JPS61103044A - Automatic speed changer - Google Patents

Abstract

PURPOSE:To improve the operationability by shifting down a speed changer if the car speed will increase continuously under the condition where the throttle opening is lower than predetermined level, decreasing or maintained constant after decrease. CONSTITUTION:An accelerator pedal 128 is provided with a movement sensor 126 the output from which is fed to a microcomputer 116 to execute shift-down irrespectively of speed change map if the car speed will increase continuously under the condition that the throttle opening is lower than predetermined level, decreasing or maintained constant after decrease. Consequently, engine brake will function effectively to prevent unintended speed increase resulting in improvement of operationability.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to automatic transmissions for vehicles, and in particular,
This relates to the speed change control.

Conventional automatic transmissions for vehicles generally specify that a shift amplifier or downshift should be performed when the relationship between vehicle speed and engine throttle opening (throttle valve opening) reaches a certain value. A so-called shift map is stored in the storage area of the control device, and the vehicle speed and throttle opening are detected while the vehicle is running, the shift map is searched based on these detection results, and the shift amplifier or A downshift is now being performed.

Problems to be Solved by the Invention However, in conventional vehicles equipped with automatic transmissions as described above, it has been difficult to use engine braking when exiting the vehicle. It is effective to use engine braking to prevent the vehicle speed from increasing more than the operator desires when exiting the vehicle, and in vehicles equipped with a manual transmission, downshifting the transmission can sufficiently apply engine braking. However, in vehicles equipped with automatic transmissions, even if you release the accelerator pedal to apply engine braking, the vehicle's speed will not decrease so rapidly, so downshifting will not be possible. Rather, there is a possibility that an upshift will occur.

This is because, while the throttle opening decreases when the accelerator pedal is released, the shift map is normally set such that the lower the throttle opening, the lower the vehicle speed.

When the vehicle speed range is wide and the gradient of the shift line is gentle, such as in a normal passenger car, a so-called kickdown occurs, in which a downshift occurs when the accelerator pedal is suddenly depressed, so this phenomenon is utilized. It is possible to quickly downshift by using engine braking effectively. However, when the vehicle speed range is narrow and the slope of the shift line is steep, such as in an industrial vehicle such as a forklift truck, it is difficult to expect such a kickdown to occur.

Means for Solving the Problems The present invention has been made in order to solve the above-mentioned problems, and for this purpose, the gear position of the transmission is changed according to the shift map stored in the storage area of the control device. In an automatic transmission that automatically switches, a throttle opening detection device is provided to detect the opening of the throttle valve, and the control device is configured to detect when the throttle opening detected by the throttle opening detection device is below a certain value. If the vehicle speed continues to increase for a certain period of time even though at least one of the following conditions is met: the vehicle speed is decreasing or is held constant after decreasing, the transmission is changed regardless of the shift map. The gist of this is that the gear is downshifted to a lower gear.

Functions and Effects In the automatic transmission configured as described above, at least one of the following conditions is satisfied: the throttle opening is below a certain value, is decreasing, or is held constant after decreasing. If the vehicle speed continues to increase for a certain period of time despite the change in speed, the transmission is downshifted regardless of the shift map. In such cases, it is normal for the operator to have no intention of increasing the speed of the vehicle, so if the vehicle speed continues to increase for a certain period of time, the increase in vehicle speed is considered to be against the operator's will, and the vehicle is shifted. This downshift effectively applies engine braking to prevent an increase in speed against the driver's will, thereby improving driving operability.

In particular, in industrial vehicles such as forklift trucks and excavators, there are operation levers for operating equipment in addition to the steering wheel, and it may be necessary to operate these while driving, so the accelerator pedal is operated by foot rather than by hand. It is extremely beneficial to be able to quickly downshift by simply operating the .

EXAMPLE Hereinafter, an example in which the present invention is implemented in a forklift truck equipped with a power transmission device in which an automatic transmission is directly connected to an engine without going through a torque converter will be described in detail with reference to the drawings.

In FIG. 2, 10 is an engine. A pump 12 and a planetary gear unit 14 are connected to the engine 10, and the planetary gear unit 14 is connected to the sun gear 1.
6, 18, 20, 22. Planetary gear 24, 26, 2
8. ．． 30. Ring gears 32, 34, 36, 38.
Forward clutch 40° Reverse clutch 42. First clutch 44°Second clutch 46. It is equipped with a third clutch 48, etc. In the third clutch 48, both of the two clutch elements connected to each other are rotatable, but in other clutches, one clutch element is not rotatable. Forward clutch 4
When the zero or reverse clutch 42 is in the engaged state, any one of the first, second, and third clutches is brought into the engaged state, thereby providing three forward speeds or three reverse speeds.

That is, in this embodiment, a sun gear, a planetary gear, etc., and a first clutch 44. A transmission is constituted by shift clutches such as a second clutch 46 and a third clutch 48, and this and the engine 10 are connected to the forward clutch 40 or reverse clutch 4, which is the main clutch.
They are connected by 2.

The planetary gear unit 14 has a pinion of 50.5 mm.
2 and gears 54 and 56 is connected thereto, and left and right drive wheels 62 are connected to the reducer 58 via a differential gear device 60.

A pump 12 connected to the engine 10 sucks hydraulic oil from a tank 70 as shown in FIG. supply The hydraulic pressure supplied to these is always kept at a constant value by the regulator 72, but the hydraulic pressure supplied to the actuators 40a and 42a of the forward clutch 40 and the reverse clutch 42 is further controlled by a modulator 74. ing. 75 is an aperture.

As shown in FIG. 4, the modulator 74 includes a drain passage 78 that drains hydraulic oil from a main passage 76 connecting the regulator 72 and the actuator 40a'i or 42a to the tank 70. A relief valve 80 is provided at the connection portion of the drain passage 78 to the main passage 76. The relief valve 80 has a valve 82. Spring 84° Piston 86. A spring 88 and the like are provided, and the opening pressure of the relief valve 80 changes as the position of the piston 86 changes.

The position of the piston 86 is determined based on the urging force of the springs 88 and 84 and the oil pressure in the hydraulic chamber 90 (piston 86
The hydraulic pressure in the hydraulic chamber 90 is controlled by an electromagnetic on-off valve 92.

Hydraulic oil from the main passage 76 is led to the hydraulic chamber 90 through a control passage 96 having a throttle 94, and the amount of hydraulic oil flowing from the hydraulic chamber 90 from the electromagnetic on-off valve 92 is controlled. The hydraulic pressure in the hydraulic chamber 90 is controlled. The electromagnetic on-off valve 92 closes when the modulating solenoid 98 is off, that is, when no current is supplied, and opens when the modulating solenoid 98 is on. The amount of hydraulic oil flowing out from the hydraulic chamber 90 is controlled by changing the duty ratio of the current.

The hydraulic oil whose hydraulic pressure is controlled by the modulator 74 is transferred to the forward clutch 40 by a manual directional control valve 100.
The actuator 40a and the actuator 42a of the reverse clutch 42 are selectively supplied. That is, the directional control valve 100 is connected to a shift lever 101 as an operating member for determining the traveling direction of the vehicle, and when the shift lever 101 is in the neutral position, hydraulic oil is not supplied to either actuator 40a or 42a. First, when the shift lever 101 is operated to the forward or reverse position, hydraulic oil is supplied to the corresponding actuators. Above is the pump 12° regulator 72. The modulator 74, the direction switching valve 100, and the like constitute a clutch connection/disconnection device.

On the other hand, for the regulator 72 and the first.

Second and third clutch actuator 4
Directional switching valves 102 and 104 are disposed in the middle of the oil passage connecting the oil passages 4a, 46a, and 48a.

These directional control valves 102 and 104 are in the third position when the drain passages 110 and 112 are opened by energizing the shift solenoids 106 and 108, respectively.
The state shown in the figure is reached, and the shift solenoids 106 and 1
08 can be switched to the opposite state when each is demagnetized. That is, the shift solenoid 10
Hydraulic oil is supplied to any of the actuators 44a, 46a, and 48a depending on whether the first clutch 44.6, 108 is on or off. The second clutch 46 or the third clutch 48 is connected.

the above? The foot solenoids 106, 108 and the modulating solenoid 98, as shown in FIG.
Microcomputer 1 controlled by microcomputer 116 via solenoid drive circuit 114
16 is equipped with a CPU (central processing unit) 118,
A signal from the rotation sensor 120 is input to this. The rotation sensor 120 is disposed close to the outer circumference of the pinion 50 and generates an alternating current signal as the pinion 50 rotates. This AC signal is shaped into a rectangular wave by the waveform shaping circuit 124, and the CPU
1 B is supplied. Since the pinion 50 is fixed to the output shaft of the transmission as shown in FIG. 2, the frequency of the rectangular wave is proportional to the rotation speed of the output shaft of the transmission. Further, since only some gears are interposed between the pinion 50 and the drive wheel 62, the rotation speed of the pinion 50 is proportional to the rotation speed of the drive wheel 62, that is, the vehicle speed.

Therefore, the CPU 1B can calculate the vehicle speed from the frequency of the rectangular wave.

A movement sensor 126 is further connected to the CPU 18. This movement amount sensor 126 is connected to the accelerator pedal 12.
Although it is depicted as directly detecting the amount of movement of 8, this is not necessarily essential, and it may be possible to detect the movement of the accelerator pedal, throttle valve, or any of the members that connect the two. . Since the amounts of movement of these members are substantially proportional, the CPU 118
The throttle opening degree can be calculated based on the output signal of the movement amount sensor 126, and the CP
The UI 1 B and the movement amount sensor 126 constitute a throttle opening detection device.

The microcomputer 116 includes a memory 130 in addition to the CPLJI 18, and the memory 130 stores various control programs as well as control patterns for the modulating solenoid 98 and shift solenoids 106 and 108, and a speed change map. During gear shifting, the hydraulic pressure of actuator 40a (same as 42a) is changed as shown in FIG. 6, and after the forward clutch 40 is once disengaged, one of the shift clutches, for example, the first clutch 44, is disengaged. At the same time, it is necessary to connect the second clutch 46 and then slowly connect the forward clutch 40, and control patterns for the modulating solenoid 98 and shift solenoids 106 and 108 for this purpose are stored. In addition, as shown in Figure 7, the gear change map shows the timing at which the gear ratio should be automatically switched using vehicle speed and accelerator opening as parameters, and the solid lines in the figure are numbers. The arrows and arrows indicate a shift line for shifting from 1st to 2nd gear or from 2nd to 3rd gear, and the broken line indicates a shift up from 3rd to 2nd gear. This is a shift line for downshifting from second gear to second gear. When the vehicle speed increases with the throttle opening at a certain value and reaches the value shown by the solid line, a shift amplifier is performed, and conversely, if the value shown by the broken line is reached during deceleration, a downshift is performed. However, since this point is already well known, detailed explanation will be omitted. Furthermore, as is clear from the above explanation, the first
A microcomputer 116 comprising a memory 130 in which the program represented by the flowchart shown in the figure and the shift map shown in FIG. 7 are stored constitutes a control device for the automatic transmission.

The operation of the apparatus of this embodiment will be explained below based on the flowchart shown in FIG.

First, step S1 is executed, and (a) it is determined whether the throttle opening is below a relatively low value such as 5% (bl whether the throttle opening is decreasing or not)
It is determined whether any of the following conditions is satisfied: the throttle opening remains at a constant value after decreasing. If the determination result is NO, a normal shift map search is performed in step S2. In step S3, it is determined whether or not a shift is necessary. If a shift is necessary, a shift is performed in step S4. If a shift is not necessary, one execution of the shift routine is continued. While the vehicle is running, this shift routine is repeatedly executed along with other programs, but since this point is well known, a detailed explanation will be omitted.

If the determination result in step S1 is YES, that is, if any of the three conditions mentioned above is satisfied, step S5 is executed, and it is determined whether the vehicle speed is increasing or not. If the vehicle speed is not increasing, steps S2 to S4 are executed in the same way as in the above case, but if it is increasing, S6 is executed to determine whether a certain period of time has elapsed since the vehicle speed started increasing. be judged. If the elapsed time has not elapsed, steps S2 to S4 are performed in the same way as in the above case.
However, if the vehicle speed continues to increase for a certain period of time, step S7 is executed (actual), and a downshift is performed to a gear position one gear lower than the current gear position. By executing this downshift, execution of one shift routine is completed.

If the throttle opening is below a certain value, is decreasing, or remains constant after decreasing as described above, but the vehicle speed continues to increase for a certain period of time,
This speed increase is automatically determined to be against the operator's will, and a downshift is performed, thereby effectively applying engine braking and suppressing the speed increase of the vehicle.

Although one embodiment of the present invention has been described in detail above, this is literally an example, and the present invention can be implemented in other embodiments.

For example, in the above embodiment, a downshift is performed even if any of the following three conditions is met: the throttle opening is below a certain value, is decreasing, or is kept constant after decreasing. However, it is also possible to downshift only when one or two of the above three conditions are satisfied.

In addition, in the above embodiment, the automatic transmission was a planetary gear type equipped with a forward clutch and a reverse clutch, but a constant mesh type or selective sliding type transmission is common for forward and reverse. Even if the vehicle is connected to the engine by a single clutch, the present invention can be applied to any vehicle that can automatically change gears by a shift actuator and a clutch connection/disconnection actuator.

Further, in the above embodiment, the transmission was directly connected to the engine without going through a torque converter, but the present invention can also be applied to an automatic transmission that is connected to the engine through a torque converter. Furthermore, the present invention can be applied not only to industrial vehicles such as forklift trucks, but also to automatic transmissions of passenger cars, trunks, and the like.

Although not illustrated in detail, the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing one embodiment of the present invention. FIG. 2 is a diagram conceptually showing the entire power transmission system for a forklift truck equipped with an automatic transmission controlled based on a program as shown in the above flowchart. FIG. 3 is a circuit diagram showing the hydraulic circuit of the automatic transmission, and FIG. 4 is a horizontal view showing details of the modulator shown in FIG. 3. FIG. 5 is a block diagram showing the electrical control portion of the automatic transmission. FIG. 6 is a graph showing the control status of the actuator oil pressure during gear shifting in the automatic transmission. FIG. 7 is a diagram showing a shift map stored in the memory shown in FIG. 5. 12: Pump 14: Planetary Gyauninote 40:
Forward clutches 40a, 42a, 44a, 46a, 48a: Actuator 42: Reverse clutch 44: First clutch 46: Second clutch 48: Third clutch 72: Regulator 74: Modulator too, 1
02,104: Directional switching valve 106.108: Shift solenoid 114: Solenoid drive circuit 116: Microcomputer 118 2 CPU (Central Processing Unit) 120: Sensor 124: Waveform shaping circuit 126: Travel amount sensor 128: Accelerator pedal 130: Memory Applicant Toyota Industries Corporation Fujitsu Ltd. Figure 6 Time Figure 7 Vehicle speed (km/h) -

Claims (1)

[Claims] In an automatic transmission that automatically switches gears of the transmission according to a shift map stored in a storage area of a control device, a throttle opening detection device for detecting an opening of a throttle valve is provided, and the control device even though at least one of the following conditions is met: the throttle opening detected by the throttle opening detection device is below a certain value, is decreasing, or is held constant after decreasing. An automatic transmission characterized in that, if the vehicle speed continues to increase for a certain period of time, the transmission is downshifted to a lower gear regardless of the shift map.