Vacuum Pump Disconnectable Drive Coupling
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Solution Overview
Problem
Existing vacuum pumps for vehicles experience parasitic losses due to continuous operation, leading to reduced fuel efficiency, and current disconnectable drive solutions face issues with cold start engagement, shock loading, and clutch durability, especially with friction clutches and mechanical drives.
Innovation Solution
A disconnectable drive coupling with a speed synchronizing clutch and a coupling sleeve that uses fluid pressure to engage and disengage, featuring a resiliently urged annular piston and drive formations on both shafts, allowing for failsafe operation without electrical components, and minimizing shock loading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a friction clutch is used to disengage the vacuum pump drive, then the pump can be disengaged to reduce parasitic losses, but the clutch life is reduced under cold start conditions due to high drive torque requirements
Solution Approach 1:
The drive coupling is segmented into multiple functional components: a friction clutch for initial engagement and speed synchronization, and a mechanical dog clutch for final positive drive connection. This segmentation allows each component to perform its specialized function optimally - the friction clutch handles speed matching without shock, while the dog clutch provides reliable mechanical engagement.
Solution Approach 2:
The friction clutch performs preliminary action by synchronizing the speeds of the input and output shafts before the dog clutch engages. This speed synchronization prevents shock loading during the subsequent mechanical engagement, thereby protecting the clutch components and extending their service life while still enabling pump disengagement to reduce parasitic losses.
2Reliability
If a mechanical drive connection such as a dog clutch is used, then reliable engagement is achieved, but shock loading occurs during connection
Solution Approach 1:
Speed synchronization is performed as a preliminary action before the mechanical dog clutch engagement. The friction clutch gradually matches the rotational speeds of the input and output shafts, ensuring that when the dog clutch engages, there is minimal speed differential and thus minimal shock loading, while maintaining reliable mechanical connection.
Solution Approach 2:
The friction clutch acts as a cushioning element before the rigid dog clutch engagement. It absorbs and dissipates the kinetic energy difference between the two shafts through friction, preventing the shock that would otherwise occur during direct mechanical engagement, thereby protecting the drive train components.
3Reliability
If the vacuum pump runs continuously to ensure vacuum availability, then vacuum is always available, but fuel consumption increases due to parasitic losses
Solution Approach 1:
The drive coupling transitions from a static continuous connection to a dynamic disconnectable connection. The pump drive can be engaged or disengaged based on actual vacuum demand, allowing the system to adapt its operational state - connected when vacuum is needed, disconnected when not needed - thereby reducing parasitic losses while maintaining vacuum availability when required.
Solution Approach 2:
The system uses the vehicle's existing hydraulic system fluid pressure to automatically actuate the drive coupling engagement and disengagement. When hydraulic pressure is available (indicating engine running and hydraulic system active), the drive coupling engages automatically, eliminating the need for separate vacuum demand sensing and control mechanisms.
4Loss of energy
If a disconnectable drive coupling is implemented, then parasitic losses are reduced, but device complexity increases
Solution Approach 1:
The friction clutch and dog clutch mechanisms are merged into a single integrated drive coupling assembly that operates automatically based on hydraulic system conditions. This integration eliminates the need for separate control systems, sensors, and actuators, reducing overall system complexity while still achieving the benefit of reduced parasitic losses through automatic engagement/disengagement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reduces parasitic losses by enabling efficient engagement and disengagement of the vacuum pump drive, ensuring reliable operation across various conditions, including cold starts, while maintaining clutch longevity and avoiding shock loading.
Implementation Method 1
the coupling sleeve forming part of an annular piston which is movable in response to an increase in fluid pressure to achieve a disengaged condition
Implementation Method 2
The speed synchronising clutch is in use used to synchronise the speed of the input and output shafts prior to coupling the shafts together such that relative rotation is obviated
Implementation Method 3
said coupling sleeve is resiliently urged to an engaged condition where the input shaft is coupled for rotation with the output shaft
Data Source
Figure 1~2
Figure 3
Figure 4~9
AI summary
A vacuum pump drive is disconnectable from a drive shaft upon movement of a piston against a return spring, under the action of oil pressure. The piston comprises a speed synchronising clutch engageable with the input shaft to rotate the piston at the speed of the input shaft, and teeth to directly dog the piston and input shaft together. The arrangement provides a failsafe drive coupling capable of high torque transmission in direct dog drive.