JP4092146B2 - Vehicle drive system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle drive system, and more particularly, to a vehicle drive system capable of changing a rotational speed-torque characteristic of a vehicle drive source.
[0002]
[Prior art]
In the vehicle, a transmission is provided between the engine and the drive wheel, and the speed and torque of the drive shaft are changed by selecting a gear ratio in accordance with the running condition of the vehicle, so that the engine performance is fully exhibited. It is designed as follows. As this transmission, in addition to a continuously variable transmission that can continuously change the gear ratio, a stepped transmission that has a plurality of gear stages and that selects a gear stage that meets the driving conditions of the vehicle is known. It has been. As is well known, the gear ratio in these transmissions is changed according to a so-called shift line (shift characteristic) set in accordance with the vehicle speed and the accelerator opening.
[0003]
[Problems to be solved by the invention]
In order to select a gear ratio in accordance with the running conditions of the vehicle, the transmission has a gear ratio pattern in which the gear ratio is changed stepwise from a gear stage with a large gear ratio to a gear stage with a small gear ratio. Even when the engine has a low low-speed torque, starting is facilitated by using a gear stage having a large gear ratio.
[0004]
However, in the case of a vehicle drive source with sufficient margin for low-speed torque, if the conventional gear ratio pattern is used, the gear ratio can be changed even though there is not much need to use a gear stage with sufficient torque and a large gear ratio. Is frequently performed step by step, resulting in a so-called busy shift, and drivability is reduced.
[0005]
For example, in the case of a so-called hybrid vehicle provided with a motor for torque assist in addition to the engine as a vehicle drive source, or in an engine having an electromagnetically driven valve that has been attracting attention recently, an engine whose torque is relatively low In the case of controlling the electromagnetically driven valve so as to increase the torque even in the low-speed rotation region, it is possible to provide a margin for the low-speed torque.
[0006]
Thus, by controlling the electric motor, the electromagnetically driven valve, etc., the torque characteristic of the entire drive source of the vehicle, that is, the rotation speed-torque characteristic can be variably set, and a margin can be given to the torque in the low speed rotation region. In that case, when a conventional gear ratio pattern is used, a so-called busy shift remains and drivability may be reduced.
[0007]
An object of the present invention is to provide a vehicle drive system that solves the problems of the prior art and that can prevent busy shift and improve drivability in a vehicle that can variably set the rotational speed-torque characteristics of a vehicle drive source. is there.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a vehicle drive system according to the present invention includes a torque characteristic setting means for variably setting a rotation speed-torque characteristic of a vehicle drive source, and a gear shift that is a ratio between the gear ratio and the gear ratio. has a maximum speed ratio different gear ratios pattern with specific step is different, the rotational speed according to the torque characteristic setting means - according to the change of the torque characteristics, the rotational speed - torque characteristic changes to the high torque side according the the gear ratio of the step ratio rather more size, and characterized by comprising a speed change ratio pattern selecting means maximum speed ratio is selected more small has the speed change ratio pattern.
[0009]
With this configuration, the gear ratio pattern can be selected by changing the gear ratio step in accordance with the degree of torque margin due to the change in the rotational speed-torque characteristics of the vehicle drive source. Therefore, Rutoki and he has high torque, and larger steps of speed change ratios, it is possible to prevent the busy shifting by reducing the frequency of changing the transmission ratio.
[0011]
The vehicle drive system according to the present invention includes a plurality of torque characteristic setting means for variably setting the rotational speed-torque characteristic of the vehicle drive source, and a plurality of speed ratios with different speed ratios at different speed stages . has a shift speed pattern, the rotational speed - depending on the change of the torque characteristics, the rotational speed - torque characteristic in accordance with the change to the high torque side, the number of speeds is rather more small, and the slowest side a shift pattern selection means for the transmission ratio of the transmission stage is selected more small not the gear position pattern, characterized by comprising a.
[0012]
Here, the number of gears refers to the number of gears that can be obtained from the maximum gear ratio to the minimum gear ratio. With this configuration, it is possible to select the shift speed pattern by changing the shift speed according to the degree of torque margin due to the change in the rotation speed-torque characteristics of the vehicle drive source. Therefore, it is possible to prevent busy shifts by reducing the number of shift stages and reducing the frequency of change of shift stages when high torque is being generated.
[0014]
Further, it is preferable that the torque characteristic setting means is an electrically open / close intake valve or an electrically open / close exhaust valve which is provided in a vehicle engine as the vehicle drive source and can be electrically opened and closed. Further, the torque characteristic setting means is preferably a vehicle engine and which are both provided with an electric motor as the vehicle driving source.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a vehicle drive system 10. The vehicle drive system 10 includes an engine 13 having an electromagnetically driven valve, an electric motor 14 for assisting torque of the engine 13, a torque converter 16 having a lock-up clutch 36, and a transmission 18 connected to an output shaft 20 on the drive wheel side. A power transmission device that supplies driving force is provided. Further, the vehicle drive system 10 controls the engagement operation of the electromagnetic valve control unit 22 that controls the torque characteristics of the engine 13, the motor control unit 24 that controls the torque characteristics of the electric motor 14, and the lockup clutch of the torque converter 16. A lockup clutch control unit 26 and a transmission control unit 28 that controls the transmission 18 are provided. The entire vehicle drive system is controlled by a vehicle electronic control unit (ECU) (not shown).
[0016]
Here, the engine 13 and the electric motor 14 including the electromagnetically driven valve correspond to the vehicle drive source 12, and the electromagnetic valve control unit 22 and the electric motor control unit 24, as will be described in detail later, This corresponds to torque characteristic setting means 25 for variably setting the torque characteristic.
[0017]
The engine 13 is an internal combustion engine for vehicle travel. Each cylinder of the engine 13 is provided with an intake valve and an exhaust valve that are opened and closed by an electromagnetic actuator that is electrically controlled, that is, an electromagnetically driven valve.
[0018]
FIG. 2 shows the state of the electromagnetically driven valves 74 and 75 attached to the cylinders of the engine 13. The electromagnetically driven valves 74 and 75 correspond to an intake valve and an exhaust valve that are electrically controlled, respectively. As shown in FIG. 2, the engine 13 includes electromagnetic actuators 76 and 77 that open and close the electromagnetically driven valves 74 and 75 of the respective cylinders, and the electromagnetic valve control unit 81 detects the rotation angle of the crankshaft 79. It has a function of controlling the operation timing of the electromagnetically driven valves 74 and 75 according to a signal from the crankshaft rotation angle sensor 80.
[0019]
This solenoid valve control unit 81 not only changes the operation timing to the optimal time according to the engine load, but also becomes a time for operating the engine 13 in four cycles and a time for operating in two cycles according to the operation cycle switching command. To control. Further, the engine speed can be controlled by the engine itself by changing the operation timing of the electromagnetically driven valves 74 and 75 or changing the number of operating cylinders. For example, by opening and closing the exhaust valve in accordance with normal control while the intake valve is closed, the rotational energy can be consumed by the compression work of the piston, and the engine rotation speed can be forcibly and rapidly reduced. The rate of change of the engine speed can be adjusted by controlling the degree of opening. Further, for example, the electromagnetically driven valves 74 and 75 can be controlled to increase the torque even in the low speed rotation region of the engine where the torque falls.
[0020]
Thus, by controlling the electromagnetically driven valves 74 and 75, the rotational speed-torque characteristic of the engine 13 can be variably set.
[0021]
FIG. 3 shows a cross-sectional view of the electromagnetic actuators 76 and 77. The electromagnetic actuators 76 and 77 are connected to the electromagnetically driven valves 74 and 75 and supported so as to be movable in the axial direction of the electromagnetically driven valves 74 and 75, and a movable member 82 made of a magnetic material. A pair of electromagnets 84 and 85 are provided at positions sandwiching them in order to selectively attract 82, and a pair of springs 86 and 87 for urging the movable member 82 toward the neutral position. .
[0022]
The electric motor 14 is a motor that generates vehicle driving force, and is coupled to the output shaft of the engine 13. For example, it has a function of torque assist that is operated at a low rotational speed of the engine 13 to compensate for the insufficient torque. When the output of the engine 13 is sufficient, the motor 14 can be used as a generator to provide a function of recovering excess energy. The sum of the torque of the engine 13 and the torque supplied by the electric motor 14 is transmitted to the torque converter 16 as the torque of the vehicle drive source. Control such as torque assist of the electric motor 14 is performed by the electric motor control unit 24 controlling an inverter control circuit (not shown).
[0023]
Thus, by controlling the torque characteristic of the electric motor 14, the rotational speed-torque characteristic of the entire vehicle drive source including the engine 13 and the electric motor 14 can be variably set.
[0024]
The torque converter 16 is torque transmission means for transmitting the torque of the vehicle drive source side member to the transmission side member, which is a driven side member, by a fluid. The torque converter 16 includes a pump impeller 32 connected to the output shaft 15 of the vehicle drive source, a turbine impeller 34 connected to the input shaft 17 to the transmission 18, and the pump impeller 32 and the turbine impeller 34. And a lock-up clutch 36 for directly connecting the two. The lock-up clutch 36 is not engaged at the time of rising of the torque of the vehicle drive source, and causes torque amplification via the fluid between the pump impeller 32 and the turbine impeller 34, so that the torque of the vehicle drive source is sufficient. After starting up, it has a function of engaging and transmitting the torque of the vehicle drive source directly to the transmission. Further, it is possible to perform slip control in which torque is transmitted by sliding at a predetermined engagement pressure in an intermediate state between release and engagement. Control of engagement of the lockup clutch 36 is performed by the lockup clutch control unit 26 controlling an engagement hydraulic actuator (not shown).
[0025]
The transmission 18 is provided between the vehicle drive source and the drive wheel, and has a function of sufficiently exerting the performance of the vehicle drive source by selecting a gear ratio in accordance with the traveling condition of the vehicle. As is well known, the interior of the transmission 18 is composed of a plurality of planetary gears and a plurality of brakes for fixing the movement of sun gears, ring gears and the like that are constituent elements of the planetary gears. The transmission ratio between the input shaft 17 of the transmission 18 and the output shaft 20 to the drive wheel is defined by a combination of the number of teeth of the sun gear and the ring gear of each planetary gear. The speed ratio is changed according to a constant speed ratio pattern. The transmission 18 includes a plurality of transmission ratio patterns, and the transmission control unit 28 performs selection of the transmission ratio pattern and control of changing the transmission ratio in the selected transmission ratio pattern.
[0026]
FIG. 4 is a diagram showing an input / output relationship of an electronic control unit (ECU) 50 that controls the entire vehicle drive system. The electronic control device 50 receives signals representing the engine speed, the vehicle speed, the accelerator opening, etc., and judges the traveling condition of the vehicle, the operating state of the engine, etc., and the electromagnetically driven valve signal is sent to the electromagnetic valve control unit 22. The motor controller signal is output to the motor controller 24. Further, a reduction gear signal is output to the shift control unit 28, and an AT lockup control solenoid signal is output to the lockup clutch control unit 26.
[0027]
The operation of the vehicle drive system in this embodiment will be described using the torque characteristics of the vehicle drive source shown in FIG. 5, that is, the rotation speed-torque characteristics. When neither the electromagnetically driven valve nor the electric motor is operated, the torque characteristic of the vehicle drive source is a torque characteristic unique to the engine. That is, as is generally known, the torque is low in the region where the rotational speed is low, the torque increases as the rotational speed increases, and after reaching the maximum torque, the torque gradually increases as the rotational speed further increases. The torque characteristic curve is decreasing. The engine-specific torque characteristic curve that becomes a mountain with respect to the rotational speed change is referred to as a first torque mode 60.
[0028]
Next, the electromagnetic valve control unit 22 is controlled by the electromagnetically driven valve signal of the electronic control unit 50, and the torque characteristics of the vehicle drive source can be variably set by controlling the electromagnetically driven valve provided in the engine. For example, when it is detected from the engine speed signal that the engine speed has decreased, an electromagnetic valve signal for changing the opening / closing timing of the electromagnetically driven valve can be output to the electromagnetic valve control unit 22. Thus, for example, even if the rotational speed decreases from the rotational speed of the maximum torque, it can be a torque characteristic curve that maintains the torque without being reduced. Now, a torque characteristic curve that controls the electromagnetically driven valve and has a substantially constant torque at a low rotational speed will be referred to as a second torque mode 62.
[0029]
The torque characteristic of the vehicle drive source can also be variably set by controlling the motor control unit 24 by the motor controller signal of the electronic control unit 50 and controlling the operation of the motor. For example, when the engine output is estimated from the vehicle speed signal and the accelerator opening signal and it is detected that the estimated torque is low, an electric motor controller signal instructing the electric motor operation can be output to the electric motor control unit 24. Thus, for example, torque assist can be performed in a low rotation speed region, for example, and the torque can be further increased to obtain a torque characteristic curve that is larger than the engine-specific maximum torque. Now, the electric motor is controlled, and the torque characteristic curve that falls to the right with respect to the change in the rotational speed is referred to as a third torque mode.
[0030]
As described above, when the torque characteristic of the vehicle drive source is changed by electrically controlling the electromagnetically driven valve or the electric motor, the electronic control unit 50 controls the shift control unit 28 according to the changed torque characteristic. A reduction gear signal is output. For example, depending on whether the torque mode is the first torque mode, the second torque mode, or the third torque mode, or among them, a different reduction gear signal is output depending on the difference in torque characteristics. The reduction gear signal includes a control instruction related to selection of a gear ratio pattern corresponding to the changed torque characteristic and change of the gear ratio in the selected gear ratio pattern.
[0031]
FIGS. 6A and 6B show examples of transmission ratio patterns and shift speed patterns, respectively. The gear ratio pattern A and the gear stage pattern A have a minimum gear ratio (deceleration) ratio of 0.591, a maximum gear ratio (deceleration) ratio of 3.721, and the gear ratio between the adjacent gear speeds is eight. The gear ratio step that is the ratio is 1.3, and the range of the gear ratio that is the ratio between the maximum gear ratio and the minimum gear ratio is 3.721 / 0.591.
[0032]
The gear ratio pattern B and the gear stage pattern B have the same minimum gear ratio as the gear ratio pattern A, the gear ratio step is 1.5 larger than the gear ratio pattern A, and the gear ratio is the gear ratio ratio A The maximum gear ratio is set to 6 stages closest to the maximum gear ratio. The speed ratio range at this time is 3.375 / 0.591, which is a value different from the speed ratio pattern A.
[0033]
The transmission ratio pattern C and the transmission speed pattern C are the same as the transmission ratio pattern A and the transmission ratio range, and the transmission ratio step is 1.3 * 1.3 = 1.69. That is, the gear ratio pattern C is obtained by thinning the gear ratio of the gear ratio pattern A to increase the gear ratio step.
[0034]
FIG. 7 is a flowchart illustrating a procedure for selecting a gear ratio pattern or a gear stage pattern according to the torque characteristics of the vehicle drive source. S10 is a torque mode determination step of determining whether or not the torque characteristic is the first torque mode. The torque control can be determined by the electronic control unit from the contents of the electromagnetically driven valve signal and the motor controller signal. For example, when the content of the electromagnetically driven valve signal is a normal valve opening / closing control instruction, and the motor controller signal is a control instruction without torque assist, the first torque mode can be determined.
[0035]
S12 is a step of selecting the gear ratio pattern A or the gear position pattern A in the first torque mode. The electronic control unit selects a speed ratio pattern A or a speed stage pattern A and outputs a speed reduction device signal for performing speed ratio change control in the speed ratio control unit. As described above, in the first torque mode unique to the engine, gear shifting is performed with a small gear ratio.
[0036]
S14 is a step that proceeds when it is determined that the torque mode is not the first torque mode, and is a step of selecting the gear ratio pattern B or the gear stage pattern B. The electronic control unit outputs a reduction gear signal for selecting the gear ratio pattern B or the gear stage pattern B to the gear shift control unit. When it is not the first torque mode, it is the second torque mode or the third torque mode, and the torque is sufficient even at a low rotational speed as compared with the torque characteristic unique to the engine. Therefore, the vehicle can travel sufficiently even at the current gear position, and there are few problems even if a large gear ratio step is taken when a gear shift is required. Therefore, by selecting the gear ratio pattern B or the gear stage pattern B in which the gear ratio step is set larger than the gear ratio pattern A, the number of change of the gear ratio can be reduced, preventing a busy shift, Drivability can be improved.
[0037]
Further, the electronic control device can determine whether the second torque mode or the third torque mode is in accordance with the contents of the motor controller signal. Therefore, when determining the third torque mode, the gear ratio pattern C or the gear stage pattern C can be selected. Thereby, the change of the gear ratio can be further reduced as compared with the gear ratio pattern B and the like, and the drivability is further improved.
[0038]
Further, since the magnitude of the torque characteristic can be determined in more detail from the contents of the electromagnetically driven valve signal and the contents of the electric motor controller signal, the gear ratio pattern A, the gear ratio pattern B, the gear ratio pattern C, etc. according to the magnitude of the torque characteristic. The selection criteria between can also be defined.
[0039]
The change of the gear ratio in the selected gear ratio pattern can be performed so as to conform to the torque mode of the torque characteristics and the running condition of the vehicle. That is, a suitable gear ratio is selected from a vehicle speed signal, an accelerator opening, an engine rotation speed signal, an electromagnetically driven valve signal, an electric motor controller signal, and the like.
[0040]
The gear ratio can be changed by sequentially switching the shift stage of the vehicle from the low speed stage to the high speed stage or from the high speed stage to the low speed stage at the shift position “D”, that is, the forward change position by automatic gear shifting. Further, when a predetermined gear stage is selected with + or-as in the so-called shift steer gear stage hold type, the gear ratio can be changed to a different speed ratio with one + or-.
[0041]
【The invention's effect】
The vehicle drive system according to the present invention can prevent busy shift and improve drivability in a vehicle in which the rotation speed-torque characteristic of the vehicle drive source can be set variably.
[Brief description of the drawings]
FIG. 1 is a block diagram of a vehicle drive system according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an electromagnetically driven valve provided in an engine.
FIG. 3 is a cross-sectional view of an electromagnetic actuator.
FIG. 4 is a diagram showing an input / output relationship of the electronic control unit.
FIG. 5 is a diagram showing torque characteristics of a vehicle drive source.
FIG. 6 is a diagram showing an example of a gear ratio pattern and a gear stage pattern in the embodiment according to the present invention.
FIG. 7 is a flowchart showing a procedure for selecting a gear ratio pattern or a gear stage pattern according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Vehicle drive system, 12 Vehicle drive source, 13 Engine, 14 Electric motor, 16 Torque converter, 18 Transmission, 22 Solenoid valve control part, 24 Electric motor control part, 28 Transmission control part, 50 Electronic control unit (ECU), 60 First torque mode, 62 Second torque mode, 64 Third torque mode, 74, 75 Electromagnetically driven valve, 76, 77 Electromagnetic actuator.

Claims (4)

Torque characteristic setting means for variably setting the rotational speed-torque characteristic of the vehicle drive source;
Gear ratio and has a maximum speed ratio different gear ratios pattern in which when the transmission ratio step is different ratios between the speed ratio, the rotational speed according to the torque characteristic setting unit - in response to a change in torque characteristics the rotational speed - in accordance with the torque characteristic is changed to the high torque side, the step ratio between the gear ratio is rather more large, and the speed change ratio pattern selecting means maximum speed ratio is selected more small have gear ratios pattern, the the vehicle drive system characterized by comprising. Torque characteristic setting means for variably setting the rotational speed-torque characteristic of the vehicle drive source;
A transmission gear ratio of the gear stage of the lowest speed side when the transmission number is different from a plurality of different shift speeds pattern, the rotational speed according to the torque characteristic setting means - according to the change of the torque characteristics, the rotational speed - torque characteristic it but in accordance with the change to the high torque side, with a, a shift speed pattern selecting means for gear ratio of the gear position of the shift stages is rather more low, and the lowest speed side to select a more small not the gear position pattern A vehicle drive system.   3. The vehicle drive system according to claim 1, wherein the torque characteristic setting means is an electrically open / close intake valve or an electrically open / close exhaust that is provided in a vehicle engine as the vehicle drive source and can be electrically opened and closed. A vehicle drive system characterized by being a valve.   3. The vehicle drive system according to claim 1, wherein the torque characteristic setting unit is an electric motor provided with a vehicle engine as the vehicle drive source. 4.

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