Current location - Health Preservation Learning Network - Healthy weight loss - Knowledge Analysis of Automobile "Throttle": Pulling Wire &; Electrical control
Knowledge Analysis of Automobile "Throttle": Pulling Wire &; Electrical control
Content summary:

Throttle controls fuel injection process.

Advantages and disadvantages of cable throttling

Advantages and disadvantages of electronic throttle

First of all, we need to explain the most important point-"the accelerator pedal controls the valve"!

For non-automotive professional users, the understanding of many vehicle configurations is limited to literal meaning; Throttle is also understood to control the oil system of the vehicle. But the accelerator pedal of all cars will not directly control the oil pump or injector, because the oil pressure has a fixed standard, so how to adjust the fuel injection quantity?

"Air-fuel ratio" is the basis of indirect control of fuel injection, and the ratio is 14.7: 1, which can be understood as that only 14.7 kg of air can burn one kilogram of gasoline; So what is the amount of air entering the engine combustion chamber, and is it possible 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 accelerator; The throat "valve" of the engine is a throttle valve connected with the intake pipe, and then reaches the intake valve of the cylinder through the intake manifold. Pedal-controlled "main throttle", and cylinder valve is controlled by camshaft.

Figure 1: concepts of cable throttling and throttling

Figure 2: Dynamic demonstration of camshaft controlling intake valve and exhaust valve

Key point: What is a cable valve?

This structure is widely used in old vehicles, and the accelerator pedal of the vehicle is rigidly connected with the throttle through a steel cable or a connecting rod. This system is like the concept of "combination switch" or "marionette".

The change of pedal depth stroke controls the adjustment of throttle opening; In short, the deeper you step on the accelerator, the greater the valve opening. With the increase of air intake and fuel injection, the base of combustible substances can be increased and the engine torque can be improved. This structure is very advantageous because there is no delay in mechanical control at all. When the pedal touches here, the flap will open there and the dynamic response will be more direct.

However, the cable throttle has basically been eliminated, and there are basically no vehicles with this structure in mass production passenger cars at this stage. Why?

The reason is that the control accuracy of the cable throttle is very low, and the throttle opening is completely controlled by the number of steps; It is difficult to achieve sufficient linearity when operating the pedal. The opening of the flap does not increase a little, but jumps like a step, which will affect the calculation of fuel injection. Both carburetor and EFI system are prone to the problem of unbalanced air-fuel ratio. The result is that insufficient combustion will waste fuel, produce too much carbon monoxide, nitrogen oxides and hydrocarbons, and emit particulate matter, so being eliminated is an inevitable result.

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 with the accelerator, but serves as a controller for current regulation, and outputs signals with different standards to the electronic control system. The control system comprehensively judges the accurate operation data according to the operation signal, and then controls the motor to control the throttle opening.

The correct air-fuel ratio will be considered in the whole process, so the mixed oil and gas can always burn very fully under the condition of heat engine; This can not only save fuel and reduce emissions, but also reduce the formation efficiency of engine carbon deposit, so electronic throttle is the best and universal standard at present.

However, the electronic throttle also has disadvantages. The main problem is "power feedback is slow", because there are actually four steps in operation.

Control the throttle

system operation

Motor controlled throttle

The ECU calculates the fuel injection quantity.

If the acceleration of cable throttle control is synchronous or there is no time difference; Then the electronic throttle will have a time difference, that is, there is no acceleration at the moment of stepping on the throttle, 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 instantly, but there will be a linear pull-up process, so the sense of acceleration will be a bit slow.

However, this design is also a protection for the engine. For example, when the throttle is pulled, the maximum fuel injection quantity can be achieved instantly through the "full opening" of the valve, and the torque increase caused by combustion work will not be linear at all; Driving instead of walking will affect the driving quality, and it will be more dangerous for novices to step on the wrong pedal when driving.

Therefore, the electronic throttle is actually a "safety throttle", and the power feedback of slow half-beat is also to set a "fault-tolerant operation time" for the driver; This is the difference between the two pedals, and the overall advantage of the electronic pedal is greater.

This article comes from car home, the author of the car manufacturer, and does not represent car home's position.