You may not know that a key component in a car engine is the "baton" of the entire system, controlling the engine's operating rhythm: the camshaft. Don't underestimate this shaft; it has a crucial impact on engine performance. Today, we'll explore the importance of the car camshaft in detail.

Let's start with how the engine works. The engine is the heart of the car, continuously providing power to keep it going. For example, a common four-stroke engine operates through four strokes: intake, compression, power, and exhaust. During the intake stroke, the piston moves downward, opening the intake valve and drawing a fresh mixture of air and fuel into the cylinder. Next, during the compression stroke, both the intake and exhaust valves close, and the piston moves upward, compressing the mixture. This power stroke follows, with the spark plug igniting and the mixture burning, generating powerful thrust that pushes the piston downward, thereby outputting power. Finally, during the exhaust stroke, the piston moves upward again, opening the exhaust valve and expelling the burned exhaust gases from the cylinder. This repetitive process enables the engine to operate continuously.

The camshaft plays a crucial role in this process. It is primarily responsible for controlling the opening and closing of the valves. Think of the valves as the cylinder's "gates," and the camshaft as the "gatekeeper," precisely controlling when these gates open and close, how wide they open, and how quickly they open and close. In a four-stroke engine, the camshaft typically rotates at half the speed of the crankshaft. This is because the crankshaft rotates twice for the engine to complete a full cycle of intake, compression, power, and exhaust, while the camshaft only needs to control the opening and closing of the valves once. Despite rotating at half the speed of the crankshaft, the camshaft still rotates at high speeds and must withstand significant torque, placing high demands on its strength and support during design. Camshafts are typically constructed of high-quality alloy steel or special cast iron, though forgings are sometimes used.

Structurally, the camshaft's main body is a cylindrical rod approximately the length of the cylinder bank. Attached to this rod are multiple cams, which actuate the valves. One end of the camshaft is supported by a bearing, ensuring its secure attachment to the engine; the other end is connected to the drive wheel, through which it receives power from the crankshaft. A close look at the side of the cam reveals its egg-shaped design. This design is not random but carefully calculated. This unique shape enables the valves to open and close in the shortest possible time, ensuring sufficient intake and exhaust of air into and out of the cylinders. Furthermore, to ensure engine durability and smooth operation, the acceleration and deceleration of the valves during opening and closing must be smooth, avoiding excessive shock. Otherwise, valve wear will occur, noise will increase, and other serious consequences may occur. Therefore, the design of the cam is closely related to the engine's power, torque output, and smooth operation.

The relationship between cams and valves varies depending on the engine type. For example, in an in-line engine, one cam is typically associated with one valve; in a V-type or horizontally opposed engine, two valves typically share a cam. However, rotary engines and valveless engines, due to their unique structure, do not require a camshaft.

Camshafts are typically located in three configurations: undermount, midmount, and overhead. Undermount camshafts are located in the crankcase, midmount camshafts are located in the engine block, and overhead camshafts are located in the cylinder head. Currently, most production vehicle engines use overhead camshafts. Overhead camshafts offer significant advantages: they reduce the number of moving parts, shorten the transmission chain, increase overall mechanism rigidity, and bring the camshaft closer to the valves. This reduces the kinetic energy loss caused by the large distance between the camshaft and the valves, a common problem with undermount camshafts. As a result, overhead camshafts enable faster valve opening and closing, higher speeds, and smoother operation.

Camshafts operate under demanding conditions. They are subject to periodic impact loads, high contact stress between the cam and tappet, and high relative sliding speeds, resulting in significant wear on the cam's working surface. To meet these challenges, the camshaft journals and cam running surfaces must not only exhibit high dimensional accuracy, minimal surface roughness, and sufficient rigidity, but also high wear resistance and excellent lubrication properties. Camshafts are typically forged from high-quality carbon steel or alloy steel, though cast alloy cast iron or ductile iron is also sometimes used. The journals and cam running surfaces require a polished finish after heat treatment to meet these stringent requirements.

What problems can camshafts easily encounter during operation? Common failures include abnormal wear, noise, and breakage. Notably, noise and breakage often occur after abnormal wear. For example, the camshaft is located near the end of the engine's lubrication system, providing poor lubrication conditions. If the oil pump is operating for extended periods, resulting in insufficient oil supply pressure, clogged lubricating oil passages, or excessive tightening torque on the bearing cap bolts prevents lubricant from reaching the camshaft clearance, these conditions can cause abnormal camshaft wear. Once the camshaft exhibits abnormal wear, the clearance between it and the bearing seat increases, potentially causing axial displacement during movement and generating noise. Furthermore, abnormal wear can increase the gap between the drive cam and the hydraulic tappet, causing a collision when the two meet, also producing unusual noise. More seriously, camshaft failures can sometimes occur, such as breakage. This can be caused by factors such as a broken or severely worn hydraulic tappet, poor lubrication, poor camshaft quality, or a cracked camshaft timing gear. In some cases, camshaft failures are caused by human error, particularly improper camshaft disassembly and assembly during engine repair. Examples include forceful hammering or prying with a screwdriver when removing the camshaft bearing cap; incorrect installation of the bearing cap, resulting in a mismatch between the bearing cap and the bearing seat; or excessive tightening torque on the bearing cap fastening bolts. Therefore, when installing the bearing cap, be sure to pay attention to the directional arrows and position numbers marked on the bearing cap surface and tighten the bearing cap fastening bolts using a torque wrench to the specified torque.

If you suspect the camshaft may be damaged, there are several ways to diagnose it. First, regarding starting, if the engine experiences difficulty starting or the engine is difficult to start, there may be a problem with the camshaft or its position sensor. Next, observe the engine's operating status and sound. Any unusual noise or vibration during operation could indicate a camshaft problem. Performance-wise, symptoms like lack of engine power, increased fuel consumption, vehicle jitter, and sudden stalling during warm-up could indicate camshaft damage. Additionally, inspect the camshaft for wear, observing any surface blurring, breakage, or dimensional changes. Check the bearings for excessive wear on the bolts, nuts, and bearings. Check the cavities for accumulated water, dust, and other impurities. Check the angles to ensure the mounting and installation angles are consistent. Check the engine oil for blackening, metallic particles, or rapid depletion, which could indicate camshaft wear. Listen for unusually increased engine noise, shuddering and vibration at high speeds, or leaking air during startup, which could also indicate a camshaft problem. Monitor engine performance, including decreased acceleration and fuel economy, which could indicate camshaft damage. Alternatively, you can use a diagnostic tool to read engine fault codes and make a diagnosis based on the actual situation. If camshaft damage is suspected, it is recommended to consult a professional technician who will use specialized equipment and techniques for diagnosis and repair.

To boost engine power, some modification shops modify the engine's camshafts, with installing high-angle camshafts being a common method. Compared to standard camshafts, high-angle camshafts have a wider cam angle. While standard camshafts typically operate at around 240°, high-angle camshafts typically reach over 280°. This wide camshaft angle prolongs valve opening time and increases valve lift, allowing the intake and exhaust valves to open earlier and close later, allowing more air to enter the cylinders and improving engine power at medium and high rpm. However, for everyday civilian vehicles, it's important to choose a camshaft with an operating angle below 278°. This is because camshafts with operating angles exceeding 278° significantly increase valve overlap. While this significantly boosts power at high rpm, it can also reduce cylinder sealing at low rpm, leading to severe idle jitter and even stalling. Such vehicles are more suitable for racing than for everyday driving.

With the continuous advancement of automotive technology, the requirements for camshafts are also increasing. In terms of production technology, the hardness and white cast layer depth of the camshaft lobe are key technical indicators that determine camshaft service life and engine efficiency. While ensuring the camshaft has sufficiently high hardness and a deep white cast layer, it is also important to ensure that the journal does not contain excessive carbides to maintain good machinability. Various camshaft production methods are used both domestically and internationally. For example, a process uses a steel forging blank, then, after machining, high-frequency quenches the cam lobe to form a martensitic layer. In the late 1970s, Germany and France developed a new argon arc remelting process for camshafts. Furthermore, there are hardenable cast iron camshafts, primarily in the United States, chilled cast iron camshafts, primarily in Japan and France, and production processes that use Cr-Mn-Mo alloy coatings to alloy the casting surface in the cam area.

In short, although the camshaft is just one component in the engine, it plays a vital role, like a conductor in an orchestra, precisely controlling the engine's operating rhythm. From its structure and operating principles to common faults and repairs, and even modifications and development trends, every aspect is closely related to engine performance. Understanding camshafts will deepen your understanding of automotive engines. We hope this article provides a comprehensive perspective and helps you better understand automotive camshafts. If you found this article helpful, please like and follow us. Your support will fuel our continued progress.