GB2306701A

GB2306701A - Vehicle rear wiper arrangement

Info

Publication number: GB2306701A
Application number: GB9521612A
Authority: GB
Inventors: Stephen John Cook
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1995-10-21
Filing date: 1995-10-21
Publication date: 1997-05-07
Also published as: GB9521612D0

Abstract

The rear screen wiper of a vehicle can be operated in intermittent mode with the delay between each wiping operation varying inversely with the speed of the vehicle, so that as the vehicle speed increases, the wiping rate decreases, i.e. the delay between wiping operations gets longer.

Description

VEHICLE REAR WIPER CONTROL This invention relates to a rear screen wiper control for a motor vehicle.

Many passenger vehicles are equipped with wipers for wiping rain and moisture from a rear screen. Such wipers are typically provided on hatchback and estate car (station wagon) models, but are also fitted to the rear screens of other motor vehicle styles.

In a simple form, such rear screen wipers are controlled by a single ON/OFF switch under the control of the driver.

When the wiper is switched on, it operates continuously and when it is switched off it does not operate at all.

Other systems are known where the rear wiper operates intermittently. The interval between wipes may be fixed or may be adjustable, again under the control of the driver. However all such known systems require input from the driver to vary the rate of wiping.

German patent 4341844 discloses a system, useable for a front screen wiper or a rear screen wiper, or both, in which at least one stroke of the wipers is initiated when a vehicle speed sensor senses a change of speed of the vehicle above a predetermined threshold. Thus the wipers are operated automatically when the driver accelerates sharply or when he brakes sharply, these being the times when optimum visibility is especially desirable.

International patent specification WO 87/00810 discloses an arrangement for varying the speed of a windscreen wiper according to the speed of the vehicle, with the wiper speed increasing as the vehicle speed increases.

According to the present invention there is provided a rear screen wiper control which receives an input representing the vehicle's speed and controls the rear screen wiper so that the rate of wiping decreases as the vehicle speed increases.

In contrast to the situation with the front windscreen, less rain falls on the rear screen as the vehicle speeds up and therefore it is desirable to reduce the frequency of wipe as the vehicle speed increases. This avoids unnecessary wiping and reduces the risk of wiper "judder" which can occur if the wiper wipes a dry screen.

The arrangement may switch the wiper off or increase the wiping interval to an infinite length when the vehicle speed rises above a preset threshold speed. When the vehicle is travelling particularly fast, it may be the case that rain will not fall at all on the rear screen.

The arrangement may be linked into a corresponding arrangement for the front screen, so that when the wipers are switched on to the "intermittent position, the wiping interval increases for the front screen with increasing vehicle speed but decreases for the rear screen with increasing vehicle speed.

The control may include a continuous setting for the rear wiper in addition to an automatically variable setting as set forth above.

The speed sensitive rear wiper could be automatically switched on either with or after an initial predetermined number of cycles once the front wiper has been switched to constant wipe.

Different time threasholds for the speed sensitive rear wiper could be set dependant upon front wiper being set to either intermittant or constant operation.

Intermittent wiper operation may be initiated by a moisture sensor, in a known manner.

The invention will now be further described, by way of example, with reference to the accompanying drawing which shows schematically a vehicle with a wiper control in accordance with the invention fitted to it.

The figure shows a vehicle 10 of an estate car body style with a tailgate 12 and a rear screen 14. The vehicle also has a front screen 16 not visible in the drawing. A rear screen wiper 18 is mounted on an axis 20, and is driven in rotation by a motor contained within a housing 22. In practice the motor and its housing 22 will be concealed behind the tailgate panel 12 and so will not be visible.

A control box 24 will also be mounted in the vehicle. For convenience this box is shown as being mounted in the vehicle engine compartment, but it could be located elsewhere. The control box 24 receives an input proportional to the vehicle speed. The control box may be part of an existing vehicle management system which receives an input representing the vehicle speed, which may be used for controlling other vehicle functions.

The vehicle also has an instrument panel 26 with a steering wheel 28 and a switch stalk 30 for controlling wiper operation.

In operation, the wiper 18 is inactive, and will be stored in a parked position on the screen 14 until the driver initiates rear wiper operation through the switch stalk 30. The stalk may have two positions for controlling rear wiper operation, namely a continuous wipe position and an intermittent wipe position. When the intermittent wipe position is selected, the wiper will pause for an interval between each wiping operation and the length of this interval will be determined in accordance with a signal sent to the housing 22 from the control box 24 along a signal line 32. The length of the intervals between rear wiper operation will vary inversely with the speed of the vehicle. The relationship between speed and wiper operation interval does not have to be linear.

When the vehicle is moving slowly, rain is likely to land on the rear screen at a significant rate. However as the vehicle speeds up, rain is less likely to land because the slipstream resulting from the vehicle motion will divert rain away from the screen. In these circumstances, a slowing down of the wiper as the vehicle speed increases can keep the rate of wiping in register with the rate at which rain falls on the screen.

The switch stalk 30 may control operation of both front and rear screen wipers which may, for example, both be switched off automatically at the same time.

Claims

1. A rear screen wiper control adapted to receive an input representing the vehicle's speed and to control a rear screen wiper so that the rate of wiping decreases as the vehicle speed increases.

2. A control as claimed in Claim 1, adapted to switch the wiper off or to increase the wiping interval to an infinite length when the vehicle speed rises above a preset threshold speed.

3. A control as claimed in Claim 1 or Claim 2, linked into a corresponding arrangement for the front screen, so that when the wipers are switched on to the "intermittent" position, the wiping interval increases for the front screen with increasing vehicle speed but decreases for the rear screen with increasing vehicle speed.

4. A control as claimed in Claim 3, wherein switching on of the front screen wipers also switches on the rear screen wipers.

5. A control as claimed in Claim 4, wherein rear screen wiper operation begins a predetermined interval after the start of operation of the front screen wipers.

6. A control as claimed in any one of Claims 3 to 5, wherein switching the front screen wiper between intermittent and continuous operation results in a change of operating pattern for the rear screen wiper.

7. A rear screen wiper control which includes a continuous setting for the rear wiper in addition to an automatically variable setting as claimed in any preceding claim.