JP2001263469A - Method of preventing hunting in automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit automatic shift hold at the occurrence of hunting and to permit both upshift and downshift even in a shift hold state. SOLUTION: In an automatic transmission used for a vehicle such as a wheel loader to automatically shift a speed stage on the basis of vehicle speed during travel in a full throttle state, hunting shifted between the adjacent speed stages in a short time is detected during the travel, and when detecting the hunting, the values of an upshift point P1' and a downshift point P2' to the adjacent speed stages are changed, and one of the adjacent speed stages when detecting the hunting is made a speed stage after detecting the hunting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing hunting in an automatic transmission used for a work vehicle such as a wheel loader.
If hunting occurs while traveling at full throttle on an uphill slope on one of the adjacent speed stages, the state is detected and analyzed to fix the speed stage to the optimal one of the adjacent speed stages. The present invention relates to a hunting prevention method for preventing hunting.

[0002]

2. Description of the Related Art Conventional automatic speed apparatus (first prior art)
As shown in FIG. 8, the controller 1 controls the vehicle speed sensor 2 and
2nd-speed solenoid 4 or 3 that activates the 2nd-speed clutch
An automatic transmission that turns on one of the third-speed solenoids 5 that activates the speed clutch and runs at each speed stage is provided with a hold switch 6 for fixing the speed stage. In some cases, when it occurs, it is turned on to fix the speed stage to prevent the occurrence of hunting thereafter.

As another prior art (second and third prior arts), there are those disclosed in Japanese Patent Publication No. Hei 6-21650 and Japanese Utility Model Registration No. 2566126. If so-called hunting occurs in which the number of downshifts exceeds a predetermined number within a predetermined time between a predetermined speed stage and the next speed stage, so-called hunting occurs, upshifting is prohibited, and the vehicle is no longer climbing a hill. And shift up.

In the third prior art, when upshifting and downshifting are repeated when the engine throttle is fully opened, upshifting is inhibited, and inhibition of upshifting is continued until the throttle is fully opened. Like that.

[0005]

In the first prior art, an operation for pressing a hold switch is required every time hunting occurs in the vehicle. There was a problem that the steering operation became complicated.

In the second and third prior arts,
In both cases, when hunting occurs, upshifting of the speed stage is prohibited.For example, when hunting occurs at a low speed stage, even when the running resistance acting on the vehicle decreases, the vehicle is climbing up a slope or fully opening the throttle. In all cases, the vehicle was not shifted up, and in either case, the vehicle was required to run at a low speed with the throttle fully open, and there was a problem in energy saving and fuel saving measures.

The present invention has been made in view of the above. When hunting occurs, the hunting can be automatically prevented without using a hold switch.
In order to solve the above-mentioned problems of the related arts, it is possible to perform both upshifting and downshifting of the speed stage of the vehicle according to the running resistance acting on the vehicle even when hunting occurs. It is an object of the present invention to provide a method for preventing hunting in an automatic speed device that can perform the following. Specifically, as shown in FIG.
The hunting prevention logic 7 is provided in the controller 1 in addition to eliminating the hold switch 6 of the first prior art shown in FIG. 8, and the hunting prevention logic 7 prevents hunting.

[0008]

In order to achieve the above object, a method for preventing hunting in an automatic transmission according to the present invention is directed to a vehicle in which a speed stage is automatically shifted based on a vehicle speed during traveling. In the automatic transmission used in the above, during the above-mentioned traveling, hunting that switches between adjacent speed gears in a short time is detected, and when this hunting is detected, the shift up point P1 ′ and the shift down point with respect to the adjacent speed gears are detected. P
By changing the value of 2 ', one of the adjacent speed gears is set as the speed gear after the hunting is detected when the hunting is detected.

According to the present invention, when hunting occurs on a road surface where hunting is liable to occur, such as an uphill road, a hold switch is turned on to fix a speed stage or switch to a manual mode as in the related art. The hunting after the occurrence of the hunting can be prevented.

In this hunting prevention method, when the hunting is detected, the values of the shift-up point P1 'and the shift-down point P2' with respect to the adjacent speed stages to be hunted are changed, so that after the occurrence of the hunting. If the lower speed stage is selected from the adjacent speed stages, the vehicle is shifted up to the higher speed stage at the shift-up point P1 'when the vehicle speed increases due to the reduction of the running resistance. A speed stage corresponding to the speed can be obtained, and energy saving and fuel saving can be achieved as compared with the related art in which a low speed stage is fixed after hunting occurs.

When the higher speed stage is selected from the adjacent speed stages after the occurrence of the hunting, even if the vehicle speed falls below the speed of the shift-up point P1 'due to an increase in running resistance, the lower speed is immediately obtained. The shift is not performed at the speed stage on the side, and traveling at the higher speed stage can be performed smoothly.

In the above invention, the duration of each of the two adjacent speed stages at the time of hunting detection is detected, and the speed stage with the longer duration is set as the speed stage after hunting detection. It is possible to set a speed gear that matches the actual traveling speed, and by changing the value of the shift point, it is possible to reduce the frequency of hunting and reduce the shock.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described with reference to FIGS. (A) and (b) of FIG.
FIG. 1A shows a shift pattern of the wheel loader in the case of traveling uphill with the throttle fully open. FIG. 1A shows a case of normal traveling, where P1 is an upshift point and P2 is a downshift point. In order to reduce the shock at the time of downshifting, the speed at both points is P1 <P2. After a shift-up by the shift-up point P1 and after a shift-down by the shift-down point P2, a shift disable time of a predetermined time (for example, 2 seconds) is provided.

The shift in the normal running is increased, for example, while the vehicle is running in the second speed (F2), and when the shift-up point P1 (for example, 10.2 km / h) is reached, the speed changes in the third speed (F2).
The vehicle is shifted up to 3) and runs at a speed higher than the second speed (F2). Then, after the shift prohibition time has elapsed, the speed is increased or decelerated, so that the shift down point P2 (for example, 10.7 k
m / h), the downshift is performed and the 2nd speed (F2)
Is shifted. Even if the wheel loader satisfies P1 <P2, if the running resistance is low, such as when traveling on level ground, even if the gear is shifted up to the third speed at the shift-up point P1, the shift-down point P2 is reached after the shift impossible time (two seconds) elapses. The shift down point P
The vehicle speed increases without downshifting at 2, and 4 more
Shift up to speed. However, when the traveling resistance is large, such as on an uphill, after shifting up to the third speed at the shift-up point P1, the vehicle speed is changed from the second speed to the third speed, and the traction force is reduced. Even if the vehicle speed once becomes larger than the downshift point P2 within the second), the vehicle speed immediately falls to the downshift point P2. Further, the vehicle speed reaches the shift down point P2 after the shift impossible time (two seconds) has elapsed, and the vehicle shifts down to the second speed at the shift down point P2. When the vehicle shifts down to the second speed at the shift down point P2, the vehicle speed temporarily becomes lower than the shift up point P1, but the traction force increases, so that the vehicle speed increases again to the shift up point P1 and shifts up to the third speed. Hunting occurs by repeating the above.

FIG. 1B shows the case of hold running in the hunting prevention logic, where P1 'is a shift up point, P2' is a shift down point, and P1 '> P.
2 'and the speed of P1' is, for example, 1
1 km / h, the speed of P2 'is, for example, 9.0 km / h,
The shift point interval P1'-P2 'is larger than the shift point interval P1-P2 in the case of normal running.

In the case of the hold traveling, for example, the speed is increased while the vehicle is traveling in the second speed (F2), and becomes the third speed (F) when the shift up point P1 '(11 km / h) is reached.
The shift is shifted up to 3), the hold traveling is released, and the shift is performed at the normal shift points P1 and P2. This is because, when the gear is shifted at the point during the hold, the running state is regarded as changed, and the state returns to the normal state.

FIG. 2 is a diagram showing the state of the above-mentioned shift pattern. That is, in the case of normal running in the uphill running at full throttle, for example, 2
During traveling at the speed (F2), the traveling resistance is reduced and the vehicle is accelerated, and the vehicle speed is 10.2 km / of the shift-up point P1.
When h is reached, the upshift is performed and the vehicle is driven in the third speed (F3). If the vehicle speed does not rise above the shift down point P2 of 10.7 km / h within 2 seconds of the shift impossible time,
The vehicle is shifted down to second speed (F2). As described above, when the running resistance is between the shift-up point P1 and the shift-down point P2, the shift-up and the shift-down are frequently performed, and a hunting state is obtained. It is determined that hunting has occurred, and a hold state is set.

In the case of the hold traveling, for example, during traveling in the second speed (F2), the traveling resistance is reduced and the vehicle is accelerated. When the vehicle speed reaches the shift-up point P1 'of 11 km / h, the vehicle is shifted up to the third speed. (F3) Running, hold running is released, and normal shift points P1, P2
The speed is changed by.

FIG. 3 shows a flow of the hunting prevention method according to the present invention. Hunting is determined when the vehicle is running in the second speed (F2) or the third speed (F3) (step (1)). At this time, the traveling state of the vehicle is as shown in FIG. 4. For example, the vehicle that has traveled normally with the second speed (F2) and traveled while shifting with the normal shift pattern shown in FIG. 3rd speed (F3) → 2nd speed (F2) → 3rd speed
When the speed is changed from speed (F3) to second speed (F2),
The shift holding time TFi of each speed is within a hunting determination threshold TH for a predetermined time (for example, 5 seconds) (TFi <TH).
If it is, hunting is determined. On the other hand, if TFi> TH, it is determined to be normal.

If hunting is determined in step (1), the number of hunting is counted in step (2). When the number of times of hunting becomes Nmax times, for example, two or more times (step (3)), the process proceeds to the hunting prevention logic (step (4)), and the shift pattern of the automatic transmission is shown in FIG. The shift pattern at the time of normal running shown can be changed to the shift pattern during hold shown in FIG.

When the hold speed during this hold is 2
Whether the speed becomes the second speed (F2) or the third speed (F3) is determined by the hunting determination in the hunting determination in step (1). That is, if TF2 ≦ TF3, the third speed (F3) is held, and if TF2 ≧ TF3, the second speed (F3) is held.
2) It is held.

The hunting prevention logic (step (4)) is used for the shift points P1 ', P
It ends when a shift change is performed at 2 ',
The shift pattern returns to the normal one. That is, FIG.
In (b), when the vehicle is held at the second speed (F2), the hold is released when the speed is increased to P1 'and shifted up to the third speed (F3), and the normal operation is performed at the third speed (F3). Be run.

FIGS. 5 and 6 are flowcharts specifically showing the above-described control method. Each step will be described below in order. First, the controller of the automatic transmission detects whether it is in the automatic transmission mode (S1), and then detects whether this is a hunting prevention hold (S2). If the hunting prevention hold is set, the shift points F2.fwdarw.F3 are changed to the shift points P1 'and P2' during the hold so as to have the shift pattern shown in FIG. 1B (S3). If there is a shift change or forward / reverse switching during the hold traveling (S4), the hunting prevention hold is released (S5) and the process ends.

In the step (S2), if the controller is not in the hunting prevention hold, the shift points of the second speed (F2) and the third speed (F3) are shifted to the normal shift points P1 and P2. (S
6). The presence or absence of the automatic shift in this state is detected (S
7). When this shift is made, this is changed to the second speed (F
It is determined whether the shift is from 2) to the third speed (F3) or vice versa (S8). If the automatic shift at this time is neither of these, the process ends.

It is determined whether the automatic shift in step (S8) is a shift from the second speed (F2) to the third speed (F3) (S8).
9) If the automatic shift is from the second speed (F2) to the third speed (F3), then is the continuous shift from the third speed (F3) to the second speed (F2) → the third speed (F3) performed? Is detected (S1
0). If the continuous shift has been performed, it is determined whether the holding time of the second speed (F2), which is the speed stage before the start of the continuous shift, is within the hunting determination threshold TH (S11).
If it is within TH, hunting is determined, and the number of hunting is counted (S12). Then, it is detected whether the number of hunting is Nmax or more, for example, 2 or more (S
13) If it is two or more times, the shift holding time of both speeds (F2, F3) in the hunting state is compared (S1).
4) When the second speed (F2) is longer, hold at the second speed (F2) (S15), and when the third speed (F3) is longer, hold at the third speed (F3) (S16). .

In step (S9), the second speed (F2)
→ If it is not the third speed (F3) (F3 → F2), then
It is detected whether or not the continuous shift from the second speed (F2) to the third speed (F3) → the second speed (F2) has been performed (S17). If the continuous shift has been performed, it is determined whether the holding time of the third speed (F3), which is the speed stage before the start of the continuous shift, is within the hunting determination threshold TH (S18), and if it is within TH. Hunting and count the number of hunting (S1
9) Then, it goes to the above step (S13).

Then, in both logics separated from step (S9), step (S10) and step (S1)
In the case of NO in each of 1), step (S17), and step (S18), the number of hunting is cleared (S2
0).

In step (S7), if there is no automatic shift (shift), the speed at this time is set to the third speed (F
3) (S21), 2nd speed (F2) (S2
The shift holding time is counted according to 2) (S23), and the process ends from (S24).

5 and 6, (S15), (S1)
6) In both steps, the second speed (F2) or the third speed (F
3), and this state is changed to (S2)
Is the state of YES in the step of, that is, the hunting prevention hold state.

[Brief description of the drawings]

FIGS. 1A and 1B show examples of shift points of an automatic transmission according to the present invention, wherein FIG. 1A shows a case of normal traveling and FIG. 1B shows a case of holding.

FIG. 2 is a diagram showing gear shift states at respective shift points in a normal case and a hold state of second speed and third speed with respect to towing and vehicle speed.

FIG. 3 is a flowchart showing a control method for preventing hunting according to the present invention.

FIG. 4 is an explanatory diagram showing a state of shifting from a normal running to a hunting state.

FIG. 5 is a part of a flowchart showing an embodiment of a hunting prevention method according to the present invention.

FIG. 6 is another part of the flowchart showing the embodiment of the hunting prevention method according to the present invention.

FIG. 7 is an explanatory diagram illustrating a configuration of a hunting prevention device according to the present invention.

FIG. 8 is a configuration explanatory view showing a conventional hunting prevention device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Controller, 2 ... Vehicle speed sensor, 3 ... Shift lever,
4 ... Solenoid for 2nd speed, 5 ... Solenoid for 3rd speed, 6 ... Hold switch, 7 ... Hunting prevention logic

Claims (2)

[Claims] 1. An automatic transmission for use in a vehicle which automatically shifts a speed stage based on a vehicle speed during traveling, detecting hunting that switches between adjacent speed stages in a short time during the traveling, When the hunting is detected, the values of the shift-up point P1 'and the shift-down point P2' with respect to the adjacent speed gears are changed, and one of the adjacent speed gears is set as the speed gear after the hunting is detected when the hunting is detected. A method for preventing hunting in an automatic transmission, wherein: 2. The method according to claim 1, wherein the duration of each of the adjacent speed gears at the time of hunting detection is detected, and the speed gear having the longer duration is set as the speed gear after hunting detection. Item 2. A hunting prevention method in the automatic transmission according to Item 1.