What is the role of a power steering pump in a car?

- Sep 19, 2019-

Steering gear and steering gear form

A steering gear (also often referred to as a steering gear) is a set of gear mechanisms that perform a rotary motion to a linear motion (or approximately linear motion) and is also a reduction gearing in a steering system. There have been many types of steering gears in history. At present, there are commonly used gear rack type, worm crank finger type, recirculating ball-rack type fan type, recirculating ball crank type pin type, worm wheel type and the like. The second and fourth types are the first and third variants, respectively, while the worm roller type is less common. We only introduce the two most commonly used and most representative shapes: rack and pinion and recirculating ball.

Rack and pinion type: The biggest feature of the rack and pinion method is its high rigidity, compact structure, light weight and low cost. Since this method is easy to transmit the reaction force to the steering wheel by the wheel, it has the advantage of being sensitive to the state of the road surface, but at the same time, it is easy to generate the phenomenon of hitting and shimmy. The gear meshes directly with the rack to convert the rotational motion of the gear into a linear motion of the rack, causing the steering rod to pull the wheel laterally to deflect. The gear is not a simple spur gear, but a special spiral shape. This is to minimize the meshing gap between the gear and the rack, so that the slight rotation of the steering wheel can be transmitted to the wheel, which improves the sensitivity of the operation. It is generally said to reduce the amount of steering wheel. However, it is not a good thing that the gear meshes too tightly. It makes the operating force when turning the steering wheel too large, and people will feel strenuous.

Recirculating ball type: This kind of steering device is used to reduce the rotational force from the steering wheel by the gear mechanism, so that the rotary motion of the steering wheel becomes the rotary motion of the worm, the ball screw and the nut sandwich the steel ball, and thus the ball screw The rotary motion becomes a linear motion, and the nut is meshed with the sector gear. The linear motion becomes a rotary motion again, causing the link arm to swing, and the link arm linearly moves the linkage lever and the tie rod to change the direction of the wheel.

Power steering mechanism

The power steering machine is a device that uses external power to assist the driver to operate the steering wheel lightly. With the recent increase in the horsepower of automobile engines and the widespread use of flat tires, both the weight of the vehicle and the steering resistance have increased, and thus the power steering mechanism has become more and more popular. It is worth noting that the steering assist should not be constant, because at high speeds, the lateral resistance of the tire is small, the steering wheel becomes light, it is difficult to capture the feeling of the road, and it is easy to cause the steering to be too sensitive and the car is not easy to control. . Therefore, it is necessary to reduce the power properly at high speeds, but this change must be smooth and excessive.

(1) Hydraulic power steering device

The hydraulic power steering unit is light in weight and compact in structure, which is good for improving the steering operation feeling. However, the increase in the liquid flow rate will increase the load of the pump and the mechanism for maintaining the idle rotation.

(2) Electric power steering device

The electric power steering device is the latest form of steering device, and it is highly valued because of its energy saving. It uses the battery to rotate the motor to generate thrust. Since the power of the engine is not directly used, the power loss of the engine is greatly reduced (hydraulic maximum loss is 5-10 hp), and hydraulic piping is not required, which is convenient for installation. Especially suitable for mid-engine rear-wheel drive vehicles. However, the power of the electric power steering device is not comparable to that of the hydraulic type, so it can only be used in a car with a front axle that is lightly driven by a mid-engine.

(3) Electro-hydraulic power steering device

That is, the motor drives the power steering pump and is controlled by a computer, which combines the advantages of hydraulic and electric. Because it is computer controlled, the steering booster pump does not have to work often, saving engine power. This method is compact and easy to install, but the hydraulic power can not be too large, so it is suitable for cars with small displacement.