JP2796568B2 - Control device for continuously variable transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a control device for electronically controlling a shift and the like in a belt-type continuously variable transmission for a vehicle, and more particularly, to a fail-safe in the event of a failure of a shift control solenoid valve and a harness thereof.

[Prior art]

As a control of this type of continuously variable transmission, a method of electrically processing various input signals, operating each solenoid valve for speed change control and line pressure control with an electric signal, and performing speed change and line pressure control has already been proposed. Have been. If the shift control solenoid valve and its harness break down due to disconnection or the like in such an electronic control system, the shift control is inevitably disabled, causing various problems. Therefore, conventionally, as for fail-safe at the time of failure of the shift control solenoid valve or the like, for example, JP-A-60-249761
There is a prior art in Japanese Patent Publication No. Here, an abnormality detection device is provided for the solenoids of the shift direction switching valve and the shift speed control valve. In the case of abnormality detection, both solenoids are de-energized, and the shift-up switching position is regulated, for example, to a shift-up side position to suppress the shift-up speed.

[Problems to be solved by the invention]

By the way, in the above-mentioned prior art, a sudden change in the gear ratio can be avoided by substantially restricting the gear stage at that time when the solenoid fails. However, even in the case of such a failure, it is necessary to secure the minimum required traveling of the vehicle, but in this regard, it is restricted only to the upshift side,
It is difficult to travel continuously in response to changes in road surface conditions. In addition, since the abnormality detection device is a hardware-like circuit using a plurality of transistors, the structure is complicated by the amount of the circuit, and a failure easily occurs. For this reason, it is desired that failure detection be performed by finding a state that cannot be controlled by normal control and making a software decision, in terms of simplification of the structure and the like. In the event of a failure, it is necessary to return to the maximum gear ratio or the like to ensure stable running. In this case, it is desired to avoid the engine braking effect due to a sudden downshift. The present invention has been made in view of such a point,
The purpose thereof is to provide a control device for a continuously variable transmission capable of determining a malfunction of a shift control solenoid valve or the like in a shift manner and, in the event of a malfunction, avoiding a sudden action of an engine brake and ensuring stable running. Is to provide.

[Means for Solving the Problems]

In order to achieve the above object, the control device for a continuously variable transmission according to the present invention determines a state where normal shift control cannot be performed as a failure of a shift control solenoid valve or the like. That is,
When the solenoid valve fails, the primary pulley rotation speed Np and the target primary pulley rotation speed Np
A first change amount calculating unit for calculating the change amount of D, a comparison between the primary pulley rotation speed Np and the primary pulley rotation speed maximum value Npm on the shift control map, or a change dNp / dt of the primary pulley rotation speed and a target Np> Npm or dNp / dt> dNp
A failure determination unit is provided for determining that a failure has occurred when the D / dt state has continued for a predetermined time or more. In the case where the actual speed ratio i is controlled to follow the target speed ratio is, a second change amount calculating unit for calculating a change amount between the actual speed ratio i and the target speed ratio is provided. Since the change dis / dt in the target gear ratio is larger than the change di / dt in the ratio, it is also determined that a failure has occurred when dis / dt <di / dt. Further, if the state of d (i-is) / dt> 0 continues for a certain period of time without following the actual speed ratio i during the upshift of i> is, it is determined that a failure has occurred. When a failure is determined under any of the above conditions, the engine is immediately disconnected.

[Action]

According to the above configuration, if the shift control solenoid valve or the like breaks down when the vehicle travels while performing shift control, the downshift is suddenly made to the maximum gear ratio side due to non-energization. Then, the primary pulley rotation speed Np, the change in the primary pulley rotation speed dNp
/ dt, the change in the actual gear ratio, di / dt, or d (i−i
s) Since a state of / dt> 0 occurs, these change amounts are calculated by the first and second change amount calculation units, and the output signals from the first and second change amount calculation units are input. Thus, a failure of the solenoid valve or the like is determined by the failure determination unit. When the failure determination unit determines that a failure has occurred, the output signal from the failure determination unit is input to the clutch release unit, and the output signal from the clutch release unit immediately controls the disconnection of the continuously variable transmission from the engine. As a result, the engine brake does not work and the vehicle simply coasts. At this time, the continuously variable transmission returns to the maximum gear ratio, and when the vehicle is substantially stopped, the vehicle is connected to the engine again, so that the vehicle can be reliably driven at the maximum gear ratio.

【Example】

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, the overall configuration of a drive system in which a belt-type continuously variable transmission is combined with an electromagnetic clutch will be described. The engine 1 is connected to a continuously variable transmission 4 via an electromagnetic clutch 2 such as an electromagnetic powder type and a forward / reverse switching device 3, and is connected to the continuously variable transmission 4 from the continuously variable transmission 4.
The transmission gears are configured to be transmitted to drive wheels 9 via a set of reduction gears 5, output shafts 6, differential gears 7, and axles 8. The electromagnetic powder type clutch 2 has a drive member 2a on an engine crankshaft 10 and a driven member 2b having a clutch coil 2c on an input shaft 11. And clutch coil 2c
The electromagnetic powder is coupled and accumulated in the gap between the two members 2a and 2b in a chain by the clutch current flowing through the clutch, and the clutch engagement / disengagement and clutch torque are variably controlled by the coupling force. The forward / reverse switching device 3 is synchronously meshed with a gear, a hub, and a sleeve between the input shaft 11 and the transmission main shaft 12, and includes a forward position at which the input shaft 11 is directly connected to the main shaft 12, and an input shaft. And a retracted position for transmitting the rotation of the rotation 11 to the main shaft 12 in the reverse direction. The continuously variable transmission 4 includes a main shaft 12 and a sub shaft arranged in parallel with the main shaft 12.
The primary shaft 12 is provided with a primary pulley 14 having a hydraulic cylinder 14a having a hydraulic cylinder 14a and the secondary shaft 13 is similarly provided with a secondary pulley 15 having a hydraulic cylinder 15a. A drive belt 16 is wound around both pulleys 14 and 15, and both cylinders 14a and 15a are configured as a hydraulic control circuit 17. A line pressure corresponding to the transmission torque is supplied to both cylinders 14a and 15a to apply a pulley pressing force, and the primary pressure changes the ratio of the winding diameter of the drive belt 16 to the pulleys 14 and 15 to continuously change the speed. It is configured to control. Next, an electronic control system of the electromagnetic powder type clutch 2 and the continuously variable transmission 4 will be described. Engine speed sensor 19 for engine 1 and primary pulley speed sensor 2 for continuously variable transmission 4
1, a secondary pulley rotation speed sensor 22, and sensors 23 and 24 for detecting the operation status of the air conditioner and the choke. Also,
The shift lever 25 of the operation system is mechanically coupled to the forward / reverse switching device 3, and has a shift position sensor 26 for detecting each range of reverse (R), tribe (D), and sporty drive (Ds). Further, the accelerator pedal 27 has an accelerator switch 28 for detecting an accelerator depression state,
A throttle opening sensor 29 is provided on the throttle valve side. The various signals of the switches and the sensors are input to the electronic control unit 20 and processed by software using a microcomputer or the like. The clutch control signal output from the electronic control unit 20 is input to the electromagnetic clutch 2 and the shift control signal and the line pressure control signal are input to the hydraulic control circuit 17 of the continuously variable transmission 4 to perform each control operation. I have. 2, the electromagnetic clutch control system and the continuously variable transmission control system of the control unit 20 will be described. First, the electromagnetic clutch control system includes a reverse excitation mode determination unit 32 to which signals in the parking (P) and neutral (N) ranges other than R, D, and Ds of the engine speed Ne and the shift position sensor 26 are input. For example, if Ne <300 rpm,
Alternatively, in the case of the P and N ranges, the mode is determined to be the reverse excitation mode, and the output determining unit 33 allows a small current to flow in a direction opposite to the normal direction. Then, the electromagnetic clutch 2 is completely released except for the residual magnetism.
Further, there is provided an energization mode determination unit 34 to which a determination output signal of the reverse excitation mode determination unit 32, a depression signal of the accelerator switch 28, and a rotation (hereinafter referred to as vehicle speed V) signal of the secondary pulley rotation speed sensor 22 are input. And the like, and the discrimination signal is input to the start mode current setting unit 35, the drag mode current setting unit 36, and the direct connection mode current setting unit 37. The start mode current setting unit 35 sets the start characteristics individually in relation to the engine speed Ne and the like in the case of normal start or start using the air conditioner and choke. Then, the starting characteristics are corrected based on the travel ranges of the throttle opening θ and the vehicle speeds V, R, D, and Ds, and the clutch current is set. The drag mode current setting unit 36 determines a small drag current when the accelerator is released at a low vehicle speed in each range of R, D, and Ds,
A drag torque is generated in the electromagnetic clutch 2 to reduce the play of the belt and the drive system, thereby smoothly starting the vehicle. In this mode, the current is determined to be zero current until just before the vehicle stops after the clutch in the D range is released, thereby ensuring the coasting. The direct-coupling mode current setting unit 37 determines the direct-coupling current based on the relationship between the vehicle speed V and the throttle opening θ in each of the R, D, and Ds ranges, completely connects the electromagnetic clutch 2, and saves power in the engaged state. The output signals of these current setting units 35, 36, and 37 are input to the output determination unit 33, and the clutch current is determined according to the instruction. Next, regarding the shift speed control system of the continuously variable shift control, the primary pulley speed Np and the secondary pulley speed Ns of the primary pulley speed sensor 21 and the secondary pulley speed sensor 22 are input to the actual speed ratio calculating unit 40. , The actual speed ratio i is calculated from the actual speed ratio i = Np / Ns. The actual gear ratio i and the throttle opening θ of the throttle opening sensor 29
The shift positions R, D, and Ds of the shift position sensor 26 are input to the target primary pulley rotation speed search unit 41, and a target primary pulley is determined using an i-θ map based on a shift pattern for each of the R, D, and Ds ranges. The pulley rotation speed NPD is searched. The target primary pulley rotation speed NPD and the secondary pulley rotation speed Ns are input to the target gear ratio calculator 42, and the target gear ratio is is = NPD
It is calculated by / Ns. Then, the target speed ratio is input to the target speed ratio change speed calculating section 43, and the target speed ratio change speed dis / dt is calculated based on the amount of change of the target speed ratio is for a certain period of time. The actual gear ratio i, the target gear ratio is, the target gear ratio change speed dis / dt, and the coefficients K ₁ and K ₂ of the coefficient setting unit 44 are input to the gear speed calculator 45, and the gear speed di / dt is calculated. It is calculated as follows. di / dt = K ₁ (is−i) + K ₂ · dis / dt In the above equation, is−i is a control amount of the target and actual speed ratio deviation, and dis / dt is a delay correction element of the control system. The gear speed di / dt and the actual gear ratio i are the duty ratio search units.
Enter 46. Here, the duty ratio D of the manipulated variable is D
= F (di / dt, i), the duty ratio D becomes di / dt in upshift and downshift.
-Searched using the map of i. The value of the duty ratio D of the manipulated variable is supplied to the hydraulic control circuit
Output to the 17 speed change control solenoid valve 48. Subsequently, a line pressure control system of the continuously variable transmission control will be described. Engine speed sensor 19, throttle opening sensor 29
And an engine torque search unit 50 to which the engine speed Ne and the throttle opening θ are inputted, and obtains the engine torque T from the torque characteristic map of θ-Ne. This engine torque T
The signal of the actual gear ratio i of the actual gear ratio calculator 40 is input to the target line pressure setting unit 51, and the target line pressure PLd is determined by the product of the required line pressure corresponding to the engine torque and the actual gear ratio i. On the other hand, since the maximum value of the line pressure fluctuates as the pump discharge pressure changes depending on the engine speed, the maximum line pressure search unit 52 for inputting the engine speed Ne and the actual speed ratio i to detect this fluctuation state. And the maximum line pressure PLmax is obtained from the Ne-i map. The target line pressure PLd and the maximum line pressure PLmax are input to the pressure reduction value calculation unit 53, and the line pressure P is calculated as a ratio of the target line pressure PLd to the maximum line pressure PLmax.
LR is calculated, and this is input to the duty ratio search unit 54 to determine the duty ratio D according to the line pressure PLR. The duty signal is output to the line pressure control solenoid valve 56 via the drive unit 55. Therefore, a fail-safe operation for the solenoid valve 48 and a failure such as a disconnection of a harness in the control system will be described. First, there are various methods for failure diagnosis. To summarize these, the primary pulley rotation speed Np of the primary pulley rotation speed sensor 21 and the maximum primary pulley rotation speed Npm on the map are input to the failure determination unit 60. , Np> Npm +
If n (n is a constant value), it is determined that a failure has occurred. The primary pulley rotation speed Np and the target primary pulley rotation speed NpD are input to the first change amount calculation unit 61, and a change dNp / dt in the primary pulley rotation speed and a change dN in the target primary pulley rotation speed are input.
pD / dt is calculated, and these are input to the failure determination unit 60, and d
If Np / dt> dNpD / dt, it is determined that a failure has occurred. The actual speed ratio i and the target speed ratio is also input to the second change amount calculator 62, and the actual speed ratio change di / dt and the target speed ratio change dis / dt are calculated. And di / dt> dis / d
In the case of t, it is determined that a failure has occurred. The actual speed ratio i and the target speed ratio is input to the failure determination unit 60, and a failure is similarly determined when d (i-is) / dt> 0 during an upshift of i> is. The failure determination unit 60 outputs a failure signal under any of the above conditions.
63, and outputs a zero current to the output determination unit 33 when the vehicle speed is equal to or higher than the set vehicle speed. Next, the operation of the thus configured shift control device for a continuously variable transmission will be described. First, power corresponding to the depression of the accelerator from the engine 1 is input to the primary pulley 14 of the continuously variable transmission 4 via the electromagnetic clutch 2 and the forward / reverse switching device 3, and the drive belt 16,
The power is shifted by the secondary pulley 15 and is transmitted to the drive wheels 9 to travel. During the traveling, the target line pressure is set to be larger as the engine torque T is larger in a low speed stage where the value of the actual speed ratio i is larger, and a corresponding duty signal is input to the solenoid valve 56 to generate a control pressure. The line pressure PL is increased by controlling the line pressure with the averaged pressure. Then, as the gear ratio i becomes smaller and the engine torque T becomes smaller as the gear shifts to the higher gear, the line pressure PL is controlled so as to decrease in the same manner, so that the transmission by the drive belt 16 is always performed. A pulley pressing force corresponding to the torque acts. The line pressure PL is always supplied to the secondary cylinder 15a, and the transmission speed is controlled by supplying and discharging oil to and from the primary cylinder 14a by a transmission speed control valve (not shown) by the control pressure of the solenoid valve 48. Will be described below. First, the signals Np, Ns, and θ from the primary pulley rotation speed sensor 21, the secondary pulley rotation speed sensor 22, and the throttle opening sensor 29 are read, and the actual gear ratio calculation unit 40 of the control unit 20 obtains the actual gear ratio i. . The target primary pulley rotation speed search unit 41 once searches the map for the target primary pulley rotation speed NPD based on the actual gear ratio i and the throttle opening θ, and the target gear ratio calculation unit 42 corresponds to the target primary pulley rotation speed NPD. The calculated target gear ratio is is calculated. Therefore, in the region where the primary pulley rotation speed is constant, the target speed ratio is has the same fixed value as calculated by the Ns-θ method, but in the region where the primary pulley rotation speed is variable, the target speed ratio is Ns−. As compared with the value calculated by the θ method, it is set to be offset toward the lower gear, and the target speed ratio is a value that changes by itself. Using the actual gear ratio i, the target gear ratio is, the dis / dt of the target gear ratio change speed calculator 43, and the coefficients K ₁ and K ₂ of the coefficient setting unit 44, the gear speed calculator 45 uses the gear speed di / dt. Ask for. Then, the duty ratio search unit 46 searches the duty ratio D based on the shift speed di / dt and the actual speed ratio i. The duty signal is input to a solenoid valve 48 to generate a pulse-like control pressure, whereby the shift speed control valve is repeatedly operated at two positions of oil supply and oil discharge. Here, when the duty ratio becomes small, the operation time at the refueling position becomes longer due to the off time, and the primary cylinder
Refueling at 14a, thus upshifting. On the other hand, when the duty ratio increases, the operating time at the oil discharge position becomes longer due to the on-time, and the primary cylinder 14a is drained, thereby causing a downshift.
Since the shift speed di / dt in this case corresponds to a change in the duty ratio, when the deviation between the target speed ratio is and the actual speed ratio i is small, the change in the duty ratio is small and the flow rate change of the primary cylinder 14a is small. The gear speed is slowed down due to the small number of gears. On the other hand, as the deviation between the target speed ratio is and the actual speed ratio i increases, the change in the duty ratio causes the flow rate change of the primary cylinder 14a to increase, and the speed change speed increases. In this way, in the entire shift range of the low-speed gear and the high-speed gear, the upshift or downshift is performed while changing the shift speed, and the gear is continuously changed. Next, the operation at the time of failure of the shift control solenoid valve 48 and the like will be described with reference to the flowchart of FIG. First, a change dNp / dt between the primary pulley rotation speed Np and the primary pulley rotation speed during the shift control, and a change d between the target primary pulley rotation speed NpD and the target primary pulley rotation speed d
NpD / dt, actual gear ratio i and change in actual gear ratio di / dt, target gear ratio i
The value of s and the change dis / dt of the target gear ratio are input to the failure determination unit 60 and determined. Therefore, in the normal case, Np ≦ Npm. Further, since the shift control is performed so that the primary pulley rotation speed Np follows the target primary pulley rotation speed NpD and the actual speed ratio i follows the target speed ratio is, the target primary pulley rotation speed NpD and the target speed ratio is The change in the target primary pulley speed dNpD / dt and the change in the target gear ratio dis / dt are always the change in the primary pulley speed dNp / dt and the change in the actual speed ratio in both upshift and downshift. Make it larger than / dt. Further, at the time of an upshift of i> is, i-is = 0 because the actual speed ratio i follows the target speed ratio is. Therefore, all are judged to be normal when the failure condition is not satisfied. On the other hand, if disconnection of the solenoid valve 48 or the harness, clogging of the drain port of the solenoid valve 48, or failure of the spool stick, the stick on the control valve side, the duty signal 0% hold, etc. occurs, the solenoid valve 48 is de-energized or A similar state is established, and the gear ratio is fixed at the maximum gear ratio or rapidly downshifted to that gear ratio. For this reason, despite the target primary pulley rotation speed NpD and the target speed ratio is small on the high speed side, the primary pulley rotation speed Np, the actual speed ratio i, and the change in the primary pulley speed dNp / d
t, the change in the actual transmission ratio, di / dt, increases rapidly, and Np
> Npm + n. Further, during shifting, when traveling at the minimum speed ratio, d / d> dis / dt, dNp / dt> dNpD / dt, i> is
Any one of the conditions of (i-is) / dt> 0 is satisfied, whereby the failure determination unit 60 determines that a failure has occurred. Then, the zero current by the clutch release unit 63 flows to the electromagnetic clutch 2 by the output determination unit 33 of the clutch control system, and the electromagnetic clutch 2 is immediately released. Then, the engine 1 is disconnected and the engine brake is not effective. On the other hand, in the continuously variable transmission 4, when the solenoid valve 48 is not energized, the primary pressure is drained and the operation is performed to the maximum gear ratio side. The gear ratio returns to the above, and the vehicle coasts in this state. The vehicle stops due to the coasting, and at this stop, the output of the clutch release unit 63 disappears and the clutch control system returns. With this operation, the driver notices the failure and depresses the accelerator in order to move to the optimum location. When the starter mode current setting unit 35 of the clutch control system gradually engages the electromagnetic clutch 2, then the direct connection mode current setting unit 37 As a result, a direct connection current flows, and the electromagnetic clutch 2 is held in the engaged state. Then, the power of the engine 1 is transmitted to the electromagnetic clutch 2 and thereafter. At this time, since the continuously variable transmission 4 is held at the maximum speed ratio, the minimum traveling is performed only at that speed ratio. The embodiment of the present invention has been described above. However, the present invention is not limited to this, and can be applied to an automatic clutch other than an electromagnetic clutch. In the case of a torque converter type CVT, the forward / reverse switching device may be controlled to the neutral position.

【The invention's effect】

As described above, according to the present invention, the electronic control system of the continuously variable transmission determines the failure of the shift control solenoid valve or the like based on unusual changes in various elements. It is unnecessary and can be easily processed in software. When changes in the primary pulley rotation speed, actual gear ratio, and gear ratio deviation are used, both upshifts and downshifts can be applied, and a failure can be determined quickly. In the event of a failure, problems caused by engine braking can be avoided by releasing the clutch or the like, and stable running at the maximum gear ratio can be ensured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a control device for a continuously variable transmission according to the present invention, FIG. 2 is a block diagram of a control system, and FIG. 3 is a flowchart of an operation. 4 ... continuously variable transmission, 20 ... electronic control unit, 48 ... shift control solenoid valve, 60 ... failure determination unit, 61 ... first
... A second change amount calculating section, 63... A clutch release section

Continuation of the front page (51) Int.Cl. ⁶ identification code FI F16H 59:46 (58) Fields investigated (Int.Cl. ⁶ , DB name) B60K 23/00 B60K 20/00 F16H 9/00 F16H 61 / 12

Claims (4)

(57) [Claims] A shift control solenoid valve which shifts to a low gear of a maximum gear ratio when no power is supplied, and controls the detected actual shift state to a target shift state calculated from a value on a control map. In the control system of the continuously variable transmission, when the detected primary pulley rotation speed becomes higher than the maximum primary pulley rotation speed on the control map, a failure determination unit that determines and outputs a failure, and the failure determination unit A control device for a continuously variable transmission, comprising: a clutch releasing portion for immediately disconnecting the continuously variable transmission from the engine side by an output from the engine. And a shift control solenoid valve that shifts to a lower gear of a maximum gear ratio when no power is supplied, and controls the detected actual shift state to a target shift state calculated from a value on a control map. In a control system of the continuously variable transmission, a failure determination unit that determines and outputs a failure when a state in which the detected change in the primary pulley rotation speed is higher than a target change in the primary pulley rotation speed continues for a certain period of time, A control device for a continuously variable transmission, comprising: a clutch release unit that immediately disconnects the continuously variable transmission from an engine side based on an output from a failure determination unit. 3. A shift control solenoid valve which shifts to a lower gear of a maximum gear ratio when no power is supplied, and controls the detected actual shift state to a target shift state calculated from a value on a control map. In the control system of the continuously variable transmission, a failure determination unit that determines and outputs a failure when a state in which the change in the actual gear ratio is higher than the change in the target gear ratio continues for a certain period of time; A control device for a continuously variable transmission, comprising: a clutch release portion for immediately disconnecting a stepped transmission from an engine side. 4. A shift control solenoid valve which shifts to a lower gear of a maximum gear ratio when no power is supplied, and controls the detected actual shift state to a target shift state calculated from a value on a control map. In the control system of the continuously variable transmission, if the change of the deviation between the actual gear ratio and the target gear ratio is larger than 0 in the upshift where the actual gear ratio is larger than the target gear ratio for a certain period of time, it is judged as a failure and the output is made. A control device for a continuously variable transmission, comprising: a failure determination unit that performs the operation; and a clutch release unit that immediately disconnects the continuously variable transmission from the engine according to an output from the failure determination unit.