Hill start method, system and vehicle based on automatic continuously variable transmission

Abstract

This application discloses a hill start method, system, and vehicle based on an automatic continuously variable transmission. The hill start method includes: determining whether the vehicle is in a hill start state; if so, executing a hill start assist method based on the transmission electronic control unit, including: receiving a current throttle opening signal and determining a first target engine speed based on the current throttle opening signal; when the clutch reaches the engagement point, controlling the engine speed to increase and controlling the clutch load to below a first threshold, while simultaneously receiving engine speed information; if the engine speed rises to the first target speed, controlling the clutch load to increase while the engine speed decreases, and the vehicle begins to climb; when the engine speed drops to a second target speed, controlling the clutch load to stop increasing, completing the hill start. This application solves the problem of difficulty in hill starts in vehicles with automatic continuously variable transmissions.

Description

Technical Field

[0001] The present application relates to the field of automotive technology, and more specifically, to a hill start method, system, and vehicle based on an automatic continuously variable transmission. Background Art

[0002] Starting a car on a slope is a common occurrence, requiring high levels of driver skill, especially for manual transmission cars, which require skilled coordination of the accelerator and clutch pedals. Insufficient power during a slope start can often cause the vehicle to roll or even stall, causing significant driver anxiety and potentially leading to accidents.

[0003] Currently, the hill start assist function of manual transmission (MT) models is that the engine electronic control unit (ECU) controls the electronic throttle to first increase the initial target speed. Then, when the driver releases the clutch pedal, the electronic throttle is automatically controlled to increase its opening during the clutch engagement process to compensate for the intake volume, control the engine speed, increase the vehicle's load resistance when the clutch is engaged, and ensure a smooth start of the vehicle.

[0004] Energy conservation and environmental protection are receiving increasing attention, and the country's corresponding passenger car fuel consumption regulations are constantly being updated and improved. The current fourth-stage passenger car standard "GB27999-2014 Passenger Car Fuel Consumption Evaluation Method and Indicators" also requires passenger car fuel consumption to meet the requirements; in order to meet domestic fuel consumption needs, various automobile manufacturers have gradually adopted small-displacement engines to reduce fuel consumption and emissions; the power performance of small-displacement engines is naturally reduced, so the challenges faced when starting on a slope will be greater.

[0005] To ensure that vehicle emissions and fuel consumption meet national regulatory requirements, CVT shift lines prioritize the engine's fuel economy zone, resulting in relatively low shift speeds. Furthermore, to minimize vehicle noise during startup, the target starting speed is relatively low. Unlike manual transmissions, CVT vehicles don't rely on the ECU to increase engine torque during hill starts. Instead, the transmission's electronic control unit (TCU) controls engine torque by controlling the starting speed. Therefore, low starting speeds can easily lead to insufficient starting torque, making hill starts difficult.

[0006] Currently, the mainstream hill start assist control solution for CVT models is the hill start assist system (HAC) derived from the vehicle stability program (ESP). The control body is the vehicle stability program (ESP), and its main function is to prevent the vehicle from sliding backward. It does not have the function of enhancing the climbing ability by increasing the vehicle's torque. Therefore, the existing HAC cannot solve the problem of CVT models' difficulty in starting on hills. Summary of the Invention

[0007] The present application provides a hill start method, system and vehicle based on an automatic continuously variable transmission. The hill start assist method is implemented by the transmission electronic control unit, which first quickly increases the engine speed under a smaller clutch load, and then increases the clutch load after the engine reaches sufficient torque to improve starting performance and maximum climbing grade, thereby solving the problem of difficult hill starting.

[0008] The present application provides a hill start method based on an automatic continuously variable transmission, comprising:

[0009] Determine whether the vehicle is in a hill start state;

[0010] If yes, a hill start assist method based on the transmission electronic control unit is executed, including:

[0011] receiving a current throttle opening signal, and determining a first target speed of the engine according to the current throttle opening signal;

[0012] When the clutch reaches the engagement point, the engine speed is controlled to increase, and the clutch load is controlled below a first threshold, while receiving the engine speed information;

[0013] If the engine speed rises to the first target speed, the load of the clutch is controlled to increase, while the engine speed decreases, and the vehicle starts to climb the slope;

[0014] When the engine speed drops to the second target speed, the load of the clutch is controlled to stop increasing, completing the hill start;

[0015] The first target speed is greater than the second target speed.

[0016] Preferably, the transmission electronic control unit controls the load of the clutch and the speed of the engine through the throttle opening.

[0017] Preferably, the method further includes identifying whether a hill start assist function switch based on a transmission electronic control unit is turned on;

[0018] If it is turned on and the vehicle is in the hill start state, the hill start assist method based on the transmission electronic control unit will be executed.

[0019] Preferably, if the vehicle is on a slope, the brakes of the vehicle are in a released state, the vehicle speed is less than a second threshold, and the current gear of the vehicle is a forward gear, the vehicle is in a slope starting state.

[0020] Preferably, the hill start assist method based on the gearbox electronic control unit is executed while the hill start assist method based on the vehicle body stability system is also executed.

[0021] The present application also provides a hill start system based on an automatic continuously variable transmission, comprising an engine electronic control unit, a vehicle body stability system, and a transmission electronic control unit;

[0022] The transmission electronic control unit is connected to the engine electronic control unit and the vehicle stability system signal through the CAN bus;

[0023] The transmission electronic control unit determines whether the vehicle is in a hill start state through the brake signal sent by the engine electronic control unit, the slope signal sent by the vehicle stability system, and the gear position signal recognized by itself;

[0024] The transmission electronic control unit includes a hill start assist module, which includes a first target speed determination module, a speed control module, an engine speed receiving module, a judgment module, and a load control module;

[0025] The first target speed determination module is used to determine the first target speed of the engine according to the throttle opening signal sent by the engine electronic control unit;

[0026] The speed control module is used to control the engine speed to increase before the engine speed increases to a first target speed, and is also used to control the engine speed to decrease after the engine speed increases to the first target speed;

[0027] The engine speed receiving module is used to receive the speed information sent by the engine electronic control unit;

[0028] The judging module is used to judge whether the engine speed has risen to a first target speed and whether the engine speed has fallen to a second target speed;

[0029] The load control module is configured to control the clutch load to be below a first threshold after the clutch reaches the engagement point and before the engine speed reaches a first target speed; is further configured to control the clutch load to increase after the engine speed reaches the first target speed; and is further configured to control the clutch load to stop increasing when the engine speed drops to a second target speed, thereby completing a hill start;

[0030] The first target speed is greater than the second target speed.

[0031] Preferably, the speed control module controls the load of the clutch and the speed of the engine by adjusting the throttle opening.

[0032] Preferably, the transmission electronic control unit further includes a hill start assist function switch.

[0033] Preferably, the vehicle body stabilization system further includes a hill start assist module, which is configured to work simultaneously with the hill start assist module in a hill start state.

[0034] The present application also provides a vehicle based on an automatic continuously variable transmission, which is used to execute the above-mentioned hill start method based on the automatic continuously variable transmission.

[0035] Other features and advantages of the present application will become apparent from the following detailed description of exemplary embodiments of the present application with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the application and, together with the description, serve to explain the principles of the application.

[0037] Figure 1 A structural diagram of the hill start system based on an automatic continuously variable transmission provided in this application;

[0038] Figure 2 A flowchart of a hill start method based on an automatic continuously variable transmission provided in this application;

[0039] Figure 3 A flowchart of the hill start assist method based on the transmission electronic control unit provided in this application;

[0040] Figure 4 A comparison diagram of the engine speed and vehicle speed curves during hill start in the present application and the prior art;

[0041] Figure 5 A comparison diagram of engine torque and clutch load torque during hill start in the present application and the prior art;

[0042] Figure 6 This is a structural diagram of the hill start assist module provided in this application. DETAILED DESCRIPTION

[0043] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0044] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses.

[0045] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0046] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0047] The present application provides a hill start method, system and vehicle based on an automatic continuously variable transmission. The hill start assist method is implemented by the transmission electronic control unit, which first quickly increases the engine speed under a smaller clutch load, and then increases the clutch load after the engine reaches sufficient torque to improve starting performance and maximum climbing grade, thereby solving the problem of difficult hill starting.

[0048] like Figure 1 As shown, the hill start system based on the automatic continuously variable transmission provided in this application includes an engine electronic control unit ECU, a body stability system ESP and a transmission electronic control unit TCU.

[0049] The transmission electronic control unit TCU is connected to the engine electronic control unit ECU and the body stability system ESP signal through the CAN bus.

[0050] The engine electronic control unit (ECU) detects the brake signal, indicating whether the brakes are released. It also detects the throttle signal, indicating the degree of throttle opening. The ECU sends the brake and throttle signals to the transmission electronic control unit (TCU).

[0051] The ESP system detects a ramp signal. In one embodiment, the ESP system sends a ramp on / off signal to the transmission electronic control unit (TCU) via the vehicle controller area network (CAN bus). This allows the TCU to directly identify whether the vehicle is on a slope. In another embodiment, the ESP system sends a gravity acceleration signal to the TCU via the CAN bus. The TCU's internal logic then calculates and determines whether the vehicle is on a slope.

[0052] The transmission electronic control unit TCU itself identifies the gear signal.

[0053] The transmission electronic control unit (TCU) includes a hill start assist module, which is used to assist the vehicle in starting on a hill.

[0054] Based on the aforementioned hill start system, this application provides a hill start method based on an automatic continuously variable transmission, which is executed by the transmission electronic control unit (TCU). It should be noted that the speed control logic in the hill start of this application is independent of the shift line control logic of the transmission electronic control unit (TCU).

[0055] like Figure 2 As shown, the hill start method includes:

[0056] S210: Determine whether the vehicle is in a hill start state. If yes, execute S220; otherwise, continue to execute S210.

[0057] Specifically, the transmission electronic control unit (TCU) receives the brake signal from the engine electronic control unit (ECU), the ramp signal from the vehicle stability control system (ESP), the vehicle speed signal from the electronic stability control system (ESC), and the gear position signal detected by the transmission electronic control unit (TCU). If the vehicle is on a slope, the brakes are released, the vehicle speed is less than a second threshold (e.g., 2 km / h or 1 km / h), and the vehicle's current gear is forward, the vehicle is determined to be in a hill start state. S220: Execute the hill start assist method based on the transmission electronic control unit.

[0058] Specifically, if Figure 3 As shown, the hill start assist method based on the transmission electronic control unit includes:

[0059] S310: Receive a current throttle opening signal, and determine a first target engine speed according to the current throttle opening signal.

[0060] Specifically, the transmission electronic control unit TCU receives the throttle opening signal from the engine electronic control unit ECU.

[0061] As an embodiment, each throttle opening corresponds to a calibration value of the first target speed.

[0062] S320: When the clutch reaches the engagement point, the engine speed is controlled to increase rapidly, and the load of the clutch is controlled to be below a first threshold, while receiving the engine speed information.

[0063] Specifically, the transmission electronic control unit (TCU) controls clutch load and engine speed based on throttle opening. This speed and clutch load control based on the vehicle's throttle opening provides flexible operation and, when used at 100% throttle, improves the vehicle's maximum gradeability.

[0064] As an example, in this application, each throttle opening corresponds to a calibrated value for the clutch oil filling rate. The clutch load is calculated by the transmission electronic control unit (TCU) based on the first target speed and the oil filling rate corresponding to the throttle opening. Therefore, each throttle opening corresponds to a clutch load value.

[0065] This application simulates the starting characteristics of a manual transmission (MT)—the higher the engine speed, the greater the torque—before the engine reaches rated speed and torque, rapidly increasing the engine speed to reach a higher torque point. However, it should be noted that while the MT's hill start assist is controlled by the engine's ECU, this application's hill start assist is controlled by the transmission's TCU.

[0066] S330: Determine whether the engine speed has reached the first target speed. If so, execute S340; otherwise, return to S320.

[0067] S340: Control the clutch load to increase while the engine speed decreases, the vehicle starts to climb, and receives engine speed information.

[0068] S350: Determine whether the engine speed has dropped to the second target speed. If so, execute S360; otherwise, return to S340.

[0069] The first target speed is greater than the second target speed.

[0070] As an embodiment, the second target rotation speed is a calibrated value.

[0071] S360: Control the clutch load to stop increasing and complete the hill start.

[0072] like Figure 4 and 5 As shown, stage 1 is the idling stage, that is, before the clutch reaches the engagement point, the engine speed, engine torque, and clutch load in this application are the same as those in the prior art.

[0073] In the prior art, during stages 2 and 3, engine torque builds and clutch load gradually increases, while engine speed and torque slowly increase to the speed and torque corresponding to the second target speed. During this process, due to the heavy clutch load, engine speed and torque increase with difficulty, ultimately reaching the speed and torque corresponding to the second target speed. This results in a low clutch load torque, leading to difficulty starting.

[0074] In stage 2, in the present application, as the throttle opening increases, the engine torque is established, the engine speed increases rapidly, and the clutch load is maintained at a low point. In this stage, since the clutch load is small, it is less difficult to increase the engine speed, and the final first target speed and the corresponding torque are greater than the speed and torque corresponding to the second target speed. The first target speed is used as a trigger condition for the clutch load to change. In stage 3, under a larger engine torque, the clutch load gradually increases, so that the clutch load obtains a larger engagement power, and the clutch load torque increases rapidly. At this time, the vehicle obtains sufficient torque and starts to climb (ie, vehicle speed>0). At the same time, as the clutch load increases rapidly, the engine speed decreases. After the engine speed drops to the second target speed, the clutch load stops increasing and reaches a steady state, as shown in stage 4.

[0075] From the above, in this application, the entire starting process is to achieve phased control of the clutch load through a higher first target speed and a lower second target speed, thereby achieving control of the engine speed and achieving stable starting of the vehicle. Figure 4As shown, the hill start assist method of the present application enables the vehicle to start climbing earlier than the prior art, and after the clutch load reaches a steady state, the vehicle speed of the present application is greater than the vehicle speed of the prior art. Therefore, the hill start assist method of the present application reduces the difficulty of hill starting and increases the speed of hill starting.

[0076] Preferably, during hill starting, the transmission electronic control unit TCU calculates the corresponding target speed in real time according to the change in throttle opening until the throttle opening stabilizes, and uses the target speed corresponding to the stabilized throttle opening as the first target speed, which is conducive to the smooth starting of the vehicle.

[0077] Based on the above hill start method, the transmission electronic control unit TCU includes a hill start assist module. Figure 6 As shown, the hill start assist module includes a first target speed determination module 610 , a speed control module 620 , an engine speed receiving module 630 , a determination module 640 and a load control module 650 .

[0078] The first target speed determination module 610 is configured to determine a first target speed of the engine according to a throttle opening signal sent by the engine electronic control unit.

[0079] The speed control module 620 is used to control the engine speed to increase before the engine speed increases to the first target speed, and is also used to control the engine speed to decrease after the engine speed increases to the first target speed.

[0080] As an embodiment, the speed control module 620 controls the clutch load and the engine speed by adjusting the throttle opening.

[0081] The engine speed receiving module 630 is used to receive speed information sent by the engine electronic control unit.

[0082] The determination module 640 is configured to determine whether the engine speed has risen to a first target speed and whether the engine speed has fallen to a second target speed.

[0083] The load control module 650 is used to control the load of the clutch to be below a first threshold value after the clutch reaches the engagement point and before the engine speed rises to the first target speed; it is also used to control the increase of the load of the clutch after the engine speed rises to the first target speed; it is also used to control the increase of the load of the clutch to complete the hill start when the engine speed drops to the second target speed.

[0084] Preferably, the transmission electronic control unit (TCU) also includes a hill start assist switch. The hill start assist module operates only when the hill start assist switch is on. Specifically, the hill start assist method based on the TCU is executed when the hill start assist switch is on and the vehicle is in a hill start state.

[0085] Preferably, the vehicle stability system also includes a hill-start assist module (HAC). The HAC's primary function is to prevent the vehicle from rolling backward. During a hill start, the HAC and the hill-start assist module operate simultaneously. This ensures the vehicle does not roll backward during a hill start, while also providing greater starting torque to facilitate hill starts, resulting in a more effective hill start.

[0086] Based on the above-mentioned hill start system and method, the present application also provides a vehicle based on an automatic continuously variable transmission, which includes the above-mentioned hill start system and executes the above-mentioned hill start method.

[0087] Without changing the vehicle's powertrain or reducing the vehicle's weight, this application optimizes the transmission control strategy, distinguishes between different working conditions on slopes and non-slopes, and achieves maximum torque output on slopes, thereby improving the vehicle's climbing performance; at the same time, it ensures NVH and driving comfort when the vehicle does not require too much torque when starting on non-slopes.

[0088] Although some specific embodiments of the present application have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present application. It should be understood by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A hill start method based on an automatic continuously variable transmission, characterized in that: include: Determine whether the vehicle is in a hill start state; If yes, a hill start assist method based on the transmission electronic control unit is executed, including: receiving a current throttle opening signal, and determining a first target speed of the engine according to the current throttle opening signal; When the clutch reaches the engagement point, controlling the engine speed to increase, controlling the clutch load to be below a first threshold, and receiving the engine speed information at the same time; If the engine speed increases to the first target speed, the load of the clutch is controlled to increase, while the engine speed decreases, and the vehicle starts to climb the slope; When the engine speed drops to a second target speed, the load of the clutch is controlled to stop increasing, thereby completing the hill start; Wherein, the first target speed is greater than the second target speed; The starting process is to achieve phased control of the clutch load through the first target speed and the second target speed: Stage 1, idling stage, before the clutch reaches the engagement point; In stage 2, as the throttle opening increases, the engine torque builds up, the engine speed increases rapidly, and the clutch load remains low. In stage 3, under the engine torque, the clutch load gradually increases, so that the vehicle obtains sufficient torque and starts to climb the slope; In stage 4, when the engine speed drops to the second target speed, the load on the clutch stops increasing and reaches a steady state.

2. The hill start method based on an automatic continuously variable transmission according to claim 1, characterized in that: The transmission electronic control unit controls the load of the clutch and the speed of the engine through the throttle opening.

3. The hill start method based on an automatic continuously variable transmission according to claim 1, characterized in that: It also includes identifying whether the hill start assist function switch based on the transmission electronic control unit is turned on; If it is turned on and the vehicle is in a hill start state, the hill start assist method based on the transmission electronic control unit is executed.

4. The hill start method based on an automatic continuously variable transmission according to claim 1, characterized in that: If the vehicle is on a slope, the brakes of the vehicle are in a released state, the vehicle speed is less than a second threshold, and the current gear of the vehicle is a forward gear, then the vehicle is in a slope start state.

5. The hill start method based on an automatic continuously variable transmission according to claim 3, characterized in that: While executing the hill start assist method based on the transmission electronic control unit, the hill start assist method based on the vehicle body stability system is also executed.

6. A hill start system based on an automatic continuously variable transmission, using the hill start method according to any one of claims 1 to 5, characterized in that: Including engine electronic control unit, body stability system, transmission electronic control unit; The transmission electronic control unit is connected to the engine electronic control unit and the vehicle stability system signal via a CAN bus; The transmission electronic control unit determines whether the vehicle is in a hill start state through the brake signal sent by the engine electronic control unit, the slope signal sent by the vehicle body stability system, and the gear position signal recognized by itself; The transmission electronic control unit includes a hill start assist module, which includes a first target speed determination module, a speed control module, an engine speed receiving module, a judgment module, and a load control module; The first target speed determination module is used to determine a first target speed of the engine according to the throttle opening signal sent by the engine electronic control unit; The speed control module is used to control the engine speed to increase before the engine speed increases to the first target speed, and is also used to control the engine speed to decrease after the engine speed increases to the first target speed; The engine speed receiving module is used to receive the speed information sent by the engine electronic control unit; The judging module is configured to judge whether the engine speed has risen to the first target speed and whether the engine speed has fallen to the second target speed; The load control module is configured to control the load of the clutch to be below a first threshold after the clutch reaches an engagement point and before the engine speed rises to the first target speed; is further configured to control the load of the clutch to increase after the engine speed rises to the first target speed; and is further configured to control the load of the clutch to stop increasing when the engine speed drops to the second target speed, thereby completing a hill start; Wherein, the first target speed is greater than the second target speed.

7. The hill start system based on an automatic continuously variable transmission according to claim 6, characterized in that: The speed control module controls the load of the clutch and the speed of the engine according to the throttle opening.

8. The hill start system based on an automatic continuously variable transmission according to claim 6, characterized in that: The transmission electronic control unit also includes a hill start assist function switch.

9. The hill start system based on an automatic continuously variable transmission according to claim 8, characterized in that: The vehicle body stabilization system further includes a hill start assist module, which is configured to work simultaneously with the hill start assist module in a hill start state.

10. A vehicle based on an automatic continuously variable transmission, characterized in that: The vehicle is used to execute the hill start method based on an automatic continuously variable transmission according to any one of claims 1 to 5.

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