JP6550747B2 - Vehicle control device - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine that detects a road surface condition of a traveling path to control a compression ratio of the internal combustion engine.

  For example, Patent Document 1 discloses a technique of changing the compression ratio based on the road shape of the traveling path on which the vehicle travels. In Patent Document 1, road shape data on which the vehicle travels is analyzed from GPS signals, map information, and road traffic information, and a compression ratio is set according to the analyzed road shape of the travel path.

JP 2011-256719 A

  However, the road surface condition of the traveling road under the actual traffic environment changes from moment to moment due to, for example, the weather, and compression ratio control based on the road shape based on predetermined map data does not necessarily adapt to the current driving condition. The compression ratio control may not be performed.

  That is, there is a prediction of further improvement in controlling the compression ratio during traveling of the vehicle in accordance with the environment outside the vehicle.

A control device for a vehicle according to the present invention includes an internal combustion engine mounted on the vehicle, a compression ratio variable mechanism capable of changing the compression ratio of the internal combustion engine, and a road surface state detection unit capable of detecting a road surface state of a traveling road. In the state where the accelerator opening is constant, if the road surface friction coefficient of the traveling road is smaller than a predetermined value, it is predicted that the future driving state will shift to the low rotation low load driving state, and the target compression ratio Is relatively high.

  When the road surface condition of the traveling road is a state where the friction coefficient is small, it is not practical to cause the vehicle to travel in a high rotation and high load driving condition because the driving force is hard to be transmitted to the road surface. Therefore, when it is detected that the friction coefficient of the traveling path is smaller than a predetermined value, it is predicted that the driving state of driving will shift to the low rotation and low load driving state in the future, and there is no operation request from the driver. Also increase the compression ratio.

  According to the present invention, it is possible to set an appropriate compression ratio according to the external environment of the vehicle without increasing the response speed of the variable compression ratio mechanism, as compared to the case where the compression ratio is changed after waiting for an operation request from the driver. Well realized.

Explanatory drawing which showed typically schematic structure of the control apparatus of the vehicle which concerns on this invention. Target compression ratio calculation map. Explanatory drawing which showed typically schematic structure of the control apparatus of the vehicle which concerns on this invention. Road friction coefficient estimation map using wheel rotation speed. Road friction coefficient estimation map using lateral acceleration. The timing chart shown contrasting compression ratio change by driver operation, and compression ratio change by high compression ratio control. The flowchart which shows the flow of control during vehicle travel.

  Hereinafter, an embodiment of the present invention will be described in detail based on the drawings. FIG. 1 is an explanatory view schematically showing a schematic configuration of a control device for a vehicle according to the present invention.

  The internal combustion engine 1 has a variable compression ratio mechanism 14 capable of changing the engine compression ratio by changing the top dead center position of the piston 13 reciprocating in the cylinder 12 of the cylinder block 11.

  The variable compression ratio mechanism 14 utilizes a multi-link type piston-crank mechanism in which the piston 13 and the crank pin 16 of the crankshaft 15 are linked by a plurality of links, and is rotatably mounted on the crank pin 16 Lower link 17, upper link 18 connecting lower link 17 and piston 13, control shaft 19 provided with eccentric shaft portion 20, and control link 21 connecting eccentric shaft portion 20 and lower link 17 ,have.

  The crankshaft 15 is rotatably supported by the first bearing bracket 22 on the cylinder block 11.

  The upper link 18 is rotatably attached at one end to the piston pin 23 and is rotatably connected at the other end to the lower link 17 by the first connection pin 24. One end of the control link 21 is rotatably connected to the lower link 17 by the second connection pin 25, and the other end is rotatably attached to the eccentric shaft portion 20 of the control shaft 19.

  The control shaft 19 is disposed parallel to the crankshaft 15 and rotatably supported by the cylinder block 11. Specifically, the control shaft 19 is rotatably supported between the first bearing bracket 22 and the second bearing bracket 26.

  The control shaft 19 is rotationally driven by an actuator 28 formed of an electric motor via a gear mechanism 27 and its rotational position is controlled. The actuator 28 is controlled based on a command from the control unit 31. The control shaft 19 may be rotationally driven by a hydraulic actuator.

  By changing the rotational position of the control shaft 19 by the actuator 28, the position of the eccentric shaft portion 20 serving as the fulcrum of the control link 21 changes. As a result, the posture of the lower link 17 by the control link 21 changes, and the compression ratio becomes continuous with changes in the piston motion (stroke characteristics) of the piston 13, ie, the top dead center position and the bottom dead center position of the piston 13. Changed to

  The control unit 31 incorporates a microcomputer and performs various controls of the internal combustion engine 1, and based on signals from various sensors, the fuel injection amount, fuel injection timing, ignition timing, throttle opening degree, compression Control the ratio etc. As various sensors, an accelerator opening degree sensor 32 for detecting an accelerator pedal depression amount (accelerator opening degree APO) representing a required load state of the internal combustion engine 1, a brake pedal sensor 33 for detecting a depression amount of a brake pedal not shown There are a crank angle sensor 34 capable of detecting an engine speed as well as a crank angle of the crankshaft 15, a vehicle speed sensor 35 detecting a vehicle speed of a vehicle equipped with the internal combustion engine 1, an outside air temperature sensor 36 detecting an outside air temperature, and the like.

  The compression ratio of the internal combustion engine 1 is controlled in accordance with the operating state. In the present embodiment, a target compression ratio map to which a target compression ratio is assigned is stored in the control unit 31 according to the rotational speed of the internal combustion engine 1 (engine rotational speed) and the load of the internal combustion engine 1 (engine load). The target compression ratio is set based on the target compression ratio map.

  FIG. 2 schematically shows an example of the target compression ratio calculation map. The compression ratio is high on the low rotation low load side, and is low on the high rotation high load side. That is, in FIG. 2, the compression ratio is set so that the operating state shifts from the low rotation low load region to the high rotation high load region and thus gradually decreases from the predetermined maximum compression ratio, and finally the predetermined A minimum compression ratio is set. In FIG. 2, the compression ratio is set to the highest compression ratio in the operation area surrounded by the horizontal axis and the broken line in the figure, and the compression ratio is set to a lower value outside the operation area. Further, a solid line L in FIG. 2 is a torque curve when the throttle is fully opened (at the time of WOT).

  Further, as shown in FIG. 1 and FIG. 3, the control unit 31 is connected to the brake control unit 41 via a CAN communication line 42 capable of exchanging information mutually.

  The brake control unit 41 includes a first wheel speed sensor 43 that detects the number of rotations (rotational speed) of the right front wheel, a second wheel speed sensor 44 that detects the number of rotations (rotational speed) of the front left wheel, and a rotation of the right rear wheel The third wheel speed sensor 45 detects the number (rotational speed), the fourth wheel speed sensor 46 detects the rotational speed (rotational speed) of the rear wheel left, and the steering angle detects the steering angle of the steering wheel (not shown) Sensor 47, Lateral G sensor 48 for detecting the lateral acceleration of the vehicle, yaw rate sensor 49 for detecting the rotational angular velocity of the vehicle, Brake pressure for detecting the brake fluid pressure (master cylinder pressure) generated according to the driver's brake operation A signal from the sensor 50 or the like is input.

  The brake control unit 41 controls the differential pressure between the brake fluid pressure and the wheel cylinder pressure supplied to the disc brakes (not shown) of the respective wheels of the vehicle by means of the brake actuator 51 so that the wheel rotation at the time of braking is performed. It performs various types of brake control such as so-called anti-lock brake control that detects the number and prevents locking of the wheels (tires), and vehicle behavior control that prevents the sideslip of the vehicle when the attitude of the vehicle is disturbed. . Reference numeral 52 in FIG. 3 denotes hydraulic piping that supplies hydraulic pressure from the brake actuator 51 to the disk brakes of the respective wheels.

  The antilock brake control determines that the wheels are locked when the rotational speed of the wheels decreases with respect to the traveling speed of the vehicle at the time of sudden braking, and the hydraulic pressure of each wheel is intermittently adjusted by the brake actuator 51. Is to avoid the lock.

  The above-mentioned vehicle behavior control is, for example, a state where the turn of the vehicle can not catch up with it (understeer) even if the steering wheel is operated (turned), or the vehicle tends to spin on a specific road surface or driving At the time of oversteer, the output of the internal combustion engine 1 and the wheel cylinder pressure at the individual wheels are controlled so that the attitude of the vehicle is corrected (so that the vehicle does not skid). The above-mentioned vehicle behavior control also has a function of controlling the wheel cylinder pressure in order to reduce the slip of the drive wheel on the slipping side, and transmitting power to the non-slip side driving wheel on the same axle. .

  When the road surface condition of the traveling road is a state where the friction coefficient is small, it is not practical to cause the vehicle to travel in a high rotation and high load driving condition because the driving force is hard to be transmitted to the road surface. Therefore, if it is detected that the friction coefficient of the traveling path is smaller than a predetermined value during high load and high speed operation, the future operation state becomes the low rotation and low load operation state, and the compression ratio of the internal combustion engine 1 is high compression ratio. Can be predicted.

  Here, the antilock brake control and the vehicle behavior control both control the slip between the wheel (tire) and the traveling path, and in a vehicle capable of performing these controls, existing control The system can be used to detect the road surface friction coefficient of the traveling road.

  In a vehicle capable of performing the above antilock brake control, the wheel rotational speed (reference wheel rotational speed) on a dry road (high μ road) is calculated in advance from the vehicle speed and the wheel radius (wheel moving radius) during traveling. If the reference wheel rotational speed corresponding to the vehicle speed on the dry road (high μ road) does not match the actual wheel rotational speed, it is possible to estimate that the road surface state of the traveling road has a small coefficient of friction.

  The wheel rotation speed also varies depending on tire wear and the type of tire. In addition, the wheel rotation speed of the front wheels fluctuates due to steering. Furthermore, if the traveling path is a curved road, the wheel rotational speed fluctuates between the inner ring and the outer ring. Therefore, in the present embodiment, in consideration of these rotational fluctuations, as shown in FIG. 4 for example, a dry road (high μ road) rotational speed range including the characteristic line A representing the reference wheel rotational speed is set. Then, when the actually detected wheel rotational speed deviates from the dry road (high μ road) rotational speed range, it is determined that the road surface state of the traveling road has a small coefficient of friction.

  The characteristic line Amax in FIG. 4 is a characteristic line that represents the upper limit value of the reference wheel rotational speed corresponding to the vehicle speed, and the characteristic line Amin in FIG. 4 is the lower limit value of the reference wheel rotational speed corresponding to the vehicle speed. It is a characteristic line to represent. Further, in the example shown in FIG. 4, the characteristic line A is set so as not to overlap the characteristic line Amax and the characteristic line Amin, but if possible, part or all of the characteristic line Amax or the characteristic line Amin A may be set to match A.

  In the example of FIG. 4, the wheel is in a slip state when the wheel rotational speed is larger than the upper limit value of the predetermined dry road (high μ road) rotational speed range determined in accordance with the vehicle speed in a state where the accelerator pedal is depressed. Therefore, it is determined that the road surface friction coefficient of the traveling road is small. Also, if the wheel rotational speed is smaller than the lower limit value of the dry road (high μ road) rotational speed range determined according to the vehicle speed while the brake pedal is depressed, the road is locked because the wheels are locked. It is determined that the road surface friction coefficient is small.

  The wheel rotation number used when determining the road surface friction coefficient of the traveling path is, for example, one wheel rotation number among a plurality of drive wheels, one wheel rotation number among all the wheels, and one of a plurality of drive wheels. An average value, an average value of all the wheels, and the like can be set as appropriate. Also, the road surface friction coefficient of the traveling path may be estimated for every wheel, and the road surface friction coefficient of the traveling path may be comprehensively estimated based on these results.

  Further, in a vehicle capable of performing the above-mentioned vehicle behavior control, lateral acceleration (reference lateral acceleration) of the vehicle on a dry road (high μ road) is calculated in advance from the vehicle speed and the steering angle. If the reference lateral acceleration corresponding to the vehicle speed and the steering angle on the road (high μ road) does not coincide with the actual lateral acceleration, it can be estimated that the road surface state of the traveling road has a small coefficient of friction.

  Lateral acceleration also fluctuates depending on conditions during driving. For example, if the bank angle of the road surface is large, the lateral acceleration decreases even at the same steering angle and vehicle speed. Therefore, in the present embodiment, in consideration of fluctuations due to various conditions during operation, as shown in FIG. 5, for example, a dry road (high μ road) lateral acceleration region including a characteristic line B representing the reference lateral acceleration is set. Set. This map is prepared for each vehicle speed or for each predetermined vehicle speed range. Then, when the lateral acceleration actually detected deviates from the dry road (high μ road) lateral acceleration area in the map corresponding to the current vehicle speed, it is determined that the road surface state of the traveling road has a small friction coefficient To do.

  The characteristic line Bmax in FIG. 5 is a characteristic line that represents the upper limit value of the reference lateral acceleration corresponding to the vehicle speed and the steering angle, and the characteristic line Bmin in FIG. 5 is a reference lateral direction corresponding to the vehicle speed and the steering angle. It is a characteristic line showing the lower limit value of directional acceleration. Further, in the example shown in FIG. 5, the characteristic line B is set so as not to overlap with the characteristic line Bmax and the characteristic line Bmin, but if possible, part or all of the characteristic line Bmax or the characteristic line Bmin You may set so that it may correspond to B.

  In the example of FIG. 5, when the lateral acceleration is larger than the upper limit value of the dry road (high μ road) lateral acceleration area determined according to the vehicle speed and the steering angle, the road surface friction on the traveling road It is determined that the coefficient is small. If the lateral acceleration is smaller than the lower limit value of the dry road (high μ road) lateral acceleration range determined according to the vehicle speed and the steering angle, it is determined that the road surface friction coefficient of the travel road is small because it is understeer. To do.

  Then, in a vehicle capable of performing the above antilock brake control and the above vehicle behavior control, when it is detected that the friction coefficient of the traveling road is smaller than a predetermined value, the compression ratio is made high by waiting for the driver's operation request. Instead of changing it, change the compression ratio to be high at that time. For example, if there is a sudden change in weather while traveling on a dry road at a low compression ratio, or if there is a portion where the road surface friction coefficient is partially small while traveling on a mountain road at a low compression ratio, etc. If it is detected that the road surface condition of the traveling road has a small coefficient of friction from the change in the external environment earlier than the driver's operation, the compression ratio is requested before the driver's operation requests a compression ratio increase. Start high compression ratio control to start raising.

  FIG. 6 is a timing chart showing the change of the compression ratio by the driver's operation and the change of the compression ratio by the high compression ratio control in comparison.

  While traveling on a dry road (high μ road), when it is detected that the road surface friction coefficient becomes smaller at time t1 and the road surface friction coefficient of the road becomes smaller at time t2, the accelerator opening degree becomes smaller at time t2. In anticipation of becoming smaller, the target compression ratio is switched to a relatively high compression ratio, and the actual compression ratio starts to gradually change from time t2 toward the target value.

  Here, as indicated by a broken line in FIG. 6, when the driver notices a change in the road surface condition of the traveling road and returns the access pedal at time t3 later than time t2, the compression ratio is set from this time t3. Is started, the timing at which the compression ratio becomes a compression ratio suitable for the road surface condition of the traveling road is relatively delayed.

  That is, in this embodiment, it is possible to switch the target compression ratio to a compression ratio suitable for the road surface condition of the traveling road earlier than the timing when the driver notices the change of the road surface condition of the traveling road and returns the access pedal. Become.

  However, when it is detected that the friction coefficient of the traveling path is smaller than a predetermined value, if the low rotation and low load operation state has already been made, the compression ratio is already high, so it is not necessary to further increase the compression ratio.

  Thus, in the present embodiment, as compared with the case where the compression ratio is changed after waiting for an operation request from the driver, the appropriate compression according to the external environment of the vehicle can be made without increasing the response speed of the variable compression ratio mechanism 14 The ratio setting can be realized with high accuracy.

  Further, when the actuator 28 is an electric motor, the actuator 28 can be replaced with one having a relatively low output performance, and cost reduction can be achieved. In addition, even when the actuator 28 is not replaced with one having a relatively low output performance, it is possible to relatively reduce the drive energy (drive current value) of the actuator 28 to reduce the power consumption, thereby improving the fuel consumption as a whole. can do.

  FIG. 7 is a flowchart showing the flow of control during traveling of the vehicle according to the embodiment described above.

In S1, it is determined whether or not brake control such as antilock brake control or vehicle behavior control is being performed, and if it is being performed, the process proceeds to S2, and if it is not being performed, the present routine is ended. In S2, various driving states such as an accelerator opening degree, an engine rotational speed, a vehicle speed, a wheel rotational speed, a steering angle, and a lateral acceleration of the vehicle are detected. In S3, it is determined whether or not the road surface friction coefficient of the traveling road is small. Specifically, whether the road surface friction coefficient of the traveling road is small or not is determined from the comparison between the reference wheel rotation number and the actual wheel rotation number described above and the comparison between the reference lateral acceleration and the actual lateral acceleration described above. judge. When it is determined that the road surface friction coefficient of the traveling road is small, the process proceeds to S4, and when it is not determined that the road surface friction coefficient of the traveling road is small, the current routine is ended. In S4, the compression ratio of the internal combustion engine is equal to or a low compression ratio, the process proceeds to S5 If low compression ratio, and terminates the low compression ratio unless the current routine. In S5, the high compression ratio control request is turned on because there is a request for the high compression ratio control described above. In S6, when the high compression ratio control request is turned ON, the high compression ratio control is started. The high compression ratio control request becomes OFF when the operation state changes and the target compression ratio is switched to the high compression ratio.

  When the outside air temperature is lower than the predetermined temperature, it can be determined that the road surface friction coefficient of the traveling road is small. This is because if the outside air temperature is a low temperature such as below freezing, for example, it can be estimated that the friction coefficient of the road surface is as low as an icing road.

  Further, whether the road surface friction coefficient of the traveling road is small can be determined by using the wheel rotation speed, by using the lateral acceleration, or by using the outside air temperature, and by combining these three, It is possible to accurately estimate the road surface friction coefficient of the traveling road. In addition, the control device for a vehicle according to the present invention may be configured to include at least one of these three determination methods.

14 ... variable compression ratio mechanism 28 ... actuator 31 ... control unit 32 ... accelerator opening sensor 33 ... brake pedal sensor 34 ... crank angle sensor 35 ... vehicle speed sensor 36 ... outside air temperature sensor 41 ... brake control unit 42 ... CAN communication line 43 ... 1st wheel speed sensor 44 ... 2nd wheel speed sensor 45 ... 3rd wheel speed sensor 46 ... 4th wheel speed sensor 47 ... steering angle sensor 48 ... lateral G sensor 49 ... yaw rate sensor 50 ... brake pressure sensor 51 ... brake actuator

Claims (6)

An internal combustion engine mounted on a vehicle,
A compression ratio variable mechanism capable of varying the compression ratio of the internal combustion engine;
A road surface state detection unit capable of detecting the road surface state of the traveling road,
If the road surface friction coefficient of the traveling road is smaller than a predetermined value in a state where the accelerator opening is constant, it is predicted that the future driving state will shift to the low rotation and low load driving state, and the target compression ratio is relatively A control device of a vehicle characterized by raising.   When the accelerator pedal is depressed, the accelerator pedal depression detection unit detecting the depression amount of the accelerator pedal, the vehicle speed detection unit detecting the vehicle speed, and the wheel speed detection unit detecting the number of revolutions of the wheel The vehicle according to claim 1, wherein the road surface state detecting unit determines that the road surface friction coefficient is small when the number of revolutions of the wheel is larger than an upper limit value of a predetermined number of revolutions determined according to the vehicle speed. Control device.   When the brake pedal is depressed, the brake pedal depression detection unit detecting the depression amount of the brake pedal, the vehicle speed detection unit detecting the vehicle speed, and the wheel speed detection unit detecting the number of revolutions of the wheel The road surface state detecting unit determines that the road surface friction coefficient is small when the number of revolutions of the wheel is smaller than the lower limit value of a predetermined number of revolutions range determined according to the vehicle speed. Vehicle control device.   The vehicle includes a steering angle detection unit that detects a steering angle of a steering wheel of the vehicle, and a lateral acceleration detection unit that detects a lateral acceleration of the vehicle, and the vehicle rotates when the steering wheel is operated. When the lateral acceleration is larger than the upper limit value of the predetermined acceleration range determined according to the vehicle speed and the steering angle of the steering wheel, the road surface state detecting unit determines that the road surface friction coefficient is small. The control apparatus of the vehicle in any one of -3.   The vehicle includes a steering angle detection unit that detects a steering angle of a steering wheel of the vehicle, and a lateral acceleration detection unit that detects a lateral acceleration of the vehicle, and the vehicle rotates when the steering wheel is operated. When the lateral acceleration is smaller than the lower limit value of the predetermined acceleration range determined according to the vehicle speed and the steering angle of the steering wheel, the road surface state detecting unit determines that the road surface friction coefficient is small. The control apparatus of the vehicle in any one of -4.   The outside air temperature detection unit for detecting the temperature outside the vehicle, wherein when the outside air temperature is lower than a predetermined temperature, the road surface condition detection unit determines that the road surface friction coefficient is small. The vehicle control device according to any one of the above.

Images