JP5761487B2 - Vehicle speed change control device - Google Patents

Description

  The present invention relates to a vehicle speed change control device, and more particularly to a speed change control device that executes a control for automatically downshifting (hereinafter, this control is referred to as a shift down brake) when an accelerator is turned off in order to enhance an engine braking action.

For example, vehicles such as trucks and buses are equipped with auxiliary brakes in addition to service brakes (foot brakes) because the vehicle weight is large and changes greatly depending on the loading capacity and the number of passengers.
This type of auxiliary brake includes an exhaust brake that forcibly closes the exhaust passage of the engine to enhance the engine brake action, and exhausts compressed air from the cylinder by forcibly opening the exhaust valve immediately before the compression top dead center of each cylinder. There is a compression-release type engine brake that enhances the engine braking action, or a retarder that applies a rotational resistance to a propeller shaft or the like by utilizing a fluid stirring resistance or electromagnetic induction of an electromagnet. By operating these auxiliary brakes in response to the driver's accelerator-off operation, the burden on the service brake is reduced, and the driver's fatigue can be reduced by reducing the frequency of the service brake operation.

On the other hand, in recent years, automatic transmissions have been put into practical use in which the conventional shift operation of a manual transmission and the clutch operation associated with the shift are automated by an actuator, and the function of the automatic transmission can also be used as an auxiliary brake. Yes (see, for example, Patent Document 1). In other words, since this type of automatic transmission can arbitrarily switch the gear stage, the shift control device that performs shift control automatically performs a downshift as a downshift brake when the accelerator is turned off. The brake function is enhanced to function as an auxiliary brake.
For example, in the technique of Patent Document 1, when the first switch of the switch provided in the driver's seat is operated, if the accelerator is turned off, only the exhaust brake or the exhaust brake and the compression release engine brake are operated, and the second switch of the switch is operated. When the accelerator is turned off at the time of operation, in addition to these auxiliary brakes, the shift control device executes a one-stage downshift from the current gear stage to achieve a higher engine braking action.

Patent No. 3030758

  However, since the engine braking action required at the time of accelerator-off operation differs depending on the driving situation, the technique of Patent Document 1 that can be uniquely shifted down by one step in any situation can provide an appropriate engine braking action. There wasn't.

For example, the engine brake action required according to the driver's own preference for the strength of the engine brake is different, and the engine brake action required according to the undulation and congestion of the driving road is different, but the patent In some cases, the technique of Document 1 cannot achieve an optimal engine braking action. For this reason, the effect of the above-described downshift brake, that is, the effect of reducing the service brake load and the driver's fatigue could not be sufficiently obtained.
The present invention has been made to solve such problems, and the object of the present invention is to always perform a downshift to the optimum gear ratio during accelerator-off operation to generate an appropriate engine braking action. An object of the present invention is to provide a vehicular speed change control device.

In order to achieve the above object, the invention of claim 1 shifts the transmission so as to achieve the target gear ratio obtained from the driver's accelerator operation amount and the vehicle speed, while the driver's accelerator off operation performs the target gear. In a vehicle transmission control device that performs a downshift for downshifting the transmission by setting the ratio to a lower gear ratio side than the current gear ratio, a stop position provided at the driver's seat to stop the downshift brake, A change-over switch that can be switched to a weak position where the downshift brake is operated with a weak effect and a strong position where the downshift brake is operated with a strong effect, and when the changeover switch is switched to the stop position, the downshift brake is stopped. When shifting to the weak and strong positions, the downshift brake is activated and the target gear is set in the strong position compared to the weak position. By setting the ratio to a lower gear ratio side is that a shift control means for shifting down.

Therefore, the shift down brake is stopped when the changeover switch is changed to the stop position, while the shift down brake is activated both when the changeover switch is changed to the weak position and the strong position, and in the strong position compared to the weak position. The target gear ratio is set on the lower gear ratio side. As a result, the effect of the downshift brake is further increased in the strong position as compared with the weak position, and the effect of the downshift brake can be switched between the strong and weak two stages. Therefore, for example, a more appropriate engine braking action can be generated as compared with the technique of Patent Document 1 in which the gear is uniquely shifted down by one stage.

According to a second aspect of the present invention, in the first aspect, when the shift control means switches the changeover switch to the weak position or the strong position, the shift control means compares it with the weak position according to a preset relationship between the vehicle speed and the braking force. was calculated as the target braking force higher braking force from the vehicle speed at the strong position Te, a gear ratio capable of achieving the calculated target braking force is to downshift by setting the target gear ratio.
Therefore, when the changeover switch is switched to the weak position or the strong position, a higher braking force is calculated as a target braking force from the vehicle speed at the strong position than at the weak position, and a gear ratio that can achieve the calculated target braking force is obtained. The target gear ratio is set and shifted down. In this way, the target braking force that should be actually generated is specifically calculated, and the shift-down brake is executed based on the target gear ratio that can achieve the target braking force, so that it is very close to the target braking force after the downshift. Engine braking, that is, engine braking that is optimal for the current situation can be generated.

According to a third aspect of the present invention, in the first or second aspect, when the shift control means shifts down based on the set target gear ratio and the engine speed exceeds the upper limit value, the engine speed can be limited to the upper limit value. The target gear ratio is corrected to the high gear ratio side, and the gear is shifted down based on the corrected target gear ratio.
Therefore, if the engine speed exceeds the upper limit value after shifting down based on the set target gear ratio, the target gear ratio is corrected to the high gear ratio side so that the engine speed can be limited to the upper limit value. Since the gear is shifted down based on the gear ratio, over-rotation of the engine is prevented in advance.

According to a fourth aspect of the present invention, in the first to third aspects, when the engine speed exceeds the upper limit as the vehicle speed increases due to the downhill road after the downshift based on the target gear ratio, The target gear ratio is corrected to the high gear ratio side so that the rotation speed can be limited to the upper limit value, and the gear ratio is controlled based on the corrected target gear ratio.
Therefore, when the engine speed exceeds the upper limit as the vehicle speed increases due to the downhill road after the downshift based on the target gear ratio, the target gear ratio is set to a high gear so that the engine speed can be limited to the upper limit. Since the gear ratio is corrected to the specific side and the gear ratio is controlled based on the corrected target gear ratio, over-rotation of the engine is prevented in advance.
According to a fifth aspect of the present invention, in the first to fourth aspects, the changeover switch includes an auxiliary brake position for operating an auxiliary brake mounted on the vehicle in addition to the stop position, the weak position, and the strong position, and the shift control means is provided. When the changeover switch is switched to the auxiliary brake position, only the auxiliary brake is operated, and when the changeover switch is changed to the weak position and the strong position, the auxiliary brake is operated together with the shift down brake, and the strong position is compared with the weak position. Then, the target gear ratio is set to the lower gear ratio side.
Therefore, a slight shift shock is generated when the downshift brake is operated, but in a situation where a relatively weak engine brake is required, the shift brake does not occur because the auxiliary brake deals with it, minimizing the disadvantages of the downshift brake. It is suppressed.
According to a sixth aspect of the present invention, in the first to fifth aspects, the shift control means prohibits execution of the downshift brake at a speed lower than a predetermined vehicle speed.
Therefore, since the execution of the downshift brake is prohibited in the low vehicle speed range where the shift shock and the engine brake become conspicuous, the driving feeling is prevented from being deteriorated.

As described above, according to the vehicle transmission control apparatus of the first aspect of the present invention, the shift down brake is stopped when the changeover switch is changed to the stop position, and both when the changeover switch is changed to the weak position and the strong position. In addition to operating the downshift brake, the target gear ratio is set to the lower gear ratio side in the strong position compared to the weak position, so the effect of the downshift brake can be switched between the strong and weak two stages, and the appropriate engine braking action Can be generated.
According to the vehicle shift control device of the invention of claim 2, in addition to claim 1, the target braking force to be actually generated according to the weak position and the strong position of the changeover switch is specifically calculated, and the target Since the gear is shifted down based on the target gear ratio at which the braking force can be achieved, it is possible to generate an engine brake very close to the target braking force after the shift down, that is, an engine brake optimum for the current situation.

According to the vehicle transmission control device of the invention of claim 3, in addition to claim 1 or 2, when the engine speed exceeds the upper limit value when the gear is shifted down based on the set target gear ratio, the engine speed is set to the upper limit value. Since the target gear ratio is corrected to the high gear ratio side so that it can be limited to a lower gear ratio, the shift down brake is started so that over-rotation of the engine is prevented and an appropriate engine rotation range is always maintained. be able to.
According to the fourth aspect of the present invention, in addition to the first to third aspects, the engine speed increases to the upper limit as the vehicle speed increases due to the downhill road after the downshift based on the target gear ratio. If the engine speed exceeds the upper limit, the target gear ratio is corrected to the high gear ratio side so that the engine speed can be limited to the upper limit, and the gear ratio is controlled based on the corrected target gear ratio. In this case, it is possible to prevent the engine from over-rotating.
According to the fifth aspect of the present invention, in addition to the first to fourth aspects, the shift shock of the downshift brake is provided in order to cope with the auxiliary brake in a situation where a relatively weak engine brake is required. Defects can be minimized.
According to the vehicle shift control device of the sixth aspect of the invention, in addition to the first to fifth aspects, the execution of the downshift brake is prohibited at a speed lower than the predetermined vehicle speed, so that the deterioration of the running feeling can be prevented in advance. it can.

1 is an overall configuration diagram showing a truck drive system to which a vehicle transmission control device of an embodiment is applied. It is a control block diagram which shows the process of ECU for calculating a target gear stage.

Hereinafter, an embodiment of a transmission control apparatus for a vehicle embodying the present invention will be described.
FIG. 1 is an overall configuration diagram showing a drive system of a truck to which a vehicle shift control device of this embodiment is applied. However, the application target of the speed change control device of the present invention is not limited to a truck, and may be applied to, for example, a bus or a passenger car.
A vehicle is equipped with a diesel engine (hereinafter referred to as an engine) 1 as a driving power source. The engine 1 is configured as a so-called common rail type engine that supplies high-pressure fuel accumulated in a common rail by a pressurizing pump to the fuel injection valve of each cylinder and injects the fuel into the cylinder as the fuel injection valve opens.

The type of the engine 1 is not limited to this, and may be a conventional type diesel engine that controls fuel injection to each cylinder according to the operation of the control rack, or may be a gasoline engine.
Further, the valve mechanism 1a of the engine 1 is configured to be able to forcibly open the exhaust valve of each cylinder, whereby the engine 1 functions as a compression release type engine brake which is a kind of auxiliary brake. In other words, the exhaust valve is forcibly opened immediately before the compression top dead center of each cylinder during the driver's accelerator-off operation, whereby the compressed air is discharged from the cylinder and the engine braking action is enhanced. The amount of compressed air discharged from the cylinder changes in accordance with the crank angle when the exhaust valve is forcibly opened, and the effectiveness of the compression release type engine brake changes accordingly. Therefore, in the present embodiment, the forced opening of the exhaust valve is performed by selecting one of the two preset crank angles, and the effectiveness when the compression release type engine brake is operated is divided into two levels. Switching is possible.

  An input shaft 3a of an automatic transmission (hereinafter simply referred to as a transmission) 3 is connected to an output shaft 1b of the engine 1 via a clutch device 2. The rotation of the engine 1 is transmitted to the transmission 3 when the clutch device 2 is connected. It has come to be. The transmission 3 is based on a manual transmission having 12 forward speeds (1st to 12th speeds) and 1 reverse speed. As described below, the transmission 3 is associated with the speed change operation and the speed change. The connection / disconnection operation of the clutch device 2 is automated. Needless to say, the gear position of the transmission 3 is not limited to the above and can be arbitrarily changed.

The clutch device 2 is configured as a friction clutch that is connected to the flywheel 4 by press-contacting the clutch plate 5 with a pressure spring 6 and is disconnected by separating the clutch plate 5 from the flywheel 4. An air cylinder 8 is connected to the clutch plate 5 via an outer lever 7, and an air tank 11 filled with compressed air is connected to the air cylinder 8 via an air passage 10 in which an electromagnetic valve 9 is interposed.
When the electromagnetic valve 9 is opened, compressed air is supplied from the air tank 11 to the air cylinder 8 via the air passage 10, and the air cylinder 8 is activated to separate the clutch plate 5 from the flywheel 4 via the outer lever 7. Thus, the clutch device 2 is switched from the connected state to the disconnected state. On the other hand, when the solenoid valve 9 is closed, the air cylinder 8 stops operating due to the stop of the supply of compressed air, so that the clutch plate 5 is pressed against the flywheel 4 by the pressure spring 6, and thereby the clutch device 2 is released from the disconnected state. Switch to connected state. As described above, the air cylinder 8 is operated in accordance with the opening and closing of the electromagnetic valve 9 so that the clutch device 2 can be automatically connected and disconnected.

A change lever 13 is provided in the driver's seat of the vehicle. Although not shown, the change lever 13 is located between the parking range (P range), the reverse range (R range), the neutral range (N range), and the drive range (D range). The switching operation is possible with. As with ordinary vehicles, the N range is a range that does not transmit the rotation of the engine 1, the P range is a range that restricts movement of the vehicle in addition to the N range function, and the D range is an automatic shift based on a preset shift map. The R range and R range are the reverse ranges.
The configuration of the change lever 13 is not limited to this. For example, in addition to the D range, a shift up range (+ range) and a shift down range (− range) are provided as manual shift ranges, and the driver's operation The gear stage may be arbitrarily switched according to the above.

  The transmission 3 is provided with a gear shift unit 14 for switching gear stages. Although not shown, the gear shift unit 14 includes a plurality of air cylinders that operate shift forks corresponding to the respective gear stages in the transmission 3, and It incorporates multiple solenoid valves that actuate the air cylinder. The gear shift unit 14 is connected to the above-described air tank 11 through the air passage 12, and compressed air from the air tank 11 is supplied to the corresponding air cylinder according to opening and closing of each solenoid valve, and the air cylinder is operated. When the corresponding shift fork is switched, the gear stage of the transmission 3 is switched according to the switching operation. As described above, the air cylinder is operated in accordance with the opening / closing of the electromagnetic valve of the gear shift unit 14, and the transmission 3 can be automatically operated for shifting.

In the passenger compartment, an input / output device (not shown), a storage device (ROM, RAM, etc.) for storing control programs and control maps, an ECU (control unit) equipped with a central processing unit (CPU), a timer counter, etc. 21 is installed, and comprehensive control of the engine 1, the clutch device 2, and the transmission 3 is performed.
On the input side of the ECU 21 are an engine rotation speed sensor 22 that detects the rotation speed Ne of the engine 1, a clutch rotation speed sensor 23 that detects the rotation speed (clutch rotation speed) of the input shaft 3 a of the transmission 3, and a change lever 13. A lever position sensor 24 for detecting the switching position, a gear position sensor 25 for detecting the gear position of the transmission 3, an accelerator sensor 27 for detecting the operation amount Acc of the accelerator pedal 26, and an output shaft 3b of the transmission 3 are provided on the vehicle speed. Sensors such as a vehicle speed sensor 28 for detecting V and an auxiliary brake changeover switch 29 provided in the driver's seat are connected.

The auxiliary brake switching switch 29 is a switch for the driver to arbitrarily switch the operating state of the auxiliary brake mounted on the vehicle. In addition to the operating state of the compression release engine brake described above, other auxiliary brakes to be described later are provided. It is also possible to switch the operating state of the downshift brake.
Specifically, the auxiliary brake changeover switch 29 includes an OFF position (stop position) at which all auxiliary brakes are stopped, a PT weak position (auxiliary brake position) at which the compression release engine brake is operated with a weak effect, a compression release engine. PT strong position (auxiliary brake position) where the brake is operated with a strong effect, SDB weak position (weak position) where the shift down brake is operated with a weak effect in addition to the strong-pressing pressure-release engine brake, and a strong effect in addition to圧宿open engine braking has been arbitrarily can be switched between 5 position of the SDB strong position to operate in strong potency downshift brake (strong position).

Further, the electromagnetic valve 9 of the clutch device 2 and the electromagnetic valves of the gear shift unit 14 are connected to the output side of the ECU 21, and although not shown, a pressure pump for common rail pressure accumulation and fuel for each cylinder are not shown. An actuator for forcibly opening the exhaust valve of each cylinder as an injection valve and a compression release type engine brake is connected.
In addition, you may make it provide ECU for engine control separately from ECU21, for example, without controlling comprehensively by single ECU21 in this way.

For example, the ECU 21 determines the rail pressure of the common rail accumulated by the pressure pump from a map (not shown) based on the engine speed Ne detected by the engine speed sensor 22 and the accelerator operation amount Acc detected by the accelerator sensor 27. The fuel injection amount to each cylinder is calculated, and the fuel injection timing is calculated from a map (not shown) based on the engine speed Ne and the fuel injection amount Q. The pressurizing pump is driven and controlled based on these calculated values, and the engine 1 is operated while driving and controlling the fuel injection valves of the respective cylinders.
Further, the ECU 21 calculates the target gear stage tgtG from a shift map (not shown) based on the accelerator operation amount Acc and the vehicle speed V detected by the vehicle speed sensor 28 when the D range of the change lever 13 is detected by the lever position sensor 24. calculate. Then, while opening and closing the electromagnetic valve of the clutch device 2 and connecting and disconnecting the clutch device with the air cylinder 11, the target electromagnetic valve of the gear shift unit 14 is opened and closed and the corresponding shift fork is switched and operated with the air cylinder. The gear stage tgtG is achieved, whereby the vehicle is always driven with an appropriate gear stage.

On the other hand, when the ECU 21 determines the driver's accelerator-off operation based on the accelerator operation amount Acc, the operation of all the auxiliary brakes is stopped when the auxiliary brake selector switch 29 is in the OFF position, while at the time of switching to the other four positions. The auxiliary brake is operated according to the switching position. That is, since all the auxiliary brakes are not operated in the OFF position, the original engine brake generated by the engine 1 in which the fuel injection is stopped by the accelerator off is applied to the vehicle, and the braking force according to the pedaling force is operated when the assist brake is operated. Works.
In the PT weak position, the exhaust valve of each cylinder is forcibly opened by the actuator at a crank angle with a small amount of compressed air discharged from the cylinder, thereby operating the compression release type engine brake with a weak effect. Further, at the PT strong position, the compression opening type engine brake is operated with a strong effect by forcibly opening the exhaust valve of each cylinder at a crank angle with a large discharge amount of compressed air.

In the SDB weak position, the shift down is executed by setting the target gear stage tgtG as the shift down brake to the lower gear ratio side than the currently selected gear stage while performing the compression release type engine brake having a strong effect. Also, at the SDB strong position, the target gear stage tgtG is set as a lower gear ratio side than the gear stage selected at the SDB weak position as the downshift brake while performing the compression release type engine brake having the same strong effect. Perform a downshift.
As described above, the operation state of the auxiliary brake is switched according to the switching position of the auxiliary brake changeover switch 29, and accordingly, the engine brake action is in the OFF position, the PT weak position, the PT strong position, the SDB weak position, or the SDB strong position. In order. Therefore, the driver can generate the engine brake with the desired strength at the time of the accelerator-off operation only by switching the auxiliary brake changeover switch 29 to an arbitrary position in advance, and the braking force is insufficient only with this engine brake. Only operate the service brake.

For example, in addition to switching the auxiliary brake changeover switch 29 according to the driver's own preference for the strength of the engine brake, the driver assists in consideration of the level of ups and downs of the road to be driven or the congestion of the road. The switching position of the brake switch 29 is determined. For example, if road undulations are strong, a stronger engine braking action on downhill roads will reduce the service brake burden and reduce the frequency of service brake operations and reduce driver fatigue. . Further, if the road is congested, it is preferable to generate a stronger engine brake in order to maintain the distance from the preceding vehicle in terms of service brake burden and driver fatigue.
In the present embodiment, the shift down brake can be switched between the strong and weak two stages, and the target gear stage tgtG is set on the lower gear ratio side in the SDB strong position compared to the SDB weak position, and the downshift is executed. , Increasing the effectiveness of downshift braking (ie engine braking). Therefore, as compared with the technique of Patent Document 1 in which the gear is uniquely shifted down by one stage, a more appropriate engine braking action can be generated. Therefore, the above-described service brake burden and driver fatigue can be further reduced. Benefits can be gained.

In addition, first, the compression release type engine brake is operated, and then the shift down brake is operated only when the engine brake is insufficient even when the compression release type engine brake corresponding to the strong position is effective. Compared to the compression release type engine brake, the shift down brake can obtain a strong engine braking action even at a low vehicle speed, but has a drawback that a slight shift shock is caused during the downshift.
However, in situations where a relatively weak engine brake is required, a compression shock does not occur because the compression release type engine brake is used. In a situation where a stronger engine brake is required, a rapid increase in the deceleration G generated by the engine brake Since it becomes difficult for the occupant to feel the shift shock, it is possible to minimize the disadvantages of the shift shock that the downshift brake has.

As described above, the compression release type engine brake and the downshift brake are operated as the auxiliary brakes according to the operation of the auxiliary brake changeover switch 29. In the present embodiment, the process for calculating the target gear stage tgtG of the downshift brakes. In the following, the calculation process of the target gear stage tgtG will be described in detail.
In the calculation process of the target gear stage tgtG of the present embodiment, the optimum target braking force to be generated by the downshift brake is determined according to the vehicle speed, and the target gear stage tgtG is calculated as a gear stage that can achieve the target braking force. This is based on the knowledge that an appropriate engine braking action can be obtained as a result.

FIG. 2 is a control block diagram showing the processing of the ECU 21 for calculating the target gear stage tgtG. As described above, in the present embodiment, the switching position of the auxiliary brake selector switch 29 (hereinafter simply referred to as switch switching position). Since the effect of the downshift brake is switched according to the vehicle speed V, the switch switching position is input as information together with the vehicle speed V.
The switch switching position is 3 positions, that is, the OFF position for stopping the shift down brake, the PT weak position and the PT strong position, the SDB weak position for operating the shift down brake with a weak effect, and the SDB strong for operating the shift down brake with a strong effect. It is classified into positions, and the information is input to the target braking force calculation unit 31 together with the vehicle speed V as information.

In the target braking force calculation unit 31, the target braking force tgtB is set to 0 when the switch switching position is any one of the OFF position, the PT weak position, and the PT strong position. On the other hand, when the switch switching position is the SDB weak position or the SDB strong position, the target braking force tgtB is calculated from the vehicle speed V based on a map in which the relationship between the vehicle speed V and the target braking force tgtB is set in advance.
The map is prepared for each switch switching position, and the characteristic is set so that a larger target braking force tgtB is calculated at the same vehicle speed V in the map in the SDB strong position compared to the map in the SDB weak position. For example, when the switch switching position is the strong SDB position and the vehicle speed V is 80 km / h, 10000 N is calculated as the target braking force tgtB.

The target braking force tgtB calculated in this way is input to the target gear stage calculation unit 32 together with the vehicle speed V, and the target gear stage calculation unit 32 is a gear for achieving the target braking force tgtB on the assumption of the current vehicle speed V. The step is calculated as the target gear step tgtG.
The calculation process is performed in consideration of engine characteristics. That is, the engine rotational speed Ne at the gear stage after the downshift is known from the current vehicle speed V, while the engine 1 at the time of the accelerator off operation stops the fuel injection. The torque generated by 1 (in this case, a negative torque) can also be specified. Therefore, it can also be determined whether or not the target braking force tgtB can be achieved at each gear stage based on the engine torque when the gear is shifted down to each gear stage.

In the actual processing of the target gear stage calculation unit, a map in which the relationship between the target braking force tgtB and the vehicle speed V and the target gear stage tgtG is prepared in advance and the target gear stage is calculated from the target braking force tgtB and the vehicle speed V based on the map. tgtG is calculated. As the target braking force tgtB is higher, a shift down to the lower gear ratio side is required. As a result, the target gear stage tgtG is set to the lower gear ratio side at the SDB strong position compared to the SDB weak position, and the shift is performed. Downbrake is executed. Of course, when the target braking force tgtB is set to 0, the execution of the downshift brake is prohibited by setting the current gear stage as the target gear stage tgtG.
In the map for setting the target gear stage tgtG, the upper limit value of the engine speed Ne is taken into account, and when the engine speed exceeds the upper limit value after the downshift, the gear stage on the first gear ratio side is the target gear stage. Calculated as tgtG. As a result, over-rotation of the engine 1 is prevented in advance, and the shift-down brake can be started in a state where an appropriate engine rotation range is always maintained.

Based on the target gear stage tgtG set in this way, the ECU 21 performs a shift operation of the transmission 3 and a connection / disconnection operation of the clutch device, whereby the transmission 3 is shifted down from the current gear stage to the target gear stage tgtG. Thus, an engine brake corresponding to the target braking force tgtB is generated. Although the braking force generated by the downshift brake has been described above, the compression release engine brake is also operated in parallel at the SDB weak position and the SDB strong position. It will affect the vehicle.
In the present embodiment, a series of processes of the ECU 21 for calculating the target gear stage tgtG described with reference to FIG. 2 functions as the shift control means of the present invention.

  As is apparent from the above description, in the present embodiment, the target braking force tgtB to be actually generated based on the current switch switching position and the vehicle speed V is specifically calculated, and the gear stage that can achieve the target braking force tgtB. Is set as the target gear stage tgtG, and the downshift braking is executed. Therefore, it is possible to generate an engine brake that is extremely close to the target braking force tgtB after the downshift, that is, an engine brake that is optimal for the current situation, and further reduce the service brake burden and reduce the driver's fatigue. Can be increased.

On the other hand, due to the engine braking action of the downshift brake executed in this way, the vehicle speed V should gradually decrease in a normal traveling state, but the vehicle speed V may increase on the downhill road, for example. In this case, there is a possibility that the engine speed Ne exceeds the upper limit value.
Therefore, in this embodiment, the engine speed Ne is always monitored during execution of the downshift brake, and when the upper limit value is exceeded, the target gear stage tgtG is set to one stage so that the engine speed Ne can be limited to the upper limit value. Correction is made to the high gear ratio side, and the gear is shifted up based on the corrected target gear stage tgtG. Therefore, over-rotation of the engine 1 is prevented in advance even during execution of the downshift brake, and the downshift brake can be continued in a state where an appropriate engine rotation range is always maintained.

By the way, when the downshift brake is executed, there is a possibility that the driving feeling may be impaired like the above-described shift shock. Therefore, in this embodiment, in order to suppress such an adverse effect as much as possible, The following points are taken into account when setting the gear stage tgtG.
1) Since shift shocks and engine brakes become prominent in the low vehicle speed range, for example, when the vehicle speed is lower than a predetermined vehicle speed, the running feeling is given priority and the execution of downshift braking is prohibited. Specifically, the current gear stage is maintained by setting 0 as the target braking force tgtB.
2) Since the engine brake tends to be excessive at low gears, aggressive downshifts are suppressed, and common use with downshift timing when the downshift brake is stopped (OFF position, PT weak position, and PT strong position). Plan.
3) Suppresses control interference and shift hunting during suspension / execution of downshift braking.
4) Suppresses excessive engine brake change at the time of switching between the SDB weak position and the SDB strong position.
5) Suppresses shifting hunting when the vehicle speed V increases during execution of downshift braking.

By taking these measures, it is possible to prevent the deterioration of the running feeling due to the execution of the downshift brake.
This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above embodiment, the transmission 3 is used in which the shifting operation and the connecting / disconnecting operation of the clutch device 2 associated with the shifting are automated based on the manual transmission, but the type of the transmission 3 is not limited thereto. . For example, the present invention may be applied to a so-called dual clutch transmission.
The dual clutch transmission is configured by connecting gear mechanisms divided into odd and even gears to the engine side via clutches, and when the power is transmitted by connecting the clutch of one gear mechanism. The clutch of the other gear mechanism is disengaged and switched to the next predicted gear stage in advance, and when the shift timing comes, the connected state of both clutches is reversed and power transmission by the other gear mechanism is started. is there. Even in such a dual clutch transmission, the gear stage can be arbitrarily switched, so that the downshift braking described in the embodiment can be performed.

Further, the present invention may be applied to an automatic transmission in which a planetary gear mechanism is combined with a torque converter, or may be applied to a continuously variable transmission such as a belt type. In particular, a continuously variable transmission that can control the gear ratio steplessly can achieve a gear ratio that completely matches the target braking force tgtB obtained from the switch switching position and the vehicle speed V. The action can be realized.
In the above embodiment, the target braking force tgtB is calculated by the target braking force calculation unit 31 from the switch switching position and the vehicle speed V, and the target gear step calculation unit 32 calculates the target gear step tgtG using the target braking force tgtB. However, the target braking force calculation unit 31 and the target gear stage calculation unit 32 may be integrated in order to reduce the calculation load of the ECU 21. Specifically, after clarifying the relationship between the target braking force tgtB and the target gear stage tgtG by a prior test, a map for directly calculating the target gear stage tgtG from the switch switching position and the vehicle speed V is set. From this, the target gear stage tgtG may be obtained.

  Moreover, in the said embodiment, although the function of the compression release type engine brake was added to the engine 1, you may abbreviate | omit the function of the said compression release type engine brake. In this case, the PT weak position and the PT strong position of the auxiliary brake changeover switch 29 are omitted, and the control procedure described in the above embodiment according to the switching between the OFF position, the SDB weak position, and the SDB strong position. The shift down brake may be operated according to the above.

3 Transmission 21 ECU (shift control means)
29 Auxiliary brake switch (switch)

Claims (6)

While shifting the transmission to achieve the target gear ratio obtained from the driver's accelerator operation amount and vehicle speed, the target gear ratio is set to a lower gear ratio side than the current gear ratio when the driver turns off the accelerator. In a vehicle transmission control apparatus that performs a downshift for setting and downshifting the transmission,
A change-over switch provided in the driver's seat, which can be switched to a stop position for stopping the downshift brake, a weak position for operating the downshift brake with a weak effect, and a strong position for operating the downshift brake with a strong effect; ,
When the changeover switch is switched to the stop position, the downshift brake is stopped. When the changeover switch is switched to the weak position and the strong position, the shift down brake is operated. A vehicle shift control device comprising: a shift control means for shifting down by setting the target gear ratio to a lower gear ratio side. When the changeover switch is switched to a weak position or a strong position, the shift control means has a higher braking force than the vehicle speed at the strong position compared to the weak position according to a preset relationship between the vehicle speed and the braking force of the host vehicle. The shift control apparatus for a vehicle according to claim 1, wherein a shift ratio is reduced by setting a gear ratio capable of achieving the calculated target braking force as the target gear ratio.   When the gear shift control means shifts down based on the set target gear ratio and the engine speed exceeds the upper limit value, the target gear ratio is set to the high gear ratio side so that the engine speed can be limited to the upper limit value. 3. The vehicle shift control device according to claim 1, wherein the shift control device corrects and shifts down based on the corrected target gear ratio.   The shift control means can limit the engine speed to the upper limit value when the engine speed exceeds the upper limit value as the vehicle speed increases due to the downhill road after the downshift based on the target gear ratio. 4. The vehicle transmission control apparatus according to claim 1, wherein the target gear ratio is corrected to a high gear ratio side, and the gear ratio is controlled based on the corrected target gear ratio. The changeover switch includes an auxiliary brake position for operating an auxiliary brake mounted on the vehicle in addition to the stop position, the weak position, and the strong position.
The shift control means operates only the auxiliary brake when the changeover switch is switched to the auxiliary brake position, and operates the auxiliary brake together with the shift-down brake when the changeover switch is switched to the weak position and the strong position. 5. The transmission control apparatus for a vehicle according to claim 1, wherein the target gear ratio is set to a lower gear ratio side in a strong position compared to a weak position. 6. The vehicle shift control device according to claim 1, wherein the shift control means prohibits execution of the downshift brake at a speed lower than a predetermined vehicle speed.

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