Abstract
Hydraulic Hybrid Vehicles (HHV) store energy/power in a pressurized gas and converting that energy when needed using hydraulic motors. Hydraulically operated vehicles are not new; however the concept using hydraulics as a hybridization technology is innovative and has been proven both very feasible and efficient. In fact, recent work has shown that hydraulic hybrids are capable of being more than 70% more fuel efficient over conventional vehicles while having a payback of only 2 years. When comparing this to electric hybrid technologies with a maximum of 42% fuel efficiency with a payback of 11 years, clearly, this technology needs to be explored further. However, hydraulic hybrids are not without problems. One of the problems reported from testing is that the noise levels emitted by the hydraulic pumps and motors are not acceptable. The lack of space, the extreme pressures and the dynamics of components with the pump/motor unit limits direct observation or measurement of potential noise causing mechanisms. As a result, there are several theories as to the source of the noise from the pump units but little concrete information to further isolate and reduce the noise generation. This paper presents a dynamic model of a bent axis pump with the objective to find the dominating harmonics that create the noise in the bent axis pump. The differential equations of the piston pressure and the equations of motion of the pump’s parts were developed, and verified at a constant angular speed of the main shaft and yoke angles ranging from 5° to 40°.
Keywords: Hydraulic Hybrid Vehicles, Hydraulic pump motors, Pump noise