using, for example, an oil temperature sensor (not shown) when the hydraulic clutch 74 shifts from the hold mode to the start mode, and when the detected oil temperature is below a predetermined temperature, It has a control function to increase duty and increase line pressure.

Specifically, when the predetermined temperature is set at 120 degrees and the oil temperature detected by the oil temperature sensor is 120 degrees or less when transitioning from the hold mode to the start mode, as shown in FIG. Line pressure solenoid drive duty (DL
IN) to 90%, and the line pressure is controlled to increase.

The above line pressure solenoid drive duty (DLIN
) to obtain sufficient target line pressure, DL I
It is necessary to select a line pressure solenoid drive duty (DL I N) that satisfies N > DT.

However, the drive duty (DT) that provides characteristics at room temperature
is not always constant, and DLIN=90%, for example, is selected in consideration of a high safety factor.

The symbols used in the line pressure control time chart in FIG. 3 will be explained in detail.

DLIN Ni line pressure solenoid drive duty NE: Engine speed NCI: Clamp input speed (vehicle speed) NCO: Clap output speed PLIN Ni line pressure PCLLI: Clutch pressure Here, the characteristics depending on the oil temperature will be explained.

In the duty solenoid of the present invention, when the drive duty is increased, the opening area of the oil i circuit is expanded, the flow rate is increased, and the solenoid pressure (PSOL) is increased.

Since the line pressure (PLIN) is an amplified version of the solenoid pressure (PSOL) in the hydraulic circuit, it has characteristics as shown in FIG. 6 at room temperature. At low temperatures, for example at extremely low temperatures of -25 degrees or lower, the viscosity of the oil increases, so that vLt becomes smaller than at room temperature even if the opening area is the same. For this reason, the change in solenoid pressure (PSOL) becomes sluggish as the drive duty increases, and the solenoid pressure (PSOL) decreases immediately after the drive duty is exceeded.
PSOL) increases. At extremely low temperatures, it has characteristics as shown in FIG.

Further, an input shaft rotation detection gear 102 is provided on the outside of the first housing 20, and a first rotation detector 104 on the input shaft side is provided near the outer periphery of the input shaft rotation detection gear 102. Further, an output shaft rotation detection gear 106 is provided outside the second housing 22, and a second rotation detector 1 on the output shaft side is provided near the outer circumference of the output shaft rotation detection gear 106.
08 is provided. Detection signals from the first rotation detector 104 and the second rotation detector 108 are output to the control section 90 and are used to determine the belt ratio of the engine rotation speed.

The hydraulic clutch 74 is provided with an output transmission gear 110, and a third rotation detection word 112 for detecting the rotation of the final output shaft is provided near the outer periphery of the output transmission gear 110. In other words, the third rotation detector 112 detects the rotation of the final output shaft directly connected to the reduction gear, the differential, the drive shaft, and the tires, and is capable of detecting the vehicle speed.

Further, the second rotation detector 108 and the third rotation detector 11
2, it is possible to detect the rotation before and after the hydraulic clutch 74, and the amount of clutch slip can be detected.

Next, the operation of this embodiment will be explained.

As shown in Fig. 4.5, the continuously variable transmission 2 has a rotating shaft 1.
An oil pump 30 located above the transmission shaft 18 operates in response to the drive of the rotating shaft 18, and the oil is pumped into the oil pan 3 at the bottom of the transmission.
2 through the oil filter 34. The line pressure, which is this pump pressure, is controlled by the line pressure control valve 54, and if the amount of leakage from the line pressure control valve 54, that is, the amount of relief from the line pressure control valve 54 is large, the line pressure will be low; If it is less, the line pressure will be higher.

The operation of the line pressure control valve 54 is controlled by a dedicated second three-way solenoid valve 60, and this second three-way tta
The line pressure control valve 54 operates following the operation of the valve 60, and the second three-way solenoid valve 60 is controlled at a duty rate of a constant frequency. That is, a duty rate of 0% means that the second three-way solenoid valve 60 does not operate at all, the output side is connected to the atmosphere, and the output oil pressure is zero. Further, when the duty rate is 100%, the second three-way solenoid valve 60 operates and the output side is connected to the atmosphere side, and the maximum output oil pressure is the same as the control pressure, and the output oil pressure is varied depending on the duty rate. Therefore, the characteristics of the second three-way solenoid valve 60 enable the line pressure control valve 54 to be operated in an analog manner, and the duty rate of the second three-way solenoid valve 60 can be arbitrarily changed to control the line pressure. be able to. Further, the operation of the second three-way solenoid valve 60 is controlled by the control section 90.

The primary pressure for speed change control is controlled by the primary pressure control valve 4.
Similarly to the line pressure control valve 54, the operation of the primary pressure control valve 44 is also controlled by a dedicated first three-way solenoid valve 52. This first three-way solenoid valve 52 is used to conduct the primary pressure to the line pressure or to conduct the primary pressure to the atmosphere side,
The belt ratio is caused to shift to the full overdrive side by conducting to the line pressure, or to the full low side by conducting to the atmosphere side.

The clutch pressure control valve 62 that controls the clutch pressure is connected to the line pressure when the maximum clutch pressure is required, and connected to the atmosphere side when the minimum clutch pressure is required. Like the line pressure control valve 54 and the primary pressure control valve 44, this clutch pressure control valve 62 also has a G4, a dedicated third
Since the operation is controlled by the three-way solenoid valve 68, the explanation will be omitted here. Clutch pressure varies within a range from minimum atmospheric pressure (zero) to maximum line pressure.

There are five patterns for clutch pressure control.

This pattern is as follows: +1), Neutral mode: When the shift position is N or P and the clutch is completely disengaged, the clutch pressure is the lowest pressure (zero) (2),
Hold mode: When the shift position is D or R and you release the throttle and have no intention of driving, or when you want to decelerate and cut off the engine torque while driving, the clutch pressure is set to a low level that the clutch contacts ( 3) Start mode: When starting or when trying to re-engage the clutch after the clutch has been disengaged, the clutch pressure is adjusted to prevent the engine from revving up and to maintain engine-generated torque (clutch input) that allows the vehicle to operate smoothly. (4), special start mode (a), when the shift lever is repeatedly used in D-N-D at a vehicle speed of 8 km/h or higher, or (b), Bb7H when driving at deceleration <vehicle speed 15km/
When the brake state is released with H, (5), drive mode... When the clutch is fully engaged after transitioning to full driving state, the clutch pressure has enough margin to withstand the engine torque. There are five high levels. (1) of this pattern is performed by a dedicated switching pulp (not shown) that is linked to shift investigation, and the other (2)
), (3), (4), and (5) are the first,
This is performed by duty rate control of the second and third three-way solenoid valves 52, 60, and 68. Particularly in the state (5), the clutch pressure control valve 62 controls the seventh oil passage 64.
The clutch pressure and the tenth oil passage 72 are communicated with each other to generate a maximum pressure, and the clutch pressure becomes the same as the line pressure.

In addition, the primary pressure control valve 44 and the line pressure control valve 5
4, and the clutch pressure control valve 62 has first, second, and third clutch pressure control valves.
They are each controlled by the output oil pressure from the three-way solenoid valves 52, 60, 68, and the control oil pressure that controls these first, second, and third three-way solenoid valves 52, 60, 68 is adjusted by the constant pressure control valve 48. constant oil pressure. This control oil pressure is always lower than the line pressure, but it is a stable and constant pressure. Control hydraulic pressure is also introduced into each control valve 44.54.62.
54.62 is being stabilized.

Next, electronic control of the continuously variable transmission 2 will be explained.

Continuously variable transmission 2 is hydraulically controlled, and controls appropriate line pressure for belt retention and torque transmission, primary pressure for changing the gear ratio, and hydraulic clutch 74 according to commands from control unit 90. Clutch pressure for reliable engagement is ensured in each case.

Next, line pressure control will be explained based on the flowchart of FIG.

When the program starts (100), the program first moves to the main program (101)L, and then it is determined whether or not it is in the normal start mode (102).

If this judgment (102) is NO, the process returns to the main program (101), and if YES, the oil temperature sensor 9
Judgment whether the oil temperature detected by 4 is below 120 degrees (1
03).

In addition, if the oil temperature exceeds 120 degrees in judgment (103), the target line pressure (PLINSP) is determined by 2/ (THR,) with the throttle opening as a variable (1
04) (see 200 in Figure 2).

Furthermore, if the oil temperature is below 120 degrees in the above judgment (103), the maximum value (PLmax) is replaced with the target line pressure (PLINSF) (105) (2 in Fig. 2).
01).

Then, the line pressure solenoid drive duty is set from the map (OLSCHD) by the target line pressure (PLrNsp) determined by the above-mentioned throttle opening and the target line pressure (PLI N S P) which replaces the maximum value (PLmax). Find (DLIN) (106) (
(see 202 in Figure 2), this line pressure solenoid drive duty (DLXN) drives the solenoid (see 202 in Figure 2).
107) and increase the line pressure to a predetermined pressure (second
(See 203 in the figure).

At this time, the line pressure solenoid drive duty (DLrs) based on the target line pressure (PLxssp) replacing the maximum value (PLmax) is set to about 90%.

As a result, when the hydraulic clutch 74 shifts from the hold mode to the start mode, the oil temperature is detected by the oil temperature sensor, and when the detected oil temperature is below the predetermined -2.5 degrees, the line pressure Solenoid drive duty (DL
IN) to 90%, the line pressure at low temperatures can be increased, clutch control becomes possible, and the feeling at low temperatures can be improved.

Furthermore, by being able to increase the line pressure at a low temperature when transitioning from the hold mode to the start mode, chain slip due to insufficient line pressure in the drive mode can be reliably prevented and safety can be improved.

Furthermore, there is no need to add new hardware, and it can be handled by simply changing the software, and most of the existing programs can be used, so the amount of memory increase in the control unit can be reduced and the configuration can be changed. It is economically advantageous because it does not become complicated and the cost can be reduced.

〔Effect of the invention〕

As is clear from the detailed description above, according to the present invention,
In the continuously variable transmission control method, the oil temperature is detected when transitioning from the hold mode to the start mode, and when this oil temperature is below a predetermined temperature, the line pressure duty is increased and the line pressure is controlled to increase. It is possible to increase the line pressure at low temperatures, enable clutch control, and improve the feeling at low temperatures.

Furthermore, by being able to increase the line pressure when the temperature is low when transitioning from the hold mode to the start mode, chain slip due to insufficient line pressure in the drive mode can be reliably prevented and safety can be improved. Furthermore, there is no need to add new hardware, and it can be handled by simply changing the software, and most of the existing programs can be used, so the configuration is not complicated and costs are low, making it economical. It is advantageous.

[Brief explanation of the drawing]

1 to 7 show embodiments of the present invention, FIG. 1 is a flowchart of a line pressure control method, FIG. 2 is a block diagram for line pressure control of a continuously variable transmission, and FIG. 3 is a belt-driven continuously variable transmission. Time chart for line pressure control of the transmission, Figure 4 is a cutaway sectional view of the main parts of the continuously variable transmission, Figure 5 is a schematic diagram of the continuously variable transmission and hydraulic circuit, Figure 6 is drive at normal temperature. A diagram showing the relationship between the duty rate, target clutch pressure, and solenoid pressure. FIG. 7 is a diagram showing the relationship between the drive duty rate, target clutch pressure, and solenoid pressure at an extremely low temperature of -25 degrees or less. In the figure, 2 is a continuously variable transmission, 4 is a belt, 6 is a driving pulley, 12 is a driven pulley, 18 is a rotating shaft, 3
0 is the oil pump, 38 is the first oil passage, 40 is the second
an oil passage, 42 a pressure control valve means, 44 a primary pressure control valve, 46 a third oil passage, 48 a constant pressure control valve;
50 is the fourth oil passage, 52 is the first oil passage for primary pressure control.
Three-way solenoid valve, 54 is a line pressure control valve, 56 is a fifth oil passage, 58 is a sixth oil passage, 60 is a second three-way solenoid valve for controlling line pressure, 62 is a clutch pressure control valve, 64 is a seventh oil passage , 66 is an eighth oil passage, 68 is a third three-way solenoid valve for clutch pressure control, 70 is a ninth oil passage, 72 is a tenth oil passage, 74 is a hydraulic clutch, 78 is a pressure sensor, and 90 is a control unit. be. Patent Applicant Suzuki Motor Co., Ltd. Patent
Applicant Mitsubishi Electric Co., Ltd. Agent Patent Attorney Yoshi Saigo Younger brother 1 Figure 2 Figure 3 Room temperature B8 Cryogenic (-25°C delivery) procedure dispute report issued January 21, 1988 Director General of the Patent Office Kunio Ogawa Tonoki 1, Indication of the case Japanese Patent Application No. 62-274746 2, Name of the invention Method for controlling line pressure of a continuously variable transmission 3, Person making the amendment Relationship with the case Patent applicant address , 300 Takatsuka, Kami Village, Hamana District, Shizuoka Prefecture
(208) Suzuki Motor Co., Ltd. Representative Suzuki
Osamu (and 1 other person) 4. Agent 101 Tit 03-292
-4411 (Representative) Address Saigo Patent Building, 2-8 Kanda Ogawamachi, Chiyoda-ku, Tokyo Name (8005) Patent Attorney Nishida Sommi/'5',
5. Date of amendment order Voluntary action
'. L-7, Contents of correction (11 Specification, page 8, line 9 [Constant pressure (1, 5 to 2.
0kg/crl) J is constant pressure (4,0~5゜0k
g/a ri J to be corrected.

Claims (1)

[Claims] 1. The width of the groove between the fixed pulley piece and the movable pulley piece attached to the fixed pulley piece so as to be removable can be decreased or increased by hydraulic pressure. In a continuously variable transmission control method that performs speed change control to change the gear ratio by decreasing or increasing the rotation radius of a belt that is wound around, the oil temperature is detected when transitioning from the hold mode to the start mode, and the oil temperature is determined to be below a predetermined temperature. 1. A line pressure control method for a continuously variable transmission, characterized in that control is performed to increase the line pressure by increasing the line pressure duty when necessary. 2. The predetermined temperature is set to -20 degrees, and when the oil temperature is below -20 degrees when transitioning from the hold mode to the start mode, the line pressure solenoid drive duty is increased to 90% to increase the line pressure. A method for controlling line pressure in a continuously variable transmission according to claim 1, wherein the line pressure is controlled by temperature.