JPH0554583B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

TECHNICAL FIELD The present invention relates to a control device for electronically controlling a shift speed in a belt-type continuously variable transmission for a vehicle, and specifically relates to correction during kickdown.

[Conventional technology]

Regarding the speed change control of this type of continuously variable transmission, for example, there is a basic one shown in Japanese Patent Application Laid-Open No. 55-65755. It is shown that the speed change is controlled mechanically. However, in this shift control method, the shift speed, that is, the rate of change of the gear ratio, is mechanically determined by each gear ratio, primary pressure, etc., and the shift speed cannot be directly controlled, so there is a limit to responsiveness during transients, and it is difficult to converge. Overshoot and hunting are likely to occur. Therefore, in recent years,
It has been proposed to electrically process various information and requirements and electronically control the speed change of a continuously variable transmission by controlling the speed change. Conventionally, regarding the speed change control of the above-mentioned continuously variable transmission, there is a prior art, for example, disclosed in Japanese Patent Application Laid-Open No. 159456/1983, which includes a speed ratio change directional switching valve device and a speed ratio change control valve device as the speed change control. Then, with the changing direction switching valve device switched to either oil supply or oil draining, the changing speed control valve device operates the spool valve at a predetermined duty ratio using a solenoid valve to control the changing speed of the gear ratio. It is shown. Regarding correction during acceleration, for example, JP-A-59
There is a prior art disclosed in Japanese Patent No. 205053, which teaches that during acceleration, the speed change speed is set to increase according to the throttle opening or a change in the opening.

[Problem to be solved by the invention]

However, according to the former of the above-mentioned prior art, since two types of valve devices are used for speed change control, the structure is inevitably complicated. Furthermore, the latter prior art has the advantage that the faster the acceleration occurs, the faster the shift speed becomes, and the responsiveness improves. However, if the shift speed is set in the same way in the case of full-throttle acceleration such as during a kickdown, the value of the shift speed becomes very large and a sudden downshift occurs. This results in an increase in shift shock, and in extreme cases, the engine power is used only to increase the engine speed, resulting in a loss of acceleration of the vehicle body. In view of these points, the present invention provides a control device for a continuously variable transmission that is capable of electronically controlling the shift speed using simple open-loop control and smoothing the shift during a downturn. The purpose is to

[Means to solve the problem]

In order to achieve this object, the present invention has a variable speed control valve 23 having control ports 23a, 23b and a spring 23c that operate to switch between an oil supply position and an oil drain position, and a flow rate restriction means 32 from a line pressure oil path 21.
The oil passage 26 that branches through the solenoid valve 28
The control unit 40 generates a signal hydraulic pressure according to an electric signal from the control unit 40, and this signal hydraulic pressure is introduced into the control port 23a of the speed change control valve 23 through an oil passage 34 to control the speed change. The control unit 40 also includes means 45 for calculating the actual gear ratio based on the primary pulley rotation speed and secondary pulley rotation speed, and means 46 for determining the target gear ratio based on the throttle opening and the secondary pulley rotation speed.
and means 47 for setting a coefficient according to the acceleration state.
, means 52 for reducing the coefficient when the deviation between the target gear ratio and the actual gear ratio is equal to or greater than a set value, and calculating a target gear change speed from the deviation between the target gear ratio and the actual gear ratio and the corrected coefficient. It is characterized by comprising means 48 and means 49 for determining a manipulated variable based on the relationship between the target gear change speed and the actual gear ratio and outputting an electrical signal of this manipulated variable.

[Effect]

In the present invention having the above configuration, the continuously variable transmission basically converts an electric signal from the control unit 40 into a signal oil pressure by the solenoid valve 28, and introduces this signal oil pressure into the control port 23a of the variable speed control valve 23. It operates repeatedly in two positions: oil supply and oil drain. Then, the primary pressure is increased or decreased while changing the speed change speed according to the manipulated variable of the electric signal, and the speed change is controlled electronically. In the control unit 40, a target gear ratio is set according to driving and running conditions, and a target gear shift speed is calculated based on the deviation between the target gear ratio and the actual gear ratio and a coefficient, and a shift up or a downshift is performed depending on the sign of the gear shift speed. is determined. Then, the manipulated variables for upshifting and downshifting are set based on the target shift speed and actual gear ratio, respectively, and electrical signals of these manipulated variables are output for open-loop control. Therefore, the shift is down or up depending on the operating amount of the electric signal, and at this time, the actual gear ratio quickly follows the target gear ratio while changing the gear shift speed with a slope according to the shift speed of the deviation between the two.
Moreover, it is smoothly converged. In this way, the shift speed is controlled in a stepless manner with good response throughout the entire shift range. Also, during acceleration, the deviation between the target gear ratio and the actual gear ratio is compared with a set value, and if the deviation is greater than the set value, it is determined that the full-throttle acceleration should be reduced. At the time of kickdown, the coefficient is corrected to decrease, so that the target shift speed becomes temporarily smaller. Therefore, downshifting starts smoothly at a slow shift speed, avoiding a shift shock, and the engine power is appropriately distributed between the increase in engine speed and the acceleration of the vehicle body, resulting in good acceleration.

【Example】

Embodiments of the present invention will be described below based on the drawings. Referring to FIG. 1, an outline of a continuously variable transmission and a hydraulic control system to which the present invention is applied will be explained. First, the drive system will be described. An engine 1 is connected to a main shaft 5 of a continuously variable transmission 4 via a clutch 2 and a forward/reverse switching device 3. In the continuously variable transmission 4, a subshaft 6 is arranged parallel to a main shaft 5, a primary pulley 7 is provided on the main shaft 5, a secondary pulley 8 is provided on the subshaft 6, and a drive belt 11 is provided on both pulleys 7, 8. is wrapped.
Both pulleys 7 and 8 are connected to the fixed side and the hydraulic cylinders 9 and 1.
0 and a movable side that is movable in the axial direction, the pulley interval is variable, and the primary cylinder 9 has a larger pressure receiving area than the secondary cylinder 10. The belt is properly clamped by the line pressure of the secondary cylinder 10, and the ratio of the winding diameter of the drive belt 11 to the pulleys 7 and 8 is changed by the primary pressure of the primary cylinder 9, thereby continuously changing the speed. Further, the subshaft 6 is connected to an output shaft 13 via a set of reduction gears 12 . and output shaft 1
3 is configured to be transmitted to drive wheels 16 via a final gear 14 and a differential gear 15. Next, the hydraulic control system of the continuously variable transmission 4 will be explained. First, it has an oil pump 20 driven by an engine 1, and a line pressure oil passage 21 on the discharge side of the oil pump 20 is connected to a secondary cylinder 10,
It communicates with a line pressure control valve 22 and a speed change control valve 23 , and the speed change control valve 23 communicates with the primary cylinder 9 via an oil passage 24 . The line pressure oil passage 21 further communicates with an oil passage 26 via an orifice 32a that restricts the flow rate, and a portion of the line pressure is taken out. The oil passage 26 is connected to the regulator valve 2
5, a constant regulator pressure PR is generated,
The oil passage 26 for this regulator pressure PR is connected to the line pressure control solenoid valve 27 via the orifice 32b.
will be communicated to. Also, the oil passage 26 has an orifice 32c.
The oil passage 35 has an orifice 32d.
The solenoid valve 28 is connected to the solenoid valve 28 for controlling the speed change speed. The solenoid valve 27 is configured to drain oil when the duty signal from the control unit 40 is on, and the pulsed duty pressure Pd generated by the solenoid valve 27 is smoothed by the accumulator 30, and the line pressure is restored by the oil path 33. It is supplied to the control valve 22. The solenoid valve 28 has a similar configuration, and the pulsed duty pressure Pd generated by the solenoid valve 28 is directly supplied to the speed change control valve 23 through the oil passage 34. The line pressure control valve 22 is configured to control the line pressure PL by a function of the initially set spring and the duty pressure Pd of the oil passage 33. The speed change control valve 23 has one control port 23
A constant regulator pressure PR of the oil passage 35 acts on b, and a spring 23c acts on the other control port 23a.
is energized, and the duty pressure Pd of the oil passage 34 acts. The system is configured to repeatedly switch between an oil supply position where the line pressure oil passage 21 is connected to the oil passage 24 and an oil drain position where the oil passage 24 is connected to the drain oil passage 29 by turning on and off the duty pressure Pd. Ru. For example, if the duty ratio is increased and the zero time of the duty pressure Pd is lengthened, the oil supply amount>
Shifts up depending on the amount of oil discharged. On the other hand, if the duty ratio is decreased and the constant pressure time of the duty pressure Pd is lengthened, the oil supply amount is set to less than the oil displacement amount, so that a downshift is performed. Here, the control principle of shift speed control will be explained. First, the required oil amount V of the primary cylinder 9 is
It is determined mechanically in relation to the gear ratio i, and V=f1(i), and the flow rate Q is the oil amount V differentiated with respect to time, so Q=dv/dt={df1(i) )/di}·(di/dt), and the flow rate Q and the gear change speed di/dt correspond to each other using the gear ratio i as a parameter. Therefore, the following equation is obtained. di/dt=f2(Q,i) Also, if primary pressure Pp, line pressure PL, flow coefficient c, power acceleration g, oil specific weight γ, valve oil supply port opening area Si, and oil drain port opening area SD are:
The oil supply flow rate Qi and the oil drain flow rate QD are: QD=c・SD[2g Pp)/γ] ^1/2 =a・SD(Pp) ^1/2 Qi=a・Si(PL−Pp) ^1/2 [a = c(2g/γ) ^1/2 ]. Therefore, if the duty ratio is D, the average flow rate Q for one cycle of the duty operation signal (assuming lubrication is positive) is: Q=aA{D・Si(PL−Pp) ^1/2 −(1−D) ×SD( Pp) ^1/2 }, and if a, Si, and SD are constants, the following formula is obtained. Q=f3 (D, PL, Pp) Here, the line pressure PL is controlled by the gear ratio i and the engine torque T. Since the primary pressure Pp is determined by the gear ratio i and the line pressure PL, T
Assuming that is constant, Q=f4(D,i), and the following equation holds true. di/dt=f5(D,i) Therefore, when solving for D, we get D=f6(di/dt,i). From the above, it can be seen that the shift speed di/dt corresponds to the duty ratio D. The duty ratio D is determined by the speed change speed di/dt and the speed change ratio i. On the other hand, the gear shift speed di/dt is the target gear ratio in steady state.
Since it is based on the deviation between is and the actual gear ratio i, the following equation holds true. di/dt=k(is-i) As described above, the shift speed di/dt is calculated from the deviation between the target gear ratio is and the actual gear ratio i, and the duty ratio D is set according to this shift speed di/dt. Ru. Further, in the case of an upshift, the value of the shift speed di/dt becomes negative when is<i, and in the case of a downshift, the value of the shift speed di/dt becomes positive when is>i. Therefore, when the shift speed di/dt is negative, the duty ratio D is increased, and a value corresponding to di/dt is set in the direction where the duty ratio D is large. Shift speed di/
When dt is positive, conversely, the duty ratio D is decreased, and a value corresponding to di/dt is set in the direction of decreasing the duty ratio D. This makes it possible to shift up or down according to the value of the duty ratio D of the electric signal, and to control the speed change according to di/dt. Further, (is-i) corresponds to the change ΔTe in the engine torque, and the coefficient k represents the driver's intention to accelerate. Therefore, by making the coefficient k variable according to changes in engine load, the shift speed di/dt during acceleration can be
is calculated appropriately. Furthermore, transient states and various operating states other than steady state and acceleration can be dealt with by correcting the shift speed based on the steady state. Therefore, the electrical control system shown in FIG. 2 is constructed based on the above-mentioned principle, and will be explained below. First, the primary pulley rotation speed sensor 41 detects the primary pulley rotation speed Np, the secondary pulley rotation speed sensor 42 detects the secondary pulley rotation speed Ns, the engine rotation speed sensor 43 detects the engine rotation speed Ne, and the throttle opening θ.
It has a throttle opening sensor 44 that detects.
These sensor signals are input to unit 40. The transmission speed control system in the control unit 40 will be explained. It has an actual gear ratio calculation means 45 which inputs the primary pulley rotation speed Np and the secondary pulley rotation speed Ns, and calculates the actual gear ratio i by i=Np/
Calculated by Ns. Further, the secondary pulley rotation speed Ns and the throttle opening θ are input to the target gear ratio search means 46, and the target gear ratio is
Search for. On the other hand, the throttle opening degree θ is input to the acceleration detecting means 51, and a change in the throttle opening degree is calculated by dθ/dt. This throttle opening change dθ/dt is input to the coefficient setting means 47, and a coefficient k is set as an increasing function of the throttle opening change dθ/dt. The actual gear ratio i, the target gear ratio is at steady state, and the coefficient k are input to the gear shifting speed calculation means 48, and the target shifting speed di/dt is calculated by di/dt=k(is-i). do. Further, if the sign of the shift speed di/dt is positive, it is determined to be a downshift, and if it is negative, it is determined to be a shift up. Coefficient setting means 4 is used for correction at the time of kickdown.
A coefficient correction means 55 is attached to the output side of 7, and the target gear ratio is and the actual gear ratio i are input thereto. The coefficient correction means 55 compares the deviation (is-i) between the target gear ratio and the actual gear ratio during acceleration with a set value A, and determines whether there is a kickdown in full-throttle acceleration. and is-i>A
In the case of a knockdown, the coefficient k is corrected by decreasing it by several percent. The target speed change speed di/dt and actual speed change ratio i are further inputted into the duty ratio search means 49, and the results are shown in FIG. 3c.
The duty ratio D as the manipulated variable is searched from the di/dt-i table. In the table, when the shift speed di/dt is positive, the larger di/dt is, the smaller the value of the duty ratio D is set, and when the shift speed di/dt is negative,
The larger the absolute value of di/dt is, the larger the value of duty ratio D is set. Also, if di/dt is negative,
The larger the actual gear ratio i, the smaller the value of the duty ratio D is set, and if di/dt is positive, the actual gear ratio i
The larger the value of the duty ratio D is set, the larger the value of the duty ratio D is set. In this way, the duty ratio D is searched using the three-dimensional table of di/dt, i, and D. Then, the electric signal of the duty ratio D searched by the duty ratio search means 49 is outputted to the solenoid valve 28 via the drive means 50. Next, the line pressure control system will be explained. First, the engine speed Ne, throttle opening θ, and actual gear ratio i are input to the target line pressure calculation means 52, and the target line pressure PLt is calculated based on the engine speed Ne, the engine torque T based on the throttle opening θ, and the actual gear ratio i. Calculate. The target line pressure PLt is input to the duty ratio setting means 53, and the target line pressure PLt
The larger the value, the larger the duty ratio D is set. Then, an electric signal with a duty ratio D is outputted to the solenoid valve 27 via the driving means 54. Next, the operation of this embodiment will be explained. First, the oil pump 2 is activated by the operation of the engine 1.
1 is driven, the line pressure PL of the oil passage 21 is supplied only to the secondary cylinder 10, and the gear ratio is set to the maximum low gear. At this time, the oil at the line pressure PL is taken out into the oil passage 26 with the flow rate restricted by the orifice 32a, and the pressure is regulated by the regulator valve 25 to generate the regulator pressure PR.
is guided to solenoid valves 27, 28, etc., making it possible to electronically control line pressure and speed change. Further, signals of the primary pulley rotation speed Np, the secondary pulley rotation speed Ns, the throttle opening θ, and the engine rotation speed Ne are input to the control unit 40. Then, in the line pressure control system, the target line pressure PLt is calculated from the actual gear ratio i calculated from the primary pulley rotation speed Np and the secondary pulley rotation speed Ns, the engine torque T from the engine rotation speed Ne and the throttle opening θ, and this target Line pressure PLt
The duty ratio D is set accordingly. Therefore, if the engine torque T increases during starting or acceleration, the target line pressure PLt will be calculated to be large.
A signal with a large duty ratio D is sent to the solenoid valve 27.
Output to. Therefore, the amount of oil discharged from the solenoid valve 27 increases and is converted to a lower duty pressure Pd.
This duty pressure Pd is introduced into the line pressure control valve 22, and the line pressure PL is controlled to be high. Furthermore, as the vehicle speed increases, shift control is started and the actual gear ratio i becomes smaller, and when the engine torque T also becomes smaller, the duty ratio D becomes smaller. Therefore, in the solenoid valve 27, the duty pressure Pd increases as the amount of discharged oil decreases, and in the line pressure control valve 22, the line pressure PL is sequentially controlled to be lower. In this way, the line pressure PL is continuously electronically controlled to be lower as the actual gear ratio i is smaller, and higher as the engine torque T is larger. By constantly introducing this line pressure PL into the secondary cylinder 10 and acting on it, the minimum necessary pulley pressing force that does not cause belt slip is always applied. On the other hand, in the speed change control system, the throttle opening θ
The target gear ratio is determined by the and secondary pulley rotation speed Ns.
is is set. Then, the target gear speed di/
dt is calculated, and the duty ratio D is set based on the relationship between the target speed change speed di/dt and the actual speed change ratio i.
The electric signal of the duty ratio D is output to the solenoid valve 28 and converted into duty pressure Pd, and this duty pressure Pd is introduced into the control port 23a of the speed change control valve 23, and the lubrication is performed by turning the duty pressure Pd on and off. Operates repeatedly in two positions for draining oil. At this point, by decreasing the vehicle speed or stepping on the accelerator,
When it reaches i, the duty ratio D is set in the smaller direction. For this reason, the shift speed control valve 23 operates for a longer time in the oil draining position, and the primary cylinder 9 is drained of more oil than it is filled with oil, and the primary pressure Pp decreases, resulting in a downshift. At this time, the duty ratio D is sequentially set according to the shift speed di/dt calculated from the deviation between the target gear ratio is and the actual gear ratio i, and the amount of oil discharged is varied by the duty ratio D. For this reason, the actual gear ratio i, which is larger than the target gear ratio is, which is set to a large value, follows the target gear ratio is with a slope corresponding to the gear shift speed di/dt. In other words, if the initial deviation is large, the actual gear ratio i will quickly follow the shifting speed with a large slope, and as the deviation gradually decreases, the slope will become smaller, and the shifting speed will slow down and shift smoothly so that overshoot does not occur. Converge. Conversely, when is < i due to an increase in vehicle speed or release of the accelerator, the duty ratio D is set toward a larger value. Therefore, the shift speed control valve 23 operates for a longer time in the refueling position, and the primary cylinder 9
is filled with more oil than the drained oil, increasing the primary pressure Pp and shifting up. In this case, the actual gear ratio i is larger than the target gear ratio is, which is set to a smaller value.
However, in the same way as described above, the shift speed is changed to quickly follow and converge smoothly. Also, both upshifting and downshifting,
According to the duty ratio D according to the actual gear ratio i, the higher the speed, the more oil is supplied and drained, and the primary cylinder 9 is always maintained.
becomes the oil amount commensurate with the actual gear ratio i. In this way, the target shift speed di/dt is calculated according to the driving and running conditions, and an electric signal with a duty ratio D based on this shift speed di/dt and the actual speed ratio i is output for closed loop control. Then, the shift speed di/dt is varied as a control target by the duty signal, and the shift is controlled by shifting up or down over the entire shift range. On the other hand, when accelerating by pressing the accelerator, the acceleration state is detected based on the throttle opening change dθ/dt, and the coefficient k is set according to the throttle opening change dθ/dt. Therefore, during sudden acceleration, the coefficient k becomes a large value and the value of the shift speed di/dt also becomes a large positive value. Therefore, by downshifting as described above, the target gear ratio is
The shift speed when the actual gear ratio i follows becomes even faster, and the downshift is performed quickly. During this acceleration, the value of the target gear ratio is is set to be very large compared to the actual gear ratio i, and is−i>
When the condition A is satisfied, the coefficient correcting means 55 determines that the kickdown is full throttle acceleration. In the case of a kickdown, the coefficient k is corrected to a smaller value, so that the value of the shift speed di/dt also becomes smaller. Therefore, as shown by the broken line in Figure 3a, even though the deviation of is-i is large, downshifting is started smoothly at a slow shift speed, and the engine speed and acceleration of the vehicle body increase almost simultaneously. . In the process of downshifting toward a low speed gear, when is-i<A, the original coefficient k corresponding to the acceleration state is output from then on. Therefore, the value of the shift speed di/dt also increases, resulting in a rapid downshift. Although one embodiment of the present invention has been described above,
It goes without saying that the process is not limited to the above embodiment, and can also be processed using software using a microcomputer.

【Effect of the invention】

As explained above, according to the present invention, in a control device that electronically controls speed change in a continuously variable transmission,
The control unit is configured to calculate a target gear shift speed based on the deviation between the target gear ratio and the actual gear ratio, and to perform open loop control by setting the manipulated variable of the electrical signal based on the target gear shift speed and the actual gear ratio. Therefore, it is possible to directly control the speed change so that it follows quickly and converges smoothly. This improves responsiveness during transients and reduces overshoot. Control is also much easier. Since the signal oil pressure generated by the electric signal is introduced into the control port of the speed change control valve and operates repeatedly between the two positions of oil supply and oil drain, the primary pressure can be increased or decreased while changing the speed change depending on the amount of operation of the electric signal. Therefore, the speed change speed can be controlled accurately. During full-throttle acceleration, the shift speed is corrected to decrease and the shift down is performed smoothly, thereby avoiding a shift shock and suppressing a sudden increase in engine speed alone, improving acceleration performance. Since the coefficient set according to the acceleration state is corrected to decrease, control is easy and it is possible to easily return to the speed change control in the acceleration state. The shift speed correction is temporary immediately after the shift down, and since the shift speed is shifted down at a faster shift speed thereafter, the performance of full-throttle acceleration is not impaired.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the hydraulic control system of the continuously variable transmission and control device of the present invention, and FIG. 2 is a block diagram showing an embodiment of the electrical control system of the control device of the continuously variable transmission of the present invention. FIG. 3A is a diagram showing a shift pattern, b is a table of target gear ratios, and c is a diagram showing a table of duty ratios. 4...Continuously variable transmission, 5...Main shaft, 11...Drive belt, 6...Subshaft, 7...Primary pulley,
8... Secondary pulley, 9... Primary cylinder, 10... Secondary cylinder, 21, 26
... Oil passage, 22 ... Line pressure control valve, 23 ... Speed change control valve, 23a, 23b ... Control port,
23c... Spring, 32a... Orifice,
28... Solenoid valve, 40... Control unit,
45...actual gear ratio calculation means, 46...target gear ratio search means, 47...coefficient setting means, 48...shift speed calculation means, 49...duty ratio search means,
55... Coefficient correction means.

Claims (1)

[Scope of Claims] 1 A primary pulley with variable pulley spacing is provided on the main shaft on the engine side, a secondary pulley with variable pulley spacing is provided on the subshaft on the wheel side, which is arranged parallel to the main shaft, and a driving pulley is provided between the two pulleys. A line pressure control valve is provided on the oil path from the hydraulic source around which the belt is wound, which controls line pressure and supplies the line pressure to the cylinder of the secondary pulley to apply pulley pressing force, and the line pressure is applied to the cylinder of the primary pulley. A variable speed control valve that changes the primary pressure by supplying and discharging line pressure to the oil passage is installed, and the primary pressure changes the ratio of the winding diameter of the drive belt to both pulleys to continuously change the speed. In the transmission, the speed change control valve 23 has control ports 23a, 23b and a spring 23c that operate to switch between an oil supply position and an oil drain position, and has oil branched from the line pressure oil passage 21 via a flow rate restriction means 32a. The passage 26 communicates with the solenoid valve 28 to generate a signal oil pressure according to the electric signal from the control unit 40, and this signal oil pressure is introduced into the control port 23a of the speed change control valve 23 through the oil path 34 to control the speed change and the speed change. The control unit 40 includes means 45 for calculating the actual gear ratio based on the primary pulley rotation speed and secondary pulley rotation speed, and means 46 for determining the target gear ratio based on the throttle opening and the secondary pulley rotation speed.
and means 47 for setting a coefficient according to the acceleration state.
, means 52 for reducing the coefficient when the deviation between the target gear ratio and the actual gear ratio is equal to or greater than a set value, and calculating a target gear change speed from the deviation between the target gear ratio and the actual gear ratio and the corrected coefficient. A control device for a continuously variable transmission, comprising means 48 and means 49 for determining a manipulated variable based on the relationship between a target gear speed and an actual gear ratio and outputting an electrical signal of the manipulated variable.