Shared power street sweeper

A power delivery system for a vehicle is disclosed. In one embodiment, the power delivery system includes a chassis engine configured to power driving functions of the vehicle and an auxiliary engine configured to power non-driving hydraulic functions of the vehicle. The power delivery system may also include a power boost system comprising a hydraulic pump and a hydraulic motor in fluid communication with each other. The hydraulic pump may be coupled to a power output of the chassis engine while the hydraulic motor may be coupled to a power output of the auxiliary engine. In one embodiment, the power delivery system has a power sharing mode in which power is transferred from the chassis engine power output to the auxiliary engine power output via the hydraulic pump and motor such that the non-driving hydraulic functions of the vehicle are simultaneously powered by the chassis engine and the auxiliary engine.

BACKGROUND

Street sweeping vehicles are often provided with an auxiliary engine in addition to the main chassis engine. The purpose of an auxiliary engine is to provide a dedicated power source to non-driving functions of the street sweeping vehicle. Examples of non-driving functions are broom operation, blower/fan operation, conveyor operation, and dumping of the hopper. In such arrangements, it is sometimes the case that the chassis engine will also be configured to separately provide power to non-driving functions as well. This allows for the auxiliary engine to be designed at a smaller maximum output capacity since less total load is placed on the auxiliary engine. However, this type of configuration can be disadvantageous in that a failure of the chassis engine system can prevent the operation of some or all of the non-driving functions. Additionally, energy normally lost to heat during braking and deceleration of the vehicle is generally not able to be recaptured in these types of systems. Improvements are desired.

SUMMARY

A power delivery system for a vehicle, such as a street sweeper, is disclosed. In one embodiment, the power delivery system includes a chassis engine configured to power driving functions of the vehicle and an auxiliary engine configured to power non-driving functions of the vehicle. The power delivery system may also include a power boost system comprising a first and second power transmission device in power communication with each other. In one embodiment, the power transmission devices are a hydraulic pump and a hydraulic motor, respectively. The first power transmission device may be coupled to a power output of the chassis engine while the second power transmission device may be coupled to a power output of the auxiliary engine. In one embodiment, the power delivery system has a power sharing mode in which power is transferred from the chassis engine power output to the auxiliary engine power output via the first and second power transmission devices such that the non-driving functions of the vehicle are simultaneously powered by the chassis engine and the auxiliary engine.

A method for simultaneously powering at least one non-driving function of a vehicle with a chassis engine and an auxiliary engine is also disclosed. In one step of the method, a first power transmission device, such as a hydraulic pump, is coupled to a power output of the chassis engine. In another step of the method, a second power transmission device, such as a hydraulic motor, is coupled a power output of the auxiliary engine. The auxiliary engine may be configured to power at least one non-driving function. Another step in the method is placing the first and second power transmission devices in power communication with each other, such as with a hydraulic circuit. Yet another step is transferring power from the chassis engine power output to the auxiliary engine power output via the first and second power transmission devices such that the non-driving functions of the vehicle can be simultaneously powered by the chassis engine and the auxiliary engine. In one embodiment, the driving functions of the vehicle can be simultaneously powered by the chassis engine and the auxiliary engine in a second power sharing mode.

DETAILED DESCRIPTION

Referring toFIG. 1, a power delivery system10and a vehicle20is schematically shown. In one embodiment, the vehicle20is a street sweeping vehicle, such as that shown inFIGS. 10-12. As shown, the street sweeping vehicle20includes a chassis22, wheels24, brooms26, vacuum nozzle28, and a hopper30. The power delivery system10includes a chassis power system100, an auxiliary power system200, and a power boost system300. The chassis power system100is primarily responsible for providing power for the driving functions of the vehicle20. Examples of driving functions that require power are the vehicle drive train, the steering system, and the braking system. The auxiliary power system200is primarily for providing power to auxiliary operations associated with the vehicle20, for example hydraulic functions (not shown) can be driven by a hydraulic pump212. Examples of auxiliary components that require power in a street sweeper application are fans/blowers, scarifying brooms, the hopper, and the conveyor.

In the embodiment shown, the chassis power system100includes an internal combustion engine102and a transmission104coupled to an output shaft (not shown) of the internal combustion engine102. A power take-off (PTO) unit106is also shown as being mounted to the transmission104.FIGS. 5 and 6show an exemplary embodiment of the chassis power system100wherein a first power transmission device302is mounted to and driven by the PTO106which is in turn mounted to and driven by the transmission104.

As shown, the auxiliary power system200includes an internal combustion engine202. Auxiliary power system200is further shown as including a power take-off (PTO) unit206that provides power to a fan208via a belt drive system210. Additionally, auxiliary power system200is shown as having an accessory power take off212driven by the engine202via a gear drive and/or belt drive system214.FIGS. 7-9show an exemplary embodiment of the auxiliary power system200wherein a second power transmission device304(discussed below) is operably connected to the PTO206which is in turn mounted to and driven by the auxiliary engine202. In the embodiment shown inFIGS. 7-9, device304is a hydraulic motor. As most easily seen atFIGS. 8 and 9, an adapter assembly216, having a first adapter part216aand a second adapter part216b, is mounted between the PTO206and the hydraulic motor304. A bracket assembly218, having a horizontal extension218band a vertical extension218aare provided to constrain the torque reaction of the device304, where necessary.

Still referring toFIG. 1, a hydraulic power boost system300is also shown. Power boost system300is for transferring power from the chassis power system100to the auxiliary power system200. During some operations, the chassis engine102may be underutilized while the auxiliary engine202may be at peak capacity. In such instances, the power boost system300can transfer excess power available from the chassis engine102to the auxiliary engine202. This configuration allows for the chassis engine102to simultaneously provide power to the driving functions of the vehicle and to the auxiliary engine202, and for the engines102,202to simultaneously power the non-driving functions of the vehicle20. The power boost system300can also be configured to reclaim and deliver energy from the movement of the vehicle chassis22to the auxiliary power system200as well. For example, the power boost system300can transfer energy developed by braking, deceleration, or engine-braking the vehicle20to the auxiliary power system200.

As shown, the power boost system300includes a first power transmission device302that is driven by a power output150of the chassis engine102. The first power transmission device302is for transmitting power to a second power transmission device304via a power flow path306. The second power transmission device304is for providing power to an output250of the auxiliary engine202. Accordingly, the first and second power transmission devices302,304operate together to transfer power from the output150of the chassis engine102to the output250of the auxiliary engine202. Additionally, the first and second power transmission devices302,304can be configured to transfer power in the opposite direction from the auxiliary engine output205to the chassis engine output150. In one embodiment devices302and304are a hydraulic pump302and motor304, respectively, in fluid communication with each other via a hydraulic circuit306.FIG. 12shows such an embodiment. In one embodiment, the hydraulic pump302is a variable displacement piston pump with pressure compensating controls to maintain a constant system pressure in the hydraulic system. In one embodiment, the hydraulic motor304is a fixed displacement gear motor. In one embodiment, each of the first and second power transmission devices302,304are a hydraulic device configured to operate as both a pump and a motor.

With reference toFIG. 1, the chassis engine output150corresponds to the output of the PTO106. However, the chassis power system100and power boost system300can be configured to drive the first power transmission device302at other locations.FIG. 2shows four alternative engine output sources for driving the first device302: an accessory drive belt150a; a front mounted PTO150b; a rear mounted PTO150c; and a gear drive150dthat can power an air compressor, a fuel injection pump, or a user installed accessory.

With reference toFIG. 1, the auxiliary engine output250corresponds to the auxiliary engine mounted PTO206that drives fan208. However, the auxiliary power system200and power boost system300can be configured to input power from the second power transmission device304at other locations.FIG. 3shows three alternative power input locations for the second device304: a shaft250aof fan208; an additional PTO250boutput of the auxiliary engine202; and a front accessory drive250cof the auxiliary engine202. Additionally, the power input can be at another power path, such as the gear drive that powers an air compressor, a fuel injection pump, or a user installed accessory.

Referring toFIG. 4, an exemplary embodiment of a power boost system300is shown in which the system is based on hydraulic components. As such, the first power transmission device302will be referenced as pump302and the second power transmission device will be referenced as hydraulic motor304. As shown, hydraulic pump302draws hydraulic fluid from a reservoir or tank308. Downstream of the pump302is a spring check valve310. Spring check valve310is for preventing hydraulic fluid from flowing in reverse from the hydraulic motor304towards the hydraulic pump302. However, check valve310is not present where each of the devices302,304are configured to function as either a motor or a pump so that power can be transmitted auxiliary engine to the chassis engine and vice versa.

Between the check valve310and the pump302is a pressure relief valve312which vents back to the tank308. Pressure relief valve312is for protecting the hydraulic system from over pressurization. Downstream of the check valve310is an anti-cavitation check valve314in fluid communication with tank308. The anti-cavitation valve is configured to permit hydraulic fluid to flow to the motor304even if there is a lack of flow from pump302and/or when the motor304is rotating at an excess capacity as compared to the pump302(i.e. when the motor304is winding down). Also downstream of the check valve310is a flow control valve316that can be utilized to regulate flow to the hydraulic motor304from the pump302. In one embodiment, the flow control valve316will limit system flow in the event of a failure.FIG. 4also shows the pump302engaged with the transmission mounted power take-off unit106wherein a PTO106is clutched to engage and disengage with the pump302. Power boost system300can also be provided with a storage device318, such as an accumulator318, for reclaiming braking or energy normally lost to heat, and can provide an additional power source under high load conditions.

As configured inFIG. 4, the power boost system300can operate in a “shared power on” mode and a “shared power off” mode. In the shared power on mode, the clutched PTO106engages to drive the hydraulic pump302. The flow from the pump302will cause the hydraulic motor304to rotate at the speed of the auxiliary engine component to which it is connected.

In one embodiment, a transmission mounted, PTO driven first power transmission device302is utilized in a configuration where the PTO output is dependent upon the travel speed of the vehicle20, as is the case with an Allison 2500 RDS transmission, and similar designs. In such a case, the PTO106is driven at “turbine speed” wherein the turbine rotational speed is nearly equal to the engine crankshaft rotational speed. This is the case except when the transmission104is in gear and the vehicle20is at a full stop. In this configuration, full power is available once the vehicle20exceeds a minimum travel speed, or if the transmission104is in the neutral position. Accordingly, the first device302will be driven by the PTO106whenever the vehicle20is in motion and the transmission is in a non-neutral gear. This configuration additionally allows for energy to be reclaimed during braking, and/or engine-braking events. Also, power to the first device302can be selectively turned off when not required. When first device302is operational, the first device302can be selectively controlled to meet the second device304speed requirements.

In one embodiment, a transmission mounted, PTO driven first power transmission device302is utilized in a configuration where the PTO106is driven by the engine crankshaft, as is the case with an Allison 3500 RDS transmission, and similar designs. In such a configuration, power output from the PTO106is available whenever the engine102is rotating. Accordingly, full power to the first device302is always available regardless of vehicle20speed. If a transmission gear is selected that allows the engine to be back-driven during decelerations, the first device302will be driven whenever the vehicle20is in motion. In such a configuration, energy can be reclaimed through the first device302during braking, and/or engine-braking events. Also, power to the first device302can be selectively turned off when not required. When first device302is operational, the device302can be selectively controlled to meet the second device304speed requirements.

In the shared power off mode, the clutched PTO106disengages with the first power transmission device302such that the device302will not rotate and no power is transmitted (i.e. no hydraulic fluid flow is produced in a hydraulic circuit). In a hydraulic based embodiment, a pump check valve310can be used to ensure that reverse hydraulic flow will not cause the pump302to rotate in the opposite direction. However, when the auxiliary engine202is operating, the second device304can be rotated by the engine202. When this occurs, the motor304operates as a pump and hydraulic fluid is allowed to circulate between the tank308and the motor304via the flow path defined by the anti-cavitation valve314. Alternatively, the hydraulic motor304can utilize a clutch instead of adapter216, such that the motor304can be disengaged from the auxiliary engine output250when not in use. In one embodiment, the clutch is an overrunning clutch. A clutch may also be electrically or otherwise selectively controlled to engage and disengage with the motor304.

In one embodiment, the second power transmission device304provides power to the first power transmission device302in a second power sharing mode such that the auxiliary engine202can provide power to the chassis engine102. This mode of operation is beneficial in applications where the chassis engine may be underpowered due to any number of factors.

Although power boost system300has been described in detail with hydraulic components, other types of power transfer systems may be utilized as well for the first and second power transmission devices302,304shown inFIG. 1. For example, the first and second power transmission devices302,304ofFIG. 1can be electrical generators and motors. Pneumatic based components such as air pumps and air motors could also be utilized for the first and second devices302,304. Also, electrical batteries, electrical capacitors, and/or air tanks may be utilized to store regeneration energy, for example from slowing, braking, or engine-braking the vehicle20.

It is also noted that the power boost system300can be retrofitted onto an existing vehicle20already configured with a chassis engine and an auxiliary engine. In such an application, the power boost system300can be turned off or disconnected without any loss in functionality of the chassis and auxiliary engine systems. In a new system, the auxiliary engine202can be sized smaller than a traditionally sized dual engine system, as the power from the chassis engine augments the auxiliary engine power. For example, instead of installing an auxiliary engine having a rated power output in the range of 99 to 115 horsepower, a smaller 74 horsepower engine could be installed. Since the chassis engine102is generally underutilized during sweeping operations, the chassis engine102will be able to transfer the remaining 25 to 41 horsepower to the auxiliary engine. Accordingly, the maximum output capacity of the auxiliary engine can actually be designed to be less than the maximum input power requirements for the powered non-driving functions of the vehicle20.