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Knowledge analysis of automobile 'throttle': cable u0026 electronic control

by:Yisheng      2021-06-10

Content overview:

Throttle control injection process

The advantages and disadvantages of the cable throttle

The advantages and disadvantages of the electronic throttle

First of all, I need to explain the most important point-'The accelerator pedal controls the valve'!

For non-automotive users, the understanding of many configurations of the vehicle is limited to the literal meaning; the accelerator is also understood as the oil system of the vehicle, but the accelerator pedal of all cars is not It will directly control the fuel pump or fuel injection nozzle, because the fuel pressure has to have a fixed standard, so how to adjust the fuel injection volume?

'Air-fuel ratio' is the basis for indirect control of fuel injection. The ratio is 14.7:1, which can be understood as 14.7 kg Only one kilogram of gasoline can be burned by air; then, what is the amount of air entering the combustion chamber of the engine? Is it enough to adjust the fuel injection amount in the same proportion?

This is the way to control fuel injection, and the accelerator pedal needs to control the [throttle valve]; the engine's throat 'valve' is the throttle valve connected to the intake pipe, and then reaches the cylinder through the intake manifold Intake valve. In the pedal-controlled 'total throttle

Figure 1: The concept of cable throttle and throttle

Figure 2: Camshaft controls intake and exhaust Dynamic demonstration of the door

Key point: What is the cable valve?

Once old vehicles generally use this structure. The accelerator pedal of the vehicle will be rigidly connected to the throttle through a steel cable or a connecting rod. This system is like a 'combination switchThe concept of 'Puppets'.

The change of the pedal depth stroke controls the adjustment of the throttle flap opening; in short, the deeper the throttle, the greater the valve opening, and the amount of intake and fuel injection As the amount increases, the base number of combustibles can be increased to increase the torque of the engine. This structure is very advantageous because the mechanical control will not be delayed at all. When the pedal is touched here, the flap will be turned on there, and the dynamic response will be more direct.

However, the cable throttle has been basically eliminated. At this stage, mass-produced passenger cars can hardly find vehicles using this structure. Now, why is this?

The reason is that the control precision of the cable throttle is very low, and the throttle opening depends entirely on the control of the footsteps; it is difficult to achieve sufficient linearity when operating the pedal, and the opening of the flap is not uniform from small to large. A little bit of increase, but a jump like a step, this will affect the calculation of the fuel injection volume, whether it is the carburetor or the electronic injection system, it is prone to the problem of air-fuel ratio imbalance. The result is that insufficient combustion will waste fuel, and will produce too much carbon monoxide, nitrogen oxides and hydrocarbons, and particulate matter emissions, so being eliminated is an inevitable outcome.

Question: What is the concept of electronic throttle?

The concept of electronics is of course 'electronic control.' The accelerator pedal is no longer rigidly connected to the throttle, but as a controller for current adjustment, which outputs signals of different standards to the electronic control system; the control system operates according to the operation The signal comprehensively judges the accurate operating data, and then controls the motor to complete the action of controlling the throttle opening.

The entire process will take into account the correct ratio of air-fuel ratio, so in a warm engine state, the mixed oil and gas can always be burned very fully; this can not only save fuel and reduce emissions, but also reduce engine carbon deposits. The formation efficiency of the electronic throttle is the best at present, and it is also the universal standard.

But the electronic throttle also has shortcomings. The problem is mainly 'power feedback·slow half beatstep.

Control the throttle

System calculation

Motor control throttle

ECU calculates the fuel injection volume

If you say Pulling the throttle to control acceleration is synchronized, or there is no time difference; then there will be a time difference in the electronic throttle, that is, when you step on the throttle, you will find that there is no acceleration, but it will start after about half a second, and even if the pedal is stepped to the end, The intake fuel injection quantity controlled by ECU will not reach the highest standard in an instant. Instead, there must be a linear pull-up process, so the acceleration will appear to be a little slow.

However, this design also protects the engine. For example, the cable throttle can instantly reach the maximum fuel injection volume through the “full opening” of the valve. At this time, the torque increase generated by the combustion work will not be linear at all; for daily transportation driving, it will affect the driving quality, and it will be more dangerous for novice drivers to drive the wrong pedal.

So the electronic throttle can actually be regarded as a 'safety throttleThe overall advantage is greater.

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