JPH02253052A - Automatic transmission gear control device - Google Patents

Abstract

PURPOSE:To make an engine brake compatible by prohibiting the use of the maximum speed stage at the time of an accelerator not being stepped on, the running resistance or acceleration being within the specified range, and the car speed at which an engine does not overrun even by the speed change to the stage which is one stage lower than the maximum speed stage. CONSTITUTION:A controller 10 inputs the signals of an engine rotation sensor 2, a gear stage detecting sensor 7, a car speed sensor 9, a select lever sensor 12 and an accelerator sensor 14, and sets a flag 10-1 for prohibiting the use of the maximum speed stage at the time of an accelerator 1 not being stepped on, the running resistance or the acceleration being within the specified range, and the car speed at which an engine 1 does not overrun even if a transmission gear 5 is speed-changed to the gear stage which is one step lower than the maximum speed stage. When the accelerator 13 is stepped on or the fixed range is selected, the flag 10-1 is released. The engine brake is thus made compatible at the time of braking during the high speed running so as to reduce the abrasion of a foot brake.

Description

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

The present invention is an automatic transmission system that applies engine braking even when driving in the automatic transmission range when driving at high speed and when braking is required.

[Conventional technology]

There are automatic cars that are equipped with a friction-type automatic clutch and automatic transmission, and are controlled by a controller consisting of a microcomputer or the like. In such an automatic vehicle, a shift range can be selected using a select lever, and the shift range can be broadly classified into a fixed range and an automatic shift range. If you select a fixed range, the vehicle will drive in a specific gear. For example, if the "1" range is selected, the vehicle will run in first gear. When automatic shift range "D" is selected, the controller selects the optimal gear based on the vehicle's driving conditions, engine conditions, etc., and automatically shifts the gear. Selection of the optimum gear stage is performed according to a predetermined shift diagram. FIG. 2 shows an example of such a shift diagram. The horizontal axis is the vehicle speed, and the vertical axis is the accelerator depression amount. In FIG. 2, curve A indicates the boundary when shifting up from 1st speed to 2nd speed. When the operating point determined by the vehicle speed and the amount of accelerator depression moves across curve A from left to right, 1
It will automatically shift up from 1st gear to 2nd gear. Similarly, the curve opening indicates the boundary when shifting from 2nd speed to 3rd speed, and the boundary when shifting from 3rd speed to 4th speed. Note that the curve in FIG. 2 is for upshifting. Therefore, even if the operating point crosses curve A from right to left, it does not mean that the gear is downshifted from second gear to first gear. In order to provide hysteresis to the gear shifting operation, another curve (not shown) is prepared for downshifting. In addition, as a conventional document regarding an automatic transmission control device, there is Japanese Patent Application Laid-Open No. 100023/1983.

[Problem to be solved by the invention]

(Problem) With the conventional technology described above, engine braking cannot be applied when the vehicle is running in the automatic transmission range, so the burden is placed only on the foot brake, which causes severe wear on the brake lining and brake pads. was there. (Explanation of the problem) When attempting to apply engine braking, drivers habitually release their foot from the accelerator pedal. However, when driving in the automatic transmission range, the vehicle may end up shifting up. For example, in Fig. 2, vehicle speed N, accelerator depression MP
The operating point when the vehicle is running in No. 1 is A, but when the accelerator pedal is released in this state, the operating point shifts to B. At this time, since the vehicle crosses curve C and enters the 4th gear region, the gear is shifted up from 3rd gear to 4th gear. Shifting up would disappoint the driver's expectations of applying engine braking. The driver has no choice but to apply the foot brake. At low and medium speeds, the degree of wear on the footbrake is small, but when used at high speeds, the wear is large. This is because the kinetic energy of a vehicle is related to the square of the vehicle speed, and a large braking force is required to stop a vehicle running at high speed. Additionally, some vehicles are equipped with an overdrive gear (hereinafter referred to as rOD) with a gear ratio of 1 or less as the highest speed gear in order to reduce engine speed and improve fuel efficiency when driving at high speeds. . An overdrive switch is provided which is a switch for selecting whether or not to use the OD stage. If you are driving in OD gear, you cannot expect engine braking, so if you want engine braking to work, turn off the overdrive switch and do not use OD gear. Then, even at high speed, 1 stage is higher than 00 stage.
The vehicle will run in the lower gear, which has the effect of engine braking. However, the overdrive switch is cumbersome to operate because the driver has to switch it each time while judging the driving situation, and it cannot be said to be fully utilized to reduce the burden on the foot brake. An object of the present invention is to solve the above-mentioned problems.

[Means to solve the problem]

In order to solve the above problem, in the present invention, even if braking at low and medium speeds is left to the foot brake, at least when braking at high speeds when the fund brake is heavily worn,
The following measures were taken in order to obtain an engine braking effect by running the vehicle in a gear that is one gear lower than the OD gear (or the highest gear for vehicles without an OD gear). That is, in the automatic transmission control device of the present invention, even if the accelerator pedal is not depressed, the running resistance or acceleration is within a predetermined range, and the gear is shifted to one gear below the highest speed, the engine will not start. The system is equipped with a means for prohibiting the use of the highest gear when the vehicle speed is such that it will not overrun, and a means for canceling the prohibition of the use of the highest gear when the accelerator pedal is depressed or a fixed range is selected. .

[For production]

According to the above-mentioned automatic transmission control device, it is determined whether engine braking is likely to be required while driving in the automatic transmission range by checking the driver's intention and the vehicle situation. . The driver's intention is checked by checking whether he or she is pressing the accelerator pedal. If you press the pedal down, it means you want to accelerate, so you don't need engine braking. Vehicle conditions are checked to see if the running resistance or acceleration is within the specified range, and whether the vehicle speed is such that the engine will not overrun even if the gear is shifted to one gear below the OD gear (or the highest gear). This is done on two points. If the running resistance is lower than the set value, it means that the vehicle is likely to speed up, so there is a need for engine braking. The same holds true when the acceleration is greater than the set value. The effect of engine braking comes from driving in the gear one step lower when the vehicle speed would normally be in OD gear (or highest gear), but if you shift to that gear, the engine It would be a problem if the engine speed rose too high and the engine went into overrun condition. This is because even if the foot brake is less damaged, the engine is more likely to be damaged. As a result of checking the driver side and the vehicle side, if it is determined that there is no problem in using the gear one step below for engine braking, the O
Prohibits use of D gear (or highest speed gear). As a result, when the vehicle is automatically shifted to the OD gear (or the highest gear), the vehicle is driven in a gear one gear lower than the OD gear (or the highest gear), and engine braking is applied. On the other hand, when the fixed range is selected by the select lever or when the driver is depressing the accelerator pedal, the use of the OD gear (or the highest speed gear) is not prohibited. This is because, in the case of a fixed range, there is no relation to the shift diagram shown in FIG. 2, and there is no possibility that the gear will shift up when the accelerator pedal is released. Furthermore, if the accelerator pedal is pressed down, the driver has the will to accelerate, so there is no need to apply engine braking.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows an automatic transmission control device according to an embodiment of the present invention. In FIG. 1, 1 is an engine, 2 is an engine speed sensor, 3 is a clutch, 4 is a clutch actuator, 5 is a transmission, 6 is a transmission actuator, and 7
is a gear stage detection sensor, 8 is a drive shaft, 9 is a vehicle speed sensor, 1
0 is a controller, 10-1 is a prohibition flag, 11 is a select lever, 12 is a select lever sensor, 13 is an accelerator pedal, and 14 is an accelerator sensor. The clutch actuator 4 controls whether or not the clutch 3 is engaged or disengaged in response to a signal from the controller 10 . The transmission actuator 6 shifts gears in response to a signal from the controller 10. Gear stage detection sensor 7
detects which gear is currently in use. The select lever 11 is a lever for selecting various fixed ranges or automatic shift ranges. FIG. 3 is a flowchart for explaining the control operation of the present invention. This flowchart is repeatedly executed at extremely short time intervals (for example, several tens of meters). Item numbers ■ ~ @ in the following explanation refer to steps ■ in Figure 3.
It corresponds to ~■. ■ Read signals related to select lever range, vehicle speed, engine speed, and accelerator pedal depression. These signals are sent to the select lever sensor 12 and the vehicle speed sensor 9. Engine speed sensor 2. It is obtained from the accelerator sensor 14. ■ Recognize which gear is currently in use. This is done by reading the signal from the gear stage detection sensor 7. ■ Calculate the vehicle's running resistance under current conditions. Running resistance is a force that opposes the running of the vehicle. For example, running resistance is small when the vehicle is running downhill, and is large when the vehicle is running uphill. The running resistance is calculated by a known method using engine speed and the like. ■ Check whether you are driving in the automatic transmission range. This is done by examining the signal from the select lever sensor 12. ■ The fact that it is not in an automatic transmission range means that it is running in a fixed range. In this case, the prohibition flag 10-1 set in the controller 10 is reset. The prohibition flag 10-1 is O when it is set.
This means that the use of the D gear (or the highest speed gear) is prohibited, and is not prohibited when it is reset. ■ Since the vehicle is running in a fixed range, processing operations are performed according to that range. For example, when the fixed range of "1" is selected,
Travel is performed while maintaining the first gear. ■ Check whether the accelerator pedal is pressed. This determines whether the driver has the intention to accelerate. In other words, do eight laps to see if you're willing to apply engine braking. When you press the accelerator pedal to accelerate, it is determined that there is no intention to apply engine braking. This step is engine brake number 1! ! This step is aimed at checking with the driver to see if they need to be prepared. Steps (2) and [phase] that come after this are steps aimed at inspecting the vehicle side. - If it is determined that there is no intention to apply the engine brake, the prohibition flag 10-1 is reset. This is because in this case, there is no need to prohibit the use of the OD gear (or the highest speed gear). ■ Check whether the running resistance calculated in step ■ is less than the set value. This is because the magnitude of running resistance is one of the factors for determining whether or not the vehicle is in a situation that requires engine braking. This is because when running resistance is large, there is no need to use engine braking. For example, running resistance is large when going uphill, but engine braking is of no use at such times. Conversely, running resistance is small on a downhill slope. In such cases, it is necessary to be able to apply engine braking. By the way, the magnitude of the "setting value" that is the subject of comparison varies depending on the vehicle model, but it can be determined based on the amount of running resistance at which it is necessary to apply engine braking. For example, if the brakes are to be applied, the set value may be the running resistance when the vehicle is traveling on a flat road at a speed that imposes an excessive load on the foot brake. [Phase] Check to see if the engine will overrun if you downshift one gear at the current vehicle speed. From the gear ratio and vehicle speed after downshifting,
The engine speed can be calculated, so check based on that. If the engine overruns, you need to give up on engine braking. (2) If there is no overrun even if the gear is downshifted, set the prohibition flag 10-1. This means that the use of the OD gear (or the highest speed gear) is prohibited, and the conditions for applying engine braking have been established. (2) Check whether the prohibition flag 10-1 is set or not. - If the prohibition flag 10-1 is set, the OD gear (or highest speed gear) cannot be used. Therefore, automatic shift range processing operations such as shift amplifier operation (processing to determine the optimal gear) according to the shift diagram shown in Figure 2 are performed without using the OD gear (or highest gear). be exposed. For example, in Figure 2 where 4th gear is the highest gear, if you release your foot from the accelerator pedal at point A, normally 3
The vehicle will shift up from speed to 4th gear, but if the use of 4th gear is prohibited, it will remain in 3rd gear and engine braking will be applied. - When the prohibition flag 10-1 is reset, there is no need for engine braking. Therefore, the use of OD gear (or highest speed gear) is not prohibited. The processing operation of the automatic shift range is performed including the 09th gear (or the highest gear). ■ Check whether gear shifting operation is necessary. This is done by comparing the optimal gear determined in step (2) [phase] with the current gear recognized in step (2). If they match, there is no need for a shift operation; if they do not match, it is necessary.
' [Phase] When a gear shift operation is not required, it is sufficient to maintain the current gear position, so the clutch 3 is controlled in this manner. ■ Perform gear shifting operations. The gear shifting operation involves driving the clutch actuator 4 to disengage the clutch 3, driving the transmission actuator 6 to perform a gear shift, and driving the clutch actuator 4 again to engage the clutch 3. done in order. In the above example, there are some parts where the determination is made using "1 running resistance" (steps (2) and (2)), but these parts can also be changed so that the determination is made using "acceleration". However, the words in step ■ are "Is the acceleration set value or more?" Note that the acceleration can be calculated using the vehicle speed change rate or the engine rotation speed change rate.

【Effect of the invention】

As described above, according to the present invention, in the automatic transmission,
Even if you are driving at a high speed that requires the use of the OD gear (or the highest gear), if certain conditions are met, the use of the OD gear (or the highest gear) will be prohibited and the vehicle will drive in the next lower gear. let me,
Engine braking can now be applied. Therefore, it is now possible to use the engine brake in conjunction with braking during both speed driving, where the wear of the foot brakes is severe, and it has become possible to reduce the wear of the foot brakes. 10 is a controller, 10-1 is a prohibition flag, 11 is a select lever, 12 is a select lever sensor, 13 is an accelerator pedal, and 14 is an accelerator sensor.

Claims (1)

[Claims] Use the highest gear when the accelerator pedal is not depressed, the running resistance or acceleration is within the specified range, and the vehicle speed is such that the engine will not overrun even if the gear is shifted to one gear below the highest gear. An automatic transmission control device comprising: means for prohibiting the use of the highest gear; and means for canceling the prohibition of the use of the highest gear when the accelerator pedal is depressed or a fixed range is selected.