JPH0440217B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a vehicle power plant including a continuously variable transmission.

[Conventional technology]

In conventional vehicles, the intake system throttle valve is connected to the accelerator pedal in the driver's cab via a link or wire, and the throttle opening is directly controlled by the driver's operation of the accelerator pedal, and the amount of air supplied is controlled accordingly. The output torque of the engine is increased or decreased.
In addition, in conventional transmissions, the gear ratio is selected directly by the driver's shift lever operation in the case of a manual transmission, or as a function of the throttle opening and vehicle speed in the case of an automatic transmission. There is. It is preferable for an internal combustion engine to be operated at a minimum fuel consumption rate, but the gear ratio of a conventional transmission is set in consideration of drivability in the case of acceleration, and is stepped. It has been difficult to operate an internal combustion engine at a minimum fuel efficiency over the entire operating range. Therefore, the present applicant has previously provided a vehicle power unit that can control the operation of an internal combustion engine at a minimum fuel efficiency rate over the entire operating range using a continuously variable transmission. According to this, in a vehicle power system in which the rotation of the internal combustion engine is transmitted to the drive wheels via a continuously variable transmission, the required horsepower of the internal combustion engine is determined as a function of the amount of depression of the accelerator pedal or a signal corresponding thereto. The output torque and rotational speed of the internal combustion engine that can achieve horsepower at the minimum fuel efficiency rate are determined as the target output torque and target rotational speed, and the gear ratio of the continuously variable transmission is fed back so that the rotational speed of the internal combustion engine becomes the target rotational speed. The amount of air or fuel supplied to the internal combustion engine is feedback-controlled so that the output torque of the internal combustion engine becomes the target output torque.

[Problem to be solved by the invention]

However, in the case of the vehicle power plant described above, it is best in terms of fuel consumption to quickly change the engine rotation speed to the target rotation speed so as to generate the required horsepower, but it is best for the fuel consumption rate. From this point of view, the following inconveniences arise. That is, Te: engine output torque, J: engine and CVT (continuously variable
moment of inertia of a part of the transmission),
When Ne: engine rotational speed and Tout: torque transmitted from the engine to the CVT, the following equation is established from the equation of motion. Te=JN〓e+Tout...(1) ∴Tout=Te-J・N〓e......(2) However, N〓e is the time differential of Ne, that is, the acceleration of engine rotation. From equation (2), CVT output torque Tout
It can be seen that is also related to J・N〓e. Therefore, when the engine rotation speed Ne suddenly increases when the accelerator pedal is pressed for acceleration, Ne increases,
Tout decreases, and in extreme cases Te<J・N〓e, Tout becomes negative and the vehicle decelerates, and when the accelerator pedal is released, the vehicle accelerates. occurs momentarily, and driving performance deteriorates. In particular, driving performance deteriorates significantly during acceleration requests and during warm-up. In view of these conventional problems, it is an object of the present invention to improve the operating performance during the transition period and further during the warm-up period by taking into account the moment of inertia of the engine and CVT.

[Means to solve the problem]

In the present invention, the target engine rotation speed and target output torque are defined as a function of the amount of depression of the accelerator pedal or a signal corresponding thereto, and the speed ratio of the continuously variable transmission provided between the engine and the drive wheels is changed. Feedback control is performed so that the engine rotation speed becomes the target engine rotation speed, and by changing the fuel supply flow rate or air supply flow rate to the intake system, the engine output torque becomes the target output torque. In a vehicle power system that performs feedback control on the engine, means for determining the torque to be absorbed or output due to the moment of inertia of the engine and rotating parts connected thereto, and the sum of the absorbed or output torque and the target output torque or The above object is achieved by including means for setting a corresponding value as a new target output torque for the feedback control.

[Effect]

The operation of the present invention will be explained with reference to FIG. FIG. 1 shows a constant fuel consumption rate line (solid line) and a constant horsepower line (broken line) on the engine rotation speed-engine output torque. In addition, the unit of the equal horsepower line is
PS, the unit of constant fuel consumption rate line is g/PS・h. The dashed-dotted line is the characteristic when the throttle valve is fully open, and is the operating limit of the engine. Line A is a line connecting the points that give the minimum fuel consumption rate for each output horsepower.In the present invention, the required horsepower of the engine is set as a function of the amount of depression of the accelerator pedal. The internal combustion engine is operated such that the engine rotational speed and engine output torque are defined by line A at the required horsepower. During warm-up, the engine operation is controlled according to the B line below the A line, and as a result, the catalyst installed in the exhaust system to purify harmful components in the exhaust gas quickly rises to its activation temperature. When driving performance is important, engine operation is controlled according to line C. In conventional stepped transmission vehicles that do not use CVT, the output horsepower is increased by increasing the output torque in a transient manner, resulting in less response delay. In an engine equipped with a CVT, the output horsepower must be increased due to an increase in engine rotational speed, so the response delay of the CVT has a negative impact on driving performance. Therefore, the engine operation is controlled according to the C line in which there is a margin in the output torque during a transient period, that is, the output torque can be significantly increased during acceleration. The engine rotation speed is controlled by changing the CVT speed ratio, and the engine output torque is controlled by changing the intake system throttle opening. The function is determined on the assumption that as the amount of depression of the accelerator pedal increases, the required horsepower also increases. In the present invention, "torque absorbed or outputted due to the moment of inertia of the engine and rotating parts connected to it" is a specific means for shifting to the C line.
It is designed to reflect the Note that lines A to C in FIG. 1 are shown for convenience in order to explain the effects of the present invention, and the present invention is not restricted to the values of these specific curves.

【Example】

Various CVT mechanisms have been proposed in the past, but here, a belt-driven type shown in FIG. 2, which has a large transmittable torque and is compact, will be explained. In FIG. 2, an output shaft 2 of an internal combustion engine 1 is connected to an input shaft 5 of a CVT 4 via a clutch 3. The input shaft 5 and the output shaft 6 are provided parallel to each other, and the input side fixed disk 7 is connected to the input shaft 5.
The input side movable disk 8 is fitted onto the outer periphery of the input shaft 5 with splines or ball bearings so as to be movable in the axial direction, and the output side fixed disk 9 is fixed to the output shaft 6. 1
0 is fitted onto the outer periphery of the output shaft 6 via a spline or a ball bearing so as to be movable in the axial direction. The pressure-receiving area of the movable disk is set so that input side>output side, and the axial arrangement of the fixed disk and the movable disk is opposite to each other on the input side and output side. The opposing surfaces of the fixed disks 7, 9 and the movable disks 8, 10 are formed into tapered surfaces that extend outward in the radial direction and increase the distance between them, and a belt 11 with a truncated conical cross section is formed on the input side and the output side. can be hung between the discs. Therefore, as the clamping force of the fixed and movable disks changes, the radial contact position of the belt 11 on the disk surface changes continuously.
Belt 11 on the surface of input side disks 7 and 8
When the contact position of the belt 11 moves radially outward, the contact position of the belt 11 on the surfaces of the output side disks 9 and 10 moves radially inward, and the speed ratio e of the CVT 4 (=rotational speed of the output shaft 6/ (rotational speed of the input shaft 5) increases, and in the opposite case e decreases. The power of the output shaft 6 is transmitted to drive wheels (not shown). The torque sensor 15 detects the torque of the input shaft 5 from changes in torsional stress or torsion angle in the input shaft 5.
Therefore, the output torque Te of the internal combustion engine 1 is detected.
The accelerator pedal sensor 16 detects the amount of depression of the accelerator pedal 18 by the driver's foot 17 . The opening degree of the intake throttle of the internal combustion engine 1 is controlled by an electromagnetic throttle actuator 19. Input side and output side rotation angle sensors 20, 21
detect the rotation angles and therefore the rotational speeds of the disks 7 and 10, respectively. The line pressure generation valve 24 controls the line pressure in the oil passage 29 by controlling the amount of oil as a hydraulic medium that is sent from the reservoir 26 via the oil passage 27 by the oil pump 25 and releases to the oil passage 28. Adjust Pl. The hydraulic servo of the output side movable disk 10 is supplied with line pressure Pl via the oil passage 29. The flow rate control valve 30 controls the amount of oil flowing into and out of the input movable disk 8 . In order to maintain the speed ratio e of the CVT 4 constant, the oil passage 33 is disconnected from the line pressure oil passage 31 and the drain oil passage 32 branching from the oil passage 29, that is, in the axial direction of the input side movable disk 8. In order to maintain the position constant and increase the speed ratio e, oil is supplied from the oil passage 31 to the oil passage 33 to increase the clamping force between the input side discs 7 and 8, and the speed ratio e
In order to reduce this, the hydraulic pressure of the hydraulic servo of the movable disk 8 is conducted to the atmosphere through the drain oil passage 32 to reduce the thrust between the input side disks 7 and 8. The oil pressure in the oil passage 33 is line pressure Pl
As shown below, the piston action area of the hydraulic servo of the input side movable disk 8 is the output side movable disk 1.
Since the area of action of the piston of the hydraulic servo 0 is larger than that of the piston, it is possible to make the tightening force of the input side disks 7 and 8 larger than the tightening force of the output side disks 9 and 10. The electronic control unit 38 has D/Ds connected to each other by an address data bus 39.
A (digital/analog) converter 40, input interface 41, A/D (analog/digital)
Converter 42, CPU43, RAM44, ROM45
Contains. The analog outputs of the torque sensor 15, accelerator pedal sensor 16, and oil temperature sensor 46 of the oil reservoir 26 are sent to the A/D converter 42, and the pulses of the rotation angle sensors 20 and 21 and the signal of the sporty switch 47 are It is sent to the input interface 41. Outputs to the electromagnetic actuator 19, flow rate control valve 30, and line pressure generation valve 24 are output from a D/A converter 40 to amplifiers 49 and 5, respectively.
0,51. FIG. 3 shows the relationship between the input voltage of the amplifier 49 for the throttle actuator 19 and the output current. Figure 4 shows the throttle actuator 19.
The relationship between input current and intake system throttle opening is shown. Therefore, the throttle opening increases in proportion to the input voltage of the amplifier 49. FIG. 5 shows the relationship between the input voltage and output current of the amplifier 50 for the flow control valve 30, and FIG. 6 shows the relationship between the input current of the flow control valve 30 and the flow rate to the input side hydraulic servo of the CVT 4. It shows. Therefore, the speed ratio e is proportional to a change in the input current of the amplifier 50. 7 shows the relationship between the input voltage and the output voltage of the amplifier 51 for the line pressure generating valve 24, and FIG. 8 shows the relationship between the input voltage and the output voltage of the amplifier 51 for the line pressure generating valve 24.
4 shows the relationship between input current and line pressure Pl. Therefore, line pressure Pl changes linearly with changes in the input voltage of amplifier 51. Line pressure Pl
is controlled to be the minimum value that can ensure torque transmission in the CVT 4. Note that even if the input current to the line pressure generation valve 24 is 0, the line pressure
Since Pl is maintained at Pl1 (Pl1≠0), even if a disconnection occurs or a failure occurs in the electronic control unit 38, a predetermined hydraulic pressure is supplied to the hydraulic servos of the movable disks 8 and 10.
The minimum torque transmission in CVT4 is ensured. FIG. 9 is a block diagram of an embodiment of the invention. Block 55 determines the amount of acceleration pedal depression Xacc
is converted to the required horsepower PS′. The required horsepower PS′ is
It increases with the increase in the amount of pedal stroke Xacc.
It is set as an Xacc function. Block 5
6, the required horsepower PS' is the engine's target rotational speed N',
That is, the target rotational speed Nin′ of the input shaft 5 (N′=Nin′)
is converted to Required horsepower PS′ and target rotation speed
The relationship with Nin' is A, B, or C in Figure 1.
This is indicated by a line. Which function is selected from among the functions Fa, Fb, and Fc based on the A, B, and C lines, respectively, is determined by the temperature Toil of the hydraulic medium used in the hydraulic servo of the CVT4, and by the driver in order to increase acceleration. It is determined by the operating state of the sporty switch in the driver's cab, which is operated by . When the oil temperature Toil is above the predetermined value a and the sporty switch is off, that is, during steady driving after warming up, Fa is selected to minimize the fuel efficiency and the oil temperature Toil is set to the predetermined value. If it is less than a,
That is, during warm-up, Fb is selected and the catalyst in the catalytic converter is quickly raised to the activation temperature, and if the sporty switch is on,
Fc is selected to improve acceleration performance. Furthermore,
If the CVT4 oil temperature Toil is low, the viscosity of the hydraulic medium will increase, the flow rate of the hydraulic medium sent to the CVT4 will decrease, and there is a risk that the driving performance will deteriorate.
Deterioration of driving performance can be prevented by selecting Fb. In block 57, the target rotational speed
The deviation Nin′−Nin between Nin′ and the actual rotational speed Nin is determined. The deviation Nin'-Nin is amplified to K (Nin'-Nin) by the feedback gain 58, and then sent to the flow control valve 30 via the flow control valve amplifier 50, so that the speed ratio e of the CVT 4 is be changed. From equation (2) above, Tout/Te=1-J・N〓e/Te...(3) Therefore, in order to improve driving performance, a predetermined amount of
In order to ensure Tout/Te, the engine rotation acceleration N〓e (=N〓in) should be controlled so as to change inversely to Tout/Te. Therefore, in the present invention, the feedback gain K in the feedback gain 58 is determined by the following equation. K=-k(1-J・N〓e/Te)...(4) However, k is a positive number and is a function of the driving state of the vehicle. The reduction in N〓e is achieved by slowing down the time change in the speed ratio e in the CVT 4. The block 62 receives the input side rotational speed Nin of the CVT 4 sent via the differentiator 63, that is, Nin
and the output torque Te of the engine 1, K is calculated according to equation (4). Let k be a function of the oil temperature Toil of the CVT 4, which changes in relation to the warm-up state, and the operating state SW of the sporty switch. During warm-up and while the sporty switch is on, k is decreased to improve driving performance. In block 67, the required horsepower PS' and the input side rotational speed Nin of CVT4 are calculated.
The steady state required output torque T1 as a function f′ of
Calculate. T1=b・PS'/Nin...(5) However, b is a constant. In block 68, CVT4
Calculate the loss torque T2 in the transient state absorbed by the moment of inertia J as a function f'' of the input-side rotational acceleration N〓in.T2=J・N〓in...(6) In block 69, the target output Torque Te′
Assuming that Te′=T1+T2, target output torque Te′ and engine 1
Find the deviation Te′−Te from the actual output torque Te,
Te'-Te is sent to the throttle actuator amplifier 49 via the feedback gain 70. FIG. 10 is a flowchart of a program according to the block diagram of FIG. In step 75, from the input signal from the accelerator pedal sensor 16,
Calculate the required horsepower PS′. In step 76, CVT
Determine whether or not the oil temperature Toil in step 4 is equal to or higher than a predetermined value a,
If Toil≧a, proceed to step 78; if Toil<a, proceed to step 77. In step 77, during warm-up, the target rotation speed is determined based on the above-mentioned function Fb.
Calculate Nin' and substitute k1 for k. step 78
Then, it is determined whether the sporty switch 47 is on or not, and if it is on, the process proceeds to step 80, and if it is off, the process proceeds to step 79. In step 79, the target rotational speed Nin′ is calculated based on the above-mentioned function Fc,
Assign k2 to k. In step 80, the target rotational speed Nin is calculated based on the above-mentioned function Fa, and k3
Assign k to k. Note that k3>k1>k2. In step 81, k is corrected in relation to the rate of change in the throttle opening or accelerator pedal depression (the amount of change in the throttle opening or accelerator pedal depression per unit time). The more rapidly the accelerator pedal 18 is depressed, the smaller the time change in the speed ratio of the CVT 4 is made to increase the output torque of the engine. In step 84, the feedback gain K
is calculated based on equation (4) above. In step 85, the input voltage Vin of the flow control valve amplifier 50 is
Calculated from the following formula. Vin=K(Nin′−Nin) ……(7) In step 86, the required torque T1 in steady state
is calculated from equation (5) above. In step 87, the transient loss torque T2 absorbed due to the moment of inertia J is calculated from the above-mentioned equation (6). In step 88, T1+T2 is set as target output torque Te'.
In step 89, the input voltage Vth of the throttle actuator amplifier 49 is calculated from the following equation. Vth=K′(Te′−Te) ……(8) However, K′ is a constant. After performing step 89,
Return to step 76.

【Effect of the invention】

As described above, according to the present invention, the speed ratio is controlled steplessly using the CVT, and the time change in the speed ratio of the CVT is controlled in consideration of the torque absorbed due to the moment of inertia, or Since the engine output torque is controlled to compensate for the torque absorbed due to the moment of inertia, fuel efficiency and driving performance can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing equal horsepower lines and equal fuel consumption rate lines on the coordinate system of engine rotational speed and output torque. FIG. 2 is a configuration diagram of a vehicle power plant to which the present invention is applied. Figure 3 is a diagram showing the input/output characteristics of the throttle actuator amplifier, Figure 4 is a diagram showing the relationship between the throttle actuator input and throttle opening, and Figure 5 is a diagram showing the relationship between the throttle actuator input and throttle opening. Figure 6 shows the input/output characteristics of the valve amplifier. Figure 6 shows the relationship between the input of the flow control valve and the CVT speed ratio. Figure 7 shows the input/output characteristics of the line pressure generating valve amplifier. 8 is a diagram showing the relationship between the input of the line pressure generation valve and the line pressure, FIG. 9 is a block diagram of an embodiment of the present invention, and FIG. 10 is a block diagram of FIG. 9. This is a flowchart of the program to follow. 1... Internal combustion engine, 4... CVT, 15... Torque sensor, 18... Accelerator pedal, 19... Throttle actuator, 20... Rotation angle sensor, 3
0...Flow control valve, 38...Electronic control device, 46
...Oil temperature sensor, 47...Sporty switch.

Claims (1)

[Claims] 1. A target engine rotation speed and a target output torque are defined as a function of the amount of depression of the accelerator pedal or a signal corresponding thereto, and the speed of a continuously variable transmission provided between the engine and the driving wheels is defined. By changing the ratio, feedback control is performed so that the engine rotation speed becomes the target rotation speed, and by changing the fuel supply flow rate or air supply flow rate to the intake system, the output torque of the engine is adjusted to the target output torque. A vehicle power system that performs feedback control so that A vehicle power plant comprising: means for setting the sum or a value corresponding thereto as a new target output torque for the feedback control.