JP3116616B2 - Hydraulic control device for belt-type continuously variable transmission for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control apparatus for a belt type continuously variable transmission for a vehicle.

[0002]

2. Description of the Related Art A belt-type continuously variable transmission for a vehicle generally includes:
A pair of variable pulleys respectively provided on the primary side rotary shaft and the secondary side rotary shaft, a transmission belt wound around the pair of variable pulleys to transmit power, and an effective diameter of the pair of variable pulleys are respectively changed. And a pair of primary hydraulic actuators and secondary hydraulic actuators. Such a hydraulic control device for a belt-type continuously variable transmission for a vehicle is actually detected as described in, for example, Japanese Patent Application Laid-Open No. 3-181662 and Japanese Patent Application No. 4-73418. By adjusting the pressure regulating valve so that the tension control pressure coincides with the target pressure, the tension of the transmission belt, that is, the squeezing pressure on the transmission belt is reduced as much as possible within a range where the transmission belt does not slip. ,
Optimum control is performed according to the speed ratio and input torque of the belt-type continuously variable transmission.

[0003]

In the above-described hydraulic control apparatus for a continuously variable transmission for a vehicle, the pressure regulating valve is configured to generate a basic hydraulic pressure exceeding a theoretical value of the tension control pressure. It has an oil chamber that receives the control oil pressure output from the linear solenoid valve in order to generate an optimal tension control pressure close to its theoretical value, and receives a control oil pressure of a size corresponding to the amount of decrease from the basic oil pressure. As a result, the tension control pressure is output. Thereby, while the optimal tension control pressure is obtained, at the time of failure such as disconnection of the linear solenoid valve, the basic hydraulic pressure is output as it is as the tension control pressure, and the tension control pressure is set to the maximum value. The transmission belt does not slip despite the failure, and power transmission and running of the vehicle are enabled.

However, when the control hydraulic pressure generating means such as the disconnection of the linear solenoid valve of the conventional hydraulic control device fails as described above, the power is transmitted because the tension control pressure is set to its maximum value. However, there is a disadvantage that the load on the power transmission belt becomes larger than the optimum value. In particular, at the time of high-speed running with a large engine load, the load on the power transmission belt may be excessively large and its durability may be impaired.

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent the load on the transmission belt from being excessively increased even when the control oil pressure generating means fails, and to improve durability. An object of the present invention is to provide a hydraulic control device for a belt-type continuously variable transmission that does not impair.

[0006]

A first aspect of the present invention for achieving the above object is to provide an endless ring.
Thickness direction in contact with the hoop and the inner peripheral surface of the hoop
And a large number of V-blocks
A pair of variable pulleys around which a compression type transmission belt is wound and the effective diameter is variable, and a pair of hydraulic cylinders for applying a clamping force to the pair of variable pulleys, and the thrust of the pair of hydraulic cylinders In a vehicle belt-type continuously variable transmission in which the gear ratio is changed steplessly by changing the ratio, a pressure regulating valve that adjusts a tension control pressure based on an engine load and a gear ratio of the belt-type continuously variable transmission is provided. A hydraulic control device for optimally controlling the tension of the transmission belt by the tension control pressure, wherein (1) an abnormal tension control pressure state detection for detecting an abnormal state of the tension control pressure regulated by the pressure regulating valve Means, and (2) when the tension control pressure abnormal state detecting means detects a state in which the tension control pressure is abnormal, a margin pressure up to the breaking tension on the minimum speed ratio side.
In relation to the reduction of the maximum transmission ratio, the bending of the hoop
In connection with the increase of stress, the transmission belt
Variable range of the speed ratio of the continuously variable transmission so that
And a transmission belt load reduction means for reducing the load on the transmission belt by limiting the load.

[0007]

In this way, when the tension control pressure abnormal state detecting means detects a state in which the clamping pressure of the power transmission belt becomes abnormally high, the power transmission belt load lowering means detects the minimum. On the gear ratio side, up to the breaking tension
In connection with the reduction of the margin pressure, the hoop is
Excessive tension in the power transmission belt
It is possible to change the speed ratio of the continuously variable transmission so that
By limiting the performance range, the clamping force of the power transmission belt is reduced. Therefore, according to the present invention, the control oil
Even if the pressure generating means fails, the load on the
It will not be large and will not impair the durability of the transmission belt.
No.

[0008]

[Second means for solving the problem] In addition,
The gist of the second invention to be achieved is that the transmission
A pair of variable pulleys with a variable effective diameter
And a pair of variable pulleys for applying a squeezing force to the variable pulleys.
And a pair of hydraulic cylinders.
Gear ratio changes steplessly by changing the thrust ratio
In a belt-type continuously variable transmission for vehicles,
Based on the gear load and the gear ratio of the belt-type continuously variable transmission.
Pressure control valve to adjust the tension control pressure
Hydraulic control that optimally controls the tension of the transmission belt by pressure
(1) tension regulated by the pressure regulating valve
Tension control pressure abnormal state detection means for detecting abnormal control pressure
And (2) the tension control pressure abnormal state detecting means.
If a state where the tension control pressure is abnormal is detected,
By reducing the input torque of the continuously variable transmission,
Transmission belt load reduction means for reducing the load on the transmission belt
And to include.

[Action and effect of the second invention] In this way, the tension
The clamping pressure of the power transmission belt is
If a constantly high state is detected, the transmission belt
Load reduction means to reduce the input torque of the continuously variable transmission
As a result, the clamping pressure of the transmission belt is reduced.
You. Therefore, according to the present invention, the control oil pressure
Even at the time of failure, the load on the transmission belt does not become excessive,
There is no loss in the durability of the transmission belt.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. In FIG. 2, the power of the engine 10 is
Fluid coupling with lock-up clutch 12, belt-type continuously variable transmission (hereinafter referred to as CVT) 14, forward / reverse switching device 1
6, via an intermediate gear device 18 and a differential gear device 20 to drive wheels 24 connected to a drive shaft 22.

The fluid coupling 12 includes a pump impeller 28 connected to a crankshaft 26 of the engine 10 and a CVT 1
4; a turbine impeller 32 fixed to the input shaft 30 via the damper 34; a lock-up clutch 36 fixed to the input shaft 30 via a damper 34; A release side oil chamber 35 is provided. The inside of the fluid coupling 12 is always filled with hydraulic oil. For example, when the vehicle speed becomes equal to or higher than a predetermined value, or when the rotation speed difference between the pump impeller 28 and the turbine impeller 32 becomes equal to or lower than the predetermined value, the engagement side oil is set. When the hydraulic oil is supplied to the chamber 33 and the hydraulic oil flows out from the release-side oil chamber 35, the lock-up clutch 36 is engaged, and the crankshaft 26 and the input shaft 30 are directly connected. Conversely, when the vehicle speed becomes equal to or less than a predetermined value, or when the rotational speed difference becomes equal to or more than a predetermined value, hydraulic oil is supplied to the release-side oil chamber 35 and hydraulic oil flows out of the engagement-side oil chamber 33. As a result, the lock-up clutch 36 is released.

The CVT 14 includes variable pulleys 40 and 42 of the same diameter provided on its input shaft 30 and output shaft 38, respectively, and a transmission belt 44 wound around the variable pulleys 40 and 42. Variable pulley 40
And 42 are fixed rotating bodies 46 and 48 fixed to the input shaft 30 and the output shaft 38, respectively, and a movable member provided on the input shaft 30 and the output shaft 38 so as to be movable in the axial direction and non-rotatable relative to the axis. Rotating bodies 50 and 52
The movable grooves 50 and 52 are moved by the primary hydraulic cylinder 54 and the secondary hydraulic cylinder 56 functioning as hydraulic actuators, thereby changing the V-groove width, that is, the hanging diameter (effective diameter) of the transmission belt 44. Then, the gear ratio γ of the CVT 14 (= the rotation speed N _in of the input shaft 30 / the rotation speed N _out of the output shaft 38) is changed. Since the variable pulleys 40 and 42 have the same diameter, the hydraulic cylinders 54 and 56 have the same pressure receiving area. Normally, the pressure of the hydraulic cylinders 54 and 56 located on the driven side is operated exclusively to maintain the tension of the transmission belt 44 optimally.

The forward / reverse switching device 16 is a well-known double pinion type planetary gear mechanism, and a pair of planetary gears 62 and 64 rotatably supported by a carrier 60 fixed to an output shaft 58 and meshing with each other. A sun gear 66 fixed to the input shaft (output shaft of the CVT 14) 38 of the forward / reverse switching device 16 and meshing with the planetary gear 62 on the inner peripheral side; and a ring gear 6 meshing with the planetary gear 64 on the outer peripheral side.
8, a reverse brake 70 for stopping rotation of the ring gear 68, the carrier 60 and the forward / reverse switching device 16
And a forward clutch 72 for connecting the input shaft 38 to the input shaft 38. Reverse brake 70 and forward clutch 72
Is a friction engagement device of a type operated by hydraulic pressure, and when they are not engaged with each other, the forward / reverse switching device 1
6 is set to a neutral state, and power transmission is interrupted. But,
When the forward clutch 72 is engaged, the output shaft 38 of the CVT 14 and the output shaft 58 of the forward / reverse switching device 16 are directly connected, and power in the forward direction of the vehicle is transmitted. When the reverse brake 70 is engaged, the rotation direction is reversed between the output shaft 38 of the CVT 14 and the output shaft 58 of the forward / reverse switching device 16, so that power in the vehicle reverse direction is transmitted.

FIG. 3 shows in detail the main part of the hydraulic control circuit of FIG. 2 for controlling the vehicle power transmission. The other parts are the same as those described in, for example, Japanese Patent Application Laid-Open No. 2-212658.

In FIG. 3, an oil pump 74 constitutes a hydraulic source of the present hydraulic control circuit,
By being integrally connected to the second pump impeller 28, it is constantly driven to rotate by the crankshaft 26. The oil pump 74 sucks in the working oil returned to the oil tank (not shown) through the strainer 76, and sucks the working oil returned through the return oil passage 78 and feeds it to the first line oil passage 80. . In this embodiment, the operating oil in the first line oil passage 80 is leaked to the return oil passage 78 and the lock-up clutch pressure oil passage 92 by the relief type first pressure regulating valve 100, so that the first line oil passage 80 The first line hydraulic pressure P ₁₁ is adjusted. In addition, the second line oil pressure P _l2 in the second line oil passage 82 is adjusted by reducing the first line oil pressure P _l1 by the second pressure reducing valve 102 of the pressure reducing valve type. The second line hydraulic pressure P _l2 is adjusted to control the tension of the power transmission belt 44, that is, the clamping force applied to the power transmission belt 44, and thus corresponds to the belt tension control pressure of the present embodiment.

First, the second pressure regulating valve 102 will be described. The second pressure regulating valve 102 includes a spool valve element 110 that opens and closes between the first line oil passage 80 and the second line oil passage 82, a spring seat 112, a return spring 114, and a plunger 116. A first land 118, a second land 120, and a third land 122 having larger diameters are sequentially formed on the shaft end of the spool valve element 110 in this order. Second
Between the land 120 and the third land 122, there is provided a chamber 126 in which the second line oil pressure _Pl2 is introduced as a feedback pressure through the throttle 124.
10 is urged in the valve closing direction by the second line oil pressure _Pl2 . On the end face side of the first land 118 of the spool valve element 110, there is provided a chamber 130 into which a later-described speed ratio pressure Pr is introduced via a throttle 128, and the spool valve element 110 is closed by the speed ratio pressure Pr. It is designed to be biased in the valve direction. In the second pressure regulating valve 102, the urging force in the valve opening direction of the return spring 114 is applied to the spool valve element 110 via the spring seat 112. Further, the end face of the plunger 116 is provided with a chamber 132 for applying a throttle pressure P _th below, so the spool valve element 110 is urged in the valve opening direction by the throttle pressure P _th I have. Then, the first land 118 and the second land 12 of the spool valve 110
0, a control oil pressure P output from a linear valve 180 described later to make the tension of the transmission belt 44 an optimum value.
A chamber 136 into which _solL is introduced is provided, and the spool valve element 110 is urged in the valve closing direction by the speed ratio pressure Pr.

Accordingly, the pressure receiving area of the first land 118 is A ₁ , the area of the cross section of the second land 120 is A ₂ , the area of the cross section of the third land 122 is A ₃ , and the pressure receiving area of the land 117 of the plunger 116 is A. ₄ , return spring 11
Assuming that the urging force of No. 4 is W, the spool valve element 110 is balanced at a position where the following equation 1 holds. That is, when the spool valve element 110 is moved according to the equation 1, the hydraulic oil in the first line oil passage 80 guided to the port 134a flows into the second line oil passage 82 via the port 134b. The state and the state in which the hydraulic oil in the second line oil passage 82 led to the port 134b flows to the drain port 134c communicating with the drain are repeated, and the second line oil pressure _P12 is generated. . The second line oil passage 82 is a relatively closed system, and the second pressure regulating valve 102 is shown in FIG. 4 by reducing the first line oil pressure _P11, which is a relatively high oil pressure as described above. It creates pressure.

[0017]

[Number 1] P _l2 = _{[A 4 · P th + W-} A 1 · P r - (A 2 -A 1) P solL ] / (A ₃ -A ₂₎

In FIG. 4, when a failure such as disconnection of the linear valve 180 occurs, the control oil pressure P _solL output from the failure is output.
Is zero (atmospheric pressure), the second line oil pressure P _l2 , which is adjusted according to the above equation 1, that is, the basic oil pressure P _mec is shown by a solid line. In addition, a linear valve 1 driven by an electronic control unit 200 described below to obtain the optimum value _Popt.
Based on the control oil pressure P _solL output from 80, the second line oil pressure P _{l2 adjusted} in accordance with the above equation 1 is indicated by a broken line. The second line pressure P _l2 shown by broken lines in which is generated by being allowed to step down in accordance with the value of the control hydraulic pressure P _Soll from the basic hydraulic P _mec.

The first pressure regulating valve 100 includes a spool valve 14
0, spring seat 142, return spring 14
4, the first plunger 146, and the second plunger 14 having the same diameter as the second land 155 of the first plunger 146.
8 are provided. The spool valve 140 has a first
It opens and closes between a port 150a communicating with the line oil passage 80 and the drain port 150b or 150c. A first line oil pressure P _l1 as feedback pressure acts on an end face of the first land 152 via a throttle 151. A first chamber 153 is provided, and the spool valve element 140 is urged in the valve opening direction by the first line oil pressure _P11 . A chamber 156 for guiding the throttle pressure P _th is provided between the first land 154 and the second land 155 of the first plunger 146 provided coaxially with the spool valve element 140. 155
A chamber 1 for guiding the hydraulic pressure Pin _{in the} primary hydraulic cylinder 54 through an oil passage 161 between the first plunger 148 and the second plunger 148.
The second plunger 148 is provided with a chamber 158 for guiding the second line oil pressure _P12 . The urging force of the return spring 144 is applied to the spool valve 14 via the spring seat 142.
0 in the valve closing direction.
0, the pressure receiving area of the first land 152 is A ₅ , the cross-sectional area of the first land 154 of the first plunger 146 is A ₆ , the cross-sectional area of the second land 155 and the second plunger 148 is A ₇ ,
Assuming that the urging force of the return spring 144 is W, the spool valve element 140 is balanced at a position where the following equation 2 is satisfied, and the first line hydraulic pressure P _l1 is adjusted.

[0020]

[ _Equation 2] P _l1 = [(P _in or P _l2 ) · A ₇ + P _th (A ₆ −A ₇ ) + W] / A ₅

[0021] In the first pressure regulating valve 100, the hydraulic pressure P _in the in the primary-side hydraulic cylinder 54 and the second line pressure P _l2 (hydraulic P _out in P _l2 = secondary hydraulic cylinder 56 in the steady state)
If the pressure is higher than the first pressure, the first plunger 146 and the second plunger 148 are separated from each other, and the thrust by the hydraulic pressure Pin _{in the} primary hydraulic cylinder 54 acts on the spool valve 140 in the valve closing direction. in the side hydraulic cylinder 54 hydraulic pressure P _in
Is lower than the second line oil pressure P _l2 , the first plunger 146 and the second plunger 148 come into contact with each other, so that the thrust by the second line oil pressure P _l2 acting on the end face of the second plunger 148 Acts in the valve closing direction of the spool valve element 140. That is, the primary hydraulic cylinder 54
The second plunger 148 which receives the inner pressure P _in the second line pressure P _l2 is of exerting an action force based on the hydraulic pressure of the higher of those pressure in the closing direction of the spool 140. The first land 15 of the spool valve element 140
The chamber 160 provided between the second land 159 and the second land 159 is open to the drain.

The throttle pressure P _th is a signal pressure indicating the throttle valve opening θ _th as shown in FIG. 5, and is a throttle opening detecting valve (not shown) which is operated in relation to the rotational position of the throttle cam. Have been generated from. Further, the gear ratio pressure P _r is the gear ratio of CVT14 as shown in FIG. 6 gamma
, Which is generated from a speed ratio detection valve (not shown) which is operated in relation to the axial position of the movable rotator 50 or 52. The transmission ratio detecting valve, since those which generate speed ratio pressure P _r by changing the relief amount of hydraulic oil in the second line pressure P _l2 supplied through the orifice from the second line oil passage 82, shift while specific pressure P _r is being restricted to be a second line pressure P _l2 or more values, the second pressure regulating valve 10 that operates in accordance with equation 1
The with decreasing 2 in speed ratio pressure P _r 2 line pressure P _l2
Increase. Therefore, the speed ratio pressure P _r becomes equal to the second line pressure P _l2 increases to a predetermined value, is constant with saturated Both later. Figure 4 straight lines show the change characteristics of the P _mec (maximum value of the second line pressure P _l2) basic hydraulic pressure pressure is regulated according to equation 1 in relation to the speed ratio pressure P _r in the second pressure regulating valve 102 . The second pressure regulating valve 1
The basic hydraulic pressure P _mec obtained by the valve mechanism 02 is a value that is mechanically determined in relation to the spool valve element 110 of the second pressure regulating valve 102, the pressure receiving area of the plunger 116, and the like, and is sufficiently higher than the ideal pressure P _opt. It is set high.

The first line pressure P _l1 regulated by the first pressure regulating valve 100 and the second line pressure P _l2 regulated by the second pressure regulating valve 102 are used to adjust the speed ratio γ of the CVT 14. It is supplied to one and the other of the primary hydraulic cylinder 54 and the secondary hydraulic cylinder 56 by a shift control valve device (not shown) composed of a shift direction switching valve and a flow control valve. Also, the second line hydraulic pressure P _l2
Are made to act on the secondary hydraulic cylinder 56 via a throttle.

The linear valve 180 generates the output signal pressure P _solL by using the modulator pressure P _mo regulated to a constant value from the first line oil pressure P _l1 by a pressure regulating valve (not shown) as a _source pressure. , Valve body 182
A spool valve element 186 slidably fitted in the cylinder bore 184 of FIG. 1, a linear solenoid 188 excited by a drive signal (control signal value) D supplied from the electronic control unit 200, and an excitation of the linear solenoid 188 A core 190 for urging the spool valve element 186 to the boost side based on the electromagnetic force generated in relation to the state, a spring 192 for urging the spool valve element 186 to the step-down side, and a spool valve element 186 to the step-down side A feedback oil chamber 194 into which the output signal pressure P _solL is guided for _energizing is provided. The spool valve element 186 is operated so as to move to a position where the urging force applied from the core 190 to the pressure-increase side and the urging force applied from the spring 192 to the pressure-decrease side move to a position where it is balanced as shown in FIG. The control oil pressure P _solL is output based on the drive signal D supplied from the electronic control device 200 in accordance with the output characteristics shown in FIG. The control oil pressure P _solL output in this manner is supplied from the output port 196 of the linear valve 180 to the chamber 136 of the second pressure regulating valve 102, so that the control oil pressure P _solL is reduced from the basic oil pressure P _mec to a predetermined reduction pressure P _down.
The target pressure _Popt lowered only by this is output from the second pressure regulating valve 102 as the second line oil pressure _P12 .

The drive signal D for the linear valve 180 is a current that is continuously changed. However, in order to remove the hysteresis of the linear valve 180 and stabilize the operation, an alternating current having a frequency of, for example, about 300 Hz is superimposed. May be forced.

Returning to FIG. 2, the electronic control unit 200
The shift direction switching is performed so that the target input shaft rotation speed N _in決定 determined based on the actual throttle valve opening θ _th and the vehicle speed V from a previously stored relationship (not shown) matches the actual input shaft rotation speed N _in. A third solenoid valve 2 that drives a first solenoid valve 202 and a second solenoid valve 204 that control a valve and a flow control valve, while controlling a clutch control valve (not shown);
06, a fourth solenoid valve 208 for controlling a relay valve, and a CV by selectively driving the linear valve 180.
Speed ratio of T14 gamma, engagement of the lock-up clutch 36 of the fluid coupling 12, as well as controls the increase or decrease in the second line pressure P _l2, second line pressure P _l2 is the tension control pressure of the transmission belt 44 Execute the optimal control of

The electronic control unit 200 includes a CPU, a RAM,
A so-called microcomputer comprising a ROM or the like is provided, which includes a vehicle speed sensor 212 for detecting the rotation speed of the drive wheels 24, an input shaft 30 and an output shaft 38 of the CVT 14.
Input shaft rotation sensor 214 for detecting the rotation speed of
And an output shaft rotation sensor 216, a throttle sensor 218 for detecting an opening degree of a throttle valve provided in an intake pipe of the engine 10, an operation position sensor 222 for detecting an operation position of the shift lever 220, and detecting operation of a brake pedal. from a brake switch 224, an engine speed sensor 226 for detecting the rotational speed N _e of the engine 10, the output pressure of the second pressure regulating valve 102, i.e. an oil pressure sensor 228 which detects the second line pressure P _l2 to the vehicle speed V
, A signal indicating the input shaft rotation speed N _in , a signal indicating the output shaft rotation speed N _out , a signal indicating the throttle valve opening θ _th , a signal indicating the operation position P _s of the shift lever 220,
Signal representing the brake operation, a signal indicative of engine rotational speed N _e, the output pressure P _sns (basic oil pressure P of the hydraulic sensor 228
_mec ) is supplied. The CPU in the electronic control unit 200 processes an input signal according to a program stored in the ROM while utilizing the temporary storage function of the RAM, and executes the first solenoid valve 202, the second solenoid valve 204,
Third solenoid valve 206, fourth solenoid valve 208, linear valve 180
And outputs a signal for driving.

Hereinafter, the main part of the control operation of the electronic control unit 200, that is, the second line oil pressure optimum control for making the second line oil pressure P _l2 coincide with the ideal pressure P _opt, and the control when the belt clamping pressure is abnormal will be described. Will be described in detail.

First, in the second line hydraulic pressure optimum control, while input signals and the like from each sensor are read, the rotation speed N _in of the input shaft 30 and the rotation speed N _{out of the} output shaft 38 are based on the read signals. , The speed ratio γ of the CVT 14, the vehicle speed V, and the like are calculated. Subsequently, based on the relationship shown in Equation 3 stored in advance, slippage of the transmission belt 44 occurs based on the actual input torque T _in , the actual diameter D _in of the transmission belt 44, and the output shaft rotation speed N _out. An optimal target pressure (ideal pressure) P _opt that can sufficiently transmit the input torque within a range not to be calculated is calculated. The second term on the right side of Equation 3 is a correction term of the centrifugal oil pressure, the third term on the right side is a margin value, and C
₁ and C ₂ are constants. Output torque T _e of the input torque T _in, that is, the engine 10, for example, well-known engine formulas speed N _e (= N _in) and the throttle valve opening theta _th, or added intake manifold negative pressure PM to it The transmission belt 44 is calculated based on the parameters.
The barbs diameter D _in is calculated from the actual speed ratio of the CVT 14 gamma (= rotational speed N _out of the rotational speed N _in / output shaft 38 of the input shaft 30).

[0030]

P _opt = C ₁ · T _in / D _in -C ₂ · N _out ² + ΔP

[0031] Then, the driving signal D based a predetermined stored relationship to the deviation so that the deviation between the actual and the second line pressure P _l2 is detected above the target pressure P _opt by the hydraulic pressure sensor 228 is eliminated It is determined, and the linear valve 180 is driven by the drive signal D.

FIG. 1 is a functional block diagram illustrating a control function of the electronic control unit 200 regarding an excessive tension abnormality of the transmission belt 44 caused by a failure such as a disconnection of the linear solenoid valve 180. In the figure, when the tension control pressure abnormal state detecting means 238 detects that the second line oil pressure P _l2, which is the tension control pressure, is abnormally high, the load on the transmission belt 44 is reduced by the transmission belt load reduction means 240. Lowered.

Next, the control when the second line oil pressure _Pl2 becomes abnormally large will be described with reference to the flowcharts of FIGS. 8, 9, and 10. FIG. FIGS. 8 and 9 show a failure determination routine for determining that the second line hydraulic pressure _Pl2 has become excessive due to a failure of the control hydraulic pressure generation means. These routines are repeatedly executed in parallel or in series. You. FIG. 10 shows a fail-safe routine that is repeatedly executed in parallel or in series with the above-described routine in order to reduce the load on the power transmission belt 44 when such clamping pressure is abnormal.

At step SA1 in FIG. 8, it is determined whether or not control for obtaining the optimum value of the second line oil pressure _P12 is being executed. At next step SA2, the actual second line oil pressure _P12 is _reduced. Whether the value is close to the value of the basic oil pressure P _mec or whether the actual second line oil pressure P _l2 and the target pressure P
_It is determined whether or not the difference from _opt is greater than a previously stored determination reference value α. The criterion value α, the feedback control of the second line pressure P _l2 is set sufficiently larger than the difference between the second line pressure P _l2 and the target pressure P _opt when normal. Then, the above step S
If the determination of A1 or SA2 is negative, the contents of the fail flag F _f is cleared to "0" in step SA3. However, the above steps SA1 and SA
If the second determination is affirmative together, the contents of the fail flag F _f is set to "1" in step SA4.

In step SB1 of FIG.
Whether or not the 0 linear solenoid 188 is disconnected is determined by its current value or the like. This disconnection failure is detected by a well-known disconnection detection circuit (not shown). If the determination at step SB1 is negative, the contents of the fail flag F _f is cleared to "0" in step SB2. However, the above step SB1
If the determination is affirmative, the contents of the fail flag F _f is set to "1" in step SB3.

[0036] In step SC1 of FIG. 10, the content of the fail flag F _f is whether or not "1" is determined. If the determination in step SC1 is denied, this routine ends. However, if the determination in step SC1 is affirmative, in step SC2, C
The speed ratio γ of the VT 14 is limited as shown in FIG. That is, the range in which the speed ratio γ of the CVT 14 can be changed is limited from the range between the solid line indicating the maximum speed ratio γ _max and the minimum speed ratio γ _min to the range between the broken lines. .

In general, factors that determine the durability of the transmission belt 44 include the belt clamping force, the transmission torque, the increase in the clamping force due to the centrifugal force of the belt itself and the centrifugal oil pressure, which increase in relation to the vehicle speed, and the hanging diameter. . The second line oil pressure P _l2 for controlling the tension of the transmission belt 44 is applied to the linear solenoid 18.
When it rises to the basic hydraulic pressure P _mec due to disconnection of 8, etc.
The tension of the transmission belt 44 also increases, and as shown in FIG.
The amount of the increase increases as the vehicle speed increases, and the margin value up to the breaking tension decreases. Further, in the case where the transmission belt 44 is a compression type belt including an endless annular hoop and a plurality of V blocks that are in close contact with each other in the thickness direction while being in contact with the inner peripheral surface of the hoop, The relationship between the bending stress characteristic of the hoop and the vehicle speed is as shown in FIG.
As is apparent from the figure, the bending stress of the hoop increases as the vehicle speed decreases (at the maximum speed ratio _γmax side) and the vehicle travels under high load, and becomes more dominant than the tension. Therefore, in FIG. 11, the range in which the speed ratio γ of the CVT 14 can be changed is limited at the low vehicle speed (the maximum speed ratio γ _max side) and the high vehicle speed (the minimum speed ratio γ _min side).

As described above, according to the present embodiment, the step SA1 corresponding to the tension control pressure abnormal state detecting means 238 is performed.
If the state where the second line oil pressure P _l2 of the power transmission belt 44 becomes abnormally high is detected in step SA 1 or step SA 2, the excessive tension of the power transmission belt 44 is determined in step SC 2 corresponding to the power transmission belt load reduction means 240. The change range of the speed ratio γ is limited so as not to be in the region, and the load on the transmission belt 44 is reduced. Therefore, even when a failure such as a disconnection of the linear valve 180 occurs, the load on the transmission belt 44 does not become excessive,
The durability of No. 4 is not impaired.

FIG. 14 shows another example of the fail-safe routine. In step SD1 of Fig., The contents of the fail flag F _f is whether or not "1" is determined. If the determination in step SD1 is denied, this routine ends. However, if the determination in step SD1 is affirmative, in step SD2, the actual belt tension indicating the load on the transmission belt 44 based on the input torque T _{in of the} CVT 14 and the hanging diameter D from the relationship stored in advance. T is calculated, in step SD3 corresponding to the subsequent tension control圧異atmospheric state detecting means 238, whether the actual belt tension T is either pre greater than set determination reference value T ₀ is determined. The determination reference value T ₀ is set in advance to determine whether the tension of the transmission belt 44 has become excessive. If the determination in step SD3 is denied, this routine is terminated. However, if the determination in step SD3 is affirmed, the tension T of the transmission belt 44 is in an excessively large state.
Step SD corresponding to transmission belt load reduction means 240
In 4, the output of the engine 10 is reduced by supplying a signal from the electronic control device 200 to the engine electronic control device (not shown). This engine 10
The output of the engine is reduced by retarding the ignition timing controlled by the engine electronic control unit, suppressing the fuel injection amount, performing fuel cut, and the like.

Also in this embodiment, when it is determined that the tension T of the transmission belt 44, that is, the load is in an excessive state, the input torque of the CVT 14 is reduced, so that the same effect as in the above-described embodiment is obtained. can get. In particular, in a high vehicle speed state, the output of the engine 10 is reduced, and as a result, the vehicle speed is also reduced. Therefore, there is an advantage that the effect of reducing the tension of the transmission belt 44 due to the reduced vehicle speed can be enjoyed.

While the embodiment of the present invention has been described with reference to the drawings, the present invention can be applied to other embodiments.

For example, the linear valve 180 of the above-described embodiment
Is configured such that when the drive current becomes zero due to disconnection or the like, the control oil pressure P _solL output _therefrom becomes zero, but it may be configured to become the maximum value. In such a case, the oil chamber 136 provided in the second pressure regulating valve 102 is provided on the plunger 116 side.

FIGS. 10 and 14 of the above embodiment.
May be executed at the same time, or may be selectively executed according to predetermined conditions.

In the above-described embodiment, the second line hydraulic pressure is controlled by driving the linear valve 180 so that the target pressure P _opt and the actual second line hydraulic pressure P _l2 detected by the hydraulic pressure sensor 228 match. Although _P12 was controlled, it may be controlled by open loop control. In this case, based on the actual gear ratio γ and the throttle valve opening theta _th a predetermined stored relationship second
The basic hydraulic pressure P _{mec of the} pressure regulating valve 102 is determined, and the target pressure P
A lowering pressure P _down to be reduced from the basic oil pressure P _mec to obtain _opt is calculated by subtracting the target pressure P _opt from the basic oil pressure P _mec, and a magnitude corresponding to the lowering pressure P _down is obtained from a relationship stored in advance. a decision control oil pressure P _Soll is, the drive signal D to generate the control pressure P _Soll is outputted from the electronic control unit 200 to the linear valve 180.

The above is merely an embodiment of the present invention, and the present invention can be variously modified without departing from the gist thereof.

[Brief description of the drawings]

FIG. 1 is a functional block diagram illustrating a main part of a control function of an electronic control device in the embodiment of FIG. 2;

FIG. 2 is a diagram illustrating an example of a belt type continuously variable transmission for a vehicle to which the present invention is applied.

FIG. 3 is a circuit diagram illustrating a main part of a hydraulic control circuit of FIG. 2;

FIG. 4 is a diagram for explaining control specification of a second pressure regulating valve in FIG. 3;

FIG. 5 is a diagram illustrating a change characteristic of a throttle pressure in FIG. 3;

FIG. 6 is a diagram for explaining a change characteristic of a speed ratio pressure shown in FIG. 3;

FIG. 7 is a diagram illustrating a change characteristic of a control oil pressure output from the linear valve of FIG. 3;

FIG. 8 is a diagram illustrating a failure determination routine executed in the electronic control device of FIG. 2;

FIG. 9 is a diagram illustrating another failure determination routine executed in the electronic control device of FIG. 2;

FIG. 10 is a diagram illustrating a fail-safe routine executed in the electronic control device of FIG. 2;

FIG. 11 is a diagram illustrating a range of a gear ratio limited by a fail-safe routine of FIG. 10;

FIG. 12 is a diagram illustrating the relationship between vehicle speed and transmission belt tension.

FIG. 13 is a diagram illustrating a relationship between a vehicle speed and a bending stress of a hoop of a transmission belt.

FIG. 14 is a diagram illustrating another fail-safe routine executed in the electronic control device of FIG. 2;

[Explanation of symbols]

 14: Belt type continuously variable transmission 40, 42: Variable pulley 44: Transmission belt 54, 56: Hydraulic cylinder 102: Second pressure regulating valve (pressure regulating valve) 238: Tension control pressure abnormal state detecting means 240: Transmission belt load reducing means

Continuation of the front page (56) References JP-A-4-248066 (JP, A) JP-A-64-49759 (JP, A) JP-A-1-269620 (JP, A) JP-A-3-181662 (JP) JP-A-2-3751 (JP, A) JP-A-5-240331 (JP, A) JP-A-2-212658 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) F16H 59/00-61/12 F16H 61/16-61/24 F16H 63/40-63/48

Claims (2)

(57) [Claims] An endless annular hoop and an inner peripheral surface of the hoop
In close contact with each other in the thickness direction while in contact with
A pair of variable pulleys around which a compression type transmission belt composed of a set V block is wound and the effective diameter of which is variable, and a pair of hydraulic cylinders for applying a clamping force to the pair of variable pulleys. In a vehicle belt-type continuously variable transmission in which the gear ratio is continuously changed by changing the thrust ratio of a pair of hydraulic cylinders, tension control is performed based on an engine load and a gear ratio of the belt-type continuously variable transmission. A hydraulic control device, comprising: a pressure regulating valve for regulating pressure; and optimally controlling the tension of the transmission belt by the tension control pressure, wherein the tension control detects an abnormal state of the tension control pressure regulated by the pressure regulation valve. Pressure abnormal state detecting means, and when the tension control pressure abnormal state detecting means detects a state in which the tension control pressure is abnormal, the minimum gear ratio side
Is the maximum gear ratio in relation to the reduction of the margin pressure to breaking tension.
On the side, the transmission is related to an increase in the bending stress of the hoop.
The stepless change is performed so that the tension range of the moving belt does not become excessive.
A hydraulic control device for a belt-type continuously variable transmission for a vehicle, comprising: a transmission belt load reduction unit that reduces a load on the transmission belt by limiting a range in which a speed ratio of a transmission can be changed . (2) The transmission belt is wound and the effective diameter is
A pair of variable pulleys and a pair of variable pulleys
A pair of hydraulic cylinders for applying force.
Shifting by changing the thrust ratio of the pair of hydraulic cylinders
Belt-type continuously variable transmission for vehicles whose ratio can be changed steplessly
The engine load and the belt type continuously variable transmission
A pressure regulating valve that regulates the tension control pressure based on the gear ratio
The tension control pressure optimizes the tension of the transmission belt.
A hydraulic control device for controlling, An abnormal state of the tension control pressure regulated by the pressure regulating valve is detected.
An abnormal tension control pressure abnormal state detecting means, The tension control pressure is detected by the tension control pressure abnormal state detecting means.
If an abnormal state is detected, the continuously variable transmission
Of the power transmission belt by reducing the input torque of
Transmission belt load reduction means to reduce the load Including
Control device for a belt type continuously variable transmission for vehicles
Place.