[Basic knowledge of YesAuto] There is a group of engineers who have very developed auditory nerves and tactile nerves, but they don’t inherit the skills of old Chinese doctors in auscultation, nor do they work as the special agent Gold Wesler in “Eavesdropping Storm. Instead, it is committed to let everyone enjoy the pleasure of ears and body in the car. Although the term “driving quality” is often used in our ears, it is difficult for many car critics who “read countless cars” to explain it clearly to you. In the eyes of this group of engineers, driving quality is nothing more than three simple letters: NVH.
● What is NVH?
(If you don’t understand the above description, click here for a picture to easily understand NVH) For ordinary family cars, this kind of ear and body pleasure comes from the car’s quiet, comfortable and smooth driving experience; and for focused sports For sexual models, it also needs to have a surging and pleasant engine sound and direct road feedback. Therefore, different types of vehicles have different NVH evaluation standards and different driving qualities.
● Why use NVH performance to measure driving quality?
The Ride Quality of a car can be simply understood as whether the car is comfortable to drive or sit up, and whether it has a “grade sense”. It includes a series of content such as car sound insulation, vibration filtering, driving smoothness and handling texture, etc. , So it can be said that NVH level is the subdivision and quantification of driving quality.
-Why is the quality audible?
From the perspective of music theory, people are more willing to accept music and hate noise. The difference between music and noise lies in whether the sound is pure and harmonious. A pleasant sound can create a good car driving quality. The noise is unpleasant because it is caused by the irregular vibration of the object, the pitch and intensity of the sound will change irregularly, or it may be mixed with sharp and harsh high-frequency sounds. But judging from the actual driving experience, the basis of music theory is not perfect in the division of music and noise. For example, friends who like sports cars never hate the roar of exhaust pipes. They think this is a symbol of speed and passion. For middle-aged and elderly people who pay attention to quietness and comfort, this is undoubtedly unbearable noise. Therefore, what kind of sound represents good driving quality also varies from person to person or from car to car.
-Why does vibration affect driving quality?
“Bump” is a term that we often use to evaluate the comfort of a car. Where is the bump? How's it going? It is one of our methods to evaluate the driving quality of cars. People's perception of vibration is related to the position and direction of the feeling. For example, the human body is most sensitive to the vibration of 4-8Hz in the vertical direction, and the most sensitive to the vibration of 1-2Hz in the horizontal direction. These sensitive vibrations often resonate with human internal organs, head, etc., and cause uncomfortable feelings. (Part of the reason why people get motion sickness is the resonance of internal organs caused by vibration).
In short, don't say that you don't understand the driving quality of a car. As long as you have a pair of ears, sound limbs and a butt full of tactile nerves, you have the innate conditions to evaluate the quality of a car.
● 8 points of concern test driving quality, see how Roewe RX5 responds?
The driving quality is often reflected in the details, and it is each detail that affects your overall evaluation of the car. When we enter a Roewe RX5, what are the details that make us subconsciously judge the driving quality? Below we have summarized 8 details that are usually paid more attention. From these points of concern, Roewe RX5 has also been improved accordingly.
Concern 1: Is the sound of opening and closing the door pleasant?
Imagine how each contact between you and the car starts and ends in what way? That's right, it starts with opening the door handle and ends with closing the door. Therefore, these two actions in the subconscious will greatly affect your overall feeling of the car.
How to solve and optimize the sound problem of opening and closing doors, which is more concerned? The approach of Roewe RX5 is to add plastic parts to the door panel behind the door handle. When the handle is automatically retracted after opening the door, it can reduce the noise caused by the collision between the handle and the door panel (at the same time this plastic part also has a sealing effect) .
For door closing sound, the rigidity of the door and the body is also an important factor. Only moderate rigidity can produce a more pleasant sound at the moment of closing the door. Therefore, RX5 optimizes the rigidity of the door and body.
The sealing strip around the door affects the sound insulation level of the vehicle on the one hand, and on the other hand it also plays a great role in improving the quality of door closing sound. The sealing strip is actually a cavity structure. There are small holes on the sealing strip. The size, number and position of the small holes can be designed to control the pressure relief effect when closing the door, thereby improving the sound characteristics of closing the door. Avoid ear pressing when closing the door.
In addition, in order to avoid unnecessary noise when opening and closing the door, Roewe RX5 also optimizes the door lock for NVH.
Concern 2: How is the sound insulation inside the car?
“Close the door, it has nothing to do with the world”. It is no longer an exaggeration to use this phrase to describe the excellent sound insulation of the vehicle. In addition to deepening the color of the windows, another way to create a private space for drivers and passengers is to improve the sound insulation of the vehicle. With the basic structure of the body unchanged, the main task to improve the sound insulation of the vehicle is to improve the airtightness of the vehicle. Such as adding sealant and optimizing rubber components to block sound-transmitting holes and gaps can effectively improve the sound insulation of the vehicle.
Concern 3: Is the moment of ignition quiet enough?
At the moment the car is ignited, a series of internal parts of the car begin to operate. The noise and vibration levels of this process are also very important to our subjective feelings. So where do these noises and vibrations come from?
Subsequently, the starter exerts its maximum power to drive the engine to run. After a certain speed, the engine starts to work normally such as fuel injection and ignition. During this process, the starter will inevitably produce noise when it drives the engine to run. So how does the Roewe RX5 deal with the noise from the engine compartment when the ignition is started?
Focus 4: How much vibration does the body feel when driving?
Generally speaking, the parts that the driver touches most during driving are the floor, accelerator pedal, seat, steering wheel and shift lever from bottom to top. The vibration of these components is also a part of the quality of driving.
Although the current passenger car rarely has the phenomenon of shift lever thumping or excessive steering wheel shaking that causes hand numbness, but whether it is the floor, accelerator pedal, seat, steering wheel or shift lever, these components have subtle differences in vibration. Will show up when driving for a long time.
The vibration of the steering wheel, shift lever, seat and other components is generally transmitted directly or indirectly by the engine. Therefore, if you want to solve their vibration problems, you must start with the vibration source engine, because the vibration problem of the engine itself is difficult. Processing, so isolating engine vibration is the most common way.
Focus 5: Is the sound change smoothly during acceleration?
Acceleration speed is an important indicator for evaluating the dynamics of a car, and when it comes to the NVH performance of a vehicle, we must drive the car on the road to truly feel the noise changes when the car speed increases. It is difficult for us to express the size of the noise clearly in words, but what an ordinary consumer can feel is whether the sound in the ear changes evenly as the engine speed increases?
Judging from the current power system revealed by Roewe RX5, it uses 1.5L and 2.0L engines with turbocharged technology. Due to the inherent characteristics of supercharged engines, at the moment of turbocharging intervention, it will obviously affect the vibration and noise level and smoothness of the whole vehicle. Therefore, although turbocharging has improved power performance, from the perspective of NVH, the vibration and noise problems caused by these two turbocharged engines are more complicated than naturally aspirated engines.
For the optimization of the noise problem in the car during acceleration, Roewe drove the RX5 into a semi-anechoic room with a four-wheel drive drum to test the noise curve of the vehicle during acceleration in such an environment free from external noise interference. By analyzing the sounds of different frequencies in the noise curve, the root cause of the acceleration noise is diagnosed.
Generally speaking, it is the intake and exhaust system that has a greater impact on the noise in the car during acceleration. Intake resonant cavity and exhaust muffler are the main contributors to the solution of intake and exhaust noise. Roewe RX5 has a special design of its exhaust muffler, which improves the noise level in the car.
Solving the problem of vehicle vibration and noise is a complex project, and there is often a phenomenon of noise going down one after another, so it is the same for the acceleration noise of Roewe RX5. The ultimate goal of the engineer is to weigh a variety of factors. A state of equilibrium.
Focus 6: What is the amount of tire noise and wind noise introduced into the car when driving at medium and high speeds?
At idle and low speeds, the engine is often the main noise contributor to the car. When we let Roewe RX5 gradually accelerate to 60km/h, 80km/h, 100km/h, 120km/h…, vehicle tire noise and wind noise gradually become the main contributors to vehicle noise.
The optimization of tire noise is mainly reflected in the tire rubber formula, tire structure and tread pattern. For example, if you are careful, you will find that the pitch between the tread patterns is different. This is to avoid it during driving. Resonance leads to increased tire noise. The principle is similar to that when an army crosses a bridge, it must use small, inconsistent steps to pass.
Wind noise is an inevitable problem for every vehicle. Especially for SUV models, it is common for wind noise to be larger due to body styling factors. In order to sort out the air flow through the surface of the car body, Roewe RX5 adjusted the body shape in the wind tunnel laboratory.
What is mentioned above is how to solve the noise problem from the root cause, and how to deal with the unavoidable noise change? Then you must use another trick of the NVH solution-noise absorption. If you want to reduce the tire noise and wind noise generated by driving into the car, you must start from the noise propagation path. For example: Roewe RX5 is equipped with sound-absorbing cotton around the body.
Focus 7: Is it easy to hear the other person in a driving car?
Maybe we have all had this experience. Even if two people sitting in the car are close to each other when the car is driving, it is difficult to know what the other person is saying. This is why?
In a moving car, it is difficult for people to hear what the other person is saying clearly, mainly because the noise in the car and the voice of speaking have a masking effect. The sound frequency of each word in a sentence is different. The sound of different frequencies and the noise in the car have the effect of canceling each other in amplitude at a certain position, so it is difficult to hear certain words in a sentence.
The current way to improve the speech intelligibility of Roewe RX5 is mainly to improve the overall noise level of the car, such as reducing engine noise, intake and exhaust noise, tire noise, wind noise, etc., and isolating or absorbing noise sources introduced into the car. sound.
Concern 8: Are there any abnormal noises in the car when driving?
Abnormal noise in the car is one of the most common complaints by car owners, and it is also a problem that is easy to occur in the car. For example, abnormal noise in the dashboard, abnormal seat noise, abnormal noise in the window glass, etc., will cause the comfort of the people in the car. Great influence, so this is also a very important one to evaluate driving quality.
Roewe RX5 considered abnormal noise at the early stage of development and design. For example, the design of the air outlet of the air conditioner should not cause abnormal noise due to the wind; ensure a certain gap between the seat and the center armrest to avoid seating on bumpy roads. Friction noise occurs between the chair and the armrest box; in addition, the position of the seat belt buckle is also carefully designed to avoid collision with other interior parts when the buckle shakes.
After a few minutes of experience on the road condition simulation equipment in the abnormal noise test room, I did not hear any abnormal noise in the Roewe RX5 car. Although the abnormal noise in the car is small, it is a problem that we usually use in the car. Therefore, the R&D investment of the manufacturer in this area is very necessary.
The NVH level of a car is a very important aspect that reflects the driving quality. Although it is difficult for us ordinary consumers to understand the unpredictable NVH thoroughly, from the actual driving and riding experience, through the above 8 points of attention Subjectively, you can basically feel the pros and cons of a car's driving quality. In response to these eight issues that are most likely to affect subjective feelings, Roewe RX5 has been given key consideration, relying on the research center's semi-anechoic chamber, air tightness test equipment, road condition simulation equipment for detecting abnormal noise, etc., has conducted a lot of research and development test. In the end, whether the driving quality of Roewe RX5 can satisfy you, you still need to test drive it yourself. (Auto House Text/Xia Zhimeng Picture/Zhu Lishen)