JPH0556423B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention electronically controls a friction clutch interposed between an engine and a transmission via an actuator, and also changes the gear position of the transmission. The present invention relates to a speed change control method for an automatic transmission that is electronically controlled via means.

<Conventional technology> In recent years, automatic transmission devices that can automatically select the gear position according to the driving conditions of the vehicle have been developed in order to reduce the burden of driving operations on large freight vehicles, passenger cars, etc. It is considered.

Conventional automatic transmissions are aimed exclusively at small passenger cars, and are equipped with a fluid coupling such as a torque converter between the engine and the planetary gear transmission, using pressure oil as the control medium. A type of transmission equipped with gear position switching means is common.

What is important when developing automatic transmission systems for large freight vehicles is that the number of vehicles produced is significantly smaller than that of passenger cars, so designing new expensive torque converters is not an option due to cost considerations. Therefore, it is desirable to use conventional drive systems such as friction clutches and transmissions, including production equipment, as they are.

<Problems to be Solved by the Invention> However, when an automatic transmission that controls the operation of a friction clutch and a transmission is applied to a large freight vehicle, the vehicle speed may increase even when the exhaust brake is in operation when descending a slope. In such a situation, there is a problem in that the engine is shifted up to a high speed gear even though there is a need to decelerate, resulting in a decrease in engine braking force.

Therefore, an object of the present invention is to provide a speed change control method for an automatic transmission device that can effectively apply engine braking by operating an exhaust brake.

<Means for Solving the Problems> The speed change control method for an automatic transmission according to the present invention includes a clutch actuator 42 that operates a friction clutch 31 connected to an output shaft 30a of an engine 30.
a gear position switching means 51 for switching the gear position of the gear type transmission 32 whose input shaft is connected to the friction clutch; and a gear position switching means 51 for controlling the operation of these and automatically changing the gear position according to the vehicle speed and the accelerator opening. In a speed change control method for an automatic transmission, the present invention detects that the exhaust brake is in operation, and changes the vehicle speed for shift up in an accelerator opening range below a predetermined value to a higher vehicle speed while the exhaust brake is in operation. It is characterized by the fact that

<Function> According to the present invention, when the exhaust brake is operating, the vehicle speed for shift up is changed to a higher vehicle speed in the accelerator opening range below a predetermined value, so the vehicle speed increases while the exhaust brake is operating when going downhill. It is possible to suppress upshifts in situations where the engine brakes would otherwise occur, and the engine brake can be applied effectively.

<Embodiment> As shown in FIG. 1, which shows the concept of an embodiment of an automatic transmission that implements the method of the present invention, this automatic transmission includes a diesel engine (hereinafter simply referred to as engine) 30 and its output shaft 30a. and a gear type transmission 32 which receives the rotational force of the motor through a friction clutch 31. A fuel injection pump (hereinafter simply referred to as an injection pump) 34 is attached to the engine 30 and has an input shaft 33 that rotates at half the rotation speed of the output shaft 30a. Electromagnetic actuators 38 are connected to the racks 35 through links 36, and an engine rotation sensor 39 is attached to the input shaft 33 to generate a rotation speed signal of the output shaft 30a of the engine 30. The friction clutch 31 presses the clutch plate 41 against the flywheel 40 by a well-known clamping means (not shown), and when the air cylinder 42 as a clutch actuator shifts from a non-operating state to an operating state, the clamping means operates in the releasing direction. However, the clutch 31 changes from the connected state to the disconnected state (the disconnected state is shown in FIG. 1). Note that this clutch 31 has a
A clutch stroke sensor 70 is installed to detect the disconnected state or connected state of the clutch by ON/OFF operation, but a clutch touch sensor 43 may be installed instead. Also, gear type transmission 3
A clutch rotation speed sensor 45 is attached to the input shaft 44 of No. 2, which generates a signal of the rotation speed of the input shaft 44 (hereinafter referred to as clutch rotation speed). An air passage 47 is connected to the air chamber 46 of the air cylinder 42, and this is connected to an air tank 48 as a high-pressure air source. An electromagnetic cut valve 49 is installed in the middle of the air passage 47 as an opening/closing means for controlling the supply of working air, and a duty-controlled normally closed electromagnetic valve 50 is also provided to open the air chamber 46 to the atmosphere. is installed. The air cylinder 42 is equipped with the aforementioned clutch stroke sensor 70 that outputs an ON signal when the internal air pressure exceeds a specified value that causes the clutch 31 to be disconnected, and the air tank 48 is further equipped with the clutch stroke sensor 70 that outputs an ON signal when the internal air pressure exceeds a specified value that causes the clutch 31 to be disconnected. Air sensor 7 outputs an ON signal when
2 is installed. To change the gear position of the gear type transmission 32 to achieve each gear stage,
For example, when the driver operates the change lever 54 to a shift position corresponding to a shift pattern as shown in FIG. 51 to change the gear position to a target gear position corresponding to the shift pattern. Here, R indicates reverse gear, N is neutral, 1, 2, and 3 indicate each designated gear, and D _P and D _E indicate any automatic gear from 2nd to 7th gear. , D _P , and D _E ranges, 2nd to 7th speeds are automatically determined based on the driving conditions of the vehicle by the optimum gear position determination process described later. Furthermore, it has a powerful automatic gearbox.
As shown in Figure 3, which shows the shift range between D _P and D _E , which is an economy automatic gear, 2nd speed to D _E range shown by the dotted line and D _P range shown by the solid line.
The shift timing of the 7th gear is set to the higher speed side in the D _P range in order to deal with situations such as when the vehicle is under high load.
The gear shift unit 51 includes a plurality of electromagnetic valves (only one is shown in FIG. 1) 53 that are operated by an operation signal from a control unit 52.
High-pressure operating air is supplied from the air tank 48 via these solenoid valves 53 to drive the gear transmission 32.
A pair of power cylinders (not shown) actuate a select fork (not shown) and a shift fork (not shown), and each power cylinder is operated by an actuation signal given to the electromagnetic valve 53, and the gear type transmission 32 is operated in the order of select and shift. It operates to change the engagement mode of the Furthermore, the gear shift unit 51 is provided with gear position switches 56 as gear position sensors for detecting the positions of each gear, and gear position signals from these gear position switches 56 are output to the control unit 52. Furthermore, a vehicle speed sensor 58 is attached to the output shaft 57 of the gear type transmission 32 to generate a vehicle speed signal, and the accelerator pedal 37 generates a resistance change in the form of a voltage value according to the amount of depression of the accelerator pedal 37. Accelerator load sensor 6 converts into digital signal with converter 59 and outputs it
0 is attached. The brake sensor 62 outputs a high-level brake signal when the brake pedal 61 is depressed. A starter 63 is attached to the engine 30 and starts the engine 30 by meshing with a ring gear on the outer periphery of the flywheel 40 at appropriate times, and a starter relay 64 of the starter 63 is connected to the control unit 52. In addition, the reference numeral 65 in the figure indicates the control unit 5.
2 indicates a microcomputer that is separately attached to the vehicle and performs various controls of the vehicle, and performs drive control of the engine 30 and the like in response to input signals from various sensors (not shown). The microcomputer 65 provides an actuation signal to the electromagnetic actuator 38 of the injection pump 34, and can control the increase/decrease in the rotational speed of the output shaft 30a of the engine 30 (hereinafter referred to as engine rotational speed) by increasing or decreasing fuel.

The control unit 52 is a microcomputer dedicated to the automatic transmission, and is composed of a microprocessor (hereinafter referred to as CPU) 66, a memory 67, and an interface 68 as an input signal processing circuit. interface 6
The input port 69 of No. 8 has the above-mentioned gear selection switch 55, brake sensor 62, accelerator load sensor 60, engine rotation sensor 39, clutch rotation speed sensor 45, gear position switch 56, vehicle speed sensor 58, and clutch touch sensor 43. Output signals are input from a clutch stroke sensor 70 (used to detect the disconnected state or connected state of the friction clutch 31 in place of the clutch stroke sensor 70), a clutch stroke sensor 70, and an air sensor 72. On the other hand, the output port 74 is connected to the above-mentioned microcomputer 65, starter relay 64, and solenoid valve 5.
0, 53 and cut valve 49, respectively, and output signals can be sent to these. In addition, the reference numeral 75 in the figure is an air warning lamp that lights up upon receiving an output from a drive circuit (not shown) when the air pressure in the air tank 48 does not reach a set value, and 76 is an air warning lamp that lights up when the amount of wear of the friction clutch 31 is specified. This is a clutch warning lamp that lights up in response to the output when the value is exceeded.

The memory 67 is composed of a read-only ROM in which programs and data shown in flowcharts in FIGS. 5 to 8 are written, and a read-write RAM. That is, in addition to the above program, the ROM contains a solenoid valve 5 corresponding to the value of the accelerator load signal.
The duty rate α of 0 is stored in advance as a map as shown in FIG. 4, and the corresponding value is read out by referring to this map as appropriate. The gear selection switch 55 described above outputs a select signal and a shift signal as a gear change signal, but the gear position corresponding to a pair of combinations of these two signals is stored in advance as a data map, and the select signal and shift signal are stored in advance. When the gear shift signal is received, this map is referred to and the corresponding output signal is output to each electromagnetic valve 53 of the gear shift unit 51 to adjust the gear position to the target gear position corresponding to the gear shift signal. In this case, the gear position signal from the gear position switch 56 is output when the gear shift is completed, and it is determined whether all gear position signals corresponding to the select signal and shift signal have been output, and a signal indicating whether the meshing is normal or abnormal is determined. It is used to emit. Furthermore, in the ROM, when a target gear exists in the D _P range or the D _E range, based on the vehicle speed, accelerator load, and engine rotation signals,
A map for determining the optimum gear position is also stored.

Here, the speed change control procedure of this embodiment will be explained based on FIGS. 5 to 8.

As shown in FIGS. 5a and 5b, when the program starts, the control unit 52 enters the starting process, and after completing the starting process, inputs a vehicle speed signal,
That value is the specified value (for example, 0Km/h to 3Km/h)
Below, a start process is performed, and above a specified value, a gear change process is performed. However, if the engine speed N _E is below the specified value (for example, idle speed) before calculating the engine speed N _E and performing start processing, it is determined whether the oil pump is stopped or not. It is assumed that the engine has stopped and the startup process is performed again. If the oil pump is not stopped or the engine speed is
If N _E exceeds the specified value, it is determined whether or not the start process is in progress, and if the start process is not in progress, the amount of accelerator depression (hereinafter referred to as the accelerator load signal) is compared with the specified value. Then, it is determined whether the driver has the intention to start the vehicle. During the start process and when the accelerator load signal is above the specified value, the engine speed N _E and the first engine stop (hereinafter referred to as
Compared to the prevention rotation speed N _EST1 (simply written as engine stall),
Engine speed N _E is the first engine stall prevention speed
If N _EST1 or less, the friction clutch 31 is disengaged and the start process is performed. On the other hand, if the accelerator load signal is smaller than the specified value, the engine speed N _E is compared with the second engine stall prevention speed N _EST2 , which is higher than the first engine stall prevention speed N _EST1 , and the engine speed N _E is determined. If the second engine stall prevention rotation speed N _EST2 is lower than the second engine stall prevention rotation speed N _{EST2, the clutch is disengaged and the start processing is performed. If the engine rotation speed N E exceeds} the second engine stall prevention rotation speed N _EST2 or If the engine stall prevention rotation speed _NEST1 is exceeded, normal processing is resumed.

In the starting process shown in Figure 6, the engine speed N _E
A signal is input, and it is determined whether the value is within the stop range of the engine 30. If the engine 30 is stopped, a clutch connection signal is output and a time lag is taken, and the friction clutch 31 is set to the normal pressure and normal state. Connect in the state of . When the friction clutch 31 is connected at the normal pressure and in the normal state, the friction clutch 31 is disengaged to some extent from this position and the drive theory of the vehicle shifts from the rotating state to the stopped state (hereinafter referred to as the half-clutch state). (denoted as a point) is corrected depending on the wear condition of the facing of the friction clutch 31, the presence or absence of a loaded object, etc. In other words, the stroke of the clutch plate 41 from the LE point until the friction clutch 31 is completely engaged is always approximately constant.
The friction clutch 31 is smoothly engaged regardless of the state of the vehicle. When the LE point is corrected, it is determined whether the position of the change lever 54 and the gear position are the same, that is, the shift signal and the gear position signal are the same, and the target gear (D _E ,D When the _P range is selected, the gear type transmission 32 is set (for example, 2nd speed) in advance.
Determine whether the gear positions are aligned. If the position of the change lever 54 and the gear position are different, it is determined whether the air in the main air tank 48 has reached a specified pressure, and if the pressure has been reached, the friction clutch 31 is activated. Then, the air in the air tank 48 is used to operate an actuator (not shown) to automatically align the gear position with the position of the change lever 54, connect the friction clutch 31, and connect the air tank 48 (main tank) and the sub tank (not shown). After turning off the switching solenoid valve, turn the change lever 5 again.
It is determined whether the position No. 4 and the gear position are the same.
In addition, if the air in the air tank 48 has not reached the specified pressure, it is determined whether the air in the sub-tank has reached the specified pressure, and if the air has reached the specified pressure, the switching solenoid valve is turned on. Friction clutch 3
1 and operate the power cylinder with the air in the sub-tank to automatically select the gear position corresponding to the position of the change lever 54. If the air in the sub-tank has not reached the specified pressure, the air warning lamp 75 is turned on to notify the driver that the air in the air tank 48 and the sub-tank is below the specified pressure. On the other hand, if the position of the change lever 54 and the gear position are the same, a relay for enabling starter is output. When the starter enable relay is output, the starter 63 is started and the engine 30 is activated.
If the engine 30 starts, turn off the starter enable relay, and if the engine 30 does not start, change the position of the change lever 54 again. Determine whether the gear positions are the same. When the starter enable relay is turned off,
Check whether the air in the air tank 48 and sub-tank has reached the specified pressure. If the air has not reached the specified pressure, turn on the air warning lamp 75 and repeat the judgment until the air reaches the specified pressure. When the air warning lamp 75 is reached, the air warning lamp 75 is turned off and the startup process is completed.

After the start process is completed, the vehicle speed signal is read, and if it is below a specified value, the start process begins. As shown in FIGS. 7a and 7b, first, the CPU 66 outputs an ON signal to the cutoff valve 49 to disengage the friction clutch 31, thereby disengaging the friction clutch 31. Next, it is determined whether the position of the change lever 54 and the gear position are the same, and if NO, the gear position is adjusted to the target gear position. When the position of the change lever 54 and the gear position become the same, it is determined again whether the vehicle speed is smaller than the specified value, and if NO (the vehicle speed is higher than the specified value), the accelerator load signal detection step described later is performed. Proceed to. On the other hand, if this is not the case, the next gear position that reaches the target gear is read from the shift signal to see if it is neutral or not.
Perform LE point correction. If the gear position is NO, which is other than neutral, the friction clutch 31 is connected to the LE point. Next, it is determined whether the accelerator load signal value exceeds the specified value (voltage low enough to indicate the driver's intention to start), and if NO, indicating that the driver has no intention to start, the above Repeat each step. On the other hand, it is determined that there is an intention to take off.
If YES, proceed to the next step, detect the accelerator load signal value, and read the optimum duty rate α corresponding to this value from the map shown in FIG. Then, the obtained pulse signal with the optimum duty rate α is outputted to the solenoid valve 50, and the friction clutch 31 is gradually connected. At this point, the CPU 66 outputs a selection signal to the input port 69 to continue inputting the engine speed N _E signal, and the engine speed N _E over time based on this engine speed N _E signal is stored in the memory 67. The engine speed N _E and clutch speed N _CL are sequentially stored in the internal RAM.
As shown in FIG. 9, which shows an example of the change in , arithmetic processing is performed to find the peak point M, and until the peak point M is detected, the process goes to NO and repeats from the accelerator load signal detection step. On the other hand, when the peak point M is detected, the solenoid valve 50 is held ON from _T1 . Note that the peak point M is at engine 3.
This occurs because the output shaft 30a of the zero output shaft 30a decreases as power begins to be transmitted to the drive wheels through the friction clutch 31 as the rotation of the input shaft 44 of the gear type transmission 32.

Next, the LEOFF routine is executed. this
The LEOFF routine is used to deal with cases where the vehicle is slightly moved with the clutch partially engaged rather than a normal start.The LEOFF routine first determines whether the vehicle speed is greater than a specified value, and if the vehicle speed is greater than the specified value (YES) In this case, it is determined that it is a normal start, and the LEOFF routine ends and returns to the start flow. On the other hand, in the case of NO, it is determined whether or not the next accelerator pedal 37 is depressed.
If YES, the LEOFF routine also ends,
If NO, the friction clutch 31 is gradually disengaged by off-duty until the LE point is reached. Meanwhile, a determination is made as to whether or not the accelerator pedal 37 is being depressed.
When the pedal is depressed, the process returns to the accelerator load signal detection step described above. After the friction clutch 31 has retreated to the LE point, the process returns to the step of determining the position of the change lever 54 and the gear position described above.

When the LEOFF routine is completed and it is determined that the vehicle has started normally, the friction clutch 31 is connected from the half-clutch state at the LE point to the clutch engagement state.
Engine speed after passing peak point M at this time
Considering that N _E gradually decreases as the clutch rotation speed N _CL , which corresponds to the rotation of the input shaft 44 of the gear type transmission 32, increases, this engine rotation speed
Control is performed so that the rate of decrease in N _E falls within a predetermined range and the start shock becomes smaller. That is, first, it is determined whether or not the rate of decrease in engine speed ΔN _E for each predetermined period of time is less than or equal to the first set value |x ₁ | shown in FIG. If YES, after executing the above-mentioned LEOFF routine, the accelerator load signal is detected again, the optimum duty rate α corresponding to this value is determined, and the friction clutch 31 is gradually engaged based on this duty rate α. After this, it is determined whether the engine speed reduction rate ΔN _E is less than or equal to the second set value |x ₂ | (|x ₁ | < | x ₂ |), and if NO, the process returns to before the LEOFF routine described above. Then, a loop is repeated in which the engine speed reduction rate ΔN _E is kept constant. On the other hand, if the engine speed reduction rate ΔN _E is larger than |x ₁ |, this engine speed reduction rate ΔN _E becomes the third set value |y ₂ |
Determine whether it is less than or equal to (|x ₂ | < | y ₂ |). If YES here, after executing the LEOFF routine, the friction clutch 31 is gradually disengaged by off-duty. After that, it is determined whether the engine speed reduction rate ΔN _E is less than or equal to the fourth set value |y ₁ | (|y ₁ | < | y ₂ |), and if NO, the loop of cutting off the friction clutch 31 is repeated. . In the case of YES, or in the case of NO in the step of determining whether the engine speed reduction rate ΔN _E is less than or equal to |y ₂ |, in the step of determining whether the engine speed reduction rate ΔN _E is less than or equal to |x ₂ | In the case of YES, at this point the engine speed reduction rate ΔN _E falls approximately within the shaded area in FIG. Therefore, conditions have been established for switching the friction clutch 31 to the engaged state in the half-clutch state without causing a start shock and without prolonging the start time excessively. Hold. After this, the CPU 66 calculates the difference between the engine speed N _E and the clutch speed N _CL to a specified value (for example, |N _E −N _CL |=
10 rpm) or less, and if NO, the above-mentioned loop is repeated, and after a predetermined time lag at _T2 , which is the time of YES, the solenoid valve 50 is fully opened and clutch meet is performed. . After this, after a predetermined time lag on the condition that the engine speed N _E is equal to or higher than the idle speed,
The CPU 66 calculates the slip rate of the friction clutch 31 (difference between engine speed N _E and clutch speed N _CL / engine speed N _E ) and compares this value with a specified value. Return to flow. On the other hand, when the slip rate is above the specified value, it is determined that the amount of wear on the friction clutch 31 is large, and an ON signal as a clutch wear signal is sent to the clutch warning lamp 76 through the output port 74 and a drive circuit (not shown). The clutch warning lamp 76 is turned on.

After the starting process is completed, the CPU 66 reads the vehicle speed signal, and if it exceeds a specified value, starts the gear change process. As shown in Fig. 8 a, b, and c, first, a selection signal is given to the input port 69 to check whether the brake has failed or not.
If YES, downshift one gear at a time to stop the vehicle as described later. On the other hand, in the case of brake fail NO, it is checked using, for example, an acceleration sensor whether or not sudden braking is being applied with deceleration exceeding a certain value, and if YES, the gear change operation described below is performed. Since the braking distance becomes longer, the system returns to the main flow and temporarily blocks the gear shifting operation. However, if the friction clutch 31 is disengaged even when the brakes are applied suddenly, it is determined that the gear shift is in progress, so the gear shift operation is completed and the friction clutch 31 is connected.

On the other hand, when there is no sudden braking operation or when the friction clutch 31 is disengaged as described above even during sudden braking, the position of the change lever 54 is read, and this is the designated shift of 1, 2, or 3 other than D _P and D _E. Determine whether it is a gear classification, D _P or _DE automatic gear stage classification, R gear classification, or N gear classification.

In the case of designated gears 1, 2, and 3, it is determined whether the position of the change lever 54 and the gear position are the same, and if YES is selected, the process returns to the main flow, and if NO is selected, the process proceeds to the next step. In this step, the change lever 54 is positioned at one of target gears 1, 2, and 3, and the current gear position before shifting is D _P , D _E
It is determined whether or not it corresponds to a downshift from the range. If YES, engine 3
It is determined whether or not it is possible to downshift without overrunning the 0 revolution. If NO, the system proceeds to the next step and warns the driver of an overrun with a reverse warning buzzer, without changing gears. Return to the main flow. If the determination as to whether or not there is an overrun is YES, a downshift operation is performed by one gear from the current gear position as follows. As shown in FIG. 11, which shows the operational concept of this downshift operation, a control signal from the control rack 35 is outputted to the electromagnetic actuator 38 via the output port 74 and the microcomputer 65, and the engine speed N _E is maintained as it is. Hold in state. Then, an ON signal is output for a predetermined period of time to the cut valve 49 via the output port 74 to disengage the friction clutch 31, and a control signal is output to each electromagnetic valve 53 of the gear shift unit 51 to shift the gear by one gear from the previous gear position. Perform a downshift to the lower gear position. Next, the output port 74
The microcomputer 65 then outputs a voltage signal to the electromagnetic actuator 38 as an accelerator pseudo signal to increase the engine speed N _E so that the same rotation as the clutch rotation speed N _CL increases, thereby increasing the clutch rotation speed N _CL after shifting. The engine rotation speed N _E is matched, air is removed from the air cylinder 42, and the friction clutch 31 is moved to the half-clutch state at the LE point. Next, the friction clutch 31 is connected at the optimum duty rate α corresponding to the accelerator load signal, and the engine rotational speed N _E and clutch rotational speed are
The difference from N _CL is compared with a specified value preset for each gear, and the operation of connecting the friction clutch 31 at the duty rate α is repeated until |N _E −N _CL | becomes equal to or less than the specified value. Then, after |N _E -N _CL
The connection is completed, the accelerator pseudo signal is released, and the process returns to the main flow.

On the other hand, if the result of the determination as to whether this corresponds to a downshift from the D _P or D _E range is NO, a determination is made as to whether or not it is a shift up. If this is YES, perform the shift up operation as follows and return to the main flow. As shown in Fig. 12, which shows the concept of the shift-up operation,
A control signal for the control rack 35 is output to the electromagnetic actuator 38 via the output port 74 and the microcomputer 65, and the engine speed N _E is returned to idle speed. After the friction clutch 31 is disengaged, the gear position is output to each solenoid valve 53 via the output port 74 so that it matches the target gear position, which is one of the designated gear positions 1, 2, and 3. do. After that, perform the operations after outputting the accelerator pseudo signal for the downshift operation to match the engine speed N _E with the clutch rotation speed N _CL after shifting, complete the engagement of the friction clutch 31, and switch the main Return to flow. In addition, as a result of the above judgment on whether or not to shift up, if NO, it is judged whether or not the overrun is within the range, and if this is YES, the engine speed _N is held as it is, and the friction clutch is 31, the gear position is set to one of the designated gears 1, 2, and 3, and the operations after outputting the accelerator pseudo signal of the downshift operation are performed, and the process returns to the main flow. Furthermore, if the result of the determination as to whether or not the overrun is within the range is NO, a warning is issued by a warning buzzer.

The above operation is performed when the result of the determination of the position of the change lever 54 is the designated gear stage 1, 2, or 3, and the result of the determination of the position of the change lever 54 is D _P , If the automatic gear position is D _E , the following operations are performed. That is, the vehicle speed and the amount of depression of the accelerator pedal 37 are detected, and it is determined whether or not the exhaust brake device (exhaust brake) is being used. If NO, the map A shown in FIG. 13 is detected.
, and further determines whether the change lever 54 is in the D _P range or the D _E range, and selects the target shift in each range from the preset map A to D _P or D _E as shown in Fig. 13. The optimum gear stage to be considered as the gear stage is determined. After this, it is determined whether the gear position matches the optimum gear position.
If YES, the process returns to the main flow, and if NO, the process moves to a step to determine whether or not to shift up, and the same speed change operation as described above is performed.

In map A shown in Figure 13, the D _P and D _E ranges are shown with the same line (a solid line for upshifting and a dotted line for downshifting) to make it easier to understand when upshifting and downshifting. However, as shown in Figure 3, D _P is actually better than D _E
is set to a higher speed.

If an exhaust brake device is used, the first
Select map B shown in Figures 4 and 15. In this map B, when the driver does not press down on the accelerator pedal 37 as shown in the figure, the vehicle speed is set to a higher speed when the vehicle is shifted to a higher gear position. In other words, when the exhaust brake system is operating and the driver is not pressing the accelerator pedal 37 when driving downhill, etc., even if the vehicle speed increases, the vehicle speed is set to the high speed side. Therefore, the gear position on the low speed side is maintained, further enhancing the exhaust braking effect and engine braking effect. When map B is selected, it is determined whether the change lever 54 is in the D _P range or the _DE range, and from map B, the optimum gear position that is regarded as the target gear position in each range of D _P or D _E is determined. After this, it is determined whether the gear position matches the optimum gear position, and if the answer is YES, the process returns to the main flow, and if the answer is NO, the process moves to the step of determining whether to shift up or not, and the process is the same as above. A speed change operation is performed.

If the result of the determination of the position of the change lever 54 is R, the CPU 66 determines whether or not the gear position is set to R as the target gear, and selects YES, which is currently in reverse operation. If the answer is NO, which is an erroneous operation, then the engine speed N _E is set to idling speed and the friction clutch 31 is disengaged in the same manner as described above. Then, in order to return the gear position to neutral, it is outputted to each solenoid valve 53 via the output port 74,
After turning on the reverse warning lamp that indicates a gear shift error, the friction clutch 31 is connected and the process returns to the main flow.

Furthermore, if the result of the determination of the position of the change lever 54 is N gear, it is determined whether the change lever 54 has moved within a predetermined time, that is, whether the driver has simply passed through N gear during the shift operation. Determine whether or not there is. If the result of this judgment is YES, which is in the middle of a gear shift operation, the position of the change lever 54 and the gear position are judged as described above, and the flow returns to the main flow, or the shift is performed by upshifting and downshifting to the main flow. An operation to return to the flow is performed. However, if the N gear is selected (NO), reduce the engine speed N _E to idling speed, disengage the friction clutch 31 to set the gear position to neutral, and then connect the friction clutch 31 again to return to the main flow. return.

In this embodiment, the friction clutch 31 is operated by using air pressure from an air tank 48 installed in the vehicle.
Although the air cylinder 42 for actuation is driven, it is of course possible to use hydraulic pressure as the control medium. However, in this case, a new hydraulic pressure generation source such as an oil pump must be added, which may increase costs. Furthermore, it goes without saying that the speed change control procedure, shift pattern, etc. shown in this embodiment can be modified in detail as necessary.
The present invention can also be applied to vehicles equipped with gasoline engines. Furthermore, a dummy clutch pedal may be installed for the driver who is switching from a manual transmission, and in this case, the clutch pedal functions in priority over the air cylinder 42 in the R gear and the designated gears 1, 2, and 3. It is also possible to set it so that

<Effects of the Invention> According to the shift control method for an automatic transmission of the present invention, it is possible to suppress useless shift-up in situations where the vehicle speed increases while the exhaust brake is operating when descending a slope, and the exhaust brake This has the effect that the engine brake can be effectively applied by the operation.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an automatic transmission according to an embodiment of the present invention, Fig. 2 is a conceptual diagram showing an example of its shift pattern, and Fig. 3 is a shift characteristic of its D _P range and D _E range. FIG. 4 is a graph showing an example of a map for determining the duty rate. FIGS. Figure 9 is a graph showing an example of changes over time in the engine speed and clutch rotation speed during the gear shift, Figure 10 is a graph showing the area of change rate of the engine speed during the gear shift, and Figure 11 is a graph showing the change rate of the engine speed during the gear shift. Fig. 12 is a conceptual diagram of the operation during shift-up operation, Fig. 13 is a graph showing the shift characteristics of map A in the D _P range and D _E range, Fig. 14 is the D _P range and D _E range. FIG. 15 is a graph showing the speed change characteristics of map B during upshifts in the D _P range and _DE range. In the drawing, 30 is an engine, 30a is an output shaft of the engine, 31 is a friction clutch, 32 is a gear type transmission, 34 is a fuel injection pump, 35 is a control rack, 37 is an accelerator pedal, 38 is an electromagnetic actuator, and 42 is an air pump. 44 is an input shaft of a gear type transmission, 48 is an air tank, 50 is a solenoid valve, 51 is a gear shift unit, 52 is a control unit, 54 is a change lever, and 65 is a microcomputer.

Claims (1)

[Scope of Claims] 1. A clutch actuator 42 for operating a friction clutch 31 connected to the output shaft 30a of the engine 30; and a gear position switch for changing the gear position of a gear type transmission 32 whose input shaft is connected to the friction clutch. means 51, and a speed change control method for an automatic transmission which controls these operations and automatically changes the gear position according to vehicle speed and accelerator opening, comprising: detecting that the exhaust brake is in operation; 1. A shift control method characterized in that during operation, a vehicle speed for shift up is changed to a high vehicle speed in an accelerator opening range below a predetermined value.