Vehicle control system

Abstract

To appropriately execute speed change control even in a case where a vehicle mounted with a belt type continuously variable transmission travels at an extremely low speed, with a speed change ratio difficult to be calculated.SOLUTION: A vehicular control apparatus performs hydraulic controls of respective primary sheave pressure and secondary sheave pressure, and performs belt narrow pressure control and speed change control of a belt-type stepless transmission 3. The apparatus performs: speed change control by executing feedback control to calculate the primary sheave pressure for causing an actual speed change ratio to track a target transmission ratio or feedforward control to calculate primary sheave pressure in balance with the secondary sheave pressure on the basis of the target speed change ratio; and calculating, in a case where a vehicle Ve travels at an extreme low speed making it difficult to calculate the actual speed change ratio, with an oil temperature very high to cause ejection performance of the oil pump to deteriorate, primary sheave pressure from an ejection volume of oil instead of the secondary sheave pressure through the feedforward control, thus executing speed change control (step S10).SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a control device for a vehicle equipped with a continuously variable transmission, and more particularly to a control device for a vehicle that hydraulically controls the operation of a belt-type continuously variable transmission (belt squeezing pressure control and shift control).

Background Art

[0002] Patent Document 1 describes a control device for a belt-type continuously variable transmission aimed at suppressing the occurrence of belt slip and maintaining the maximum speed ratio. The belt-type continuously variable transmission described in this Patent Document 1 includes a primary pulley and a secondary pulley around which a transmission belt is wound, an oil pump, and a hydraulic control device. The oil pump is driven by the output torque of the engine to discharge hydraulic oil. The hydraulic control device applies the hydraulic oil discharged from the oil pump to the primary movable sheave of the primary pulley and the secondary movable sheave of the secondary pulley. The control device for the belt-type continuously variable transmission controls the primary thrust for moving the primary movable sheave and the secondary thrust for moving the secondary movable sheave, respectively. And the control device for the belt-type continuously variable transmission described in this Patent Document 1 reduces the primary target pressure when the secondary target pressure is smaller than the discharge capacity of the oil pump compared to the case where the secondary target pressure is larger than the discharge capacity of the oil pump when the maximum speed ratio is required.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described in Patent Document 1 above, a belt-type continuously variable transmission has two pulleys around which the transmission belt is wound, namely a primary pulley and a secondary pulley. By controlling the thrust (or sheave pressure) that moves the movable sheaves of the primary and secondary pulleys in the direction of the rotation axis, belt narrowing pressure control and gear shift control of the belt-type continuously variable transmission are performed. For example, by hydraulically controlling the sheave pressure of the secondary pulley, belt narrowing pressure control is performed to prevent belt slippage. Conversely, by hydraulically controlling the sheave pressure of the primary pulley, gear shift control is performed to change the gear ratio by changing the diameter around which the transmission belt is wound.

[0005] Typically, gear shifting in a belt-type continuously variable transmission (CVT) is performed using feedback control, or a combination of feedback and feedforward control. For example, to make the actual gear ratio (actual gear ratio) of the belt-type CVT track the target gear ratio, the upshift or downshift amount is calculated using feedback control. Then, gear shifting is performed by hydraulically controlling the sheave pressure of the primary pulley based on the calculated upshift or downshift amount. However, in situations where the vehicle is traveling at extremely low speeds, the rotational speeds of the input and output shafts of the belt-type CVT cannot be properly detected, and the accurate gear ratio cannot be calculated. In such cases, gear shifting is performed using only feedforward control without using feedback control.

[0006] In the feedforward control-based gear shift control described above, the secondary pulley sheave pressure (secondary sheave pressure) to prevent belt slippage and the primary pulley sheave pressure (primary sheave pressure) to achieve a gear ratio that follows the target gear ratio are instructed to maintain a balance with each other. That is, the feedforward control calculates the instructed pressure (target value) for the primary sheave pressure and the instructed pressure (target value) for the secondary sheave pressure, respectively. If the actual pressure of the secondary sheave pressure (detected by the hydraulic sensor) is used to calculate the instructed pressure for the primary sheave pressure, hydraulic vibration (hydraulic pulsation) may cause hunting in the gear shift control. Therefore, the instructed pressure for the primary sheave pressure is calculated using the instructed pressure for the secondary sheave pressure via feedforward control. However, in situations such as when the oil temperature of a belt-type continuously variable transmission is high and the discharge performance of the oil pump that generates each sheave pressure decreases, the balance between the primary sheave pressure and the secondary sheave pressure (actual pressure) will be disrupted towards the upshift side. In this case, feedback control cannot make the actual gear ratio follow the target gear ratio, so it is not possible to immediately correct the state in which the actual gear ratio deviates from the target gear ratio. As a result, the unbalanced state on the upshift side continues as described above, and the belt-type continuously variable transmission continues to gradually upshift. Consequently, there is a risk that the vehicle's driving force will become insufficient.

[0007] This invention was conceived in response to the above-mentioned technical problems, and aims to provide a vehicle control device that can appropriately control the shifting of a belt-type continuously variable transmission (CVT) even when it becomes difficult to calculate the gear ratio when the vehicle equipped with the CVT is traveling at extremely low speeds. [Means for solving the problem]

[0008] To achieve the above objective, this invention provides a vehicle control device comprising an engine, a belt-type continuously variable transmission having a primary pulley and a secondary pulley around which a transmission belt is wound, which transmits the torque output by the engine to the drive wheels, and an oil pump driven by the engine, wherein the oil pump uses the hydraulic pressure generated to hydraulically control the primary sheave pressure supplied to the primary pulley and the secondary sheave pressure supplied to the secondary pulley, respectively, to perform belt narrow pressure control and shift control of the belt-type continuously variable transmission, wherein the device comprises a controller for controlling the belt-type continuously variable transmission, the controller calculates the target shift ratio and the actual shift ratio of the belt-type continuously variable transmission, respectively, and The gear shift control is performed by at least one of the following: feedback control, which calculates the primary sheave pressure to make the actual gear ratio follow the target gear ratio; or feedforward control, which calculates the primary sheave pressure that balances with the secondary sheave pressure based on the target gear ratio. Furthermore, when the vehicle is traveling at or below a predetermined vehicle speed threshold where it becomes difficult to calculate the actual gear ratio, and the temperature of the oil discharged by the oil pump is higher than a predetermined oil temperature threshold where the discharge performance of the oil pump deteriorates, the primary sheave pressure is calculated from the oil discharge amount instead of the secondary sheave pressure using the feedforward control, and the gear shift control is performed. [Effects of the Invention]

[0012] The vehicle control device of this invention controls a vehicle equipped with a belt-type continuously variable transmission (CVT) and performs belt pressure control and gear shift control of the CVT. Normally, gear shift control of a belt-type CVT is performed using feedback control, or a combination of feedback control and feedforward control. However, in situations where the vehicle is traveling at extremely low speeds, such as when parking a vehicle or making turns or maneuvers in a narrow space, the rotational speeds of the input and output shafts of the belt-type CVT cannot be properly detected. Therefore, in such cases, gear shift control is performed using only feedforward control without using feedback control. Feedforward control allows gear shift control to be performed even when the rotational speed cannot be detected and the gear ratio of the belt-type CVT cannot be accurately calculated. However, when performing gear shift control using feedforward control, if, for example, the oil in the belt-type continuously variable transmission becomes hot and the discharge performance of the oil pump decreases, the actual secondary sheave pressure will be insufficient compared to the indicated pressure for the secondary sheave pressure, causing the balance between the primary and secondary sheave pressures to be disrupted towards the upshift side. In such cases, the belt-type continuously variable transmission will effectively continue upshifting, which raises concerns about insufficient driving force for the vehicle. Therefore, in the vehicle control device of this invention, when the vehicle is traveling at a very low speed and the oil temperature of the belt-type continuously variable transmission is high, the primary sheave pressure is calculated based on the discharge amount of the oil pump and gear shift control is performed. As a result, even in situations where there is a discrepancy between the indicated pressure and the actual pressure of the secondary sheave pressure, the feedforward control balances the primary and secondary sheave pressures, allowing for appropriate gear shift control of the belt-type continuously variable transmission.

[0013] Furthermore, in the vehicle control device of this invention, as described above, when the vehicle is traveling at a very low speed, the oil temperature of the belt-type continuously variable transmission is high, and the engine speed is below the rotational speed threshold, the primary sheave pressure is calculated based on the discharge amount of the oil pump. When the engine speed is above the rotational speed threshold, the discharge amount (increase or decrease) of the oil pump does not adversely affect the feedforward control as described above. On the other hand, when the engine speed falls below the rotational speed threshold, the amount of oil discharged by the oil pump decreases, and there is a concern that a situation may arise where the indicated pressure and the actual pressure of the secondary sheave pressure diverge, as described above. Therefore, in the vehicle control device of this invention, when the engine speed falls below the rotational speed threshold and the discharge amount of the oil pump decreases, the primary sheave pressure is calculated based on the discharge amount of the oil pump and shift control is executed. Thus, shift control of the belt-type continuously variable transmission can be reliably executed.

[0014] Furthermore, in the vehicle control device of this invention, when the vehicle's accelerator opening (or the amount operated by the accelerator device) exceeds the accelerator opening threshold, the primary sheave pressure is calculated from the secondary sheave pressure indicator (i.e., the hydraulic command value), and shift control is performed. When the accelerator opening exceeds the accelerator opening threshold and the vehicle generates a large driving force, the discharge amount of the oil pump decreases, and if the actual pressure of the secondary sheave pressure drops, there is a risk of belt slippage occurring in the belt-type continuously variable transmission. Belt slippage can damage the belt-type continuously variable transmission. Therefore, in the vehicle control device of this invention, when the accelerator opening exceeds the accelerator opening threshold, priority is given to protecting the belt-type continuously variable transmission, and the primary sheave pressure is calculated from the secondary sheave pressure indicator, and shift control is performed. Thus, damage due to belt slippage can be prevented, and the belt-type continuously variable transmission can be reliably protected.

[0015] Furthermore, the vehicle control device of this invention calculates the primary sheave pressure from the secondary sheave pressure indicator (i.e., hydraulic command value) and performs gear shift control when the gradient of the road on which the vehicle is traveling or located exceeds a gradient threshold. When traveling on an uphill road with a gradient of a gradient threshold or higher, a greater driving force is required compared to traveling on a flat road. In such situations, if the discharge amount of the oil pump decreases and the actual pressure of the secondary sheave pressure drops, there is a risk of belt slippage occurring in the belt-type continuously variable transmission. Belt slippage can damage the belt-type continuously variable transmission. Therefore, when the road gradient exceeds a gradient threshold, the vehicle control device of this invention prioritizes protecting the belt-type continuously variable transmission by calculating the primary sheave pressure from the secondary sheave pressure indicator and performing gear shift control. Thus, damage due to belt slippage can be prevented, and the belt-type continuously variable transmission can be reliably protected.

[0016] Therefore, according to the vehicle control device of this invention, even when it becomes difficult to calculate the gear ratio when a vehicle equipped with a belt-type continuously variable transmission is traveling at an extremely low speed, the vehicle control device can appropriately perform gear shift control of the belt-type continuously variable transmission and generate appropriate driving force to drive the vehicle. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is a block diagram showing a schematic configuration of a vehicle equipped with a belt-type continuously variable transmission that is the target of control in this invention, including a gear train diagram and a schematic control system. [Figure 2] Figure 2 is a time chart illustrating the shift control mechanism of a conventional belt-type continuously variable transmission and the challenges associated with that shift control. [Figure 3] Figure 3 is a flowchart illustrating an example of gear shift control for a belt-type continuously variable transmission performed by the vehicle control device of this invention. [Figure 4]Figure 4 is a time chart illustrating the details of the gear shift control of the belt-type continuously variable transmission shown in the flowchart of Figure 3, and the effects of executing that gear shift control. [Modes for carrying out the invention]

[0018] Embodiments of this invention will be described with reference to the drawings. Note that the embodiments shown below are merely examples of how this invention can be implemented and do not limit the invention.

[0019] The vehicle controlled in this embodiment of the invention uses an engine (internal combustion engine) as a driving force source and is equipped with a belt-type continuously variable transmission that transmits the engine's output torque to the drive shaft and drive wheels. The vehicle control device in this embodiment of the invention performs belt pressure control and gear shift control of the belt-type continuously variable transmission. Figure 1 shows an example of the vehicle controlled in this embodiment of the invention and a belt-type continuously variable transmission.

[0020] The vehicle Ve shown in Figure 1 is equipped with an engine (ENG) 1 as a driving force source. The vehicle Ve is also equipped with a belt-type continuously variable transmission 3 that transmits torque between the engine 1 and the drive wheels 2. Furthermore, it is equipped with a detection unit 4 that detects various data used for controlling the vehicle Ve, and a controller 5 that controls the operation of the vehicle Ve, in particular the belt-type continuously variable transmission 3.

[0021] Engine 1 is an internal combustion engine that generates power by burning fuel, such as a gasoline engine or a diesel engine. Engine 1's output, as well as its operating states such as starting and stopping, are electrically controlled.

[0022] The drive wheel 2 is a wheel that generates the driving force of the vehicle Ve by transmitting the output torque of the engine 1. In the example shown in FIG. 1, the vehicle Ve is envisioned as a front-wheel drive vehicle that uses the front wheels as the drive wheels 2 and generates the driving force with those front wheels. Note that the vehicle Ve in the embodiments of this invention may be a front-wheel drive vehicle (not shown) that uses the rear wheels as the drive wheels 2 and generates the driving force with those rear wheels. Or, it may be a four-wheel drive vehicle (not shown) that distributes the output torque of the engine 1 to the front and rear wheels via a transfer (not shown) and uses the front and rear wheels as the drive wheels 2. Alternatively, it may be a four-wheel drive hybrid vehicle (not shown) that drives either the front or rear wheels with the engine 1 and drives the other of the front or rear wheels with a motor.

[0023] The belt-type continuously variable transmission 3 is, for example, connected to the output side of the engine 1 via a torque converter 6, and transmits the output torque of the engine 1 to the drive wheel 2 side between the engine 1 and the drive wheel 2. At the same time, it changes the rotational speed of the output shaft 1a of the engine 1. And the belt-type continuously variable transmission 3 is a power transmission device that can appropriately and continuously change the ratio of the rotational speed of the output shaft 3b to the rotational speed of the input shaft 3a, that is, the transmission ratio, and the control of changing the transmission ratio, that is, the shift control, is automatically controlled.

[0024] Specifically, the belt-type continuously variable transmission 3 includes, as main components, a primary pulley 7, a secondary pulley 8, and a transmission belt 9 that is wound around the primary pulley 7 and the secondary pulley 8 to perform power transmission. Also, the belt-type continuously variable transmission 3 includes a forward / reverse switching mechanism 10, an oil pump 11, and a hydraulic control device (not shown).

[0025] In the example shown in FIG. 1, the primary pulley 7 is provided on the input shaft 3a side, fixed to the input shaft 3a, and has a fixed sheave 7a that rotates integrally with the input shaft 3a, a movable sheave 7b that rotates integrally with the input shaft 3a and is relatively movable in the axial direction of the input shaft 3a (the left - right direction in FIG. 1), and a hydraulic cylinder 7c that operates the movable sheave 7b. When executing the shift control of the belt - type continuously variable transmission 3, the hydraulic pressure (primary sheave pressure) acting on the movable sheave 7b of the primary pulley 7 is controlled to change the winding diameter of the transmission belt 9.

[0026] In the example shown in FIG. 1, the secondary pulley 8 is provided on the output shaft 3b side, fixed to the output shaft 3b, and has a fixed sheave 8a that rotates integrally with the output shaft 3b, a movable sheave 8b that rotates integrally with the output shaft 3b and is relatively movable in the axial direction of the output shaft 3b (the left - right direction in FIG. 1), and a hydraulic cylinder 8c that operates the movable sheave 8b. When executing the belt - narrow pressure control of the belt - type continuously variable transmission 3, the hydraulic pressure (secondary sheave pressure) acting on the movable sheave 7b is controlled to adjust the belt - narrow pressure of the transmission belt 9.

[0027] In the example shown in FIG. 1, the forward - reverse switching mechanism 10 mainly includes a double - pinion type planetary gear mechanism 10a, a forward clutch (C1) 10b, and a reverse brake (B1) 10c. The forward - reverse switching mechanism 10 switches the rotation direction of the input shaft 3a to the forward direction or the reverse direction of the vehicle Ve by controlling the engagement and release states of the forward clutch 10b and the reverse brake 10c respectively. Also, by releasing both the forward clutch 10b and the reverse brake 10c, the neutral state of the belt - type continuously variable transmission 3 is set.

[0028] The oil pump 11 is a "mechanical oil pump" that generates hydraulic pressure when driven by the output torque of the engine 1. The hydraulic pressure generated by the oil pump 11 is supplied via the hydraulic control device to the hydraulic cylinder 7c of the primary pulley 7 and the hydraulic cylinder 8c of the secondary pulley 8, respectively, and the shift control and belt pressure control of the belt-type continuously variable transmission 3 are performed, respectively.

[0029] In this embodiment of the invention, the belt-type continuously variable transmission 3 shown in Figure 1 is basically the same configuration as the "belt-type continuously variable transmission" shown in "Figure 1" of Patent Document 1 and "Figure 4" of Japanese Patent Application Publication No. 2014-62596. Therefore, a detailed explanation of the configuration of each part of the belt-type continuously variable transmission 3 is the same as the content described in the specification of Patent Document 1 and the specification of Japanese Patent Application Publication No. 2014-62596.

[0030] The detection unit 4 is a device or apparatus for acquiring various data and information necessary for controlling the vehicle Ve, and includes, for example, a power supply unit, a microcomputer, sensors, and an input / output interface. In particular, the detection unit 4 in this embodiment of the invention detects various data for controlling the belt-type continuously variable transmission 3. For example, the detection unit 4 has various sensors and devices such as a vehicle speed sensor 4a for detecting vehicle speed, an acceleration sensor 4b for detecting the acceleration of the vehicle Ve, an oil pressure sensor 4c for detecting the oil pressure acting on the movable sheave 7b (primary sheave pressure) and the oil pressure acting on the movable sheave 8b (secondary sheave pressure), respectively, a rotation speed sensor 4d for detecting the engine speed, the rotation speed of the input shaft 3a (or primary pulley 7), and the rotation speed of the output shaft 3b (or secondary pulley 8), respectively, an oil temperature sensor 4e for detecting the oil temperature of the belt-type continuously variable transmission 3 (specifically, the temperature of the oil discharged by the oil pump 11), and an accelerator opening sensor 4f for detecting the amount of depression (or accelerator opening) of the accelerator pedal (not shown). The detection unit 4 is electrically connected to the controller 5, which will be described later, and outputs electrical signals, etc., as detection data to the controller 5, corresponding to the detected or calculated values ​​of the various sensors, equipment, and devices mentioned above.

[0031] Controller 5 is an electronic control device mainly composed of a microcomputer, and in this embodiment of the invention, Controller 5 controls the vehicle Ve, in particular the belt-type continuously variable transmission 3. Various data detected or calculated by the detection unit 4 are input to Controller 5. Controller 5 performs calculations using the input data and pre-stored data and calculation formulas. Controller 5 then outputs the calculation result as a control command signal and is configured to control the vehicle Ve as described above. Specifically, Controller 5 outputs a primary sheave pressure instruction pressure (hydraulic command value) to the hydraulic control device of the belt-type continuously variable transmission 3 and executes shift control of the belt-type continuously variable transmission 3. It also outputs a secondary sheave pressure instruction pressure (hydraulic command value) and executes belt narrow pressure control of the belt-type continuously variable transmission 3. Although Figure 1 shows an example in which one Controller 5 is provided, multiple Controller 5s may be provided for each device or equipment to be controlled, or for each control content.

[0032] As mentioned above, the belt-type continuously variable transmission 3 normally performs belt pressure control and gear shift control using feedback control, or a combination of feedback control and feedforward control. However, when the vehicle Ve is traveling at an extremely low speed, the rotational speed of the output shaft 3b of the belt-type continuously variable transmission 3 cannot be accurately detected, so gear shift control is performed using feedforward control without applying feedback control. In that case, if the oil in the belt-type continuously variable transmission 3 becomes hot and the discharge performance of the oil pump 11 decreases, the actual secondary sheave pressure (actual pressure) may become insufficient compared to the indicated pressure of the secondary sheave pressure, and the balance between the primary sheave pressure and the secondary sheave pressure may be disrupted towards the upshift side.

[0033] For example, as shown in the time chart in Figure 2, when the oil temperature of the belt-type continuously variable transmission 3 (CVT oil temperature) rises above a predetermined temperature, the discharge performance of the oil pump 11 decreases, and the amount of oil discharged decreases. Consequently, the actual pressure of the secondary sheave (Sec actual pressure) also decreases from around time t1, and there is a discrepancy between the indicated pressure of the secondary sheave (Sec indicated pressure) and the actual pressure. In other words, the balance between the primary sheave pressure and the secondary sheave pressure is disrupted towards the upshift side. Therefore, the actual gear ratio (actual gear ratio) of the belt-type continuously variable transmission 3 deviates in the downward direction, i.e., towards the upshift side, relative to the target gear ratio (in this case, the maximum gear ratio). Consequently, the belt-type continuously variable transmission 3 effectively continues to upshift, and as a result, there is a concern that the driving force of the vehicle Ve will be insufficient.

[0034] Therefore, in the vehicle control device in this embodiment of the invention, even when it becomes difficult to calculate the gear ratio of the belt-type continuously variable transmission 3 when the vehicle Ve is traveling at an extremely low speed, as described above, the control device is configured to perform the control shown in the flowchart of Figure 3 below in order to appropriately control the gear shift.

[0035] In the flowchart of Figure 3, first, in step S1, it is determined whether the vehicle speed is higher than a predetermined vehicle speed threshold A. The vehicle speed threshold A is a threshold used to determine the extremely low vehicle speed state at which it becomes difficult to calculate the actual gear ratio of the belt-type continuously variable transmission 3. For example, the lower limit of the vehicle speed at which it is possible to calculate the actual gear ratio of the belt-type continuously variable transmission 3 based on the detection value of the rotation speed sensor 4d is set as the vehicle speed threshold A. The vehicle speed threshold A is set in advance based on, for example, the results of driving experiments with actual vehicles or simulations.

[0036] If the vehicle speed is higher than the vehicle speed threshold A, meaning that the actual gear ratio of the belt-type continuously variable transmission 3 can be calculated, and the result is determined to be "Yes" in step S1, the process proceeds to step S2.

[0037] In step S2, the gear shifting of the conventional belt-type continuously variable transmission 3 is performed using feedback control, or a combination of feedback control and feedforward control. After the gear shifting of the conventional belt-type continuously variable transmission 3 is performed in step S2, the routine shown in the flowchart of Figure 3 is terminated.

[0038] On the other hand, if the vehicle speed is below the vehicle speed threshold A, that is, if it is difficult to calculate the actual gear ratio of the belt-type continuously variable transmission 3, and therefore the result in "No" in step S1, the process proceeds to step S3.

[0039] In step S3, it is determined whether a failure has occurred in the process of detecting the actual pressure of the secondary sheave. Specifically, it is determined whether the actual pressure of the secondary sheave detected by the hydraulic sensor 4c is higher than expected.

[0040] If the actual pressure of the secondary sheave detected by the hydraulic sensor 4c is higher than expected, and the result in a "Yes" in step S3, proceed to step S4.

[0041] In step S4, the transmission of the belt-type continuously variable transmission 3 is controlled by feedforward control, which calculates the indicated pressure of the primary sheave pressure using the actual pressure of the secondary sheave pressure. If the actual pressure of the secondary sheave pressure is used when calculating the indicated pressure of the primary sheave pressure in feedforward control, hydraulic vibration (hydraulic pulsation) may cause hunting in the transmission control. Therefore, under normal circumstances when no such failure occurs, the indicated pressure of the secondary sheave pressure is used when calculating the indicated pressure of the primary sheave pressure in feedforward control. On the other hand, in this case, the actual pressure of the secondary sheave pressure is higher than the assumed value equivalent to the indicated pressure (in the direction in which the actual gear ratio of the belt-type continuously variable transmission 3 increases), so the actual gear ratio becomes the maximum gear ratio and is not affected by hydraulic vibration, or is only slightly affected. Therefore, when such a failure occurs, the actual pressure of the secondary sheave pressure (detected value of hydraulic sensor 4c) is used when calculating the indicated pressure of the primary sheave pressure in feedforward control.

[0042] As described above, once the shift control of the belt-type continuously variable transmission 3 in the event of a failure is performed in step S4, the routine shown in the flowchart of Figure 3 is then terminated.

[0043] In contrast, since the above-mentioned failure has not occurred, step In S3 If the answer is "No," proceed to step S5.

[0044] In step S5, it is determined whether the oil temperature of the belt-type continuously variable transmission 3 (the temperature of the oil discharged by the oil pump) is higher than a predetermined oil temperature threshold B. The oil temperature threshold B is a threshold used to determine a high oil temperature condition in which the discharge performance of the oil pump 11 decreases, reducing the amount of oil discharged by the oil pump 11 and affecting the calculation of the actual gear ratio of the belt-type continuously variable transmission 3. If the oil temperature of the belt-type continuously variable transmission 3 is higher than this oil temperature threshold B, it is determined that there is a possibility of problems in calculating the actual gear ratio of the belt-type continuously variable transmission 3. The oil temperature threshold B is set in advance based on, for example, the results of driving experiments with actual vehicles or simulations.

[0045] If the oil temperature of the belt-type continuously variable transmission 3 is below the oil temperature threshold B, that is, the oil temperature is not high enough to cause problems when calculating the actual gear ratio of the belt-type continuously variable transmission 3, and the result in "No" in step S5, then proceed to step S6.

[0046] In step S6, the transmission of the belt-type continuously variable transmission 3 is controlled by feedforward control, which calculates the indicated pressure of the primary sheave pressure using the indicated pressure of the secondary sheave pressure. As mentioned above, when calculating the indicated pressure of the primary sheave pressure using feedforward control, the indicated pressure of the secondary sheave pressure is used instead of the actual pressure of the secondary sheave pressure (the value detected by the hydraulic sensor 4c) because of the influence of hydraulic vibration.

[0047] As described above, once the gear shift control of the belt-type continuously variable transmission 3 is performed in step S6, the routine shown in the flowchart of Figure 3 is then terminated.

[0048] If, in step S5, the result is "Yes" because the oil temperature of the belt-type continuously variable transmission 3 is higher than the oil temperature threshold B, which could cause problems when calculating the actual gear ratio of the belt-type continuously variable transmission 3, then the process proceeds to step S7.

[0049] In step S7, it is determined whether the rotational speed of engine 1 is lower than a predetermined rotational speed threshold C. The rotational speed threshold C is a threshold used to determine a low rotational speed state in which the amount of oil discharged by the oil pump 11 decreases, which affects the calculation of the actual gear ratio of the belt-type continuously variable transmission 3. If the rotational speed of engine 1 is lower than this rotational speed threshold C, it is determined that there is a possibility of problems when calculating the actual gear ratio of the belt-type continuously variable transmission 3. The rotational speed threshold C is set in advance based on, for example, the results of driving experiments with actual vehicles or simulations.

[0050] If the engine speed is above the rotational speed threshold C, that is, the engine speed is not low enough to cause problems when calculating the actual gear ratio of the belt-type continuously variable transmission 3, and the result in "No" in step S7, proceed to step S6.

[0051] In step S6, as before, the transmission of the belt-type continuously variable transmission 3 is performed by feedforward control, calculating the primary sheave pressure using the secondary sheave pressure indicator. After the transmission of the belt-type continuously variable transmission 3 is performed in step S6, the routine shown in the flowchart of Figure 3 is terminated.

[0052] If the result in step S7 is "Yes" because the engine speed is lower than the rotational speed threshold C, which could cause problems when calculating the actual gear ratio of the belt-type continuously variable transmission 3, then the process proceeds to step S8.

[0053] In step S8, it is determined whether the accelerator opening (or the amount of operation of the accelerator device such as the accelerator pedal) is lower than a predetermined accelerator opening threshold D. The accelerator opening threshold D is a threshold used to determine a condition in which belt slippage of the belt-type continuously variable transmission 3 is a concern due to a decrease in the actual pressure of the primary sheave pressure and secondary sheave pressure. Here, it is determined that belt slippage may occur if the accelerator opening is greater than or equal to the accelerator opening threshold D. The accelerator opening threshold D is set in advance based on, for example, the results of driving experiments with actual vehicles or simulations.

[0054] If the accelerator opening is greater than or equal to the accelerator opening threshold D, meaning that there is a possibility of belt slippage in the belt-type continuously variable transmission 3, and the result in "No" in step S8, proceed to step S6.

[0055] In step S6, as before, the transmission of the belt-type continuously variable transmission 3 is performed by feedforward control, calculating the primary sheave pressure using the secondary sheave pressure indicator. After the transmission of the belt-type continuously variable transmission 3 is performed in step S6, the routine shown in the flowchart of Figure 3 is terminated.

[0056] In contrast, because the accelerator opening is lower than the accelerator opening threshold D, that is, there is no concern about belt slippage in the belt-type continuously variable transmission 3, the step In S8 If the answer is "Yes," proceed to step S9.

[0057] In step S9, it is determined whether the road surface gradient on which the vehicle Ve travels (or is located) is smaller than a predetermined gradient threshold value E. Specifically, it is determined whether the absolute value of the road surface gradient is smaller than the gradient threshold value E. That is, if the gradient threshold value E on the uphill side is set as a positive value (+E) and the gradient threshold value E on the downhill side is set as a negative value (-E), it is determined whether the inequality of “-E < road surface gradient < E” holds. The gradient threshold value E, together with the above-mentioned accelerator opening threshold value D, is a threshold value for determining a state in which belt slip of the belt-type continuously variable transmission 3 is a concern due to a decrease in the actual pressures of the primary sheave pressure and the secondary sheave pressure. When the road surface gradient (absolute value) is greater than or equal to the gradient threshold value E, a large driving force (engine output torque) is required to prevent the vehicle Ve from slipping downhill on the slope road, so it is determined that belt slip may occur. The gradient threshold value E is preset based on, for example, the results of running experiments with actual vehicles, simulations, and the like.

[0058] If it is determined as “No” in this step S9 because the road surface gradient is greater than or equal to the gradient threshold value E, that is, there is a possibility of belt slip of the belt-type continuously variable transmission 3, the process proceeds to step S6.

[0059] In step S6, as before, by calculating the indicated pressure of the primary sheave pressure using the indicated pressure of the secondary sheave pressure in feedforward control, the shift control of the belt-type continuously variable transmission 3 is executed. Then, when the shift control of the belt-type continuously variable transmission 3 is executed in step S6, thereafter, the routine shown in the flowchart of FIG. 3 is temporarily terminated.

[0060] On the contrary, if it is determined as “Yes” in step S9 because the road surface gradient is smaller than the gradient threshold value E, that is, there is no concern of belt slip of the belt-type continuously variable transmission 3, the process proceeds to step S10.

[0061] Then, in step S10, using feedforward control, the transmission of the belt-type continuously variable transmission 3 is controlled by calculating the primary sheave pressure using the discharge rate of the oil pump 11 instead of the secondary sheave pressure indicator.

[0062] In the feedforward control described above, the indicated primary sheave pressure is calculated based on the thrust ratio characteristics of the belt-type continuously variable transmission 3. The thrust ratio of the belt-type continuously variable transmission 3 is the ratio of the primary sheave pressure (primary thrust) to the secondary sheave pressure (secondary thrust) in a steady state. The thrust ratio characteristics are characteristic values ​​of the belt-type continuously variable transmission 3 determined from the reciprocal of the safety factor of the transmission belt 9 and the gear ratio at which the primary thrust and secondary thrust balance each other. Typically, the thrust ratio characteristics of the belt-type continuously variable transmission 3 are calculated from a map that has been set up.

[0063] The target value (indicated pressure) Pintgt for the primary sheave pressure is the primary thrust used to balance the primary and secondary thrusts, as described above, and can be called the primary sheave balance thrust. If we denote the primary sheave balance thrust as clfinbl, the primary sheave pressure-receiving area as AIN, the secondary sheave target thrust as clfouttgt, the thrust ratio as taout, the target value (indicated pressure) for the secondary sheave pressure as pouttgt, and the secondary sheave pressure-receiving area as AOUT, then, respectively, Pintgt=clfinbl / taout clfinbl=clfouttgt / taout clfouttgt=pouttgt×AOUT The following relationship holds true.

[0064] Step S6, as described above, is a feedforward control that calculates the primary sheave pressure (Pintgt) using the secondary sheave pressure (pouttgt). Based on the above-mentioned relational expressions, the primary sheave pressure (Pintgt) is calculated, and the shift control of the belt-type continuously variable transmission 3 is executed. In contrast, in step S10, instead of the secondary sheave pressure (pouttgt), the primary sheave pressure (Pintgt) is calculated using the discharge rate of the oil pump 11. For example, the actual secondary sheave pressure is estimated from the discharge rate of the oil pump 11, which is calculated based on the engine speed and the oil temperature of the belt-type continuously variable transmission 3. Then, using this estimated value of the actual secondary sheave pressure, the primary sheave pressure (Pintgt) is calculated, and the shift control of the belt-type continuously variable transmission 3 is executed.

[0065] As described above, in step S10, the primary sheave pressure is calculated based on the discharge amount of the oil pump 11, and the shift control of the belt-type continuously variable transmission 3 is performed. After that, the routine shown in the flowchart of Figure 3 is terminated.

[0066] As shown in the time chart in Figure 4, when the oil temperature of the belt-type continuously variable transmission 3 (CVT oil temperature) rises above a predetermined temperature, the discharge performance of the oil pump 11 decreases, and the amount of oil discharged decreases. Consequently, from around time t11, the actual pressure of the secondary sheave (Sec actual pressure) also decreases, and there is a discrepancy between the indicated pressure of the secondary sheave (Sec indicated pressure) and the actual pressure. In other words, the balance between the primary sheave pressure and the secondary sheave pressure is disrupted towards the upshift side. In the conventional control method shown in the time chart in Figure 2, the indicated pressure of the primary sheave (Pri indicated pressure) is calculated based on the indicated pressure of the secondary sheave pressure, so the actual gear ratio deviates towards the upshift side relative to the target gear ratio of the belt-type continuously variable transmission 3. In contrast, in the control of this embodiment of the invention shown in the time chart of Figure 4, the indicated pressure of the primary sheave pressure (Pri indicated pressure) is calculated based on the discharge amount of the oil pump 11. Therefore, even if the actual pressure of the secondary sheave pressure decreases and deviates from the indicated pressure, the indicated pressure of the primary sheave pressure also decreases in accordance with the decrease in the actual pressure of the secondary sheave pressure. As a result, the actual gear ratio does not deviate from the target gear ratio of the belt-type continuously variable transmission 3, and appropriate gear control is performed in accordance with the target gear ratio.

[0067] As described above, in the vehicle control device in the embodiment of this invention ,car When both Ve vehicles are traveling at extremely low speeds and the oil temperature of the belt-type continuously variable transmission 3 is high, the primary sheave pressure is calculated based on the discharge amount of the oil pump 11, and shift control is performed. Therefore, even in situations where there is a discrepancy between the indicated pressure and the actual pressure of the secondary sheave pressure, feedforward control allows for the setting of an appropriate indicated pressure for the primary sheave pressure, balancing the primary and secondary sheave pressures.

[0068] Therefore, according to the vehicle control device in this embodiment of the invention, even when a vehicle Ve equipped with a belt-type continuously variable transmission 3 is traveling at an extremely low speed and the oil temperature of the belt-type continuously variable transmission 3 becomes high, making it difficult to calculate the gear ratio, the vehicle control device can still appropriately control the gear shift of the belt-type continuously variable transmission 3, generate appropriate driving force, and drive the vehicle Ve. [Explanation of symbols]

[0069] 1. Engine (ENG) 2 drive wheels 3. Belt-type continuously variable transmission 3a Input shaft (of a belt-type continuously variable transmission) 3b (Output shaft of a belt-type continuously variable transmission) 4. Detection Unit 4a Vehicle speed sensor (of the detection unit) 4b Accelerometer (of the detection unit) 4c (Detection unit) Hydraulic sensor 4d (Detection unit) rotation speed sensor 4e (Detection unit) Oil temperature sensor 4f (Detection unit) Accelerator opening sensor 5. Controller (ECU) 6 Torque converter 7 Primary Pulley 7a Fixed sheave (of the primary pulley) 7b (Primary pulley) movable sheave 7c (Primary pulley) hydraulic cylinder 8 Secondary Pulley 8a Fixed sheave (of the secondary pulley) 8b (Secondary pulley) movable sheave 8c (Secondary pulley) hydraulic cylinder 9. Transmission belt 10 Forward / Forward Switching Mechanism 10a Planetary gear mechanism (for forward / reverse switching mechanism) 10b Forward clutch (C1) (of the forward / reverse switching mechanism) 10c (Forward / reverse switching mechanism) Reverse brake (B1) 11 Oil pump Vehicle

Claims

[Claim 1] A vehicle control device comprising an engine, a belt-type continuously variable transmission having a primary pulley and a secondary pulley around which a transmission belt is wound, which transmits the torque output by the engine to the drive wheels, and an oil pump driven by the engine, wherein the device uses the hydraulic pressure generated by the oil pump to hydraulically control the primary sheave pressure supplied to the primary pulley and the secondary sheave pressure supplied to the secondary pulley, respectively, and performs belt narrowing pressure control and shift control of the belt-type continuously variable transmission, The system includes a controller for controlling the aforementioned belt-type continuously variable transmission, The aforementioned controller, The target gear ratio and actual gear ratio of the aforementioned belt-type continuously variable transmission are calculated, The gear shift control is performed by at least one of the following: feedback control, which calculates the primary sheave pressure to make the actual gear ratio follow the target gear ratio; or feedforward control, which calculates the primary sheave pressure that balances with the secondary sheave pressure based on the target gear ratio. If the vehicle is traveling at a speed below a predetermined speed threshold where it becomes difficult to calculate the actual gear ratio, and the temperature of the oil discharged by the oil pump is higher than a predetermined oil temperature threshold where the discharge performance of the oil pump deteriorates, the feedforward control calculates the primary sheave pressure from the oil discharge amount instead of the secondary sheave pressure, and then performs the gear shift control. A vehicle control device characterized by the following features.

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