Hydropneumatic and Hydractive Suspension Systems Guide
ITEM 8
Hydraulic Fluid Level
1. How is the reading of the hydraulic fluid level taken?
It is checked with the engine running and the drive lever height in its highest position. The indicator should be between the minimum and maximum marks.
Conjuntor-Breaker Settings
2. How is the setting adjusted for the conjuntor-breaker?
By using specific springs with washers.
Safety Valve Functioning
3. How can I check the functioning of the safety valve?
Leave the engine running with the height command in the high position until disjunction. Stop the engine when the disjunction starts and open the bleed screw on the conjuntor-breaker. After that, the car should not decrease in height.
Pipelines to the Deposit
4. How many pipelines reach the deposit?
One, which is the return line.
Fluid Pressure in the Tank
5. What is the fluid pressure in the tank?
There is no pressure because it has no pressure source.
Gas Used in the Spheres
6. What gas is used in the spheres?
Nitrogen.
Suspension Block Liquid Flow
7. What element allows the flow of liquid in the suspension blocks on the same route?
The valve.
Valve Fall Arrest Isolation
8. What components are isolated by the valve fall arrest when the vehicle is stopped?
The suspension circuit and the main hydraulic circuit.
Axis Pressure Differences
9. Why is the set pressure of the spheres of each axis different?
Because they support different amounts of weight.
Nitrogen Pressure Loss
10. What happens if a sphere loses nitrogen pressure?
That means the sphere needs to be replaced because it will not provide proper damping for the vehicle.
Hydractive Suspension
Hydraulic vs. Hydractive Suspension
1. What are the differences between a hydraulic suspension and a Hydractive suspension?
A hydraulic suspension is managed manually, while a Hydractive suspension is managed automatically.
Hydractive Suspension Elements
2. What are the elements of a Hydractive suspension?
- An electro-hydraulic unit
- 2 pneumatic spheres
- 3 springs for variation of flexibility
- 4 level indicator on the front axle
- 5 springs for rear tires
- 6 flexibility change dock
- 7 axle height indicator
- 8 control switchboard
- 9 wheel angle indicator
- 10 pressure liquid tank
- 11 accelerator and brake pedals
Hydractive Suspension Operating Conditions
3. What are the operating conditions of the Hydractive suspension? Explain.
- Soft: The stiffness regulator allows the flow of hydraulic fluid between the suspension elements of the same axle.
- Firm: The stiffness regulator prevents hydraulic fluid movement between the suspension elements of the same axle.
Hydractive Suspension Electrical Components
4. What are the electrical components of the Hydractive suspension?
- Control unit
- Sport mode switch
- Speed sensor
- Steering wheel sensor
- Body displacement sensor
- Throttle pedal travel sensor
- Brake pressure sensor
Vehicle Height Control
5. How is the height of the vehicle controlled?
Automatically or manually.
Abnormal Hardening Diagnosis
6. What needs to be checked to determine if the Hydractive suspension is hardening abnormally?
Ensure good continuity of the power and ground circuits of the control unit.
Control Unit Speed Dependence
7. How does the control unit operate depending on the speed?
By sending square waves with a speed ratio range.
Braking with Adherence Difference
8. What happens if, during braking, there is a large difference in adherence between the two wheels of the same axle?
The suspension becomes firm.
Suspension Regulation with ABS/ESP
9. What happens to the suspension during ABS/ESP regulation?
It becomes firm and then adjusts a second later.
Self-Leveling Suspension
Self-Leveling Mechanism
1. How does the self-leveling suspension work?
It works hydraulically and is controlled electronically. It can be regulated automatically without driver intervention.
Self-Leveling Management
2. How is the self-leveling suspension managed?
Electronically through an electronic control unit with two functions: manual, auto, and sport.
Self-Leveling Logic
3. How does the logic of the self-leveling suspension operate?
The suspension works at a minimum speed of 5 km/h, taking two positions with speed intervals and considering excessive rolling angle.
Self-Leveling Electrical Components
4. List the electrical components of the self-leveling suspension, the role they play in the suspension, and the operation of each.
- Switchboard: Runs in real-time and controls the functions of the suspension. Diagnoses failures that may arise.
- Contactor: Feeds the 4 solenoids. Allows the unit to excite the four valves based on certain signals.
- Selection Group: Allows the coupling of the desired type of operation. Indicates whether the vehicle has a suspension problem at startup.
- Acceleration Sensor: Detects vertical accelerations of the body. Informs the unit about the vertical accelerations of the body.
- Tacho Sensor: Transforms square pulse signals. Sends impulses to the sinusoidal oscillator.
- Brake Sensor: Closes the loop when it reaches a higher pressure and vice versa. Sends impulses to the sinusoidal oscillator.
- Speed Sensor: Informs the unit about the steering wheel position and speed of rotation. Sends impulses to a sinusoidal oscillator.
- Self-diagnosis: Reports anomalies.
Self-Diagnostic Controls
5. What does the self-diagnostic feature control?
- Warning light for breakdown
- Supply step relay for solenoid
- Solenoid
- Vertical acceleration sensor or accelerometer
- Speed sensor and steering wheel rotation sensor (steering)
- Tacho sensor
- Braking sensor
Hydro-Leveling Shock Absorber Operation
6. Explain the operation of hydro-leveling shock absorbers.
They operate automatically in response to increasing load. They are operated by a hydraulic pump that is integrated with the movements.
Hydropneumatic Spring Types
7. List the hydropneumatic spring types and their operation.
- Hydromat: The clearinghouse and the reservoir are located between the inner and outer tubes. It does not have a coil spring and requires more space than other types.
- Nivomat: With the high-pressure tank and a separate plunger above or below the working chamber, it is very compact and easy to install. It requires a coil spring.
Final Book Item 8
Hydropneumatic Suspension Advantages
1. What are the advantages of the hydropneumatic suspension?
- Ensures driving comfort and suspension elasticity
- Maintains constant ride height regardless of load
- Allows for a lower center of gravity, improving driving stability
- Improves suspension performance in a vacuum. The flexibility of the suspension varies with the load
- Allows for adjustment of the body height, up and down, for obstacles
- Integrates the shock absorbers into the suspension blocks, saving space
- Offers greater safety in case of a puncture, as the body remains horizontal
- Reduces suspension system maintenance
Hydropneumatic Suspension Hydraulic Circuit Elements
2. What are the main hydraulic circuit elements of the hydropneumatic suspension? What does each element do?
- Hydraulic Tank: A plastic or metal container that stores the hydraulic fluid to ensure the pump’s supply and allow for fluid return and recovery after use.
- Pressure Source: A high-pressure mechanical pump with constant flow. It is composed of various pumping elements arranged circularly.
- Pressure Regulator: Also called a conjuntor-breaker, it is one of the main elements of the circuit. It ensures regulated working pressure to guarantee the system’s proper functioning.
- Accumulator: A reservoir of hydraulic fluid under pressure. It consists of an additional chamber whose mission is to supply hydraulic fluid quickly when there is a demand from the circuit.
- Safety Valve: Gives priority to feeding the components that affect vehicle safety.
Conjuntor-Breaker Operation
3. Explain the operation of the conjuntor-breaker.
It works in two phases:
- Disjunction: In this phase, the pressure exceeds 170 bar. At this point, the internal pressure overcomes the spring force and closes the power flow. The flow of liquid coming from the pump is diverted through the valve action and returned to the tank while the circuit is isolated. While the liquid is consumed, the regulator remains in this position until the pressure drops to the minimum rate, which is approximately 145 bar.
- Conjunction: Chambers A and B reach a pressure of 145 ± 5 bar. At this point, the regulator shifts. It connects the pump’s power to the circuit. The outlet to the tank is closed.
Safety Valve Mission
4. What is the mission of the safety valve in the hydropneumatic suspension?
To give priority to feeding the components related to vehicle safety.
Hydropneumatic Shock Absorber Types
5. What types of hydropneumatic shock absorbers are there? What are their characteristics?
Double-acting shock absorbers are inserted into the bottom of the sphere. They consist of a synthesized steel washer with holes around its periphery. A deformable valve in the form of flakes obstructs oil flow through the holes.
Crash Valve Mission
6. What is the mission of the crash valve?
To isolate the suspension circuit from the main hydraulic circuit.
Hydractive Suspension Operating States
7. Explain the operating states of the Hydractive suspension.
- Soft: The stiffness regulator allows the flow of hydraulic fluid between the suspension elements of the same axle.
- Firm: The stiffness regulator prevents the movement of hydraulic fluid between the suspension elements of the same axle.
Hydractive Suspension Calculator Input Signals
8. What incoming signals does the Hydractive suspension calculator receive? What components does it control?
It receives pressure and speed signals to control the solenoid stiffness regulators.
ADS Suspension Operation
9. Explain the operation of the suspension with ADS level regulation.
It can regulate the hardness of the suspension depending on driving conditions and height.
Stiff Suspension Valve and Resonator
10. Why is there a valve in the stiff suspension with level control and damping control? What about the resonator?
The valve enables the cushion to work in two stages. The resonator absorbs the noise from the pump pulse.
Self-Leveling Hydropneumatic Shock
11. What is a self-leveling hydropneumatic shock?
It refers to a system where the suspension regulation is done mechanically.