JP3295568B2 - Line pressure control device for continuously variable transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line pressure control device for electronically controlling a line pressure of a hydraulic control system in a belt-type continuously variable transmission for a vehicle, and more particularly to a line pressure control device for upshifting and downshifting of shift control. Related to line pressure control.

[0002]

2. Description of the Related Art A large number of electronic control of a continuously variable transmission (CVT) of this type have already been proposed by the present applicant. Explaining the outline of this electronic control system, a hydraulic pressure control system is provided with a line pressure control valve for controlling a line pressure as a secondary pressure and a shift control valve for controlling a primary pressure. In a shift control system of electronic control, a target speed ratio is set based on a target primary pulley speed and a secondary pulley speed, and an actual speed ratio is calculated based on the primary pulley speed and the secondary pulley speed. By outputting an electric signal of an operation amount corresponding to the target primary pressure to the shift control valve to control the primary pressure, the gear ratio is shifted up to the OD side or downshifted to the LOW side according to the traveling state. Speed control.

The line pressure control system estimates a CVT input torque and calculates a required line pressure per unit torque as shown in FIG.
Are set in an increasing function by the speed ratio as shown in FIG.
The target line pressure is calculated by multiplying the T input torque by the required line pressure. Then, by outputting an electric signal of an operation amount corresponding to the target line pressure to the line pressure control valve, the line pressure is reduced to CV.
Increases or decreases according to the T input torque.
The W side is controlled to be high and the OD side is controlled to be low, so that the belt clamping force due to the line pressure is always set to the minimum necessary.

[0006] In the shift control during the transition between the upshift and the downshift, the actual speed ratio always lags behind the target speed ratio as shown in FIG. For this reason, if the required line pressure is set in the line pressure control by, for example, a function of the actual speed ratio, the line pressure becomes excessive due to the delay of the actual speed ratio during an upshift, so that belt slip hardly occurs. However, at the time of downshifting, the line pressure rises slowly due to the delay of the actual gear ratio, and the line pressure itself tends to be insufficient because the line pressure itself is delayed.
Therefore, if a downshift is performed rapidly, belt slip is likely to occur due to insufficient line pressure.

Since the required line pressure may be set as a function of the gear ratio, the target gear ratio can be used instead of the actual gear ratio. However, when the target gear ratio is used, the relationship is completely opposite to that described above as shown in FIG. 6, and the line pressure first drops due to a shift delay during an upshift, and belt slip is likely to occur. Therefore, using this target gear ratio does not provide a fundamental solution. Therefore, in the line pressure control, it is desired to prevent the belt slip due to the insufficient line pressure in both the upshift and the downshift.

Conventionally, as for the line pressure control of the continuously variable transmission, for example, there is a prior art disclosed in Japanese Patent Application Laid-Open No. 63-1847, in which the line pressure is temporarily increased to a level higher than normal during a rapid shift in the upshift direction. Thus, it is shown that the belt does not slip against the large inertia of the pulley. JP Hei 3
In the prior art of JP-A-69850, when a pulsation reducing orifice is provided in the line pressure introduction port of the speed ratio control means, the line pressure is changed to be high at the time of upshifting, and the hydraulic pressure is applied to one pulley regardless of the orifice. It has been shown to be introduced quickly to compensate for the reduced shift response.

[0007]

In the above prior art, since the line pressure is changed to a high value during an upshift, the control using the required line pressure of the function of the actual speed ratio requires The line pressure becomes too high at the time of the upshift, and there is a possibility that the shift control by the primary pressure is impaired. Control using the required line pressure as a function of the target gear ratio seems to be effective, but it must be corrected to increase the line pressure, and the control becomes complicated and affects shift control. is there.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to prevent belt slip due to insufficient line pressure during upshift and downshift in electronic control of line pressure.

[0009]

To achieve this object, a line pressure control device for a continuously variable transmission according to a first aspect of the present invention, as shown in FIG. A primary pulley 14 having a cylinder 14a is provided, and a secondary pulley 15 having a secondary cylinder 15a is provided on a secondary shaft 13 on the wheel side. And the oil passage 2 to the secondary cylinder 15a.
3, a line pressure control valve 26 is provided to control the line pressure of the secondary cylinder 15a by an electric signal of the control unit 40 to clamp the drive belt, and the primary pressure is changed in the oil passage 25 to the primary cylinder 14a. A shift control valve 27 is provided for controlling the speed change so that the actual speed ratio follows the target speed ratio. The control unit 40 detects a speed change control upshift or downshift based on a change state of the target speed ratio. Direction detecting means 6
0, a required line pressure setting for selecting an actual speed ratio for an upshift, and selecting a target speed ratio for a downshift, and setting the required line pressure per unit torque in an increasing function for these speed ratios. Means 42, a target line pressure calculating means 43 for calculating a target line pressure based on the input torque of the continuously variable transmission and a required line pressure per unit torque, and an electric signal of an operation amount corresponding to the target line pressure is supplied to a line pressure control valve. 26, and an operation amount setting means 44 for outputting the operation amount to the control unit 26.

[0010]

According to the first aspect of the present invention, the engine power is input to the primary pulley 14 of the primary shaft 12 when the vehicle is running, and at this time, the belt pressure is controlled by the line pressure of the secondary cylinder 15a by the line pressure control valve 26. Is done. The transmission control valve 27 controls the primary cylinder 14
The speed is controlled so as to change the ratio of the winding diameter of the drive belt 16 to both the pulleys 14 and 15 by changing the primary pressure a. Therefore, for example, at the time of acceleration, the actual gear ratio is up-shifted in the direction from the maximum gear ratio LOW to the minimum gear ratio OD while following the target gear ratio. In addition, for example, during deceleration, the actual speed ratio similarly shifts down from OD to LOW while following the target speed ratio and continuously changes speed.

At this time, the target line pressure is calculated by the target line pressure calculating means 43 of the control unit 40 based on the CVT input torque and the required line pressure per unit torque, and the operation amount setting means 44 is used to calculate the operation amount according to the target line pressure. By outputting an electric signal to the line pressure control valve 26 and operating the line pressure, the line pressure is controlled in accordance with the input torque and the gear ratio, and the belt pressure is always clamped with a minimum necessary force by the line pressure. In this case, the necessary line pressure setting means 42 selects an actual gear ratio with a larger gear ratio due to a shift delay during an upshift, and selects a target gear ratio with a larger gear ratio as a result of a shift advance during a downshift. Therefore, in both upshifts and downshifts, the required line pressure is set higher, so that the line pressure is kept higher during the upshift, and the line pressure rises earlier during the downshift, causing belt slip. It is surely prevented.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. Referring to FIG. 2, as a continuously variable transmission to which the present invention is applied, an overall configuration of a drive system in which an electromagnetic clutch is combined with a belt-type continuously variable transmission will be described. The engine 1 includes a continuously variable transmission 4 via an electromagnetic clutch 2 and a forward / reverse switching device 3.
, And transmitted to the drive wheels 9 from the continuously variable transmission 4 via a set of reduction gears 5, an output shaft 6, a differential device 7, and an axle 8.

The electromagnetic clutch 2 has a drive member 2a directly connected to the crankshaft 10 of the engine 1, and a driven member 2b having a built-in clutch coil 2c and directly connected to the input shaft 11. When the clutch current Ic is supplied to the clutch coil 2c by the control unit 40, the magnetic powder magnetically couples and accumulates the magnetic powder in a gap between the two members 2a and 2b, and transmits the clutch torque by this coupling force. . That is, when starting, the clutch current Ic according to the engine speed Ne is supplied to smoothly connect the clutch, and the clutch current Ic is reduced below the set vehicle speed to release the clutch or generate a predetermined drag torque.

The forward / reverse switching device 3 is constituted by a gear, a hub and a sleeve between the input shaft 11 and the primary shaft 12 in a synchronous meshing manner. Then, the input shaft 11 is changed to the primary shaft 1
2, a retreat position for reversing the rotation direction of the input shaft 11 and transmitting it to the primary shaft 12,
12 has a neutral position for cutting.

The continuously variable transmission 4 has a primary shaft 12 and a secondary shaft 13 arranged in parallel with the primary shaft 12. The primary shaft 12 is provided with a primary pulley 14 having a primary cylinder 14a and a variable pulley interval. The secondary shaft 13 is provided with a secondary pulley 15 having a similar secondary cylinder 15a.
The drive belt 16 is wound around. Then, for example, during acceleration, the drive belt 16 shifts from LOW having the largest speed change ratio with the largest winding diameter to the secondary pulley 15 toward the primary pulley 14 and is upshifted. Also, for example, during deceleration, the drive belt 16
In this configuration, the speed is continuously changed so as to shift from the minimum speed ratio OD having the largest winding diameter to the secondary pulley 15 and downshift.

Next, the hydraulic control system will be described. First, an oil passage 22 from an oil pump 21 communicating with an oil pan 20 is connected to a line pressure control valve 26 of a proportional electromagnetic relief valve.
Communicate with The line pressure control valve 26 is a proportional solenoid 2
When a solenoid current Is flows from the control unit 40 to 6a, the pump discharge pressure is adjusted to generate a predetermined line pressure Ps. The line pressure Ps is constantly supplied to the secondary cylinder 15a by the oil passage 23 to perform belt clamping. Further, the line pressure Ps is guided to a shift control valve 27 of a proportional electromagnetic pressure reducing valve by an oil passage 24. When the solenoid current Ip from the control unit 40 flows through the proportional solenoid 27a, the shift control valve 27 changes the line pressure Ps to the primary cylinder 1
4a, a predetermined primary pressure Pp is generated, and the primary pressure Pp causes the two pulleys 1 of the drive belt 16 to rotate.
It is configured to change the ratio of the winding diameter to 4,15.

Further, the electronic control system will be described. The control unit 40 has a clutch control function, a shift control function, and a line pressure control function, and has an arithmetic function and an input / output function necessary for each control. Line pressure sensor 3 for detecting line pressure Ps as an input signal
0, engine speed Ne by ignition pulse etc.
, An engine speed sensor 31 for detecting the primary pulley speed Np,
It has a secondary rotation speed sensor 33 for detecting the secondary pulley rotation speed Ns, a throttle opening sensor 34 for detecting the throttle opening θ, and various switches 37 such as a range switch, an accelerator switch, and a brake switch.
These sensor and switch signals are input to the control unit 40 and are electrically processed. The clutch current Ic is output to the electromagnetic clutch 2 to perform clutch control, and the solenoid current Is is output to the line pressure control valve 26 to perform line pressure control. Then, the solenoid current Ip is output to the shift control valve 27 to perform shift control.

Next, the operation of this embodiment will be described. First, the oil pump 21 is driven by the operation of the engine 1 to generate a hydraulic pressure, and the hydraulic pressure is guided to the line pressure control valve 26. Then, the pressure is adjusted to the line pressure Ps by the line pressure control valve 26, and the transmission control valve 27 is
To control the primary pressure Pp.

At the time of starting, for example, when the D range is selected, the forward / reverse switching device 3 is brought to the forward position, and the input shaft 11 and the primary shaft 12 are directly connected. When the accelerator pedal is depressed, a clutch current Ic corresponding to the increase in the engine speed Ne flows, and the electromagnetic clutch 2 is smoothly connected. For this reason, the power of the engine 1 is input to the continuously variable transmission 4 via the electromagnetic clutch 2 and the forward / reverse switching device 3 to be shifted, and the shifted power is transmitted to the drive wheels 9 to start running the vehicle. Then, the line pressure control and the shift control are executed when the vehicle stops and runs.

The line pressure control will be described with reference to the functional blocks of the entire control system shown in FIG. 3 and the flowchart shown in FIG. First, the throttle opening θ and the engine speed Ne are input to the input torque calculation unit 41, and the engine torque Te is estimated from the torque characteristic of θ−Ne. Further, the CVT input torque Ti is calculated in consideration of the clutch torque and the amplification factor in the case of the torque converter (step S1). On the other hand, the required line pressure Psu per unit torque is
Is set in an increasing function according to the speed ratio i (step S5). These CVT input torque Ti and required line pressure P
su is input to the target line pressure calculation unit 43, and the target line pressure Pss required in this case is calculated as Pss = Ti · Psu ·
It is calculated by Ks (Ks is a slight safety factor) (step S6). The target line pressure Pss is determined by the solenoid current setting unit 4
4 is converted into a solenoid current Is corresponding to the target line pressure Pss, and this solenoid current Is is
5 to the proportional solenoid 26a (step S5).
7).

Therefore, when the vehicle is stopped, the CVT input torque Ti
Is substantially zero, the line pressure Ps is controlled to be very low together with the target line pressure Pss. At the start of accelerator depression,
Since the CVT input torque Ti and the required line pressure Psu are large, the target line pressure Pss is calculated to be high, and the solenoid current Is in this case flows through the proportional solenoid 26a.
Therefore, the line pressure control valve 26 operates so as to reduce the drain amount, and the line pressure Ps is controlled to be high. Therefore, the clamping force of the belt 16 due to the line pressure Ps in the secondary cylinder 15a is also increased, and belt slip is prevented.

After the shift is started, the required line pressure Psu is set to decrease as the gear ratio i gradually decreases. In this case, when the CVT input torque Ti is also reduced by the accelerator operation, the target line pressure Pss is calculated to be lower, and the line pressure Ps is controlled to be reduced. Therefore, belt 1
6 is always clamped with the minimum required force.

The shift control will be described with reference to the functional blocks of the entire control system shown in FIG. 3 and the flowchart shown in FIG. In the hydraulic pressure ratio control system, the primary pulley rotation speed Np and the secondary pulley rotation speed Ns are input to the actual speed ratio calculation unit 46, and the actual speed ratio is is calculated from is = Np / Ns (step S11). Further, the CVT input torque Ti, the required line pressure Psu, and the actual line pressure Ps from the hydraulic pressure sensor 30 are input to the torque ratio calculation unit 49. Here, when the CVT input torque Ti increases, for example, the shift proceeds in the downshift direction, and the CVT input torque Ti affects the actual speed ratio is.
Therefore, with respect to the relationship between the CVT input torque Ti and the actual speed ratio is, the maximum torque (Ps
/ Psu) and the torque ratio K of the current CVT input torque Ti
t is calculated by Kt = Ti / (Ps / Psu) (step S12).

The torque ratio Kt and the actual gear ratio is input to a hydraulic ratio setting unit 50. Here, the actual speed ratio is in the steady state is determined by the oil pressure ratio between the line pressure Ps and the primary pressure Pp, so that the oil pressure ratio Kp (Pp / Ps) is a function of the actual speed ratio is. Further, from the current torque transmission state, the hydraulic pressure ratio Kp becomes a function of the torque ratio Kt, whereby the hydraulic pressure ratio Kp is changed to Kp
= F (Kt / is) (step S13).
Then, the hydraulic pressure ratio Kp and the line pressure Ps are input to the required primary pressure calculation unit 51, and the hydraulic pressure ratio Kp is applied to the line pressure Ps.
The required primary pressure Ppd for balancing with p is calculated by Ppd = Kp · Ps−gp, taking into account the centrifugal oil pressure gp of the primary cylinder portion based on the primary rotation speed Np (step S14).

In the flow control system, the actual gear ratio is and the throttle opening θ are input to the target primary pulley rotation speed search section 47, and the target primary pulley rotation speed Npd is determined in relation to i−θ (step S15). The target primary pulley rotation speed Npd and the secondary pulley rotation speed Ns are input to the target gear ratio calculator 48, and the target gear ratio it is set to it.
= Npd / Ns (step S1).
6) Thus, the target gear ratio it corresponding to each driving and running condition is obtained based on the gear shift pattern. The actual speed ratio is and the target speed ratio it are input to the speed change pressure calculation unit 52, and a correction amount Δ corresponding to the difference between the speed ratios it and is is input.
Pp is obtained (step S17).

The required primary pressure P of the hydraulic ratio control system
pd and the shift pressure ΔPp of the flow control system are input to the target primary pressure calculation unit 53, and the target primary pressure Pps is
At the time of upshift, it is calculated by Pps = Ppd + ΔPp, and at the time of downshift, it is calculated by Pps = Ppd−ΔPp (step S18). The target primary pressure Pps is further input to a solenoid current setting unit 54 to be converted into a solenoid current Ip corresponding to the target primary pressure Pps.
a (step S19).

Therefore, when the vehicle stops at Ns = 0, the target speed ratio it is set to the maximum speed ratio LOW (for example, 2.5) on the mechanism of the continuously variable transmission 4, and the speed change control valve 27 is set to the drain (oil drain) side. And the primary pressure Pp becomes substantially zero. For this reason, the line pressure Ps is supplied only to the secondary cylinder 15a, and the continuously variable transmission 4 is in the low speed stage with the maximum speed ratio LOW where the belt 16 is shifted to the secondary pulley 15 side most.

At the time of running after starting, the target primary pulley rotation speed Npd is set according to the driving and running conditions, and as the secondary pulley rotation speed Ns rises with the vehicle speed, the target speed ratio it gradually decreases to start shifting. I do.
Then, the target primary pressure Pps is calculated to be gradually higher by the correction amount ΔPp corresponding to the difference between the torque ratio Kt, the oil pressure ratio Kp, the actual speed ratio is and the target speed ratio it. Therefore, the solenoid current Ip also gradually changes to the pressure increasing side, the oil supply amount is increased by the shift control valve 27, the primary pressure Pp is controlled to be sequentially increased, and the belt 16 is sequentially shifted to the primary pulley 14 to reduce the gear ratio. Upshift to a smaller high speed stage. Then, it is possible to change the speed to the minimum speed ratio OD (for example, 0.5) and drive at high speed.

If the target primary pulley rotation speed Npd increases when the accelerator pedal is depressed, or if the secondary pulley rotation speed Ns decreases with the vehicle speed during deceleration, the target gear ratio it increases. For this reason, the target primary pressure Pps is calculated to be low. Accordingly, the primary pressure Pp is reduced and decreased by the transmission control valve 27, and the belt 16 shifts to the secondary pulley 15 again and downshifts. In this way, the actual speed ratio i
s is upshifted or downshifted while following the target speed ratio it as shown in FIG.

Next, a description will be given of a countermeasure for preventing a line pressure shortage due to a delay in the actual speed ratio between the upshift and the downshift in the shift control. First, in the line pressure control, in order to set the required line pressure Psu per unit torque in an increasing function with respect to the speed ratio i, the required line pressure Psu and the target line pressure Pss are determined by setting the speed ratio i to be relatively large.
Can be increased. As is apparent from FIG. 6, the speed ratio i is larger in the actual speed ratio is than the speed ratio in the upshift, and the target speed ratio it is larger in the target speed ratio it in the downshift because of the speed advance. i is large. Therefore, by using the actual speed ratio is during an upshift and using the target speed ratio it during a downshift, the required line pressure Psu becomes larger with the speed ratio i in any case.

The control in this case will be described with reference to the functional blocks of the entire control system of FIG. 3 and the flowchart of FIG. First, the target speed ratio it is input to the speed change direction detection unit 60,
An upshift is detected based on a decrease in the target gear ratio it, and a downshift is detected based on an increase (step S2). The signal in the shift direction, the actual speed ratio is, and the target speed ratio it are input to the required line pressure setting unit 42, and the up-shift operation selects the actual speed ratio is (step S3), and sets the required line pressure Psu to the actual speed ratio. It is set by the function of is (step S5). At the time of downshift, the target gear ratio it is selected (step S4), and the required line pressure Psu is set as a function of the target gear ratio it (step S5). Based on the required line pressure Psu set in this way, the target line pressure Ps
s is calculated and the line pressure is controlled.

Therefore, for example, when upshifting to the OD side during acceleration, the required line pressure Psu and the target line pressure Pss are kept high based on the actual speed ratio is of the shift delay, and the line pressure Ps is controlled to be high. . Further, for example, when downshifting to the LOW side during deceleration, the required line pressure Psu and the target line pressure Pss are increased earlier on the basis of the target speed ratio it of the shift advance, and the line pressure Ps is similarly controlled to be higher. For this reason, in both cases of the upshift and the downshift, the line pressure Ps is controlled to be relatively high as indicated by the one-dot chain line in FIG. 6, and the belt 16 is reliably clamped, thereby preventing the belt slip.

Although the embodiment of the present invention has been described above, the actual gear ratio and the target gear ratio can be calculated by other methods. Further, the present invention can be applied to all cases where the line pressure is electronically controlled in relation to the gear ratio.

[0034]

As described above, in the line pressure control device for a continuously variable transmission according to the first aspect of the present invention, the control unit for controlling the line pressure controls the upshift of the shift control by changing the target gear ratio. Alternatively, a shift direction detecting means for detecting a downshift and an actual gear ratio during an upshift and a target gear ratio during a downshift are selected, and the required line pressure per unit torque is increased for these gear ratios. A required line pressure setting means for setting the function, a target line pressure calculating means for calculating a target line pressure based on a CVT input torque and a required line pressure per unit torque, and an electric signal of an operation amount corresponding to the target line pressure is supplied to the line. Since it is configured to include the operation amount setting means for outputting to the pressure control valve, it is possible to appropriately control the line pressure during the upshift and the downshift in the shift control.

At the time of an upshift, the actual speed ratio of a shift delay is used, and at the time of a downshift, the required line pressure per unit torque is set in an increasing function using the target speed ratio of a shift advance to perform line pressure control. Therefore, in each case, the line pressure is increased, and the belt slip can be reliably prevented. Since this method selects one of the actual speed ratio and the target speed ratio according to the speed change direction, control is easy. In addition, the margin when setting the line pressure can be reduced, so that the driving force loss due to excessive belt tension and the pump load are reduced, and the fuel efficiency and the like are improved.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims showing a configuration of a line pressure control device of a continuously variable transmission according to the present invention.

FIG. 2 is a skeleton diagram showing a drive system and a hydraulic control system of an example of a continuously variable transmission to which the present invention is applied.

FIG. 3 is a functional block diagram illustrating an entire configuration of a control unit.

FIG. 4 is a flowchart of line pressure control.

FIG. 5 is a flowchart of shift control.

FIG. 6 is a diagram showing gear shifting states during an upshift and a downshift.

FIG. 7 is a diagram showing a setting map of a required line pressure with respect to a gear ratio.

[Description of Signs] 12 Primary shaft 13 Secondary shaft 14 Primary pulley 14a Primary cylinder 15 Secondary pulley 15a Secondary cylinder 16 Drive belt 23, 25 Oil passage 26 Line pressure control valve 27 Shift control valve 40 Control unit 42 Required line pressure setting unit ( Required line pressure setting means) 43 Target line pressure calculating section (Target line pressure calculating means) 44 Solenoid current setting section (Operation amount setting means) 60 Shift direction detecting section (Shift direction detecting means)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F16H 59/00-61/12 F16H 61/16-61/24 F16H 63/40-63/48

Claims (1)

(57) [Claims] A primary pulley having a primary cylinder is provided on a primary shaft on the engine side, a secondary pulley having a secondary cylinder is provided on a secondary shaft on the wheel side, and a drive belt is wound between these pulleys. A line pressure control valve is provided to control the line pressure of the secondary cylinder by controlling the line pressure of the secondary cylinder by the electric signal of the control unit in the oil passage to the secondary cylinder, and is wound around the oil passage to the secondary cylinder in a stepless manner by changing the diameter ratio. ,
In a continuously variable transmission provided with a shift control valve that changes the primary pressure in the oil passage to the primary cylinder and controls the shift so that the actual gear ratio follows the target gear ratio, the control unit is controlled by the change state of the target gear ratio. A shift direction detecting means for detecting an upshift or a downshift of the shift control, and based on the detection result of the shift direction detecting means, an actual gear ratio is selected at the time of the upshift, and a required line per unit torque
The required line is set such that the pressure is set in an increasing function with respect to the actual speed ratio, and at the time of downshifting, the target speed ratio is selected and the required line pressure per unit torque is set in an increasing function with respect to the target speed ratio. Pressure setting means; target line pressure calculating means for calculating a target line pressure based on the input torque of the continuously variable transmission and a required line pressure per unit torque; and a line pressure control valve for transmitting an electric signal of an operation amount corresponding to the target line pressure. A line pressure control device for a continuously variable transmission, comprising: an operation amount setting unit that outputs the operation amount to the control unit.