JP4966589B2 - Driving force distribution device - Google Patents

Description

  The present invention relates to a driving force distribution device.

  2. Description of the Related Art Conventionally, there has been a driving force distribution device that can vary the driving force distribution between a main driving wheel (usually, the front wheel in the case of a front wheel driving vehicle base) and an auxiliary driving wheel by a torque coupling provided with an electromagnetic clutch. For example, in the driving force distribution device described in Patent Document 1, a plurality of driving force distribution characteristics are defined by a map set that uses vehicle speed and throttle opening or front and rear wheel speed differences as parameters, and switches the map to be referred to. Thus, the driving force distribution characteristic is changed. Some of such driving force distribution devices perform appropriate driving force distribution according to the road surface state by estimating the state of the traveling road surface.

  By the way, the estimation of the road surface condition is generally performed using vehicle state quantities such as the yaw rate and the longitudinal acceleration (front and rear G). Further, in the driving force distribution device described in Patent Document 1, the road surface state is estimated by predicting the weather based on the change in atmospheric pressure detected by the atmospheric pressure sensor. However, many vehicles are not equipped with sensors for detecting such special vehicle state quantities. For this reason, an increase in cost due to the adoption of such a sensor is inevitable, and there is a problem that it is necessary to optimize the relationship between the vehicle state quantity and the road surface state as appropriate according to the specifications of the vehicle.

Therefore, conventionally, when the outside air temperature of a vehicle is detected and the outside air temperature is lower than a predetermined temperature, a low temperature that distributes more driving force to the auxiliary driving wheel side than the driving force distribution characteristic at normal temperature. Some switch to a mode (see, for example, Patent Document 2). That is, the driving tendency is a two-wheel drive tendency when the traveling road is a high μ road at a normal temperature and the driving tendency is a four-wheel driving tendency when the driving road is a low μ road and the probability is high. As a result, good vehicle stability can be ensured without increasing the number of sensors.
JP 2003-31288 A JP-A-11-59216

  However, in many cases, the outside air temperature sensor is disposed in the engine room of the vehicle, and thus is easily affected by exhaust heat of the engine. For this reason, the conventional configuration described above may not be able to accurately determine the outside air temperature when the engine exhaust heat is likely to stay in the engine room, for example, and in such a case, drive force distribution should be performed appropriately. You may not be able to.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a driving force distribution device that can perform more appropriate driving force distribution according to the road surface state without increasing the number of sensors. Is to provide.

In order to solve the above problems, the invention according to claim 1 controls the torque coupling capable of varying the driving force distribution between the main driving wheel and the auxiliary driving wheel, and the operation of the torque coupling. Drive means having a low-temperature mode for controlling the operation of the torque coupling so as to distribute more driving force to the auxiliary driving wheel side than the driving force distribution characteristic at normal temperature. The power distribution device, comprising: an outside air temperature detecting unit that detects an outside air temperature of a vehicle set in an engine room that is affected by heat generated by the engine; and a vehicle speed detecting unit that detects a vehicle speed , the control The means sets the low temperature mode when the outside air temperature is continuously lower than a predetermined temperature for a predetermined time, and the state where the outside air temperature is the predetermined temperature or higher and the vehicle speed is higher than the predetermined speed is a second predetermined time. Less than If you continue, it is a temperature mode corresponding to the time of the normal temperature, and the gist.

  That is, when the detected outside air temperature is continuously low for a predetermined time or longer, the outside air temperature is not easily affected by engine exhaust heat (during driving or immediately after engine start), or the exhaust air temperature does not become a problem. It can be estimated that the state is low. Therefore, according to the above configuration, it is possible to accurately determine that the temperature is low, without causing an increase in sensors and eliminating the influence of exhaust heat of the engine. Thereby, it is possible to more appropriately switch to the “low temperature mode” suitable for the low μ road, and as a result, it is possible to realize more appropriate driving force distribution according to the road surface condition.

Further , when the vehicle travels at a speed higher than a constant speed (predetermined speed) and the state in which the outside air is sufficiently introduced into the engine room continues (second predetermined time), the temperature in the engine room is increased. Becomes a value close to the outside air temperature, thereby reducing the influence of the exhaust heat of the engine.

  Therefore, according to the above configuration, it is possible to determine whether or not the temperature is normal temperature only when the engine is not easily affected by the exhaust heat of the engine. It is possible to prevent erroneous determination as being at room temperature, and to more appropriately switch to the “room temperature mode” that is suitable for the room temperature with high probability that is a high μ road. As a result, more appropriate driving force distribution according to the road surface condition can be realized without adding a new sensor, and good vehicle stability can be ensured.

The invention according to claim 2 comprises a torque coupling capable of varying the driving force distribution between the main drive wheel and the auxiliary drive wheel, and a control means for controlling the operation of the torque coupling, the control means. Is a driving force distribution device having a low temperature mode for controlling the operation of the torque coupling so as to distribute more driving force to the auxiliary driving wheel side compared to the driving force distribution characteristic at normal temperature, An engine intake air temperature detecting means for detecting an engine intake air temperature provided in the intake pipe, wherein the control means is set to the low temperature mode when the engine intake air temperature is continuously lower than a predetermined temperature for a predetermined time, Is the gist.

  That is, it is conceivable to use an engine intake air temperature sensor as an outside air temperature sensor. However, since the engine intake temperature sensor is provided in the engine intake pipe, the engine intake temperature sensor is more susceptible to the exhaust heat of the engine. If the low temperature determination threshold is usually set to a low value in consideration of fuel efficiency, the low temperature determination is possible when the engine intake air temperature sensor is simply used instead of the outside air temperature sensor. Such a situation is practically limited to a complete cold start when the engine is completely cold, or extremely cold.

  In this regard, if the determination condition is that the temperature is continuously lower than the predetermined temperature for a predetermined time or longer, the determination threshold value (predetermined temperature) can be set to a value that considers the influence of exhaust heat of the engine to some extent. The situation in which it can be determined that the temperature is low can be expanded. In other words, the exhaust heat of the engine may stay in the engine intake pipe before the engine starts, but after the engine starts, the outside air is introduced into the engine intake pipe, so the outside air temperature can be adjusted relatively accurately. Can be detected. That is, after the engine is started and before the engine temperature rises again, if it can be detected that the engine intake air temperature is lower than the predetermined temperature for a predetermined time, it can be determined that the outside air temperature is low.

  Therefore, according to the above-described configuration, it is possible to accurately determine that the temperature is low without adding a new sensor, and thereby, a “low temperature mode” that is suitable for low temperatures, which is a low μ path, and has a high probability. Can be switched more appropriately. As a result, it is possible to achieve more appropriate driving force distribution according to the road surface condition and ensure good vehicle stability. In addition, by using the engine intake air temperature sensor as an outside air temperature sensor, it can be applied to a vehicle that does not have an outside air temperature sensor, such as a vehicle that is not equipped with an air conditioner.

The invention according to claim 3 is provided with vehicle speed detecting means for detecting a vehicle speed, and the control means has a state in which the engine intake air temperature is equal to or higher than the predetermined temperature and the vehicle speed is higher than the predetermined speed for a second predetermined time or more. When it continues, it makes it a summary to set it as the normal temperature mode corresponding to the said normal temperature time.

  According to the above configuration, as in the configuration of the second aspect, it is possible to determine whether or not the temperature is normal temperature only when the engine is not easily affected by exhaust heat from the engine. This prevents incorrect judgment that the ambient temperature is low even though the outside air temperature is low, and makes it possible to more appropriately switch to the “normal temperature mode” that is suitable for normal temperatures that are high μ roads. it can.

The gist of the invention described in claim 4 is that the control means fixes the driving force distribution characteristic to the low temperature mode after changing to the low temperature mode.
According to the above configuration, it is possible to prevent a normal temperature mode from being erroneously determined even when the temperature is low, and to maintain good vehicle stability while maintaining a more stable 4WD trend. Can do.

The gist of the invention described in claim 5 is that the control means changes the driving force distribution characteristic when the vehicle speed is equal to or lower than a second predetermined speed.
That is, in the high vehicle speed region, the influence of the change in the driving force distribution upon the mode transition on the vehicle behavior is large. Therefore, according to the said structure, the destabilization of the vehicle behavior accompanying the change of the driving force distribution at the time of mode transition can be suppressed.

The invention according to claim 6 comprises a torque coupling capable of varying the driving force distribution between the main drive wheel and the auxiliary drive wheel, and a control means for controlling the operation of the torque coupling, the control means. Is a driving force distribution device having a low temperature mode for controlling the operation of the torque coupling so as to distribute more driving force to the auxiliary driving wheel side compared to the driving force distribution characteristic at normal temperature, An outside air temperature detecting means for detecting the outside air temperature of the vehicle set in the engine room , which is a part affected by the generated heat, and a cooling water temperature detecting means for detecting the cooling water temperature of the engine, and the control means includes: At the time of start-up, when the temperature difference between the outside air temperature and the cooling water temperature is smaller than a predetermined value and at least one of the outside air temperature or the cooling water temperature is lower than the predetermined temperature, the low temperature mode is set. It is de, and the gist.

  That is, if the engine coolant temperature is close to the outside air temperature, that is, if the engine is sufficiently cooled, the influence of engine exhaust heat is slight. Therefore, according to the above-described configuration, it is possible to accurately determine that the temperature is low without adding a new sensor, and thereby, a “low temperature mode” that is suitable for low temperatures, which is a low μ path, and has a high probability. Can be switched more appropriately. As a result, it is possible to achieve more appropriate driving force distribution according to the road surface condition and ensure good vehicle stability.

According to a seventh aspect of the present invention, the control means is a normal temperature mode corresponding to the normal temperature when the temperature difference is smaller than the predetermined value and the outside air temperature and the cooling water temperature are equal to or higher than the predetermined temperature. This is the gist.

  According to the above configuration, for the same reason as in the second and fourth aspects, it is possible to accurately determine that the room temperature is normal without adding a new sensor. It is possible to more appropriately switch to the “normal temperature mode” that is suitable at high normal temperatures. As a result, it is possible to achieve more appropriate driving force distribution according to the road surface condition and ensure good vehicle stability.

The invention according to claim 8 includes a torque coupling capable of varying the driving force distribution between the main drive wheel and the auxiliary drive wheel, and a control means for controlling the operation of the torque coupling, the control means. Is a driving force distribution device having a low temperature mode for controlling the operation of the torque coupling so as to distribute more driving force to the auxiliary driving wheel side compared to the driving force distribution characteristic at normal temperature, An engine intake air temperature detecting means for detecting an engine intake air temperature provided in an intake pipe; and a cooling water temperature detecting means for detecting a cooling water temperature of the engine, wherein the control means is configured to detect the engine intake air temperature when the engine is started. The low temperature mode is set when the temperature difference from the cooling water temperature is smaller than a predetermined value and at least one of the engine intake air temperature or the cooling water temperature is lower than the predetermined temperature. The the gist.

  That is, the engine intake air temperature sensor is provided in the engine intake pipe that is more susceptible to the exhaust heat of the engine. For this reason, the engine intake air temperature does not necessarily coincide with the outside air temperature. However, when the temperature difference between the engine intake air temperature and the engine cooling water temperature is smaller than a predetermined value and at least one of the engine intake air temperature and the engine cooling water temperature is lower than the predetermined temperature, the engine temperature is also low as with the outside air temperature. It can be estimated that.

  Therefore, according to the above-described configuration, it is possible to accurately determine that the temperature is low without adding a new sensor, and thereby, a “low temperature mode” that is suitable for low temperatures, which is a low μ path, and has a high probability. Can be switched more appropriately. As a result, it is possible to achieve more appropriate driving force distribution according to the road surface condition and ensure good vehicle stability.

According to a ninth aspect of the present invention, when the temperature difference is smaller than the predetermined value and the engine intake air temperature and the cooling water temperature are equal to or higher than the predetermined temperature, the control unit is configured to perform a normal temperature corresponding to the normal temperature. The gist is to set the mode.

  According to the above configuration, for the same reason as in the second, fourth, and eighth aspects, it is possible to accurately determine that the temperature is normal temperature without adding a new sensor. It is possible to more appropriately switch to “room temperature mode” that is suitable at room temperature with a high probability. As a result, it is possible to achieve more appropriate driving force distribution according to the road surface condition and ensure good vehicle stability.

According to a tenth aspect of the present invention, the control means stores a mode of the driving force distribution characteristic when the engine is stopped, and the stored mode is stored when the temperature difference is not less than the predetermined value. This is the gist.

  According to the above configuration, when it is impossible to accurately determine whether the temperature is low due to the influence of exhaust heat from the engine, such as when the engine is restarted within a short time after the engine is stopped, Prevents switching to “room temperature mode” in spite of the occasion, and if it was “low temperature mode” at the time of the previous engine stop, maintains a more stable 4WD trend and good vehicle stability Can be secured.

  ADVANTAGE OF THE INVENTION According to this invention, the driving force distribution apparatus which can perform more suitable driving force distribution according to a road surface state can be provided, without causing the increase in a sensor.

(First embodiment)
Hereinafter, a first embodiment in which the present invention is embodied in a driving force distribution device for a four-wheel drive vehicle will be described with reference to the drawings.

  As shown in FIG. 1, the vehicle 1 is a four-wheel drive vehicle based on a front wheel drive vehicle, and a pair of front axles 4 are connected to a transaxle 3 assembled on one side of the engine 2. Further, a propeller shaft 5 is connected to the transaxle 3 together with the front axles 4, and the propeller shaft 5 is connected to a pair of rear axles 8 via a rear differential 7. The driving force of the engine 2 is transmitted to the front wheels 6f through these front axles 4, and is also transmitted to the rear wheels 6r through the propeller shafts 5 and the respective rear axles 8.

  Further, the vehicle 1 of the present embodiment includes a torque coupling 9 that can vary the driving force distribution between the front wheels 6f that are the main driving wheels and the rear wheels 6r that are the auxiliary driving wheels, and a control unit that controls the operation thereof. And a driving force distribution device 11 including the ECU 10.

  In the present embodiment, the torque coupling 9 is interposed between the propeller shaft 5 and the rear differential 7. The torque coupling 9 includes an electromagnetic clutch 12 whose frictional engagement force changes according to the amount of current supplied to the electromagnetic coil, and a driving force based on the frictional engagement force is transferred from the propeller shaft 5 to the rear differential 7. Configured to communicate. The ECU 10 controls the operation of the torque coupling 9 through current supply to the electromagnetic clutch 12, thereby controlling the driving force distribution between the front wheels 6f that are the main driving wheels and the rear wheels 6r that are the auxiliary driving wheels. .

  Specifically, the throttle opening sensor 13 and the wheel speed sensors 14a to 14d are connected to the ECU 10 of the present embodiment, and the ECU 10 determines the throttle opening Ra, the vehicle speed V, the vehicle speed V based on the output signals of these sensors. And the wheel speed difference Wth between the front wheel 6f and the rear wheel 6r is detected. That is, in this embodiment, each wheel speed sensor 14a-14d comprises a vehicle speed detection means. The ECU 10 controls the driving force distribution based on the vehicle speed V, the throttle opening Ra, and the wheel speed difference Wth. Specifically, the ECU 10 according to the present embodiment includes a map set 16a including a feed forward map using the vehicle speed V and the throttle opening Ra as parameters, and a feedback map using the wheel speed difference Wth as parameters. Then, the ECU 10 compares the detected vehicle speed V, throttle opening Ra, and wheel speed difference Wth with the map set 16a so as to respond to the vehicle speed V, throttle opening Ra, and wheel speed difference Wth. The driving force distribution ratio to the wheel 6r is determined. That is, in this embodiment, the driving force distribution characteristic of the driving force distribution device 11 is defined by the map set 16a. Then, the ECU 10 supplies a current to the electromagnetic clutch 12 so as to generate a frictional engagement force according to the determined driving force distribution ratio, whereby the operation of the torque coupling 9, that is, the front wheel 6f which is the main driving wheel, Control of driving force distribution with respect to the rear wheel 6r which is the auxiliary driving wheel is controlled.

(Driving force distribution characteristics variable control)
Next, variable control of the driving force distribution characteristic in the driving force distribution device of the present embodiment will be described.

  As shown in FIG. 1, in the present embodiment, an engine intake air temperature sensor 15 as an engine intake air temperature detecting means provided in an engine intake pipe (not shown) is connected to the ECU 10. The ECU 10 then distributes the driving force between the front wheels 6f as the main driving wheels and the rear wheels 6r as the auxiliary driving wheels based on the engine intake air temperature Tmp detected by the engine intake air temperature sensor 15 and the vehicle speed V. (Driving force distribution characteristic variable control).

  More specifically, in the present embodiment, the ECU 10 has a plurality of modes that define the driving force distribution characteristics, more specifically, the “normal temperature mode” corresponding to the case where the engine intake air temperature Tmp is in the normal temperature range, and the road surface is a low μ road. There are three modes: a “low-temperature mode” corresponding to an easy low temperature, and a “temporary mode” corresponding to immediately after the engine is started. The ECU 10 changes the driving force distribution characteristics by switching these modes based on the engine intake air temperature Tmp and the vehicle speed V.

  Specifically, the ECU 10 according to the present embodiment, in addition to the above-described map set 16a corresponding to the “normal temperature mode”, is compared with the driving force distribution characteristic in the map set 16a by the rear wheel 6r side which is the auxiliary driving wheel. A second map set 16b set to distribute a large amount of driving force is provided. Then, in the “low temperature mode”, the ECU 10 determines a driving force distribution ratio by using this second map set, thereby distributing a larger amount of driving force to the rear wheel 6r side. Good vehicle stability is ensured even at low temperatures that tend to occur. In the present embodiment, the driving force distribution ratio is determined using the second map set 16b even in the “provisional mode”, and the driving force distribution characteristic at the start of the engine is “low temperature mode”. As in the case of FIG. 2, a large amount of driving force is distributed to the rear wheel 6r side which is the auxiliary driving wheel.

  More specifically, as shown in the flowchart of FIG. 2, when the ECU 10 acquires the engine intake temperature Tmp and the vehicle speed V as sensor values (step 101), the ECU 10 subsequently shifts based on the engine intake temperature Tmp and the vehicle speed V. The power mode determination, that is, the mode transition determination is executed (step 102). Then, it is determined whether or not there is a mode transition (step 103). If it is determined that the mode transition is to be performed (step 103: YES), the transition processing to the mode is executed (step 104). As will be described later, in the present embodiment, when each mode is changed, it is not performed at the same time as the determination thereof. Therefore, hereinafter, the term “migration” will be used for convenience.

[Mode transition judgment]
Next, modes of mode transition determination by the ECU of this embodiment will be described.
In the present embodiment, the ECU 10 sets the mode to be shifted to the “low temperature mode” when the engine intake temperature Tmp is continuously lower than the predetermined temperature T0 for the predetermined time t1 in the mode shift determination. The mode to be shifted to when the engine intake temperature Tmp is equal to or higher than the predetermined temperature T0 and the vehicle speed V is higher than the predetermined speed V1 continues for the predetermined time t2 or longer is referred to as “normal temperature mode”. For example, the predetermined time t1 may be set to 10 seconds, and the predetermined time t2 may be set to about 60 seconds. The predetermined temperature T0 is a temperature at which the road surface may be frozen or there is residual snow, specifically 5 It is desirable that the temperature is not higher than ° C.

  Specifically, as shown in the flowchart of FIG. 3, the ECU 10 first determines whether or not the detected engine intake air temperature Tmp is lower than a predetermined temperature T0 (step 201). When the engine intake air temperature Tmp is lower than the predetermined temperature T0 (Tmp <T0, Step 201: YES), it is determined whether or not the low temperature mode is set (low temperature determination) (Step 202 to Step 211). When the engine intake air temperature Tmp is equal to or higher than the predetermined temperature T0 (Tmp ≧ T0, Step 201: NO), it is determined whether or not to enter the room temperature mode (room temperature determination) (Steps 212 to 224). When it is determined that the engine intake air temperature Tmp is continuously lower than the predetermined temperature T0 for the predetermined time t1 or more, the mode determination value Val_md indicating the transition mode is set to “1” corresponding to the “low temperature mode”, and the engine intake temperature is determined. If it is determined that the temperature Tmp is equal to or higher than the predetermined temperature T0 and the vehicle speed V is higher than the predetermined speed V1, the mode determination value Val_md is “2” corresponding to the “normal temperature mode”. . In this embodiment, since the “provisional mode” corresponding to the engine start is set, the initial value of the mode determination value Val_md is “0” corresponding thereto.

  More specifically, when the ECU 10 determines in step 201 that the engine intake air temperature Tmp is lower than the predetermined temperature T0 (Tmp <T0, step 201: YES), first, the mode determination value Val_md is “1”. Whether it is already in the “low temperature mode” (step 202). If the mode determination value Val_md is not “1” (step 202: NO), it is subsequently determined whether or not the room temperature is being determined (step 203), and if it is determined that the room temperature is being determined (step 203). 203: YES), a normal temperature determination flag indicating that the normal temperature determination is being performed is reset (step 204).

  When it is determined in step 202 that the mode determination value Val_md is “1”, that is, already in the “low temperature mode” (step 202: YES), the ECU 10 performs the processing from step 203 to step 211. Do not execute. If it is determined in step 203 that the room temperature is not being determined (step 203: NO), the process of step 205 shown below is executed without executing the process of step 204.

  Next, the ECU 10 determines whether or not the low temperature determination is already being performed (step 205). If it is determined that the low temperature determination is not being performed (step 205: NO), a low temperature determination flag indicating that the low temperature determination is being performed is set (step 206), and the timer for measuring the elapsed time t is reset. (T = 0, step 207). If it is determined in step 205 that the low temperature determination has already been made (step 205: YES), the ECU 10 does not execute the processes in steps 206 and 207, but performs the process in step 208 shown below. Execute.

  Next, the ECU 10 increments the timer (step 208) and determines whether or not the elapsed time t is equal to or greater than the predetermined time t1 (step 209). When the elapsed time t is equal to or longer than the predetermined time t1 (t ≧ t1, step 209: YES), the low temperature determination flag is reset (step 210), and the mode determination value Val_md is set to “1” (Val_md = 1, step 211). In step 209, when the elapsed time t is less than the predetermined time t1 (t <t1, step 209: NO), the ECU 10 does not execute the processing of steps 210 and 211.

  On the other hand, when the engine intake temperature Tmp is equal to or higher than the predetermined temperature T0 in step 201 (Tmp ≧ T0, step 201: NO), the ECU 10 first determines whether or not the low temperature determination is being performed (step 212). If it is determined that the determination is being made (step 212: YES), the low temperature determination flag indicating that the low temperature determination is being performed is reset (step 213). If the low temperature determination is not in progress (step 212: NO), the ECU 10 executes the process of step 214 shown below without executing the process of step 213.

  Next, the ECU 10 determines whether or not the vehicle speed V is higher than the predetermined speed V1 (step 214). If the vehicle speed V is higher than the predetermined speed V1 (V> V1, step 214: YES), the ECU 10 continues. Then, it is determined whether or not the mode determination value Val_md is “2”, that is, whether or not it is already in “room temperature mode” (step 215).

  When it is determined in step 214 that the vehicle speed V is equal to or lower than the predetermined speed V1 (V ≦ V1, step 214: NO), the ECU 10 determines whether or not the room temperature is being determined (step 216). If the normal temperature determination is being performed (step 216: YES), the normal temperature determination flag is reset (step 217), and the processing after step 215 and step 218 shown below is not executed, and the normal temperature determination is being performed. If not (step 216: NO), the processing from step 215 and step 217 onward is not executed.

  Next, when it is determined in step 215 that the mode determination value Val_md is not “2” (step 215: NO), the ECU 10 subsequently determines whether or not the room temperature determination is being performed (step 218). . If it is determined that the room temperature is not being determined (step 218: NO), a room temperature determination flag indicating that the room temperature is being determined is set (step 219), and the timer for measuring the elapsed time t is reset. (T = 0, step 220).

  When it is determined in step 215 that the mode determination value Val_md is “2”, that is, already in the “normal temperature mode” (step 215: YES), the ECU 10 does not execute the processing after step 218. . If it is determined in step 218 that the room temperature has already been determined (step 218: YES), the ECU 10 does not execute the processes in steps 219 and 220 but performs the process in step 221 shown below. Execute.

  Next, the ECU 10 increments the timer (step 221), and determines whether or not the elapsed time t is equal to or longer than the predetermined time t2 (step 222). When the elapsed time t is equal to or longer than the predetermined time t2 (t ≧ t2, step 222: YES), the normal temperature determination flag is reset (step 223), and the mode determination value Val_md is set to “2” (Val_md = 2, step 224). In step 222, when the elapsed time t is less than the predetermined time t2 (t <t2, step 222: NO), the ECU 10 does not execute the processes of steps 223 and 224.

  As described above, the ECU 10 performs the mode transition determination by sequentially executing the processing of step 201 to step 224 for each scheduled interruption. Thus, when the engine intake air temperature Tmp is continuously lower than the predetermined temperature T0 for the predetermined time t1, the mode to be shifted to is “low temperature mode”, and the engine intake air temperature Tmp is the predetermined temperature T0 or higher and the vehicle speed V When the state where the speed is higher than the predetermined speed V1 continues for a predetermined time t2 or longer, the mode to be transferred is determined as the “normal temperature mode”. The predetermined speed V1 may be a vehicle speed at which the exhaust heat of the engine 2 is not accumulated in the part where the engine intake air temperature sensor 15 is disposed, that is, the vehicle speed is such that the outside air is sufficiently introduced into the engine room. Is preferably 10 km / h or more.

[Mode transition processing]
Next, the mode transition process by the ECU of this embodiment will be described.
Now, when the mode for defining the driving force distribution characteristic shifts, the driving force distribution changes even at the same vehicle speed V, accelerator opening, and wheel speed difference Wth. For this reason, the change in the driving force distribution at the time of the mode transition may disturb the vehicle behavior. In general, the influence becomes more remarkable as the vehicle speed V increases.

  In consideration of this point, in the present embodiment, the ECU 10 executes the mode transition when the vehicle speed V is lower than the predetermined speed V2 in the mode transition process. In other words, even when it is determined that the mode transition should be changed (see FIG. 2, step 103: YES), the speed region that is greatly affected by the change in the driving force distribution at the time of the mode transition, that is, the predetermined speed V2 When the vehicle speed V is higher, the mode, that is, the driving force distribution characteristic is not changed. As a result, instability of the vehicle behavior accompanying the mode transition is suppressed.

  Specifically, as shown in FIG. 4, the ECU 10 first determines whether or not the vehicle speed V is equal to or lower than a predetermined speed V2 (step 301). When the vehicle speed V is equal to or lower than the predetermined speed V2 (V ≦ V2, step 301: YES), it is subsequently determined whether or not the mode determination value Val_md is “1” (step 302), and the mode determination is performed. When the value Val_md is “1” (Val_md = 1, step 302: YES), the mode is changed to “low speed mode” (step 303). In step 302, when the mode determination value Val_md is not “1” (step 302: NO), it is determined whether the mode determination value Val_md is “2” (step 304), and the mode determination value Val_md is determined. If it is “2” (Val_md = 2, step 304: YES), the mode is changed to “room temperature mode” (step 305). In step 301, when the vehicle speed V is higher than the predetermined speed V2 (V> V2, step 301: NO), the processing after step 302 is not executed. The predetermined speed V2 is lower than the predetermined speed V1 or the same speed as V1, and specifically, it is preferably 10 km / h or less.

As described above, according to the present embodiment, the following features can be obtained.
(1) The driving force distribution device 11 includes a torque coupling 9 capable of varying the driving force distribution between the front wheel 6f as the main driving wheel and the rear wheel 6r as the auxiliary driving wheel, and a control means for controlling the operation thereof. The ECU 10 has a “low temperature mode” in which more driving force is distributed to the rear wheel 6r side, which is the auxiliary driving wheel, compared to the driving force distribution characteristic at normal temperature. When the engine intake air temperature Tmp is continuously lower than the predetermined temperature T0 for the predetermined time t1 or longer, the ECU 10 sets the mode to be shifted to the “low temperature mode”.

  That is, since the engine intake temperature sensor 15 is provided in the engine intake pipe, the engine intake temperature sensor 15 is more susceptible to the exhaust heat of the engine 2. In consideration of the fact that the low temperature determination threshold value is usually set to a low value in consideration of fuel efficiency, when the engine intake temperature Tmp is simply used as the outside air temperature, the situation where the low temperature determination is possible is In fact, this is limited to a complete cold start when the engine is completely cold, or extremely cold.

  In this regard, as described above, the determination condition is that the engine intake air temperature Tmp continues for a predetermined time t1 or longer and is lower than the predetermined temperature T0, so that the influence of the exhaust heat of the engine 2 is considered to some extent. The value can be set to a value, thereby widening the situation in which it can be determined that the temperature is low. Therefore, it is possible to accurately determine that the temperature is low without adding a new sensor, and this makes it more appropriate to switch to the “low-temperature mode” that is suitable for low-μ roads that have a high probability of low temperature. Can be done. As a result, it is possible to achieve more appropriate driving force distribution according to the road surface condition and ensure good vehicle stability.

  (2) The ECU 10 sets the mode to be shifted to “normal temperature mode” when the engine intake temperature Tmp is equal to or higher than the predetermined temperature T0 and the vehicle speed V is higher than the predetermined speed V1 for a predetermined time t2 or longer.

  That is, when the vehicle travels at a vehicle speed V higher than the predetermined speed V1 and the outside air is sufficiently introduced into the engine room for a predetermined time t2 or more, the temperature in the engine room becomes a value close to the outside air temperature. As a result, the influence of the exhaust heat of the engine 2 is also alleviated.

  Therefore, by configuring as described above, it is possible to determine whether or not the temperature is normal temperature only when the engine 2 is not easily affected by the exhaust heat of the engine 2. Nevertheless, it is possible to prevent erroneous determination that the temperature is normal temperature, and more appropriately switch to the “normal temperature mode” which is a high μ road and is suitable for normal temperature. As a result, more appropriate driving force distribution according to the road surface condition can be realized without adding a new sensor, and good vehicle stability can be ensured.

  (3) When the vehicle speed V is equal to or lower than the predetermined speed V2 in the mode transition process, the ECU 10 executes the mode transition, that is, changes in driving force distribution characteristics. With such a configuration, it is possible to suppress the instability of the vehicle behavior accompanying the change in the driving force distribution at the time of mode transition.

(Second Embodiment)
Hereinafter, a second embodiment in which the present invention is embodied in a driving force distribution device for a four-wheel drive vehicle will be described with reference to the drawings. For convenience of explanation, the same parts as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 5, in the driving force distribution device 20 of the present embodiment, the ECU 22 is connected to a water temperature sensor 23 as a cooling water temperature detecting means for detecting the cooling water temperature Tw of the engine 2. Then, the ECU 22 changes the mode for defining the driving force distribution characteristic based on the coolant temperature Tw and the engine intake air temperature Tmp when the engine 2 is started.

  More specifically, as shown in the flowchart of FIG. 6, the ECU 22 first determines whether or not the engine 2 has just been started (step 401). If it is determined that the engine 2 has just been started (step 401: YES), the engine intake air temperature Tmp and the cooling water temperature Tw are acquired as sensor values (step 402). When it is determined in step 401 that the engine 2 is not immediately after starting (step 401: NO), the ECU 22 does not execute the processing from step 403 onward. That is, in this embodiment, the ECU 22 changes the mode only when the engine is started.

  Next, when the engine intake air temperature Tmp and the coolant temperature Tw are acquired in step 402, the ECU 22 subsequently determines that the temperature difference (| Tmp−Tw |) between the engine intake air temperature Tmp and the coolant temperature Tw is greater than the predetermined value α. It is determined whether it is small (step 403). If the temperature difference (| Tmp−Tw |) is smaller than the predetermined value α (| Tmp−Tw | <α, Step 403: YES), whether or not the engine intake air temperature Tmp is lower than the predetermined temperature β. If the engine intake air temperature Tmp is equal to or higher than the predetermined temperature β (Tmp ≧ β, step 404: NO), then whether or not the cooling water temperature Tw is lower than the predetermined temperature β is determined. Determination is made (step 405). In step 404, the engine intake air temperature Tmp is lower than the predetermined temperature β (Tmp <β, step 404: YES), or in step 405, the cooling water temperature Tw is lower than the predetermined temperature β (Tw <β, step 405). : YES), the mode for defining the driving force distribution characteristic is set to the “low temperature mode” (step 406).

  That is, in the present embodiment, the ECU 22 has a temperature difference (| Tmp−Tw |) between the engine intake air temperature Tmp and the cooling water temperature Tw smaller than the predetermined value α, and the engine intake air temperature Tmp or the cooling water temperature. The “low temperature mode” is set when at least one of Tw is lower than the predetermined temperature β. In step 405, the cooling water temperature Tw is equal to or higher than the predetermined temperature β (Tmp ≧ β, step 405: NO), that is, the temperature difference (| Tmp−Tw |) between the engine intake air temperature Tmp and the cooling water temperature Tw is predetermined. A “normal temperature mode” is set in which the engine intake air temperature Tmp and the coolant temperature Tw are equal to or higher than a predetermined temperature β, which is smaller than the value α (step 407). The predetermined value α is preferably set to about 10 ° C., and the predetermined temperature β is preferably set to a range of 0 to 10 ° C.

  In the present embodiment, the ECU 22 stores a mode (previous mode) at the time of the previous engine stop. In step 403, the temperature difference (| Tmp−Tw |) between the engine intake air temperature Tmp and the coolant temperature Tw. ) Is greater than or equal to the predetermined value α, the process after step 404 is not executed, and the stored previous mode is continued (step 408).

As described above, according to the present embodiment, the following features can be obtained.
(1) When starting the engine, the ECU 22 has a temperature difference (| Tmp−Tw |) between the engine intake air temperature Tmp and the cooling water temperature Tw smaller than a predetermined value α, and at least one of the engine intake air temperature Tmp or the cooling water temperature Tw. Is lower than the predetermined temperature β, the “low temperature mode” is set. Then, a “normal temperature mode” in which the temperature difference (| Tmp−Tw |) between the engine intake air temperature Tmp and the coolant temperature Tw is smaller than a predetermined value α, and the engine intake air temperature Tmp and the coolant temperature Tw are equal to or higher than the predetermined temperature β. To do.

  That is, the engine intake air temperature sensor 15 is provided in the engine intake pipe that is more susceptible to the exhaust heat of the engine 2. For this reason, the engine intake air temperature Tmp does not necessarily coincide with the outside air temperature. However, if the temperature difference between the engine intake air temperature Tmp and the cooling water temperature (engine cooling water temperature) Tw is smaller than a predetermined value and at least one of the engine intake air temperature Tmp or the cooling water temperature Tw is lower than the predetermined temperature, the engine temperature is also It can be estimated that the temperature is low as well as the outside temperature.

  Therefore, according to the above-described configuration, it is possible to accurately determine whether the temperature is low or at room temperature without adding a new sensor. It is possible to more appropriately switch to the “low temperature mode” suitable for high temperature and low temperature, and to the “room temperature mode” suitable for normal temperature with high probability of being a high μ road. As a result, it is possible to achieve more appropriate driving force distribution according to the road surface condition and ensure good vehicle stability.

  (2) The ECU 22 stores the mode at the time of the previous engine stop (previous mode), and determines that the temperature difference (| Tmp−Tw |) between the engine intake air temperature Tmp and the coolant temperature Tw is equal to or greater than a predetermined value α. If so, the stored previous mode is continued.

  With such a configuration, when it is impossible to accurately determine whether the temperature is low due to the influence of exhaust heat of the engine 2 such as when the engine is restarted within a short time after the engine is stopped, It is possible to prevent switching to the “room temperature mode” despite the time.

In addition, you may change each said embodiment as follows.
In each of the above embodiments, the engine intake air temperature sensor 15 is used as an outside air temperature sensor. However, in a vehicle having a sensor that can directly measure the outside air temperature, such as a vehicle equipped with an air conditioner, The “engine intake air temperature Tmp” may be replaced with “outside air temperature” to perform variable driving force distribution characteristic control. Even if it changes in this way, there can exist an effect similar to said each embodiment.

  Even when an outside air temperature sensor other than the engine intake air temperature is used, the predetermined temperature T0, the predetermined speeds V1 and V2, the predetermined times t1 and t2, the predetermined value α, and the predetermined temperature β are the same as those in the above embodiments. However, it may be changed as appropriate in consideration of the distance from the heat generation part, such as an engine, and ventilation when traveling.

  Moreover, as such an outside temperature sensor, what was set in the site | part which receives the influence of the heat which an engine emits is assumed. Specifically, for example, a bumper rain (a member that connects the front ends of the left and right front side frames, a beam) disposed between the air inlet and the radiator as desired at the front air inlet of the vehicle body is provided. There are things. This may be used for multiple purposes such as air conditioning. Further, by providing the outside air temperature sensor at a location that is not easily affected by the exhaust heat of the engine, the driving force distribution characteristic variable control can be performed more appropriately.

  In each of the above embodiments, the present invention is embodied in the driving force distribution device 11 (20) of the vehicle 1 having the front wheels 6f as the main driving wheels, but the driving force distribution of the vehicles having the rear wheels 6r as the main driving wheels. It may be embodied in a device.

  In each of the above embodiments, the driving force distribution characteristic is defined by the map set 16a (16b) including the feed forward map using the vehicle speed V and the throttle opening Ra as parameters and the feedback map using the wheel speed difference Wth as parameters. However, the mode is not limited to this.

  In the first embodiment, the ECU 10 has the “provisional mode” corresponding to the engine start. However, the “provisional mode” does not necessarily need to be set. "May be the initial state.

  In the first embodiment, the transition from the “low temperature mode” to the “room temperature mode” is possible, but after changing to the “low temperature mode” once, the “low temperature mode” may be fixed. Good.

  In the first embodiment, the ECU 10 executes the mode transition, that is, the change of the driving force distribution characteristic when the vehicle speed V is equal to or lower than the predetermined speed V2 in the mode transition process. Regardless of the vehicle state quantity, the mode transition may be executed simultaneously with the mode transition determination.

In the low temperature determination process (steps 404 and 405) in the second embodiment, only one of the engine intake air temperature Tmp and the cooling water temperature Tw may be performed.
In addition, when the wheel speed difference Wth exceeds a predetermined threshold, the “low temperature mode” may be used regardless of the content of the mode transition determination.

The schematic block diagram of the driving force distribution apparatus of 1st Embodiment. The flowchart which shows the aspect of the driving force distribution characteristic variable control in 1st Embodiment. The flowchart which shows the process sequence of mode transfer determination. The flowchart which shows the aspect of a mode transfer process. The schematic block diagram of the driving force distribution apparatus of 2nd Embodiment. The flowchart which shows the aspect of the driving force distribution characteristic variable control in 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Engine, 6f ... Front wheel, 6r ... Rear wheel, 9 ... Torque coupling, 10, 22 ... ECU, 11, 20 ... Driving force distribution device, 14a-14d ... Wheel speed sensor, 15 ... Engine suction Air temperature sensor, 23 ... Water temperature sensor, Tmp ... Engine intake air temperature, Tw ... Cooling water temperature, T0, α ... Predetermined value, V ... Vehicle speed, V1, V2 ... Predetermined speed, β ... Predetermined temperature, t1, t2 ... Predetermined time, Val_md ... Mode transition judgment value.

Claims (10)

A torque coupling capable of varying the driving force distribution between the main driving wheel and the auxiliary driving wheel; and a control means for controlling the operation of the torque coupling, wherein the control means has a driving force distribution characteristic at normal temperature. A driving force distribution device having a low-temperature mode for controlling the operation of the torque coupling to distribute more driving force to the auxiliary driving wheel side,
An outside air temperature detecting means for detecting the outside air temperature of the vehicle set in the engine room that is affected by the heat generated by the engine ;
Vehicle speed detecting means for detecting the vehicle speed ,
The control means sets the low temperature mode when the outside air temperature is continuously lower than a predetermined temperature for a predetermined time, and the second state is when the outside air temperature is the predetermined temperature or higher and the vehicle speed is higher than the predetermined speed. A driving force distribution device, characterized in that when it continues for a predetermined time or longer, the room temperature mode corresponding to the room temperature is set . A torque coupling capable of varying the driving force distribution between the main driving wheel and the auxiliary driving wheel; and a control means for controlling the operation of the torque coupling, wherein the control means has a driving force distribution characteristic at normal temperature. A driving force distribution device having a low-temperature mode for controlling the operation of the torque coupling to distribute more driving force to the auxiliary driving wheel side,
Equipped with engine intake air temperature detecting means for detecting engine intake air temperature provided in the intake pipe of the engine;
The control means sets the low-temperature mode when the engine intake air temperature is continuously lower than a predetermined temperature for a predetermined time or more. The driving force distribution device according to claim 2 ,
Vehicle speed detection means for detecting the vehicle speed,
The control means sets the room temperature mode corresponding to the room temperature when the engine intake temperature is equal to or higher than the predetermined temperature and the vehicle speed is higher than the predetermined speed for a second predetermined time or longer. Driving force distribution device. In the driving force distribution device according to any one of claims 1 to 3 ,
The control means, after changing to the low temperature mode, fixes the driving force distribution characteristic to the low temperature mode. In the driving force distribution device according to any one of claims 1 to 4 ,
The control means changes the driving force distribution characteristic when the vehicle speed is equal to or lower than a second predetermined speed. A torque coupling capable of varying the driving force distribution between the main driving wheel and the auxiliary driving wheel; and a control means for controlling the operation of the torque coupling, wherein the control means has a driving force distribution characteristic at normal temperature. A driving force distribution device having a low-temperature mode for controlling the operation of the torque coupling to distribute more driving force to the auxiliary driving wheel side,
An outside air temperature detecting means for detecting the outside air temperature of the vehicle set in the engine room that is affected by the heat generated by the engine ;
With cooling water temperature detecting means for detecting the cooling water temperature of the engine,
When the engine starts, the control means
The driving is characterized in that the low temperature mode is set when a temperature difference between the outside air temperature and the cooling water temperature is smaller than a predetermined value and at least one of the outside air temperature or the cooling water temperature is lower than a predetermined temperature. Power distribution device. In the driving force distribution device according to claim 6 ,
The control means is configured to switch to a room temperature mode corresponding to the room temperature when the temperature difference is smaller than the predetermined value and the outside air temperature and the cooling water temperature are equal to or higher than the predetermined temperature. Power distribution device. A torque coupling capable of varying the driving force distribution between the main driving wheel and the auxiliary driving wheel; and a control means for controlling the operation of the torque coupling, wherein the control means has a driving force distribution characteristic at normal temperature. A driving force distribution device having a low-temperature mode for controlling the operation of the torque coupling to distribute more driving force to the auxiliary driving wheel side,
Engine intake air temperature detecting means for detecting engine intake air temperature provided in the intake pipe of the engine;
With cooling water temperature detecting means for detecting the cooling water temperature of the engine,
When the engine starts, the control means
When the temperature difference between the engine intake air temperature and the cooling water temperature is smaller than a predetermined value and at least one of the engine intake air temperature or the cooling water temperature is lower than a predetermined temperature, the low temperature mode is set. Driving force distribution device. The driving force distribution device according to claim 8 ,
The control means sets a room temperature mode corresponding to the room temperature when the temperature difference is smaller than the predetermined value and the engine intake air temperature and the cooling water temperature are equal to or higher than the predetermined temperature. Driving force distribution device. In the driving force distribution device according to claim 7 or 9 ,
The control means stores a mode of the driving force distribution characteristic when the engine is stopped, and sets the stored mode when the temperature difference is not less than the predetermined value.
A driving force distribution device characterized by the above.

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