JPH0532618B2 - - Google Patents

Description

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

The present invention relates to a turning control device for an automatic transmission for a vehicle, and more particularly, the present invention is configured to execute a downshift according to a predetermined shift map, and the downshift is performed during a predetermined run when the vehicle turns. The present invention relates to an improvement in a turning control device for a vehicle automatic transmission that is configured to be limited within a state range.

[Conventional technology]

A gear transmission mechanism and a plurality of frictional engagement devices are provided, and engagement of the frictional engagement devices is selectively switched by operating a hydraulic control device to shift gears according to a predetermined shift map. Automated vehicle transmissions configured to do this are already widely known. The shift map is normally determined based on the vehicle speed and engine load, and a specific gear stage is determined by detecting the vehicle speed and engine load. This speed change control is performed even when the vehicle is turning. However, when a gear shift is performed while turning, torque fluctuations or speed fluctuations occur, which not only gives the driver an unexpected sense of fear, but also causes sudden downshifts, especially when downshifting at a sharp curve. This may cause problems such as side slipping of the vehicle due to increased driving force. Conventionally, Japanese Patent Publication No. 48-9729 has been disclosed as a technique for solving this problem. That is, this technique is designed to stop the gear shift when the vehicle is turning, thereby preventing unexpected torque fluctuations by the driver. Furthermore, Utility Model Application Publication No. 61-154126 discloses a technology in which the downshift line of the transmission map is appropriately shifted to the lower vehicle speed side according to the steering angle, and the execution of the downshift in the shifted portion is essentially prohibited. is also disclosed.

[Problems to be solved by the invention]

However, in the above technique, there have been cases in which good results cannot always be obtained in terms of appropriateness of control. For example, a change in the output shaft torque of an automatic transmission is a factor that is directly linked to vehicle behavior.
In recent years, with the increase in engine output, the change in output shaft torque during downshift {= (difference in gear ratio) ×
(difference in engine torque)} tends to increase. Therefore, even when turning with the same radius, for example, when downshifting from 3rd gear to 1st gear and downshifting from 2nd gear to 1st gear, the shift of the automatic transmission will affect vehicle behavior. The impact will be different.
Also, even if the change in output shaft torque is the same, the output shaft torque when downshifted {= (gear ratio)
x (engine torque)} itself is different, the influence on vehicle behavior will also be different. That is, since the gear ratios are different between a downshift to the first gear and a downshift to the second gear, the vehicle behavior is different even if the change in output shaft torque accompanying the gear change is the same. The above is nothing but the fact that the type of gear change affects vehicle behavior. Even when turning with the same radius, the stability of vehicle behavior changes depending on the vehicle speed. Generally, as the vehicle speed increases, the lateral acceleration increases, so the behavior tends to become unstable. Furthermore, the rate at which changes in the output shaft torque affect vehicle behavior also changes depending on the vehicle speed. Furthermore, depending on the vehicle speed, oversteering,
Stability factors such as understeering also change. From the perspective of changes in engine torque,
It is well known that engine torque changes depending on the throttle opening (engine load). in general,
At low throttle opening, engine torque is low,
Therefore, even if the gear ratio is the same, the output shaft torque will be lower, so the effect of shifting will be small even when turning sharply. Therefore, even when turning at the same radius, the degree of influence on vehicle behavior differs depending on the throttle opening. Problems such as those mentioned above tend to become more and more noticeable as engines have become higher in output and torque in recent years. Such a problem arises when, for example, as in the technique disclosed in the above-mentioned Japanese Patent Publication No. 48-9729, downshift control is executed only under the condition that the steering angle is above a certain level, and when the speed change control is performed only under the condition that the steering angle is above a certain value, The gear change prohibition is not executed in the state area, or
Conversely, prohibition of shifting is executed even in a driving state region where prohibition is not required, resulting in problems such as poor acceleration and insufficient driving force. In addition, in the technology disclosed in Utility Model Application Publication No. 15426/1983, the method of shifting the downshift line was devised, but attention was paid to the type of gear shifting, especially the difference in vehicle speed at that time. No particular consideration was given to this, and both 2-to-1 downshifts at low vehicle speeds and 4-to-3 downshifts at high vehicle speeds were restricted in the same way. Therefore, the prohibition of the shift may not be executed in a driving state region where the prohibition of the shift should be executed, or conversely, the prohibition of the shift may be executed even though the prohibition of the shift is not required, resulting in poor acceleration and driving force. Problems such as shortages sometimes occurred.

[Purpose of the invention]

The present invention has been made in view of such conventional problems, and the present invention limits the region in which shifting to a low gear is restricted to the necessary and minimum region, thereby reducing instability caused by execution of a downshift. An object of the present invention is to provide a turning control device for an automatic transmission for a vehicle, which can secure maximum vehicle driving force while suppressing the occurrence of undesirable vehicle behavior. In addition to the above-mentioned Japanese Patent Publication No. 48-9729, for example, Japanese Patent Application Laid-Open No. 59-1999 has been published regarding the speed change control during turning of a vehicle.
Publication No. 192621, Publication No. 59-200840, Publication No. 59-
There is a technique disclosed in Publication No. 231249 and the like. However, these technologies attempt to actively downshift to a lower gear without performing normal gear change control in order to secure engine braking or driving force when turning, and are not suitable for real use. The purpose, structure, and operation of this invention are different from the technology that attempts to control downshifts that should be performed in normal gear change control in order to ensure steering stability.

[Means to solve the problem]

The present invention provides an automatic transmission for a vehicle configured to execute a downshift according to a predetermined vehicle speed-engine load shift map, and configured to limit execution of the downshift when the vehicle turns. In this turning control device, in order to realize the downshift restriction, a threshold value for determining whether to execute or prohibit a downshift is set depending on at least a steering angle, a vehicle speed, and an engine load. , by making the threshold regarding the engine load for downshift restriction different even when the steering angle is the same, depending on whether the type of downshift is a downshift between high speed gears or a downshift between low gear gears, The above objectives have been achieved.

[Operation and effects of the invention]

In the present invention, when setting the restriction area for downshifting when the vehicle turns, the steering angle, vehicle speed,
The engine load and the type of gear change in question are taken into consideration. Therefore, based on the magnitude of the steering angle, the driving condition range in which downshifting is prohibited is set accurately, taking into consideration differences in vehicle speed, engine torque, and gear ratio that are considered to affect vehicle behavior. be able to. Furthermore, when considering vehicle speed, the influence of stability factors such as understeer or oversteer, which are generally considered to depend on the steering angle and vehicle speed, and the influence of the magnitude of the vehicle's lateral acceleration can also be taken into account. can. More specifically, even if the steering angle is the same, the engine load-related threshold for downshift restriction is different between the case of downshifting between high speed gears and the case of downshifting between low speed gears, and the vehicle speed, It becomes possible to determine the optimal restriction area taking into consideration gear ratio, output torque, and other factors.

【Example】

Embodiments of the present invention will be described in detail below based on the drawings. First, FIG. 2 shows an overall outline of a vehicle automatic transmission to which this embodiment is applied. This automatic transmission includes a torque converter section 20 and an overdrive mechanism section 40 as its transmission section.
and an underdrive mechanism section 60 with three forward stages and one reverse stage. The torque converter section 20 includes a pump 21,
It is of a known type, comprising a turbine 22, a stator 23, and a lock-up clutch 24. The overdrive mechanism section 40 includes a sun gear 43, a ring gear 44, and a planetary pinion 4.
2 and a carrier 41, and the rotational state of this planetary gear system is controlled by a clutch C ₀ , a brake B ₀ , and a one-way clutch F ₀ . The underdrive mechanism section 60 includes two sets of planetary gears consisting of a common sun gear 61, ring gears 62, 63, planetary pinions 64, 65, and carriers 66, 67, and the rotational state of the two sets of planetary gears, Clutches C ₁ , C ₂ and brakes are connected to the overdrive mechanism.
It is controlled by B ₁ to B ₃ and one-way clutches F ₁ and F ₂ . Since this transmission section itself is well known, the specific state of connection of each component will only be shown in a skeleton diagram in FIG. 2, and detailed explanation will be omitted. This automatic transmission includes a transmission section as described above and a computer 84. The computer 84 includes a throttle sensor 80 that detects the throttle opening which reflects the load condition of the engine 1, a vehicle speed sensor (rotational speed sensor of the output shaft 70) 82 that detects the vehicle speed, and a steering angle that detects the steering angle. Each signal from the steering angle sensor 99 and the like is input. As a result, the solenoid valves S ₁ and S ₂ (for shift valves) and SL (for lock-up clutch) in the hydraulic control circuit 86 are driven and controlled according to the shift map preset by the computer 84. The combination of engagement of each clutch, brake, etc. as shown in FIG. 3 is performed to perform speed change control. In this case, based on the steering angle signal from the steering angle sensor 99, the vehicle speed signal from the vehicle speed sensor 82, the throttle opening signal from the throttle sensor 80, and the type of shift that can be directly grasped in the computer 84,
Downshift prohibition control is executed in a predetermined driving condition region based on a map showing conditions for starting and canceling prohibition control as shown in FIG. FIG. 4 shows the control flow in this embodiment device. Each step will be explained below. Step 100: It is determined whether the shift determined by the computer 84 is a downshift. Steps 101 and 102: Since the control ranges are different for a downshift to the first gear and a downshift to the second gear, the content of the downshift (type of gear change) is determined and distinguished. Note that the downshift to the third gear is not particularly prohibited because it does not have much effect on vehicle behavior. Steps 103 and 104: It is determined for each type of shift whether the throttle opening θ corresponds to the region _A1 or _A2 shown in FIG. That is,
When downshifting to 1st gear, throttle opening θ
It is determined whether or not the throttle opening degree θ is greater _{than or equal to θ 1 in} downshifting to the second gear. Note that the area _A1 or _A2 in FIG. 5 is a predetermined driving state area related to vehicle speed, throttle opening, and type of shift for prohibiting downshifting in this control flow. Steps 105 and 106: Similarly, it is determined for each type of shift whether the vehicle speed V corresponds to the region _A1 or _A2 shown in FIG. That is, when downshifting to 1st gear, it is determined whether the vehicle speed V is greater than _V3 , and when downshifting to 2nd gear, the vehicle speed V is
It is determined whether or not it is greater than V ₄ . Steps 107 and 108: It is determined for each type of shift whether the steering angle α is within a predetermined driving state range. That is, in the case of a downshift to the first gear, whether the steering angle α is greater than or equal to _α1 , and in the case of a downshift to the second gear, whether the steering angle α is greater than or equal to _α2 . is judged. Note that α ₁ <α ₂ . Steps 109 and 110: If it is determined that the throttle opening θ, vehicle speed V, and steering angle α are all within the predetermined driving state range for each type of shift, the downshift is restricted. That is, when the type of shift is a downshift to the first gear, the downshift gear is limited to the second gear. As a result, if the downshift to the first gear is a downshift to the second gear, step 109 is performed.
This effectively prohibits gear shifting. Also, if the downshift is from the 3rd or 4th gear to the 1st gear, the 3rd or 4th gear
Only a downshift from gear to second gear is performed. Similarly, in step 110, in the case of a downshift to second gear, the downshift gear is limited to third gear. As a result, the third
In the case of a downshift from gear to second gear, shifting is essentially prohibited, and the downshift from fourth gear to second gear is prohibited.
In the case of a downshift to a gear, only a downshift from the fourth gear to the third gear is executed. Step 111: Either the shift output limited in steps 109 and 110 or the initial shift output determined according to the shift map is output. As a result, a control start map as shown in FIG. 1 is realized, and downshift restriction is executed according to the steering angle, vehicle speed, throttle opening, and type of shift. On the other hand, if the downshift restriction is executed in steps 109 and 110, the restriction is canceled in the sixth step.
This is performed by the control flow shown in the figure. That is, in step 200, the downshift control is executed. In step 202, the steering angle α
is the predetermined value α ₃ (in case of downshift to 1st gear)
It is determined whether or not the following is true. Note that in the case of downshifting to the second gear, it is determined whether or not the speed is less than or equal to _α4 . Here, the predetermined value α ₃ (α ₄ ) is a value set smaller than the above-mentioned predetermined value α ₁ (α ₂ ). If the steering angle α becomes less than α ₃ (α ₄ ), the downshift control is immediately canceled in step 204. On the other hand, when it is determined that the steering angle α is larger than α ₃ (α ₄ ), the process proceeds to step 206 where it is determined whether the throttle opening θ and the vehicle speed V are within a predetermined driving state range. Even if the steering angle α remains larger than α ₃ (α ₄ ), if either the throttle opening θ or the vehicle speed V falls outside the predetermined driving state range, the process advances to step 204 and the downshift control is immediately canceled. be done. On the other hand, the steering angle α is α ₃
(α ₄ ) and both the throttle opening θ and the vehicle speed V are within the predetermined driving state range, the downshift control continues to be maintained. As a result, when either the throttle opening θ or the vehicle speed V deviates from the predetermined driving state range, the downshift control is immediately canceled, but the steering angle α remains at the value α ₁ (α ₂ ) at the start of the control. Downshift control will be canceled only when α ₃ (α ₄ ) is lower than α 3 (α 4 ). In this way, by providing hysteresis in the control start condition and return condition, the set steering angle α ₁
It is possible to avoid a phenomenon in which downshifts and upshifts are repeated while driving near (α ₂ ). FIG. 7 shows another example for canceling downshift control. First, step 302
Downshift control is executed. Thereafter, in step 304, it is determined whether the steering angle α is less than or equal to α ₁ (or α ₂ when the limiting gear is the second speed). This step 304 is performed as long as the steering angle α is greater than _α1 .
The judgment is repeated. When the steering angle α becomes smaller than α ₁ , the process proceeds to step 306 and timer T is activated. In step 308, timer T is set to a predetermined value.
It is determined whether or not the temperature has exceeded Td. Timer T
If Td is less than the predetermined value Td, the routine proceeds to step 310, where it is determined whether the downshift limiting conditions including the vehicle speed V and the throttle opening θ are satisfied. When it is established, the process returns to step 302 and the downshift restriction control is maintained as it is. If the limiting condition is not met, the judgment made in step 308, that is, whether or not the timer T has become larger than the predetermined value Td is again judged, and at the point when the timer T has become larger than the predetermined value Td, the downshift restriction is canceled (step 314). As a result, as shown in FIG. 8, for example, the throttle opening θ vehicle speed V is within the predetermined driving range,
When only the steering angle α becomes smaller than α ₁ and falls outside the predetermined driving range, the downshift control is canceled only when the steering angle α continues to be smaller than α ₁ for Td. Become. If the steering angle α exceeds α ₁ even once before Td elapses, the count of the timer T is stopped and the prohibition control is continued. By doing this, it becomes possible to have hysteresis in the start and release of control. As shown in the flowchart of Figure 6, the starting value α ₁ of the control condition
The method of directly providing hysteresis between (α ₂ ) and the return value α ₃ (α ₄ ) has advantages such as a clear intention and a simpler control flow, but the currently developed steering angle Considering the accuracy of the sensor 99, this has the disadvantage that good results may not always be obtained. That is, when the steering angle α is large, the relationship between the steering angle α and the actual vehicle turning radius is relatively reproducible, but when the steering angle α is small, the relationship between the steering angle α and the actual vehicle rotation radius is relatively reproducible. The relationship with radius does not necessarily have good reproducibility. As described above, it is obvious that when the detected value of the steering angle α itself cannot be expected to be reliable, the hysteresis control based on the steering angle α is not necessarily executed accurately. Therefore, in order to provide reliable hysteresis when starting and executing this control, it is effective to use a timer to delay the return by a predetermined time Td. According to this method, once control is started, at least
Recovery is not performed during Td.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a starting condition map for downshift restriction control adopted in an embodiment of the turning control device for a vehicle automatic transmission according to the present invention, and FIG. 2 is a diagram showing a start condition map to which the above embodiment is applied. FIG. 3 is a diagram showing the operating state of each frictional engagement device, etc. in the automatic transmission, and FIG. 4 is a diagram showing the operating state of each frictional engagement device, etc. used in the above embodiment. FIG. 5 is a flowchart showing the control flow for starting downshift restriction control, FIG. FIG. 7 is a flowchart showing an example of another control flow for canceling the restriction control, and FIG. 8 is a flowchart showing the control flow for canceling the restriction control executed based on the control flow in FIG. 7. It is a time chart. 80... Throttle sensor, 82... Vehicle speed sensor, 99... Steering angle sensor, θ... Throttle opening, V... Vehicle speed, α... Steering angle.

Claims (1)

[Scope of Claims] 1. A vehicle configured to execute a downshift according to a predetermined vehicle speed-engine load shift map, and configured to limit execution of the downshift when the vehicle turns. In a turning control device for an automatic transmission, in order to realize the downshift restriction, a threshold value for determining whether to execute or prohibit a downshift is set depending on at least a steering angle, a vehicle speed, and an engine load. In addition to setting, the threshold value related to the engine load for the downshift is set differently depending on whether the type of downshift is a downshift between high speed gears or a downshift between low speed gears, even if the steering angle is the same. Characteristics of a turning control device for automatic transmissions for vehicles.