Vehicle control system

Abstract

The system appropriately controls the clutch to a slipping state to suppress vibrations, depending on the vehicle's operating or driving conditions. [Solution] A vehicle control device that controls the clutch to a slipping state when a predetermined condition is met, including the operating point of the internal combustion engine being within a predetermined region, wherein the controller 9 comprises a tilt determination unit 9b that determines the tilt of the road surface on which the vehicle is traveling in the longitudinal direction, and a vibration reduction region setting unit 9d that sets a region, the vibration reduction region setting unit 9d sets a flat road region Af when no tilt is determined, a downhill road region Ad that is narrower than the flat road region when a downhill tilt is determined, and an uphill road region Au that is wider than the flat road region Af when an uphill tilt is determined, and the condition is met when the operating point is within the flat road region, the downhill road region, or the uphill road region.

Description

Technical Field

[0001] The present invention relates to a device for controlling the transmitted torque in order to reduce vibrations in a vehicle equipped with an internal combustion engine and a transmission.

Background Art

[0002] An internal combustion engine mounted on a vehicle outputs mechanical power by intermittent combustion of fuel, so its output torque inevitably vibrates. In addition, the transmission system and the vehicle body from the internal combustion engine, which is the driving power source, to the driving wheels not only have inevitable backlash but also elastically deform, so the vehicle as a whole constitutes a vibration system. Therefore, when the vehicle is running, resonance of the transmission system may occur with the torque fluctuation output by the internal combustion engine as the excitation source. A device configured to prevent deterioration of NV characteristics due to such resonance is described in Patent Document 1.

[0003] The device described in Patent Document 1 is a control device for a vehicle having a torque converter with a lock-up clutch. When conditions including that the lock-up clutch is in an engaged state, a predetermined gear stage is established in the transmission, and an operating point determined according to the engine speed and load belongs to a predetermined region are satisfied, and resonance is determined, the lock-up clutch is controlled to a slip state. In a state where the lock-up clutch is engaged, resonance caused by the vibration of the torque output by the internal combustion engine as the excitation source is sometimes referred to as a grab field. In the control device described in Patent Document 1, by controlling the lock-up clutch to a slipping state, a rotational speed difference occurs between the internal combustion engine and the transmission mechanism or the transmission mechanism, and the torque fluctuation is absorbed by the slip of the lock-up clutch, so the grab field is suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] In the control device described in Patent Document 1, the operating range for controlling the lock-up clutch to a slipping state is set for each gear shift. However, depending on the vehicle's driving state, vibrations due to resonance such as grab feel may be difficult to perceive, or conversely, even small vibrations may be perceived and cause discomfort. The device described in Patent Document 1 does not consider conditions related to the quality of NV characteristics other than those exemplified in Patent Document 1. Therefore, in the device described in Patent Document 1, there was a possibility that the timing of controlling the lock-up clutch to a slipping state would be delayed, worsening the vibrations, or conversely, that the lock-up clutch would be unnecessarily controlled to a slipping state.

[0006] The present invention has been made in view of the above technical problems, and aims to provide a control device that can appropriately perform control to suppress vibration by controlling the clutch to a slipping state according to the driving state or running state of the vehicle. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a vehicle control device that includes an internal combustion engine and a transmission having a clutch capable of transmitting torque in a slipping state, and controls the clutch to a slipping state when a predetermined condition is met, including the operating point of the internal combustion engine, which is determined by rotational speed and load, is within a predetermined region, the device further comprising a controller for controlling the clutch, the controller comprising a slope determination unit for determining the inclination of the road surface on which the vehicle is traveling in the longitudinal direction, and a vibration reduction region setting unit for setting the region, the vibration reduction region setting unit for setting a flat road region when the inclination is not determined, a downhill road region that is narrower than the flat road region when a downhill slope is determined, and an uphill road region that is wider than the flat road region when an uphill slope is determined, and the condition is met when the operating point is within any of the flat road region, the downhill road region, or the uphill road region. [Effects of the Invention]

[0008] According to the control device of the present invention, when the acceleration is lower due to driving uphill than when driving on a flat road, the operating range of the internal combustion engine in which the clutch is controlled to slip is widened. As a result, the clutch is controlled to slip at low output torque or torque fluctuations where vibrations are easily perceived, thereby preventing or suppressing the worsening of vibrations. Furthermore, when the acceleration is higher due to driving downhill than when driving on a flat road, the operating range of the internal combustion engine in which the clutch is controlled to slip is narrowed. As a result, in the range set for flat roads, the clutch is not controlled to slip but maintained in an engaged state on the lower output torque or torque fluctuation side. In other words, control that unnecessarily slips the clutch in a state where the worsening of vibrations is not perceived can be avoided. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing the powertrain (transmission system) of a vehicle in an embodiment of the present invention. [Figure 2]This is a block diagram illustrating the functional configuration of the controller. [Figure 3] (A) is a diagram showing the relationship between engine torque and engine torque fluctuation at a specific engine speed, (B) is a diagram showing the relationship between engine torque at a specific engine speed and the range in which the driver perceives grab feel, and (C) is a diagram that superimposes these diagrams. [Figure 4] (A) is a diagram similar to (C) in Figure 3, showing the case where the boundary line changes upward, and (B) is a diagram similar to (C) in Figure 3, showing the case where the boundary line changes downward. [Modes for carrying out the invention]

[0010] Next, embodiments of the present invention will be described with reference to the attached drawings. Note that the embodiments described below are merely examples of how the present invention can be implemented and do not limit the invention.

[0011] Figure 1 schematically shows the powertrain (transmission system) of a vehicle 1 in an embodiment of the present invention. It is equipped with an internal combustion engine 2 as a driving force source. The internal combustion engine 2 may be a gasoline engine or a diesel engine, and outputs mechanical power by intermittently burning fuel. Therefore, the output torque of the internal combustion engine (hereinafter referred to as the engine) 2 inevitably fluctuates (vibrates).

[0012] A transmission 3 is connected to the output side of engine 2. Transmission 3 comprises a torque converter 5 with a lock-up clutch 4 and a gear transmission mechanism 6. The torque converter 5, as in conventionally known systems, is configured to send pressurized fluid from a pump impeller to a turbine runner to rotate the turbine runner, and to change the direction of fluid flow from the turbine runner back to the pump impeller via a stator supported by a one-way clutch. The lock-up clutch 4 is provided between the pump impeller and the turbine runner and transmits torque without fluid. The lock-up clutch 4 is controlled by hydraulic pressure to be engaged and disengaged, and is also controlled to be in a slipping state (or flex lock-up state) that transmits torque with slippage. The gear transmission mechanism 6 is mainly composed of multiple gear pairs or multiple sets of planetary gear mechanisms and is configured to set multiple gear ratios (gear stages) according to the engagement and disengagement states of engagement mechanisms such as clutches and brakes. The output shaft 7 of the transmission 3 is connected to the differential gear 8, which is the final reduction gear, and the drive torque is transmitted from the differential gear 8 to the left and right drive wheels.

[0013] A controller 9 for controlling the lock-up clutch 4 is provided in the vehicle 1. The controller 9 is an electronic control device mainly composed of a microcomputer, which performs calculations using input data and pre-stored data, and outputs the result of the calculations as a control command signal that controls the lock-up clutch 4 to the engaged state, released state, and slip state. Examples of input data include the intake air volume Qa of the engine 2 detected by an airflow meter (not shown), engine speed Ne, the rotational speed Nt of the turbine runner in the lock-up clutch 4, the output rotational speed No, which is the rotational speed of the output shaft 7, the accelerator opening Acc, which is the depression angle of the accelerator pedal (not shown), the vehicle speed V, and the gear position γ output by a gear position sensor (not shown), which are input to the controller 9. Examples of pre-stored data include a map that defines the correction coefficients described later, an engine speed threshold, an engine torque threshold, and a map that defines the region for the engine operating point, which will be described later, which are pre-stored in the controller 9.

[0014] The controller 9 is configured to perform control that puts the lock-up clutch 4 into a slipping state in order to suppress resonance caused by fluctuations in engine torque. The functional configuration for this control is shown in a block diagram in Figure 2. The controller 9 is equipped with an acceleration detection unit 9a. The acceleration detection unit 9a detects acceleration, for example, by differentiating the input vehicle speed V with respect to time. The controller 9 is equipped with a slope determination unit 9b that estimates the slope (angle of inclination) of the road based on the detected acceleration and the input accelerator opening Acc. The driving force of the vehicle 1 can be determined based on the accelerator opening Acc, and the acceleration on a flat road without inclination can be determined from that driving force and the weight of the vehicle. The acceleration obtained by differentiating the vehicle speed V is affected by the gravitational acceleration due to the inclination of the vehicle 1 in the longitudinal direction, so the slope angle of the road can be determined from the difference between the acceleration obtained by differentiating the vehicle speed V and the acceleration obtained from the accelerator opening Acc. The slope determination unit 9b estimates the slope (angle of inclination) of the road in this way.

[0015] A correction coefficient calculation unit 9c is provided in the controller 9 to determine a correction coefficient kx for engine speed Ne and a correction coefficient ky for engine torque Te based on the estimated gradient. These correction coefficients kx and ky are coefficients used to adjust the operating range of the engine 2, defined by rotational speed and torque, and are coefficients determined in the design according to the estimated gradient. Figure 2 shows an example of a map of coefficients determined based on the gradient. In this example, when the gradient is "0", the correction coefficients kx and ky are set to "1", the larger the uphill gradient, the smaller the correction coefficients kx and ky are set to be in the range greater than "0", and the larger the downhill gradient, the larger the correction coefficients kx and ky are set to be.

[0016] A vibration reduction region setting unit 9d is provided in the controller 9 that uses these correction coefficients kx and ky to set the region of the engine 2's operating point. The region is the region of the operating point where grab feel is expected to occur, and the region where resonance occurs when driving on a level, flat road with the lock-up clutch 4 fully engaged is defined as the flat road region Af, based on experiments and simulations. The above correction coefficients kx and ky are coefficients for widening or narrowing the flat road region Af, and the correction is performed by dividing the range of engine speed Ne in the flat road region Af (difference between the maximum and minimum values) by the correction coefficient kx for engine speed Ne, and by dividing the range of engine torque Te in the flat road region Af (difference between the maximum and minimum values) by the correction coefficient ky for engine torque Te. Therefore, for uphill roads, each correction coefficient kx and ky will be a value less than "1", so the region on uphill roads (uphill road region) Au will be wider than the flat road region Af. Furthermore, for downhill roads, the correction coefficients kx and ky become values ​​greater than "1," so the downhill road region (Ad) becomes narrower than the flat road region (Af). The vibration reduction region setting unit 9d is input with engine speed threshold and engine torque threshold values. The engine speed Ne and engine torque Te used to set each region Af, Au, and Ad are within the range of their respective thresholds.

[0017] Here, we will explain the technical basis for changing the vibration reduction region, that is, the region in which so-called vibration reduction control is performed, which changes the lock-up clutch 4 from a fully engaged state to a slipping state, according to the slope (angle of inclination) of the road surface. Figure 3(A) shows the relationship between engine torque Te and engine torque fluctuation at a specific engine speed. When the engine torque Te is small, the engine torque fluctuation remains small, and when the engine torque Te increases beyond a predetermined value, the engine torque fluctuation increases accordingly. After the engine torque Te becomes large enough, the increase in engine torque fluctuation becomes gradual. The engine torque fluctuation is approximately equal to or proportional to the grab feel, which is the resonance when driving with the lock-up clutch 4 engaged.

[0018] Furthermore, Figure 3(B) shows the relationship between engine torque Te at a specific engine speed and the region in which the driver perceives grab feel. Note that Figure 3(B) shows an example of driving on a horizontal plane, and therefore the engine torque Te is equal to or proportional to the acceleration when driving on a horizontal plane. In Figure 3(B), the dashed line indicates the boundary line (criterion) C, and above the dashed line is the region in which grab feel is perceived and it is preferable to implement control to suppress vibration. Conversely, below the dashed line is the region in which grab feel is not perceived, or grab feel is not significant enough to be a problem, and control to suppress vibration is not particularly necessary.

[0019] Figure 3(C) shows a superimposed view of Figures 3(A) and 3(B). The region in Figure 3(C) where the grab feel value falls within the range where the grab feel is easily perceived by the driver is indicated by hatching. This region is between the engine torque indicated by Te1 and the engine torque indicated by Te2. Therefore, the region requiring vibration suppression control at a specific engine speed is determined as the engine torque region.

[0020] Incidentally, whether the grab feel is good or bad, that is, whether it is preferable to perform vibration suppression control, is determined by the sensitivity of the rider to vibration. As a general tendency, when the vehicle acceleration is large, the sensitivity of the grab feel becomes lower compared to when the acceleration is small, and the degree of tolerance for the grab feel increases. If this is represented by the boundary line C explained in (B) of FIG. 3, it is as shown in FIGS. 4(A) and (B). FIG. 4(A) shows an example where the acceleration increases due to the addition of gravitational acceleration on a downhill road. The boundary line C has a larger intercept on the vertical axis indicating engine torque fluctuations and a smaller slope of the line. As a result, the minimum value of the engine torque that defines the region where the torque fluctuation value exceeds the boundary line C increases from Te1 to Te3. That is, the region where it is necessary to perform vibration suppression control becomes narrower. On the other hand, on an uphill road, as shown in FIG. 4(B), the boundary line C has a smaller intercept on the vertical axis indicating engine torque fluctuations and a larger slope of the line. As a result, the minimum value of the engine torque that defines the region where the torque fluctuation value exceeds the boundary line C decreases from Te1 to Te4. That is, the region where it is necessary to perform vibration suppression control becomes wider.

[0021] The examples shown in FIGS. 3 and 4 above are examples when the engine speed is fixed at a predetermined speed. However, the grab feel also changes depending on the engine speed. As a general tendency, the higher the engine speed, the larger the value of the grab feel. Therefore, as described in the explanation of the vibration reduction region setting unit 9d shown in FIG. 2, the region for the operating point of the engine 2 that performs control to suppress the grab feel is represented by a two-dimensional map of the engine speed and the engine torque. And that region becomes narrower than the flat road region Af when the acceleration increases on a downhill road, and conversely becomes wider than the flat road region Af when the acceleration decreases on an uphill road.

[0022] In the control device according to the embodiment of the present invention, control is executed to put the lock-up clutch 4 into a slipping state based on the region for the operating point set by the vibration reduction region setting unit 9d shown in FIG. 2. That is, the operating point of the engine 2 is detected based on the engine load that can be represented by the engine speed Ne and the accelerator opening Acc, and when the detected operating point falls within any of the regions Af, Ad, Au set according to the driving state, control is executed to switch the lock-up clutch 4 from the fully engaged state to the slipping state, that is, vibration suppression control. As a result, it is possible to prevent or suppress the situation where the control to put the lock-up clutch 4 into the slipping state is delayed and the vibration deteriorates. In addition, it is possible to avoid or suppress a situation where the lock-up clutch 4 is released despite the fact that the vibration does not deteriorate, and the driving torque or the engine speed changes unintentionally.

[0023] Note that the present invention is not limited to the above-described embodiment. The downhill road region and the uphill road region only need to be different from the flat road region, and may be set independently based on the detected predetermined parameters without setting by correcting the flat road region. Further, when setting the downhill road region or the uphill road region by correcting the flat road region, the correction method may be a correction other than the correction described in the above embodiment. For example, the lower limit value defining the flat road region may be corrected to be larger or smaller by a correction coefficient. Therefore, the correction coefficient is not limited to the coefficient described with reference to FIG. 2. Further, in the present invention, instead of obtaining the inclination angle of the traveling road surface from the acceleration based on the accelerator opening and the vehicle speed, it may be obtained as road information by a navigation system. Further, the control to put the lock-up clutch into the slipping state may be executed for a predetermined time, and the time may be a short time of about several seconds. Furthermore, in the present invention, in addition to the engine operating point falling within any region, the lock-up clutch may be controlled to be in the slipping state on the condition that a grab field is detected. And the clutch in the present invention may be a friction clutch in a gear transmission mechanism in addition to the lock-up clutch.

Description of Reference Numerals

[0024] 1 vehicle 2. Internal combustion engine 3. Transmission 4. Lock-up clutch 5 Torque converter 6. Gear transmission mechanism 7 Output shaft 8 Differential gear 9 Controllers 9a Acceleration detection unit 9b Inclination determination section 9c Correction coefficient calculation unit 9d Vibration reduction area setting section γ gear shift Accelerator opening Af flat road area C border Ne Engine speed No. Output rotation speed Nt (Turbine Runner) Rotational Speed Qa Intake air volume Te, Te1, Te2 Engine Torque V Vehicle speed kx, ky correction coefficient

Claims

[Claim 1] A vehicle control device comprising an internal combustion engine and a transmission having a clutch capable of transmitting torque in a slipping state, wherein the device controls the clutch to a slipping state when predetermined conditions are met, including the fact that the operating point of the internal combustion engine, determined by rotational speed and load, falls within a predetermined range, The system includes a controller that controls the clutch, The aforementioned controller, An inclination determination unit that determines the inclination of the road surface in the longitudinal direction on which the vehicle is traveling, The system includes a vibration reduction region setting unit for setting the aforementioned region, The vibration reduction area setting unit sets a flat road area when no slope is detected, a downhill road area that is narrower than the flat road area when a downhill slope is detected, and an uphill road area that is wider than the flat road area when an uphill slope is detected. The condition is met when the driving point enters any of the flat road region, the downhill road region, or the uphill road region. A vehicle control device characterized by the following features.

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